Before fault-finding, a visual inspection and assessment of the failed component must decide whether the work can be done de-energized. For fault-finding on or near exposed live parts: assess the risks and decide whether isolation, barriers or a safety observer are needed; only competent persons may do it; controls must stop a worker touching two conductors at different potentials, or a conductor and earth, at once; suitable, well-fitting PPE in good condition must be used; the work must be done from a stable position; test equipment must be confirmed suitable and working, correctly selected and ranged (HB 187 gives guidance); the risks of bridging safety or control interlocks, unintended starting or energization, bridging terminals and forcing contactors, interlocks or software interlocks must be considered; care is needed not to open-circuit a current transformer secondary and when inserting fuses or closing links under load or suspected fault; unfinished work must be left safe; and equipment must be returned to its original state or changes assessed by a competent person. Cables must be discharged to earth after testing, and a removed MEN link must be reinstated.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.