ETSI EN 300 132-2 V2.8.1 (2024-10)

Environmental Engineering (EE); Power supply interface at the input of Information and Communication Technology (ICT) equipment; Part 2: -48 V Direct Current (DC)

REN/EE-02109

Okoljski inženiring (EE) - Napajalni vmesnik na vhodu opreme informacijske in komunikacijske tehnologije (IKT) - 2. del: Enosmerna napetost - 48 V (DC)

Ta dokument vsebuje zahteve in merilne metode za fizični vmesnik »A«, ki je med napajalnim sistemom/sistemi ter informacijsko in komunikacijsko tehnološko opremo (IKT), ki porablja električno energijo.
Nazivna napetost pri električnem vmesniku »A« informacijske in komunikacijske tehnološke opreme, določena v tem dokumentu, je enosmerna napetost –48 V.
Enosmerno napajanje lahko poteka prek električnega sistema z enosmernim tokom (npr. temelječega na usmerniku na izmenični tok na mreži ali enosmerni pretvorniki v sončnem sistemu, gorivna celica, motor na izmenični tok ali generator gorivne celice), poleg tega pa je na voljo tudi neposredno napajanje z baterijskim pomožnim sistemom v tem sistemu napajanja z enosmernim tokom. Namen tega dokumenta je uporaba napajalnega sistema z enakimi značilnostmi za vso informacijsko in komunikacijsko tehnološko opremo, ki je določena za področje uporabe zaradi:
– omogočanja medsebojnega delovanja različnih vrst napajalnih enot;
– omogočanja standardizacije informacijske in komunikacijske tehnološke opreme;
– omogočanja nameščanja, delovanja in vzdrževanja informacijske in komunikacijske tehnološke opreme ter sistemov različnega izvora v istem omrežju.
Cilj tega dokumenta je zagotavljanje električne združljivosti med napajalno opremo ter informacijsko in komunikacijsko tehnološko opremo, ki porablja električno energijo, med različnimi sistemskimi bloki in obremenitvami, povezanimi z istim virom napajanja, ki napaja vmesnik »A« (npr. enota za nadzor/spremljanje, hladilni sistem itd.).
Zahteve so določene za:
– napajalni vhod vseh vrst informacijske in komunikacijske tehnološke opreme, nameščene v telekomunikacijskih središčih in povezane z vmesnikom »A«, ki se napaja z enosmerno napetostjo;
– vse vrste informacijske in komunikacijske tehnološke opreme, nameščene v omrežjih za dostop in prostorih strank, pri katerih vmesnik »A« z enosmerno napetostjo prav tako uporablja oprema, ki zahteva napajanje z enosmernim tokom;
– vse vrste informacijske in komunikacijske tehnološke opreme z enosmerno napetostjo, ki se uporablja v stacionarnih in mobilnih omrežjih, nameščene na različnih
lokacijah, kot so stavbe, pokriti prostori, cestne omarice, zunanji objekti.
Motnje v napajalnem vmesniku »A«, povezane s pojavom trajnega vala pod 20 kHz, so zajete v tem dokumentu.
Ta dokument ne opisuje varnostnih zahtev; opisane so v ustreznih varnostnih standardih.
Ta dokument ne opisuje zahtev za elektromagnetno združljivost; opisane so v ustreznih standardih za elektromagnetno združljivost.
OPOMBA: Dodatek B vsebuje usmeritve za napajalne sisteme z enosmerno napetostjo –60 V.

General Information

• Status: Not Published
• Technical Committee: EE 2 - EE Power Supply
• Current Stage: 12 - Citation in the OJ (auto-insert)
• Due Date: 17-Oct-2024
• Completion Date: 08-Oct-2024
• Ref Project: SIST EN 300 132-2 V2.8.1:2024 - Environmental Engineering (EE) - Power supply interface at the input of Information and Communication Technology (ICT) equipment - Part 2: -48 V Direct Current (DC)

Standards Content (Sample)

Draft ETSI EN 300 132-2 V2.8.0 (2024-07)

EUROPEAN STANDARD
Environmental Engineering (EE);
Power supply interface at the input of
Information and Communication Technology (ICT) equipment;
Part 2: -48 V Direct Current (DC)

2 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)

Reference
REN/EE-02109
Keywords
interface, power supply
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ETSI
3 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 10
3.3 Abbreviations . 10
4 Requirements . 10
4.0 Power interface "A" . 10
4.1 Nominal voltage . 11
4.2 Normal service voltage range at interface "A" . 11
4.3 Abnormal service voltage range at interface "A" . 13
4.3.1 Abnormal service voltage range under steady state conditions . 13
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions . 13
4.3.3 Voltage transients . 14
4.3.3.1 Voltage transient due to short-circuit and protective device clearance . 14
4.3.3.2 Short voltage transient due to switching and lightning . 15
4.3.4 Recovery from voltage transients . 16
4.4 Voltage changes due to the regulation of the power supply . 17
4.5 Power supply protection at interface "A" . 17
4.6 Maximum current drain . 17
4.7 Inrush Current on connection of interface "A" . 18
4.7.1 Limits . 18
4.7.2 Measurements . 19
4.8 Conducted immunity requirements of the ICT equipment at interface "A": narrowband noise . 20
4.9 Conducted emissions requirements of the ICT equipment at interface "A" . 22
5 Earthing and bonding . 23
Annex A (informative): Identification of interface "A" . 24
Annex B (informative): -60 VDC systems . 25
Annex C (informative): Guide for measuring inrush current and for transferring the
recorded pulses onto the limit chart . 26
C.1 Measurement . 26
C.2 Pulse waveform transfor mation . 26
C.3 Measurement of inrush current with filter capacitor current pulses . 29
Annex D (informative): Test arrangements for the injection of electrical noise at interface
"A" . 32
Annex E (informative): Wideband noise . 33
E.0 Wideband noise . 33
E.1 Emission of wideband noise . 33
E.1.0 General . 33
E.1.1 Assessment of wideband noise . 33
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4 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
E.2 How to calculate wideband emission . 33
Annex F (informative): Protection dimensioning . 37
Annex G (informative): Effects of protective device operation transients in the power
distribution . 38
Annex H (normative): Verification of measurement network defined in clause 4.9 . 39
Annex I (informative): Bibliography . 40
Annex J (informative): Change history . 41
History . 42

ETSI
5 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Intellectual Property Rights
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pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
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ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
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Foreword
This draft European Standard (EN) has been produced by ETSI Technical Committee Environmental Engineering (EE),
and is now submitted for the combined Public Enquiry and Vote phase of the ETSI EN Approval Procedure.
The present document concerns the requirements for the interface between ICT equipment and its power supply, and
includes requirements relating to its stability and measurement. Various other references and detailed measurement and
test arrangements are contained in informative annexes.
The present document is part 2 of a multi-part deliverable covering Environmental Engineering (EE); Power supply
interface at the input of Information and Communication Technology (ICT) equipment, as identified below:
Part 1: "Alternating Current (AC)";
Part 2: "-48 V Direct Current (DC)";
Part 3: "Up to 400 V Direct Current (DC)".

Proposed national transposition dates
Date of latest announcement of this EN (doa): 3 months after ETSI publication
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 6 months after doa
Date of withdrawal of any conflicting National Standard (dow): 6 months after doa

