IEC 60076-22-8:2021

Power transformers - Part 22-8: Power transformer and reactor fittings - Devices suitable for use in communication networks

IEC 60076-22:2021 applies to a selection of accessories and fittings mounted on liquid immersed power transformers according to IEC 60076-1 and reactors according to IEC 60076-6 with or without conservator for indoor or outdoor installation.
It outlines the operation requirements specific to each device as well as the data made available to the communication network and the type and routine test to be performed.

Transformateurs de puissance - Partie 22-8: Accessoires pour transformateurs de puissance et bobines d'inductance - Dispositifs compatibles avec les réseaux de communication

L'IEC 60076-22:2021 s'applique à un ensemble d'accessoires installés sur des transformateurs de puissance immergés dans un liquide conformes à l'IEC 60076-1 et sur des bobines d'inductance conformes à l'IEC 60076-6 avec ou sans conservateur, destinés aux installations intérieures ou extérieures.
Elle spécifie les exigences de fonctionnement spécifiques à chaque dispositif, les données mises à la disposition du réseau de communication, ainsi que les essais de type et les essais individuels de série à réaliser.
Le réseau de communication ne relève pas du domaine d'application du présent document.

General Information

• Status: Published
• Publication Date: 14-Jun-2021
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 14 - Power transformers
• Drafting Committee: WG 32 - TC 14/WG 32
• Current Stage: PPUB - Publication issued
• Start Date: 15-Jun-2021
• Completion Date: 17-Jun-2021

Overview

IEC 60076-22-8:2021 is an international standard published by the International Electrotechnical Commission (IEC) that specifies requirements for power transformer and reactor fittings designed for communication network compatibility. As part 22-8 of the IEC 60076 series on power transformers, this standard focuses on accessories mounted on liquid-immersed power transformers and reactors, applicable for both indoor and outdoor installations.

The standard defines operational requirements, communication data interfaces, and testing protocols for devices integral to transformer and reactor monitoring. These devices include sensors and relays that interface with communication networks to provide real-time diagnostics and condition monitoring, enhancing transformer reliability and asset management.

Key Topics

• Scope and Applicability
  Covers accessories and fittings installed on liquid-immersed power transformers as per IEC 60076-1 and reactors according to IEC 60076-6. Applicable to transformers with or without conservator tanks.

• Communication Network Integration
  Specifies devices that output diagnostic data suitable for integration with communication protocols like Modbus, facilitating remote monitoring and control.

• Device Types and Outputs
  Describes a range of transformer fittings including:

  • Gas and liquid actuated relays (Buchholz relays)
  • Protective relays for sealed liquid-immersed equipment
  • Mechanical and electronic liquid level and temperature indicators
  • Pressure relief devices with continuous monitoring
  • Dehydrating breathers (self-regenerating types)
  • Dissolved Gas Analysis (DGA) devices

  Outputs typically include analog 4 mA to 20 mA signals and digital Modbus interfaces for communication.

• Testing and Compliance
  Establishes type and routine test requirements emphasizing electromagnetic compatibility (EMC), operational safety, and communication protocols conformity.

• Cybersecurity Considerations
  Addresses the need for cybersecurity measures to protect communication channels from unauthorized access or interference.

Applications

IEC 60076-22-8:2021 is essential for utilities, manufacturers, and engineering firms involved in the design, manufacture, installation, and maintenance of power transformers and reactors. The standard facilitates:

• Enhanced Transformer Monitoring
  Enables integration of advanced monitoring devices into communication networks for continuous assessment of transformer health and operational status.

• Predictive Maintenance
  Supports condition-based maintenance strategies by providing accurate, real-time data via standardized communication outputs, reducing unplanned outages.

• Operational Efficiency and Safety
  Promotes reliable operation of transformer fittings with tested protocols and ensures compatibility with industrial communication systems, thus enhancing electrical grid stability.

• Network Management and Automation
  Facilitates remote data access allowing operators to efficiently manage transformer assets across smart grids and automated electrical substations.

