Overheating and discharge fault identification for novel three-element mixed oil–paper insulation system based on new characteristic gas combination parameters

Abstract

To support the safe operation of the novel three-element mixed insulation oil (TEMO) transformer, gas generation behaviors of the TEMO oil–paper insulation system under overheating faults and discharge faults were investigated. Results show that that the content of H2 and C2H6 generated by TEMO–paper insulation system is much higher than that in conventional mineral oil (MO)–paper insulation system under different overheating temperatures. Under partial discharge fault, the content of H2 dissolved in oil changes distinctly, while the content of C2H2 also increases with the discharge time. Under surface flashover breakdown, AC breakdown and lightning impulse breakdown fault, the content of H2 and C2H2 changes greatly compared to other gases, while the concentration of total hydrocarbon gases in TEMO–paper insulation system is smaller than that in MO–paper insulating system after the same breakdown times. The diagnosis model of overheating and discharge faults for the TEMO–paper insulation system was proposed based on the oil dissolved gas analysis, while H2, C2H2 and C2H4 were chosen as the characteristic gases and the boundary settings were determined. The verified result for the low-temperature overheating, lightning impulse and surface flashover fault for the TEMO–paper insulation system presents that the new diagnosis model is effective.