Coupling Capacitor Voltage Transformer (CCVT) Transient Surge Suppression

This month’s Featured Technical Paper is from the Proceedings of the 2017 International Conference of Doble Clients. The paper is titled: Coupling Capacitor Voltage Transformer (CCVT) Transient Surge Suppression.



Puget Sound Energy (PSE) implements a variety of transmission auto schemes in order to isolate faults on the 115kV transmission system. There are two significant ramifications with this standard design: 

  • a motor operated switch will close to energize a section of transmission line and 
  • motor operated switches will be manually operated to drop line charge or re-energize a section of line for maintenance purposes.

In both scenarios there are instances where a motor operated switch with either whips or arcing horns will be used to de-energize and energize a CCVT along with the section of transmission line being isolated. It is known that CCVTs will produce transients on the electric system. However, in 2015 and 2016 there were several substation projects which involved installing or making changes to a CCVT intended for line potential sensing. As the crews were working in the substations, arcing was observed on the control wires and the test switches of the CCVT as the 115kV switch would energize or de-energize the section of line with the CCVT. Several consequences were: visible arcing in the control house, restarts of the RTU, several communication modems were destroyed, and several RTU communication ports were no longer functional. 

This was observed at several locations and was deemed a safety issue. Therefore the investigation was started to better understand the issue and to develop a suitable solution.

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