Multi-terminal out-of-step protection system

From time to time a sequence of unexpected and often overlapping contingencies may lead to power system angular instability and even blackouts if not addressed adequately by means of an out-of-step protection system. This paper proposes the out-of-step protection system structure, which is based on generation sources electromotive forces vectors angle control. The protection system consists of several strategically located terminals, exchanging information in real time by means of a communication network. Terminals determine online the groups of coherent generators and choose the splitting boundary from a predefined transmission lines cut sets list. The protection system structure, the principles of operation and the possible IEC 61850 communication standard-based implementation are described.