Power distribution system equivalent ground distributed capacitor measuring method

Abstract

The invention provides a technical scheme of a power distribution system equivalent ground distributed capacitor measuring method, comprising the following steps: 1) injecting signal current with constant frequency into a power distribution system; 2) measuring neutral current of primary side of an arc suppression coil and busbar voltage of a busbar in the power distribution system, filtering the measured neutral current and busbar voltage, and filtering out power frequency quality to obtain current injected into the power distribution system and pressure drop generated by the current on an equivalent ground distributed capacitor; 3) modeling the power distribution system based on a lumped parameter model, and calculating a complex functional equation of the injected signal current, voltage and power distribution system equivalent ground distributed capacitance according to Ohm's law; and 4) calculating equivalent ground distributed capacitance value of the power distribution system and ground insulation resistance value of the power distribution system according to the equation in the step 3). The method provided by the invention is clear in principle, is easy to implement, and has a wide application range and high accuracy in computation.

Description

Technical field: [0001] The invention relates to a method for calculating the equivalent-to-ground distributed capacitance of a power distribution system based on constant-frequency injection signals. Background technique: [0002] In the prior art, it is known that in the power system, more than 85% of the faults are single-phase ground faults, most of which are instantaneous ground faults. In the small current grounding system, since the neutral point of the system is not effectively grounded, the single-phase ground fault current is the sum of the distributed capacitive currents of the non-fault lines. When the current exceeds a certain amplitude (generally, the on-site regulation is greater than 10A), an arc suppression coil must be installed to reduce the grounding arc and achieve the purpose of quickly eliminating the instantaneous ground fault. With the transformation of the power distribution system, while the power supply radius is gradually shrinking, the short-ci...

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Problems solved by technology

The inductance of the arc-suppression coil must be adjusted artificially when the displacement voltage method is used to calculate the capacitance to ground. The operation is more complicated and has a certain impact on the safety of the system. The asymmetry of the system, damping rate and other factors have great influence, so the start-up shift measurement is frequent; the principle of injecting variable frequency signal method is clear, easy to implement, and has great advantages, but because the resonant frequency is generally near the power frequency, it is easy to be affected by the medium frequency. The impact of the unbalanced voltage of the neutral point, and because the two frequency signals may be relatively close, and the resonant frequency is unknown, it is difficult to implement filtering, so it is difficult to eliminate the influence of the power frequency component. In addition, this method requires the injection of frequency conversion Signal source, signal switching is sometimes required when ground fault line selection is performed, which is the deficiency of the existing technology

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