Direct current insulation monitoring device and method capable of compensating deviation of voltage to earth of positive pole and negative pole

Abstract

The invention relates to a direct current insulation monitoring device and a method capable of compensating deviation of voltage to earth of a positive pole and a negative pole. The device comprises a balanced bridge circuit, an unbalanced bridge circuit and a compensation bridge circuit. The compensation bridge circuit inputs resistance to the direct current bus negative pole voltage to earth or the direct current bus positive pole voltage to earth according to the deviation conditions of voltage to earth of the positive pole and the negative pole of a direct current system, so the direct current bus positive pole voltage to earth and the direct current bus negative pole voltage to earth are almost the same or achieve safe operation conditions of the direct current system. When the direct current bus voltage to earth deviates, the deviated voltage can be compensated through the compensation bridge circuit to enable the positive pole voltage to earth and the negative pole voltage to earth of the direct current system to be under a balanced state, and therefore a relay protection maloperation problem caused by the single point grounding of the positive pole of an exit relay is avoided.

Description

technical field [0001] The invention relates to a direct current insulation monitoring system and method capable of compensating positive and negative pole-to-ground voltage offsets, belonging to the field of direct current IT system insulation monitoring. Background technique [0002] The DC systems of power plants and substations provide power for control, protection, signals, and automatic devices. In order to ensure the continuity and reliability of power supply, DC systems are generally designed as ungrounded systems, that is, IT systems. According to the design requirements of the DC system of electric power engineering, it is necessary to carry out insulation monitoring on the DC IT system. [0003] At present, most insulation monitoring devices carry out insulation monitoring through the combination of balanced bridge and unbalanced bridge. By switching the unbalanced bridge, measure the voltage value of the positive and negative poles to the ground when the unbalan...

AI Technical Summary

Problems solved by technology

[0016] It can be seen that the voltage across the relay coil KM is greater than the operating voltage U of the relay d , at this time, relay protection malfunction may occur

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