Monitoring the condition of power transformers is a crucial issue, and in this article, Ampacimon discusses its solutions for managing and solving this challenge.

First, the selection and test configuration of partial discharge (PD) sensors used when the power transformer is connected to the grid via an oil-air plug or cable terminal is an important issue; therefore, different sensor alternatives were considered by Ampacimon: a coupling capacitor with a measurement impedance, high-frequency current transformers attached to the grounding cable sheath, high-frequency current transformers connected to the transformer tank ground connection, and UHF sensors placed on the cable sheaths or near the transformer tap when used.

Signal processing analysis is used to identify whether the PD source is in the power transformer, feedthrough, cable termination, or cable system. Next, signal processing tools are used for noise suppression, PD clustering, PD localisation, and PD phase resolved pattern recognition to obtain an appropriate diagnosis. Measurements of load current, voltage, and ambient temperature are complementary parameters used to correlate the behaviour of PD activity. A histogram of the hourly distribution of PD activity and a monitoring period of several weeks allows a better understanding of the correlation between the insulation fault and these parameters to obtain a better insulation diagnosis.

Image source: Courtesy of Ampacimon

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