A 12.47 kV feeder is built as a four-wire multigrounded wye, the most common form of US distribution. A new tech standing under it asks a fair question: what voltage sits on each phase conductor relative to the grounded earth they are standing on? Before you read on, pick one: is it the full 12,470 V, or is it 7,200 V?
The answer is 7,200 V, and the reason is the grounding. On a wye system the phase conductor never sees the full line-to-line value against earth. It sees the line-to-ground voltage, which is the line-to-line value divided by 1.732. So 12,470 / 1.732 is about 7,200 V, and that is the stress on the insulation, the arrester, and the lineman’s clearance from that conductor to a grounded surface.
What makes it multigrounded is where the neutral touches earth. A four-wire wye carries a neutral alongside the three phases, and on a multigrounded system that neutral is bonded to earth at the source and again, repeatedly, at poles and transformers all the way down the line. That repeated bonding is what holds the neutral near earth potential everywhere, so a grounded neutral fixes each phase at the line-to-ground voltage above earth the whole length of the feeder.
This is not a trivia point for a buyer or a relay tech. The line-to-ground voltage that grounding sets is the number arrester MCOV, cable insulation level (100 versus 133 percent), and ground-fault 51N relaying are all chosen against. Get the grounding mode wrong and you spec the wrong arrester and the wrong cable. It is the silent prerequisite that the protection and equipment tracks lean on later.
Contrast that with an ungrounded or delta system, which has no neutral reference to earth. A single line-to-ground fault there does not blow a fuse right away. With no low-impedance path to ground, the faulted phase ties to earth and the two healthy phases shift up toward the full line-to-line voltage above ground. The system can keep running, but every conductor’s insulation now has to withstand that higher stress, which is exactly why grounded wye won out for most US distribution.
Power factor penalties, reactive charges, and %Z mismatches show up as real line items on a utility bill or a bid rejection. DistroForge Insider applies these fundamentals to pricing and equipment-selection intelligence.