SIST EN 50122-3:2010
(Main)Railway applications - Fixed installations - Electrical safety, earthing and bonding - Part 3: Mutual interaction of a.c. and d.c. traction systems
Railway applications - Fixed installations - Electrical safety, earthing and bonding - Part 3: Mutual interaction of a.c. and d.c. traction systems
This European Standard specifies requirements for the protective provisions relating to electrical safety in fixed installations, when it is reasonably likely that hazardous voltages or currents will arise for people or equipment, as a result of the mutual interaction of a.c. and d.c. electric traction systems. It also applies to all aspects of fixed installations that are necessary to ensure electrical safety during maintenance work within electric traction systems. The mutual interaction can be of any of the following kinds: - parallel running of a.c. and d.c. electric traction systems; - crossing of a.c. and d.c. electric traction systems; - shared use of tracks, buildings or other structures; - system separation sections between a.c. and d.c. electric traction systems. Scope is limited to basic frequency voltages and currents and their superposition. This European Standard does not cover radiated interferences. This European Standard applies to all new lines, extensions and to all major revisions to existing lines for the following electric traction systems: a) railways; b) guided mass transport systems such as: 1) tramways, 2) elevated and underground railways, 3) mountain railways, 4) trolleybus systems, and 5) magnetically levitated systems, which use a contact line system; c) material transportation systems. The standard does not apply to: d) mine traction systems in underground mines; e) cranes, transportable platforms and similar transportation equipment on rails, temporary structures (e.g. exhibition structures) in so far as these are not supplied directly or via transformers from the contact line system and are not endangered by the traction power supply system for railways; f) suspended cable cars; g) funicular railways; h) procedures or rules for maintenance.
Bahnanwendungen - Ortsfeste Anlagen - Elektrische Sicherheit, Erdung und Rückstromführung - Teil 3: Gegenseitige Beeinflussung von Wechsel- und Gleichstrombahnsystemen
Applications ferroviaires - Installations fixes - Sécurité électrique, dispositions pour les courants de retour et mise à la terre -- Partie 3: Interactions entre systèmes de traction en courant alternatif et en courant continu
Železniške naprave - Stabilne naprave električne vleke - 3. del: Medsebojno vplivanje med izmeničnimi in enosmernimi sistemi vleke
Ta evropski standard določa zahteve za zaščitne ukrepe v zvezi z električno varnostjo v stabilnih napravah električne vleke, kadar obstaja razumna možnost nastanka napetosti ali tokov, nevarnih za ljudi ali opremo, kot posledica medsebojnega vplivanja med izmeničnimi in enosmernimi električnimi sistemi vleke. Velja tudi za vse vidike stabilnih naprav, potrebne za zagotavljanje električne varnosti med vzdrževalnim delom v električnih sistemih vleke. Vrste medsebojnega vplivanja so lahko naslednje: - vzporedno tekoči enosmerni in izmenični električni sistemi vleke; - križanje enosmernih in izmeničnih električnih sistemov vleke; - souporaba tirnic, stavb ali drugih konstrukcij; - deli za ločevanje sistemov med enosmernimi in izmeničnimi električnimi sistemi vleke. Področje uporabe je omejeno na napetosti in tokove osnovne frekvence in njihovo superpozicijo. Ta evropski standard ne zajema izsevanih