Results of full-scale stability tests on the British 132-kV grid system

The paper describes the results obtained from transient stability tests carried out on a section of the British 132-kV grid system during the summer of 1956. A 45 MW (56 MVA) generator was connected to the main system through a 150-mile line and faults of various types were applied with the generator on full load. The main purpose of the tests was to check how closely network-analyser results agreed with the actual performance. It was found that the agreement was, in general, very good, and some important information was obtained about the characteristics of cylindrical-rotor machines which should be of assistance in future analyser studies. It was also found that flux decay, even with voltage regulators, is a factor which alone could result in discrepancies between network-analyser studies and actual performance, but that this is largely compensated, when it is neglected, by the improving effects of damping, additional losses during faults and governor action. Stability was maintained with full load on the machine when the reactance of 150 miles of line was suddenly inserted between it and the system, provided that the excitation was sufficient for steady-state operation with the line. Reactive power consumed by the machine at the steady-state stability limit was about 15% higher than calculated values, owing to saturation effects. During asynchronous operation with open field up to 30 MW the slip remained very low.