Distance protection is widely used in modern power systems because of its numerous characteristics and merits. Distance relays determine the apparent impedance based on voltage and current measurement, and operate when the apparent impedance falls within operating zones for an appropriate amount of time.
In this paper, Ming Jin (Areva T&D Inc, USA) and Tarlochan S. Sidhu (University of Western Ontario, Canada) propose a new adaptive load encroachment prevention scheme based on steady-state security analysis and adaptive anti-encroachment zone (AEZ). The new scheme identifies the vulnerable distance relays through real-time security analysis. Selected dual contingencies are included to reflect the influence from the ‘hidden failures’ of protection systems.
Effective measures are taken to improve the computational efficiency. The AEZ will be designed online, to prevent undesired tripping if the analysis shows that a distance relay may suffer the load encroachment for a particular scenario. To ensure the dependability of the protection system, the AEZ will be applied only when its introduction is necessary. The effectiveness of the new scheme is verified through reported test cases.
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