Related Standards

• IEC 60076-1: Power transformers – General requirements
• IEC 60076-6: Reactors – General requirements
• IEC 61850 Series: Communication networks and systems in substations (relevant for communication protocol integration)
• IEC 61131 Series: Programmable controllers (for automation compatibility)
• ISO/IEC 27000 Series: Information security management (for cybersecurity frameworks)

Summary

Adhering to IEC 60076-22-8:2021 ensures that power transformer and reactor fittings are equipped for seamless and secure communication with modern monitoring systems. This supports electrical grid modernization efforts, enhances asset management through advanced diagnostics, and contributes to reliable power delivery by standardizing the interoperability of critical transformer devices within communication networks.

Standards Content (Sample)

IEC 60076-22-8 ®
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Power transformers –
Part 22-8: Power transformer and reactor fittings – Devices suitable for use in
communication networks
Transformateurs de puissance –
Partie 22-8: Accessoires pour transformateurs de puissance et bobines
d'inductance – Dispositifs compatibles avec les réseaux de communication

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IEC 60076-22-8 ®
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Power transformers –
Part 22-8: Power transformer and reactor fittings – Devices suitable for use in

communication networks
Transformateurs de puissance –

Partie 22-8: Accessoires pour transformateurs de puissance et bobines

d'inductance – Dispositifs compatibles avec les réseaux de communication

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-9861-9

– 2 – IEC 60076-22-8:2021 © IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 General requirements . 8
4.1 Standard compliance . 8
4.2 Modbus requirements . 8
4.3 Type tests for EMC . 9
4.3.1 Emission . 9
4.3.2 Immunity . 9
4.4 Additional requirements . 9
4.4.1 Terminals . 9
4.4.2 Signal and control ports . 9
4.5 Cybersecurity . 10
5 Power supply . 10
6 Devices . 10
6.1 Gas and liquid actuated relays (Buchholz relays) . 10
6.1.1 General . 10
6.1.2 4 mA to 20 mA output . 10
6.1.3 Modbus output . 10
6.1.4 Tests . 11
6.2 Protective relays for hermetically sealed liquid-immersed equipment . 11
6.2.1 General . 11
6.2.2 4 mA to 20 mA output . 11
6.2.3 Modbus output . 11
6.2.4 Tests . 11
6.3 Direct reading dial type liquid level indicators . 12
6.3.1 General . 12
6.3.2 4 mA to 20 mA output . 12
6.3.3 Modbus output . 12
6.3.4 Tests . 12
6.4 Pressure relief devices with continuous pressure monitoring . 12
6.4.1 General . 12
6.4.2 4 mA to 20 mA output . 13
6.4.3 Modbus output . 13
6.4.4 Routine test . 13
6.5 Electronic pressure and pressure rise monitoring systems . 13
6.5.1 General . 13
6.5.2 4 mA to 20 mA output . 13
6.5.3 Modbus output . 13
6.5.4 Tests . 14
6.6 Direct reading mechanical dial type liquid temperature indicators . 15
6.6.1 General . 15
6.6.2 4 mA to 20 mA output . 15
6.6.3 Modbus output . 15

6.6.4 Routine tests . 15
6.7 Direct reading mechanical dial type winding temperature indicators . 15
6.7.1 General . 15
6.7.2 4 mA to 20 mA output . 15
6.7.3 Modbus output . 16
6.7.4 Routine tests . 16
6.8 Electrical and electronic liquid temperature measuring devices . 16
6.8.1 General . 16
6.8.2 4 mA to 20 mA output . 16
6.8.3 Modbus output . 16
6.8.4 Tests . 16
6.9 Electrical and electronic winding temperature simulating devices . 17
6.9.1 General . 17
6.9.2 4 mA to 20 mA output . 17
6.9.3 Modbus output . 17
6.9.4 Tests . 17
6.10 Dehydrating breathers, self-regenerating types . 18
6.10.1 General . 18
6.10.2 4 mA to 20 mA output . 18
6.10.3 Modbus output . 19
6.10.4 Routine tests . 19
6.11 Dissolved gas analysis devices (DGA devices) . 19
6.11.1 General . 19
6.11.2 4 mA to 20 mA output . 19
6.11.3 Modbus output . 20
6.11.4 Tests . 20
Bibliography . 21

Figure 1 – Pressure rise response curves for oil (left) or gas (right) space applications . 14

