Proteetion Criterion Study Of EHV Transmission Lines Based On Nature Frequencies

With the increasing of EHV(Extra High Voltage) transmission lines, the contradiction between the reliability and rapidity of the traditional protection due to its special conditions and requirements is urgent need to resolve, so it is necessary to search for a range suitable protection configuration for the EHV transmission line. This paper describes the concept of the nature frequencies, and analyzes them in a variety of short-circuit types. Refer to the amplitude characteristics and distribution characteristics of nature frequencies components, a phase selection program based on nature frequencies is build; refer to the characteristics of nature frequencies and the frequency interval, protection criterions based on nature frequencies are constructed; when the nature frequencies is very large, the presence of bus capacitance will make the nature frequencies localized, then a fault location method based on nature frequencies can be constucted with the frequency interval. On this basis, the paper discusses further the impacts of the transition resistors, series compensation capacitors and shunt reactors on the phase selection program, the protection criterion and the fault location method, and gives the corresponding countermeasures.