IEC 60076-22-1:2019

IEC 60076-22-1 ®
Edition 1.0 2019-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power transformers –
Part 22-1: Power transformer and reactor fittings – Protective devices

Transformateurs de puissance –
Partie 22-1: Accessoires pour transformateurs de puissance et bobines
d'inductance – Dispositifs de protection

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IEC 60076-22-1 ®
Edition 1.0 2019-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Power transformers –
Part 22-1: Power transformer and reactor fittings – Protective devices

Transformateurs de puissance –

Partie 22-1: Accessoires pour transformateurs de puissance et bobines

d'inductance – Dispositifs de protection

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-6505-5

– 2 – IEC 60076-22-1:2019 © IEC 2019
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Service conditions . 10
4.1 General . 10
4.2 Degree of protection . 10
4.3 Corrosion protection . 11
4.4 Resistance to ambient conditions . 11
4.5 Insulating liquid characteristics . 11
4.6 Vibration withstand . 11
4.7 Seismic requirements. 11
5 Characteristics of switches . 11
5.1 General . 11
5.2 Dielectric strength (in accordance with IEC 60255-27) . 11
6 General requirements for routine and type test . 12
7 Protective devices . 12
7.1 Gas and liquid actuated relay (Buchholz relay) . 12
7.1.1 Additional service conditions . 12
7.1.2 Mechanical requirements . 12
7.1.3 Performance requirements . 16
7.1.4 Tests . 17
7.2 Gas and liquid sampling device at man’s height . 20
7.2.1 Additional service conditions – Operating pressure . 20
7.2.2 Mechanical requirements . 20
7.2.3 Performance requirements – Visibility . 20
7.2.4 Tests . 20
7.3 Protective relay for hermetically sealed liquid-immersed equipment . 21
7.3.1 Additional service conditions . 21
7.3.2 Mechanical requirements . 22
7.3.3 Performance requirements . 24
7.3.4 Tests . 25
7.4 Direct reading dial type liquid level indicators . 27
7.4.1 Mechanical requirements . 27
7.4.2 Performance requirements . 28
7.4.3 Tests . 28
7.5 Liquid flow indicators . 29
7.5.1 Mechanical requirements . 29
7.5.2 Performance requirements . 31
7.5.3 Tests . 31
7.6 Pressure relief devices. 33
7.6.1 Additional service conditions . 33
7.6.2 Mechanical requirements . 33
7.6.3 Performance requirements . 36
7.6.4 Tests . 37

7.7 Pressure relief valves . 38
7.7.1 Additional service conditions . 38
7.7.2 Mechanical requirements . 38
7.7.3 Performance requirements – Nominal operating pressure . 39
7.7.4 Tests . 39
7.8 Direct reading mechanical dial type liquid temperature indicators . 40
7.8.1 Mechanical requirements . 40
7.8.2 Performance requirements . 41
7.8.3 Tests . 42
7.9 Direct reading mechanical dial type winding temperature indicators . 44
7.9.1 Mechanical requirements . 44
7.9.2 Performance requirements . 46
7.9.3 Tests . 47
7.10 Shutter valve. 48
7.10.1 Additional service conditions . 48
7.10.2 Mechanical requirements . 48
7.10.3 Functional requirements . 49
7.10.4 Performance requirements . 50
7.10.5 Tests . 51
7.11 Liquid-flow controlled relay for on-load tap-changer . 52
7.11.1 Additional service conditions . 52
7.11.2 Mechanical requirements . 53
7.11.3 Performance requirements . 54
7.11.4 Tests . 55
7.12 Sudden pressure relay . 57
7.12.1 Additional service conditions . 57
7.12.2 Mechanical requirements . 57
7.12.3 Performance requirements . 58
7.12.4 Tests . 59
7.13 Dial type gas detecting device . 61
7.13.1 Additional service conditions . 61
7.13.2 Mechanical requirements . 61
7.13.3 Performance requirements – Switches . 63
7.13.4 Tests . 64
7.14 Gas detecting device for sealed compartment . 65
7.14.1 Additional service conditions . 65
7.14.2 Mechanical requirements . 66
7.14.3 Performance requirements . 67
7.14.4 Tests . 68
7.15 Leakage detector for insulating liquid to water heat exchangers . 69
7.15.1 Additional service conditions . 69
7.15.2 Mechanical requirements . 70
7.15.3 Performance requirements . 70
7.15.4 Tests . 71
Bibliography . 73

Figure 1 – DN 25 to 100 with circular flanges . 14
Figure 2 – DN 25 with threaded connections . 15

