PROCEDURE FOR DETECTING VICINITY OF A TRANSMISION LINE TO VOLTAGE INSTABILITY IN POWER DISTRIBUTION SISTEMS

摘要

The new procedure for detecting vicinity of a transmission line to voltage instability in power distribuion systems is a local one, since for its operation it requires only measurements of local phase vectors, this means voltages and currents in all of the system relay points. The basic criteria for detecting the vicinity of a voltage instability are reactive power losses of the line. A change in reactive power flow is calculated from measurements of local phase vectors in two consecutive points of time. Based on this change the vicinity indicator of voltage failure is calculated, which at the point of the voltage failure reaches zero value. On its basis the protective algorithm has been defined. If the value of the SDI indicator is lower than the defined threshold, the relay sends commands for the implementation of predefined protective measures according to the corresponding command logic.