Method and system for judging disappearance of single-phase ground fault in neutral point non-effectively grounded system

Abstract

The invention discloses a method and system for judging the disappearance of a single-phase grounding fault in a non-effective neutral point grounding system. A three-phase switch is installed at the busbar of a substation, and the occurrence of single-phase grounding is calculated according to the ground-distributed capacitance values ​​of all lines of the distribution network. When a single-phase ground fault occurs, judge the fault phase according to the change of the bus voltage of the substation, and control the corresponding grounding switch at the fault phase bus to close; after a certain short time delay and adjust the adjustable resistance After the resistance value is obtained, the current value of the adjustable resistance branch after the resistance value is adjusted is obtained, and a preliminary judgment is made on whether the actual fault of the line has disappeared; After adjusting the resistance value of the adjustable resistor in the following order, continuously obtain the current values ​​of the adjustable resistor branch under multiple different resistance values, and judge again whether the actual fault of the line disappears.

Description

technical field [0001] The present disclosure relates to the field of fault judgment, in particular to a method and system for judging disappearance of a single-phase ground fault in a neutral point non-effectively grounded system based on an adjustable resistance. Background technique [0002] The distribution network with a voltage level of 35kV and below in my country usually adopts the operation mode of non-effective grounding of the neutral point. The advantage is that when a single-phase ground fault occurs, the line voltage is still symmetrical and will not affect the normal operation of the load. The operation with faults does not exceed 2 hours, which plays an important role in improving the power supply reliability of the distribution network. But this mode of operation will also bring certain problems, for example, the neutral point voltage of the system and the non-fault phase voltage will increase, which will cause damage to the system insulation, and may cause m...

AI Technical Summary

Problems solved by technology

[0007] In order to overcome the deficiencies of the above-mentioned artificial heuristic method, on the premise of taking into account both safety and reliability, the present disclosure provides a method and system for judging the disappearance of a single-phase ground fault in a neutral point non-effectively grounded system based on an adjustable resistance. Adjust the resistance to change the grounding resistance value of the distribution network. By comparing the changes of the corresponding electrical quantities under different resistance values, it can automatically judge whether the actual fault of the line has disappeared, and can quickly, timely and reliably judge whether the actual fault of the line has disappeared.

Images