Method and system for measuring ground insulation parameters of neutral point ungrounded power distribution network by adopting star-shaped capacitor

Abstract

The invention discloses a method and system for measuring ground insulation parameters of a neutral point ungrounded power distribution network by adopting a star-shaped capacitor. The method comprises the following steps: injecting a specific frequency current signal into a neutral point of the star-shaped capacitor of a neutral point ungrounded power distribution network; measuring the returnedfrequency voltage signal by a no-load zero-sequence voltage transformer on the open triangle side; and calculating ground insulation parameters, namely ground capacitance and ground leakage conductance, of the neutral point ungrounded power distribution network according to the voltage signal and the current signal. According to the invention, online measurement of ground insulation parameters canbe realized, primary side wiring of the power distribution network does not need to be changed during measurement, normal operation of the power distribution network is not influenced, the influenceof impedance in the voltage transformer and harmonic elimination resistance of the power distribution network can be eliminated, and the method has the characteristics of safe, simple and convenient measurement, economy and high precision.

Description

technical field [0001] The invention belongs to the field of distribution network measurement, and in particular relates to a method and system for measuring ground-to-ground insulation parameters of a neutral-point ungrounded distribution network using a star-shaped capacitor. Background technique [0002] When a single-phase ground fault occurs in the neutral point ungrounded distribution network, the grounding arc can be extinguished by itself when the capacitance current of the distribution network to the ground is not large. The grid-to-ground capacitive current gradually increases. When the neutral point is not grounded, the arc is difficult to extinguish when there is a ground fault in the distribution network, and it is easy to develop into a phase-to-phase fault, which endangers the safety of people and equipment. It is necessary to install an arc suppression coil to compensate for the capacitive current and leakage. current. Real-time measurement of the insulation...

AI Technical Summary

Problems solved by technology

However, the connection of the harmonic elimination resistor leads to a change in the topology of the equivalent circuit of the ground parameter measurement. The existing measurement methods do not consider the influence of the harmonic elimination resistor on the measurement of the insulation parameter, and the measurement error is large when applied.

The current single-frequency measurement method uses approximately equal leakage inductance parameters on the primary side of the transformer and the open triangle side, and then ignores the influence of the internal impedance of the transformer

This method can only calculate the capacitance current of the distribution network, but cannot calculate the leakage current. At the same time, the measurement accuracy is limited by the parameters of the transformer, and it is difficult to meet the current operation requirements of the distribution network.

[0007] In short, the existing technology cannot accurately measure the insulation parameters of the neutral point ungrounded distribution network to the ground

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