1999 zyxwvutsr Conference on Electrical Insulation and Dielectric Phenomena Development of Partial Discharge Model, Simulation and Measurement Nikolay P. Kolev Technical University of Sofia English Language Department of Engineering 8 KI. Ohridski Blvd., Sofia-1000, Bulgaria Michael G. Danikas Democritus University of Thrace Dept. of Electrical and Computer Engineering 67100 Xanthi, Greece N-Kolev@,vmei.acad.bg mdanikas@xanthi.cc.duth.gr Elissaveta D. Gadjeva Technical University of Sofia Department of Electronics 8 KI. Ohridski Blvd., Sofia-1000, Bulgaria egadjeva@vmei.acad.bg Abstract In cases, when there are electrically weak areas in solid dielectric materials (most often gaseous or liquid inclusions), partial discharges (PD) can be measured when voltage is applied. Partial discharges cause degradation in insulated materials. The investigation of insulated material behavior under electrical stress and the data obtained from PD measurements provide the possibility to predict dielectric breakdown. PD measurements are affected by electrode arrangements and by measuring circuits (MC). It is very important to investigate the relation between experimental PD data, electrode arrangement and the elements of measuring circuits applying computer mode Is The present paper considers PD behavior of polyethylene voids. Various models have been built using special software tools for analogue design and simulation. The results obtained have been analyzed and discussed in order to assess the influence of various types of measurement circuits. The data obtained from the model have been compared with the experimental results from polyethylene samples with artificially introduced cylindrical voids subjected to PD. The electrode configuration used is plane-plane, and electrodes are parallel to the cylinder ends of the void. The parameters of the models correspond to the parameters of the experimental set-up. Introduction Generally direct zyxwvutsrqp ' measurement of partial discharge characteristics of in the volume of the testing object is impossible at the site of PD origin. Areas with internal PD are coupled to the surface of the test object by the Nikolay R. Gourov Technical University of Sofia Department of Electrical Measurements 8 KI. Ohridski Blvd., Sofia-1000, Bulgaria nrg@vmei.acad. bg partial capacitances of the dielectric and PD can be detected by means of voltage fluctuations at the specimen terminals caused by them. These fluctuations result in current pulses taking place in the circuit connected to the tested object. When electrical partial discharge measurements are performed, the tested object is connected to some kind of measurement circuit. The arrangement and parameter !values of additional elements of this circuit can influence experimental results The electrical circuit illustrating the principle of PD measurements is shown in Fig. 1. ' I Z vs t Fig. 1 Electrical circuit illustrating the principle of PD measurements In this circuit V, is a high voltage zyxw AC source with network frequency, Z is a lowpass filter and C, is a coupling capacitor. The tested object TO is represented by its equivalent capacitance zyxwv Co. If the voltage V, is increasing and there are electrically weak places in TO, PD activity can be observed at certain voltage levels. This activity results in a high- frequency pulse circulating current I(t), which flows through the capacitances C, and Co. The flowing of this . 0-7803-5414-1199/$10.00 1999 IEEE 214