Low-voltage inverse-time leakage protection method

Abstract

The invention discloses a low-voltage inverse-time leakage protection method. The method comprises the steps that whether or not a system is in a leakage state is judged by looking up a table on the basis of the system voltage level and the leakage resistance value; if the system is in the leakage state, the inverse time process is conducted, the inverse time delay time of the current leakage resistance is obtained by looking up the table, and if the inverse time delay time is up, an action is executed; and if the system is in a non-leakage state, the inverse time process cannot be conducted,and measurement on the ground insulation resistance is conducted by combining an additional DC power supply method to achieve low-voltage inverse-time protection, wherein measurement on the ground insulation resistance through the additional DC power supply method is achieved by an additional +44V DC power supply generation circuit, an insulation resistance measurement bridge circuit and an insulation resistance measurement signal conditioning circuit. According to the method, by means of the comprehensive measurement technology of the ground insulation resistance measurement method combiningthe inverse-time leakage protection algorithm with the additional DC power supply method, leakage measurement on the neural point ungrounded power supply system under a coal mine can be effectively and precisely conducted, and the leakage protection function is achieved.

Description

technical field [0001] The invention relates to the technical field of leakage protection, in particular to a method for low-voltage leakage inverse time protection. Background technique [0002] The single-arm bridge circuit (hereinafter referred to as the bridge circuit) is also called the Wheatstone bridge circuit, which is a commonly used circuit in electricity; it is composed of the principle of bridge balance, and can not only measure resistance, but also measure capacitance, Inductance, etc.; therefore, the bridge circuit is widely used in automatic instrumentation and automatic control, and its measurement principle is as follows: Figure 4 shown. [0003] In practical applications, there is very little opportunity to obtain bridge balance by adjusting the resistance of the bridge arm resistance, and finally reverse the resistance of the bridge arm to be measured. In most cases, the current resistance to be measured is reversed by measuring the voltage difference. r...

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Problems solved by technology

[0005] However, there are still measurement defects in the existing technical solutions, which are applied to the ungrounded neutral point power supply system in coal mines. The present invention adopts a low-voltage leakage feedback method combined with an additional DC power supply method to measure the ground insulation resistance and an inverse time leakage protection algorithm. Method of Time Limit Protection

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