Method and system for monitoring insulation level of substation power cable

Abstract

The invention relates to a method and a system for monitoring the insulation level of a substation power cable, which comprises a power cable insulation monitoring device based on an optimized direct current superposition method. A power cable insulation monitoring system is built based on the power cable insulation monitoring device. According to the power cable insulation monitoring device based on the optimized direct current superposition method, the same direct current voltage source is connected onto three phases of lines of a high-voltage bus respectively through three equivalent megohm-level current-limiting resistors, current is detected and sampled, a blocking capacitor is matched for use, the blocking capacitor is hooked between the primary-side neutral point of a voltage transformer and the ground, and when the insulation level of the power cable drops, the direct current can have a unique channel to conveniently and accurately calculate the direct current resistance. According to the method and the system of the invention, as the system is provided with the power cable insulation monitoring device based on the optimized direct current superposition method and the power cable insulation monitoring system is built, power cable insulation drop judgment based on the insulation monitoring system can be carried out.

Description

technical field [0001] The invention belongs to the technical field of on-line monitoring of power cable insulation, in particular to a method and system for monitoring the insulation level of power cables in a substation, which includes a power cable insulation monitoring device based on an optimized DC superposition method, and a power cable insulation monitoring system based on an insulation monitoring system. The drop criterion and the power supply system based on the principle of CT power supply. Background technique [0002] The degree of power cableization of urban power grid is an important symbol to measure the technical level of urban power grid, and it is also a necessary means to promote the rapid progress of urban civilization and improve the urban living environment. In the past 30 years, various technologies of power cables at home and abroad have developed rapidly, especially the development of three-layer co-extrusion production technology to manufacture XLP...

AI Technical Summary

Problems solved by technology

Disadvantages: The DC component is too weak to be detected accurately

Disadvantage: This method has strict requirements on the frequency and amplitude of the superimposed AC signal

Disadvantages: DC high voltage is superimposed on the high-voltage bus through the primary neutral point of the voltage transformer, which may cause bias and saturation of the voltage transformer, and may also cause relay protection malfunctions

[0018] The power supply of existing power cable insulation testing devices generally uses the power frequency 220V AC voltage from the substation to power low-voltage important protection and monitoring devices. On the other hand, in order to detect the insulation level, the power cable insulation testing device needs to communicate with high voltage The busbar and its power cables are directly connected, so that the 220V AC power supply and high-voltage AC busbars of different levels are connected to the same power cable insulation testing device through the insulation testing device. It brings great potential safety hazards and is strictly prohibited by the power industry and national standards

It hinders the popularization and application of power cable insulation detection device

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