Electrical Buss Duct
Electrical Buss Duct
(OP)
I am trying to benchmark best practices in the area of electrical buss duct testing for predictive / preventive maintenance. Here in our facility, we have 400 & 600 amp 480 volt three phase buss ducts supplying power to all of
our equipment and due to age and contamination, are beginning to experience ground fault and phase to phase failures in some areas. The only thing I know to do is to shut down the equipment, power down the buss and perform a
high-pot test. However, shutting down a whole section of buss is not an attractive solution. Infrared analysis has not been of much use due to ambient and reflected energy. I'm thinking about ultrasonic but don't know if that is a viable option.
Any help with this matter will be greatly appreciated.
our equipment and due to age and contamination, are beginning to experience ground fault and phase to phase failures in some areas. The only thing I know to do is to shut down the equipment, power down the buss and perform a
high-pot test. However, shutting down a whole section of buss is not an attractive solution. Infrared analysis has not been of much use due to ambient and reflected energy. I'm thinking about ultrasonic but don't know if that is a viable option.
Any help with this matter will be greatly appreciated.






RE: Electrical Buss Duct
Likewise for outdoor bus duct the weather tight integrity is important. Rust penetration or poor seals can get you.
I assume that if contamination is a problem then cleaning would also be part of your shut-down maintenance.
RE: Electrical Buss Duct
Production loss from electrical failures may spur replacement funding. It is very stressful trying to keep electrical distribution working any degree of reliability in aged equipment, particularly if maintenance has been a low priority. Unfortunately, sometimes it takes the cost of human injury to force the issue. Old bus duct is spooky stuff.
RE: Electrical Buss Duct
RE: Electrical Buss Duct
ANSI/IEEE C37.23
IEC 439-2
BS 5486: Part 2
NEMA BU1
etc.
RE: Electrical Buss Duct
RE: Electrical Buss Duct
If the bus duct is short in length you might consider replacing it. The time and money spent to find and repair the defective areas can add up fast and might lead to replacing all of the bus duct anyways.
If your getting ground faults and phase-to-phase faults, you’re in bad shape. I would get a testing specialist there to find out the integrity of the bus duct and will have a better understanding of your situation.
RE: Electrical Buss Duct
Depends if you have plant air, and can stand a continuous drain on it.
RE: Electrical Buss Duct
RE: Electrical Buss Duct
Check NFPA 70b, it may establishes requirements for this kind of maintenance. Again, I don't think any type of testing will effectively prevent failures from old bus equipment that is already failing. It will only give you a false sense of security.
RE: Electrical Buss Duct
http://www.ecmweb.com/ar/electric_ensuring_good_bus/
etc. for more info on bus duct intallation
RE: Electrical Buss Duct
RE: Electrical Buss Duct
You are fighting a loosing battle and only waiting for a disaster!
RE: Electrical Buss Duct
Assuming open plug style, chances are your environment has deposited significant contamination onto the support insulaters etc. I've has success in similar situations by doing a total shutdown, then physically cleaning ALL supporting insulation after removal (and cleaning) of all plug units. If your plant can stand it, high pressure washing with good water (call one of the pole line mtce wash crews in). Use a clean air hose to blow out and standing water, leave to dry 12+ hrs with low humidity, megger completely, downfuse to minimum then turn it on (fingers crossed, protective gear). I've used procedure on 800A and 1200A 600V ducts, no further problems.
Consider de-comissioning a small section of it before the shutdown. Tear it out, strip it down, keep for emergency replacement parts during main shutdown.
Use megger testing, not HyPot, which will likely create failures itself. An infrared camera might spot tracking from conductive contaminants on the insulation blocks, but thats pretty late to detect a problem. By the time a thermograph sees it, it will be too late to make the next scheduled shutdown. Visual inspection and regular recorded megger tests (keep records, record temp and humidity at test time, do it OFTEN) then monitor for trends, analyse records prior to any failure event.
If you have metalclad stuff failing, scrap it out unless you can see obvious points to upgrade.
RE: Electrical Buss Duct
http://www.parkdetroit.com/Busway%20Manual.pdf
for:
NON-SEGREGATED & SEGREGATED BUS DUCT INSTALLATION MANUAL
RE: Electrical Buss Duct
Good table of test voltages though. Agree with limiting test voltage to 1.65 kv for .635 kv equipment. Suppose a HyPot tester could be used if set properly, but when meggers are so much simpler, cheaper, (and rugged) that's what I'd use.