interferenc. Ta evropski standard velja za vse nove vode, razširitve in za vse večje prenove obstoječih vodov za naslednje električne sisteme vleke: a) železniške proge, b) vodene masovne prevozne sisteme, kot so: 1) tramvajske proge, 2) nadzemne in podzemne železnice, 3) gorske železnice, 4) trolejbusni sistemi, in 5) sistemi z magnetnim lebdenjem, ki uporabljajo sistem voznih vodov, c) sisteme za prevoz materiala. Ta standard ne velja za: d) rudniške vlečne sisteme v podzemnih rudnikih, e) žerjave, prenosne platforme in podobno opremo za prevoz po tirih, začasne strukture (npr. razstavne strukture), če ne prihajajo neposredno ali preko transformatorjev s sistema voznih vodov in jih ne ogroža napajanje sistema vleke za železnice, f) viseče kabinske žičnice, g) vzpenjače; h) postopke ali pravila za vzdrževanje.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN 50122-3:2010
01-december-2010
äHOH]QLãNHQDSUDYH6WDELOQHQDSUDYHHOHNWULþQHYOHNHGHO 0HGVHERMQR
YSOLYDQMHPHGL]PHQLþQLPLLQHQRVPHUQLPLVLVWHPLYOHNH
Railway applications - Fixed installations - Electrical safety, earthing and bonding - Part
3: Mutual interaction of a.c. and d.c. traction systems
Bahnanwendungen - Ortsfeste Anlagen - Elektrische Sicherheit, Erdung und
Rückstromführung - Teil 3: Gegenseitige Beeinflussung von Wechsel- und
Gleichstrombahnsystemen
Applications ferroviaires - Installations fixes - Sécurité électrique, dispositions pour les
courants de retour et mise à la terre -- Partie 3: Interactions entre systèmes de traction
en courant alternatif et en courant continu
Ta slovenski standard je istoveten z: EN 50122-3:2010
ICS:
29.280 (OHNWULþQDYOHþQDRSUHPD Electric traction equipment
SIST EN 50122-3:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN 50122-3:2010
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SIST EN 50122-3:2010
EUROPEAN STANDARD
EN 50122-3
NORME EUROPÉENNE
October 2010
EUROPÄISCHE NORM
ICS 29.120.50; 29.280
English version
Railway applications -
Fixed installations -
Electrical safety, earthing and the return circuit -
Part 3: Mutual Interaction of a.c. and d.c. traction systems
Applications ferroviaires - Bahnanwendungen -
Installations fixes - Ortsfeste Anlagen -
Sécurité électrique, mise à la terre et Elektrische Sicherheit, Erdung und
circuit de retour - Rückleitung -
Partie 3: Interactions mutuelles entre Teil 3: Gegenseitige Beeinflussung von
systèmes de traction en courant alternatif Wechselstrom- und
et en courant continu Gleichstrombahnsystemen
This European Standard was approved by CENELEC on 2010-10-01. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Management Centre: Avenue Marnix 17, B - 1000 Brussels
© 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50122-3:2010 E
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SIST EN 50122-3:2010
EN 50122-3:2010 – 2 –
Foreword
This European Standard was prepared by SC 9XC, Electric supply and earthing systems for public transport
equipment and ancillary apparatus (Fixed installations), of Technical Committee CENELEC TC 9X, Electrical
and electronic applications for railways. It was submitted to the formal vote and was approved by CENELEC
as EN 50122-3 on 2010-10-01.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2011-10-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2013-10-01
This draft European Standard has been prepared under a mandate given to CENELEC by the European
Commission and the European Free Trade Association and covers essential requirements of EC Directives
96/48/EC (HSR), 2001/16/EC (CONRAIL) and 2008/57/EC (RAIL). See Annex ZZ.
