A new fast protective device for high voltage series capacitors

Present overvoltage protection schemes for series capacitors have various limitations with respect to size, performance and impact of environmental hazards. There has for long time been a need for more compact and environmentally robust equipment. There has also been a need for a new type of protection scheme, which can limit the amount of MOV in order to reduce the overall costs as well as add new features to the series capacitor concept. A new type of series capacitor protection scheme, designated fast protective device has been developed. It is intended to operate in combination with a primary MOV in high voltage and extra high voltage series capacitor applications. This paper gives a background to general requirements on series capacitor protection schemes and the limitations of present equipments. The new scheme and its working principle are explained in some detail. The scheme has been tested in high voltage and high power laboratories and in a pilot installation in Hydro Quebec 315 kV network in Canada. The paper also explains some new series capacitor features, which becomes possible in the future using the new protective scheme