The Development of a HVDC SF6 Breaker

A 500 kV HVDC breaker prototype for switching load and fault currents up to 2200A was designed, manufactured, tested, and delivered to the Celilo terminal of BPA for field trial. This prototype breaker was a result of integrating a HVDC SF6 puffer interrupter into a Westinghouse LWER HVAC breaker. Detailed developments are presented here including design of the components, interrupter development??? A closing resistor and switch (R and S2) In order to interrupt the dc circuit, the interrupter begins to open and arcing occurs. As the interrupter continues to open its arc voltage rises, a result of both arc lengthening and increasing upstream pressure. When the arc and flow conditions have produced a high enough arc voltage, switch S1 is closed. This initiates a current diversion from the interrupter into the parallel capacitor Cs. This current diversion results in a current oscillation which grows. When its magnitude is large enough, a current zero is produced in the interrupter. As soon as the current zero in the interrupter is produced, the arc is extinguished and commutation of Io into Cs occurs. As the capacitor continues to be charged, the voltage across it rises to the selected clipping voltage of the ZnO, in ~ 1 ms. At this voltage the ZnO conducts; this prevents further voltage rise across the capacitor and the ZnO absorbs the dc line energy.