Long distance power cable insulation resistance online monitoring method

Abstract

The invention provides a long distance power cable insulation resistance online monitoring method. The method comprises the following steps: respectively mounting a current transformer and a voltage transformer at the head end and the tail end of each phase of a three-phase power cable in advance; acquiring a main insulation leakage current which flows through the power cable of the phase according to the difference between a head end current value which is measured by the current transformer at the head end of the phase and a tail end current value which is measured by the current transformer at the tail end of the phase, and determining a reference voltage of the phase according to half of the phasor sum of the head end voltage which is measured by the voltage transformer at the head end of the phase and the tail end voltage which is measured by the voltage transformer at the tail end of the phase, wherein the head end current value and the tail end current value as well as the head end voltage and the tail end voltage corresponding to the head end current value and the tail end current value corresponding to each phase are synchronously measured values; calculating an insulation equivalent impedance value of the power cable according to the reference voltage of each phase and the main insulation leakage current which flows through the power cable of the phase, wherein the values of the equivalent resistance and the equivalent capacitance of the power cable of each phase can be further calculated.

Description

technical field [0001] The invention relates to the technical field of high voltage and insulation, in particular to an on-line monitoring method for long-distance power cable insulation resistance. Background technique [0002] With the rapid development of my country's economy and the continuous expansion of urban construction, the power load is also increasing, which makes the proportion of power cables used continue to increase. Among them, cross-linked polyethylene (XLPE) power cables have been widely used in transmission and distribution of various voltage levels in power systems due to their good insulation performance, thermal performance, mechanical performance and high power supply reliability. In the electrical network, and continue to develop to the field of high voltage, ultra-high voltage. Therefore, ensuring the safe operation of power cables is of great significance to the development of the entire power system and the national economy. [0003] High-voltag...

AI Technical Summary

Problems solved by technology

The loss factor (tanδ) method is to use the current transformer and the voltage transformer to measure the current flowing through the cable insulation and the voltage applied to the cable respectively, and then measure the cable insulation tanδ value through a digital measuring device; but due to the XLPE insulation tanδ The value is generally very small, making the method difficult to adopt

[0007] It can be seen from the above that due to the problem of cross-connection of the metal sheath and the problem of voltage drop in long-distance power cables, the existing on-line monitoring technology of power cable insulation cannot be applied to on-line monitoring of long-distance cables.

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