[R-390] Re: Electrical panels and grounds...

[Kenneth G. Gordon]

This thread reminds me of a short story Roberta Barmore told us 
on the Glowbugs list a while back. She is Chief Engineer at a big 
combined AM/FM/TV station in the midwest somewhere, and a 
ham.

She was walking by the main three phase panel which fed power to 
the entire transmitter site and noticed that it seemed to be 
somewhat warm. Then a few evenings later, she thought she saw a 
slight reddish glow, so she called an electrician. 

He showed up the next day, and after putting down some thick 
rubber mats, and removing the panel, crawled back in under the 
panel and looked up. 

Her words were, "...then he said a very bad word and backed out 
slowly..."

Apparently the center one of the very large copper buss bars was 
glowing red hot. When the panel was assembled at the factory, the 
assembler had misaligned the center buss bar when drilling the 
mounting holes in it and had offset it to one side or the other by 
quite a distance. There was a very small gap between it and one 
next to it. Further, the bolt holes were damaged in such a way that 
the bolts couldn't properly clamp the buss bar to its mount, so the 
current carrying capability of the buss bar was signifcantly 
lessened. So much so that it heated up with the current load and 
loosened the bolts, making it hotter yet, and so on.

They had to cut the station power WAY back to keep the panel 
from burning up while waiting for the replacement panel.

Ken Gordon W7EKB