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6 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
7 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
1 Scope
The present document contains requirements and measurements methods for the physical interface "A" that is situated
between the power supply system(s) and the power consuming ICT equipment.
The nominal voltage at power interface "A" of ICT equipment defined in the present document is DC voltage -48 V.
The DC power can be supplied by a DC output power system (e.g. based on AC rectifiers on grid or DC/DC converters on
solar system, fuel cell, DC engine or fuel cell generator) and also directly supplied by a battery backup in this DC power
system. The purpose of the present document is to be able to use a power supply system with the same characteristics
for all ICT equipment defined in the area of application:
- to facilitate inter working of different types of load units;
- to facilitate the standardization of ICT equipment;
- to facilitate the installation, operation and maintenance in the same network of ICT equipment and systems
from different origins.
The present document aims at providing electrical compatibility between the power supply equipment and the power
consuming ICT equipment, between different system blocks and loads connected to the same power supply feeding the
interface "A" (e.g. control/monitoring, cooling system, etc.).
The requirements are defined for:
- the power supply input of any type of ICT equipment installed at telecommunication centres that are connected
to interface "A" powered by DC;
- any type of ICT equipment, installed in access networks and customers' premises, the DC interface "A" of
which is also used by equipment requiring a DC supply source;
- any type of ICT equipment powered by DC, used in the fixed and mobile networks installed in different
locations such as buildings, shelters, street cabinets, outdoor installations.
Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered
within the present document.
The present document does not cover safety requirements, they are covered by relevant safety standards.
The present document does not cover EMC requirements, they are covered by relevant EMC standards.
NOTE: Annex B gives guidance on -60 VDC supply systems.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 300 253: "Environmental Engineering (EE); Earthing and bonding of ICT equipment
powered by -48 VDC in telecom and data centres".
ETSI
8 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
[2] Void.
[3] Void.
[4] Void.
[5] EN 61000-4-5: "Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement
techniques - Surge immunity test" (produced by CENELEC).
[6] Void.
[7] EN 61000-4-29: "Electromagnetic compatibility (EMC) - Part 4-29: Testing and measurement
techniques -Voltage dips, short interruptions and voltage variations on d.c. input power port
immunity tests" (produced by CENELEC).
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Recommendation ITU-T Q.551: "Transmission characteristics of digital exchanges".
[i.2] Recommendation ITU-T Q.552: "Transmission characteristics at 2-wire analogue interfaces of
digital exchanges".
[i.3] Recommendation ITU-T Q.553: "Transmission characteristics at 4-wire analogue interfaces of
digital exchanges".
[i.4] Recommendation ITU-T Q.554: "Transmission characteristics at digital interfaces of digital
exchanges".
[i.5] ETSI TR 100 283: "Environmental Engineering (EE); Transient voltages at Interface "A" on
telecommunications direct current (dc) power distributions".
[i.6] US Department of Defence MIL-STD-461E: "Requirements for the control of electromagnetic
interference characteristics of subsystems and equipment".
[i.7] Void.
[i.8] Recommendation ITU-T O.41: "Psophometer for use on telephone-type circuits".
[i.9] IEC 60050-601: "International Electrotechnical Vocabulary. Chapter 601: Generation,
transmission and distribution of electricity - General" (Area 826 "Electrical installations",
section 826-11 "Voltages and currents").
[i.10] EN 60269-1: "Low-voltage fuses - Part 1: General requirements" (produced by CENELEC).
[i.11] EN 60934: "Circuit-breakers for equipment (CBE)" (produced by CENELEC).
[i.12] IEC 60050-351: 2013: "International Electrotechnical Vocabulary. Part 351: Control technology".
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9 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
customer premises: location which is the sole responsibility of the customer
DC power return conductor: 0 V power supply conductor
NOTE: Also called "battery return".
fully equipped equipment: configuration that corresponds to the maximum power consumption measured at -48 VDC
with the equipment in operating conditions (e.g. not in standby mode)
NOTE: When there are several fully equipped configurations because of different combinations of possible
boards, the configuration with the boards that gives the highest power consumption should be considered.
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
interface "A": terminals at which the power supply is connected to the system block
NOTE 1: See also figure 1 and annex A.
NOTE 2: This is a functional definition and not an exact depiction of the physical location.
malfunction: termination of the normal service
maximum steady state input current (I ): maximum steady state input current, stated by the manufacturer, for a fully
m
equipped equipment under test connected to interface "A" at nominal voltage
nominal voltage: value of the voltage by which the electrical installation or part of the electrical installation is
designated and identified
NOTE: As defined in IEC 60050-601 [i.9].
normal service: service mode where ICT equipment operates within its specification which includes a defined restart
time after malfunction or full interruption
normal service voltage range: range of steady state voltages over which the equipment will maintain normal service
power supply: power source to which ICT equipment is intended to be connected
service voltage: value of the voltage under normal conditions, at a given instant and a given point of the system
NOTE: As defined in IEC 60050-601 [i.9].
steady-state: state of a system at which all state and output variables remain constant in time while all input variables
are constant
NOTE: This is definition 351-45-10 in IEC 60050-351:2013 [i.12].
system block: functional group of equipment depending for its operation and performance on its connection to the same
power supply
NOTE: A system block may consist of equipment or a functional group of equipment. Different examples of
configurations at interface "A" are given in annex A.
telecommunication centre: location where ICT equipment is installed and which is the sole responsibility of the
operator
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10 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
3.2 Symbols
For the purposes of the present document, the following symbols apply:
I instantaneous inrush current
t
maximum steady state input current
I
m
L inductance of inductive element of LISN
R resistance of resistive element of LISN
t time
U
pso,eff effective psophometric voltage
U
rms RMS voltage
Z capacitive impedance of immunity measurement circuit
c
Z resistive impedance of immunity measurement circuit
m
μs microsecond
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
DC Direct Current
NOTE: Also when used as a suffix to units of measurement.
EMC ElectroMagnetic Compatibility
ESR Equivalent Series Resistance
EUT Equipment Under Test
HOD High-Ohmic Distributions
ICT Information and Communication Technology
IL Insertion Loss
LISN Line Impedance Stabilization Network
LOD Low-Ohmic Distributions
RF Radio Frequency
rms root mean square
TR Technical Report
VDC Voltage Direct Current
NOTE: Also when used as a suffix to units of measurement.
4 Requirements
4.0 Power interface "A"
The power supply interface, interface "A" of figure 1, is a physical point to which all the requirements are related.
This point is situated between the power supply system(s) and the power consuming ICT equipment.
An example of a configuration in which interface "A" is identified is given in annex A.
ETSI
11 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
-V
bat
ICT equipment
+V (0 Volt)
bat
Figure 1: Identification of interface "A"
4.1 Nominal voltage
The nominal voltage at interface "A" shall be -48 VDC with positive conductor connected to earth as defined in ETSI
EN 300 253 [1].
NOTE 1: The positive conductor, also called DC return, can be (see ETSI EN 300 253 [1]):
 Isolated DC return: this is a DC power system in which the DC power return conductor has a single
point connection to the bonding network. Equipment intended for this power distribution has a
floating DC power at the power input terminal.
 Common DC return: this is a DC power system in which the return conductor is connected to the
bonding network at many points. Equipment intended for this power distribution can have the DC
return earthed at the power input terminal.
NOTE 2: In most cases the nominal voltage of interface "A" is based on a 24 cells lead-acid battery. Use of other
technologies, such as Lithium-ion batteries, are increasing and are compatible with the requirements of
the present document
4.2 Normal service voltage range at interface "A"
The normal service voltage range for the -48 VDC nominal supply at interface "A" shall be from -40,5 VDC
to -57,0 VDC.
NOTE 1: The maximum voltage is based on a 0,3 V drop in the distribution loop and a battery voltage of
2,35 V/cell plus 0,5 % for regulation.
There shall be no degradation of service performance when ICT equipment is operating at voltages within the normal
service voltage range including voltage variation inside the normal voltage range.
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 1. The testing and measurement techniques are described in EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply "A" interface inputs.
ETSI
12 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Table 1
Test level of Normal Voltage Basic standard Rise and fall time of Performance criteria
service voltage step step for testing voltage step
variation duration
From -40,5 V to -57,0 VDC 0,1 s EN 61000-4-29 [7] No degradation in the
Between 1 μs and 50 μs on
and back to -40,5 VDC 100 Ω resistive load service performance
(see figure 2a) during and after the
(see basic standard for test
test
From -57,0 V to -40,5 VDC 0,1 s generator)
and back to -57 VDC
(see figure 2b)
-40,5
VDC
-57 VDC
0,1 sec.
1 μsec. to 50 μsec.
Figure 2a
1 μsec. to 50 μsec.
0,1 sec.
-40,5
VDC
-57 VDC
Figure 2b
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 1 on the
powered input.
NOTE 2: The minimum voltage is based on the voltage drop in the distribution network and a battery cell end of
discharge voltage.
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13 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
NOTE 3: The voltages specified are measured at interface "A". It should be noted that if interface "A" is at any
point other than the ICT equipment interface as presented in annex A, there will be a voltage drop
between interface "A" and the equipment terminals.
4.3 Abnormal service voltage range at interface "A"
4.3.1 Abnormal service voltage range under steady state conditions
ICT equipment designed to work at 48 VDC nominal voltage at the interface "A" shall not suffer any damage when
subjected to the following voltage ranges defined in table 2.
Table 2
0,0 V to -40,5 VDC
-57,0 VDC to -60,0 VDC
Following the restoration of the supply to the normal voltage range, the power conversion and management systems on
the load side of interface "A" shall automatically restore normal service. The ICT equipment shall then resume
operation according to its specifications. The abnormal service voltage shall not lead to the disconnection of the power
supply e.g. by causing circuit breakers, fuses or other such devices to operate.
NOTE: It is acceptable that the system may restart when the voltage is -40,5 VDC or anywhere within the
nominal service voltage range and/or after a time delay.
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions
ICT equipment shall comply with the requirements defined in this clause when subject to the abnormal voltage range
defined in table 3 that can be present at the interface "A".
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 3. The testing and measurement techniques are described in EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply inputs.
Table 3
Test level of abnormal Voltage step Basic standard Rise and fall time of Performance criteria
voltage step variation duration for testing voltage step
From -40,5 VDC to -60,0 VDC 0,1 s EN 61000-4-29 [7] Between 1 μs and 50 μs Self restart to a normal
and back to -40,5 VDC service of the equipment
on 100 Ω resistive load
(see figure 3a) without operator
(see basic standard)
From -57,0 VDC to 0,0 V 0,1 s intervention after the test
And back to -57,0 VDC
(see figure 3b)
ETSI
14 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
-40,5
VDC
-60 VDC
0,1 sec.
1 μsec. to 50 μsec.
Figure 3a
1 μsec. to 50 μsec.
0,1 sec.
0 VDC
VDC
-57 VDC
Figure 3b
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on one input (either Input 1 or 2).
In this case the performance criteria shall be "No degradation in the service performance during and after the
test";
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 3 on the
powered input.
4.3.3 Voltage transients
4.3.3.1 Voltage transient due to short-circuit and protective device clearance
Voltage transients may occur at interface "A" when faults (e.g. short circuits) occur in the power distribution system.
These transients are characterized by a voltage drop in the range: 0 V to -40,5 VDC, followed by an overvoltage often
in excess of the maximum steady state abnormal service voltage range defined in table 3 and dependent upon the power
distribution up to interface "A" and the equipment connected to interface "A".
NOTE 1: ETSI TR 100 283 [i.5] provides guidance for the protection of ICT equipment from the transients.
ETSI
15 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
NOTE 2: A protective device operation transient results from a low impedance fault to ground on the equipment
side of a protective device (fuse or circuit breaker) connected to a power distribution bus. In the power
bus, then voltage is reduced (undervoltage) due to high current flowing to ground through the protective
device and the short ground. When the protective device opens, the release energy stored in the
inductance of the bus causes an initial high voltage overshoot of short duration, followed by a longer
interval voltage overshoot that decays toward the steady state bus voltage. The undervoltage portion of
the protective device operation transient, may cause a voltage drop at the input terminals of the other
equipment connected to the common power bus that may affect the functionality of the equipment itself.
The propagation of the protective device operation transient on the power bus depends by the type of
power distribution system and can be minimized by:
 isolating the fault using High-Ohmic Distributions (HODs) or Low-Ohmic Distributions (LODs);
see annex G; or
 using redundant powering systems (i.e. dual feeders (A+B) from two separate power sources
(A+B)). Equipment having two power feeds is fitted with OR-ing devices or separate power supply
units; or
 using large storage capacitance to provide a holdup time equal to or larger than the protective
device operating time.
4.3.3.2 Short voltage transient due to switching and lightning
The surge immunity performance of ICT equipment against abnormal overvoltage shall be verified using the test
procedure described below and the combination wave generator defined in the standard EN 61000-4-5 [5]. This
generator can produce the pulse shape of 1,2 μs-rise time/50 μs-duration in open circuit and 8 μs-rise
time/20 μs-duration in short circuit.
This test shall be performed with the DC return of power supply source connected to ground and with the operating
input voltage of -54 VDC. In a -48 VDC system having a Common DC return, see clause 4.1 of the present document,
only the negative polarity of the voltage transient following the clearance of an overcurrent protection device during a
short-circuit condition is relevant and therefore only negative polarity test defined in table 4 shall apply.
The voltage surge to be applied at the interface "A" of the ICT equipment is defined in table 4.
The test shall apply to equipment with single and multiple power supply inputs.
ETSI
16 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Table 4
Transient Voltage Coupling Number of Voltage Pulse Performance Comments
voltage Pulse lines voltage shape and source criteria
level and polarity pulses impedance
test class
Between 1,2 μs-rise ICT equipment The 0 V reference of
500 V surge positive and operating within the generator shall
Negative 5 time/50 μs-duration
negative the normal be connected to the