______________
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Contents
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Hazards and adverse effects . 6
4.1 General . 6
4.2 Electrical safety of persons . 6
5 Types of mutual interaction to be considered . 6
5.1 General . 6
5.2 Galvanic coupling . 7
5.3 Non-galvanic coupling . 7
6 Zone of mutual interaction . 8
6.1 General . 8
6.2 A.C. . 8
6.3 D.C. . 8
7 Touch voltage limits for the combination of alternating and direct voltages . 9
7.1 General . 9
7.2 Touch voltage limits for long-term conditions . 9
7.3 A.C. system short-term conditions and d.c. system long-term conditions . 10
7.4 A.C. system long-term conditions and d.c. system short-term conditions . 11
7.5 A.C. system short-term conditions and d.c. system short-term conditions . 12
7.6 Workshops and similar locations . 12
8 Technical requirements and measures inside the zone of mutual interaction . 13
8.1 General . 13
8.2 Requirements if the a.c. railway and the d.c. railway have separate return circuits. 13
8.3 Requirements if the a.c. railway and the d.c. railway have common return circuits and use
the same tracks . 15
8.4 System separation sections and system separation stations . 16
Annex A (informative) Zone of mutual interaction . 17
A.1 Introduction . 17
A.2 A.C. system as source . 17
A.3 D.C. system as source . 21
Annex B (informative) Analysis of combined voltages . 22
Annex C (informative) Analysis and assessment of mutual interaction . 27
C.1 General . 27
C.2 Analysis of mutual interaction . 27
C.3 System configurations to be taken into consideration . 27
Annex ZZ (informative) Coverage of Essential Requirements of EC Directives . 28
Bibliography . 29
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SIST EN 50122-3:2010
EN 50122-3:2010 – 4 –
Figures
Figure 1 ― Maximum permissible combined effective touch voltages (excluding workshops and similar
locations) for long-term conditions . 10
Figure 2 ― Maximum permissible combined effective touch voltages under a.c. short-term conditions
and d.c. long-term conditions . 11
Figure 3 ― Maximum permissible combined effective touch voltages under a.c. long-term conditions
and d.c. short-term conditions. 12
Figure 4 ― Maximum permissible combined effective touch voltages in workshops and similar locations
excluding short-term conditions . 13
Figure 5 ― Example of where a VLD shall be suitable for both alternating and direct voltage . 14
Figure A.1 ― Overview of voltages coupled in as function of distance and soil resistivity I . 18
Figure A.2 ― Overview of voltages coupled in as function of distance and soil resistivity II . 19
Figure A.3 ― Relation between length of parallelism and zone of mutual interaction caused by an a.c.
railway . 20
Figure B.1 ― Definition of combined peak voltage . 23
Figure B.2 ― Overview of permissible combined a.c. and d.c. voltages . 24
Figure B.3 ― Overview of permissible voltages in case of a duration ≥ 1,0 s both a.c. voltage and d.c.
voltage . 25
Figure B.4 ― Permissible voltages in case of a duration 0,1 s a.c. voltage and a duration 300 s d.c.
voltage . 26
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1 Scope
This European Standard specifies requirements for the protective provisions relating to electrical safety in
fixed installations, when it is reasonably likely that hazardous voltages or currents will arise for people or
equipment, as a result of the mutual interaction of a.c. and d.c. electric traction systems.
It also applies to all aspects of fixed installations that are necessary to ensure electrical safety during
maintenance work within electric traction systems.
The mutual interaction can be of any of the following kinds:
– parallel running of a.c. and d.c. electric traction systems;
– crossing of a.c. and d.c. electric traction systems;
– shared use of tracks, buildings or other structures;
– system separation sections between a.c. and d.c. electric traction systems.
Scope is limited to basic frequency voltages and currents and their superposition. This European Standard
does not cover radiated interferences.
This European Standard applies to all new lines, extensions and to all major revisions to existing lines for the
following electric traction systems:
a) railways;
b) guided mass transport systems such as:
1) tramways,
2) elevated and underground railways,
3) mountain railways,
4) trolleybus systems, and
5) magnetically levitated systems, which use a contact line system;
c) material transportation systems.
The standard does not apply to:
d) mine traction systems in underground mines;
e) cranes, transportable platforms and similar transportation equipment on rails, temporary structures (e.g.
exhibition structures) in so far as these are not supplied directly or via transformers from the contact line
system and are not endangered by the traction power supply system for railways;
f) suspended cable cars;
g) funicular railways;
h) procedures or rules for maintenance.
NOTE The rules given in this European Standard can also be applied to mutual interaction with non-electrified tracks, if hazardous
voltages or currents can arise from a.c. or d.c. electric traction systems.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 50122-1:2010, Railway applications – Fixed installations – Electrical safety, earthing and the return
circuit – Part 1: Protective provisions against electric shock
EN 50122-2:2010, Railway applications – Fixed installations – Electrical safety, earthing and the return
circuit – Part 2: Provisions against the effects of stray currents caused by d.c. traction systems
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SIST EN 50122-3:2010
EN 50122-3:2010 – 6 –
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 50122-1:2010 apply.
