Power Quality Analysis mitigates SCADA and HMI ...


Power Quality Analysis Power Quality Analysis in a tyre conglomerate revealed the root cause of repetitive electronic card failures in SCADA, HMI, Hard Disk and AC/DC Drives and frequent unwanted tripping in its process due to voltage fluctuation. The supervisory control and data acquisition system, which is a combination of software and PLC/Computer hardware, malfunctions in sending correct batch data from HMI to process computer missing out a few process data, each day. The LED fitting driver fails due to triplen harmonics which in-addition cause a neutral current in the lighting transformer feeder. The Curing section is most sensitive in the tyre manufacturing process which used to trip frequently on voltage fluctuation. During monsoon, there used to be persistent tripping with chronic grid voltage surges. The plant management planned to upgrade the 33kV grid incomer to 132kV for solving the tripping problem. It was very costly, and that could not have solved the tripping problem anyway. The introduction of steel radial tyres brought in considerable non-linear loads (NLL) in the forms of variable speed drive (VSD), DC drives and sizeable SCADA and HMI controls in the tire manufacturing process. Premier tyre companies complying with safety regulations upgraded their process for high quality and long life radials, which further increased PLC and HMI control. It resulted in an increased total current harmonic distortion (THDi) which at the base level, without switching on capacitors, was between 20 to 40% at the main incomer of various process transformers with a corresponding total voltage harmonic distortion (THDv) of between 5 to 10%. Factory engineers need to maintain Power Factor (PF) for avoiding high demand (kVAh) charges and low PF penalty from the utility company. But they faced a new problem in adding capacitors either at load end across various high capacity motors or at PCC loads or centralized APFC panel across transformer LT busbar. It magnified harmonics in an unpredictable and non-linear manner. The magnification could be as high as several times the base harmonic level or just a few percentage point higher, which depends upon the fault level of the power system. In a high fault level power system, THDi magnifies disproportionately higher than THDv. The reverse happens with a low fault level power system. Then arrived the Detuned Harmonic Filter with a 6% reactor in series with the capacitor. Though it solved the harmonic magnification problem and improved the PF, it could not solve the repetitive equipment failure and nuisance tripping problem, and the detuned filter itself failed frequently needing continuous component replacement. Besides, it can not reduce harmonics. When the real solution arrives, the detuned filter needs to be replaced, paving the space for the super tuned harmonic filter that solves all the failure and tripping issues besides slashing down harmonics, both THDi and THDv, within IEEE 519 limits. How did the high harmonics bring in Power Quality Problem and unwanted equipment tripping in the tire industry? Well, that issue explained in details in another webpage "Power Quality Solution Delivered". What did it take to resolve both the trouble, equipment failure and nuisance tripping? The approach to the solution, its methodology and efficacy described exhaustively on another webpage "Passive Harmonic Filter proven valuable When Equipment Fails".

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