– 4 – IEC 60076-22-1:2019 © IEC 2019
Figure 3 – Gas and liquid operated relay with rectangular flanges for DN 80 mm . 16
Figure 4 – Outline and mounting details: general view . 23
Figure 5 – Fixing detail and terminal box arrangement . 24
Figure 6 – Flange interface . 35
Figure 7 – Maximum overall dimensions . 36
Figure 8 – Mounting interface and general overall dimensions . 39
Figure 9 – General overall dimensions . 54
Figure 10 – Overall dimensions . 58
Figure 11 – Sudden pressure rise relay response curves . 59
Figure 12 – Overall dimensions . 63
Figure 13 – Mounting arrangement . 65
Figure 14 – Mounting dimensions . 67

Table 1 – Dielectric strength of switches – Power frequency . 12
Table 2 – Dielectric strength of switches – Impulse . 12
Table 3 – Preferred dimensions of relay body in mm . 14
Table 4 – Flange dimensions in mm . 14
Table 5 – Alternative dimensions of relay in mm . 15
Table 6 – Alternative flange dimensions of the relay in mm . 15
Table 7 – Making and breaking capacity – Buchholz relay . 16
Table 8 – Steady liquid flow for relay operation . 17
Table 9 – Identification of relays . 23
Table 10 – Making and breaking capacity – Protective relay . 25
Table 11 – Making and breaking capacity – OLI . 28
Table 12 – Making and breaking capacity – OFI . 31
Table 13 – Fixing interface dimensions according to Figure 6 . 34
Table 14 – Overall dimensions according to Figure 7 . 35
Table 15 – Making and breaking capacity – PRD . 37
Table 16 – Fixing interface and overall dimensions according to Figure 8 . 39
Table 17 – Making and breaking capacity – OTI . 42
Table 18 – Making and breaking capacity – WTI . 46
Table 19 – Making and breaking capacity – Shutter valve . 50
Table 20 – Preferred dimensions of relay body in mm . 54
Table 21 – Flange dimensions in mm . 54
Table 22 – Making and breaking capacity – Liquid flow relay . 55
Table 23 – Making and breaking capacity – Sudden pressure relay . 59
Table 24 – Making and breaking capacity – Dial type gas detecting device . 63
Table 25 – Making and breaking capacity – Gas detecting device . 67
Table 26 – Making and breaking capacity – Leakage detector . 71

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
POWER TRANSFORMERS –
Part 22-1: Power transformer and reactor fittings – Protective devices

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
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6) All users should ensure that they have the latest edition of this publication.
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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.
International Standard IEC 60076-22-1 has been prepared by IEC technical committee TC14:
Power transformers.
The text of this International Standard is based on the following documents:
FDIS Report on voting
14/992/FDIS 14/997/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC 60076-22-1:2019 © IEC 2019
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
This Part 22-1 of the IEC 60076 series covers all accessories relevant to the safety of
transformers or reactors and having a function of signalization of abnormal operating
conditions, and outlines the operation requirements specific to each accessory.

– 8 – IEC 60076-22-1:2019 © IEC 2019
POWER TRANSFORMERS –
Part 22-1: Power transformer and reactor fittings – Protective devices

1 Scope
This part of IEC 60076-22 applies to protective devices mounted on liquid-immersed power
transformers in accordance with IEC 60076-1 and reactors in accordance with IEC 60076-6
with or without conservator for indoor or outdoor installation. It outlines the service conditions
and the mechanical and electrical requirements that are common to all the devices, which are
relevant for the safety of the machine having a function of signalization of abnormal operating
conditions.
It also outlines the operation requirements specific to each device as well as, in some cases,
the preferred dimensions relevant for interchangeability and the type and routine test to be
performed.
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 60068-3-3:1991, Environmental testing – Part 3-3: Guidance – Seismic test methods for
equipments
IEC 60076-1:2011, Power transformers – Part 1: General
IEC 60076-7, Power transformers – Part 7: Loading guide for oil-immersed power
transformers
IEC 60296, Fluids for electrotechnical applications –Unused mineral insulating oils for
transformers and switchgear
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60721-3-4, Classification of environmental conditions – Part 3: Classification of groups of
environmental parameters and their severities – Section 4: Stationary use at non-
weatherprotected locations
IEC 60947-5-1 , Low-voltage switchgear and control gear – Part 5-1: Control circuit devices
and switching elements – Electromechanical control circuit devices
ISO 228-1Pipe threads where pressure-tight joints are not made on the threads – Part 1:
Dimensions, tolerances and designation
ISO 12944-6, Paints and varnishes – Corrosion protection of steel structures by protective
paint systems – Part 6: Laboratory performance test methods

