Study Of Inverse-time Characteristic Of Microprocessor Distance Protection

The algorithms of microprocessor distance protection emulated and calculated in this paper are used to realize the inverse time characteristic of microprocessor distance protection.Microprocessor distance protection set is one of the most important protections for high-pressure transmission lines. When high pressure transmission line occurs fault, due to it's high voltage level, faults brings big impact to power system and users. The closer the faults occur, the bigger impact it brings. So it is very important to investigate the inverse time characteristic of microprocessor distance protection.This paper emulates all kinds of faults of transmission lines by using EMTP, and gets relative current and voltage sample values. Then many distance protection thoughts and algorithms are adopted to compare each inverse time characteristic, better arithmetic and set thoughts are got. Applying relative arithmetic to all kinds of faults and calculating off-line, We can master time-distance relation chart for all kinds of faults.Computation indicates: When transmission lines occur faults, the data window of protection algorithm consisting of prefault and postfault data at the same time has important significance. The following methods are useful to achieve the inverse time characteristic: Calculating impedance by using flourier in a full cycle, Calculating work voltage by using fault component, Calculating the torque created by a phase comparator or a magnitude comparator.