Transformer light gas alarm
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After the transformer was shut down normally, it was left idle for half a year. When it was brought back into operation, a low gas alarm was triggered, which prevented the switchgear from closing. The transformer uses a float-type level gauge; the oil level should be fine, as it is mostly in the blue area, with only a small portion in the red area. There is also no sign of oil leakage. What could be the cause of this situation? How to check and rule it out? Could the experts please explain this? Thank you so much! !
A gas relay is used for the protection of transformers; light gas triggers a signal alarm, while heavy gas causes the transformer to trip. Under normal circumstances, the reasons for a light gas alarm in a transformer include 1: air entering the transformer due to leaks in the refueling or cooling system ； 2. The oil level drops below the light gas float of the gas relay due to a decrease in temperature or oil leakage from the unit ； 3. The transformer has latent faults that generate a small amount of gas ； 4. Gas relay or secondary circuit failure ； 5. A transverse fault short circuit occurs. Common treatment methods: 1. Discontinue the audio signal, while checking whether the oil temperature, oil level, sound levels, as well as voltage and current of the transformer are normal ； 2. Collect the gas from the relay for analysis; if the collected gas is air, the duty personnel can release the gas inside the relay, allowing the transformer to continue operating ； If it is a combustible gas and the operation occurs frequently, the load should be reduced or the operation stopped outright to await handling ； 3. If there is no gas and the transformer is normal, it may be that there is a fault in the secondary circuit; the duty personnel should change the setting of the heavy gas relay from tripping to signaling, and immediately inspect the secondary circuit. Level. ...
In the situation I encountered, the transformer had not been in use for half a year; it was working normally before it was taken out of service. After it was restarted, a low gas alarm was triggered, which prevented the circuit breaker from being closed. It was also impossible to see the oil level through the glass window of the gas relay, although the tubular oil level gauge beside it indicated that the oil level was normal. Is it possible that there is air inside the gas relay? It’s been half a year; the likelihood of there still being combustible gases is probably low.
(1) There is gas inside the gas relay. Reasons and analysis: Transformer oil serves to provide insulation and facilitate heat dissipation. Even when the transformer is not in use for half a year, gas can still be generated within the oil, which accumulates inside the gas relay. The vent valve of the gas relay can be opened to release this gas; if there is still concern, the transformer oil should be sent for analysis. Only after it is confirmed to be of satisfactory quality can the transformer be put back into operation. Based on the phenomenon you described, it can’t be air. (2) If there is no gas inside the gas relay and a fault exists in the secondary circuit, then that secondary circuit fault is resolved. No problem, the transformer is now in operation.
This is an oil-free pillow transformer; the oil level indicator shows half red and half blue. After releasing the gas from the gas relay, is it still necessary to fill the gas relay with oil?