Evaluation of Circuit Breaker capability for re-ignition free operation of 400kV Shunt Reactor and 765kV Shunt Reactor with NGR using Controlled Switching Device

Shunt reactor is one of the key elements exists in Extra High Voltage (EHV) power system used for voltage regulation. The current drawn by reactor is of highly inductive in nature and due to this feature, it presents constraints in current interruption by circuit breakers. The current can resume after interruption if the rate of rise of dielectric strength (RRDS) of dielectric medium is lower than rise time derivative of the recovery voltage and can results in un-successful current interruption. Based on this consideration, minimum arcing time is prescribed by Circuit Breaker (CB) manufacturer. Evaluation of re-ignition free window for EHV 420kV 80Mvar shunt reactor has been carried out in this paper as per the procedure laid out in IEC-62271-100 and IEEE-035-017 with the help of PSCAD-EMTDC software package. The results are well supported by field implemented disturbance records of controlled switching opening operation. Effect of presence of surge arrester on Transient Recovery Voltage (TRV) has been considered and elaborated. The effect of presence of neutral grounding reactor (NGR) with 765kV Shunt reactor is also discussed in this paper. The presence of NGR tends to increase the peak of TRV peak and the same has been calculated through simulations, the field results are then discussed based on the re-ignition free window calculated as per IEC 62271-100. Optimum controlled switching helps in reduction of mechanical and electromagnetic stresses generated during random switching operations of reactor. The simulation results and field reports are in good agreement and controlled switching helps in meeting the opening targets within re-ignition free window with fair accuracy.