Table 1 – Summary of Modbus parameters . 9

– 4 – IEC 60076-22-8:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 22-8: Power transformer and reactor fittings –
Devices suitable for use in communication networks

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 60076-22-8 has been prepared by IEC technical committee 14: Power transformers. It is
an International Standard.
The text of this International Standard is based on the following documents:
CDV Report on voting
14/1057/CDV 14/1062A/RVC
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 60076 series, published under the general title Power transformers,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60076-22-8:2021 © IEC 2021
INTRODUCTION
Under the title "Power transformer and reactor fittings – Devices suitable for use in
communication networks", IEC 60076-22-8 covers an exhaustive selection of devices that are
currently used in communication networks.

POWER TRANSFORMERS –
Part 22-8: Power transformer and reactor fittings –
Devices suitable for use in communication networks

1 Scope
This part of IEC 60076-22 applies to a selection of accessories and fittings mounted on liquid
immersed power transformers according to IEC 60076-1 and reactors according to IEC 60076-6
with or without conservator for indoor or outdoor installation.
It outlines the operation requirements specific to each device as well as the data made available
to the communication network and the type and routine test to be performed.
The communication network is not part of the scope of this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
IEC 60076-22-1:2019, Power transformers – Part 22-1: Power transformer and reactor fittings
– Protective devices
IEC 60076-22-7, Power transformers – Part 22-7: Power transformer and reactor fittings –
Accessories and fittings
IEC 61000-6-4, Electromagnetic compatibility (EMC) – Part 6-4: Generic standards – Emission
standard for industrial environments
IEC 61000-6-5, Electromagnetic compatibility (EMC) – Part 6-5: Generic standards – Immunity
for equipment used in power station and substation environment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
communication network
collection of terminal nodes
Note 1 to entry: Links are connected to enable communication between the devices.
Note 2 to entry: Means of transmission of signals in one direction between two points.

– 8 – IEC 60076-22-8:2021 © IEC 2021
3.2
communication protocol
defined set of procedures adopted to ensure communication between sets of processes which
exist within the same layer of a hierarchy of layers
[SOURCE: IEC 60050-716-1:1995, 716-01-17, modified – In the term "communication" has
been added.]
3.3
Modbus protocol
serial communications protocol
Note 1 to entry: Modbus is a de facto standard communication protocol and it is now a commonly available means
of connecting industrial electronic devices.
Note 2 to entry: Modbus is often used to connect a supervisory computer with a remote terminal unit (RTU) in
supervisory control and data acquisition (SCADA) systems.
3.4
4 mA to 20 mA output
point-to-point or multi-drop circuit
Note 1 to entry: This type of circuit sends an analogue signal from 4 mA to 20 mA that represents the extremes of
the process variable.
3.5
electrical and electronic liquid temperature measuring device
device measuring the liquid temperature using electrical or electronic sensors
3.6
electrical and electronic winding temperature simulating device
device simulating the winding temperature using electrical or electronic sensors
3.7
dissolved gas analysis device
DGA device
device used to measure the dissolved gas concentration within a liquid on a regular time basis
Note 1 to entry: This device usually also measures relative humidity and temperature of the liquid.
Note 2 to entry: This note applies to the French language only.
4 General requirements
4.1 Standard compliance
All devices shall comply with IEC 60076-22-1 and IEC 60076-22-7 as applicable.
All devices shall be subject to type tests to verify the electromagnetic compatibility.
4.2 Modbus requirements
If not otherwise specified, Modbus output shall be of the RTU type. The manufacturer shall
provide all information about the Modbus connection needed by the customer to configure the
connection.
The digital information shall be available via an RS485 port.
Table 1 shows a summary of Modbus parameters.

