Experimental research on air-gap partial discharge properties in transformer oil-paper insulation

Partial discharge in oil-paper insulation is one of the main reasons for aging and disruption of the power transformer. Understanding the emergence of partial discharge and the gas variation law in time can determine the development of internal latent fault. Therefore, based on the air-gap discharge model, which is the primary discharge type, partial discharge characteristics and gas generation law were researched. The experimental results show that: Sk with Ku of H_η(φ) and Sk of H_qmax(φ) ascend as time rises; air-gap partial discharge mainly produces H₂, CH₄ as well as CO and the absolute gas generation rate of main gases show a downward trend; combined with fuzzy diagnosis, the relationship between partial discharge and dissolved gas in oil was analyzed, revealing that the code of the approved three-ratio method correlated to air-gap partial discharge most is “110”.