Rapid voltage changes - definition and minimum requirements

Abstract

Rapid voltage change (RVC) is one of the voltage disturbances classified under the term voltage quality and is included in several standards internationally but without a fully unique definition. This paper describes the Norwegian regulator's motive for introducing requirements for RVCs in the public electricity quality of supply regulation. Furthermore, a research project is described with focus on which rapid voltage changes that are visible in lighting. This project gave a sound basis for providing a unique definition on RVCs, and the definition is also presented. Finally, the paper describes the regulator minimum requirements for RVCs.

Rapid Voltage Changes in Power System Networks and Their Effect on Flicker

“…Networks and their Effect on Flicker IEC 61400-21 limits the number of voltage variations in a fictitious network for grid connected wind turbines, but without specifying a method for their measurement [ Table I shows the indicative planning levels for MV, HV and EHV systems, proposed in IEC 61000-3-7 for RVCs expressed as a percentage of the nominal voltage versus the number of such changes in a given time period [2]. Table II shows the limits applied in Norway at the PCC for RVCs as a function of their magnitude and frequency for different voltage levels [6] and Table III presents a summary of practical engineering limits for RVCs in different countries.…”

“…Brekke et al in [6] presents the results of a research project carried out by the Norwegian regulator on how different parameters of a RVC event, as the magnitude of instantaneous rapid voltage changes, the rate of change dv/dt of voltage during the event or the time duration between consecutive RVCs, affect the visibility of lighting equipment. The authors claim for the necessity to measure RVCs as a separate parameter, because measuring flicker will not ensure their correct assessment, and propose a precise definition and requirements for these events.…”

“…Bollen et al [5] propose the definition of indices for the measurement of voltage fluctuations in very-short time scale, which could be used for the characterization of RVCs. Brekke et al [6] associated RVCs with annoying flicker in order to establish minimum requirements for the phenomenon. The final report of the working group C4.108 of the International Council on Large Electric Systems (CIGRE) concluded that RVCs lacked clear definition and that there were no standardized methods for their measurement [7].…”

Customer's impact on the distribution grid

“…Rapid voltage changes of 10 % (e.g. from motor startups) result in 34% reduction of light intensity of a 60 W incandescent lamp [2].…”

Wavelet Packet Decomposition for IEC Compliant Assessment of Harmonics under Stationary and Fluctuating Conditions

“…The last two modulations were considered to provide a more reliable validation, since they could be realistically found in the grid, in the case of the connection of large loads or in the case of flicker [29]. More information about the modulation patterns is given in Section 4.3.…”