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
gas and liquid actuated relay
Buchholz relay
device intended to detect gas release from the unit to be protected, liquid surge from the tank
to the conservator and complete loss of liquid in the conservator
3.2
gas and liquid sampling device at man’s height
device allowing gas and liquid sampling from the Buchholz relay from ground level
3.3
protective relay for hermetically sealed liquid-immersed equipment
multifunctional protective device for hermetically sealed, liquid-immersed equipment without
gas cushion
3.4
direct reading dial type liquid level indicator
oil level indicator
OLI
device indicating the liquid level in the main conservator or in a separate compartment
Note 1 to entry: This note applies to the French language only.
3.5
liquid flow indicator
oil flow indicator
OFI
device that detects the liquid flow in a forced cooling system
Note 1 to entry: This note applies to the French language only.
3.6
pressure relief device
PRD
device that releases the internal overpressure over a pre-set value, on medium and large
power transformers
Note 1 to entry: This note applies to the French language only.
3.7
pressure relief valve
PRV
device that releases the internal overpressure over a pre-set value, on small transformers
Note 1 to entry: This note applies to the French language only.

– 10 – IEC 60076-22-1:2019 © IEC 2019
3.8
direct reading mechanical dial type liquid temperature indicator
oil temperature indicator
OTI
device that indicates the temperature of the liquid of the transformer
Note 1 to entry: This note applies to the French language only.
3.9
direct reading mechanical dial type winding temperature indicator
winding temperature indicator
WTI
device which indicates the estimated temperature of the winding of the transformer
Note 1 to entry: This note applies to the French language only.
3.10
shutter valve
device which stops the liquid flow from conservator to tank in the event of a consistent liquid
loss from the tank
3.11
liquid-flow control relay for on-load tap changer
device installed in the pipe between the top of the diverter or selector switch of an on-load tap
changer and the liquid conservator to respond at a predetermined liquid flow and enable the
transformer to be tripped
3.12
sudden pressure relay
mechanical device for detection of sudden pressure rise events
3.13
dial type gas detecting device
device for indication of gas accumulation in a sealed liquid filled transformer
3.14
gas detecting device for sealed compartment
device for detecting the presence of gas in a sealed liquid filled compartment
3.15
leakage detector for insulating liquid to water heat exchangers
device for detecting the leakage of water or insulating liquid in a double tube heat exchanger
4 Service conditions
4.1 General
The service conditions set out in 4.2 of IEC 60076-1:2011 represent the normal scope of
operation of the devices and equipment specified in this document.
For any unusual service conditions that require special consideration in the design of the
devices and equipment, see 5.5 of IEC 60076-1:2011. Device specification for operation
under such unusual service conditions shall be subject to agreement between the purchaser
and the manufacturer.
4.2 Degree of protection
The degree of protection of the connecting box or terminal box for outdoor installation shall be
at least IP 54 in accordance with IEC 60529, unless otherwise specified by the purchaser.

4.3 Corrosion protection
The materials used for the construction of the devices and equipment or the surface treatment
shall be resistant to the insulating liquid and suitable to withstand the environmental
conditions. Unless otherwise specified, minimum withstand level shall be C4 medium
durability (see ISO 12944-6).
4.4 Resistance to ambient conditions
The materials used for the construction of the devices and equipment shall be UV resistant
and suitable for outdoor operation; windows and sight glasses shall not become opaque over
the life of the accessory.
4.5 Insulating liquid characteristics
This subclause concerns only the accessories that are in contact with the insulating liquid.
If not otherwise specified, the insulating liquid is mineral liquid in accordance with IEC 60296
and the operating temperature shall be in accordance with IEC 60076-7.
If the insulating liquid is not mineral oil, then the viscosity variation and the operating
temperature shall be indicated by the purchaser. The performance of the devices depends on
the liquid properties and should be adapted if necessary.
2 2
NOTE IEC 60296 specifies a maximum viscosity of 12 mm /s at 40 °C and 1 800 mm /s at – 30 °C; IEC 60076-7
indicates a top liquid temperature for normal cyclic loading of 105 °C and 115 °C for emergency loading.
4.6 Vibration withstand
The accessories shall withstand:
• a non-stationary vibration causing a vertical shock of 100 m/s , with type 1 spectrum in
accordance with IEC 60721-3-4;
• a stationary sinusoidal vibration class 4M4 according to IEC 60721-3-4. By agreement
between purchaser and supplier, class 4M6 may also be specified.
4.7 Seismic requirements
When the accessory is specified with a seismic requirement without specified acceleration
values, the performance level shall be chosen in accordance with IEC 60068-3-3 as follows:
• classification: criterion 0 (see 4.3 of IEC 60068-3-3:1991);
• performance level II (see 7.1 of IEC 60068-3-3:1991; a starting frequency of 2 Hz is
acceptable).
5 Characteristics of switches
5.1 General
This clause defines the minimum performance characteristics that the electric switches used
in these accessories are expected to have, in accordance with IEC 60947-5-1. Switches
containing mercury are not allowed.
5.2 Dielectric strength (in accordance with IEC 60255-27)
The minimum dielectric withstand strength is given in the following Table 1 and Table 2.