Table 1 – Summary of Modbus parameters
Parameters Possible values Code Default values
Address Add 1 to 247 001 to 247 NA
4 800 bits/s 4,8 19 200 bits/s
Baud rate 9 600 bits/s 9,6 or alternatively
19 200 bits/s 19,2 9 600 bits/s
8 databits, uneven parity, 1 stop bit 8O1
8E1
8 databits, even parity, 1 stop bit 8E1
Number, parity
or alternatively
and stop bits
8 databits, no parity, 1 stop bit 8N1
8N1
8 databits, no parity, 2 stop bits 8N2

On special request TCP/IP can be provided.
4.3 Type tests for EMC
4.3.1 Emission
The equipment shall comply with IEC 61000-6-4, measured as table top arrangement, at 3 m
with all doors and caps closed. All relevant tests shall be performed.
4.3.2 Immunity
The equipment shall comply with IEC 61000-6-5, interface 4 for both substation and power
station. All relevant tests shall be performed.
4.4 Additional requirements
4.4.1 Terminals
In addition to the terminals defined in IEC 60076-22-1, the device shall be equipped with a
minimum of 2 additional terminals for each 4 mA to 20 mA output and 3 for each Modbus in and
output and 2 additional terminals for power supply if the 4 mA to 20 mA outputs are active.
Unless otherwise specified, the 4 mA to 20 mA output shall be active.
The terminal block shall be suitable for cables of 1,5 mm , unless otherwise specified.
By agreement between manufacturer and purchaser the device can be fitted with plug and
socket.
4.4.2 Signal and control ports
4.4.2.1 4 mA to 20 mA
Maximum cable length between the device and the data acquisition system shall be 30 m.
Maximum resistance to be applied shall be 450 Ω.
4.4.2.2 Modbus
Maximum cable length between the device and the data acquisition system shall be 30 m.

– 10 – IEC 60076-22-8:2021 © IEC 2021
4.5 Cybersecurity
Electronic devices covered by this document are not linked to Internet or other external
networks. Therefore there are no requirements for cybersecurity in this document.
If on special request the device is connected to Internet, cybersecurity issues shall be
addressed.
5 Power supply
Preferred power supply for the communication part of the device is 24 V DC. The tolerance on
the rated voltage shall be ±20 % permanently. The residual alternative voltage component shall
be less than 2 % of the voltage peak to peak.
If the device (for example self-regenerating dehydrating breather) needs for its operation
(beside the communication) an AC or DC power supply, then the communication power can be
derived from the operation power supply.
6 Devices
6.1 Gas and liquid actuated relays (Buchholz relays)
6.1.1 General
The volume of gas is monitored continuously by an additional component embedded in the
Buchholz relay.
Upon customer requirements, the information can be analogue given via a 4 mA to 20 mA output
and/or digital via the Modbus protocol.
The performance of the contacts specified in IEC 60076-22-1 shall not be affected by the
requirements detailed in this Subclause 6.1.1.
6.1.2 4 mA to 20 mA output
The 4 mA to 20 mA output monitors the gas volume accumulation.
Therefore the 4 mA shall correspond to the Buchholz relay completely full of liquid (no gas) and
the 20 mA shall correspond to the Buchholz relay completely empty of liquid (full of gas).
The manufacturer shall state a transfer function of the 4 mA to 20 mA output signal to the
volume of the accumulated gas.
If the gas accumulation from zero to the point before gas escapes into the pipework towards
the conservator can be expected to be linear within ±5 %, then the manufacturer may declare,
as a simplification, only the value of the accumulated gas volume before any gas escapes into
the pipework towards the conservator and the corresponding value of mA.
6.1.3 Modbus output
The digital output by Modbus shall transmit at least the gas volume monitored, measured in
cm .
6.1.4 Tests
6.1.4.1 Routine test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.1.4.2 Type test
The manufacturer shall perform a test to determine the transfer function of the 4 mA to 20 mA
output signal to the volume of the accumulated gas for each design of Buchholz relay.
6.2 Protective relays for hermetically sealed liquid-immersed equipment
6.2.1 General
The volume of gas, the temperature and the pressure are monitored.
Upon customer requirements, the information can be analogue given via a 4 mA to 20 mA output
or digital via the Modbus protocol, or both.
The performance of the contacts specified in IEC 60076-22-1 shall not be affected by the
requirements detailed in this Subclause 6.2.1.
6.2.2 4 mA to 20 mA output
Separate 4 mA to 20 mA outputs monitor the gas volume accumulation, the temperature and
the pressure.
For the gas volume monitoring, the 4 mA output value shall correspond to the protective relay
completely full of liquid (no gas) and the 20 mA output value shall correspond to the protective
relay completely empty of liquid (full of gas).
The manufacturer shall state a transfer function of the 4 mA to 20 mA output signal to the
volume of the accumulated gas, if not linear.
For the temperature monitoring, the temperature of 40 °C shall generate the 4 mA signal; the
temperature of 120 °C shall generate the 20 mA signal.
For the pressure monitoring, the value of 4 mA shall indicate the overpressure of 10 kPa; the
value of overpressure corresponding to 20 mA shall be 50 kPa.
6.2.3 Modbus output
The digital output by Modbus shall transmit at least the gas volume, measured in cm , the
temperature and the pressure.
6.2.4 Tests
6.2.4.1 Routine test
6.2.4.1.1 Electronic board test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.2.4.1.2 Accuracy tests
During the functional test of the protective relay according to IEC 60076-22-1, the accuracy of
the temperature output shall be verified. The tolerance between the liquid thermostatic bath
temperature and the output shall be less than ±4 °C.

