Transformer stop power operation, the neutral point must be grounded
Transformer stop power operation, the neutral point must be grounded. Because China's 110KV transformer is mostly neutral grounding system, the main transformer neutral grounding switch, in order to protect the sensitivity of the protection device, the main transformer neutral grounding switch in the operation often open; but in the main transformer operation , In order to prevent the operation of the over-voltage "affect" the main transformer insulation, it must be closed ground switch.
For the side of the power supply of the power transformer, when the switch is not full-phase pull, at the time, if the neutral point is not grounded the following hazards:
(1). Transformer power supply side of the neutral point to ground voltage rise up to the maximum phase voltage, which may damage the transformer insulation;
(2) Transformer between the high and low voltage coils, this capacitor will cause high voltage to the low voltage "overvoltage";
A measure taken to prevent overvoltage damage from being turned off the transformer. For the high voltage side of the power supply of the power transformer, when the circuit breaker is not full phase pull, if the neutral point is not grounded the following hazards: 1 transformer power side of the neutral point to ground voltage up to phase voltage, which may be damaged Transformer Insulation 2 Transformer between the high and low voltage winding capacitor, this capacitor will cause the high voltage to the low voltage "overvoltage" 3 When the transformer between the high and low voltage winding capacitive coupling, the low side voltage will reach the resonance conditions, may There is resonance over voltage, damage insulation.
(3). When the transformer between the high and low voltage coil capacitive coupling, the low side of the voltage will reach the resonance conditions, there may be resonance over voltage, damage insulation.
For the low voltage side of the power supply transformer:
(1). Since the low side of the power supply, in the system into the system before the high side of the transformer single-phase ground, if the neutral point is not grounded, the neutral point of ground voltage will rise to phase voltage, which may damage the transformer insulation;
(2). In the case of non-full phase incorporation, when the phase of the generator is connected with the system, the neutral point of the transformer is not grounded due to the frequency of the generator and the system. Will be twice the phase voltage, the other phase (ie, unphaseed) voltage up to 2.73 times the phase voltage, will cause insulation damage accident.
