Recent developments in high voltage (HV) switchgear and their associated protections has prompted an accelerating movement towards the implementation of Dynamic Positioning (DP) facilities with closed bus capabilities. This shift in technology and classification society approvals has been in opposition to the accepted theories of oil company and drilling contractor management, where the acceptance of the "risk" of closed bus operations is often deemed to be too high to be acceptable. This paper focuses in two parts:

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1. An assessment of all IMCA DP incident reports from 2011 to 2015 for possible differences in the outcome of these real-world incidents if a closed bus philosophy was implemented.
    

2. A risk assessment case study of a new-build DP semi- submersible specifically designed, commissioned and acceptance tested in "Ring" bus configuration.