| Transmission Line is one of the most important components of the power system. Along with the nationwide electric network construction has entered the new stage of taking ultra-high voltage, long-distance, large-capacity as the hallmark, in order to exert the capacity of power transmission of the lines fully, and raise the transmission capacity of corridor width per units line, the transmission lines of ultra-high voltage, long-distance, large-capacity increasingly used the transmission style of double circuits lines on the same tower. So studying and developing a protection with better performance, more reliability and fitting to the double circuits lines on the same tower has become an important task.At present, the domestic and overseas protections used in 500kV double circuits lines on the same tower usually are: split current phase differential protection and zero-sequence current differential protection constitute the main protection. Fast distance first-stage protection, interphase and ground distance second-stage and second-stage protection, four-stage zero-sequence direction overcurrent protection constitute the reserve protection together. However, when the main protection off line, the reserve protection have the problems of protection range shorten and lack of quick-acting characteristic, which cause by the mutual-inducatance. For the sake of solving this problem, the electric power company of Henan province presents the subject of using transverse differential protection in 500kV double circuits lines on the same tower systerm. This paper progress implementation research on this subject.This paper has analysed the selection element action behavior of the classical transverse differential protection in different accidents. Point out that when interphase fault happen, the fault delay phase measuring angle is affected by operating mode and fault location change most seriously. This paper advances using positive sequence voltage as polarizing voltage, and proves by academic analyse and emulation experiment that this method can adapt to larger range of different operating mode and has large protection range. The emulation experiment progress in different condictions, including different operating mode, different fault location, different fault types, metallicity short circuit and high resistance ground.when transverse differential protection is used in the double-circuit lines on the same tower system, it may mis-action in some states. This paper has studied these states and the corresponding closedown measures, including: Single line operation; after one circuit line trip off; double-circuit lines connects to two sects of bus bars and bus bars fault; any phases break. Besides, such as multiples-voltage closedown, as well as TV wire-interrupted closedown have also been studied. At the mean time, the transverse differential protection action logic diagram has been given.The overall scheme of the protection has been given in this paper. The constitution of the main protection and reserved protection, and the basic functions of the breaker protection have been introduced, either. In order to achieve tripping-by-phase and self adapting reclosing, we study how to cooperate between line protection and breaker protection, in the 3 / 2 breakers mode of connection. Through some examples, the information exchange between line protection and breaker protection and their action processes have been introduced detailedly. This paper grounds a theoretical basis for the developing of new style double-circuit lines protection. |
