Results of stability tests on an underexcited 120 MW generator

The paper is primarily a factual account of stability tests carried out by the Central Electricity Generating Board on a 120 MW turbogenerator at Northfleet power station. The tests were carried out with the test generator operating at leading power factors, and the generator was connected to the main body of the system by a high-impedance transmission link to simulate the situation in which a large coastal power station might be required to operate on the CEGB´s system. The results of 2-phase-to-earth-fault and 3-phase-fault tests are presented, one of which resulted in instability of the test generator followed by automatic resynchronisation. The perform ance of the auxiliary system during the fault tests is shown, as also is the behaviour of the turbine and governor. Since the tests were done at leading power factors, particular attention is given to the generator parameters in the quadrature axis. Special tests were done to investigate these parameters, and the results of these tests are also given in the paper.