Seminar
Zenon   A.
Achillides
University   of   Cyprus
14 th  April 2010, 17:15 – 18:15
Room ΠΤΕΡ – Ε111, Old Campus, University of Cyprus
Abstract:
Ensuring a reliable electric service to industrial, commercial and residential customers is becoming an important parameter for every electricity company due to the increased demand from the customers for less downtime, high productivity and reduced maintenance cost of machinery caused by unscheduled frequent interruptions due to underground power cable failures. The presence of partial discharges (PD) is one of the most prominent indicators of defects and ongoing degradation processes of electrical insulation. As a high percentage of failures are associated with
PD, the need for the classification, extraction and evaluation of PD signals is essential. For the above reasons, an electrical model of a breakdown void, modelled, as part of the power system is more than a necessity.
The capacitive network representation of the void (model) long been used for the study of the transients generated by a breakdown void. As an alternative to the capacitive representation of the void (model) the induced charge concept has been introduced expressing strong criticism against the capacitance modelling of void.
This presentation discusses and argues this criticism and exploits the potential and weakness of the classical capacitive representation of voids from a theoretical point of view and proposes an improved version of the classical capacitive model and two new capacitive models for voids: a) A model based on the induced charge concept for streamer inception b) An advanced capacitive model of void based on streamer concepts. Furthermore, in this presentation the geometrical and physical parameters governing the classical capacitive model of void (improved version) and the two proposed models are calculated by utilizing the classical electromagnetic theory concepts of streamer breakdown mechanism and gas discharge physics.
Finally, the three models are employed to replicate the transients (PD signals) along the core of a typical medium voltage cable from a breakdown void under real time power network conditions .

Biography:
Zenon Achillides is from Nicosia, Cyprus. He is a Senior Engineer at the Electricity Authority of
Cyprus (EAC). He received the B.Eng. degree in Electrical and Electronic Engineering from Brunel
University in 1992, and the M.Sc. degree in Electrical Power Engineering from UMIST in 1993. He is currently a Ph.D. student in the Department of Electrical and Computer Engineering at the
University of Cyprus. His research interests include the physics and understanding of PD, signalprocessing techniques applied to power engineering, renewable energy sources, power quality and electromagnetic fields.