A system and method for measuring capacitive current in a neutral point ungrounded distribution network

Abstract

The invention relates to a distribution network capacitance current measurement technology, in particular to a neutral point ungrounded distribution network capacitance current measurement system and method. The measurement system includes a busbar voltage transformer, an adjustable resistance, a variable frequency voltage source and a voltage measuring instrument; The adjustable resistance is connected to both ends of the third winding of the busbar voltage transformer after being connected in series with the variable frequency voltage source, and the voltage measuring instrument is also connected to both ends of the third winding of the busbar voltage transformer. The method of measuring by the measuring system solves the problem that the short-circuit impedance of the busbar voltage transformer affects the measurement accuracy, and considers the influence of the zero-sequence voltage caused by the unbalance of the power grid on the signal injection method to measure the capacitor current, so as to improve the capacitance of the distribution network. The accuracy of the current measurement, using the accurate Thevenin equivalent circuit model, to solve the system's capacitance to ground. The measurement process is carried out on the third winding side of the transformer, and there is no need to change the wiring of the primary equipment. The measurement method is safe and convenient, and the results are accurate and reliable.

Description

technical field [0001] The invention belongs to the technical field of capacitive current measurement of a distribution network, and in particular relates to a system and method for measuring a capacitive current of a neutral point ungrounded distribution network. Background technique [0002] The early medium and low-voltage distribution networks in my country mostly adopted the neutral point ungrounded mode. When a single-phase ground fault occurs, the grounding arc can be self-extinguished under the condition that the grid capacitive current is not large, and the distribution network can continue to supply power with faults for 1~ 2 hours. With the continuous development of the distribution network of the power system, especially the large number of cable lines in the urban power grid, the capacitive current of the line to the ground continues to increase, resulting in a sharp increase in the single-phase ground fault current of the distribution network line, and it is dif...

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Problems solved by technology

However, considering that there will be a certain zero-sequence voltage during the actual operation of the power grid, the zero-sequence voltage will be reflected on the open triangle end of the transformer, which will have a great impact on the measurement of the voltage, often making the measurement results more inaccurate

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