On-site AC Dielectric Test for 220kV Long XLPE Cable

Abstract: Conducting AC dielectric test for completed cables can ensure reliable and secure operation of cable. Through comparison and discussion of a 220kV cable withstand voltage proposal, variable frequency resonant method is used, greatly reducing the capacity of test equipment. Moreover, based on its own features of the equipment, serial resonant parallel compensation method is selected. The combination of several reactors in serial and parallel enhances the feasibility of test equipment. In the test, many measures are taken to reduce the circuit loss and quality factor of test circuit. The on-site test proves that method of parallel compensation and serial resonant is workable to AC dielectric test for the cable.   

Key words:  AC withstand voltage, variable resonance, serial resonance, parallel compensation, 220kV long cable, quality factor     

Introduction

With rapid development of national economy and improvement of urban appearance, XLPE cable with high voltage class is widely used in the urban construction. The cables, which have undergone pre-delivery inspection, are likely to be damaged mechanically or installed defectively during transportation, storage, construction and installation. Hence, it is very necessary to conduct the acceptance test on site for completed cables. The AC dielectric test conducted for XLPE cables and accessories not only reduces the loss caused by faults, but also effectively ensures reliable and secure operation. The length of cables also increases. It is worthy of discussing how to carry out on-site withstand test for this kind of high voltage and long cables. Details of on-site acceptance test for a 220kV long cable are given in this paper.