A Novel Method of Transformer Overloading Detection by Magnetic Flux Leakage Measurements

Power distribution networks in developing economies are often subjected to overloading. Resultantly, typical distribution transformers performing the final high to low voltage (LV) conversion are operated beyond rated capacity during peak demand hours. This overloading exceeds permissible limits prescribed by IEEE C57.91 and results in transformer failure and even catastrophic fire/explosion. Main objective of this work is to develop a contactless overload detection mechanism for distribution transformers. It was anticipated that measurement and quantization of magnetic flux leakage (MFL) outside steel tank can be utilized for overload detection. To validate this, a commercial 200 kVA transformer was modeled and tested by finite element method (FEM) to obtain levels of MFL in different loading states at various sensing points outside steel tank of transformer. Then an experimental test bed was established to validate finite element analysis (FEA) results. Resultantly, a method of transformer overloading is demonstrated and an optimum sensing position was determined. Furthermore, correlation coefficient remained greater than 90% for experiment as well as for FEM indicating high linearity between MFL and loading states of the transformer.