4.1.5 Instrumentation associated with protection and control equipment
This comprises instrumentation used in conjunction with a control loop, either locally or for the main plant control systems. The turbine governing system (described in Section 1 of this chapter) is an example of the latter, whilst any local control loops not covered by Auxiliary Systems form part of the former.
These local controls are used to operate plant prior to a unit start-up or following maintenance, where operator action from the control room is not necessary. Also, some plant requires controls which may not be immediately connected with the minute-by-minute operation of the unit. Further local controls are sometimes needed to permit a detailed fault analysis to be carried out following identification of a problem in the central control room.