Line selection method and system based on zero sequence power polarity

Abstract

The invention discloses a line selection method and system based on zero sequence power polarity. The line selection method comprises the following steps of: determining a fault starting point according to the variable quantity of zero-sequence current; enabling the zero-sequence voltage and the zero-sequence current of each line to pass through a digital high-pass filter respectively, and calculating instantaneous zero-sequence power by using the zero-sequence voltage and the zero-sequence current which pass through the digital high-pass filter; judging the polarity of the instantaneous zero-sequence power according to a value of the instantaneous zero-sequence power within the preset time after the fault starting point starts; and determining a fault line according to the polarity of the instantaneous zero-sequence power. The system comprises a fault starting point judgment module, an instantaneous zero sequence power calculation module, a polarity judgment module and a fault line judgment module. According to the line selection method, calculation and line selection are carried out through the fault feature information of the voltage and current transient components, the calculation amount is small, the line selection speed is high, the method is not affected by transition resistance and a neutral point grounding mode, the accuracy is high, a grounding line can be rapidly judged and cut off, and serious loss of the whole power distribution network caused by secondary damage is prevented.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a line selection method and system based on zero-sequence power polarity. Background technique [0002] Most of the medium and low voltage distribution networks in my country adopt the operation mode of ungrounded neutral point or grounded through arc suppressing coil. The systems using these two neutral point grounding methods are collectively called small current grounding system. Its advantage is that the system appears After a single-phase fault, the current at the fault point is small, which does not affect the normal operation of the system in a short period of time, which meets the needs of the distribution network to ensure the continuous supply of power at the end of the power system. However, with the increase of system capacity and the continuous increase of the total length of distribution network lines, the capacitive current of lines to...

AI Technical Summary

Problems solved by technology

However, with the increase of system capacity and the continuous increase of the total length of distribution network lines, the capacitive current of the line to ground is also increasing

If the grounding line cannot be judged in time and the fault is eliminated, long-term operation with faults will easily cause the fault to expand to two or more points of grounding short circuit. Once the arc is grounded, the system will be subjected to overvoltage, resulting in damage to equipment and damage to system insulation.

Therefore, there is a lack of a method for judging the grounding line when a single-phase grounding fault occurs in a small current grounding system, which is prone to secondary damage and brings serious losses to the entire distribution network

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