Simulation and measurement of the voltage distribution on high voltage suspension Porcelain insulator string under pollution condition

Satisfactory operation of suspension insulator strings is intimately related to the voltage distribution of the string. At operational voltage, the voltage distribution along insulator string is affected by stray capacitances, which causes a non-uniform voltage distribution. In addition, the performance of insulator changes by the accumulation of environmental pollution over its surface that will deteriorate by absorption of moisture sharply. In order to explain this dilemma clearly, a full equivalent circuit, which takes into account the insulator material properties and the stray capacitances, is derived from the Finite Element Method Based Software, which is implemented in the EMTP-ATP package to calculate the voltage distribution, power loss and the leakage current, flowing through the string with and without pollution under power frequency voltage. Finally, the simulation results of voltage distribution have been compared with experimental results, which were obtained in the High Voltage Laboratory. In experimental procedure, an attempt to form the pollution on the surface of the insulator has been carried out. For this investigation the dry pollutant on the insulator surface has been approached according to IEC60507, which has led to the resistance of pollutants. Then, the voltage distribution of clean and polluted insulator strings has been measured by sphere gap method.