Adaptive load encroachment prevention scheme for distance protection

In this paper, a new adaptive load encroachment prevention scheme based on steady-state security analysis and adaptive anti-encroachment zone (AEZ) is proposed. 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 the 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 can be verified through the test cases in this paper.