Electrical Failure Analysis

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Electrical Failure An Electrical Arc Furnace was facing Electrical Failure from power system harmonic resonance. Failure analysis simulation & electrical design for prevention. Abstract: An Electrical Arc Furnace near a hyperactive railway traction line was facing electrical failure from an unusual power quality harmonic distortion problem. The Gigantic 22kA copper bus bar used to overheat visibly red-hot, vibrate audibly loud loosening nuts and bolts and wear out affected plates. In-addition, it frequently encountered other harmonic problems like bulging and blasting of detuned capacitor, motor overheating and failures, HPMV lighting ballast failures, 33kv fuse blowing and overheating of the Electric Arc Furnace transformer. An on site power quality harmonic analysis revealed an unstable grid supply zone which was supplying to the plant. It was tending towards a series resonance. A harmonic solution was designed. A 33kv harmonic filter was installed at the plant's 33kV grid incomer. Its performance monitored for a year and no electrical failure occurred. The installed passive tuned harmonics filter resoled all power quality harmonic problems due to power system resonance and the associated power surge. It eliminated electrical failure and equipment tripping. Furthermore, the improved operative power system conditions facilitated increased productivity, substantially, with congruous reduction in specific energy consumption (SEC) in terms of kWh/ Tons of iron alloy produced. II. INTRODUCTION The factory manufactures Pig Iron which is an intermediate product manufactured by smelting iron ore with high carbon fuel such as coke usually with limestone as flux. As seen in Fig.2, the ingots are produced at many a branching structures which are laid in sand at right angles to its central channel called the runner wherein the liquid metal is poured directly from the bottom of the EAF. Such a configuration resembles, in appearance, to a litter of piglets suckling on a sow. As the metal cools and hardens the branching ingots, the Pigs, simply break away from the much thinner runner, the Sow, hence the name Pig Iron. III. CASE STUDY A. Problem Statement Firstly, low fault level, thanks to its remote location near a forest land. Secondly, high power quality harmonic disturbances, from a hyperactive Howrah-Mumbai railway traction line that passes beside it and receives 25kv supply from the same nearby 132/33kv Ghatsila Substation as shown in Fig.3 (The top caption picture). Furthermore, the conventional engineering design practice is limited in installing only power factor compensation capacitors for linear loads, and capacitors with detuned reactors for non linear loads (NLL). The same design practice is also followed here considering that by the EAF as NLL.

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