Capacitance measurement method and measurement device for power distribution network with neutral point grounded through arc suppression coil

Abstract

The invention provides a capacitance measurement method for a power distribution network with a neutral point grounded through an arc suppression coil and a measurement device based on the method. The measurement method comprises the following steps of: (1) applying an excitation source, and injecting an excitation signal with the frequency between f0 and 2f0 (assuming the working frequency of the power distribution network as f0) into the power network through a secondary coil of the arc suppression coil, and assuming the frequency of the excitation signal as fc; (2) measuring the current, and measuring an output signal of a zero sequence current mutual inductor to obtain current magnitude; (3) measuring the voltage, and measuring voltage magnitude through a bus voltage transformer; and (4) calculating the capacitive reactance over the ground. The measuring device comprises a signal injecting module, and a bus voltage acquisition and processing module and a zero sequence current acquisition and processing module; the zero sequence current acquisition and processing module comprises a signal processing module electrically connected with an output end of the zero sequence current transformer. The measuring method can be used for conveniently and accurately measuring the capacitive reactance over the ground and the current, and the operations of an operator to the primary side of the power network are avoided.

Description

technical field [0001] The invention relates to a capacitance measurement method and a measurement device for a distribution network whose neutral point is grounded through an arc suppression coil, and more specifically, relates to a method for detecting current through a zero-sequence current transformer and detecting voltage through a bus voltage transformer A capacitance measurement method and a measurement device for a distribution network whose neutral point is grounded through an arc suppressing coil. Background technique [0002] With the development of the power supply network, the single-phase grounding capacitive current of the system continues to increase, and the resonant grounding method of the neutral point through the arc-suppression coil is becoming more and more common. In order to determine the capacity and inductance of the arc-suppression coil, it is first necessary to measure the capacitance and current of the grid. There are two methods for measuring th...

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Problems solved by technology

Its equivalent circuit diagram for the injected signal is attached figure 2 As shown, due to the uncertainty of the gear position of the arc suppression coil, the inductance of the arc suppression coil into the power grid cannot be determined, resulting in the inability to determine the value of the injected current flowing through the distributed capacitance of the power grid. Therefore, the existing capacitance tester must Disconnect the connection between the arc suppression coil and the neutral point. If an intermittent arc ground fault occurs during this period, without the compensation of the arc suppression coil to the power grid, it may cause overvoltage in the entire system, thereby damaging the equipment and destroying the safe operation of the system. ; and in the capacitance test, the operator still has to operate the primary grid, which brings hidden dangers to personal safety

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