Zero sequence current transformer wire-break detection and residual current detection circuit

Abstract

The invention relates to a zero sequence current transformer wire-break detection and residual current detection circuit and aims at solving the problem of waveform distortion of the residual current picked up by a sampling unit. The zero sequence current transformer wire-break detection and residual current detection circuit comprises a constant-current unit for providing a constant current, an amplification unit for amplifying an input signal and the sampling unit for converting the current signal into a voltage signal; the two ends of the sampling unit are correspondingly connected with the positive and negative input ends of the amplification unit, respectively; the constant-current unit is connected to the input end of the amplification unit after being connected in parallel with the sampling unit; a switching unit is arranged between the constant-current unit and the amplification unit; besides, the detection circuit further comprises a control unit which is used for outputting a signal to switch on the switching unit if determining that the detected residual current value is zero and thus detecting the working condition of a zero sequence current transformer to decide to alarm or not, or outputting a signal to switch off the switching unit when the residual current value is non-zero and then comparing the residual current value with a standard value to decide to alarm or not.

Description

technical field [0001] The invention relates to a detection circuit, in particular to a zero-sequence current transformer disconnection detection circuit and a residual current detection circuit. Background technique [0002] The residual current protection device is used to protect the electrical circuit from ground faults, prevent equipment and electrical fire accidents caused by ground fault currents, and can also be used to provide indirect contact protection against personal electric shock hazards. The core of the residual current protection device is the zero-sequence current transformer disconnection detection circuit and the residual current detection circuit, which are intended to monitor the working status of the zero-sequence current transformer. The detection circuit needs to run in the power grid for a long time. In the existing residual current protection device, in order to detect whether the zero-sequence current transformer is disconnected, a certain constan...

AI Technical Summary

Problems solved by technology

[0003] In order to overcome the deficiency of residual current waveform distortion picked up by the sampling unit, the present invention provides a zero-sequence current transformer disconnection detection circuit and a residual current detection circuit

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