ECN Forum Forums Technical Discussion Electrical Theory and Applications Ohhh You Dirrrty Insulatorzzzz!

Around 415V maybe? Now where have run into that voltage before?

What I believe Scott35 is describing is a three-phase four-wire delta configuration, but at double the voltage of the usual “240/120V 3ø 4W∆” system. See lower left illustration at 6L6.net/localuser/busbar/imag/eei10.distckt.jpg

It has been used in some cases to skirt the NEC 230-95 service-entrance ground-fault protection mandated for ‘1000+ ampere’ 480Y/277V systems. It is the worst combination for a grounded 480V system, because 277-volt overcurrent devices cannot be safely applied, similar to the problematic corner-grounded 480V-delta system, but it still has the potentially disastrous capability of switchgear arcing-ground-fault burndown recognized {and normally protected for by GFP} in 4-wire 480Y/277V solidly-grounded systems.

{The mutant ‘480/240V 3ø 4W∆’ system is used occasionally by some utilities in the US, but should have 3-element metering to correctly register energy use as in other 4-wire solidly-grounded systems—with careful understanding of limitations.}




[This message has been edited by Bjarney (edited 01-06-2004).]

Correct - as Bjarney mentions I was refering to a 3Ø 4 Wire Delta - with Center Tapped winding, of the "Double Voltage" family.

I found 240 VAC on two of the three Phase Lines - as measured L-G, and on one Phase Line, found "More Than 240 VAC to Ground" - and since this smells "Delta-Ish", one could figure the Voltage to Ground on that single Maverick Phase Line to be in the area of 415.68 VAC
(240 × 1.732)

First thing I was thinking when there was a Voltage to Ground measured (with a Wiggy), was a Wye setup - having the Common Star Point Grounded. Finding >240 VAC to Ground on one Phase Line was totally unexpected, and debunked the Wye concept!

This was a nice "Whaddaheck" experience to me, as it was so totally unexpected!
(however, the guy I was working with found this to be of no interest, which really bummed me out!).

Bjarney;

The Image referenced in the last post didn't have "Image Tags" enclosing the URL (as far as I can see).
Let's see if it shows up in this message with tags surrounding it.



If it does not work, maybe you can try something else, enclosing its URL with image tags.

FYI, this looks like:

[img] URL to reference [/img]

Only, do not use any spaces like I have done here (did this to eliminate the BB software from going Berserk trying to figure out that tag!).

Scott35

Ooops on my part... "http://" was incorrectly stripped by me.
http://6l6.net/localuser/busbar/imag/eei10.distckt.jpg

If you copy and paste " 6l6.net/localuser/busbar/imag/eei10.distckt.jpg " into the IE address field it works.

An alternate [color!] version is http://home.att.net/~benmiller/elecsys.htm
"CENTER-TAP GROUNDED DELTA" illustration—second three-phase four-wire configuration




[This message has been edited by Bjarney (edited 01-07-2004).]

Scott,

Okay, it's an optical illusion then, because in the first picture it looks like the trees and the pole are right up on the roof, touching it actually!

Bjarney,
How would you place an EWP to "come up" to this particular pole?.
Given all of the messenger wires.

Maybe drive it up to the roof and approach it from the top? ;-)

[ ? Elevated Work Platform ? ]




[This message has been edited by Bjarney (edited 01-10-2004).]

Whoa!!.
LOL
So there are still people out there that have the same way of thinking as me!.
BTW, Bjarney, sorry 'bout the use of the term EWP, most normal people would call it a Bucket Truck, which it is really!.