Measurement and Calculation of Potential Shifting Current in ± 800kV HVDC Converter Station

摘要

The reliable and stable operation of ultra HVDC transmission system contributes to the safe operation of the power grid, thus to carry out live working is of great significance in converter station. Shift of potential is the most important aspects of entering equal-potential. At the moment of shift of potential, the strong arc and large pulse current will occur between the bus and operation worker. Research on the characteristics of the potential shift current is benefit to take appropriate protective measures. Based on NI9165 wireless data acquisition card pulse current measurement system was applied to measure potential shifting currents during the process of entering +800 kV DC converter station bus. According to the characteristics of access to DC converter station polar bus equal-potential, potential distribution and capacitor between worker and polar buses were studied using the electromagnetic analysis software in the process of entering the equal potential. Equal potential transfer analysis model was built according to these parameters and potential shifting current were calculated in UHV DC converter station. Entering potential shifting current pulse is of the highest value 150 A with positive and negative polarity pulse, pulse width for dozens of μs in the process of entering equal-potential. Potential shifting current simulation calculation results is that maximum is 190 A, pulse width of 10 μs. Calculation and measurement results show that the potential shifting current UHV DC converter station is far less than UHV AC lines, such as potential in the process of potential shifting current pulse is mainly caused by the arc extinguish and renewed between bus and workers repeatedly, and workers should be quick into and out of the equal-potential during contacting and out of a live conductor, in order to avoid arc burns damage to workers, potential shifting bar is recommended to use during into and out of the bonding process.