C phase on detail burnt up...again

[Local134 sparky]

We are replacing a 1200amp 3phase main breaker again, to the day this was replaced exactly a year ago at a pump station and same issue. The C phase detail connection from breaker to bus, with properly torqued factory replacement carriage bolts melted to nothing. Voltage is 480v, all loads are 3 phase and balanced, we are stumped. The piece fed info from plant employees, was utility company had a surge and blew fuses at there transformer just outside building, and that's when the generator took over. Utility company got us online again, and generator would not shut off, checked line voltages, good, load good, get to ATS further down gear and line side nothing on C phase...cause the buss was blown. Before adding more surge protection, another 1200amp breaker, anyone have any clue on the cause? Like I said, last year after we replaced, all phases balanced and voltages were perfect.

 

[Elect117]

Is this a grounded system? 277/480V or 480V 3W (no ground)?

 

[jim dungar]

Is the breaker failing or it just the bussing?

 

[retirede]

Remote forensic analysis is really difficult.

 

[kwired]

The C phase detail connection from breaker to bus, with properly torqued factory replacement carriage bolts melted to nothing.

What was replaced besides the breaker? If anything that was left in place happened to have been overheated to some extent, it could been compromised enough to start the second failure.

 

[ptonsparky]

Remote forensic analysis is really difficult.

 

[hillbilly1]

Remote forensic analysis is really difficult.

Tell me about it! That’s why I had my previous employer switch everybody to IPhones so we could FaceTime. Saves a lot of time!

 

[jim dungar]

Tell me about it! That’s why I had my previous employer switch everybody to IPhones so we could FaceTime. Saves a lot of time!

We video call all the time between Android and iphone and have been for quite a while.
Recently we have been using Google Meet.

 

[hillbilly1]

We video call all the time between Android and iphone and have been for quite a while.
Recently we have been using Google Meet.

We had Android’s, but you had to reboot them every couple of days.

 

[jim dungar]

We had Android’s, but you had to reboot them every couple of days.

How old, and what brand? I have been running Android video calling on Samsung, Pixel, and Kindle Fire for more than 5 years.

 

[hillbilly1]

How old, and what brand? I have been running Android video calling on Samsung, Pixel, and Kindle Fire for more than 5 years.

This was about 10-15 years ago.

 

[pipe_bender]

We are replacing a 1200amp 3phase main breaker again, to the day this was replaced exactly a year ago at a pump station and same issue. The C phase detail connection from breaker to bus, with properly torqued factory replacement carriage bolts melted to nothing.

The only time I ran into that was with old Aluminum Busbar, check that every nut bolt and screw is properly rated for the metal its attached to?

 

[zbang]

This was about 10-15 years ago.

Android has changed a bit since then (my phone and tablets only reboot for system updates).

 

[ptonsparky]

FWIU, we should be restarting our phones periodically.

 

[hillbilly1]

Android has changed a bit since then (my phone and tablets only reboot for system updates).

I think it was our IT department screwing with them. IT guys always think they can make things better, but usually screw things up. Apple doesn’t let you do that easily.

 

[Local134 sparky]

What was replaced besides the breaker? If anything that was left in place happened to have been overheated to some extent, it could been compromised enough to start the second failure.

First one a year ago, blew out the back of the breaker behind C phase, old breaker was a Westinghouse NCG, replaced with Eaton/C-H recommended replacement, which came with factory hardware. At the time we just assumed since the breaker ran its life being from 70's. Detail was not changed as it was fine and not effected, during shutdown we torqued all detail to recommendation through out gear.

 

[Local134 sparky]

Is the breaker failing or it just the bussing?

First go around was just breaker, buss was cleaned and torqued throughout gear, this time it was so severe it was breaker and buss detail.

 

[Local134 sparky]

Is this a grounded system? 277/480V or 480V 3W (no ground)?

3phase 4w

 

[Elect117]

3phase 4w

Heat gun while energized (if you can do so safely). It sounds like loose bolts or overloaded connections (to me). I would rule those out.

 

[ptonsparky]

Already damaged buss bar that was cleaned and reused when it should have been replaced.