Research on the heavy gas operation characteristics of the gas relay under multiple-point fault stimulations

• Design a dual-air cannon co-excitation experimental platform. • The BF gas relay has a stable and fast operation characteristic. • There is a delay in the heavy gas operation of the QJ gas relay. • The QJ gas relay multiple-point fault heavy gas operation is defective. Gas relays are critical non-electrical protection devices for oil-immersed transformers. However, their heavy gas operation mechanisms under multiple-point fault conditions remain underexplored, posing reliability risks to power grids. This study addresses this gap by introducing a novel dual air-cannon co-excitation experimental platform integrated with numerical simulations, systematically investigating the dynamic response discrepancies between BF-type and QJ-type gas relays under single-point and multiple-point fault scenarios. The research findings reveal: For all fault types, the BF-type gas relay exhibits a baffle operation duration of less than 15 ms. This performance advantage stems from the synergistic effect between the exponential decay of the magnetic moment and the jet flow effect at the baffle's leading edge, which collectively enables a significant reduction in alarm time compared to the QJ-type gas relay. For the QJ-type gas relay, baffle operation duration correlates negatively with fault intensity: increasing excitation pressure from 0.110 to 0.120 MPa shortens duration by 55.64 %. The fault interval significantly affects the baffle's operation duration. At 0.5 s, the baffle reverses mid-operation, delaying alarm activation to 200 ms (a 140.96 % increase over the 0.3 s interval). It has inherent operation delay issues: when the oil flow velocity during a transient fault reaches 1.048 m/s (exceeding the setpoint), there is a risk of alarm refusal. The dynamic simulation method for multiple-point faults proposed in this study overcomes the limitations of traditional single-point fault excitation, providing critical insights for optimizing gas relay selection and revising calibration standards.