Abstract:
Many energy audits in Sri Lanka have identified the installed presence of oversized
transformers and excessive number of transformers. No proper study has been done on
the effect of the no load losses added to the system due to oversized transformers.
Thus, transformers have not always being properly sized at the design stage.
In this research, a sample of bulk consumers from the North Western Province was
selected and their installed capacities were compared with the properly sized
transformers. Analysis shows that the no load losses can be reduced, on the average by
about 40% with the proper sizing. Having identified the importance of proper sizing of
transformers, software has been developed to select the optimum transformer capacity
comparing the total owning costs of the transformers. The effect of the load pattern,
transformer life time, discounting factor and the tariff rate has been considered in the
optimization. Also, the software permits the determination of the optimum transformer
for a few different load curves as well. The software tool has been validated in
comparison with manual calculations.
This software is a useful tool for the bulk consumer as well as electrical consultants to
determine the optimum transformer capacity for a given load curve based on total
owning cost. The consumer can select the optimum size at the initial stage of the
project so that unnecessary future costs due to losses can be minimized. Moreover,
this would not only be a blessing to the consumer, but would mean that the overall
distribution loss in the total electrical network will be reduced.