– 12 – IEC 60076-22-1:2019 © IEC 2019
Table 1 – Dielectric strength of switches – Power frequency
Short duration power frequency withstand voltage

1 min kV (RMS)
Between circuits and earth 2
Between contacts in open position 1

Table 2 – Dielectric strength of switches – Impulse
Lightning impulse withstand voltage

kV (peak)
Between circuits and earth 4
Between contacts in open position 3

6 General requirements for routine and type test
Tests shall be carried out at an ambient temperature between 10 °C and 40 °C, unless
otherwise specified.
All measuring instruments used for the tests shall have traceable accuracy and be subject to
periodic calibration, according to the rules given in a system like ISO 9001 or similar.
7 Protective devices
7.1 Gas and liquid actuated relay (Buchholz relay)
7.1.1 Additional service conditions
7.1.1.1 Maximum inclination
The relay is intended to function in a horizontal position; a positive inclination of up to 5° to
the horizontal axis is admissible in the direction towards the conservator. A tilt of max 5° on
either side of the vertical is admissible.
Other values may be agreed between the purchaser and the supplier.
7.1.1.2 Operating pressure
The relay shall be designed for a continuous internal pressure of 50 kPa over ambient.
7.1.1.3 Sensitivity of the relay switches to magnetic fields
The relay shall be able to withstand a DC magnetic field of up to 25 mT, in any direction and
any polarity, without unintentional operations.
7.1.2 Mechanical requirements
7.1.2.1 Nameplate
The nameplate shall contain the following information:
• name or logo of the supplier;
• country and manufacturing location;
• number of this standard;
• device manufacturer's identification;
• manufacturer’s serial number;
• connection diagram (incorporated on the nameplate or included in the terminal box);
• seismic withstand class, if applicable.
The device manufacturer’s identification shall allow identification of the device characteristics
from the mounting, operating and maintenance manual supplied by the supplier.
7.1.2.2 Terminal box
A terminal box shall be provided to connect the switches of the device; it shall include also
one protective conductor or earth terminal. The number and marking of the terminals shall
comply with the connection diagram.
The terminals shall be designed to accept cables having a cross-sectional area of between
2 2
1,5 mm to 4 mm .
A minimum of two threaded holes for cable glands M25 × 1,5 shall be provided; one shall be
closed by a weather-resistant plug, the other being protected for transport and storage. Other
thread dimensions are subject to agreement between the supplier and the purchaser.
Cable glands are supplied on demand.
7.1.2.3 Testing facility
The relay shall be provided with a device to functionally check the operation and sequence of
the switches. The mechanical test device shall differentiate between the alarm and trip
contact.
7.1.2.4 Gas and liquid sampling facility
The relay shall be fitted with a gas release and sampling petcock.
A facility shall be provided for the connection of the gas and liquid sampling device at man’s
height.
7.1.2.5 Draining device
A draining device shall be provided.
If required, a provision shall be provided for draining at man height.
7.1.2.6 Inspection windows
The relay shall be fitted with at least two scaled inspection windows for the visual check of the
presence of gas from both sides. On request, the windows are provided with protection covers.
7.1.2.7 Mounting arrangement
An arrow on the relay shall indicate the liquid flow direction towards the conservator.
7.1.2.8 General overall dimensions
Table 3 and Table 4 are to be read with Figure 1 and Figure 2.

