Determining Localization and Measuring Level of Partial Discharge in Power Transformer Using Acoustic Sensor: Case Studies at Kemang & Cilegon Baru Substation

The dielectric subsystem is an essential part of every HV apparatus. Along with the operation time, some deterioration can happen to the dielectric section. Offline tests can measure how good the dielectric is, but some symptoms cannot be discovered. Partial discharge (PD) is a standard test that can measure the dielectric strength of all equipment. When PD energy is high enough, failure can happen. PD test can determine the location of the source and the best follow-up for repairing this issue—the concept for localizing the PD source inside a transformer using the screening area method. Testing equipment consists of four acoustic sensors installed on every side of the transformer. Acoustic signals from the creep source will travel in dielectric oil and creep to the metal surface of the transformer tank, where they can be detected and measured with acoustic sensors. When one or more sensors detect a more significant PD signal, all sensors move to that side and measure a wide area. This step will repeat, moving the sensor from a comprehensive place to a smaller area depending on where it detects a partial discharge signal until it reaches a specific area where all sensors detect a PD source. This paper gives steps for localizing the PD source and findings. At the Kemang substation, dissolved gas analysis (DGA) and sweep frequency response analysis (SFRA) correlate with PD measurements. Research from the Duval triangle and PD measurement has the same result: low discharge level at phase T (high voltage side), supported by the SFRA test with a small deterioration result. In another case at Cilegon Baru Substation, a major-level PD source was found at the tertiary voltage side of all three banks of transformers and matched with a high level of paper degradation findings.