ABB ZX0 Manual For Installation And Operation page 31

Remove the earthing screws of the e-n windings
from the terminal boards of the voltage transformers
in accordance with the circuit diagrams (figure
2.3.5.2.5) or earth the e-n windings using the earthing screw
(figure 2.3.5.2.6).
Earth the circuit at one point only.
Fig. 2.3.5.2.5: View of the terminal board of a voltage transformer with e-n
winding: Earthing screw (arrow) in isolated position (no earthing)
Fig. 2.3.5.2.6: View of the terminal board of a voltage transformer with e-n
winding: Earthing screw (arrow) in earthing position (dn terminal earthed)
Manual ZX0 HB 600 en - Revision 05 | 31