Improvement of thermal interruption capability in self‐blast interrupting chamber for new 245‐kV 50‐kA GCB

Current zero measurements are performed for 245 kV‐50 kA‐60 Hz short line fault (L90) interruption tests with a self‐blast interrupting chamber (double‐volume system) which has the interrupting capability up to 245 kV‐50 kA‐50 Hz L90. Lower L90 interruption capability is observed for longer arcing time although very high pressure rise is obtained. It may be caused by higher blowing temperature and lower blowing density for longer arcing time. Interruption criteria and an optimization method of the chamber design are discussed to improve L90 interruption capability with it. The new chambers are designed at 245 kV‐50 kA‐60 Hz to improve gas density in thermal volume for long arcing time. 245 kV‐50 kA‐60 Hz L90 interruptions are performed with the new chamber. The suggested optimization method is an efficient tool for the self‐blast interrupting chamber design although study of computing methods is required to calculate arc conductance around current zero as a direct criterion for L90 interruption capability with higher accuracy. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(1): 9–17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20743