Abstract— Power cables are vulnerable to failure due to aging or defects that occur with the passage of time under continuous operation and loading stresses. PD detection and characterization provide information on the location, nature, form and extent of the degradation. As a result, PD monitoring has become an important part of condition based maintenance (CBM) program among power utilities. Online partial discharge (PD) localization of defect sources in power cable system is possible using the time of flight method. The information regarding the time difference between the main and reflected pulses and cable length can help in locating the partial discharge source along the cable length. However, if the length of the cable is not known and the defect source is located at the extreme ends of the cable or in the middle of the cable, then double ended measurement is required to indicate the location of PD source. Use of multiple sensors can also help in discriminating the cable PD or local/ external PD. This paper presents the experience and results from online partial discharge measurements conducted in the laboratory and the challenges in partial discharge source localization. Keywords—Power cables, partial discharge localization, HFCT, condition based monitoring. I. INTRODUCTION HE online partial discharge (OLPD) detection system in conjunction with suitable sensors can be successfully applied to accurately locate the PD initiation sites along the length of power cables [1, 2]. The principle of time-of-flight (TOF) measurement of the PD pulses along the cable is often utilized for this purpose. When a PD event occurs, two PD pulses travel outwards in both directions from the initiation site along the cable earth screen (and cable core), [3]. The main pulse, also known as direct pulse travels straight towards the measuring end while the second pulse known as the reflected pulse travels towards the remote end and is reflected back towards the measuring end. This technique is called ‘single- ended PD location’ and is the simplest and quickest way to provide PD mapping of cables. If both the ‘Direct Pulse’ and the ‘Reflected Pulse’ are identifiable, then location of PD initiation site is relatively simple when single-ended location method is employed. The acquired direct and reflected pulses would appear as in Fig. 1. Authors are affiliated with Saudi Aramco Chair in Electrical Power, Department of Electrical Engineering, College of Engineering, King Saud University, Riyadh, Saudi Arabia. (*corresponding author: e-mail: amkhan@ ksu.edu.sa). Fig.1 PD pulse train as seen from the measurement end In Fig. 1 the time difference between the direct and the reflected pulses is referred to as ΔT. The pulses will propagate progressively and will suffer attenuation and reflections and ultimately becomes less than the background noise level. The time that a pulse takes to reflect from the far end and return to measuring end is known as cable return time T r . This gives rise to a set of pulses of diminishing size, each spaced at the cable return time, T r . If T r for the cable length is measured then the location of the PD event is given as [4]: PD source location (pu of Cable Length) = (1-ΔT/Tr) (1) If the length of the cable is known then return time of cable can be found easily and hence PD localization can be done reasonably accurate. However, if the cable length is not known, use of time of flight method poses challenges to accurately localize the PD source. This paper presents the results of PD localization when the PD source is present at different locations. Moreover, the problems and challenges commonly faced during PD source mapping using online partial discharge non-conventional method are outlined in this paper. II. EXPERIMENTAL SETUP For studying the PD localization and to understand the challenges associated with it for long cables, a 500m long, 50mm 2 , 3 core, 15kv rated, XLPE cable was procured it was modified by inserting two heat shrink joints to make it a 1500m long single core cable Fig. 2 below shows the modified cable for this purpose and the available locations for placement of HFCTs for sensing the PD pulse. Online Partial Discharge Source Localization and Characterization Using Non-Conventional Method Ammar Anwar Khan, Nissar R. Wani, Nazar Malik, Abdulrehman Al-Arainy, and Saad Alghuwainem T World Academy of Science, Engineering and Technology International Journal of Electrical and Computer Engineering Vol:7, No:3, 2013 280 International Scholarly and Scientific Research & Innovation 7(3) 2013 scholar.waset.org/1307-6892/3536 International Science Index, Electrical and Computer Engineering Vol:7, No:3, 2013 waset.org/Publication/3536