Micro current detection circuit for grounding devices under condition of spark discharge

Abstract

The invention provides a micro current detection circuit for grounding devices under the condition of spark discharge. An I / V conversion circuit of a T-type negative feedback current-to-voltage conversion structure built with a few precision small resistors is adopted. Compared with a single precision super large metal film resistor, the T-type negative feedback current-to-voltage conversion circuit can greatly lower the input impedance, and can effectively reduce the shunting of the spark discharge current on a grounding device and an amplifier load and further reduce the system error. The ion current is shaped through a fourth-order Chebyshev low-pass filter, and the advanced anti-jamming technology in the field of small signal detection is adopted to make the detected current more accurate. The spark discharge current detection circuit is not only applicable to grounding device micro current detection under the condition of spark discharge, but also applicable to other electrical equipment. The spark discharge current detection circuit has high practical value.

Description

technical field [0001] The invention relates to the technical field of lightning protection, and more specifically, to a tiny current detection circuit used in the spark discharge condition of a grounding device. Background technique [0002] In the lightning protection design, grounding is used to smoothly discharge the lightning current into the ground to reduce the overvoltage caused by it. Grounding is an integral part of lightning protection installations. Lightning protection grounding resistance is mainly composed of two parts: power frequency grounding resistance and impact grounding resistance. When the transmission and distribution lines are struck by lightning, the impact current flows to the ground through the grounding device. Under the action of the impact current, when the current density flowing out of the grounding body exceeds the basic field strength of the soil, a spark discharge will appear around the grounding body. area, which is equivalent to changi...

AI Technical Summary

Problems solved by technology

exist figure 1 -(a) In the circuit, the current forms a potential on Rc, and then changes with the output terminal. The output terminal potential is the output amplitude, and this potential will change with the change of the input current, and the changed current will be directly fed to the tube Collector, thus affecting the sensitivity of spark discharge current detection

exist figure 1 - In (b), theoretically as long as the Rc is large enough, even if the input current is small, it can output the ideal voltage V out , but in practical circuits, the input impedance of the op amp cannot be infinite

While considering the bias current I b For the measured spark discharge current I + effect, the actual output is: V out =-(I + -I b )R c , when the bias current I b Greater than the measured spark discharge current I + , the measured spark discharge current will be overwhelmed and cannot be detected

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