Flicker Limit Compliance Assessment in the Presence of Background Disturbances

Assessing voltage fluctuations in the power system is necessary to prevent negative impacts to customers and the connected equipment. A flickermeter can be used to measure a flicker severity level that is based on the total voltage fluctuation present at a measurement point. The flickermeter can only assess the total flicker level at the measurement point; it cannot identify any individual network user's contribution. For the purposes of limit compliance assessment, it is essential to have the ability to determine each user's contribution. A measurement algorithm for accomplishing this task is presented in this paper. The algorithm is based on using measured voltages and user currents to determine the user complex power, and from the complex power and an online estimate of the network impedance, estimate the voltage fluctuation that the user would produce, if acting alone, at the measurement point. These estimated voltage fluctuations are used as inputs to the flickermeter so that the resultant flicker severity value reflects only the contribution of the individual user. Fourteen weeks of field test results are correlated with user demand data to demonstrate the effectiveness of the approach, and the traditional concepts of weekly percentiles, flicker summation, and background flicker are employed to validate the results.