power service voltage positive pole of the
2 Ω impedance
supply range shall not power supply
poles be damaged
Self restart to a
normal service of
the equipment
without operator
intervention after
the test
Between: 5 positive 1,2 μs-rise ICT equipment The 0 V reference of
500 V surge positive and and operating within the generator shall
time/50 μs-duration
Positive earth 5 negative the normal be connected to the

and service voltage earth
12 Ω impedance
Negative negative range shall not Test only applicable
and earth be damaged to equipment
intended to be used
Self restart to a in isolated DC return
normal service of power distributions
the equipment (see clause 4.1)
without operator
intervention after
the test
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 4 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 4 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 4 on the
powered input.
4.3.4 Recovery from voltage transients
After the occurrence of a voltage transient, as described in clause 4.3.3, ICT equipment shall continue to function within
its operational specification without requiring manual intervention.
NOTE 1: The abnormal service should not lead to the disconnection of ICT equipment power supply units e.g. by
causing circuit breakers, fuses and other such devices to operate.
NOTE 2: In sensitive equipment, momentary and temporary interruption of the service may occur as a result of
such transients at interface "A". Lengthening of the interruption to service (equipment is not functioning
as intended) due to the recovery of software should be declared in the test report (i.e. details about the
service interruption).
NOTE 3: To prevent system malfunctioning additional arrangements concerning the power supply system may be
necessary.
For example:
 Dual power feeding system.
 High-Ohmic power supply distribution system.
ETSI
17 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
 Independent power supply distribution.
4.4 Voltage changes due to the regulation of the power supply
ICT equipment may be subjected to a voltage change at interface "A" as a result of regulation of the voltage by the
power supply system e.g. end cell switching.
This test shall apply to the ICT equipment connected to interface "A". The test can also be applied separately to each
subpart of the equipment connected to the same interface "A".
This requirement shall be verified applying the test of a voltage variation at the interface "A" with specification and
parameters defined in table 5.
The test shall apply to equipment with single and multiple power supply inputs.
Table 5
Test level of Change rate Performance criteria
Voltage variation
From -40,5 VDC to -57,0 VDC Linear variation slope: No degradation in the equipment functionality
From -57,0 VDC to -40,5 VDC between 3 V/ms and 7 V/ms during and after the test

In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 5 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 5 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 5 on the
powered input.
4.5 Power supply protection at interface "A"
The power supply at interface "A" shall be protected by circuit breakers, fuses or equivalent devices.
NOTE: The energy content of the inrush current has also to be taken into account when specifying the power
supply system up to interface "A".
4.6 Maximum current drain
Protection devices (e.g. circuit breakers, fuses or equivalent devices) shall be defined for a rated current of 1,5 times I
m
to avoid tripping in the normal service voltage range.
This requirement shall be verified by measuring the input current when applying at interface "A" voltage levels and
voltage variations following test specification and parameters defined in table 6.
The test shall apply to equipment with single and multiple power supply inputs.
The maximum steady state current I is the current stated by the manufacturer for a fully-equipped equipment at full
m
load, connected to interface "A" at nominal voltage -48 VDC.
At 40,5 VDC, the current shall not be higher than 1,5 time I .
m
ETSI
18 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Table 6
Test level of Voltage Voltage Performance criteria
applied on power supply variation
input (U)
-48 VDC I value shall be measured and provided
m
From -57 VDC to -40,5 VDC Linear variation The current used by the equipment shall be lower than 1,5 I
m
slope: 1 V/min
From -40,5 VDC to 0 Linear variation The current chart I(U) characteristic used by the equipment
slope: 1 V/min shall be measured and provided

In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed with either Input 1 or 2 powered and no power on the other power input.
NOTE: Additional consideration should be made for temperature variation and technology of the protection
devices (see annex F).
4.7 Inrush Current on connection of interface "A"
4.7.1 Limits
The ratio of the instantaneous inrush current I to maximum steady state current I at interface "A", when the switch is
t m
closed at the nominal voltage (-48 Vdc) and at the minimum (-40,5 Vdc) and highest (-57 Vdc) voltages of the normal
service voltage range, shall not exceed the limits shown in figure 4.
The parameters are defined as follows:
- I : inrush current (magnitude of instantaneous value);
t
- I : maximum steady state input current for a fully-equipped equipment under test connected to interface "A",
m
at nominal voltage.
The power generator for inrush current test shall be in accordance with EN 61000-4-29 [7].
Performance criteria:
• Below 0,1 ms, the inrush current is not defined.
• Below 0,9 ms the I /I ratio shall be lower than 48 as shown in figure 4.
t m
• Above 1 ms: the curve corresponds to the maximum tripping limit of majority of existing protective devices.
ETSI
19 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)

I /I
t m
Inrush Current @ Nominal Voltage
0.1 1.0 10.0 100.0 1,000.0
t [ms]
NOTE 1: Figure 4 is a combined graph for both fuses and (Hydraulic) Magnetic Circuit Breakers. Fuses according to
EN 60269-1 [i.10] (gG type), Magnetic Circuit Breakers according to EN 60934 [i.11]. Annex F reports the
rationale between maximum current and protection selection.
NOTE 2: The time axis refers to "pulse width". Annex C contains suggestions for and an explanation of the inrush
measurement.
NOTE 3: Inrush current measured at maximum load and at the voltages defined in clause 4.7.1.

Figure 4: Maximum inrush current characteristics for ICT equipment
at maximum load and at the voltages defined in clause 4.7.1
4.7.2 Measurements
The circuit for measuring the inrush current drawn by the equipment shall be as shown in figure 5. The test circuit is
designed to operate with a single switch as shown.
NOTE: Small magnitude current pulses for charging RF filter capacitors should not be considered as the starting
point of the inrush measurement. These pulses are not part of the inrush pulse but are before the inrush
current pulse.
Annex C gives guidance on taking these measurements.
ETSI
20 Draft ETSI EN 300 132-2 V2.8.0 (2024-07)
Interface "A"
DC Power Source
-
Telecommunications
ICT
equipment
R L
equipment
+
EUT
LISN
Recording Device
1V
R ≤
I (@54V )
m
10μH ≤ L ≤ 20μH
NOTE 1: Resistance R includes the resistance of inductor L.
NOTE 2: The LISN could be the connecting cable (EUT to power supply), provided that the length has an
inductance of 10 µH to 20 µH and an equivalent resistance.
NOTE 3: The intention of the LISN is to simulate a power network over which a voltage drop not greater than 1 V
will appear in case of nominal current.
NOTE 4: While carrying out the surge current test, the voltage of the DC Power Source at the input of the LISN, as
shown in this figure, shall fall by no more than 2 V due to current limitation or internal impedance of the DC
Power Source.
NOTE 5: R and L in the LISN shall be on one wire or half of them (R/2 and L/2) on each wire.

Figure 5: Inrush current test circuit for DC interfaces
4.8 Conducted immunity requirements of the ICT equipment at
interface "A": narrowband noise
Conducted immunity shall apply only to ICT equipment having an analogue voice interface. Due to the nature of the
interference, only an analogue voice interface could be influenced by disturbing signals in the voice frequency range.
Performance criteria
The ICT equipment shall meet its specification when the level of narrowband noise at interface "A" does not exceed the
limits shown in figure 6.
The values shown refer to the maximum bandwidths as given in table 7.
Table 7
Frequency range Resolution bandwidth
25 Hz to 10 kHz 10 Hz
> 10 kHz to 20 kHz 200 Hz or 300 Hz

ETSI
21 Draft ETSI EN
...

EUROPEAN STANDARD
Environmental Engineering (EE);
Power supply interface at the input of
Information and Communication Technology (ICT) equipment;
Part 2: -48 V Direct Current (DC)

2 ETSI EN 300 132-2 V2.8.1 (2024-10)

Reference
REN/EE-02109
Keywords
interface, power supply
ETSI
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ETSI
3 ETSI EN 300 132-2 V2.8.1 (2024-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 10
3.3 Abbreviations . 10
4 Requirements . 10
4.0 Power interface "A" . 10
4.1 Nominal voltage . 11
4.2 Normal service voltage range at interface "A" . 11
4.3 Abnormal service voltage range at interface "A" . 13
4.3.1 Abnormal service voltage range under steady state conditions . 13
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions . 13
4.3.3 Voltage transients . 14
4.3.3.1 Voltage transient due to short-circuit and protective device clearance . 14
4.3.3.2 Short voltage transient due to switching and lightning . 15
4.3.4 Recovery from voltage transients . 16
4.4 Voltage changes due to the regulation of the power supply . 17
4.5 Power supply protection at interface "A" . 17
4.6 Maximum current drain . 17
4.7 Inrush Current on connection of interface "A" . 18
4.7.1 Limits . 18
4.7.2 Measurements . 19
4.8 Conducted immunity requirements of the ICT equipment at interface "A": narrowband noise . 20
4.9 Conducted emissions requirements of the ICT equipment at interface "A" . 22
5 Earthing and bonding . 23
Annex A (informative): Identification of interface "A" . 24
Annex B (informative): -60 VDC systems . 25
Annex C (informative): Guide for measuring inrush current and for transferring the
recorded pulses onto the limit chart . 26
C.1 Measurement . 26
C.2 Pulse waveform transfor mation . 26
C.3 Measurement of inrush current with filter capacitor current pulses . 29
Annex D (informative): Test arrangements for the injection of electrical noise at interface
"A" . 32
Annex E (informative): Wideband noise . 33
E.0 Wideband noise . 33
E.1 Emission of wideband noise . 33
E.1.0 General . 33
E.1.1 Assessment of wideband noise . 33
ETSI
4 ETSI EN 300 132-2 V2.8.1 (2024-10)
E.2 How to calculate wideband emission . 33
Annex F (informative): Protection dimensioning . 37
Annex G (informative): Effects of protective device operation transients in the power
distribution . 38
Annex H (normative): Verification of measurement network defined in clause 4.9 . 39
Annex I (informative): Bibliography . 40
Annex J (informative): Change history . 41
History . 42

ETSI
5 ETSI EN 300 132-2 V2.8.1 (2024-10)
Intellectual Property Rights
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pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
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Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Environmental Engineering (EE).
The present document concerns the requirements for the interface between ICT equipment and its power supply, and
includes requirements relating to its stability and measurement. Various other references and detailed measurement and
test arrangements are contained in informative annexes.
The present document is part 2 of a multi-part deliverable covering Environmental Engineering (EE); Power supply
interface at the input of Information and Communication Technology (ICT) equipment, as identified below:
Part 1: "Alternating Current (AC)";
Part 2: "-48 V Direct Current (DC)";
Part 3: "Up to 400 V Direct Current (DC)".

