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 n etwork. In order to prevent the distance protection from tripping duri ng such conditions, a power swing blocking device is often utilized. C onventional power swing blocking devices cannot cope with very fast po wer swings of up to 5 Hz/sec. This paper presents a new power swing bl ocking principle that has the ability to immediately clear the block w hen a fault occurs within the relay trip zone. This is demonstrated fo r extremely last swings ( greater than 5 Hz/sec) and even for two phas e operation (during Single pole tripping). This new principle is in a form which can be implemented on an existing digital distance protecti on relay. Results are presented based on extensive simulation studies carried out on a typical 409 kV system, using the Electromagnetic Tran sient program(EMTP) software.