A method of measuring and displaying generator rotor angle

The equipment was designed for stability tests at Cliff Quay generating station. The method chosen was one which might, with some modifications, be suitable for permanent installation in any power station. The instantaneous angular position of the rotor is determined using photo-electric methods, and a reference voltage is derived from a voltage transformer connected either to the generator output terminals or to one of the station 132 kV busbars. The phase angle between these two electric signals is measured by a phase-sensitive detector using transistors, the d.c. component of whose output is used to drive a pen recorder having a high speed of response. The overall accuracy of the system is ± 6°. The photo-electric method has some disadvantages, and a magnetic method would be more suitable for long-term operation. Displaying rotor angle on a pen recorder is a very useful aid to the control engineer in determining whether his action is restoring generator stability.