The gas relay can be used both on open-type transformers and hermetically sealed transformers.
On open-type transformers with conservator the gas relay of type 80 can be used both as an air cell failure relay monitoring the hydro-type compensator (rubber sack) in the conservator, and as a gas relay on the cover of the transformer.
On hermetically sealed transformers without nitrogen cushion the gas relay serves to monitor potential gas collection.
For normal operation the gas relay must be filled completely with oil. Due to its boyant force the float is positioned in the upper limit position.
When due to any event gases are formed, these are collected in the gas relay causing the float to move downwards. This operates a switching contact (magnet contact tube) and produces a signal.
Gas accumulation is visible on the inspection glass.