Detection of Near Failure Winding due to Deformation in 33/11kV Power Transformer by using Low Voltage Impulse (LVI) Test Method and Validated through Untanking

Power transformer consists of components which are under consistent thermal and electrical stresses. The major component which degrades under these stresses is the paper insulation of the power transformer. At site, lightning impulses and cable faults may cause the winding deformation. In addition, the winding may deform due to impact during transportation. A deformed winding will excite more stress to its insulating paper thus will degrade it. Insulation degradation will shorten the life-span of the transformer. Currently there are two methods of detecting the winding deformation which are Sweep Frequency Response Analysis (SFRA) and Low Voltage Impulse Test (LVI). The latter injects current pulses to the winding and capture the admittance plot. In this paper, a transformer which experienced overheating and arcing was identified, and both SFRA and LVI were performed. Next, the transformer was brought to the factory for untanking. The untanking results revealed that the LVI is more accurate than the SFRA method for this case study.

Authors:

• R. Samsudin
• Yogendra
• Hairil Satar
• Y.Zaidey

Keywords:

• Winding Deformation
• Arcing
• Dissolved GasAnalysis
• Sweep Frequency Response Analysis
• Low VoltageImpulse Method

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