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Electrical Engineering


New methodology and software improve control of power losses in the electrical sector

BEL FALLEIROSEvery year, between the hydroelectric power stations and the end consumer, no less than 18% – or 80 thousand Gigawatts-hour (GWh) – of the power produced in Brazil is lost in the entanglement of cables, transformers, connection branches and meters of the transmission grid. This adds up to losses worth R$20 billion for the sector’s companies. To uncover the sinkholes that are draining this power, professor Antonio Padilha Feltrin, from the Department of Electrical Engineering of the Ilha Solteira campus of Paulista State University (Unesp), in inner state São Paulo, developed with FAPESP aid a system that analyzes the loss of power. The idea was to measure this relatively fast, track the issue and propose a loss reduction action plan. The results, however, exceeded expectations. The study also gave rise to a methodology and to a software program to help distribution companies to calculate and understand better how and where the main losses occur. According to Padilha, this is a fairly old concern in the field of electrical engineering. “Now, however, with the segregation of the activities of the electrical sector into generation companies, transmission companies and distributions companies in Brazil, the problem gained prominence and we have started to investigate it,” he explains. “When we realized that the losses of the distributors, which carry power to the end consumer, are far greater than in the other segments and that they vary widely from one company to the next, we became aware of the need to develop new ways of calculating these losses.”

The work started in 2004, with a research and development (R&D) project approved by Aneel, the National Electric Energy Agency. After this, the professor’s team continued to pursue this research, looking for new methods. What they wanted was to create a methodology that joined the advantages of two types of calculations, the simple ones and the complex ones. According to Padilha, calculating the technical losses of a distribution system involves many variables, including the diversity of grids (medium and low tension), the number and the variety of devices that lead to power loss (meters, branches, transformers) and the volume of data required for the calculations. “They should be identified to provide input for action plans to minimize technical losses as well as non-technical ones, such as the theft of power via clandestine connections.”

According to him, the choice of a more elaborate calculation process or of a simpler one depends both on the data available and on the proposed objective. “The more complex methods, called bottom-up, yield results that are close to reality, and that can even be used for individual and localized analyses,” he explains. The problem is that for this, one needs a broad database and a permanently updated registry. The simplified methodologies, such as statistical processes and geometric models, known as top-down, demand a lower volume of data and allow one to estimate losses quickly. However, in this case, the results are satisfactory only when they are applied to large systems and overall.

Simple method
This is where Padilha’s work comes in, conducted with the PhD candidate Marcelo Escobar de Oliveira, who developed a simple method that produces more accurate results. It enables one to find out the technical losses in the distribution grids at least once a month quite easily. “The method’s innovation lies in using only the most used data and those that are easy to obtain in the distributors. It disregards or tries to avoid the need for other data that is not used daily in the engineering areas of the companies,” explains Padilha. “Based on this, we managed to get to a new calculation method.” This methodology is based on determining technical losses by means of a quantity of minimum data: the load curve at the substation, medium tension data such as cables and number of transformers, and average data on the low tension grid, such as type of cable and mileage. Nevertheless, it yields results that are as reliable as those of the complex processes. “The methodology might solve the deficiency of many companies that lack data about all their clients, and of some segments such as low tension circuits, connection branches and meters,” says Padilha.

Despite the advantages of the method developed, Padilha recalls that it is impossible to eliminate losses entirely, even though Brazil could reduce waste a fair amount. According to him, in developed countries, these losses stand at 12%, approximately. “Naturally, the Brazilian system has some special features, such as the site of hydroelectric power generation, which is far away from the consumption centers,” he says. “Throughout the world, the greatest losses are to be found in distribution and this is no different in Brazil. Therefore, the effort to cut losses should start with their reduction in this area and the first step is to become aware of their origin, whether technical or commercial, and of the segments or parts of the grid where they are greatest.”

Based on the new methodology developed, Padilha’s team created software to work out the calculation in an automatic, user friendly manner. This allows one to find out the technical losses by grid segment. Based on their total value, one can then calculate non-technical losses, those that occur due to metering errors, theft or escape, from the difference. Still as a result of this project, four articles were divulged at congresses, one was published in a journal, and a book chapter was produced. The software program developed by Padilha and his team must now be adapted for practical work. “It is excellent for scientific work, but for other applications the data inflow and outflow need adaptation. There are some distribution companies and one that develops and markets software that are interested in the program.”

The project
An analysis of tension and of electrical losses in power distribution systems (nº 07/07041-3); Type Regular Research Awards; Coordinator Antônio Padilha Feltrin – Unesp; Investment R$ 71,756.94 (FAPESP)

Scientific article
OLIVEIRA, M. E.; PADILHA FELTRIN, A. A top-down approach for distribution loss evaluation. IEEE Transactions on Power Delivery. v. 24, n. 4, p. 2.117-24. Oct. 2009.