Detection method of S injecting signal

Abstract

The invention discloses a detection method of an S injecting signal. The problem that the S injecting signal is so small to be detected currently is solved. When a power distribution system has a single-phase grounded error, the weak S injecting signal is detected by utilizing a random resonance theory so that the aim of selecting lines is fulfilled. The method comprises the following steps that:1), when a power distribution net has the single-phase grounded error, zero sequence currents of various lines can be sine signals mainly at 50Hz, a weak current signal with special frequency being 220Hz is injected into a system through a signal injecting device; 2), the injected weak current signal with the special frequency only flows through an error phase, and then is grounded through a grounded point, and the signal is a line selection judgment signal required to be detected; and 3), the output of the system can be enhanced based on the random resonance theory under a certain condition,and therefore, the weak current signal injected by the signal injection device can be detected by utilizing the random resonance theory, so that the line selection can be carried out completely.

Description

technical field [0001] The present invention relates to a detection method of injection signal in single-phase ground fault line selection technology of distribution network, in particular to a detection method of S injection signal, and the detected injection signal is a diagnostic signal for single-phase ground fault line selection . Background technique [0002] my country's 6~35kV distribution network mainly operates in the low-current grounding mode. Under this mode, the probability of single-phase grounding faults is the highest, but the problem of fault line selection has not been completely resolved. [0003] Most of the line selection methods use many characteristic signals of the fault line itself to form the line selection criterion, but the common defect of this type of criterion is that as the grounding resistance increases, the fault characteristic quantity will be greatly reduced, and it is difficult to guarantee Accuracy of fault line selection in case of hi...

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Problems solved by technology

[0003] Most of the line selection methods use many characteristic signals of the fault line itself to form the line selection criterion, but the common defect of this type of criterion is that as the grounding resistance increases, the fault characteristic quantity will be greatly reduced, and it is difficult to guarantee Accuracy of fault line selection under high ground resistance

In the 1990s, Professor Sang proposed the fault line selection method based on the injection principle for the first time. The proposal of this method is a leap in the field of fault line selection. Instead, artificially inject a current signal of a specific frequency into the system from the secondary side of the bus PT. The injected signal only flows through the fault line and then enters the ground through the grounding point. Therefore, as long as the injected current signal is detected, the fault line can be selected. , but limited by the PT capacity of the busbar, the amplitude of the injected AC current signal is weak and difficult to track

This line selection idea has been favored by the majority of electric power researchers, and a variety of small current ground fault line selection methods based on the injection principle have been proposed, including: 1) inject controllable pulse signals and square wave signals into the fault system respectively, Its principle is the same as the "S injection method", and it does not fundamentally solve the problem of small injection signals; 2) The line selection method of injecting half-wave DC signals, which injects a larger half-wave DC current from the neutral point of the system The signal is used as the line selection criterion, which can essentially solve the problem of low line selection accuracy, but an additional grounding transformer is required for the neutral point ungrounded system, which limits its field application to a certain extent; 3) Selection based on controllable short-circuit Line method, respectively implement controllable and effective grounding from the neutral point of the transformer and the open triangle on the secondary side of the bus PT, thereby generating a fault current with a large amplitude, which is easy to detect but will not affect the normal operation of the system. Its field application needs further research

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