National transposition dates
Date of adoption of this EN: 3 October 2024
Date of latest announcement of this EN (doa): 31 January 2025
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 July 2025
Date of withdrawal of any conflicting National Standard (dow): 31 July 2025

ETSI
6 ETSI EN 300 132-2 V2.8.1 (2024-10)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
7 ETSI EN 300 132-2 V2.8.1 (2024-10)
1 Scope
The present document contains requirements and measurements methods for the physical interface "A" that is situated
between the power supply system(s) and the power consuming ICT equipment.
The nominal voltage at power interface "A" of ICT equipment defined in the present document is DC voltage -48 V.
The DC power can be supplied by a DC output power system (e.g. based on AC rectifiers on grid or DC/DC converters on
solar system, fuel cell, DC engine or fuel cell generator) and also directly supplied by a battery backup in this DC power
system. The purpose of the present document is to be able to use a power supply system with the same characteristics
for all ICT equipment defined in the area of application:
- to facilitate inter working of different types of load units;
- to facilitate the standardization of ICT equipment;
- to facilitate the installation, operation and maintenance in the same network of ICT equipment and systems
from different origins.
The present document aims at providing electrical compatibility between the power supply equipment and the power
consuming ICT equipment, between different system blocks and loads connected to the same power supply feeding the
interface "A" (e.g. control/monitoring, cooling system, etc.).
The requirements are defined for:
- the power supply input of any type of ICT equipment installed at telecommunication centres that are connected
to interface "A" powered by DC;
- any type of ICT equipment, installed in access networks and customers' premises, the DC interface "A" of
which is also used by equipment requiring a DC supply source;
- any type of ICT equipment powered by DC, used in the fixed and mobile networks installed in different
locations such as buildings, shelters, street cabinets, outdoor installations.
Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered
within the present document.
The present document does not cover safety requirements, they are covered by relevant safety standards.
The present document does not cover EMC requirements, they are covered by relevant EMC standards.
NOTE: Annex B gives guidance on -60 VDC supply systems.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 300 253: "Environmental Engineering (EE); Earthing and bonding of ICT equipment
powered by -48 VDC in telecom and data centres".
ETSI
8 ETSI EN 300 132-2 V2.8.1 (2024-10)
[2] Void.
[3] Void.
[4] Void.
[5] EN 61000-4-5: "Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement
techniques - Surge immunity test" (produced by CENELEC).
[6] Void.
[7] EN 61000-4-29: "Electromagnetic compatibility (EMC) - Part 4-29: Testing and measurement
techniques -Voltage dips, short interruptions and voltage variations on d.c. input power port
immunity tests" (produced by CENELEC).
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Recommendation ITU-T Q.551: "Transmission characteristics of digital exchanges".
[i.2] Recommendation ITU-T Q.552: "Transmission characteristics at 2-wire analogue interfaces of
digital exchanges".
[i.3] Recommendation ITU-T Q.553: "Transmission characteristics at 4-wire analogue interfaces of
digital exchanges".
[i.4] Recommendation ITU-T Q.554: "Transmission characteristics at digital interfaces of digital
exchanges".
[i.5] ETSI TR 100 283: "Environmental Engineering (EE); Transient voltages at Interface "A" on
telecommunications direct current (dc) power distributions".
[i.6] US Department of Defence MIL-STD-461E: "Requirements for the control of electromagnetic
interference characteristics of subsystems and equipment".
[i.7] Void.
[i.8] Recommendation ITU-T O.41: "Psophometer for use on telephone-type circuits".
[i.9] IEC 60050-601: "International Electrotechnical Vocabulary. Chapter 601: Generation,
transmission and distribution of electricity - General" (Area 826 "Electrical installations",
section 826-11 "Voltages and currents").
[i.10] EN 60269-1: "Low-voltage fuses - Part 1: General requirements" (produced by CENELEC).
[i.11] EN 60934: "Circuit-breakers for equipment (CBE)" (produced by CENELEC).
[i.12] IEC 60050-351: 2013: "International Electrotechnical Vocabulary. Part 351: Control technology".
ETSI
9 ETSI EN 300 132-2 V2.8.1 (2024-10)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
customer premises: location which is the sole responsibility of the customer
DC power return conductor: 0 V power supply conductor
NOTE: Also called "battery return".
fully equipped equipment: configuration that corresponds to the maximum power consumption measured at -48 VDC
with the equipment in operating conditions (e.g. not in standby mode)
NOTE: When there are several fully equipped configurations because of different combinations of possible
boards, the configuration with the boards that gives the highest power consumption should be considered.
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
interface "A": terminals at which the power supply is connected to the system block
NOTE 1: See also figure 1 and annex A.
NOTE 2: This is a functional definition and not an exact depiction of the physical location.
malfunction: termination of the normal service
maximum steady state input current (I ): maximum steady state input current, stated by the manufacturer, for a fully
m
equipped equipment under test connected to interface "A" at nominal voltage
nominal voltage: value of the voltage by which the electrical installation or part of the electrical installation is
designated and identified
NOTE: As defined in IEC 60050-601 [i.9].
normal service: service mode where ICT equipment operates within its specification which includes a defined restart
time after malfunction or full interruption
normal service voltage range: range of steady state voltages over which the equipment will maintain normal service
power supply: power source to which ICT equipment is intended to be connected
service voltage: value of the voltage under normal conditions, at a given instant and a given point of the system
NOTE: As defined in IEC 60050-601 [i.9].
steady-state: state of a system at which all state and output variables remain constant in time while all input variables
are constant
NOTE: This is definition 351-45-10 in IEC 60050-351:2013 [i.12].
system block: functional group of equipment depending for its operation and performance on its connection to the same
power supply
NOTE: A system block may consist of equipment or a functional group of equipment. Different examples of
configurations at interface "A" are given in annex A.
telecommunication centre: location where ICT equipment is installed and which is the sole responsibility of the
operator
ETSI
10 ETSI EN 300 132-2 V2.8.1 (2024-10)
3.2 Symbols
For the purposes of the present document, the following symbols apply:
I instantaneous inrush current
t
maximum steady state input current
I
m
L inductance of inductive element of LISN
R resistance of resistive element of LISN
t time
U
pso,eff effective psophometric voltage
U
rms RMS voltage
Z capacitive impedance of immunity measurement circuit
c
Z resistive impedance of immunity measurement circuit
m
μs microsecond
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
DC Direct Current
NOTE: Also when used as a suffix to units of measurement.
EMC ElectroMagnetic Compatibility
ESR Equivalent Series Resistance
EUT Equipment Under Test
HOD High-Ohmic Distributions
ICT Information and Communication Technology
IL Insertion Loss
LISN Line Impedance Stabilization Network
LOD Low-Ohmic Distributions
RF Radio Frequency
rms root mean square
TR Technical Report
VDC Voltage Direct Current
NOTE: Also when used as a suffix to units of measurement.
4 Requirements
4.0 Power interface "A"
The power supply interface, interface "A" of figure 1, is a physical point to which all the requirements are related.
This point is situated between the power supply system(s) and the power consuming ICT equipment.
An example of a configuration in which interface "A" is identified is given in annex A.
ETSI
11 ETSI EN 300 132-2 V2.8.1 (2024-10)
-V
bat
ICT equipment
+V (0 Volt)
bat
Figure 1: Identification of interface "A"
4.1 Nominal voltage
The nominal voltage at interface "A" shall be -48 VDC with positive conductor connected to earth as defined in ETSI
EN 300 253 [1].
NOTE 1: The positive conductor, also called DC return, can be (see ETSI EN 300 253 [1]):
 Isolated DC return: this is a DC power system in which the DC power return conductor has a single
point connection to the bonding network. Equipment intended for this power distribution has a
floating DC power at the power input terminal.
 Common DC return: this is a DC power system in which the return conductor is connected to the
bonding network at many points. Equipment intended for this power distribution can have the DC
return earthed at the power input terminal.
NOTE 2: In most cases the nominal voltage of interface "A" is based on a 24 cells lead-acid battery. Use of other
technologies, such as Lithium-ion batteries, are increasing and are compatible with the requirements of
the present document
4.2 Normal service voltage range at interface "A"
The normal service voltage range for the -48 VDC nominal supply at interface "A" shall be from -40,5 VDC
to -57,0 VDC.
NOTE 1: The maximum voltage is based on a 0,3 V drop in the distribution loop and a battery voltage of
2,35 V/cell plus 0,5 % for regulation.
There shall be no degradation of service performance when ICT equipment is operating at voltages within the normal
service voltage range including voltage variation inside the normal voltage range.
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 1. The testing and measurement techniques are described in EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply "A" interface inputs.
ETSI
12 ETSI EN 300 132-2 V2.8.1 (2024-10)
Table 1
Test level of Normal Voltage Basic standard Rise and fall time of Performance criteria
service voltage step step for testing voltage step
variation duration
From -40,5 V to -57,0 VDC 0,1 s EN 61000-4-29 [7] No degradation in the
Between 1 μs and 50 μs on
and back to -40,5 VDC 100 Ω resistive load service performance
(see figure 2a) during and after the
(see basic standard for test
test
From -57,0 V to -40,5 VDC 0,1 s generator)
and back to -57 VDC
(see figure 2b)
-40,5
VDC
-57 VDC
0,1 sec.
1 μsec. to 50 μsec.
Figure 2a
1 μsec. to 50 μsec.
0,1 sec.
-40,5
VDC
-57 VDC
Figure 2b
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 1 on the
powered input.
NOTE 2: The minimum voltage is based on the voltage drop in the distribution network and a battery cell end of
discharge voltage.
ETSI
13 ETSI EN 300 132-2 V2.8.1 (2024-10)
NOTE 3: The voltages specified are measured at interface "A". It should be noted that if interface "A" is at any
point other than the ICT equipment interface as presented in annex A, there will be a voltage drop
between interface "A" and the equipment terminals.
4.3 Abnormal service voltage range at interface "A"
4.3.1 Abnormal service voltage range under steady state conditions
ICT equipment designed to work at 48 VDC nominal voltage at the interface "A" shall not suffer any damage when
subjected to the following voltage ranges defined in table 2.
Table 2
0,0 V to -40,5 VDC
-57,0 VDC to -60,0 VDC
Following the restoration of the supply to the normal voltage range, the power conversion and management systems on
the load side of interface "A" shall automatically restore normal service. The ICT equipment shall then resume
operation according to its specifications. The abnormal service voltage shall not lead to the disconnection of the power
supply e.g. by causing circuit breakers, fuses or other such devices to operate.
NOTE: It is acceptable that the system may restart when the voltage is -40,5 VDC or anywhere within the
nominal service voltage range and/or after a time delay.
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions
ICT equipment shall comply with the requirements defined in this clause when subject to the abnormal voltage range
defined in table 3 that can be present at the interface "A".
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 3. The testing and measurement techniques are described in EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply inputs.
Table 3
Test level of abnormal Voltage step Basic standard Rise and fall time of Performance criteria
voltage step variation duration for testing voltage step
From -40,5 VDC to -60,0 VDC 0,1 s EN 61000-4-29 [7] Between 1 μs and 50 μs Self restart to a normal
and back to -40,5 VDC service of the equipment
on 100 Ω resistive load
(see figure 3a) without operator
(see basic standard)
From -57,0 VDC to 0,0 V 0,1 s intervention after the test
And back to -57,0 VDC
(see figure 3b)
ETSI
14 ETSI EN 300 132-2 V2.8.1 (2024-10)
-40,5
VDC
-60 VDC
0,1 sec.
1 μsec. to 50 μsec.
Figure 3a
1 μsec. to 50 μsec.
0,1 sec.
0 VDC
VDC
-57 VDC
Figure 3b
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on one input (either Input 1 or 2).
In this case the performance criteria shall be "No degradation in the service performance during and after the
test";
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 3 on the
powered input.
4.3.3 Voltage transients
4.3.3.1 Voltage transient due to short-circuit and protective device clearance
Voltage transients may occur at interface "A" when faults (e.g. short circuits) occur in the power distribution system.
These transients are characterized by a voltage drop in the range: 0 V to -40,5 VDC, followed by an overvoltage often
in excess of the maximum steady state abnormal service voltage range defined in table 3 and dependent upon the power
distribution up to interface "A" and the equipment connected to interface "A".
NOTE 1: ETSI TR 100 283 [i.5] provides guidance for the protection of ICT equipment from the transients.
ETSI
15 ETSI EN 300 132-2 V2.8.1 (2024-10)
NOTE 2: A protective device operation transient results from a low impedance fault to ground on the equipment
side of a protective device (fuse or circuit breaker) connected to a power distribution bus. In the power
bus, then voltage is reduced (undervoltage) due to high current flowing to ground through the protective
device and the short ground. When the protective device opens, the release energy stored in the
inductance of the bus causes an initial high voltage overshoot of short duration, followed by a longer
interval voltage overshoot that decays toward the steady state bus voltage. The undervoltage portion of
the protective device operation transient, may cause a voltage drop at the input terminals of the other
equipment connected to the common power bus that may affect the functionality of the equipment itself.
The propagation of the protective device operation transient on the power bus depends by the type of
power distribution system and can be minimized by:
 isolating the fault using High-Ohmic Distributions (HODs) or Low-Ohmic Distributions (LODs);
see annex G; or
 using redundant powering systems (i.e. dual feeders (A+B) from two separate power sources
(A+B)). Equipment having two power feeds is fitted with OR-ing devices or separate power supply
units; or
 using large storage capacitance to provide a holdup time equal to or larger than the protective
device operating time.
4.3.3.2 Short voltage transient due to switching and lightning
The surge immunity performance of ICT equipment against abnormal overvoltage shall be verified using the test
procedure described below and the combination wave generator defined in the standard EN 61000-4-5 [5]. This
generator can produce the pulse shape of 1,2 μs-rise time/50 μs-duration in open circuit and 8 μs-rise
time/20 μs-duration in short circuit.
This test shall be performed with the DC return of power supply source connected to ground and with the operating
input voltage of -54 VDC. In a -48 VDC system having a Common DC return, see clause 4.1 of the present document,
only the negative polarity of the voltage transient following the clearance of an overcurrent protection device during a
short-circuit condition is relevant and therefore only negative polarity test defined in table 4 shall apply.
The voltage surge to be applied at the interface "A" of the ICT equipment is defined in table 4.
The test shall apply to equipment with single and multiple power supply inputs.
ETSI
16 ETSI EN 300 132-2 V2.8.1 (2024-10)
Table 4
Transient Voltage Coupling Number of Voltage Pulse Performance Comments
voltage Pulse lines voltage shape and source criteria
level and polarity pulses impedance
test class
Between 1,2 μs-rise ICT equipment The 0 V reference of
500 V surge positive and operating within the generator shall
Negative 5 time/50 μs-duration
negative the normal be connected to the

