Experimental Study on Secondary System Grounding of UHV Fixed Series Capacitors via EMI Measurement on an Experimental Platform

In isolating the disconnecting switch of ultra-high voltage (UHV) fixed series capacitors (FSCs), electromagnetic-interference (EMI) problems arise on the secondary-side protection and control devices. If the platform-mounted high-potential secondary system is not properly grounded, malfunction or damage to EMI-vulnerable devices may follow. This paper focuses on high-potential measurement and characterization of EMI in the secondary side of UHV FSC. A life-size experimental platform was built at first, and a corresponding high-potential platform-based measurement system was developed. Then, by isolating the disconnect switch in the experimental circuit, the common-mode (CM) voltage, differential-mode (DM) voltage, and current under five different conditions of secondary system grounding were obtained. In addition, EMI characterization was described and analyzed, and statistical distribution was given. Finally, several proposals based on EMI data and characterization were presented to shed light on designing and engineering UHV fixed series capacitors in addressing EMI problems.