Factor Affecting Short Term Load Forecasting

Abstract

Abstract-The basic objective of short term load forecasting is to predict the near future load for example next hour load prediction or next day load prediction etc. The total system load is the load seen at the generating end of the power system, which includes the sum of all types of loads connected to the system plus the losses. To design efficient and accurate forecasting model one must have good understanding of the characteristics of the system. There are various factors which influence the behavior of the consumer load and also impact the total losses in transmission lines. These factors can be categorized as Time factor, weather, economy and random disturbances. In this research paper these factors and their impact on consumption of electric power and their significance in short term load forecasting is evaluated.Index Terms-ANN, factors of STLF, load forecasting, load prediction. I. TIME FACTORTime is the most important factor in short term load forecasting because its impact on consumer load is highest. From observing load curve of several different grid stations it is found that the load curve has "time of the day" property, also it has "day of week", "week of month" and "month of season" property. This means that load curve is periodic in nature. Fig. 1(a)- Fig. 1(c) shows the load curve of 3 Fridays of the April 2012.As can be seen in Fig. 1(a)- Fig. 1(c) that although the average load is different because of the difference of temperature during each day but the pattern of the load is nearly same. In each curve there arises three peaks First peak at 8 o clock, 2 nd peak at 12:30 pm, And third at 8 pm and in curves first peak is lowest 2 nd a bit taller and third the highest. This shows periodicity in terms of day of the week. Manuscript received August 17, 2013; revised December 16, 2013. This work was carried out as a final year project for the award of MS degree in electrical engineering.Muhammad Usman Fahad is with the University of Engineering and Technology, Peshawar,.Naeem Arbab is with the Electrical Engineering Department of University of Engineering and Technology, Peshawar, Pakistan (e-mail: mnarbab01@yahoo.com). From the observation of daily load curve of any grid station it can be seen that load variation follows certain rules with the "time point" of the day.In Fig. 2 hourly load curves is shown for 24 hours of a day in winter season. The interval length is one hour, so there are 24 intervals in the figure. It can be seen in figure that the load is low and stable from 0 am to 6 am (0am means 12 o clock at night), the load start rising at 7 o clock till 9 am and then it is flattened till 12 am and after that it descends till 5 pm (17:00 in figure) and after 5 pm it start rising till 8 pm (19:00), after 8 pm load gradually decrease again until the end of the day.It can be seen in Fig. 2 that maximum demand occurs at 8pm, and minimum load demand occurs after mid night. So if we closely observe this load curve it can be seen that load demand reflects the consumer's daily life style. At mid...

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