A survey of harmonic voltages and currents at distribution substations

Abstract

This paper reports seven day measurements of harmonic current and voltage made at the sending end of jive feeders. The major goals are to present different ways of recording and displaying harmonics, to explain the results and to compare them with the existing engineering recommendations. At the same time, these results will provide the initial core of documentation for future reference and followup of the harmonic growth trend in 15 and 25kV feeders.The need for information on levels of harmonic pollution in power networks was stimulated by the increased importance of large rectifier stations [l], used for HVDC transmission lines and links. Major surveys were initiated at the beginning of the last decade [2,3]. Progress in the fabrication of microprocessors and minicomputers led to the design of powerful instrumentation capable of real time data acquisition [4,5,6,7,8,9]. Each new generation of instruments was capable of more advanced data acquisition, processing, and display than the previous generation.A detailed description of the instrumentation used for this survey is found in references [4,5,10]. Voltage and current waveforms were repeatedly measured and processed in three minute time intervals. The harmonic spectra and the phase angles of the current or voltage harmonics were computed by means of an FFT algorithm. Histograms of harmonic amplitudes were developed based on each waveform measured, along with the minimum, maximum and mean values of the rms value of each harmonic in each three minute interval. The software system was then used to organize the data into histogram or cumulative distribution graphs, and to produce plots of the statistical values versus time.This comprehensive survey monitored voltage and current distortion at eleven locations:Five distribution feeders One large apartment building Three industrial customers Two commercial customers 91 SM 4 1 6 -8 PWRD A paper recommended and approved by the IEEE Transmission and Distribution Committee of the IEEE Power Engineering Society for presentation at the IEEE/PES 1. P l o t s of Active, Reactive a n d Apparent Powers Versus T i m e Part I reports measurements taken at the sending-end, namely Daily or weekly load cycle recordings make it possible to establish the relevance of an electric energy user in the power system. Harmonic power-flow, direction, power factor fluctuations, effect of switched capacitor banks and other energy related problems can be addressed by understanding such recordings. A seven day recording of active and reactive powers in a 13.8kV feeder is shown in Fig. 1. The reactive power plot indicates the moments when the capacitor bank is switched. During the weekend the demand for power is lower and the capacitors remained de-ener gized . Recordings of VoltageSeven day recordings of fundamental and higher harmonic voltage are presented in Fig. 2. Due to limited space only the 3rd, 5th and 7th harmonic are presented. The fundamental voltage monitoring helps determine the effectiveness of the voltage regulation system in th...

Filtragem adaptativa para a estimação da freqüência em sistemas elétricos de potência

“…Deve ainda ser lembrado que com o avanço tecnológico das últimas décadas e o aumento considerável da utilização de sistemas eletrônicos em equipamentos e máquinas, intensificou-se a preocupação com as variações de freqüên-cia no sistema, uma vez que estes modernos componentes são mais sensíveis a este tipo de perturbação (Emanuel et al, 1991). Deste modo, observa-se que o aprimoramento das técnicas utilizadas para uma melhor estimação da flutuação da freqüência em um SEP é muito importante para a operação correta do mesmo.…”

Distribution System Harmonic Filter Planning

“…Emanuel, Orr, Cyganski and Gulachenski [7] reported on measurements on 5 distribution feeders. They show that the significant harmonic voltage levels are occurring on these systems at the third, fifth, and seventh harmonics.…”

“…This method must account for the unknown magnitude and location of the harmonic sources as well as the changes in the system operating configuration which will be encountered. There is an immediate need for this methodology as a number of recent studies have reported harmonic voltages at or near levels where filtering is desirable [6][7][8][9][10].…”

Assessment of the harmonic distortion in residential distribution networks: literature review

“…In other line of research, the data collected by Emanuel et al (1991 in extensive surveys, was used by Cavallini et al (1995) to propose a deterministic-stochastic approach to calcu-late the Probability Density Function (PDF) resulting from the sum of harmonic currents in distribution network buses. The novelty of this work lies in considering the variation patterns of harmonics over time from a deterministic component, coupled to a component which takes into account the randomness of distortion.…”