– 14 – IEC 60076-22-1:2019 © IEC 2019
Table 3 – Preferred dimensions of relay body in mm
Nominal L
a
A B C D
b
diameter E
max. max. max. min.
Short type Long type
DN
c
25 205 75 275 300 200 240 190
50 205 90 275 300 195 240 220
80 220 100 275 400 195 240 220
100 220 110 275 400 220 - -
a
Minimum clearance to remove the mechanism from the body of the relay.
b
Minimum clearance for mounting and access to the relay.
c
For nominal diameter (DN), 25 mm thread connections of G1 ½ A (ISO 228-1) are allowed with L = 185 mm
(see Figure 2).
Table 4 – Flange dimensions in mm
Nominal Number of bolt holes
d5
diameter
d1 d2 d3 d4
max.
Short type Long type
DN
25 25 115 85 14 4 4 16
50 50 165 125 18 4 4 18
80 80 200 160 18 8 4 18
100 100 220 180 18 8 - 18
E E
C
d4
d5 d1
d3
L
d2
IEC
Figure 1 – DN 25 to 100 with circular flanges
D
B A
E E
C
L
G1 1/2A
IEC
Figure 2 – DN 25 with threaded connections
7.1.2.9 Alternative overall dimensions
In some countries, alternative dimensions as indicated in Table 5 and Table 6 may be agreed
between the purchaser and the supplier.
The dimensions refer to Figure 1 above or Figure 3 below for the relay with rectangular
flanges.
Table 5 – Alternative dimensions of relay in mm
Nominal
a
A B C D1
b
diameter L E
max. max. max. min.
DN
25 180 140 320 200 127 315
50 170 150 320 200 184 315
80 170 150 320 200 184 315
a
Minimum clearance for access of petcocks.
b
Minimum clearance for mounting and access to the relay.

Table 6 – Alternative flange dimensions of the relay in mm
Nominal Number
d5
diameter d1 d2 d3 d4 of
max.
DN bolt holes
25 25,4 76 72 M10 4 N/A
50 50,8 139 110 11,1 6 14
80 76,2 160 130 11,1 6 14
Dimensions for Buchholz relay DN 80 with rectangular flanges are given in Figure 3.
D
B A
– 16 – IEC 60076-22-1:2019 © IEC 2019
ø18
IEC
Figure 3 – Gas and liquid operated relay with rectangular flanges
for DN 80 mm
7.1.3 Performance requirements
7.1.3.1 Switch type
Switches shall be potential free. Unless otherwise specified, the switches shall be open
("normally open") under normal operating conditions (normal operating conditions are when
the relay is filled with oil and there is no fault on the protected equipment). On request, the
switches can be also of the normally closed or changeover type.
7.1.3.2 Switch performance
Switches shall have a minimum rated operational current of 2 A RMS for normally open
contacts and 1 A RMS for changeover contacts and short time current of 10 A RMS for 30 ms.
Making and breaking capacity shall comply with the requirements of Table 7. Typically,
magnetically operated Reed type switches are provided.
Table 7 – Making and breaking capacity – Buchholz relay
NO Switches Changeover switches
Voltage
Making capacity Breaking capacity Making capacity Breaking capacity
24 V DC. to
250 W L/R < 40 ms 30 W L/R < 40 ms 130 W L/R < 40 ms 30 W L/R < 40 ms
220 V DC
230 V AC 400 VA 40 VA 250 VA 40 VA
cos ϕ > 0,5 cos ϕ > 0,5 cos ϕ > 0,5 cos ϕ > 0,5

Other values may be agreed between the purchaser and the supplier.
The minimum switch life shall be 1 000 operations.
The switch shall also be able to make a low current down to 50 mA for any value of voltage
defined in Table 7.
7.1.3.3 Switches setup
This device shall be provided with at least one switch for gas accumulation and one switch for
liquid surge and liquid loss.
The gas accumulation switch shall operate due to a gas accumulation volume between
3 3
100 cm and 400 cm . The gas accumulation switch shall operate before any gas escapes
into the pipework toward the conservator.
The manufacturer shall state for every type of Buchholz relay the range of gas accumulation
for which the gas accumulation switch operates.
The gas accumulation switch will also react to a liquid leakage introducing air in the relay
chamber.
The liquid surge switch shall operate at a steady liquid flow as indicated in Table 8.
This operation shall not be adversely affected when the alarm switch has already closed and
gas is escaping freely.
The liquid loss switch shall operate before the pipe is empty.
The liquid surge and liquid loss switches are usually the same, unless a different setting is
agreed between the purchaser and the manufacturer.
Upon special request, the liquid surge switch can be provided with a mechanism, which holds
it in position after a liquid flow operation until it is manually reset.
Table 8 – Steady liquid flow for relay operation
Liquid pipe connection internal diameter Steady liquid flow for relay operation
Tolerance %
[mm] [m/s]
25 1 ±15
50 1 ±15
80 1 or 1,5 or 2 ±15
100 1,5 or 2 ±15
Other values may be agreed between the purchaser and the supplier.
The switches shall not operate in case of liquid flow from the conservator to the tan
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