– 12 – IEC 60076-22-8:2021 © IEC 2021
NOTE Accuracy always refers to the thermostatic bath and therefore a difference between the output and the pointer
temperature indication can occur.
During the functional test of the protective relay according to IEC 60076-22-1, the accuracy of
the pressure output shall be verified. The tolerance between the reference pressure and the
output shall be less than ±5 kPa.
6.2.4.2 Type test
The manufacturer shall perform a test to determine the transfer function of the 4 mA to 20 mA
output signal to the volume of the accumulated gas for each design of protective relay.
6.3 Direct reading dial type liquid level indicators
6.3.1 General
The level of the liquid in the compartment is monitored by the mechanical component of the
liquid level indicator and transmitted continuously by an electronic system.
Upon customer requirements, the transmitted information can be analogue, given via a 4 mA to
20 mA output or digital via the Modbus protocol, or both.
The performance of the contacts specified in IEC 60076-22-1 shall not be affected by the
requirements detailed in this Subclause 6.3.1.
6.3.2 4 mA to 20 mA output
The 4 mA to 20 mA output monitors the liquid level.
The minimum position of the pointer shall generate a current of 4 mA; the maximum position of
the pointer shall generate a current of 20 mA. These minimum and maximum positions may not
correspond to the dial markings.
The law of variation of the 4 mA to 20 mA output in relation to the actual height of the sensor
shall be supplied by the device manufacturer, if not linear.
6.3.3 Modbus output
The digital output by Modbus shall transmit at least the liquid level monitoring as a percentage
of the movement of the pointer from minimum to maximum level.
6.3.4 Tests
6.3.4.1 Routine test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.3.4.2 Type test
The manufacturer shall perform a test to prove the correspondence of the electronic output to
the position of the pointer.
6.4 Pressure relief devices with continuous pressure monitoring
6.4.1 General
The pressure of the liquid in the compartment is monitored continuously by an additional
component embedded in the pressure relief device.

Upon customer requirements, the information can be analogue given via a 4 mA to 20 mA output
or digital via the Modbus protocol, or both.
The performance of the contacts specified in IEC 60076-22-1 shall not be affected by the
requirements detailed in this Subclause 6.4.1.
6.4.2 4 mA to 20 mA output
The 4 mA to 20 mA output shall monitor the liquid pressure.
The value of 4 mA shall indicate the overpressure of 0 kPa; the value of overpressure
corresponding to 20 mA shall be declared by the manufacturer and be over the maximum
operating pressure of the pressure relief device.
The law of variation of the 4 mA to 20 mA output in relation to the actual liquid pressure shall
be supplied by the device manufacturer, if not linear.
6.4.3 Modbus output
The digital output by Modbus shall transmit at least the liquid pressure monitoring.
6.4.4 Routine test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.5 Electronic pressure and pressure rise monitoring systems
6.5.1 General
The electronic pressure monitoring system uses sensors that convert the pressure of the liquid
or gas space to a corresponding 4 mA to 20 mA signal and measure the rate of pressure change.
The range of operation covers a span of at least 200 kPa and the sensor output is a
corresponding 4 mA to 20 mA signal wired to the electronic circuit board.
The device output has two primary functions:
a) to provide a measurement of the static pressure of the transformer tank at any given time
and assert an alarm per the users' requirements;
b) to measure the rate of change of pressure and to assert an alarm commonly used as part
of a trip circuit. The sensor output is measured for increasing magnitude and speed by
integrating the signal over time. If the output exceeds the threshold rate of 1,5 kPa/s for
longer than the threshold time, an output relay will change state, providing the user with an
alarm or trip signal.
6.5.2 4 mA to 20 mA output
The 4 mA to 20 mA output is dedicated to monitor the pressure of the liquid or gas space.
The value of 4 mA shall indicate the pressure of 0 kPa; the value of pressure corresponding to
20 mA shall be declared by the manufacturer.
The law of variation of the 4 mA to 20 mA output in relation to the actual liquid or gas pressure
shall be supplied by the device manufacturer, if not linear.
6.5.3 Modbus output
The digital output by Modbus shall transmit at least the pressure of the liquid or gas space.