4 Hazards and adverse effects
4.1 General
The different requirements specified in EN 50122-1 and EN 50122-2, concerning connections to the return
circuit of the a.c. railway, and connections to the return circuit of the d.c. railway, shall be harmonized in
order to avoid risks of hazardous voltages and stray currents.
Such hazards and risks shall be considered from the start of the planning of any installation which includes
both a.c. and d.c. railways. Suitable measures shall be specified for limiting the voltages to the levels given in
this European Standard, while limiting the damaging effects of stray currents in accordance with EN 50122-2.
NOTE Additional adverse effects are possible, for example:
– thermal overload of conductors, screens and sheaths;
– thermal overload of transformers due to magnetic saturation of the cores;
– restriction of operation because of possible effects on the safety and correct functioning of signalling systems;
– restriction of operation because of malfunction of the communication system.
These effects should be considered in accordance with the appropriate standards.
4.2 Electrical safety of persons
Where a.c. and d.c. voltages are present together the limits for touch voltage given in Clause 7 apply in
addition to the limits given in EN 50122-1:2010, Clause 9.
5 Types of mutual interaction to be considered
5.1 General
Coupling describes the physical process of transmission of energy from a source to a susceptible device.
The following types of coupling shall be considered:
a) galvanic (conductive) coupling;
b) non-galvanic coupling;
1) inductive coupling;
2) capacitive coupling.
Galvanic coupling dominates at low frequencies, when circuit impedances are low. The effects of galvanic
coupling are conductive voltages and currents.
The effects of inductive coupling are induced voltages and hence currents. These voltages and currents
depend inter alia on the distances, length, inducing current conductor arrangement and frequency.
The effects of capacitive coupling are influenced voltages into galvanically separated parts or conductors.
The influenced voltages depend inter alia on the voltage of the influencing system and the distance. Currents
resulting from capacitive coupling are also depending on the frequency.
NOTE As far as the capacitive and inductive coupling are concerned, general experience is that only the influence of the a.c. railway to
the d.c. railway is significant.
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5.2 Galvanic coupling
5.2.1 A.C. and d.c. return circuits not directly connected
A mutual interaction between the return circuits is possible by currents through earth caused by the rail
potential of both a.c. and d.c. railways, for example return currents flowing through the return conductors,
earthing installations of traction power supply substations and cable screens.
In case a conductive parallel path to the return circuit exists in the influenced system, various effects are
possible. In case a vehicle forms part of the parallel path, return current of the influencing railway system can
flow through the propulsion system of the traction unit. The same effects are possible when the return current
of the influencing system flows, for example, through the auto-transformer and substation transformer of an
auto-transformer system or through booster transformers or other devices.
An electric shock with combined voltages can occur when parts of the return circuits or conductive parts
which are connected to the return circuits by voltage limiting devices are located in the overhead contact line
zone of the other railway system, see 8.2.2.
5.2.2 A.C. and d.c. return circuits directly connected or common
In addition to the effects described in 5.2.1 current exchange will be increased where a.c. and d.c. return
circuits are directly connected or common.
NOTE Direct connections can be railway level crossings, common tracks, system separation sections, etc.
Currents flowing between the a.c. railway and the d.c. railway can create mutual interaction between the
return circuits.
Both return circuits are at the same potential at the location of the connection. A short-circuit within the a.c.
system can cause a peak voltage on conductive structures connected to the return circuit of the d.c. railway.
The same effects apply for conductive structures connected to it directly or via a voltage limiting device
(VLD). The voltage across the voltage limiting device can trip the device without a fault on the d.c. side.
The connection of the return circuit of the d.c. railway to the earthed return circuit of the a.c. railway
increases the danger of stray current corrosion.
For requirements for fixed installations see 8.3.
5.3 Non-galvanic coupling
5.3.1 Inductive coupling
An a.c. voltage can be induced on a d.c. contact line system and on the d.c. system’s return circuit. This
effect needs to be considered in case the d.c. railway is within the zone of mutual interaction.
