Resonance grounding power distribution network ground parameter measurement method considering damping resistance

Abstract

The invention provides a resonance grounding power distribution network ground parameter measurement method considering damping resistance, and the method is suitable for a neutral point arc suppression coil cascading damping resistor grounding power distribution network. The method comprises: injecting a non-power-frequency characteristic frequency constant-current signal into a power distribution network through a voltage transformer in an arc suppression coil; measuring the returned characteristic frequency voltage signal from the neutral point zero-sequence voltage transformer of the powerdistribution network, changing the frequency of the current signal, searching the resonance angular frequency of the zero-sequence equivalent circuit of the power distribution network, and calculating the ground capacitance and the ground leakage conductance of the power distribution network. The influence of impedance and damping resistance in the voltage transformer can be eliminated, high-precision measurement of ground parameters of the resonance grounding power distribution network is achieved, accurate tuning of the arc suppression coil is facilitated, measurement is safe and rapid, andnormal operation of the power distribution network is not affected.

Description

technical field [0001] The invention belongs to the field of distribution network measurement, and in particular relates to a method for measuring ground parameters of a resonant ground distribution network in consideration of damping resistance. Background technique [0002] my country's current "Code for Design of Overvoltage Protection and Insulation Coordination of AC Electrical Installations" clearly stipulates that the single-phase ground fault capacitance current of 6~66kV system shall not exceed 10A, so the medium and low voltage distribution network generally adopts the neutral point grounding method through the arc suppression coil, Limit capacitive current to ground. With the continuous expansion of the distribution network, the laying length of cables has increased significantly, and the single-phase ground fault current (especially the active component of the fault current) has risen sharply, making it difficult to eliminate the fault arc, and the intermittent ar...

AI Technical Summary

Problems solved by technology

Due to the small proportion of damping resistance in the zero-sequence impedance of the system, the influence of damping resistance is often not considered in traditional ground insulation parameter measurement methods

As the proportion of three-phase unbalanced loads and nonlinear loads in the distribution network increases, the three-phase asymmetry of the distribution network gradually increases, and the resistance value of the damping resistor tends to increase, which leads to the traditional ground insulation parameter measurement method The measurement accuracy decreases accordingly, and its inherent defects in the measurement principle gradually become prominent

Invention patent 2017109911831 proposes an online measurement method for the capacitance current of the distribution network. Although it can eliminate the influence of the arc-suppression coil series damping resistance and the internal impedance of the voltage transformer, the formula is relatively complicated, and the capacitance to ground can only be obtained separately. Due to the formula It is directly derived from the injection signal and the return signal. When the injection signal is weak and the measured return signal has a slight error, it will cause a huge error in the result

[0005] To sum up, no method has been proposed at home and abroad that can eliminate the influence of the internal impedance and damping resistance of the voltage transformer, and take into account the rapidity, accuracy and safety of the ground parameter measurement method of the resonant grounded distribution network.

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