Research On Synthetical Test And Diagnosis Technology Of XLPE Cable Insulation

Cross linked polyethylene(XLPE)cable has gradually become the main product of power cable because of its good electrical and mechanical properties.A variety of reasons can cause some potential insulation defects of XLPE cable.If not timely find and eliminate these defects,it will bring a serious threat to the security and stability of power system.Compared with the current detection methods of cable insulation,it is found that there are many problems such as large volume and inconvenient portability.At the same time,the single detection technology can not make comprehensive and complete diagnosis of the insulation status of cables,which seriously affects the efficiency of detection.Based on this,put forward the organic integration of a variety of cable insulation detection technology,including 0.1Hz ultra low frequency voltage test,partial discharge test of oscillating wave voltage,measurement of dielectric loss tangent.A integrated test and diagnosis system for insulation of XLPE cable is developed.This article complete the hardware design of the comprehensive test system.The scheme is to replace the original high voltage DC charging power supply with ultra low frequency test power,so as to accomplish the task of applying voltage to the cable.At the same time,the function of the ultra low frequency test power controller is realized by the control unit of the oscillating wave partial discharge detection system.Thus the high voltage power supply of two sets of test systems and the combination of the two parts of the control system are realized.Besides,when oscillating wave voltage partial discharge test is carried out,the oscillating wave voltage and loop current are sampled synchronously for measuring and calculating the dielectric loss tangent.Based on the Labview environment,a comprehensive test system software for cable insulation is developed to complete the control and data acquisition,processing and analysis of the whole test process.From the function,the software can be divided into two parts: the test front control and the test data analysis and processing.The test front control part provides the human-machine interaction interface.It can set relevant parameters in the test process,manipulate the test process,and observe the direct results in real time.The analysis and processing part of the test data is mainly used for detailed analysis of the data stored in the test,so as to diagnose the insulation state of the cable and locate the defect.Finally,experiments were carried out to verify the feasibility and reliability of the system,including the equivalence between the ultra-low frequency breaking-down test and the power frequency breaking-down test,the partial discharge test and partial discharge location of the oscillating wave under the integrated test system.