Abstract: This paper investigates a specific fault event involving the tripping of a main transformer in a smart substation and identifies the primary cause to be a misoperation of the sampled value（SV） soft switch.So using a flow-based logic judgment as a remote lockout strategy is proposed for SV soft switches.This strategy effectively terminates erroneous operations when operators inadvertently engage with the SV soft switch during operational periods.The results indicate that this measure can eliminate soft switch misoperations, thereby ensuring equipment safe and reliable operation in smart substations.