Source identification for voltage sag and flicker

Abstract

Summary form only given, as follows. Traditional sag and flicker measurements use voltage only. This is perfectly adequate to assess the utility system performance for survey or benchmarking purposes but has shortcomings when assessing sags and flicker causes by an individual customer. The new measurement technique described in this paper shows that by measuring current as well as voltage, and deriving the utility's source impedance, the voltage sag and flicker measured at a customer's point of supply can be separated into its two components-events caused by the customer being monitored and events already on the utility system. This separation is crucial in determining the voltage events that they are truly responsible for and not penalize them for sag and flicker coming from the utility or neighboring customers. This paper describes this new measurement technique and the subsequent Labview-based measurement system used to implement it. It also presents field studies that show how this measurement system was used to assess, in real time, the voltage flicker produced by two wood chip plants. In one case it provided a direct measure of the effectiveness of a DSTATCOM flicker countermeasure. In another case it provided conclusive evidence that a wood chip plant that wanted to expand was not the dominant source of voltage flicker in the area. These measurements gave the utility the confidence it need to allow the expansion knowing that the flicker increase would be small and acceptable.