A novel on-line cable pd localisation method based on cable transfer function and detected pd pulse rise-time

This paper presents a novel Partial Discharge (PD) localisation method, based on PD pulse Rise-Time and Transfer Function (RTTF), for use in on-line cable PD monitoring systems. This is based on the change in rise time as a function of cable length along which a PD pulse has propagated. A comparison with four other well-known location techniques, i.e. Time-Domain Reflectometry (TDR), Phase difference, Arrival Time Analysis (ATA) and Amplitude-Frequency (AF) mapping has been made and presented. Analysis shows that the TDR and Phase difference methods, although requiring a single measurement point, are only applicable to short length cable systems as both incident pulse and reflected pulse should be observable when it reaches the detection point. On the other hand, the ATA and AF mapping, which can be applied to longer cable systems, need to install detectors at multiple points and detect synchronously. In comparison, PD localisation by the proposed RTTF method, which requires detection of the incident pulse at only one measurement point, can be used to localise a PD source which is further away from the PD detection point than other methods and can be used in on-line PD monitoring systems. As on-line PD monitoring sensors commonly comprise of a high frequency current transformer (HFCT) and a high-pass filter, the rise time of detected PD pulses depends on the attenuation of the cable, the HFCT used and the filter applied. Simulations of pulse propagation in a cable and PD monitoring system are performed, based on analyses in the frequency domain using the concept of transfer functions. Results of RTTF from the simulations have been verified by laboratory experiments and on-site PD measurements, which provide evidence that the RTTF method is a very valuable and useful PD localisation technique.