On-Line Diagnosis of Power Transformer Insulation System: Experience of CPRI, India

Power transformers play a vital role in handling large amount of power from generating stations [through Generating Station Units(GSU] to transmitting stations (through power transformers) and to end user through distribution transformers. Power transformers involve large amount of capital investment and the failure of transformers causes severe fi nancial loss to the utility and inconvenience to the end users. Periodic maintenance and condition monitoring are the key factors for successful operation of power transformers. A number of diagnostic tools are in vogue. Most of these tests are conventionaloff-line techniques and require power shut down and disconnection of transformer from the circuit. Several alternate nonconventional on-line techniques are being adopted and Acoustic Emission (AE) technique is one among them. Central Power Research Institute (CPRI), India, is employing AE technique for on-line diagnosis of power transformers. Nearly 200 transformers have been tested and investigated covering rating up to 315 MVA, 400 kV.

The paper discusses some of the important aspects of on-line diagnosis of oil-fi lled power transformers employing AE technique. A few important case studies which have helped utilities and transformer manufacturers for initiating corrective actions are covered in the paper.