Diagnostic Measurement Practices for Instrument Transformers

Statistical study indicates that around 95% of Instrument Transformer failures are not maintenance related but are result of either causes introduced before putting into service or due to incorrect operation. To design a suitable maintenance plan for Instrument Transformers (IT), it is very important to understand their most prominent failure modes, identify the testing tools available and to find a perfect fit to suit the requirements within the limitation of site conditions. In this paper the different failure modes of IT are analyzed. Further the different diagnostic practices, along with their suitability and interpretation are discussed to aid the user to make an informed decision for condition-based maintenance.