| 摘要 |
Method for preventing an electric alternating current generator from falling out of step. According to the invention a transformer (TR) with controllable phase shift ( alpha ) is connected between said generator (G) and an a.c. network (N). Sensing members (TG, SC, INT1) form a measure of the load angle ( delta ) of the generator (G) and its rate of change (d delta /dt). The attainment of a predetermined point, suitably the maximum point, of the power-load angle characteristic of the generator is sensed by means of a differentiating circuit (DM) and level detecting (ND1) means. The attainment of this working point initiates a change of the phase shaft ( alpha ) of the transformer with the same rate as the rate of change (d delta /dt) of the load angle ( delta ) of the generator. Sensing members (ND2) sense when the load angle velocity has dropped to a low value, preferably zero, whereupon the change of the phase shift of the transformer is interrupted. In this way, the risk of the generator to fall out of step is effectively prevented for certain types of faults, for example short-circuits in the a.c. network. |
