A Methodology to Prevent Failure in Single Pole Reclosing Operations

Abstract

After a phase to earth fault in a transmission line, opening of the circuit breaker poles at line extremities interrupts the fault current in the faulted phase. However, due to coupling between phases there is still a residual current through the electric arc, which is then denominated secondary arc. Interruption of the secondary arc defines if single pole reclosing operation will succeed. Nowadays, studies evaluate the likelihood of secondary arc interruption to define application of single phase reclosing. By several reasons, the secondary arc interruption may not occur leading the single pole reclosing operation to a failure. In this case, the circuit breaker pole has to open again and that depletes the energy stored in the operating mechanism. As the rated operating cycle of a fast reclosing circuit breaker is O – 0,3 s – CO – 15 s CO, a failure in the first reclosing shot makes necessary an interval longer than 15 s to perform a second reclosing shot. The methodology presented herein establishes a verification beforehand if a single pole reclosing will be successful. With the secondary arc still active, the single pole reclosing is blocked and the system proceeds to a three pole reclosing. Blocking of the first reclosing shot keeps the energy stored in the operating mechanism and the three pole reclosing shot may proceed with an interval of 300 ms.