the meaning of Operating cycle O-t-CO-t-CO for MV breaker 1

[PAP]

Hi all
I 'd like to ask the implied meaning of operating cycle "O-t-CO-t-CO" with t range from 0.3s to 3 min , how the difference for varying of the interval time (fast cycle/slow cycle).

Thanks all for your help..

PAP

 

[jnims]

O-t-CO-t-CO is the reclosing cycle for fault interrupting equipment (e.g., a power circuit breaker). "t" is the dead time between operations. If a distribution circuit has a permanent fault, the relaying trips the breaker open (first O)and after a programmed time delay (first t), closes or reenergizes the circuit (first C). Since the fault did not go away, the protective relaying again trips the breaker open (second O) and stays open for the programmed delay (second t) before closing (second C). Since the fault is still hanging on, the relaying trips the breaker open for the final time (third O) and stays open until the breaker is manually closed.

A typical distribution reclosing cycle is O-.3s-CO-15s-CO. It is also not unusual to add another attempt to the reclosing cycle (e.g., O-0.3s-CO-15s-CO-45s-CO). The selection of dead times depends on a number of factors. For example, some interrupting devices have a lower than nameplate interrupt rating for non-standard reclosing cycles.

See IEEE Standard C37.010 for details