In severe cases, the open circuit resonance of the cable can superimpose the high frequency and the fundamental frequency resonance, which can make the overvoltage amplitude reach 2.5 times of the phase voltage. It may cause the neutral point of the system to shift, the windings and wires have overvoltage, and in severe cases, it may cause insulation flashover, lightning arrester explosion, and electrical equipment damage. In some cases, the phase sequence of the load transformer may be reversed, and overvoltage may be transferred to the low-voltage side of the transformer, causing harm.
The main measures to prevent disconnection from resonant overvoltage are:
(1) Use fuses to avoid non-full-phase operation.
(2) Strengthen line inspection and maintenance to prevent the occurrence of circuit breaks.
(3) Do not hang the no-load transformer on the line for a long time.
(4) Adopt ring network or dual power supply.
(5) Add interphase capacitance on the distribution transformer side,
The principle is: The capacitor is used as an energy-absorbing element to absorb the energy in the transient process, thereby reducing the intensity of impact disturbance to suppress the occurrence of resonance. s一(o+ 3C,,) 1C., add interphase capacitance △C on the distribution transformer side to increase 8 one [Co+ 3(C U+ A0)/Ca. Thereby increasing the required capacitance value of the equivalent capacitance C and the equivalent electromotive force Eo.
(6) The use of transformers with better excitation characteristics can help reduce the probability of breakage and overvoltage.