Limitations in Operation of High Voltage Equipment Resulting of Frequent Temporary Overvoltages
The Technical Brochure of JWG B1/A1/A2/A3.44 investigates operational limitations of high-voltage equipment caused by frequent power-frequency temporary overvoltages (TOV). Firstly, the network situations leading to short- and long-duration TOVs are systematically classified. It is shown that grid codes specify TOVs in a non-uniform manner and that long-duration TOVs (typically up to 1.05–1.10 × Um over seconds to minutes) are already observed in present transmission and distribution networks.
Using a typical overvoltage level UTOV = 1.05 × Um, the impact of recurrent TOV on insulation lifetime of different equipment is assessed. A continuous increase of operating voltage above maximal voltage for equipment Um can significantly reduce insulation life. Therefore, the introduction of higher…