High/low-voltage isolation circuit

Abstract

The invention belongs to a high and low voltage isolating circuit, comprises two voltage input ends and two voltage output ends, and has the following essential technical characteristics: a nonlinear element is respectively parallel connected between the two voltage input ends and the two voltage output ends, the two voltage input ends are respectively connected with two photoelectric couplers, and the two photoelectric couplers are respectively connected with the two voltage output ends. The high and low voltage isolating circuit effectively solves the safety problems of human bodies and instruments in a measuring end which are caused by intermittent excess voltage, chopped wave excess voltage and excess voltage situation that is generated by the sudden raising of earth point potential in the alternate and direct current withstand voltage testing process, is characterized by quick response speed, prompt protection, simple use and convenient transplantation, and can be widely applied into a measuring loop of the alternate and direct current withstand voltage testing and other measuring devices that need electric protection and isolation.

Description

technical field [0001] The invention belongs to an overvoltage protection circuit, in particular to a high and low voltage isolation circuit. Background technique [0002] In high-voltage tests, it is often necessary to measure higher-level voltage signals for measurement, protection, or monitoring. Although these high-voltage signals are mostly converted into low-voltage signals through transformers or voltage dividers, once a device occurs Sudden insulation breakdown discharge, unreliable grounding, or sudden rise in the potential of the grounding point may introduce high voltage into the measurement circuit, endangering the personal safety of the measurement end and the safety of instruments and meters. Overvoltages in various situations may occur during actual measurement: [0003] 1. When the electromagnetic state of the test circuit changes suddenly, electromagnetic oscillation will occur, resulting in intermittent overvoltage caused by breakdown or flashover of the t...

AI Technical Summary

Problems solved by technology

[0003] 1. When the electromagnetic state of the test circuit changes suddenly, electromagnetic oscillation will occur, resulting in intermittent overvoltage caused by breakdown or flashover of the tested equipment. Its characteristics are: short time, generally a few milliseconds, high amplitude, about The test voltage is 1-2 times of the test voltage, and the conventional overvoltage protection device often does not have time to act in the future, and the overvoltage has been transmitted to the measuring terminal of the instrument and meter, which will bring harm to the person and equipment; 2. The grounding resistance is too large or the grounding is not good. When it is reliable, once the current of the measurement circuit increases, the potential of the grounding point will increase significantly, resulting in overvoltage. This overvoltage will endanger the safety of people and instruments. The conventional method is only to reduce the potential of the grounding point. It cannot be solved fundamentally; 3. The clipping overvoltage caused by the operator's misoperation, such as the boost speed is too fast, exceeds the rated test voltage or the clipping overvoltage caused by sudden power failure during the pressurization process will endanger the measurement terminal. For personal safety and safety of instruments and meters, conventional overvoltage protection devices can only protect power frequency overvoltage, but cannot protect against chopping wave overvoltage.

[0004] In summary, the problems existing in the overvoltage protection device of the existing measurement circuit are: 1. It is only suitable for short-circuit protection, and there is a problem of slow response speed of overvoltage protection. Due to the short time of intermittent overvoltage and chopping overvoltage, the , the existing protection devices cannot protect against intermittent overvoltage and chopping overvoltage;

[0005] 2. The primary equipment and the instrument at the measuring end share a grounding point. When the potential of the grounding point rises, the safety of the person and the instrument at the measuring end will be endangered.

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