Hello all, I have been at my current post as in house electrician for a plastics manufacturer for a little over 1 year now. I recently got my thermal imaging cert and we are very behind on updating our equipment status. That being said we have had 2 major arc flash incidents on GE Spectra busway. The first was a 400A bus plug for an IMM press back in July 2023 and the latest was 5/25/24. This last one was on a 600A bus plug for an IMM press. I don’t see any obvious failure points other than the flash itself. Does anyone know if this particular busway, GE Spectra 1200A, is prone to these type of failures and I need to begin inspecting the bus plug connections and applying copper never seize to those connections? Thanks for any input.
Busway flash at bus plug
- Thread starter Amfsparky
- Start date
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I don't know what you mean by "flash".
Was there an actual arc blast?
The reality is that the most likely cause of an arc flash is some kind of foreign body falling into the bus way. The stuff just does not explode on its own.
I doubt thermal imaging is going to do much. It is something that can help over a long term but it needs to be coupled with a good understanding of the actual loads in place at the time the imaging is done. Pretty meaningless to do thermal scans when there is little load and and compare it to scans done at peak load.
Incidentally, conductors and terminations can be uncomfortably warm but still quite safe. Temperature is not a real great indicator of what is safe or not.
Was there an actual arc blast?
The reality is that the most likely cause of an arc flash is some kind of foreign body falling into the bus way. The stuff just does not explode on its own.
I doubt thermal imaging is going to do much. It is something that can help over a long term but it needs to be coupled with a good understanding of the actual loads in place at the time the imaging is done. Pretty meaningless to do thermal scans when there is little load and and compare it to scans done at peak load.
Incidentally, conductors and terminations can be uncomfortably warm but still quite safe. Temperature is not a real great indicator of what is safe or not.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Many busway plug manufacturers have a recommended 'joint compound' which should be applied when ever a plug is moved/reinstalled. This compound is different than 'never seize'. Always follow the manufacturer's installation recommendation for torque values.
Small plugs ,usually 200A max, often plugin similar to panel board breakers and have relatively robust connections. 400A and 600A plugs often have a type of connection that must be torqued. 800A and larger units are almost exclusively torqued connection.
It is difficult to clean the assembled bus bars themselves, so pitted and dirty plug locations should not be reused. If there has been severe arcing resulting in internal soot accumulation, replacement of the affected busway section may be called for.
Small plugs ,usually 200A max, often plugin similar to panel board breakers and have relatively robust connections. 400A and 600A plugs often have a type of connection that must be torqued. 800A and larger units are almost exclusively torqued connection.
It is difficult to clean the assembled bus bars themselves, so pitted and dirty plug locations should not be reused. If there has been severe arcing resulting in internal soot accumulation, replacement of the affected busway section may be called for.
It was an arc blast where the plug connects to the bus. It appears one phase shorted to ground at the connections. This GE busway allows you to set the larger plugs on the rail and support them supplementally from hangers and then you rotate a bolt that pulls the fingers onto the bus plates.
Your suggestion about foreign bodies has merit, we have a lot of dust build up on top of equipment. I will suggest a more regular if at least annual vacuuming on the connections at shutdowns. Thanks
ptonsparky
Tom
- Occupation
- EC - retired
Are you adding carbon to you plastics?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Arc blast is not an industry recognized term. It is most typically used in conjunction with Arc Flash (NFPA 70E) safety, and in reference to things literally blowing up.
What you seem to be describing is an arcing fault/event which caused damage to equipment.
Good idea on routine cleaning.
No carbon, but there is resin dust. Plus the factory isn’t air conditioned so lots and lots of column fans and 20 or so roof exhaust fans
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
How old is the buss? Age and heat can deteriorate the insulator.
I’ve been told the estimated installation was 7 to 4 years ago depending on when the busway was upgraded. The manufacturing floor does get warm in the summer due to natural warmer temps and the heat generated by the injection mold presses. There about 22 GE busways throughout the shop, most of them are 1200 A with a couple 2000 A.
The busways are inspected at the joints by our maintenance contractor every 3 years I believe but I don’t think they look at the bus plugs. Our previous electricians would thermal image the bus and bus plugs but that hasn’t been done properly in 2 years now.
My concern is that 2 arc flash events in less than a year in very similar circumstances may be a trend that I need to mitigate. I greatly appreciate the help thus far and will definitely look into steps to prevent further incidents.
Eddie702
Licensed Electrician
- Location
- Western Massachusetts
- Occupation
- Electrician
Were these "arc flashes" caused by plugging in or unplugging a buss connection? After the arc flash was the buss plug pulled off and the buss and the plug in inspected for arcing and or burning and if so what was seen?
Or were the arc flashes see at an installed buss plug while in normal use?
Or were the arc flashes see at an installed buss plug while in normal use?
Great question. We are not permitted by policy to do any work on any equipment while energized so the plug was in place and operating at the time of the arc flash. It tripped the breaker for the busway and did not blow the fuses for the machine in the plug. Megged the wires from the plug to the machine and they were 520+ megaohm to 650+ megaohm