Experiences in nonconventional partial discharge measurement for gas-insulated substation in Thailand

Nowadays, nonconventional partial discharge (PD) measurement has become essential for diagnosis the high-voltage insulation condition. The nonconventional PD measurement not only uses for periodic assessment but also uses for commissioning test after transportation and installation. This paper focuses on nonconventional PD test techniques using Ultra-high frequency (UHF) sensors, acoustic sensors and light detection sensors for gas-insulated substation (GIS) commissioning test. Fundamental defects found in GIS: (1) Hopping particles (2) Fixed protrusions (3) Floating potential and (4) Voids are described. Then, explanation about how to detect such defects by using UHF, acoustic and optical methods. Afterwards, PD commissioning tests were performed with three 230 kV electricity generating authority Thailand (EGAT) GISs, i.e., Phayao EGAT GIS, Lamphun 2 EGAT GIS and North Bangkok EGAT GIS. The PD signals due to hopping particle were found by using UHF sensors at Phayao and North Bangkok EGAT GISs. The acoustic PD test technique was used in Phayao EGAT GIS to locate such particles. In case of Lamphun 2 EGAT GIS, by using UHF measurement, PD signals were found due to tracking caused by flashover on the cone insulation surface. Later, light detection sensors were used to detect the PD location. As a result of studies, its clearly guarantee the powerful accuracy and efficiency of nonconventional PD measurement by the combination of UHF and acoustic technique including light detection sensors.