To Define a Cable Routing Override

Cable routing override is defined in Cable Routing > Cable Laying Methods section of the Options dialog.

Select the Add option at the bottom of the Cable Laying Methods tab.
New override section will be added at the bottom.
Change name to MV override.
Select the Single Layer method.
Set the Voltage Level to MV.
Click Apply to save. Notice that a raceway system can also be part of an override. If a raceway is selected then each time that raceway is placed in RW model it will use the cable routing method defined in this override.