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RULE OF THUMB FOR CALCULATING DISTRIBUTION FEEDER LOSS

How can we estimate the distribution feeder loss using a single formula?

The distribution system of an electric utility is a very complex system that is composed of many different kinds of electrical equipment. To mention a few of these components, this would include the feeder lines or wires which in reality are of different size and lengths, distribution transformers of different kVa rating capacity, low voltage lines, etc. 
Traditionally, in computing for the total distribution feeder loss, one would manually compute for the individual line loss of every section in the distribution system considering the actual length and actual loading of that section. In the advent for computer technology, this computation became more readily available through computer simulation using numerical methods and analysis.
However, if one electrical engineer wishes to compute for the feeder loss of a certain distribution system, he would either manually compute for it or purchase a very expensive application that is capable of simulating this value. The former would be highly time impractical and the latter to be financially impractical especially for an electric utility which are low income generating.
IEEE, 1994-1997 published a simplified method in computing or estimating the total loss of a certain distribution system. This simple formula is called Chen Simplified Feeder Loss. This formula was derived from using regression analysis of study involving load flow simulations. The formula is composed of four variables; total primary conductor length (km), secondary conductor length (km), total transformer capacity (MVA), feeder loading (MW), and power factor of feeder loading.
Refer to the formula below to understand how we can derive with an estimate for the distribution feeder loss using only this basic distribution systems information.

feeder loss formula

Comparison example between the Chen formula and the result of Synergee feeder loss simulation:

Ploss: 32.6433+0.752PLH+2.0041SLH -0.0908TR^2+3.0206(LD/PF)^2
A certain feeder having the parameters specified below needs to evaluated on the estimate of its feeder loss.
PLH: 10.3 (km)
SLH: 106.4 (km)
TR: 8.2135 (MVA)
LD: 4.214 (MW)
PF: 99%
Substituting the above parameter to the Chen formula would result to 247.5051 kw of feeder loss or approximately 5.87%. The same feeder if simulated using Synergee software has a total percent feeder loss of 5.99% 
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Comments

  1. UnknownNovember 27, 2013 at 10:29 AM

    The correct answer to the sample problem based on the given values should be 302.2279kW instead of 247.5051kW. Please verify. thanks

    ReplyDelete

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