Researches On The System Of Hot-line Monitoring For XLPE Cables

The safe and stable running of the power system mainly depends on the reliability of insulation of high voltage electrical equipment. With the widely use of the XLPE cable in the native and international power system, the insulation monitoring of XLPE cable becomes more and more important. Because of the long experiment period and unreliable results, the traditional insulation monitoring technology in the power-off mode is being substituted by the on-line monitoring technology. The on-line insulation monitoring is a type of method in which voltage and current can be obtained from the monitored equipment in the power-on mode. Then we can calculate the parameter of the equipment, through which the insulation status of the equipment can be evaluated. Currently there are two main trends in the field of on-line monitoring: multi-functional and automatic on-line insulation monitoring system, portable insulation monitor. Basing on the theoretic analysis of AC superposition method, the hot-line test method for insulating performance of XLPE cable and the design of detecting instrument are introduced in this paper: making use of single chip machine with some peripheral circuits attached, making use of new technology of digital signal processing, we carry out a proper processing on sampled signal, then get the measured parameter needed, we make a comparison between the different methods and puts forward the gross structure of the device. In order to suppress the interference signals in field, the paper focus on the research of the signal sampling and the application of digital signal processing technology. Thus, the locked-in amplifier and compound digital filter technology are designed.The field experiment shows that the system could fulfill the requirement of monitoring for the insulation of the XLPE cable in power system.