A single-phase ground fault detection method and detection equipment for transmission and distribution lines

Abstract

The invention provides a method and equipment for detecting a single-phase earth fault of a transmission and distribution line. The method comprises the following steps of: 1, detecting the mutation rate of transient current of the line, wherein the mutation rate Delta Ip / Delta t of the transient current is greater than Rh when the transient current positively jumps; and 2, determining a short-circuit earth fault when detecting that line voltage drops and V is smaller than Vh, wherein the sequence of the step 1 and the step 2 can be changed. According to the fault detection equipment, false alarm or alarm omission can be prevented, demands of different users can be met, and the equipment is applicable for mass production.

Description

technical field [0001] The invention relates to power equipment, in particular to the detection of single-phase grounding faults of power transmission and distribution lines. Background technique [0002] Transmission and distribution lines have many branches, long lines, and complex loads. However, when a ground fault occurs, these faults must be eliminated as soon as possible, otherwise the phase voltage will increase, which will seriously damage the insulation performance of the power supply equipment and lines, and then cause phase-to-phase short-circuit faults, thereby reducing the quality and efficiency of power supply. To troubleshoot, you must first find the location where the fault occurred. [0003] For neutral point non-directly grounded power transmission and distribution systems, when a single-phase ground fault occurs, the line voltage does not change, the line load current does not change, and the characteristic quantity is not very obvious, so single-phase g...

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Problems solved by technology

Although the transient current is relatively obvious, because the duration of the transient is very short and it is a fast decay process, less than a quarter of the power frequency cycle, the detection equipment obviously cannot accurately detect the instantaneous value of the transient, so It is also impossible to accurately detect the magnitude of the transient quantity, not to mention the ever-changing line load. Sudden fluctuations and changes in the load may cause signals with overlapping frequency ranges and transient current frequency ranges on the line. At this time, misjudgments will occur. See figure 2

[0007] Therefore, none of the above three types of ground fault detection methods can reliably detect single-phase ground faults.

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