Investigation of Partial Discharge Measuring Method via Coaxial Bonding Wire for Direct-buried Power Cable

Abstract

This paper describes a new method of measuring partial discharge (PD) via coaxial bonding wire for direct-buried power cable of which the sheaths at an sheath-insulated joint can be bonded at a terminal box, so-called link box, usually installed beside the joint but on the ground. When cable joints are directly buried under ground, it is difficult to use the conventional measuring method to detect PD, since it is necessary to install a PD detection sensor directly at or on the joint. For direct-buried cable line, the formation of sheath bonding for each joint can be usually determined at a link box that is connected to joint via coaxial bonding wire. The terminals of coaxial bonding wire at a joint are connected with sheathes of both sides of the joint, and the terminals of the other end of the coaxial wire are fixed inside the link box. This paper deals with the possibilities of measuring PD from the terminals of the coaxial wire. Some problems have to be solved when connecting a detection circuit to terminals of the coaxial wire, a) how to detect the PD signals from the coaxial wires high sensitively and safely; b) how to evaluate of the propagation attenuation of coaxial wire; c) how to do the measuring calibration for PD measurement system before detection. Some results of experiments simulating the cable conditions on side will be discussed. A practical PD measurement for this kind of direct-buried power cable conducted on site will be also introduced.