power service voltage positive pole of the
2 Ω impedance
supply range shall not power supply
poles be damaged
Self restart to a
normal service of
the equipment
without operator
intervention after
the test
Between: 5 positive 1,2 μs-rise ICT equipment The 0 V reference of
500 V surge positive and and operating within the generator shall
time/50 μs-duration
Positive earth 5 negative the normal be connected to the

and service voltage earth
12 Ω impedance
Negative negative range shall not Test only applicable
and earth be damaged to equipment
intended to be used
Self restart to a in isolated DC return
normal service of power distributions
the equipment (see clause 4.1)
without operator
intervention after
the test
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 4 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 4 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 4 on the
powered input.
4.3.4 Recovery from voltage transients
After the occurrence of a voltage transient, as described in clause 4.3.3, ICT equipment shall continue to function within
its operational specification without requiring manual intervention.
NOTE 1: The abnormal service should not lead to the disconnection of ICT equipment power supply units e.g. by
causing circuit breakers, fuses and other such devices to operate.
NOTE 2: In sensitive equipment, momentary and temporary interruption of the service may occur as a result of
such transients at interface "A". Lengthening of the interruption to service (equipment is not functioning
as intended) due to the recovery of software should be declared in the test report (i.e. details about the
service interruption).
NOTE 3: To prevent system malfunctioning additional arrangements concerning the power supply system may be
necessary.
For example:
 Dual power feeding system.
 High-Ohmic power supply distribution system.
ETSI
17 ETSI EN 300 132-2 V2.8.1 (2024-10)
 Independent power supply distribution.
4.4 Voltage changes due to the regulation of the power supply
ICT equipment may be subjected to a voltage change at interface "A" as a result of regulation of the voltage by the
power supply system e.g. end cell switching.
This test shall apply to the ICT equipment connected to interface "A". The test can also be applied separately to each
subpart of the equipment connected to the same interface "A".
This requirement shall be verified applying the test of a voltage variation at the interface "A" with specification and
parameters defined in table 5.
The test shall apply to equipment with single and multiple power supply inputs.
Table 5
Test level of Change rate Performance criteria
Voltage variation
From -40,5 VDC to -57,0 VDC Linear variation slope: No degradation in the equipment functionality
From -57,0 VDC to -40,5 VDC between 3 V/ms and 7 V/ms during and after the test

In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 5 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 5 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 5 on the
powered input.
4.5 Power supply protection at interface "A"
The power supply at interface "A" shall be protected by circuit breakers, fuses or equivalent devices.
NOTE: The energy content of the inrush current has also to be taken into account when specifying the power
supply system up to interface "A".
4.6 Maximum current drain
Protection devices (e.g. circuit breakers, fuses or equivalent devices) shall be defined for a rated current of 1,5 times I
m
to avoid tripping in the normal service voltage range.
This requirement shall be verified by measuring the input current when applying at interface "A" voltage levels and
voltage variations following test specification and parameters defined in table 6.
The test shall apply to equipment with single and multiple power supply inputs.
The maximum steady state current I is the current stated by the manufacturer for a fully-equipped equipment at full
m
load, connected to interface "A" at nominal voltage -48 VDC.
At 40,5 VDC, the current shall not be higher than 1,5 time I .
m
ETSI
18 ETSI EN 300 132-2 V2.8.1 (2024-10)
Table 6
Test level of Voltage Voltage Performance criteria
applied on power supply variation
input (U)
-48 VDC I value shall be measured and provided
m
From -57 VDC to -40,5 VDC Linear variation The current used by the equipment shall be lower than 1,5 I
m
slope: 1 V/min
From -40,5 VDC to 0 Linear variation The current chart I(U) characteristic used by the equipment
slope: 1 V/min shall be measured and provided

