Impact of Online Testing of Distribution Transformers- A Case Study

The distribution transformers being an integral equipment in the power system, rigorous testing procedures are essential for their safe operation. The type tests are performed to assess the short circuit capabilities of transformer windings. These tests are carried out in indoor transformer testing laboratories. The required short circuit power and current in the test facility are made available from the national grid. This being an online test facility, the testing will have significant impact on the grid operation especially in the case of weak grids. Central Power Research Institute (CPRI) is establishing an online test facility at UHVRL, Hyderabad to test the distribution transformers. This is a unique online test facility for testing of distribution transformers of the class 11 kV and 33 kV. A comprehensive offline study is conducted to assess the impact of online testing of the distribution transformers on the Indian National grid, the results of which are discussed in this paper.