Oil Pressure Variation Rules of Oil-Paper Insulating Bushings Under Typical Defects

Abstract

Oil pressure is the most direct characteristic quantity that reflects the operating status of steel-structured oil-less equipment and achieves explosion-proof equipment. However, the lack of oil pressure change patterns of typical defects has always been the key to limiting the development of oil pressure diagnosis technology for oil-less equipment. Based on this, this article systematically carried out experimental research on the oil pressure changes of oil-paper casings under typical electrical, thermal, and mechanical defects. First, an equivalent model of high-voltage oil-paper insulation casings with adjustable defect types was constructed using the equivalent reduction method. Then, by adjusting the defect type (partial discharge (PD), local overheating, and oil leakage) and defect severity, a large number of experiments were conducted to obtain the oil pressure change pattern of oil-paper casing under typical defects. The study found that under long-term discharge defects caused by capacitor core impurities and capacitive screen wrinkles, the oil pressure showed the iconic characteristic of rapidly rising initially, then remaining stable and rising rapidly again. The change pattern of oil pressure can reflect the degradation process of discharge defects. By using oil, the pressure can effectively realize the early warning of discharge breakdown accident; affected by the balance of heat energy dissipation, the time required for the oil pressure to rise to stabilize under local overheating defects has nothing to do with the severity of overheating, but the oil pressure rising slope and the final stable oil pressure value It is positively correlated with the severity of overheating; the final stable oil pressure value of different severities of oil leakage defects is the same, but the oil pressure drop rate under leakage oil defects is negatively correlated with the severity of oil leakage, and the oil pressure changes can be a good early warning The occurrence and severity of overheating defects and oil leakage defects. The research results of this article will further promote the development of oil pressure diagnosis technology for oil-less equipment.