Common-mode monitoring signal injection device and cable insulation on-line monitoring system adopting same

Abstract

The invention relates to a common-mode monitoring signal injection device, a control method thereof, and a cable insulation on-line monitoring system comprising the injection device. The common-mode monitoring signal injection device uses a current transformer widely existing in a power distribution network to generate a monitoring signal with controllable frequency, does not need an additional monitoring signal injection power supply, and is easy to implement, low in cost and high in flexibility. The frequency of the generated monitoring signal is controllable, the cable insulation capacitance characteristic can be effectively amplified by selecting the relatively high monitoring signal frequency, the cable monitoring precision is improved, the voltage amplitude of the injected monitoring signal is reduced, and the measurement difficulty and cost are reduced; and the common-mode monitoring signal injection device injects the generated monitoring signal from the neutral point of the system transformer in a common-mode mode, normal operation of the load is not affected, and non-invasiveness is achieved. The cable insulation on-line monitoring system realizes on-line monitoring of the insulation state of the cable by measuring the size of the induced insulation leakage current.

Description

technical field [0001] The invention relates to the technical field of on-line monitoring of cable insulation state, in particular to an on-line cable insulation monitoring system, a monitoring signal generation module and a common-mode monitoring signal injection device used in the system. Background technique [0002] With the continuous increase of the operation time of underground cables in the distribution network, more and more cables have entered the aging period. Cable aging is often caused by the harsh operating environment and the thermal effect of load current, which will eventually lead to insulation breakdown and short-circuit faults, affecting the safe and reliable operation of the distribution network and causing huge economic losses. At present, most distribution network cables still adopt the method of periodic off-line maintenance, and the cables to be monitored need to be shut down, which affects the normal operation of the system, and the overvoltage test...

AI Technical Summary

Problems solved by technology

The main defects of this method include: 1) Since the cable insulation resistance is often as high as MΩ, the magnitude of the leakage current generated by the superimposed signal is small, and the measurement is difficult, resulting in low monitoring accuracy; 2) This monitoring method requires the installation of many additional Device, high cost, poor flexibility

Images