Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations KootK on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Metal Clad Switchgear 1

Status
Not open for further replies.

CuriousElectron

Electrical
Jun 24, 2017
182
Greetings,

Can a typical Medium Voltage Switchgear Breaker compartment accommodate two sets of 500KCMIL feeder cables? I'll have to double lug the load side of the MV circuit breaker, since I have a looped primary system(two feeders supplied by the breaker). I looked at Eaton section views of the switchgear, it appears there should be plenty of space for terminations and pulling in the secondary(rear) sections of the lineup. Just need to specify double lugs in the Specification. With this arrangement, I don't think I'd need a separate transition section.

Thoughts?

Thanks,
EE
 
Replies continue below

Recommended for you

It should be possible, but a quick inquiry to a manufacturer should get you a definitive answer.
 
Howdy Curious Electron,
I think what you are describing above is commonly referred to as a bifurcated feeder. Yes , you can do this. But keep in mind that you will almost certainly require two (2) sets of CTs and two (2) protective relays.
GG
ps What are the loads that these two feeders will be supplying.

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 
Hello, GG
Is the reason for the two sets of CT's is to protect each bifurcated feeder against low-magnitude faults and provide proper sensitivity to the protective element? The problem I see now is even if the individual relay is set for a certain overcurrent setting, if the sectionalizing switches downstream isolate one of the loads, now you have potentially desensitized your relay.
The loads are looped MV inverters.
Regards,
EE
 
A one-line might help. I know exactly what GG's bifurcated feeder is, but that's not what I initially pictured. Two cables because the load is too much for one cable or two cables to two different loads? If two loads, are there two sets of CTs and two sets of relays or is there one set of CTs and one set of relays (I've seen both)? With out a good picture you could get a very good, but totally irrelevant, answer.
 
I've attached the single line.
I think scenario 2 provides better sensitivity to high impedance faults, although I'm not sure how the CTs would be physically supported, since the MV switchgear typically has a cable compartment separate from the bus compartment in the back of the lineup.

Looped_Primary_Feed_mv4ufd.jpg


Thoughts?
Thanks,
EE
 
Scenario 1 probably allows for better CTs while scenario 2 makes it easier to figure out where the fault is. In scenario 1 the CTs are on the breaker bushing and the mounting is taken care of. In scenario 2 the CTs have to be in the cable compartment, can't be easily mounted, and probably have to be physically smaller. The "right" answer depends on lots of additional factors; available fault current being one of them as it affects CT performance.
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor