Falls die Schaltanlage in "Felder" aufgeteilt ist, geht es um diese. Sonst kann mit "Feld" auch eine entferntere Anlage gemeint sein.
Cf. field-wired vs. factory-wired (vor Ort oder werksseitig verdrahtet)
But consider also switchgear units:
EN functional unit (of an assembly)
a part of an assembly of switchgear and controlgear comprising all the components of the main circuits and auxiliary circuits that contribute to the fulfilment of a single function
NOTE – Functional units may be distinguished according to the function for which they are intended e.g.: incoming unit, through which electrical energy is normally fed into the assembly, outgoing unit through which electrical energy is normally supplied to one or more external circuits.
DE Funktionseinheit
Schaltfeld
http://www.electropedia.org/iev/iev.nsf/display?openform&iev...
The translation workplace 
