Response Characteristics of the Buchholz Relay and Novel Non-Electric-Parameter Protection Methods

In recent years, many accidents occurred worldwide owing to Buchholz relay maloperation and failure to act in time, which significantly compromised the security of power systems. To address this problem, an experiment based on a 25 MVA/110 kV oil-immersed power transformer setup was performed to characterize the response of a Buchholz relay; gas-generation faults of different severity inside the transformer's oil tank were simulated by controlling the pressure and volume of injected gas. The experimental results reveal that the gas accumulation relay has high sensitivity but insufficient speediness. Further, the oil surge relay is relatively fast but low in sensitivity, whose action threshold is affected by static pressure difference. Based on the different characteristics of non-electric parameters under internal and external faults, a digital non-electric parameter protection method, which exhibits good performance, is devised. The findings of this study can lay the foundation for optimizing the design and evaluation of the Buchholz relay, and for developing non-electric parameter protection devices.