Effects of Lightning bolt on Power system: A 220kV double circuit parallel grid power transmission line-1 and line-2 were supplying to an integrated steel plant with a maximum demand of 500MW. Each 220kv grid incomer PCC was connected to 2sets of 155mva, 220kv/33kv grid transformers. Power Quality measurements were carried-out at the common 33kv secondary bus, wherein all four grid transformers were connected in parallel. A bolt of lightning struct at the nearby 200kv grid substation, a few KM away from the steel plant, blasting a 220kv circuit Lightning Arrester (LA) at line-1, and tripping it instantly.
Line-2 was healthy, but being in parallel with the lightning struck line-1, faced a momentary voltage sag problem as recorded in the waveform signature analysis, and recovered within a few milli-seconds. The Power Quality effect at a few KM away at 33kV downstream of the steel plant, which then had in operation one Siemens Germany supplied, 190mvar Static VAR Compensation (SVC) System, comprising of a 190mvar Thyristor Controlled Reactor (TCR), and a combination of 180mvar Net Capacitive harmonic filters distributed among 50mvar in 2nd, 30mvar in 3rd, 30mvar in 4th, and 70mvar in 5th harmonic filters.
The incident gave rare opportunity for online efficacy testing of a SVC system, BY INJECTING A SHORT-TERM VOLTAGE SAG AT ITS BUS TRANSFORMER'S UPSTREAM. The SVC did not trip, on the short-term voltage sag, as shown in the recorded 3phase voltage waveform signature analysis graph. Neither did 150mva, 33kv/ 1120v AC EAF transformer, or any other equipment trip.