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Transformer Faults and Handling Methods

1. Abnormal Temperature Rise of the Transformer

When the transformer's oil temperature or coil temperature exceeds the allowable value during operation, the following steps should be taken to identify the cause and take measures to reduce the temperature:

(1) Check the oil temperature and coil temperature that should be present under the load and cooling medium temperature.

(2) Check if the temperature displayed on the CRT of the transformer is normal.

(3) Check if the cooling device is functioning properly, and whether the standby cooler is engaged. If not engaged, it should be manually started immediately.

(4) Adjust the output, load, and operation mode to ensure that the transformer temperature does not exceed the specified value.

After inspection, if the cooling device and temperature measuring device are normal, adjusting the output, load, and operation mode remains ineffective. There is still a rising trend in the transformer oil temperature or coil temperature, or if the oil temperature is 10°C higher than the normal temperature under the same load and cooling temperature, it should be immediately reported to the relevant authorities, and the operation of the transformer should be stopped, and relevant maintenance personnel should be notified to participate in the handling process.

2. Abnormal Oil Level of the Transformer

Measures should be taken when the transformer oil level significantly decreases:

(1) If it is caused by long-term minor oil leakage, oil replenishment should be carried out, and maintenance should be arranged according to the leakage situation.

(2) If the oil level decreases significantly due to low oil temperature, adjust the operation mode of the cooling device appropriately.

(3) During refueling, withdraw the heavy gas protection and switch from "trip" to "signal". When refueling is completed, restore heavy gas protection to "trip".

3. Interruption of Oil Flow

(1) Check if the oil flow indicator is functioning properly.

(2) Check if the power supply of the cooling device is interrupted, if the standby power supply is automatically engaged and if the oil pump is stopped. If the cooling device malfunctions, adjust the operation mode accordingly at that time. It may be necessary to operate with load according to the temperature rise, but it should not exceed the allowed capacity under the cooling conditions specified on the transformer nameplate.

4. Action of Pressure Release Device

(1) Check if a large amount of oil is sprayed after the pressure relief plate is damaged.

(2) Check if the transformer oil sprayed catches fire, if so, follow the transformer fire handling procedure.

(3) When the pressure release device is activated due to internal faults of the transformer, handle it according to the accident procedure.

(4) Check if the pressure release device can reset automatically.

5. Handling of Gas Relay Tripping or Signaling

(1) Quickly inspect the external condition of the transformer for any equipment damage.

(2) Have maintenance personnel conduct an internal inspection of the transformer for confirmation.

(3) Check if the gas relay tripped due to external impact.

(4) Check if there is gas inside the gas relay, and determine its chemical composition based on the gas quantity, color, and gas chromatography analysis.

(5) Check and record the indication value of the hydrogen detection device.

(6) When a gas signal is emitted, determine the cause, conduct gas analysis, and decide whether to continue operation. If the gas signal frequency gradually decreases during normal operation, report to the higher authorities and prepare for tripping by the duty personnel.

(7) If it is a false gas tripping, the transformer should be put into operation as soon as possible."

6. Handling of Transformer Fire

Firstly, all power switches and disconnectors should be turned off, and the cooler should be stopped. If the transformer oil catches fire on the top cover, immediately open the transformer emergency oil drain valve, and start the transformer water spray fire extinguishing device to cool the oil and prevent combustion. If a fire occurs inside the transformer due to internal faults, oil drainage should not be carried out to prevent transformer explosion. If the transformer casing ruptures and catches fire, all oil inside the transformer must be drained into oil storage pits or tanks.

7. Handling of Cooling Power Supply Failure of the Transformer

Firstly, check if the standby power supply can be engaged. If not, quickly reduce the transformer load to bring it down to the load specified on the transformer nameplate for natural cooling, and closely monitor the coil temperature to ensure it does not exceed the limit. Immediately notify maintenance personnel for handling.

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