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Jul 10, 2007

Guide to critical power

A 66-page guide to critical power from BITS, although intended for US-based financial institutions, is broadly applicable. It outlines the electric grid system and points out that much of the critical infrastructure is exposed to adverse weather and even terrorist attacks. It goes on to provide a 225-question checklist but without model answers (though it's not exactly hard to figure them out).

On page 15, the guide points out a hidden drawback in over-engineering power systems:
"For modern critical facilities, the benchmark availability is in the range of 99.999% (“five nines”) to 99.9999% (“six nines”). To achieve six nines availability, the engineered systems will have to incorporate designs that include system+system [2(N+1)] redundancy. It is worth noting that engineered systems in a critical facility are often over-designed to include too much redundancy. That is, systems become more complex than they need to be, which leads to decreased reliability."