TEV 검출에 의한 수배전반의 절연진단에 관한 연구

Abstract

Switchboard is a major power facility that is equipped for electricity distribution, switching, metering, and diagnosis. The modern society is highly relies on electrical energy and power outage may cause great economic and technical losses. As a result, it is necessary to diagnosis the condition of switchboard to ensure its reliable operation. During the operation of power apparatus such as transformers and circuit breakers, partial discharge(PD) may occur due to electric field concentration or insulation deterioration. Accompanying with PD, the transient earth voltage(TEV) will propagate along the metal or ground surface of switchboard. In this paper, for the purpose of insulation diagnosis of switchboard and related power apparatus, a TEV sensor was designed and fabricated for on-line PD detection. The insulation defects that cause insulation breakdown in switchboard were classified into protrusion on conductor, protrusion on enclosure, and free particle. The simulated TEV experiments were carried out and the characteristics of TEV sensor were analyzed. The fabricated TEV sensor could detect the signal with a frequency range from 1MHz to 100MHz and sample PD signals with a response time less than 8ns. In addition, the detection sensitivity depending on apparent charge and sensor type were studied. It was verified that the sensor with a diameter of 70mm and a thickness of 1mm was optimal for detect PD with a magnitude of 10pC∼100pC. The sensor used for application and evaluation had a sensitivity of 1.2 mV/pC. The electrical detection method specified in KS C IEC 60270 is a reference of PD signal acquisition, however, it can not be used for on-line detection of switchboard. The TEV sensor is a non-electrical method that can obtain same discharge patterns as the electrical method and overcome the limitations of existing method. The TEV sensor proposed in this paper had the optimal detection sensitivity and economic advantage, which can be used for condition monitoring and asset management of switchboards.