Adopting the IEC Voltage Flicker Methodology in the United States

摘要

Voltage flicker was measured at two locations on a utility transmission system that serves two steel manufacturing facilities and a local town. The steel facilities included multiple furnaces and multiple SVC systems to improve the bus voltage level, reduce harmonics, and improve power factor. The voltage flicker measurements were performed using flicker meters employing the IEC measurement methodology. Data captured over seven days of monitoring was used to compare flicker propagation through the transmission system to he levels expected through calculation. In general, voltage flicker data indicate that propagation from the 161 kV melt shop system to the 500 kV utility system and back to the 161 kV system serving the rolling mill and local town was lower than expected. This could be due to many factors, including load damping, additional sources of generation on the network and unknown network contingencies. The propagation ratio was examined using the highest weighted flicker and P_(ST) values, as well as average daily values for both lowest overall although the result still indicated more attenuation than expected. Using the IEC 99th percentile values, short-and long-term flicker levels at both measurement locations were calculated. The measured/calculated flicker levels on the melt shop 161 kV system can be scaled to project the level of flicker at the 500 kV level, again using the ratio of short circuit MVA values. At the 500 kV level, this technique would indicate a flicker level that was 1.1 for the P_(ST99 percent) and 0.86 for the P_(LT99 percent). The observed levels at he other 161 kV location were approximately 60 and 65 percent of these values, respectively. This indicates a higher than expected attenuation of the voltage flicker through the transmission network. The IEC method is a useful technique, as it defines a methodology and a weighting curve and establishes some commonly accepted limiting values for utility observation of voltage flicker. The technique is being adopted by the IEEE Task Force on Voltage Flicker and is being used in some new utility/steel mill power contracts.