A NEW BLOCKING PRINCIPLE WITH PHASE AND EARTH FAULT-DETECTION DURING FAST POWER SWINGS FOR DISTANCE PROTECTION

Any sudden change in the configuration or the loading of an electrical network causes power swings between the load concentrations of that network. In order to prevent the distance protection from tripping during such conditions, a power swing blocking device is often utilized. Conventional power swing blocking devices cannot cope with very fast power swings of up to 5 Hz/sec. This paper presents a new power swing blocking principle that has the ability to immediately clear the block when a fault occurs within the relay trip zone. This is demonstrated for extremely last swings ( greater than 5 Hz/sec) and even for two phase operation (during Single pole tripping). This new principle is in a form which can be implemented on an existing digital distance protection relay. Results are presented based on extensive simulation studies carried out on a typical 409 kV system, using the Electromagnetic Transient program(EMTP) software.