Requirement for spacing between bus bars in 600V switchgear
Requirement for spacing between bus bars in 600V switchgear
(OP)
Could anyone steer me in the direction of the minimum distance required by code (N. America) between copper busbars in 600V switchgear?
Also, is the requirement for aluminium bus dufferent from that of copper bus? (Assuming Al is used for such an application).
The Standard Handbook for Electrical Engineers gives only the distances for High and Extra High Voltage equipment, and my Google searches yield nothing relevant.
Thanks.
Richard Byrne.
Also, is the requirement for aluminium bus dufferent from that of copper bus? (Assuming Al is used for such an application).
The Standard Handbook for Electrical Engineers gives only the distances for High and Extra High Voltage equipment, and my Google searches yield nothing relevant.
Thanks.
Richard Byrne.






RE: Requirement for spacing between bus bars in 600V switchgear
Don't forget the mechanical bracing to withstand the magnetic forces under the maximum asynchronous fault current.
RE: Requirement for spacing between bus bars in 600V switchgear
Noted that for short air clearance, the withstand voltage is around 300kV/m (7.2kV/in). For 600V class the switchgear is often tested to witstand a power frequency voltage of at least 2.2kV = (2x600V+1000V).
Most bare busbar configuration in air inside metalclad switchgear complies with this requirement with sufficient safety margin with approximately 1-inch clearance phase to phase or phase to ground.
For insulator covering or supporting the bus such as bushings clearance in term of creepage distance is typically around 2 inches.
RE: Requirement for spacing between bus bars in 600V switchgear
I was once told that 1" was required between adjacent phase bus bars, and given that I learned that the dielectric strength of air is approx. 3kV/mm (7.62kV/in), 1" is more than enough. But I was just curious about what the code requirement was.
Thanks again,
Richard Byrne.
RE: Requirement for spacing between bus bars in 600V switchgear
1" p-p is required under CSA. Most manufacturers also use 1" p-g to cover faults on impedance grounded systems.
Regards,
TULUM
RE: Requirement for spacing between bus bars in 600V switchgear
RE: Requirement for spacing between bus bars in 600V switchgear
As backup of alehman's response, read #59 of these Powell Technical Briefs, http://www.powl.com/main/Uploadpdf/ptb_1_91.pdf
But alehman, does it actually say that in UL-891 or are you going from memory? I no longer have a copy of that standard but I used to and I don't recall having seen that.
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Requirement for spacing between bus bars in 600V switchgear
btwn live parts of to ground
opposite polarity
through air over surface
0-125V 0.5 0.75 0.5
125-250V 0.75 1.25 0.5
250-600V 1.0 2.0 1.0