Effect and Analysis of Partial Discharge in Cross Linked Polyethylene Underground Cable Insulation

Abstract

In the high voltage power system safe and reliable operation is the most important factor to consider. So pre-detection of fault in power equipment can be scaled and useful in the calculation of age of insulation, where aging causes the degradation in all solid, liquid and gaseous type insulation. One of the most widely used high voltage power equipment is underground cable whose aging detection can reduce the chances of complete breakdown. So partial discharge(PD)detection and analysis in underground cable described in the presented thesis. Now a days manufacturing process are highly developed, but there are many cracks and micro defects can’t be avoided. These micro voids are the main sources of partial discharge and electrical tree formation, which is the main cause of insulation degradation and reduction in life of insulation. In the presented work a MATLAB SIMULINK model is discussed to observe the PD pulse for a cylindrical type void. An experiment is performed to observe t he growth of electrical tree in cross linked polyethylene (XLPE) underground cable
insulation. Electrical tree characterization is the important phenomenon for estimation of age of insulation. So as to check the life expectancy of cable insulation study of electrical tree growth is necessary at different voltage for different duration of time and different distance of electrode arrangement. From tree length verses time, width verses time and area of tree spread verses time gives an idea for the aging of cable insulation and pre-breakdown information. As applied voltage amplitude and applied time duration increases electrical tree length and tree spread area increases that are observed under digital microscope with a needle to needle arrangement in sample preparation. A mathematical formulation for the electrical tree growth is also described and used in the modelling of tree in LabVIEW. The growth of electrical tree observed at different applied voltage and for different void arrangement also. In both experimental observation and simulation result the severity of insulation degradation increases with increases in applied voltage and number of void present.