Research On The Impact Of SVC On Relay Protection For Transmission Line

Flexible AC transmission & distribution system technology(FACTS/DFACTS)could implement adjustment to AC transmission and distribution systems rapidly and flexibly, greatly improving the transmission lines Transfer Capability, damping system oscillations and improving power quality, etc. used more widely In power grid. Static Var Compensator (SVC) is the most widely used FACTS / DFACTS Controller, the electrical circuit of power systems is changed after SVC accessing network,Which inevitably affect the correct operation of protection devices,the power system security and stability will be threatened.There is less research on the impacts of the protection caused by SVC accessing network at present, Researching on the impact of fixed SVC on protection are of great theoretical and practical significance to guarantee the safe operation of power system. Therefore, this paper in-depth research on the impact of fixed SVC on line protection.The paper Introduced that FACTS/DFACTS technology played an important role in the modern power grid,good performance and compensation of reactive power and wide applications in transmission and distribution system are described, And SVC, research on working principle and the open and closed-loop control strategy, SVC models are based on voltage control , steady state and dynamic performance of SVC model are texted by simulation, the simulation results show that system voltage could be effectively regulated by SVC when the system fails.On the basis of depth analysis the SVC structure and control in this paper,Analysis is made on impedance characteristics of SVC, and on the variation patterns of the back side equivalent impedance as fault in front and rear protection on basis of fault component directional protection principle after SVC accessing grid. A formula is proposed on the relation between maximum sensitivity angle of fault component directional protection and compensation ratio of SVC. With a simple double-ended power supply system example,Analysis is made on the variation patterns of the back side system equivalent impedance angle by different compensation capacity, the same capacitive and inductive compensation are compared.Analysis is made on current characteristics of SVC in this paper, short-circuit model are made at the certain control strategies, the relationship between the output current and its own capacity, control strategies, the port voltage are analyzed on its short-circuit in the system, study on short-circuit characteristics of the grid with SVC, which show that SVC can improve the access point bus voltage and change the network short-circuit current on the system failure, the impact of upstream and downstream short-circuit current characteristics are obtained when the SVC access networkThe distribution network model with SVC is built based on RTDS (Real Time Digital Simulators), based on radial distribution network with current protection, the impact of current protection sensitivity and protection coordination with SVC accessing are analyzed, simulation results show the validity of the model and a basis for setting and configuration are provided for current protection in distribution network.