Low-frequency oscillation suppression method and device for electromagnetic voltage transformer

Abstract

The invention discloses a low-frequency oscillation suppression method and device for an electromagnetic voltage transformer. The method comprises the steps of detecting the voltage of a neutral point of the electromagnetic voltage transformer in real time, and transmitting a disconnection instruction to a self-recovery switch when the voltage is greater than or equal to a first preset threshold value, when the voltage is smaller than or equal to a second preset threshold value, sending a closing instruction to the self-recovery switch. The self-recovery switch is connected in parallel with the current-limiting resistor, and then is connected in series between the neutral point of the electromagnetic voltage transformer and the ground wire. According to the low-frequency oscillation suppression method for an electromagnetic voltage transformer provided by the invention, after the system generates low-frequency oscillation or ferromagnetic resonance, the ferromagnetic resonance and the low-frequency oscillation can be effectively suppressed under the condition that the operation of the system is not influenced, the problem of burning loss of an inductor body and a fuse wire is avoided, and the maintenance cost is reduced.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a method and device for suppressing low-frequency oscillation of an electromagnetic voltage transformer. Background technique [0002] In the medium voltage distribution network, due to the nonlinear characteristics of the electromagnetic voltage transformer, the external disturbance is easy to excite the ferromagnetic resonance. As the scale of the cable system increases, the capacitance of the system to ground increases significantly, and it is difficult to form a resonance condition with the system inductance; when the single-phase ground fault is removed, the charge accumulated in the capacitance of the healthy phase line discharges to form a nonlinear low-frequency oscillation, resulting in inductance melting. Faults such as wire fusing and body burning occur frequently. [0003] At present, among the methods used to solve the problem of primary fuse blown and bod...

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Problems solved by technology

As the scale of the cable system increases, the capacitance of the system to ground increases significantly, and it is difficult to form a resonance condition with the system inductance; when the single-phase ground fault is removed, the charge accumulated in the capacitance of the healthy phase line discharges to form a nonlinear low-frequency oscillation, resulting in inductance melting. Frequent faults such as wire fusing and body burning

[0003] At present, among the methods used to solve the problems of the primary fuse blown and body burnout of distribution network voltage transformers, the most common methods include three: the first is The central point of the primary side of the electromagnetic voltage transformer is grounded through the primary resonance eliminator (silicon carbide), but this method easily causes the sampling value of the transformer to shift, which affects the accuracy of fault identification; the second is the 4PT method, namely The accuracy of the zero-sequence measurement is solved by the compensation coil, but this method takes up a lot of space, high cost, and the service life of the device is short; ) grounding, but the disadvantage of this method is that when the PTC is disconnected, it takes more than a minute to release heat, and during this period of time, the electromagnetic voltage transformer will fail to measure due to the suspension of its primary side neutral point, especially The zero-sequence measurement fails completely, which often causes the protective device to refuse to operate when frequent arcs are grounded, resulting in more serious accidents

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