Method and device for rapidly detecting short-circuit fault of power system

Abstract

The invention relates to a device for rapidly detecting the short-circuit fault of a power system, which comprises a power supply circuit, an A / D sampling circuit, a voltage / current detection circuit, a digital signal processing signal and a protective signal output circuit, wherein the power supply circuit converts 220V alternating current into direct current for ensuring normal running of the entire device; voltages and currents in a power grid are transformed by an external transformer and then fed into the voltage / current detection circuit, voltage / current signals are formed by means of the regulation and setting of the voltage / current detection circuit, then converted by the A / D sampling circuit from analog quantity to digital quantity and at last output to the digital signal processing signal, the digital signal processing signal judges whether the short-circuit fault occurs, and if so, the digital signal processing signal controls the protective signal output circuit to send a protective signal. The device can judge the short-circuit fault according to the voltage / current signals at ports of each breaker only, and the detection time of the device is in general less than 5ms; and the device can facilitate expanding and updating power grid and reforming network.

Description

technical field [0001] The invention relates to the field of power system detection, in particular to a detection method and device capable of quickly detecting short-circuit faults in the power system, which can be used for short-circuit protection of circuit breakers. Background technique [0002] At present, the short-circuit fault detection mechanism of the circuit breaker used in the domestic power supply and distribution network is mainly a mechanical structure. The electromagnetic force or thermal effect generated by the short-circuit current is used to trip the circuit breaker protection. The principle of short-circuit fault detection is: When a short-circuit fault occurs in the power grid, the short-circuit current is far greater than the rated current. Using this characteristic, the short-circuit fault is detected by detecting whether the current increases abnormally. Due to the common shortcomings of traditional circuit breakers in short-circuit fault detection, s...

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Problems solved by technology

Because there are not only non-periodic components with fast decay in the short-circuit current, but also a large dynamic range, and the influence of various factors such as transformer magnetic saturation and detection phase shift in the detection link, it is very difficult to directly detect the short-circuit current accurately, so Such methods usually require the short-circuit current to be much greater than the rated value in order to accurately make a short-circuit fault judgment

Secondly, the detection speed of this method depends entirely on the rising speed of the short-circuit current, and due to the influence of the distribution parameters of the power grid, the initial state of the short-circuit and the load factors, the rising speed of the short-circuit current can be fast or slow, so the detection speed is not stable. Good for short circuit protection design

Finally, this method is still unable to distinguish the direction of the short-circuit current, especially when there are two power supplies with approximately the same capacity in the grid and the short-circuit feedback current of the load is small, if a short-circuit occurs at the output port of one of the power supplies, the The short-circuit current amplitudes of the two power supply protection circuit breakers are basically the same and the directions are opposite. Selective protection cannot be realized only by the magnitude of the passing current, and finally the circuit breakers of the two power supplies trip at the same time.

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