1 Abstract— This paper investigates the impact on the harmonic levels of changes in television viewing patterns in Australia. Harmonic levels during special sporting events which attracted large television viewing audiences were recorded at several sites and compared to levels at other times. The enormous increase in television audience levels (compared to typical levels at that time of the night) during the 2006 World Cup soccer match resulted in a modest increase in harmonic voltage levels. The surprisingly low impact may be attributable to the number of television receivers which are continually in operation or standby mode. No conclusive trends were observed in harmonic voltages during the 2004, 2005 and 2006 Melbourne cup races. There was a reduction in harmonic voltages at one site during 2004 and 2005 races. However this trend was not repeated in 2006. The influence of network capacitors on harmonic levels was considered. Lessons learned from these observations could potentially improve our understanding of the impact of customer equipment and customer behaviour on harmonic levels and assist in managing waveform distortion now and in the future. Index Terms—power quality, harmonic distortion, tv receivers. I. INTRODUCTION He presence of harmonics in electricity networks can lead to increased losses, heating of components and loss of equipment life. In some cases they can cause multiple-zero crossings of the waveform, fuse blowing, communication system interference, acoustic noise (eg in ceiling fans) and energy meter inaccuracy. They also have an impact on power factor. Television receivers have power supplies which create current harmonics. Whilst the harmonic current levels are small in magnitude, the cumulative effect of large numbers of receivers can be significant. One way to examine the effect of television receivers on network harmonic levels is to monitor harmonic levels during periods of increased television viewing. This paper records the results of monitoring harmonic levels during two sporting events which had very high television ratings. Harmonic levels at several sites during the 2006 World Cup Soccer matches and during the This work is supported by Integral Energy. N. Browne (neil.browne@integral.com.au) is with System Development Branch, Integral Energy, Huntingwood, NSW 2148, Australia. S. Perera (sarath@uow.edu.au) is with the School of Electrical, Computer and Telecommunication Engineering, University of Wollongong, NSW, 2522, Australia. P. F. Ribeiro (pribeiro@calvin.edu) is with the Department of Engineering, Calvin College, Grand Rapids, II 49546 USA. Melbourne Cup horse race were examined. The Melbourne Cup is an annual event so harmonic levels at one site for the last 3 years were compared. II. TELEVISION RECEIVERS A. Power Supply Description In contrast to the linear power supplies used in older electrical equipment, more recently switch mode power supplies have become the standard interface between the power system and many electrical appliances including TV receivers. These switch mode power supplies use a capacitor after the bridge rectifier to smooth the 100 Hz ripple on the dc link. The coincidence (or near coincidence) current pulses drawn by these devices has led to significant peak flattening of supply voltage waveforms [1]. There are a number of design solutions for switch-mode power supplies which address this problem. One solution is a pre-converter switch- mode supply. A pre-converter can operate from the unsmoothed rectified mains supply and produces a dc voltage with only a very small 100 Hz ripple. By proper modulation of the pre-converter, the input current can be made sinusoidal and in phase with the voltage and hence the harmonic distortion is reduced to very low levels and the power factor is close to unity [2]. It is probable that the network load includes television receivers containing a variety of power supply design types. Other harmonic loads also may have changed over the years as product standards have developed to control harmonic levels. B. Viewing Patterns The World Cup soccer match between Australia and Japan occurred at 2300 AEST (Australian Eastern Standard Time) on Monday 12 June 2006. The match between Australia and Brazil took place at 0200 on Monday 19 June 2006. In Australia, the television audience peaked at 1.74 million at 0346 hours. Soccer matches last 45 minute for each half, with a break of approximately ten minutes. The Melbourne Cup race is held on the first Tuesday in November each year at 1500 hrs. It lasts approximately 3 minutes, however viewing time is typically 15 to 30 minutes. C. Method of Measurement of Harmonics Power quality monitors were connected to measure the phase to phase voltages on the 11kV busbars at 7 zone substations. They also measured each phase of the summated currents of the zone substation transformers. Voltage at two Harmonic Levels and Television Events N. Browne, Member, IEEE, S. Perera, Member, IEEE, P.F Ribeiro, Fellow, IEEE. T 1-4244-1298-6/07/$25.00 ©2007 IEEE.