Impacts of TCSC on Switching Transients of HV transmission lines due to fault clearing

The thyristor Controlled series capacitor (TCSC) is one of the most promising components in flexible AC transmission system (FACTS).It can adjust the power flow and improve the stability of power system . TCSC´s different advantages can be classified as steady-state and transient ones. During a fault, TCSC can enhance power quality by limiting the current and help to keep the voltage as high as possible. In the operation of TCSCs, it is necessary to study side effects of their integration in power system. One of these studies is the effect of series compensation on Transients of line circuit breaker due to clearing a fault, here specially transient recovery voltage (TRV) is considered. The amplitude and rate of rise of TRV are two parameters which affect the CB´s capability to interrupt a fault current . It is important to evaluate the impact of series compensation on operation of circuit breaker (CB) and Transient Recovery Voltage (TRV) when clearing a fault because Circuit breakers can fail to interrupt fault currents when power systems have Transient Recovery Voltage (TRV) characteristics, which exceed their ratings. In other hand large and sharp TRV may be lead to damaging switch and capacitor . In this paper, first, different factors and conditions which can affect TRV in the line CB of a HV line including TCSC, is analyzed and then, the influence of protective operation of TCSC on TRV in different fault conditions is depicted and discussed Through time domain simulations. Digital simulations are carried out with PSCAD/EMTDC to analysis of transient behavior of power system. In the Transient analysis of power system TCSC is simulated considering its protection devices.