Case Study of Ht Reactor Failure

A booster pumping station (BPS) in South India with high power HT pumping motors reported sudden failures due to flashover of the current limiting reactors of the PF correction capacitor circuit. The pumping circuit has its own power factor correction capacitor circuits. The failures were reported repeatedly over three/ four days during December 2009. Extensive re-look on design aspects and simulations studies pointed out no major design issues. Finally it was concluded that the failures were due to the inherent design and workmanship limitations of the reactors itself to handle transient over currents during switching. To find out the specific reasons for such failures (which happened after three to four years’ of working), it was decided to undertake power quality studies. The longer duration period of logging at identified points it was noted that at a certain random periods , the voltage and current total harmonic distortions increases abnormally high. It was also noted that the predominant in harmonic content. Detailed investigations provided the reason for such random failures due to harmonic environment that too occurring at random intervals. This has lead to shunt resonance situation for the LC circuit resulting into the failure of the reactor. Larger sized current limiting reactors were found to be the best and economical solution in this case.

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