In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed with either Input 1 or 2 powered and no power on the other power input.
NOTE: Additional consideration should be made for temperature variation and technology of the protection
devices (see annex F).
4.7 Inrush Current on connection of interface "A"
4.7.1 Limits
The ratio of the instantaneous inrush current I to maximum steady state current I at interface "A", when the switch is
t m
closed at the nominal voltage (-48 Vdc) and at the minimum (-40,5 Vdc) and highest (-57 Vdc) voltages of the normal
service voltage range, shall not exceed the limits shown in figure 4.
The parameters are defined as follows:
- I : inrush current (magnitude of instantaneous value);
t
- I : maximum steady state input current for a fully-equipped equipment under test connected to interface "A",
m
at nominal voltage.
The power generator for inrush current test shall be in accordance with EN 61000-4-29 [7].
Performance criteria:
• Below 0,1 ms, the inrush current is not defined.
• Below 0,9 ms the I /I ratio shall be lower than 48 as shown in figure 4.
t m
• Above 1 ms: the curve corresponds to the maximum tripping limit of majority of existing protective devices.
ETSI
19 ETSI EN 300 132-2 V2.8.1 (2024-10)

I /I
t m
Inrush Current @ Nominal Voltage
0.1 1.0 10.0 100.0 1,000.0
t [ms]
NOTE 1: Figure 4 is a combined graph for both fuses and (Hydraulic) Magnetic Circuit Breakers. Fuses according to
EN 60269-1 [i.10] (gG type), Magnetic Circuit Breakers according to EN 60934 [i.11]. Annex F reports the
rationale between maximum current and protection selection.
NOTE 2: The time axis refers to "pulse width". Annex C contains suggestions for and an explanation of the inrush
measurement.
NOTE 3: Inrush current measured at maximum load and at the voltages defined in clause 4.7.1.

Figure 4: Maximum inrush current characteristics for ICT equipment
at maximum load and at the voltages defined in clause 4.7.1
4.7.2 Measurements
The circuit for measuring the inrush current drawn by the equipment shall be as shown in figure 5. The test circuit is
designed to operate with a single switch as shown.
NOTE: Small magnitude current pulses for charging RF filter capacitors should not be considered as the starting
point of the inrush measurement. These pulses are not part of the inrush pulse but are before the inrush
current pulse.
Annex C gives guidance on taking these measurements.
ETSI
20 ETSI EN 300 132-2 V2.8.1 (2024-10)
Interface "A"
DC Power Source
-
Telecommunications
ICT
equipment
R L
equipment
+
EUT
LISN
Recording Device
1V
R ≤
I (@54V )
m
10μH ≤ L ≤ 20μH
NOTE 1: Resistance R includes the resistance of inductor L.
NOTE 2: The LISN could be the connecting cable (EUT to power supply), provided that the length has an
inductance of 10 µH to 20 µH and an equivalent resistance.
NOTE 3: The intention of the LISN is to simulate a power network over which a voltage drop not greater than 1 V
will appear in case of nominal current.
NOTE 4: While carrying out the surge current test, the voltage of the DC Power Source at the input of the LISN, as
shown in this figure, shall fall by no more than 2 V due to current limitation or internal impedance of the DC
Power Source.
NOTE 5: R and L in the LISN shall be on one wire or half of them (R/2 and L/2) on each wire.

Figure 5: Inrush current test circuit for DC interfaces
4.8 Conducted immunity requirements of the ICT equipment at
interface "A": narrowband noise
Conducted immunity shall apply only to ICT equipment having an analogue voice interface. Due to the nature of the
interference, only an analogue voice interface could be influenced by disturbing signals in the voice frequency range.
Performance criteria
The ICT equipment shall meet its specification when the level of narrowband noise at interface "A" does not exceed the
limits shown in figure 6.
The values shown refer to the maximum bandwidths as given in table 7.
Table 7
Frequency range Resolution bandwidth
25 Hz to 10 kHz 10 Hz
> 10 kHz to 20 kHz 200 Hz or 300 Hz

ETSI
21 ETSI EN 300 132-2 V2.8.1 (2024-10)
dBm (1 mW in 50 Ω)
mV
-10
70,7
-13
-20 22,4
-30 7,07
-40
2,24
10 25 10 000 20 000
100 1 000 f (Hz)
Figure 6: Immunity level of narrow-band noise at interface "A"
The recommended method of measurement is with a spectrum analyser having the bandwidths shown in table 7 for the
relevant frequency ranges. The measuring circuit is shown in figure
...

SLOVENSKI STANDARD
01-december-2024
Okoljski inženiring (EE) - Napajalni vmesnik na vhodu opreme informacijske in
komunikacijske tehnologije (IKT) - 2. del: Enosmerna napetost - 48 V (DC)
Environmental Engineering (EE) - Power supply interface at the input of Information and
Communication Technology (ICT) equipment - Part 2: -48 V Direct Current (DC)
Ta slovenski standard je istoveten z: ETSI EN 300 132-2 V2.8.1 (2024-10)
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
33.050.01 Telekomunikacijska Telecommunication terminal
terminalska oprema na equipment in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
Environmental Engineering (EE);
Power supply interface at the input of
Information and Communication Technology (ICT) equipment;
Part 2: -48 V Direct Current (DC)

2 ETSI EN 300 132-2 V2.8.1 (2024-10)

Reference
REN/EE-02109
Keywords
interface, power supply
ETSI
650 Route des Lucioles
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Siret N° 348 623 562 00017 - APE 7112B
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ETSI
3 ETSI EN 300 132-2 V2.8.1 (2024-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definition of terms, symbols and abbreviations . 9
3.1 Terms . 9
3.2 Symbols . 10
3.3 Abbreviations . 10
4 Requirements . 10
4.0 Power interface "A" . 10
4.1 Nominal voltage . 11
4.2 Normal service voltage range at interface "A" . 11
4.3 Abnormal service voltage range at interface "A" . 13
4.3.1 Abnormal service voltage range under steady state conditions . 13
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions . 13
4.3.3 Voltage transients . 14
4.3.3.1 Voltage transient due to short-circuit and protective device clearance . 14
4.3.3.2 Short voltage transient due to switching and lightning . 15
4.3.4 Recovery from voltage transients . 16
4.4 Voltage changes due to the regulation of the power supply . 17
4.5 Power supply protection at interface "A" . 17
4.6 Maximum current drain . 17
4.7 Inrush Current on connection of interface "A" . 18
4.7.1 Limits . 18
4.7.2 Measurements . 19
4.8 Conducted immunity requirements of the ICT equipment at interface "A": narrowband noise . 20
4.9 Conducted emissions requirements of the ICT equipment at interface "A" . 22
5 Earthing and bonding . 23
Annex A (informative): Identification of interface "A" . 24
Annex B (informative): -60 VDC systems . 25
Annex C (informative): Guide for measuring inrush current and for transferring the
recorded pulses onto the limit chart . 26
C.1 Measurement . 26
C.2 Pulse waveform transfor mation . 26
C.3 Measurement of inrush current with filter capacitor current pulses . 29
Annex D (informative): Test arrangements for the injection of electrical noise at interface
"A" . 32
Annex E (informative): Wideband noise . 33
E.0 Wideband noise . 33
E.1 Emission of wideband noise . 33
E.1.0 General . 33
E.1.1 Assessment of wideband noise . 33
ETSI
4 ETSI EN 300 132-2 V2.8.1 (2024-10)
E.2 How to calculate wideband emission . 33
Annex F (informative): Protection dimensioning . 37
Annex G (informative): Effects of protective device operation transients in the power
distribution . 38
Annex H (normative): Verification of measurement network defined in clause 4.9 . 39
Annex I (informative): Bibliography . 40
Annex J (informative): Change history . 41
History . 42

ETSI
5 ETSI EN 300 132-2 V2.8.1 (2024-10)
Intellectual Property Rights
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Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Environmental Engineering (EE).
The present document concerns the requirements for the interface between ICT equipment and its power supply, and
includes requirements relating to its stability and measurement. Various other references and detailed measurement and
test arrangements are contained in informative annexes.
The present document is part 2 of a multi-part deliverable covering Environmental Engineering (EE); Power supply
interface at the input of Information and Communication Technology (ICT) equipment, as identified below:
Part 1: "Alternating Current (AC)";
Part 2: "-48 V Direct Current (DC)";
Part 3: "Up to 400 V Direct Current (DC)".

National transposition dates
Date of adoption of this EN: 3 October 2024
Date of latest announcement of this EN (doa): 31 January 2025
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 July 2025
Date of withdrawal of any conflicting National Standard (dow): 31 July 2025

