On-line Monitoring System For The Insulation Of Cable Based On AC Component Method

With the development of science and technology, electricity is very important both in daily life and in the production. Therefore, transmission security is increasingly important. XLPE cable plays an more and more important role in the transmission of electricity power.With the extensive use of XLPE cable, the accident such as breakdown of cable is increasing day by day. So judging the situation of cable insulation is concerned to be solved urgently in the electric power department. The traditional method is off-line detection, but this method requires the power outages, this will bring a lot of inconvenience to people's production and daily life, and this method will bring some damage to the cable insulation, and the degree of damage can't be predicted. Thus, on-line testing is getting more and more attention. On-line monitoring can judge the insulation of the cable in real time, so we can avoid problems such as the breakdown of the XLPE cable. Japan and other developed countries have made a promising research result in on-line monitoring technology, however, domestic research in this area is still in the initial stage.This paper introduces the development and the main methods of on-line monitoring, and then we introduces the cable water tree in detail. Through the comparative analysis, we finally determined to develop the on-line detection system based on the AC superposition method, including the lower machine and the upper machine. The lower machine is used to collect and manage the relevant signals, including superposed power source, I/V conversion, amplifier, filter and signal collection module. In order to avoid the influence of the external disturbance to the measurement, the system makes a good package for the lower machine. The upper machine is used to display the measured data in real time. We use LabVIEW to design the HMI interface, and in order to make the data and waveform more accurately, we add the software filter.In the testing process, part of the experiment data is collected, and the feasibility of the method and the practicality of the system has been testified, this paper has a certain reference value for improving the detection system and further research.