Abnormality And Treatment Of Voltage Transformer

Common exceptions:

(1) Three-phase voltage indication is unbalanced: one phase is reduced (can be zero), the other two phases are normal, the line voltage is abnormal, or accompanied by sound and light signals, it may be that the high voltage or low voltage fuse of the transformer is blown.

(2) The neutral point is not effectively grounded, and the three-phase voltage indication is unbalanced: one phase drops (can be zero), the other two phases rise (up to line voltage) or the pointer swings, which may be a single-phase ground fault or a base If the three-phase voltage rises at the same time and exceeds the line voltage (the pointer can swing to the end), it may be frequency division or high-frequency resonance.

(3) The high-voltage fuse has been blown many times, which may be due to serious damage to the internal insulation, such as short-circuit faults between winding layers or turns.

(4) In the neutral point effective grounding system, when the busbar is switched off, the phase voltage rises and swings at a low frequency, which is generally a series resonance phenomenon; if there is no operation, the phase voltage suddenly rises or falls abnormally, it may be The internal insulation of the transformer is damaged, such as short-circuit faults in the insulation support winding, between winding layers or between turns.

(5) The neutral point is effectively grounded. When the voltage transformer is put into operation, the indication of the voltmeter is unstable. It may be that the grounding contact of the N (X) end of the high-voltage winding is poor.

(6) Disconnection of the voltage transformer circuit.

Approach:

1. According to the relevant regulations of relay protection and automatic devices, exit the relevant protection to prevent malfunction.

2. Check whether the high and low voltage fuses and automatic air switches are normal. If the fuse is blown, the cause should be found out and replaced immediately. When it is blown again, it should be handled with care.

3. Check whether all connectors of the voltage circuit are loose or disconnected, and whether the switching circuit has poor contact.