ABSTRACT

Power Quality issues can be broadly classified as voltage quality and current quality issues. Current quality issues are mainly caused by consumers themselves, voltage quality issues could be either from the grid or consumer. One of the major voltage quality issue is voltage dip or voltage sag. As voltage dip is a momentary phenomenon, it is hard to monitor them unless there are sophisticated equipments installed for continous monitoring. A consumer can have a control over its load switching that could cause voltage dips, however he will not have any control over voltage dips coming from grid.

By design a transformer is the most efficient and long lasting electrical machine. Efficency of power transformer could be as high as 99.75% where as for distribution transformer, design efficiency could be in the range of 98.5% to 99.5%. A transformer is designed to have a life of 20 to 25 years. However, undesirable operating conditions reduces operating life of transformer to 5-6 years and efficiency could drop to 95% or even less

A transformer will work satisfactorily when it is feeding to the loads for which it is designed for and balanced loads. However in actual practice, transformers with a K factor of 1 is feeding increasingly non linear and un balanced loads. These factors cause increased operating temperature of transformer, reduced efficiency and reduced life of transformer. In cases of extreme third harmonic pollution the neutral points are often the victim resulting in burn out and failure.

This case study depicts how a distribution company addressed above issues thus improving life, reliability and efficiency of the transformer.

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