ETSI
6 ETSI EN 300 132-2 V2.8.1 (2024-10)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
7 ETSI EN 300 132-2 V2.8.1 (2024-10)
1 Scope
The present document contains requirements and measurements methods for the physical interface "A" that is situated
between the power supply system(s) and the power consuming ICT equipment.
The nominal voltage at power interface "A" of ICT equipment defined in the present document is DC voltage -48 V.
The DC power can be supplied by a DC output power system (e.g. based on AC rectifiers on grid or DC/DC converters on
solar system, fuel cell, DC engine or fuel cell generator) and also directly supplied by a battery backup in this DC power
system. The purpose of the present document is to be able to use a power supply system with the same characteristics
for all ICT equipment defined in the area of application:
- to facilitate inter working of different types of load units;
- to facilitate the standardization of ICT equipment;
- to facilitate the installation, operation and maintenance in the same network of ICT equipment and systems
from different origins.
The present document aims at providing electrical compatibility between the power supply equipment and the power
consuming ICT equipment, between different system blocks and loads connected to the same power supply feeding the
interface "A" (e.g. control/monitoring, cooling system, etc.).
The requirements are defined for:
- the power supply input of any type of ICT equipment installed at telecommunication centres that are connected
to interface "A" powered by DC;
- any type of ICT equipment, installed in access networks and customers' premises, the DC interface "A" of
which is also used by equipment requiring a DC supply source;
- any type of ICT equipment powered by DC, used in the fixed and mobile networks installed in different
locations such as buildings, shelters, street cabinets, outdoor installations.
Disturbances on the power supply interface "A" relating to the continuous wave phenomena below 20 kHz are covered
within the present document.
The present document does not cover safety requirements, they are covered by relevant safety standards.
The present document does not cover EMC requirements, they are covered by relevant EMC standards.
NOTE: Annex B gives guidance on -60 VDC supply systems.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 300 253: "Environmental Engineering (EE); Earthing and bonding of ICT equipment
powered by -48 VDC in telecom and data centres".
ETSI
8 ETSI EN 300 132-2 V2.8.1 (2024-10)
[2] Void.
[3] Void.
[4] Void.
[5] EN 61000-4-5: "Electromagnetic compatibility (EMC) - Part 4-5: Testing and measurement
techniques - Surge immunity test" (produced by CENELEC).
[6] Void.
[7] EN 61000-4-29: "Electromagnetic compatibility (EMC) - Part 4-29: Testing and measurement
techniques -Voltage dips, short interruptions and voltage variations on d.c. input power port
immunity tests" (produced by CENELEC).
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Recommendation ITU-T Q.551: "Transmission characteristics of digital exchanges".
[i.2] Recommendation ITU-T Q.552: "Transmission characteristics at 2-wire analogue interfaces of
digital exchanges".
[i.3] Recommendation ITU-T Q.553: "Transmission characteristics at 4-wire analogue interfaces of
digital exchanges".
[i.4] Recommendation ITU-T Q.554: "Transmission characteristics at digital interfaces of digital
exchanges".
[i.5] ETSI TR 100 283: "Environmental Engineering (EE); Transient voltages at Interface "A" on
telecommunications direct current (dc) power distributions".
[i.6] US Department of Defence MIL-STD-461E: "Requirements for the control of electromagnetic
interference characteristics of subsystems and equipment".
[i.7] Void.
[i.8] Recommendation ITU-T O.41: "Psophometer for use on telephone-type circuits".
[i.9] IEC 60050-601: "International Electrotechnical Vocabulary. Chapter 601: Generation,
transmission and distribution of electricity - General" (Area 826 "Electrical installations",
section 826-11 "Voltages and currents").
[i.10] EN 60269-1: "Low-voltage fuses - Part 1: General requirements" (produced by CENELEC).
[i.11] EN 60934: "Circuit-breakers for equipment (CBE)" (produced by CENELEC).
[i.12] IEC 60050-351: 2013: "International Electrotechnical Vocabulary. Part 351: Control technology".
ETSI
9 ETSI EN 300 132-2 V2.8.1 (2024-10)
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
customer premises: location which is the sole responsibility of the customer
DC power return conductor: 0 V power supply conductor
NOTE: Also called "battery return".
fully equipped equipment: configuration that corresponds to the maximum power consumption measured at -48 VDC
with the equipment in operating conditions (e.g. not in standby mode)
NOTE: When there are several fully equipped configurations because of different combinations of possible
boards, the configuration with the boards that gives the highest power consumption should be considered.
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
interface "A": terminals at which the power supply is connected to the system block
NOTE 1: See also figure 1 and annex A.
NOTE 2: This is a functional definition and not an exact depiction of the physical location.
malfunction: termination of the normal service
maximum steady state input current (I ): maximum steady state input current, stated by the manufacturer, for a fully
m
equipped equipment under test connected to interface "A" at nominal voltage
nominal voltage: value of the voltage by which the electrical installation or part of the electrical installation is
designated and identified
NOTE: As defined in IEC 60050-601 [i.9].
normal service: service mode where ICT equipment operates within its specification which includes a defined restart
time after malfunction or full interruption
normal service voltage range: range of steady state voltages over which the equipment will maintain normal service
power supply: power source to which ICT equipment is intended to be connected
service voltage: value of the voltage under normal conditions, at a given instant and a given point of the system
NOTE: As defined in IEC 60050-601 [i.9].
steady-state: state of a system at which all state and output variables remain constant in time while all input variables
are constant
NOTE: This is definition 351-45-10 in IEC 60050-351:2013 [i.12].
system block: functional group of equipment depending for its operation and performance on its connection to the same
power supply
NOTE: A system block may consist of equipment or a functional group of equipment. Different examples of
configurations at interface "A" are given in annex A.
telecommunication centre: location where ICT equipment is installed and which is the sole responsibility of the
operator
ETSI
10 ETSI EN 300 132-2 V2.8.1 (2024-10)
3.2 Symbols
For the purposes of the present document, the following symbols apply:
I instantaneous inrush current
t
maximum steady state input current
I
m
L inductance of inductive element of LISN
R resistance of resistive element of LISN
t time
U
pso,eff effective psophometric voltage
U
rms RMS voltage
Z capacitive impedance of immunity measurement circuit
c
Z resistive impedance of immunity measurement circuit
m
μs microsecond
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
DC Direct Current
NOTE: Also when used as a suffix to units of measurement.
EMC ElectroMagnetic Compatibility
ESR Equivalent Series Resistance
EUT Equipment Under Test
HOD High-Ohmic Distributions
ICT Information and Communication Technology
IL Insertion Loss
LISN Line Impedance Stabilization Network
LOD Low-Ohmic Distributions
RF Radio Frequency
rms root mean square
TR Technical Report
VDC Voltage Direct Current
NOTE: Also when used as a suffix to units of measurement.
4 Requirements
4.0 Power interface "A"
The power supply interface, interface "A" of figure 1, is a physical point to which all the requirements are related.
This point is situated between the power supply system(s) and the power consuming ICT equipment.
An example of a configuration in which interface "A" is identified is given in annex A.
ETSI
11 ETSI EN 300 132-2 V2.8.1 (2024-10)
-V
bat
ICT equipment
+V (0 Volt)
bat
Figure 1: Identification of interface "A"
4.1 Nominal voltage
The nominal voltage at interface "A" shall be -48 VDC with positive conductor connected to earth as defined in ETSI
EN 300 253 [1].
NOTE 1: The positive conductor, also called DC return, can be (see ETSI EN 300 253 [1]):
 Isolated DC return: this is a DC power system in which the DC power return conductor has a single
point connection to the bonding network. Equipment intended for this power distribution has a
floating DC power at the power input terminal.
 Common DC return: this is a DC power system in which the return conductor is connected to the
bonding network at many points. Equipment intended for this power distribution can have the DC
return earthed at the power input terminal.
NOTE 2: In most cases the nominal voltage of interface "A" is based on a 24 cells lead-acid battery. Use of other
technologies, such as Lithium-ion batteries, are increasing and are compatible with the requirements of
the present document
4.2 Normal service voltage range at interface "A"
The normal service voltage range for the -48 VDC nominal supply at interface "A" shall be from -40,5 VDC
to -57,0 VDC.
NOTE 1: The maximum voltage is based on a 0,3 V drop in the distribution loop and a battery voltage of
2,35 V/cell plus 0,5 % for regulation.
There shall be no degradation of service performance when ICT equipment is operating at voltages within the normal
service voltage range including voltage variation inside the normal voltage range.
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 1. The testing and measurement techniques are described in EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply "A" interface inputs.
ETSI
12 ETSI EN 300 132-2 V2.8.1 (2024-10)
Table 1
Test level of Normal Voltage Basic standard Rise and fall time of Performance criteria
service voltage step step for testing voltage step
variation duration
From -40,5 V to -57,0 VDC 0,1 s EN 61000-4-29 [7] No degradation in the
Between 1 μs and 50 μs on
and back to -40,5 VDC 100 Ω resistive load service performance
(see figure 2a) during and after the
(see basic standard for test
test
From -57,0 V to -40,5 VDC 0,1 s generator)
and back to -57 VDC
(see figure 2b)
-40,5
VDC
-57 VDC
0,1 sec.
1 μsec. to 50 μsec.
Figure 2a
1 μsec. to 50 μsec.
0,1 sec.
-40,5
VDC
-57 VDC
Figure 2b
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 1 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 1 on the
powered input.
NOTE 2: The minimum voltage is based on the voltage drop in the distribution network and a battery cell end of
discharge voltage.
ETSI
13 ETSI EN 300 132-2 V2.8.1 (2024-10)
NOTE 3: The voltages specified are measured at interface "A". It should be noted that if interface "A" is at any
point other than the ICT equipment interface as presented in annex A, there will be a voltage drop
between interface "A" and the equipment terminals.
4.3 Abnormal service voltage range at interface "A"
4.3.1 Abnormal service voltage range under steady state conditions
ICT equipment designed to work at 48 VDC nominal voltage at the interface "A" shall not suffer any damage when
subjected to the following voltage ranges defined in table 2.
Table 2
0,0 V to -40,5 VDC
-57,0 VDC to -60,0 VDC
Following the restoration of the supply to the normal voltage range, the power conversion and management systems on
the load side of interface "A" shall automatically restore normal service. The ICT equipment shall then resume
operation according to its specifications. The abnormal service voltage shall not lead to the disconnection of the power
supply e.g. by causing circuit breakers, fuses or other such devices to operate.
NOTE: It is acceptable that the system may restart when the voltage is -40,5 VDC or anywhere within the
nominal service voltage range and/or after a time delay.
4.3.2 Abnormal conditions: voltage variations, dips and short interruptions
ICT equipment shall comply with the requirements defined in this clause when subject to the abnormal voltage range
defined in table 3 that can be present at the interface "A".
This requirement shall be verified by applying at interface "A" a voltage step test with specification and parameters
defined in table 3. The testing and measurement techniques are described in EN 61000-4-29 [7].
The test shall apply to equipment with single and multiple power supply inputs.
Table 3
Test level of abnormal Voltage step Basic standard Rise and fall time of Performance criteria
voltage step variation duration for testing voltage step
From -40,5 VDC to -60,0 VDC 0,1 s EN 61000-4-29 [7] Between 1 μs and 50 μs Self restart to a normal
and back to -40,5 VDC service of the equipment
on 100 Ω resistive load
(see figure 3a) without operator
(see basic standard)
From -57,0 VDC to 0,0 V 0,1 s intervention after the test
And back to -57,0 VDC
(see figure 3b)
ETSI
14 ETSI EN 300 132-2 V2.8.1 (2024-10)
-40,5
VDC
-60 VDC
0,1 sec.
1 μsec. to 50 μsec.
Figure 3a
1 μsec. to 50 μsec.
0,1 sec.
0 VDC
VDC
-57 VDC
Figure 3b
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 3 on one input (either Input 1 or 2).
In this case the performance criteria shall be "No degradation in the service performance during and after the
test";
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 3 on the
powered input.
4.3.3 Voltage transients
4.3.3.1 Voltage transient due to short-circuit and protective device clearance
Voltage transients may occur at interface "A" when faults (e.g. short circuits) occur in the power distribution system.
These transients are characterized by a voltage drop in the range: 0 V to -40,5 VDC, followed by an overvoltage often
in excess of the maximum steady state abnormal service voltage range defined in table 3 and dependent upon the power
distribution up to interface "A" and the equipment connected to interface "A".
NOTE 1: ETSI TR 100 283 [i.5] provides guidance for the protection of ICT equipment from the transients.
ETSI
15 ETSI EN 300 132-2 V2.8.1 (2024-10)
NOTE 2: A protective device operation transient results from a low impedance fault to ground on the equipment
side of a protective device (fuse or circuit breaker) connected to a power distribution bus. In the power
bus, then voltage is reduced (undervoltage) due to high current flowing to ground through the protective
device and the short ground. When the protective device opens, the release energy stored in the
inductance of the bus causes an initial high voltage overshoot of short duration, followed by a longer
interval voltage overshoot that decays toward the steady state bus voltage. The undervoltage portion of
the protective device operation transient, may cause a voltage drop at the input terminals of the other
equipment connected to the common power bus that may affect the functionality of the equipment itself.
The propagation of the protective device operation transient on the power bus depends by the type of
power distribution system and can be minimized by:
 isolating the fault using High-Ohmic Distributions (HODs) or Low-Ohmic Distributions (LODs);
see annex G; or
 using redundant powering systems (i.e. dual feeders (A+B) from two separate power sources
(A+B)). Equipment having two power feeds is fitted with OR-ing devices or separate power supply
units; or
 using large storage capacitance to provide a holdup time equal to or larger than the protective
device operating time.
4.3.3.2 Short voltage transient due to switching and lightning
The surge immunity performance of ICT equipment against abnormal overvoltage shall be verified using the test
procedure described below and the combination wave generator defined in the standard EN 61000-4-5 [5]. This
generator can produce the pulse shape of 1,2 μs-rise time/50 μs-duration in open circuit and 8 μs-rise
time/20 μs-duration in short circuit.
This test shall be performed with the DC return of power supply source connected to ground and with the operating
input voltage of -54 VDC. In a -48 VDC system having a Common DC return, see clause 4.1 of the present document,
only the negative polarity of the voltage transient following the clearance of an overcurrent protection device during a
short-circuit condition is relevant and therefore only negative polarity test defined in table 4 shall apply.
The voltage surge to be applied at the interface "A" of the ICT equipment is defined in table 4.
The test shall apply to equipment with single and multiple power supply inputs.
ETSI
16 ETSI EN 300 132-2 V2.8.1 (2024-10)
Table 4
Transient Voltage Coupling Number of Voltage Pulse Performance Comments
voltage Pulse lines voltage shape and source criteria
level and polarity pulses impedance
test class
Between 1,2 μs-rise ICT equipment The 0 V reference of
500 V surge positive and operating within the generator shall
Negative 5 time/50 μs-duration
negative the normal be connected to the

