×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Arc on transformer bank

Arc on transformer bank

Arc on transformer bank

(OP)
Meterman and ape. changed a 480 volt meter at a water well. It is a 3 Ø 240/480 center grounded delta on the low side. High side is 14,400. Lineman grounded the high side before opening the cutouts. My question is when they closed the fuses in, they closed the 2 outside fuses in first. The center transformer was the one that was grounded, x2. When they shoved the center in, they missed and the barrel was swinging drawing a 3 to 4ft. arc. No load on this, as breakers were off. Why such a big arc? Thank you, Bob

RE: Arc on transformer bank

Was the primary neutral floating or connected? Did the primary neutral have a temporary connection to avoid switching surges? (Four cutouts, A,B,C and N. Neutral cutout is closed first. After A,B, and C are closed, the neutral fuse holder is opened and removed.)

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Arc on transformer bank

(OP)
Temp. connection. 2 hot line clamps on #6 copper wire. One clamp on the floating high side, other clamp on the copper for the tank grounds. Thank you, Bob

RE: Arc on transformer bank

The primary voltages were probably not equal. It is a characteristic of the four-wire-wye:delta that the transformer or transformer bank will try to balance unequal primary voltages and or phase angles. On long rural lines with single phase voltage regulators, there are often equal line to neutral voltages but a combination of unequal phase angles and unequal phase to phase voltages. These conditions will cause a circulating current in the delta and fairly large currents in the line conductors. Once the transformer bank is on-line the wye point or neutral jumper is removed, the circulating current and the associated heavy line currents will disappear. You will only have magnetizing current until you close the load breakers.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Arc on transformer bank

(OP)
Thank you, waross. Bob

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources