Evaluation of controlled energization of shunt reactors for minimizing asymmetric DC component of charging current with circuit breaker having pre-insertion resistors

Generally, Controlled Switching Device (CSD) is used during de-energization as well as energization operations of shunt reactors. However, for substations configured with One-and-Half Breaker (OHB) or line connected to non-switchable reactor scheme, the Pre-Insertion Resistor Circuit Breaker (PIR-CB) might be used during switching of shunt reactor. This paper presents optimized controlled switching strategy to minimize the level of asymmetric dc component of charging current during energization of a shunt reactor using CSD with PIR-CB. This is achieved by optimizing the insertion instant, value and Electrical Insertion Time (EIT) of PIR. The validity of the proposed technique has been evaluated by generating a large number of simulation cases in PSCAD/EMTDC software package by changing rating & configuration of shunt reactor, EIT, insertion & removal instant and the value of PIR. The simulation results suggest that the proposed methodology maintains the level of asymmetric dc component in charging current of the order of 1.02, 1.11, 1.11 p.u. for grounded star (Yg), un-grounded star (Y) and delta (Δ) configuration of shunt reactor. At the end, field results of energization of 240 MVAr shunt reactor with PIR-CB for line application at 765 kV have been presented which clearly depicts mitigation of asymmetric dc component.