Measurement of Electric Field in Composite Insulating Material with Defects

Outdoor insulators play a vital role in the reliable operation of power system. These insulators can develop defects either during manufacturing or service. It is essential to identify and replace the defective insulators before they result in a power outage. Electric field measurement technique is a widely recommended method for the detection of defects as it can measure the variation in electric field. This paper presents measurement of electric field in composite insulating material in the presence of conducting defects. A commercially available electro-optic probe was used for the measurement. Conducting defects of different lengths were attached to high voltage electrode and a relation between the length of the defect and the maximum electrical field measured was obtained. Electric fields were measured for defects of different thickness on the surface and inside the material. Results show that the defects closer to the surface can be easily detected as they create a larger variation in the electric field distribution.