Consequently an a.c. voltage can occur within the d.c. substation at the busbars versus earth (i.e. at the
rectifier or in the feeder cubicles).
Interaction can occur in terms of impermissible touch voltages. See Clause 7.
Perpendicular crossings do not result in inductive effects in the d.c. system.
5.3.2 Capacitive coupling
Within small distances an a.c. voltage can be influenced on a d.c. contact line system when it is isolated with
a disconnector or circuit-breaker open. The possibility shall be considered that the flash-over voltage of the
insulators or of the surge arrestors can be reached.
NOTE Distance depends inter alia on geometry and voltage.
An a.c. voltage can occur within the d.c. substation at the d.c. busbars versus earth, i.e. in the feeder
cubicles.
Interaction can occur in terms of impermissible touch voltages. See Clause 7.
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EN 50122-3:2010 – 8 –
6 Zone of mutual interaction
6.1 General
The a.c. railway affects the d.c. railway and vice-versa by galvanic, inductive and/or capacitive coupling (see
Clause 5). The zone of mutual interaction indicates a distance and a length of parallelism between an a.c.
railway and a d.c. railway (see Annex A). The limits of zone of mutual interaction are based on the limits of
the touch voltage given in Clause 7.
If a zone of mutual interaction exists the requirements given in this European Standard shall be fulfilled.
When the distance between both a.c. and d.c. railways is less than 50 m a zone of mutual interaction is
assumed. Distances in excess of 50 m are dealt with in 6.2 and 6.3.
NOTE 1 When the distance between a.c. and d.c. railways becomes less than 50 m effects as described in 5.2.1 or even 5.2.2 can be
expected.
NOTE 2 Distances between a.c. railway and the d.c. railway cannot be given in a generic way and should be addressed separately
depending on the local conditions.
NOTE 3 For information on analysis and assessment of zone of mutual interaction see Annex C.
6.2 A.C.
In case of an a.c. railway influencing a d.c. railway the zone of mutual interaction is based on voltages
coupled into the affected system.
Where the following preconditions apply the limit of the distance between a.c. and d.c. railway is 1 000 m:
– double track line, where only the four running rails of the a.c. railway are used for the return circuit;
– the inducing current is 500 A per overhead contact line (1 000 A in total);
– the length of parallelism between a.c. and d.c. railway is 4 km;
– the soil resistivity is 100 Ωm;
– the rated frequency is 50 Hz;
– the affected system is insulated versus earth along its entire length and connected to earth at one end
only;
– screening effects of other parallel metallic objects have not been taken into account.
Where other preconditions apply the dimension of the zone of mutual interaction shall be calculated.
NOTE 1 A method for the calculation is given in Annex A.
NOTE 2 The example above is based on a 35 V limit for a.c. with a time duration longer than 300 s.
In case a d.c. railway is within the zone of mutual interaction of an a.c. railway, the level of voltages or
currents coupled into the d.c. system is not necessarily too high; in this case further analysis of the situation
shall be carried out.
6.3 D.C.
For the effects of d.c. railway systems on a.c. railway systems the dimension of the zone of mutual
interaction can be neglected due to the steep voltage gradient in the soil, caused by the insulated rails.
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However if the possibility of a voltage transfer exists, either permanently or temporary, due to a galvanic
connection towards conductive or partly conductive parts, the zone of mutual interaction is given by the
dimensions of those parts. In this case the level of voltages or currents coupled into the a.c. system is not
necessarily too high; further analysis of the situation shall be carried out.
7 Touch voltage limits for the combination of alternating and direct voltages
7.1 General
The limits given in 7.2 to 7.6 are based on touch voltage only and shall not be exceeded. Other effects with
respect to electrical installations are not taken into account.
NOTE 1 Limits for electrical installations cannot be given in a generic way and should be addressed separately if necessary,
depending on the sensitivity of the affected installations.
Where either an alternating or a direct voltage is present the touch voltage limits given in EN 50122-1 apply.
