Transformers should have a non-intrusive visual inspection at least yearly (leaks, fluid level, enclosure tidiness, cable boxes, ventilation, weeds cleared from external enclosures) under a limitation-of-access document. Breathers should be inspected and desiccant replaced on colour change; insulators cleaned, tanks painted and temperature gauges and alarms checked; air-cooled units inspected annually for dust and cleaned under permit. Fluid-filled transformers should be sampled annually to track condition and trends. Earth protective conductor continuity should be measured; thermal imaging may help.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.