Disconnection resonance In severe cases, the superposition of high frequency and fundamental frequency resonance can make the overvoltage amplitude reach 2.5 times the phase voltage [P], which may cause the neutral point of the system to shift, and the windings and wires may experience overvoltage. Insulation flashover, lightning arrester explosion, electrical equipment damage. In some cases, the phase sequence of the load transformer may be reversed, and overvoltage may be transmitted to the low-voltage side of the transformer, causing harm.
The main measures to prevent disconnection from resonant overvoltage are:
(1) No fuse is used to avoid non-full-phase operation.
(2) Strengthen the inspection and maintenance of the line to prevent the occurrence of disconnection.
(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 use of capacitors as energy-absorbing elements 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., additional phase-to-phase capacitance △C on the distribution transformer side , Increase 8一[Co+ 3(C U+ A0)/Ca, thereby increasing the equivalent capacitance C and the equivalent electromotive force Eo. The required capacitance value can be calculated according to the method in [6]. (6) Using excitation characteristics A better transformer helps to reduce the chance of breakage and overvoltage.
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