Overcurrent Protection for MV Feeders

[ron]

240.4 clearly indicates that conductors need to be protected against overcurrent in accordance with their ampacities ....
It specifically refers to 310.15 which is 0-2000V.
Where is the requirement for overcurrent and/or short circuit protection for conductors >2000?
240.4 doesn't specifically exclude conductors >2000V, but the reference to 310.15 leaves me with nothing to go by.

I have a 15kV feeder that I will protect with 50/51 protection (overcurrent and short circuit protection), but I'm trying to figure out for this vveerryy long radial campus feeder whether there is any way I can reduce the ampacity of the feeder as I go along from building to building and the calculated load is less and less.

Thanks

 

[dkidd]

I'm trying to figure out for this vveerryy long radial campus feeder whether there is any way I can reduce the ampacity of the feeder as I go along from building to building and the calculated load is less and less.

Thanks

Have you considered fused sectionalizing switches?

 

[david luchini]

Where is the requirement for overcurrent and/or short circuit protection for conductors >2000?

Article 240, Part IX. Overcurrent Protection over 600 Volts, Nominal.

 

[pete m.]

You may also want to check article 490 and 328 for some further guidance.

Pete

 

[ron]

Have you considered fused sectionalizing switches?

I have but the client is cheap and wants me to defend each decision. I first told them they were required and he said he didn't think they were. Now I need to double check with a code reference.

 

[ron]

Article 240, Part IX. Overcurrent Protection over 600 Volts, Nominal.

Thanks.
After calculating the short circuit currents, it would seem to be a real specialty item to compare the conductor/insulation temperatures with the conductor properties and then associate that with the upstream protection.

 

[masterinbama]

Will this help? I have used them before and the ampacity chart is also useful.

http://www.cooperpower.com/library/pdf/24097.pdf

 

[ron]

Will this help? I have used them before and the ampacity chart is also useful.

http://www.cooperpower.com/library/pdf/24097.pdf

Thanks
I'm trying to reduce the conductor ampacity without reducing the 50/51 relay protection (or fuse size). 240 says that the overcurrent can be set as high as 6 times the ampacity as long as the cable will be protected for short circuits.