Oil pressure is an important parameter to characterize the operating condition of power transformers, but two problems still need to be solved to when it is used for fault diagnosis: one is to establish the correlation between the oil pressure change of the transformer and gas production; the other is to clarify the influence of temperature on the oil pressure change. In order to solve these problems, this paper analyzes the influencing factors of oil pressure and provide suitable method for transformer bushing monitoring and diagnosis.



In this paper, a pressure-temperature field simulation model of transformer bushing is established, and the mechanism of oil pressure change and the effect of oil temperature on oil pressure change are analyzed. Then experiments are carried out to verify the relationship between oil pressure and oil temperature.



Simulation and experimental results show that the temperature in transformer bushing affects the oil pressure, so that the change of temperature and oil pressure shows consistency, while the change of oil pressure lags behind the change of oil temperature. And the lag is more obvious in low temperature than that in high temperature.



The results show that the main reasons for oil pressure change are gas production rate, expansion gas in oil and the temperature. In particular, the oil pressure is sensitive to ambient temperature change, but It is hysteretic. And it is found that the oil pressure change of the single-phase casing is more affected by the temperature. By temperature calibration technique or comparative analysis of three-phase casing, the influence of temperature on oil pressure can be reduced.