Power swing indication signal determination method e.g. for power supply network

摘要

To obtain a signal indicating a power swing in electrical network, phase-currents and phase-voltages are scanned to form phase-current- and phase-voltage-sampled-values. A comparison of successive impedances is made in order to form a signal, possibly indicating a power swing. Current- and voltage-spatial vectors (i) are formed from the phase-current and phase-voltage scanned values of the positive phase-sequence system, and are then used to form associated active power magnitude (P') and a reactive power magnitude (Q'), with least squares estimation then used to form an active power measurement value (P) and a reactive power measurement value (Q). Using time-related positive phase sequence system resistance and reactance values (WR,WX), testing for abrupt changes is undertaken and with given missing abrupt changes a possibility of power swing signal is formed. With simultaneous presence of a possible swing signal and a power swing confirmation signal, the power swing signal (SP) is formed when the last formed positive phase-sequence system impedance value (Z) lies within the swing polygon (PPOL).