High voltage transformer neutral point grounding system

Abstract

The invention provides a grounding system for a neutral point in a high-voltage transformer; the system comprises a series resonant device connected between the neutral point of the high-voltage transformer and a ground the series resonant device is in power frequency resonance state with zero series impedance when a power system runs normally, good power frequency grounding of the neutral point of the transformer, and a capacitive element in the system can be free of transformer biasing due to direct-current components in the system; when the system experiences a grounding fault, a nonlinear inductor is saturated, a resonant loop is detuned, the capacitor is capable of effectively limiting faulty short-circuit current so as to ensure normal running of the breaker; meanwhile, the nonlinear inductor may limit the rise rate of faulty current and avoid transient current causing impact damage to the capacitor.

Description

technical field [0001] The invention relates to a power grid protection system, in particular to a high-voltage transformer neutral point grounding system. Background technique [0002] The selection of the neutral point grounding method of high-voltage transformers in power systems is a comprehensive problem, which is closely related to system power supply reliability, insulation coordination, relay protection, communication interference, and electrical safety. [0003] The purpose of neutral point grounding is to limit the single-phase grounding short-circuit current, reduce the impact of external short-circuit faults on the transformer, thereby reducing the damage of fault current to equipment, reducing power failure losses to users, and ensuring the reliability and safety of system operation . With the rapid development of the UHV DC transmission system, the DC current flowing into the earth from the grounding pole of the DC system will have an impact on the power equip...

AI Technical Summary

Problems solved by technology

Excessive short-circuit current will not only make the selection of circuit breakers difficult, but also affect the stable and safe operation of the power grid

[0004] At present, for high-voltage transformers, the neutral point grounding methods mainly include the neutral point grounding through a small resistance, the neutral point grounding through a small reactance, the neutral point direct grounding, and capacitor DC blocking. Suppression of DC bias and limitation of short-circuit fault current: For the neutral point grounding method through a small resistance, when the system has a DC component, the transformer bias cannot be completely limited; for the neutral point grounding method through a small reactance, due to the reactance It is an inductive element itself, and forms a resonant circuit with the line-to-ground capacitance. Under certain conditions, resonant overvoltage will occur, and at the same time, the transformer bias cannot be avoided; for the neutral point direct grounding method, when there is a DC component in the system, the transformer bias cannot It is completely limited, and at the same time, it cannot limit the excessive short-circuit current; for the neutral point capacitor DC blocking method, when the single-phase ground fault current is large, the transient current impact may damage the capacitor

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