Gas relay

The gas relay can be used both on open-type transformers and hermetically sealed transformers. It responds to oil loss and gas accumulations that can occur as a result of faults in the transformer.

Mode of operation

Due to its specific design, the gas relay is suitable especially for hermetically sealed transformers without nitrogen cushion. Mounted on the transformer tank it can be filled completely through an oil filler so that reliable monitoring of the oil level is ensured.
An integral pressure switch (optional) and a temperature sensor offer significant additional monitoring options for the transformer.

With open-type transformers with conservator the gas relay, on the one hand, serves as an air cell failure relay monitoring the hydro-type compensator (rubber sack) in the conservator and, on the other hand, the gas relay can also be used on the transformer cover.

During normal operation the gas relay must be filled completely with oil. Due to its boyant force the float is in the upper limit position.
As soon as gases are generated, these are collected in the gas relay and cause the float to descend. This actuates the switching contact (magnetic contact tube) and trips a signal.

Gas collection is indicated by the sightglass.

Technical Data


Temperature range:

  • Ambient temperature

- 40 °C to +55 °C
- 40 °F to +131 °F

Climatic test acc. to
DIN EN 60068-2-78: 2002-09

Others on request

Temperature range:

  • Operating range
    • Temperature of insulating liquid

- 40 °C to +115 °C
- 40 °F to +239 °F
Up to +135 °C design 21 required

Temperature range:

  • Operating range
    • Viscosity of insulating liquid

1 mm²/s to 1100 mm²/s
Insulating liquidMineral oilOthers on request
Resistance to vibrationVibration: 2-200 Hz, 1 g
Shock: 25 g, 6 ms
Class 4M6 acc. to
DIN EN 60721-3-4
Resistance to pressure0,25 MPa 
Resistance to vacuum< 2,5 kPa 
Insensitivity to magnetic fields25 mTStatic magnetic field of any
direction and polarity
Response of switching system to:
  • Gas accumulation

200 cm³ / 300 cm³ / 400 cm³
Tolerance ± 15%

Others on request
Cable glandM20x1,5; M25x1,5Others on request
IP codeIP 56Others on request
Casing colourTwo-component texture paintOn polyurethane basis


Cable gland *

M20x1.5: 1 Cable gland and 1 dummy plug1
M25x1.5: 1 Cable gland and 1 dummy plug2
M20x1.5: 2 Cable glands3
M20x1.5: 2 Cable glands and 1 dummy plug (added loosely)3b
M25x1,5: 2 Cable glands4
M25x1.5: 2 Cable glands and 1 dummy plug (added loosely)4b
M20x1.5: 1 Harting connector and 1 dummy plug5
1/2“ NPT: 1 Cable gland and 1 dummy plug6
1/2“ NPT: 2 Cable glands7
Cable gland: On customer’s request9

* Mandatory order data

Casing colour *

Casing colour RAL 9006 (white-aluminium)40
Casing colour RAL 7001 (silver-grey)41
Casing colour RAL 7012 (basalt-grey)42
Casing colour RAL 7022 (umber-grey)43
Casing colour RAL 7033 (cement-grey)44
Casing colour RAL 7038 (agate-grey)45
Casing colour RAL 7035 (light-grey)46
Casing colour RAL 7016 (anthracite-grey)47
Casing colour RAL 9002 (grey-white)48
Casing colour RAL 7032 (siliceous-grey)49

* Mandatory order data


Sealing of bleeding valve14
Metal plate15

Special designs

Climate-proof version/IP code

Climate-proof version for extreme frigid open-air conditions below - 40 °C34
Climate-proof version for Offshore36
Climate-proof version for aggressive industrial atmosphere36B
IP code 6639
IP code 6739B

Insulating liquid

Insulating liquid silicone oil20
Insulating liquid based on ester21

Switching system

Switching system with two magnet contact tubes25
Switching system with three magnet contact tubes99

Additional functions

Temperature sensor61

Pressure switch, factory-set

               Switching pressure from 20 kPa = 0,20 bar
               Switching pressure from 25 kPa = 0,25 bar
               Switching pressure from 30 kPa = 0,30 bar
               Switching pressure from 35 kPa = 0,35 bar
               Switching pressure from 40 kPa = 0,40 bar
               Switching pressure from 45 kPa = 0,45 bar
               Switching pressure from 50 kPa = 0,50 bar



Special request

Special request (on special agreement with customer)29
Bleeding valve as mini ball valveA
Large cap nut of test key, metalB
Without hinged lids for sightglassesC
With oil filler neckD

Please contact us! We are glad to advise you and help with your selection.

Otto-von-Guericke-Allee 12
39179 Barleben
Phone +49 (0) 392 03 / 79 - 0
Fax +49 (0) 392 03 / 53 30