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A SIMPLIFIED APPROACH IN ESTIMATING TECHNICAL LOSSES IN TNB DISTRIBUTION NETWORK BASED ON LOAD PROFILE AND FEEDER CHARACTERISTICS: TECHNICAL PAPER


Authored by: MARINA YUSOFF*, ASNAWI BUSRAH*, MALIK MOHAMAD*, MAU TENG
AU**

Abstract: - This paper presents an approach to estimate technical losses in utility’s distribution network based on feeder’s load profile and characteristics, such as such as length, peak demand to installed capacity ratio, and load distribution profile. The developed methodology is implemented in spread sheets format, which is simple and user friendly. It requires minimum set of input data, while giving reasonably accurate results. The approach is tested on a real TNB distribution network and the results are reasonably accurate. Additionally, the spread sheet developed based on the methodology could also be used to perform various energy auditing exercises.

Introduction - The amount of energy loss in electrical distribution system is one of the key measures of distribution system performance as it has a direct impact on the utility’s bottom line. Distribution system’s losses can be attributed to technical and non-technical. Non7technical losses are those associated with inadequate or missing revenue metering, with problems with billing or collection systems, etc. Technical losses in the system are inherently influenced by component and system designs.
Since losses represent a considerable amount of operating cost, accurate estimation of electrical losses enables TNB to determine with greater accuracy the operating costs for maintaining supply to consumers. This in turn enables a more accurate estimate of system lifetime costs, over the expected life of the installation. It is also critical to know if the expected target of technical losses is indeed technical, whether it is possible for reduction without changing the components and system design. Lower technical losses will provide for cheaper electricity and lower production costs, with a positive influence on economic growth. 

Various studies have been conducted over the years to calculate energy losses in distribution network [1-4]. Typically, in technical loss estimation studies, the technical loss level is estimated using simulations of the network. However these studies would require complete set of data to estimate the technical loss level. A study by Carlos A. Dortolina and Ramon Nadira, [5] propose a methodology  called ‘top-down/bottom up’, where energy losses are computed in relative accuracy for specific distribution systems or feeders and then uses the results to benchmark (i.e. estimate technical losses using top down approach) other parts of the network with matching features. The main advantage of this approach is that it can handle varying degrees of data availability.

Conclusion -This project presents a methodology to estimate technical losses of distribution network based on analytical method. Peak power loss functions of medium voltage distribution feeders based on different feeder characteristics are first established through simulation. Technical losses of each individual MV feeder is then estimated based on the respective peak power loss function and estimated feeder peak demand, length and load factor. To establish the technical losses of the complete MV network, normalized average of percent technical losses of each feeder is taken. Technical losses of distribution transformers are estimated based on transformer no load and load loss, average capacity factor, and loss factor. Finally, the technical losses of low voltage are estimated from the peak power loss function of LV network (classified as overhead or underground system), average percent loading, and loss factor. The estimation methodology is implemented using spread sheets. From the case studies, it is shown that results obtained based on the proposed approach are reasonably accurate.

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