The direct and the alternating components of a combined voltage u(t) for time duration in excess of 1 s are
calculated as follows:
1
a+T
d
dc
U = ⋅ u()t ⋅ t (1)
∫
T
a
1
a+T
2
d
ac dc
U = ⋅()u()t −U ⋅ t (2)
∫
T
a
where
T = 1 s;
t is the time;
u(t) is the combined voltage;
U is the direct component of combined voltage;
dc
U is the alternating component of combined voltage.
ac
NOTE 2 Equation (1) gives the moving average value of the direct component, Equation (2) gives the moving r.m.s. value of the
alternating component.
Only for short-duration phenomena t ≤ 1 s the following definitions for alternating voltage and direct voltage
are used:
– U is defined as that part of the combined voltage that is caused by the d.c. system;
dc
– U is defined as that part of the combined voltage that is caused by the a.c. system.
ac
NOTE 3 Further information on combined voltages is given in Annex B.
NOTE 4 Long-term conditions are associated with operation conditions and short-term conditions are associated with fault conditions
or for example switching operations.
7.2 Touch voltage limits for long-term conditions
The following approach shall be used to check whether the combined voltage is permissible:
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SIST EN 50122-3:2010
EN 50122-3:2010 – 10 –
1. the alternating part of the combined voltage shall not exceed the maximum permissible alternating body
voltage as given in EN 50122-1:2010, Table 3 for the applicable duration;
2. the direct part of the combined voltage shall not exceed the maximum permissible direct body voltage as
given in EN 50122-1:2010, Table 5 for the applicable duration;
3. the combined voltage is permissible if it is within the envelope as given for the applicable duration in
Figure 1;
4. for time durations in excess of 1 s the combined peak value (see explanation in Annex B) shall be less
than 2 × √2 times the maximum permissible alternating body voltage as given in EN 50122-1:2010,
Table 3 for the applicable duration irrespective of frequency content.
NOTE Assuming the maximum permissible direct touch voltage of 120 V being present in the d.c. system the alternating voltage limit
is 35 V, see Figure 1. Assuming the maximum permissible alternating touch voltage of 60 V being present in the a.c. system the direct
voltage limit is 85 V, see Figure 1.
110
V
0,7 s
90
0,8 s
0,9 s
80
1,0 s
70
300 s
60
∞
50
Uac
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 V 190
U
dc
NOTE All values are r.m.s.
Figure 1 ― Maximum permissible combined effective touch voltages
(excluding workshops and similar locations) for long-term conditions
7.3 A.C. system short-term conditions and d.c. system long-term conditions
The following approach shall be used to check whether the combined voltage is permissible:
1. the short-duration alternating part of the combined voltage shall not exceed the maximum permissible
alternating touch voltage as given in EN 50122-1:2010, Table 4 for the applicable duration;
2. the direct part of the combined voltage shall not exceed the maximum permissible direct touch voltage
as given in EN 50122-1:2010, Table 6 for the applicable duration;
3. the combined voltage is permissible if it is within the envelope as given for the applicable durations in
Figure 2.
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900
V
800
0,02 s
700
0,05 s
0,1 s
600
500 0,2 s
400
U
ac 0,3 s
300
0,4 s
200
0,5 s
0,6 s
100
0
0 50 100 150 V 200
Udc
NOTE All values are r.m.s.
Figure 2 ― Maximum permissible combined effective touch voltages
under a.c. short-term conditions and d.c. long-term conditions
NOTE An example of the use of Figure 2 is given in Annex B.
7.4 A.C. system long-term conditions and d.c. system short-term conditions
The following approach shall be used to check whether the combined voltage is permissible:
1. the alternating part of the combined voltage shall not exceed the maximum permissible alternating touch
voltage as given in EN 50122-1:2010, Table 4 for the applicable duration;
2. the short-duration direct part of the combined voltage shall not exceed the maximum permissible direct
touch voltage as given in EN 50122-1:2010, Table 6 for the applicable duration;
3. the combined voltage is permissible if it is within the envelope as given for the applicable durations in
...
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