Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

critical clearing angle
(1) following a balanced three-phase fault at the stator terminals of a synchronous machine, the maximum value of the angular position of the rotor prior to the removal (clearing) of the fault such that the rotor will obtain synchronous speed without slipping poles following the removal (clearing) of the fault. The corresponding time for the rotor to achieve this angle is specified as the critical clearing time.
(2) the largest allowable angular deviation from synchronism that may be borne by a power system such that the system remains stable: the edge of instability.