600V 3Ph GFI Delta

Not exactly. Your 600V system is ungrounded delta? Does it have ground fault detection? Shouldn't that protect against ground fault on this (branch) feeder?

Or when you say delta do you just mean the feeder is 3 phase 3 wire, though the 600V system is grounded? If so, a 100A MCCB (or fused switch) w/ GFI trip should do though I would guess the cost between one thousand and several thousand dollars.

Correct .... system is ungrounded and supply is a delta connected secondary three phase three wire.

Looking for molded case breaker with built in GFI ... are these available? Manufacturer? Cost?

Fred

If your system is ungrounded delta then a breaker with GFI doesn't sound like the correct animal for you. You should speak with the service outfit who does servicing on whatever brand of gear you have, they may be able to recommend something. Maybe a shunt trip breaker and some residual current sensing / relaying would get you what you want. What happens, at present, if one ground fault occurs somewhere on your 600V system? Warning buzzer / lights?

I should mention that I seem to recall that there is an important difference between a breaker rated 600V 3P (suitable for ungrounded delta as each pole is rated for 600V from ground) and a breaker rated

That sounds like a heck of a welder at 600V 3P 100A. Or is the feeder just extremely long.

Yes, was hoping to use a shunt trip breaker with a ground fault sensing circuit capable of tripping the shunt trip molded case breaker.

Actually the feeder is intended for a bank of about 5 welders working in a wet environment along with some sump pumps at 3ph 600V.

Trying to put together a bill of material to get this started.

Thanks for sharing your thoughts.