MV drive safety key interlocking

[thinker]

Please advise is there any governing document or standard in US (ANSI,IEEE,NEMA) that makes mandatory usage of key interlocking provisions for MV drives? Specific question: the separately (from drive) installed MCB must be key interlocked in OFF position allowing access to MV drive cabinets, or it is enough to switch the MCB OFF, then lock it out (with padlock), and tag out in the OFF position? We understand that key interlocking is more foolproof solution, but is it mandatory?