EVALUATION OF REACTANCES AND TIME CONSTANTS OF SYNCHRONOUS GENERATOR

Abstract

For any power equipment the control system and protection system plays an imperative role as the dependency on the power equipment in any industry will be very high. Thus for the Generator the Reactances and Time Constants becomes controlling parameter and hence protecting it is necessary for prolonged usage. In general reactance shall be defined as "non-resistive component of impedance in an AC circuit, arising from the effect of inductance or capacitance or both and causing the current to be out of phase with the electromotive force causing it". In other word it can also be defined as the imaginary part of the impedance in any power circuit. There are various Reactances and Time Constants which contributes during the selection of control systems and protection scheme for any Generator. Therefore practical evaluation of those parameters shall also be super critical same as those are by calculation. More accurate measurement or the calculation of reactance shall certainly give us more stabilized error free system and hence ensuring a healthy control system. As there are different tests or different methods to measure and calculate the Reactances and Time Constants, in this context we are considering Line to Line fault (L-L fault), Double line to Ground fault and Sudden three phase short circuit fault to determine the Negative Sequence reactance, Zero Sequence reactance, Sub-transient and Transient reactance and time constants respectively. The fault condition will be demonstrated with the 40MW, 11KV, 2624A, 4pole, 50 Hz synchronous generator and above mentioned parameters are calculated based on references available.