PROCEDURE FOR THE PROTECTION AGAINST VOLTAGE BREAKDOWN IN A LOAD NODEOF AN ELECTRIC POWER SYSTEM

The new suggested procedure for determining the distance of the load node of an electric power system from voltage instability is of local character since for its operation it requires only two measurements inside the load node: the voltage phasor and the injected current phasor which it obtains from the phasor measuring unit (PMU) installed in the load node. With the two measurements in subsequent time intervals it calculates the change of the injected current and upon an adequate change of this current it calculates the BSDC criteria, which defines the proximity to the voltage breakdown. If the value of the criteria exceeds the lower predefined value, the algorithm or relay triggers adequate control signals to perform the predefined protective measures which can stabilize the operation of the electric power system. Nov predlagani postopek za ugotavljanje oddaljenosti bremenskega vozlišča elektroenergetskega sistema od napetostne nestabilnosti je lokalen, ker za svoje delovanje potrebuje le dve meritvi v bremenskem vozlišču: fazor napetosti in fazor injiciranega toka, ki ju dobi iz fazorskega merilnika PMU (Phasor Measuring Unit), instaliranega v bremenskem vozlišču. Z dvema meritvama v zaporednih časovnih razmakih izračunava spremembo injiciranega toka in pri zadostni spremembi tega toka izračuna kriterij BSDC, ki določa bližino napetostnega zloma. Če vrednost kriterija prekorači spodnjo nastavljeno mejo, algoritem oziroma rele sproži ustrezne krmilne signale za izvedbo vnaprej izbranih zaščitnih ukrepov, ki lahko stabilizirajo obratovanje elektroenergetskega sistema.