Secure protection against synchronous and asynchronous power swings

The world power demand is continually increasing particularly in developing countries. The development of the world infrastructure resulted in a great need of energy supply for areas distant from the generation centers. As a result, the interconnection via large power corridors is happening with the use of long distance transmission lines, even interconnecting countries and trying to optimize the use of existent energy sources. The transmission line protection can be affected by heavy power flows or stable and unstable power swings. The distance protection is adjusted to not operate due a system load, however this setting cannot allow for the power system impedance alteration (entering and leaving the protection zones) due to a transient power swing. For transient power swings it is therefore necessary to apply a supplementary power swing blocking so that the distance protection does not operate, under these conditions and allows an ideal power transfer in the whole system. Out of step conditions must however also be detected so that the system recovery measures can be initiated. The objective of the present work is to present the continuous power system impedence measurement and monitoring technique which can be used for a secure detection of synchronous and asynchronous power swings.