Anyone have experience with three position switches at HV and EHV level? How are safety rules written to provide isolation and grounding?
Is it preferable to have a separate disconnect switch and a separate grounding/earth switch?
It is a part of a specification I am reviewing for a GIS. The vendor is proposing a 3-position switch, which combines a disconnect with grounding switch.
I looked at IEEE C37.122 standard and C37.122.1 guide and both are silent on that. I have not seen it used in the US in switchyards.
The standard guide shows a one line with separate ground and separate disconnect but the standard does not explicitly spell that out.
The vendor is contending that the three way switch gives the same functionality.