power service voltage positive pole of the
2 Ω impedance
supply range shall not power supply
poles be damaged
Self restart to a
normal service of
the equipment
without operator
intervention after
the test
Between: 5 positive 1,2 μs-rise ICT equipment The 0 V reference of
500 V surge positive and and operating within the generator shall
time/50 μs-duration
Positive earth 5 negative the normal be connected to the

and service voltage earth
12 Ω impedance
Negative negative range shall not Test only applicable
and earth be damaged to equipment
intended to be used
Self restart to a in isolated DC return
normal service of power distributions
the equipment (see clause 4.1)
without operator
intervention after
the test
In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 4 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 4 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 4 on the
powered input.
4.3.4 Recovery from voltage transients
After the occurrence of a voltage transient, as described in clause 4.3.3, ICT equipment shall continue to function within
its operational specification without requiring manual intervention.
NOTE 1: The abnormal service should not lead to the disconnection of ICT equipment power supply units e.g. by
causing circuit breakers, fuses and other such devices to operate.
NOTE 2: In sensitive equipment, momentary and temporary interruption of the service may occur as a result of
such transients at interface "A". Lengthening of the interruption to service (equipment is not functioning
as intended) due to the recovery of software should be declared in the test report (i.e. details about the
service interruption).
NOTE 3: To prevent system malfunctioning additional arrangements concerning the power supply system may be
necessary.
For example:
 Dual power feeding system.
 High-Ohmic power supply distribution system.
ETSI
17 ETSI EN 300 132-2 V2.8.1 (2024-10)
 Independent power supply distribution.
4.4 Voltage changes due to the regulation of the power supply
ICT equipment may be subjected to a voltage change at interface "A" as a result of regulation of the voltage by the
power supply system e.g. end cell switching.
This test shall apply to the ICT equipment connected to interface "A". The test can also be applied separately to each
subpart of the equipment connected to the same interface "A".
This requirement shall be verified applying the test of a voltage variation at the interface "A" with specification and
parameters defined in table 5.
The test shall apply to equipment with single and multiple power supply inputs.
Table 5
Test level of Change rate Performance criteria
Voltage variation
From -40,5 VDC to -57,0 VDC Linear variation slope: No degradation in the equipment functionality
From -57,0 VDC to -40,5 VDC between 3 V/ms and 7 V/ms during and after the test

In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed:
• with Inputs 1 and 2 powered simultaneously and applying the test in table 5 on both inputs simultaneously;
• with Inputs 1 and 2 powered simultaneously and applying the test in table 5 on one input (either Input 1 or 2);
• with either Input 1 or 2 powered and no power on the other power input and applying the test in table 5 on the
powered input.
4.5 Power supply protection at interface "A"
The power supply at interface "A" shall be protected by circuit breakers, fuses or equivalent devices.
NOTE: The energy content of the inrush current has also to be taken into account when specifying the power
supply system up to interface "A".
4.6 Maximum current drain
Protection devices (e.g. circuit breakers, fuses or equivalent devices) shall be defined for a rated current of 1,5 times I
m
to avoid tripping in the normal service voltage range.
This requirement shall be verified by measuring the input current when applying at interface "A" voltage levels and
voltage variations following test specification and parameters defined in table 6.
The test shall apply to equipment with single and multiple power supply inputs.
The maximum steady state current I is the current stated by the manufacturer for a fully-equipped equipment at full
m
load, connected to interface "A" at nominal voltage -48 VDC.
At 40,5 VDC, the current shall not be higher than 1,5 time I .
m
ETSI
18 ETSI EN 300 132-2 V2.8.1 (2024-10)
Table 6
Test level of Voltage Voltage Performance criteria
applied on power supply variation
input (U)
-48 VDC I value shall be measured and provided
m
From -57 VDC to -40,5 VDC Linear variation The current used by the equipment shall be lower than 1,5 I
m
slope: 1 V/min
From -40,5 VDC to 0 Linear variation The current chart I(U) characteristic used by the equipment
slope: 1 V/min shall be measured and provided

In the case of ICT equipment with power supply input redundancy (e.g. Input 1 and Input 2), this test shall be
performed with either Input 1 or 2 powered and no power on the other power input.
NOTE: Additional consideration should be made for temperature variation and technology of the protection
devices (see annex F).
4.7 Inrush Current on connection of interface "A"
4.7.1 Limits
The ratio of the instantaneous inrush current I to maximum steady state current I at interface "A", when the switch is
t m
closed at the nominal voltage (-48 Vdc) and at the minimum (-40,5 Vdc) and highest (-57 Vdc) voltages of the normal
service voltage range, shall not exceed the limits shown in figure 4.
The parameters are defined as follows:
- I : inrush current (magnitude of instantaneous value);
t
- I : maximum steady state input current for a fully-equipped equipment under test connected to interface "A",
m
at nominal voltage.
The power generator for inrush current test shall be in accordance with EN 61000-4-29 [7].
Performance criteria:
• Below 0,1 ms, the inrush current is not defined.
• Below 0,9 ms the I /I ratio shall be lower than 48 as shown in figure 4.
t m
• Above 1 ms: the curve corresponds to the maximum tripping limit of majority of existing protective devices.
ETSI
19 ETSI EN 300 132-2 V2.8.1 (2024-10)

I /I
t m
Inrush Current @ Nominal Voltage
0.1 1.0 10.0 100.0 1,000.0
t [ms]
NOTE 1: Figure 4 is a combined graph for both fuses and (Hydraulic) Magnetic Circuit Breakers. Fuses according to
EN 60269-1 [i.10] (gG type), Magnetic Circuit Breakers according to EN 60934 [i.11]. Annex F reports the
rationale between maximum current and protection selection.
NOTE 2: The time axis refers to "pulse width". Annex C contains suggestions for and an explanation of the inrush
measurement.
NOTE 3: Inrush current measured at maximum load and at the voltages defined in clause 4.7.1.

Figure 4: Maximum inrush current characteristics for ICT equipment
at maximum load and at the voltages defined in clause 4.7.1
4.7.2 Measurements
The circuit for measuring the inrush current drawn by the equipment shall be as shown in figure 5. The test circuit is
designed to operate with a single switch as shown.
NOTE: Small magnitude current pulses for charging RF filter capacitors should not be considered as the starting
point of the inrush measurement. These pulses are not part of the inrush pulse but are before the inrush
current pulse.
Annex C gives guidance on taking these measurements.
ETSI
20 ETSI EN 300 132-2 V2.8.1 (2024-10)
Interface "A"
DC Power Source
-
Telecommunications
ICT
equipment
R L
equipment
+
EUT
LISN
Recording Device
1V
R ≤
I (@54V )
m
10μH ≤ L ≤ 20μH
NOTE 1: Resistance R includes the resistance of inductor L.
NOTE 2: The LISN could be the connecting cable (EUT to power supply), provided that the length has an
inductance of 10 µH to 20 µH and an equivalent resistance.
NOTE 3: The intention of the LISN is to simulate a power network over which a voltage drop not greater than 1 V
will appear in case of nominal
...