Theoretical Study On Flow Field Of Gas Relay Based On CFD

The gas relay was invented by Max Buchholz in 1921.Since its inception,it has become an important protective and monitoring device for liquid-cooled transformers and ground reactors.It has the advantages of simple structure,fast action,high sensitivity,andstable operation,high reliability and simple installation.It has been used as the main protection device inside the transformer.However,due to gas relay malfunction caused by frequent electrical accidents in recent years,to which the safe operation of power systems and power supply reliability caused a huge impact.Therefore,the research on the flow field of the gas relay is of great significance to the safe and stable operation of the power system.At present,the imported BF-type double-float gas relay and the domestic QJ-80 type gas relay are widely used in electric power enterprises.In this paper,the two types of gas relays as a research model.The flow field theory of gas relay was carried out on the basis of a large number of related literatures and the dynamic analysis of scientific research.First of all,three-dimensional solid modeling of two types of gas relays is made by using 3D CAD modeling software Pro/ENGINEER.In order to the simulate results more accurately,the internal structure of the gas relay is described in detail,so that the parameters of the calculation model are as close as possible to the measured parameters.The ICEM software is used to complete the grid division of the computational fluid domain,and the integration of CAD and CFD technology is achieved.The computational fluid domain of the gas relay uses a hybrid meshing technique combining the advantages of structured and unstructured grids.Then,the dynamic CFD numerical simulation of the whole process of the two types of gas relays is carried out based on the dynamic grid theory,and the calculation results are analyzed and studied.The results show that the difference between the two types of gas relays is mainly reflected in the sensitivity of the impact torque of the water flow.The reaction of the domestic QJ-80 gas relay is relatively conservative and the reaction of the imported BF type gas relay is more sensitive.At the same time for possible causes of heavy gas malfunction reasons analyzed in-depth.①reverse oil flow impact;② anti-vibration performance is insufficient;The results show that the two possible causes of malfunctions ③ reverse oil flow impact caused by the possibility of heavy gas malfunction is very small;④ the corresponding improvement scheme is proposed for the lack of anti-vibration performance,and the effectiveness of the improved scheme is tested.Finally,CFD computer simulation technology is proposed to calibrate the oil flow set value of gas relay.The simulation results show that the proposed method can verify the flow value of the gas relay in a simple and effective manner,and can clearly reflect the flow velocity distribution at the specified time within the gas relay.Effectively improve the efficiency and reliability of gas relay set value calibration.