Add a feeder on a 13.8kV switchgear

[tem1234]

Hi

We have a 13.8 kV switchgear with a main breaker, a utility metering and the 4 feeder with a breaker each. All the network is underground.

We want to add a feeder, but we cannot just add a cell at the end of the switchgear because of space. We can only add a cells 100 ft away from the switchgear

so how can we do this. We thought to connect a teck cable just after the utility metering, and run it 100 ft away to another cells and there put a breaker. But the teck cable will only be protected by the main breaker of the switchgear, and i'm not sure we can do this, can we? we are in Canada and i didn't see anything about it.

Another option is to connect the new feeder on the load side of a breaker with another feeder already there. Maybe add a set of ct on each feeder to be able to locate a fault. But there again, maybe we will have a space problem.

Do you have any idea?

thanks

 

[Hoxton]

Can you add a "bus end cable box"? Then you can loop this to an incomer feeder on a new board elsewhere?

 

[tem1234]

Hi Hoxton,

I'm not sure that i understand what you mean by "bus end cable box".

The last cell of the unit is already close to a wall, so we cannot add a cell at the end. Do you put the cable box on the top of the switchgear and how do you protect the cable?

Thanks

 

[trosepe]

With the limitations you describe; the only way to do it properly is to intercept one of the existing feeders and install a two(stacked)vacuum circuit breaker section at the interception point. The new two circuit breaker section is only 36" wide x 91" high. Pull in new (largrer)conductors from the existing feeder circuit breaker to the new two breaker section. Replace the existing CT's and reset the relay at the existing feeder to protect the new, larger cable. Connect the feeder you intercepted to one of the new circuit breakers and use the other for your new load. This is more costly but maintaines good system coordination.

 

[Hoxton]

Depends how close to the wall you are. There will probably be a removable plate at the end of the switchgear in line with the bus bars in order that you can extend the board by putting in another panel. It may be possible to make up a cable box to fit this. Yoyu are right in wondering how to electrically protect the cable. Differential, with CT's in the cable box?

Otherwise consider tem1234's suggestion

 

[Electic]

13.8kV switchgear is not a good place for compromise. To terminate a cable will require specific dedicated space. To properly protect such cable will require a specific dedicated circuit breaker or fuses, again that will take more space. Something might be possible with separate CT's and differential protection but that kind of scheme would not hold up well in front of a forensic jury.

I suggest you take one of the existing feeders out of the switchgear and use that position to feed a new section of switchgear with proper number of breakers to feed the new load and the dislocated existing feeder.

Or, if the existing switchgear is single high construction, it might be possible to replace in the existing space with two-high construction that has sufficient number of breakers.

None of this will be inexpensive, but 13.8kV is not to be triffled with.

 

[tem1234]

Thank you all for your input.

The other problem is time too, the client need it pretty quickly.

We'll go to see the switchgear, we will probably try to add the new feeder with another one already there, the 2 feeders connected to the same breaker with one set of ct on each feeder to locate the fault if there is. A guy told me that it will be dificult because of space, and we will have to add another conduct, but we will see what we can do.

thanks

 

[EEJaime]

tem1234,
It would help to get added information, your field trip will provide you with good information. Look at any available space adjacent or within a few feet of the existing board. See if it is possible to add a section to the rear of the board. Is it both front and rear access? Can you change out the last breaker cubicle to install a two-breaker section?

Can you up-size one of the breakers and feeders and then sub-feed your new load from a breaker where the upsized feeder terminates?

A physical layout would be great. Also what kind of switchgear: draw-out, metal clad, one breaker per cubicle, manufacturer?

Good luck with your research. Keep us informed.

EEJaime