The sound of the transformer is abnormal As soon as the transformer is connected to the power supply, there will be a buzzing sound, which is mainly due to the effect of high-voltage magnetic flux. During normal operation, the sound of the transformer is uniform. When there are other noises, you should carefully find the cause and deal with it.
2). The transformer has noise
There may be vibrations caused by loose parts on the transformer. If the sound of the transformer is significantly increased, and the current and voltage are not abnormal, it may be caused by the loosening of the internal clamp or the screw pressing the iron core, which increases the vibration of the silicon steel sheet. Treatment method: If it does not affect the operation of the transformer, it can be temporarily not dealt with, make records, strengthen monitoring, report and dispatch, and apply for power outage inspection and processing by relevant leaders.
3) Transformer has discharge sound The transformer has a "crackling" discharge sound. If you see blue corona or sparks near the transformer bushing at night or in rainy weather, it means that the porcelain parts are seriously dirty or the equipment line cards are in poor contact. If the transformer is internally discharged, it is the electrostatic discharge of the ungrounded components or the inter-turn discharge of the coil, or the discharge due to the poor contact of the tap changer. Solution: At this time, the dispatcher and relevant leaders should be reported to apply for power failure inspection of the transformer.
4) Transformer has popping sound Indicates that the internal or surface insulation of the transformer is broken down, and the transformer should be stopped immediately for inspection.
5) Transformer has the sound of water boiling If the transformer has the sound of water boiling, and the temperature changes sharply and the oil level rises, it should be judged that the transformer winding is short-circuited or the tap changer is in poor contact caused by serious overheating, and the transformer should be stopped immediately for inspection.
The upper oil temperature is high Usually, the oil temperature of the upper layer of the transformer should be detected during operation, and the temperature of the windings should be controlled by supervising the oil temperature of the upper layer to prevent the insulation level from dropping and aging. Under normal load and normal cooling conditions, the transformer oil temperature is more than 10°C higher than usual or the transformer load remains unchanged, and the oil temperature continues to rise. Fault (such as iron core fire and short circuit between winding turns, etc.). At this time, the transformer should be stopped immediately to prevent the transformer accident from expanding.
The oil color is abnormal Normally, the transformer oil should be bright yellow and transparent. When it is found that the color of the oil in the oil level gauge changes during operation, you should contact to take oil samples for laboratory analysis. If the color of the transformer oil suddenly deteriorates during operation, and there is carbon in the oil and other abnormal phenomena, the power should be cut off immediately for inspection and treatment.
The oil level is abnormal The oil pillow of the transformer is equipped with an oil level gauge, which generally shows three oil level lines when the temperature is -30°C, +20°C, and +40°C. According to these three marking lines, it can be judged whether it is necessary to refuel or drain. High oil level: When the oil level of the running transformer is too high or oil overflows from the oil pillow, you should first check whether the load and temperature of the transformer are normal. False oil level caused by clogging of the standard pipe. At this time, with the consent of the dispatcher on duty, the gas (heavy gas) protection should be changed to the signal, and then the respirator should be cleared for processing. If the oil pillow overflows due to the high ambient temperature, it should be drained. Low oil level: If the oil level of the transformer is too low, the gas (light gas) protection will act; when there is a serious lack of oil, the iron core and windings will be exposed to the air, which is easy to be damp and may cause insulation breakdown. Therefore, the vacuum oil injection method should be used to Refueling transformers in operation. If the oil level drops rapidly due to a large amount of oil leakage, below the gas relay or continues to drop, the transformer should be stopped immediately.
When the transformer in overload operation is overloaded, the ammeter indication may exceed the stable value, the signal, the alarm bell action, etc. Operators should handle it according to the following principles:
①Check whether the current on each side exceeds the specified value, and report to the duty officer on duty.
②Check whether the oil level and oil temperature of the transformer are normal, and put all the coolers into operation at the same time.
③ Adjust the operation mode in time. If there is a spare transformer, it should be put into operation.
④Contact scheduling and adjust the load distribution in time.
⑤ In the case of normal overload, the allowable operating time can be determined according to the multiple of the overload, and the monitoring of oil level and oil temperature shall be strengthened, and the allowable value shall not be exceeded. If the time is exceeded, the load should be reduced immediately.
⑥ In case of accidental overload, the allowable multiple and time of overload shall be implemented according to the regulations of the manufacturer. If the overload multiple and time exceeds the allowable value, the compliance of the transformer should also be reduced according to regulations.
⑦ Conduct a comprehensive inspection of the transformer and its related systems. If any abnormality is found, it should be reported and dealt with
Cooling system failure When the transformer cooling system (referring to the submersible oil pump, cooling water system) is faulty, and the transformer sends out the chiller standby switch and the cooler full stop signal, the following measures should be taken: 1. Immediately check whether the standby cooler has been put into operation. 2. Immediately check the cause of the power outage and restore the normal operation of the cooling device as soon as possible. 3. Strengthen the monitoring of the oil temperature and oil level of the upper layer of the transformer, especially during the full stop time of the cooling device. 4. If the cooling system cannot be restored for a while, an application should be made to reduce the load or apply for the transformer to be withdrawn from operation to prevent the transformer from running for more than the specified non-cooling time, resulting in overheating and damage.
Gas protection action Reasons for gas shielding action may be:
There is a slight fault in the transformer, which produces weak gas; 2. Air intrudes into the transformer; 3. The oil level drops; After the gas protection signal appears, the operator should immediately conduct an external inspection of the transformer. First, check the oil level and oil color in the oil pillow, whether there is gas, gas volume and color in the gas relay, and then check whether there is oil leakage in the transformer body and the forced oil circulation system. At the same time, look at changes in transformer load, temperature and sound, etc. After external inspection, if no abnormal phenomenon is found, the gas gas of the transformer should be absorbed to find out the nature of the gas, and if necessary, the oil sample should be taken for testing to jointly determine the nature of the fault.
Parts and causes that are prone to heat during operation
Poor contact of the tap changer and poor contact will increase the contact resistance, increase the consumption, and cause severe heat generation. This is especially likely to happen after a tap change and when the transformer is overloaded.
Winding inter-turn short circuit Inter-turn short circuit is the insulation damage between adjacent turns. This will create a closed short-circuit loop and reduce the number of winding turns for that phase. There is a short-circuit current induced by the alternating magnetic flux in the short-circuit loop, which will generate high heat and may cause the transformer to burn out.
There is a short circuit between the iron core silicon steel sheets. Due to external force damage or insulation aging, the paint insulation between the silicon steel sheets is damaged, which will increase the eddy current, cause local overheating, and even melt in severe cases. This is the so-called iron core fire.
Poor contact of other parts causes local overheating.
Handling advice: closely monitor the temperature changes of the overheated parts to ensure safe operation, analyze the causes of overheating, contact scheduling, and deal with power outages.
