An investigation into the impedance characteristics of a synchronous generator under loss of excitation condition

Under loss of excitation conditions, a synchronous generator can sustain internal damage and system stability can be lost. The loss of excitation condition can be detected using a mho-type distance relay. In this work, a micromachine based turboalternator simulator was subjected to the loss of excitation condition. Tests were conducted with the field winding both open and short-circuited, and for various loading conditions. An investigation of the mho-type relay behaviour was conducted based on digital recording of the machine terminal voltage and current signals. Results show that adequate relay performance is obtained