An emergency strategy scheme based on conventional distance protection to avoid complete system collapse

An emergency protection scheme which prevents a system collapse in the case of extreme voltage instability is proposed. The scheme is based on conventional distance protection. The performance of the scheme was analysed using the NORDIC32 test system. The test case confirms that complete system collapse can be prevented when the relevant distance relays are given settings according to the proposed method. As a result the restoration time after a power system breakdown can be significantly reduced.