Bridge used for direct current insulation monitoring device and running method thereof

Abstract

The invention provides a bridge used for a direct current insulation monitoring device and a running method of the bridge used for the direct current insulation monitoring device. The bridge comprises a balanced bridge and a detection bridge, wherein the balanced bridge is composed of a balanced resistor R1 and a balanced resistor R2, wherein the balanced resistor R1 is connected between a bus positive pole and the earth, and the balanced resistor R2 is connected between a bus negative pole and the earth. The detection bridge is composed of a detection resistor R3, a detection resistor selector switch K1 and / or a detection resistor R4 and a detection selector switch K2, wherein the detection resistor R3 and the detection resistor selector switch K1 are connected between the bus positive pole and the earth, and the detection resistor R4 and the detection resistor selector switch K2 are connected between the bus negative pole and the earth. For the detection resistor R3 connected between the bus positive pole and the earth and the detection resistor R4 connected between the bus negative pole and the earth, at least one of the R3 and the R4 is changeable and controllable. The bridge used for the direct current insulation monitoring device has the advantages of carrying out insulation monitoring by utilization of the detection bridge with the changeable resistor, being capable of changing the resistance value of the detection bridge in a self-adaptation mode according to direct earth capacitance and insulation resistance of a direct current system and taking safety of the direct current system and accuracy of insulation resistance measuring into account.

Description

technical field [0001] The invention belongs to the field of DC IT system insulation monitoring, and in particular relates to an electric bridge used for DC insulation monitoring and an operating method thereof. Background technique [0002] The DC insulation monitoring device used in substations or power plants generally performs insulation monitoring by combining the balance bridge and the detection bridge. Negative pole-to-ground voltage value, use the measured positive and negative pole-to-ground voltage values ​​to calculate the positive pole-to-ground insulation resistance and negative pole-to-ground insulation resistance of the DC system. [0003] figure 1 It is the principle of DC insulation monitoring technology commonly used at present. Among them, resistor R1 and resistor R2 form a balanced bridge, and their resistance values ​​are equal. Switching element K1, switching element K2, resistor R3 and resistor R4 together form a detection bridge. Generally speaking ...

AI Technical Summary

Problems solved by technology

[0019] However, due to the low fluctuating voltage, the calculation accuracy of insulation resistance will be greatly reduced, which will affect the performance of monitoring action, and then affect the correct fault judgment of operation and maintenance personnel.

[0020] In the prior art, a detection bridge with a fixed resistance value is used to detect the insulation resistance of the DC system. If the ratio between the resistance value of the detection bridge and the resistance value of the balance bridge is large, the accuracy of the insulation resistance measurement is low; if the detection bridge If the ratio between the resistance value and the resistance value of the balance bridge is small, the voltage fluctuation of the busbar to ground caused by the operation of the detection bridge will be large, and it is difficult to meet the safety requirements of the DC system.

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