Single-phase ground fault location method and equipment

Abstract

The invention provides a single-phase ground fault location method and apparatus. The method comprises the following steps that: a signal injection device is arranged on a three-phase bus or an outlet of a transformer substation; a plurality of groups of monitoring apparatus are hung on a three-phase power circuit; a current signal with special frequency is injected to the ground when a ground fault happens; only the monitoring apparatus which is located between the signal injection device and a ground fault point can extract the current signal from a carrier signal; and the monitoring apparatus locally displays fault judgment information and outputs the information in a radio form. The apparatus comprises the signal injection device and the plurality of monitoring apparatus, wherein the signal injection device is connected between a power line and the ground and used for detecting and judging the ground situation and injecting a modulated current signal to the ground, and the plurality of monitoring apparatus are arranged on several parts of the three-phase power circuit and used for detecting an injected signal returned from the grounded point, judging the fault and outputting the fault information. With the adoption of the method and the apparatus, not the fault current but the current signal injected by the signal injection device is selected for judging the fault, and the fault is more reliably judged due to the fact that the signal is free from the affect of the ground resistance and the circuit length of the fault point.

Description

technical field [0001] The invention relates to a method and equipment for judging and finding ground faults, in particular to a method and equipment for single-phase ground faults in a small current grounding system. Background technique [0002] At present, most distribution lines adopt the method of ungrounded neutral point or grounded through arc suppressing coil, collectively referred to as small current grounding system. When a single-phase ground fault occurs, the fault point only flows through the capacitive current of the system. The current is small and does not affect the power supply operation of the system, but it causes the voltage of the ungrounded phase to rise, threatening the safety of the line insulation porcelain bottle. Once the insulating porcelain bottle breaks down, it will cause a short circuit between the two phases and cause the circuit breaker to trip. For this reason, some products or methods for finding the location of the single-phase ground f...

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Problems solved by technology

When the resistance value of the grounding resistance is large, the injected signal current intensity is limited, making it difficult to be detected by the current magnetic field signal detection device, and the success rate is very low

Another example is the method described in the invention patents 01109726.4 and 01118274.1, which lacks the knowledge of the zero-sequence voltage and zero-sequence impedance of the small current grounding system. The signal is injected in the way of creating a disturbance. The signal has no fixed amplitude-frequency characteristics and is highly random. In principle, there are inherent defects and errors, so it is difficult to have operability and practical value.

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