Common faults of transformers and fault analysis
1 Common faults of transformer During power transmission and operation, common faults and abnormal phenomena are:
(1) When the transformer is in power transmission or trial transmission after shutdown, it is often found that the voltage is abnormal, such as two phases high and one phase low or the indication is zero; some new transformers have high three-phase voltages, causing some Electric equipment burned out due to excessive voltage;
(2) The high-voltage fuse is blown and cannot be powered on;
(3) The transformer cannot be powered on after the thunderstorm;
(4) The sound of the transformer is abnormal, such as "creaking" or "cracking" noise; during operation, it makes a "squeak wow wow wow" sound, etc.; (5) The high voltage terminal is burned out, and the high voltage bushing Signs of serious damage and flashover;
(6) Under normal cooling conditions, the temperature of the transformer is abnormal and continues to rise;
(7) The color of the oil changes too much, and there is charcoal in the oil;
(8) The transformer roars, fuel is injected from the safety air passage, the oil conservator, the fuel tank and the heat pipe are deformed, oil leaks, oil seepage, etc.
2 Transformer fault analysis, judge the fault from the sound of the transformer
(1) The sound when the phase is missing
When the transformer loses phase, if the second phase fails, the second phase will still be silent, and the third phase will have a sound; if the third phase fails, the sound will not change, the same as the second phase. There are roughly three reasons for the lack of phase: ① the power supply lacks one phase; ② the transformer high-voltage fuse blows one phase; ③ the transformer is not carefully transported and the high-voltage lead is thin, causing vibration to break (but not connecting the shell).
(2) The voltage regulating tap switch is not in place or the contact is poor. When the transformer is put into operation, if the tap switch is not in place, a loud "chirp" sound will be emitted, which may cause the high voltage fuse to blow; if the tap switch is in poor contact , It will produce a slight "squeaking" spark discharge sound, once the load increases, it may burn the tap switch contacts. In this case, the power supply must be cut off in time for repair.
(3) Falling into foreign objects and loosening of the threaded screw
When the through-core screw of the transformer clamping iron core is loose, there are nut parts left on the iron core or small metal objects fall into the transformer, the transformer will make a "ding-dang-dang" knocking sound or "whoop...whee..." And the "squeaky squeaky" sound like a magnet sucking a small gasket, while the voltage, current and temperature of the transformer are normal. Such situations generally do not affect the normal operation of the transformer, and can be processed when the power is out.
(4) Dirty and cracked transformer high-voltage bushings
When the transformer's high-voltage bushing is dirty and the enamel on the surface falls off or cracks, flashover occurs on the surface, a "hissing" or "chicking" sound is heard, and sparks can be seen at night.
(5) The core grounding of the transformer is broken
When the core of the transformer is disconnected from the ground, the transformer will produce a slight discharge sound of "beep and beep".
(6) Internal discharge
When you hear the "crack" sound of iron striking when power is on, it is the discharge sound of the conductive lead through the air to the transformer housing; if you hear the dull "crack" sound through the liquid, the conductor faces the housing through the transformer oil The sound of discharge. If the insulation distance is not enough, you should check the power outage, strengthen the insulation or add insulation partitions.
(7) The external circuit is disconnected or short-circuited
When the line is disconnected at the wire connection or T connection, when the wind is blowing, the connection will be disconnected, and the arc or spark will occur when contacting, then the transformer will emit a "chirp" sound like a frog; when the low voltage When the line is grounded or there is a short-circuit accident, the transformer will make a "boom" sound; if the short-circuit point is close, the transformer will roar like a tiger.
(8) Transformer overload
When the transformer is seriously overloaded, it will emit a low "hum" sound like a heavy-duty airplane.
(9) The voltage is too high
When the power supply voltage is too high, the transformer will be over-excited and the noise will increase and be sharp.
(10) The winding is short-circuited
When the transformer winding is burnt out due to a short circuit between layers or between turns, the transformer will emit a "grumbling" boiling water sound.
There are many factors for the abnormal sound of the transformer, and the fault location is also different. Only by continuously accumulating experience can we make an accurate judgment.