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6.5.4 Tests
6.5.4.1 Routine tests
6.5.4.1.1 Insulation test
The manufacturer shall perform a short duration (60 s) power frequency withstand voltage test
between independent circuits and between all circuits together and earth.
The test voltage is given in Table 1 of IEC 60076-22-1:2019.
6.5.4.1.2 Electronic board test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.5.4.1.3 Accuracy test
The accuracy test shall verify that:
• the fast pressure rise function is set between the pressure rise response curves for use
with oil or gas shown on Figure 1;
• the slow pressure rise function is in a ±2 % span at 25 °C (includes linearity hysteresis
and repeatability).
Rapid pressure rise relay
response curves
Figure 1 – Pressure rise response curves for oil (left) or gas (right) space applications
6.5.4.2 Vibration type test
The device shall be subjected to vibrations in accordance with 4.6 of IEC 60076-22-1:2019; no
malfunction shall be recorded.
6.5.4.3 Special test – Seismic withstand test
Upon customer request, the device shall withstand a seismic test in accordance with 4.7 of
IEC 60076-22-1:2019.
6.6 Direct reading mechanical dial type liquid temperature indicators
6.6.1 General
The temperature of the liquid in the compartment is monitored by the mechanical component of
the liquid temperature indicator and transmitted continuously by an electronic system.
Upon customer requirements, the information can be analogue given via a 4 mA to 20 mA output
or digital via the Modbus protocol, or both.
The performance of the contacts specified in IEC 60076-22-1 shall not be affected by the
requirements detailed in this Subclause 6.1.1.
6.6.2 4 mA to 20 mA output
The 4 mA to 20 mA output monitors the liquid temperature.
The minimum temperature marked on the dial shall generate a current of 4 mA; a value of the
20 mA shall be generated at the maximum temperature marked on the dial.
The law of variation of the 4 mA to 20 mA output in relation to the actual liquid temperature
shall be supplied by the device manufacturer, if not linear.
6.6.3 Modbus output
The digital output by Modbus transmits at least the liquid temperature monitoring.
6.6.4 Routine tests
6.6.4.1 Electronic board test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.6.4.2 Accuracy test
During the functional test of the liquid temperature indicator according to IEC 60076-22-1, the
accuracy of the output shall be verified. The tolerance between the liquid thermostatic bath
temperature and the output shall be less than ±2 % of the full scale value.
NOTE Accuracy always refers to the thermostatic bath and therefore a difference between the output and the pointer
temperature indication can occur.
6.7 Direct reading mechanical dial type winding temperature indicators
6.7.1 General
The temperature of the winding simulated by the winding temperature indicator is monitored by
the mechanical component of the winding temperature indicator and transmitted continuously
by an electronic system.
Upon customer requirements, the information can be analogue given via a 4 mA to 20 mA output
or digital via the Modbus protocol, or both.
The performance of the contacts specified in IEC 60076-22-1 shall not be affected by the
requirements detailed in this Subclause 6.7.1.
6.7.2 4 mA to 20 mA output
The 4 mA to 20 mA output monitors the winding temperature.

