A phasor diagram based method to determine load conditions for load rejection tests for round rotor synchronous machine quadrature axis parameters determination

Abstract

This work introduces a phasor diagram based method to determine load conditions for which the round rotor synchronous machine armature current is on the quadrature axis. This load condition is necessary to determine synchronous machine quadrature axis transient and subtransient parameters from a load rejection test. Nowadays there is no analytic method to determine this load condition and, if a load rejection is to be performed to find the quadrature parameters of a round rotor synchronous machine, a time consuming trial and error procedure has to be done or special devices to measure the load angle must be installed. These necessities can represent a huge cost if the machine under test is a large power plant generator. The method here proposed is based on equations derived from machine phasor diagram and does not require a trial and error procedure or power angle measurement, simplifying the execution of the test. As a first evaluation of the method results, some load conditions are determined with the equations derived in this article and load rejections are simulated. The simulations results show that the method in fact determines the desired condition.