Protective circuit for microcomputer type relay protection device

Abstract

A protective circuit for a microcomputer type relay protection device comprises an operational amplifier, a resistor and an adjustable resistor, wherein the reverse-phase input end of the operation amplifier is connected with a digital ground wire through the first resistor; one end of the adjustable resistor is connected with the reverse-phase input end of the operation amplifier and the other end of the adjustable resistor is connected with the output end of the operation amplifier; the in-phase input end of the operational amplifier is the input end of the circuit and is connected with the output end of an analog-digital convertor A / D; and the output end of the operational amplifier is the output end of the circuit and is connected with the input end of the microcomputer type relay protection device. The protective circuit for the microcomputer type relay protection device provided by the invention has the effects that an in-phase operation amplification circuit is added in front of the microcomputer type relay protection device and a small resistance grounded current signal is amplified, so that the output signal can easily meet the sensitivity requirement of the microcomputer type relay protection device.

Description

technical field [0001] The invention belongs to the technical field of relay protection, in particular to a protection circuit used for a relay protection device of a microcomputer. Background technique [0002] In substation DC system one-point grounding line selection device (the principle is to inject low-voltage low-frequency AC signal into the DC system, generally 10V, 10HZ) and distribution network small current grounding line selection system, when a single-phase grounding short circuit occurs in the line, if When the grounding point is grounded through a resistor, the value of the grounding current will be very small, which is easy to exceed the measurement range of the protection device, so that the microcomputer protection device cannot guarantee the accuracy of grounding detection, resulting in misjudgment or data movement problems. Contents of the invention [0003] In order to solve the above problems, the object of the present invention is to provide a protec...

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Problems solved by technology

[0002] In substation DC system one-point grounding line selection device (the principle is to inject low-voltage low-frequency AC signal into the DC system, generally 10V, 10HZ) and distribution network small current grounding line selection system, when a single-phase grounding short circuit occurs in the line, if When the grounding point is grounded by a resistor, the value of the grounding current will be very small, which is easy to exceed the measurement range of the protection device, so that the microcomputer protection device cannot guarantee the accuracy of grounding detection, resulting in misjudgment or data movement problems

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