Design And Realization Of Insulation Monitoring And Evaluation System For High Voltage XLPE Cables

XLPE cables have been used in HV power network more and more extensively. Partial Discharge is the main cause for insulation failure of power cables. Partial Discharge detection and location can show potential failure of power cables and guarantee safety and reliable operation of the power system.This paper designs the structures of the detection and evaluation system, and determines the hardware design of the system. It includes parameters determination of the detection impedance, calculation about power frequency signal and high frequency signal on detection impedance, parameters design of amplifiers, circuit design and analysis and parameters establishment of 2nd-order lower-pass active filter, and DSO selection as a data acquisition device.Then this paper designs the software part of the system. The whole software is developed on the base of VB platform. It integrates the withstand voltage test , PD detection and failure location technology, It mainly includes sampling and saving of signals, handling of PD signals, and spectra such as two-dimension, three-dimension and sine and so on. And it can locate the failure position. Four key software techniques are introduced in this paper: communication between PC and DSO, mixed programming of VB and MATLAB, access of VB to database and application of wavelet de-noising technology. Parts of source code are introduced in this paper.In the end, the paper presents the detection and evaluation results of cables with insulation failure. The results show that the system can operate well and has good spectra characteristic, so it can be effectively used to evaluate and locate insulation failure.