Voltage transformer ferroresonance in cogeneration substation

An incident in which the series grading capacitance of a 230 kV circuit breaker interacted with the magnetizing reactance of a voltage transformer causing overvoltage and eventual failure of the voltage transformer is described. It is shown that this incident, including the damaging overvoltages, was successfully simulated on a digital computer. Using the same model, proposed solutions derived from transmission experience were evaluated. The most effective solution was applied to the substation circuits and measurements were taken during initial circuit breaker energization and deenergization. Measurement results are compared with analytical results