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The minimum temperature marked on the dial shall generate a current of 4 mA; a value of 20 mA
shall be generated at the maximum temperature marked on the dial.
The law of variation of the 4 mA to 20 mA in relation to the simulated winding temperature shall
be supplied by the device manufacturer, if not linear.
6.7.3 Modbus output
The digital output by Modbus transmits at least the winding temperature monitoring.
6.7.4 Routine tests
6.7.4.1 Electronic board test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.7.4.2 Accuracy test
During the functional test of the winding temperature indicator according to IEC 60076-22-1,
the accuracy of the output shall be verified. The tolerance between the liquid thermostatic bath
temperature and the output shall be less than ±2 % of the full scale value.
NOTE Accuracy always refers to the thermostatic bath and therefore a difference between the output and the pointer
temperature indication can occur.
6.8 Electrical and electronic liquid temperature measuring devices
6.8.1 General
The temperature of the liquid is continuously measured by electrical or electronic sensors;
typical examples of sensors are Pt 100 or Cu 10.
The values measured by the system are then transferred to a 4 mA to 20 mA output or Modbus
protocol for remote reading.
The manufacturer shall indicate for each device the temperature range it is set for.
6.8.2 4 mA to 20 mA output
The 4 mA to 20 mA output is dedicated to the reading of the temperature; the minimum
temperature shall generate a current of 4 mA, the maximum temperature shall generate a
current of 20 mA.
The law of variation of the 4 mA to 20 mA output in relation to the liquid temperature shall be
supplied by the device manufacturer, if not linear.
6.8.3 Modbus output
The digital output by Modbus shall transmit the liquid temperature monitoring.
6.8.4 Tests
6.8.4.1 Routine tests
6.8.4.1.1 Insulation test
The manufacturer shall perform a short duration (60 s) power frequency withstand voltage test
between independent circuits and between all circuits together and earth.
The test voltage is given in Table 1 of IEC 60076-22-1:2019.

6.8.4.1.2 Electronic board test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.8.4.1.3 Functional test
The following functional test shall be carried out to prove the correspondence of the reading to
the temperature:
– accuracy of the temperature measurement across the measuring range; at least two points
within the measuring range separated by at least 60 °C shall be compared to the
temperature of a liquid thermostatic bath.
The maximum tolerance on the reading shall be ±2 % of the measuring range.
6.8.4.2 Type test – Vibration test
The device shall be subjected to vibrations in accordance with 4.6 of IEC 60076-22-1:2019; no
malfunction shall be recorded.
6.8.4.3 Special test – Seismic withstand test
Upon customer request, the device shall withstand a seismic test in accordance with 4.7 of
IEC 60076-22-1:2019.
6.9 Electrical and electronic winding temperature simulating devices
6.9.1 General
The temperature of the winding is continuously simulated by a current reacting element and by
electrical or electronic sensors; typical examples of sensors are Pt 100 or Cu 10.
The values measured by the sensor are transferred to a 4 mA to 20 mA output and/or Modbus
protocol for remote reading.
The manufacturer shall indicate for each device the temperature range it is set for.
NOTE This device can be combined with a mechanical dial type reading element.
6.9.2 4 mA to 20 mA output
The 4 mA to 20 mA output is dedicated to the reading of the winding temperature; the minimum
temperature shall generate a current of 4 mA, the maximum temperature shall generate a
current of 20 mA.
The law of variation of the 4 mA to 20 mA output in relation to the simulated winding temperature
shall be supplied by the device manufacturer, if not linear.
6.9.3 Modbus output
The digital output by Modbus shall transmit the winding temperature.
6.9.4 Tests
6.9.4.1 Routine tests
6.9.4.1.1 Insulation test
The manufacturer shall perform a short duration (60 s) power frequency withstand voltage test
between independent circuits and between all circuits together and earth.

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The test voltage is given in Table 1 of IEC 60076-22-1:2019.
Any part connected to the current circuit shall be tested at 2,5 kV for 60 s.
6.9.4.1.2 Electronic board test
The electronic board shall be checked to verify that all the functions are performed correctly.
6.9.4.1.3 Functional test
The following functional tests shall be carried out to prove the correspondence of the reading
to the temperature:
– accuracy of the temperature measurement across the measurin
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