Review and application of diagnosis methods for 22.9kV-y distribution systems

Maintenance method for 22.9kV-y distribution systems of KEPCO was improved from time base maintenance to condition base maintenance with adopting various diagnosis instruments. The typical diagnosis methods are IR(infrared) thermo graph, ultra sonic detection, VLF(very low frequency) test, TEV(transient earth voltage) detection. Diagnosis experience was presented and the results of defects analysis were also discussed. Firstly IR camera is useful to find out the insulation that has leakage current like cracked porcelain suspension insulators. Ultra sonic detector is good to locate where the surface tracking is taking place like contaminated polymeric insulators. Lastly TEV detection is helpful to diagnosis enclosed facilities such as switchgear and transformers.