Effects Of STATCOM On Distance Protection Of Transmission Lines

With the raising of the power system, FACTS is more and more widely used in electric power system. STATCOM has such a good capability that can compensate reactive power effectively in the FACTS system. STATCOM has superior dynamic properties, it can improve the Voltage's modulate capability and the stability of the electric system, Further more, it can improve the transmit electricity capability of the circuit greatly, so it has been widely researched and used. At the same time, it caused a series of problems to the others equipments in electric system especially in normal working of electric protection equipment.This thesis studied the distance protect infection of parallel connect compensated STATCOM, discussed it from these aspect:(1) The function feature of FACTS, the classification of STATCOM, the choice of topology structure, Control strategy and digital models in all kinds states of high-capacity STATCOM;(2) Through much theoretical analysis both in working and fault states, The electric amount changing in the STATCOM line, improved that STATCOM probably can make any badness infection to electric protection equipment;(3) Use PSCAD/EMTDC software constitute the simulation model of 12 pulse waves doubling of STATCOM. In the other hand, through many Static var Compensator experiment with distance protection 110kV system, improved that the validity of STATCOM improved the voltage level of the power network connection point of junction, and can compensate reactive power effectively. When near the exit of the circuit protection happened with single phase to earth or three phases to earth fault, maybe cause distance protection skip a grade and overworking, can not to make sure the selectivity of the protection system;(4) It mentioned that some policies and methods matches the distance protection, changed to use variation relay instead of traditional relay, and from some angle such as transition resistance, increase burthen, to simulate STATCOM infect to the distance protection. From the conclusion we can see that STATCOM has superior modulation ability.