Recent policy developments in National Grid busbar protection application

During 2022, National Grid undertook a thorough review of its application policy for the busbar protection applied to its busbar type substations, chiefly at 275kV and above but also covering 132kV and below. This review, carried out at the request of th e Group Chief Engineer, re-examined busbar protection policy for the first time in twenty years and compared practices across its UK and US transmission networks. The review was concluded with the publication of an internal National Grid Technical Report and informed the recent revision of busbar protection application policy, outlined in the revised policy statement. This paper outlines the findings of the Technical Report and the justification behind recent policy changes within National Grid. These are summarised below: Duplicated busbar protection systems on new build substations at 275kV and above 132kV and below specified on a case-by-case basis, subject to system criticality and station size Duplicated distributed or process bus architecture required on asset replacement Circuit-breaker fail protection to be housed in bay level hardware (external to the busbar protection) where possible High impedance electromechanical technology is not precluded.