Distribution line breakage monitoring method and device based on voltage and current vectors

Abstract

The invention discloses a distribution line breakage monitoring method and device based on voltage and current vectors. The method and device are applied in a three-phase three-wire power grid system with a neutral point not grounded or not directly grounded. The line breakage monitoring device is installed on a monitoring point of a line. The line leakage monitoring device works out the effective value and the phase angle of the three-phase line voltage and three-phase current at the same moment through the three-phase line voltage waveform and three-phase current waveform of a periodic three-phase synchronous sampling distribution line; whether a single-phase line breakage fault occurs on an upper-side line of the monitoring point or not is judged by computing and comparing the proportional relation of the sum of the largest voltage, the smallest voltage and the second smallest voltage in the effective value of the three-phase line voltage and the phase difference value relation of the smallest voltage and the second smallest voltage; whether a single-phase line breakage fault occurs on an upper-side or lower-side line of the monitoring point by comparing the proportional relation between the negative-sequence current and the positive-sequence current; whether a single-phase ground fault occurs on a lower-side line of the monitoring point by calculating the zero sequence current value.

Description

technical field [0001] The invention relates to a method and device for monitoring disconnection of distribution lines based on voltage and current vectors. Background technique [0002] The existing distribution line disconnection monitoring technology assumes that the three-phase voltage of the power supply side of the distribution network is symmetrical, and the three-phase load of the distribution network is assumed to be symmetrical. (or effective value) changes as the judgment basis to identify the single-phase disconnection fault of the distribution line, but the actual operation of the distribution network does not always meet the three-phase symmetrical operation state. Therefore, the single-phase disconnection fault identification method based on the voltage amplitude (or effective value) and current amplitude (or effective value) as the judgment basis has a high probability of misjudgment, and the voltage amplitude method is only applicable to the measurement of d...

AI Technical Summary

Problems solved by technology

Therefore, the single-phase disconnection fault identification method based on the voltage amplitude (or effective value) and current amplitude (or effective value) as the judgment basis has a high probability of misjudgment, and the voltage amplitude method is only applicable to the measurement of disconnection fault points. In the case of the upper side of the device, if the broken line fault point is on the lower side of the monitoring point, the voltage method will fail; the voltage method cannot identify whether a single-phase broken line has a single-phase ground fault at the same time; the current amplitude method is applicable to both the broken line fault point in the measuring device The upper side is also applicable to the situation where the disconnection fault point is on the lower side of the monitoring point, but the signal of the current method is not necessarily obvious, and the probability of misjudgment is high under the condition of asymmetric load of the distribution line, and it is easy to miss and misjudgment under light load conditions. It cannot be judged when there is no load, and the accuracy of fault judgment is greatly affected by the single-phase ground current when the line is light-loaded

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