Measurements on partial discharge in on-site operating power transformer: a case study

This study presents the case study of a substation in-service power transformer referred to the on-site partial discharge (PD) detection and evaluation methods. An original methodology for simultaneous application of three methods is proposed: electrical, acoustic and ultra-high frequency. Transformer is powered by the power grid and no external generator is required according to the proposed methodology. Furthermore, several possibilities of applying these concurrent measurements and benefits of such solution in terms of result interpretation, interference resistance and on-site measurement applicability are indicated. The proposed methodology allows for a fast, accurate and secure PD diagnostics in a power transformer under on-site operating conditions. In the described example, a failure as a surface PD in the vicinity of the first phase of high voltage winding output is detected. The research results provide the basis for further works on a diagnostic expert system, which exploits automatic detection and evaluation of the PD phenomenon in power transformers under normal operating conditions.