System and method for rapidly determining single phase earth fault

Abstract

The invention discloses a system and method for rapidly determining a single phase earth fault. A structure of the system comprises a voltage transformer connected with electric signals, an isolation amplifier, a filtering rectifier, a hysteresis comparator, a monostable circuit capable of being repeatedly triggered and a microcontroller, wherein the microcontroller is connected with the hysteresis comparator and the monostable circuit capable of being repeatedly triggered. According to the system and method for rapidly determining the single phase earth fault, a characteristic of rapid responding and determining of hardware can be realized, and an advantage of flexible threshold value setting of software can be retained; during single phase earth fault determining operation, alternating current voltage signals are converted into a continuous pulse string via combination of a filtering rectification circuit and the hysteresis comparator; specifically the monostable circuit capable of being repeatedly triggered is adopted, and the pulse string is shaped into a signal pulse having a rising edge characteristic via which determining operation can be conducted via the microcontroller; via the method, a problem of threshold value jitter in a conventional hardware method can be effectively prevented, flexible threshold value setting can be realized via the microcontroller, strong universality can be realized, and high transferability is achieved.

Description

technical field [0001] The invention relates to a small current grounding system, in particular to a system and method for quickly judging a single-phase grounding fault. Background technique [0002] In the small current grounding system, it is generally judged whether the system has a single-phase ground fault according to the neutral point voltage 15% when the system side metal is grounded. Therefore, when the system side voltage is greater than 15%, it is considered that the system has a single-phase ground fault. Fault, at this time, the controller needs to quickly judge the fault, and at the same time make the arc suppression action after the fault occurs. It can be seen that it is very important to quickly and accurately judge the single-phase ground fault. [0003] The judgment methods for single-phase ground faults are generally divided into two categories. One method is software implementation, which uses software to collect and calculate the sampling voltage, and ...

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Problems solved by technology

[0003] The judgment methods for single-phase ground faults are generally divided into two categories. One method is software implementation, which uses software to collect and calculate the sampling voltage, and compares and judges it with the voltage threshold. This method occupies a part of software resources, increases software expenses, and the time for a single judgment is uncertain; the other type is hardware implementation, which usually needs to be converted to direct before making a judgment. Capacitor filtering is required during the conversion process, which will cause the judgment waveform to be near the critical voltage. Jitter occurs, there is a certain blind area for controller detection, and according to the actual site conditions, the threshold value of voltage judgment (starting voltage) is generally set at 20-35%, and it is impossible to change the completed module with general hardware methods, and the versatility is not good. powerful

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