Power angle relay to measure and respond to the power angle of a synchronous generator

A power angle relay to measure the power angle of a synchronous alternator, that comprises means to receive a reference voltage from some point in the power system to which the alternator is normally synchronized and an electric signal representative of the angular position of the shaft of the synchronous alternator and operable to combine the two to provide an indication representative of the power angle between the direct axis of the synchronous alternator and the reference voltage, the reference voltage being derived from a reference voltage waveform, said relay further including signal conditioning circuitry to receive the reference voltage waveform and the electric signal representative of the angular position of the shaft and operable to provide electric outputs, a phase locked loop circuit connected to receive one of the outputs from the signal conditioning circuitry and a phase angle measuring circuit connected to receive another of the outputs from the signal conditioning circuitry as well as outputs of the phase locked loop circuit and operable to combine the same to provide said indication.

A power angle relay to protect a synchronous alternator, that comprises, in combination, means to receive a reference voltage from some point in the power system to which the alternator is normally synchronized and an electric signal representative of the angular position of the shaft of the synchronous alternator and operable to combine the two to provide a power-angle signal representative of the power angle between the direct axis of the synchronous alternator and the reference voltage, means to process said power-angle signal to derive therefrom a measure of the power angle, means to compare the power angle with predetermined limits thereof, and means to provide an indication in the event that the power angle exceeds the predetermined limits, said relay further including memory means to permit storage of the history of the power angle.

A power angle relay to measure the power angle of a synchronous alternator, that comprises means to receive a reference voltage from some point in the power system to which the alternator is normally synchronized and an electric signal representative of the angular position of the shaft of the synchronous alternator and operable to combine the two to provide an indication representative of the power angle between the direct axis of the synchronous alternator and the reference voltage, said relay having memory means that continuously stores data representative of power angle but which can be made to inhibit further storage and to retain the previous data.