Service Equipment for Medium Voltage

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enteng14

enteng14

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Manila, Philippines
Good day!

I would like to inquire regarding service equipment for medium voltage ie. 34.5 kV. The proposed installation uses loadbreak switch (LBS) as disconnecting means and power fuse as protective device both installed in pole for overhead service.

My query is about the number of power fuses used. After the LBS each phase conductor branch-out two wires with power fuse used in each wire. These power fuse are not in parallel since they served different load (transformer).

There are two power fuse in each phase after the LBS and served different load. The common installation is there is only one set of power fuse for each LBS.

Can these be considered as service equipment since there are two fuses after a single service disconnecting means?

Thank you
 
For medium voltage services, the service disconnecting means and the "main" overcurrent protective devices are allowed to be two separate pieces of equipment.

I recently designed an installation where the air-break service disconnect was on the "utility" pole and the (2) sets of fuses (for loop A and loop B) were located in a padmount enclosure.
 
Service voltage = 34.5kV
Number of customer-owned tansformer = 2 - 1000 MVA
Number of load break switch = 1
Number of power fuse per phase = 2 sets (1 set for each transformer)

Is there no violation in the NEC about this installation?
What I know is that a service equipment is composed of sets of disconnect and power fuse. On this case, there is single disconnect and there are two sets of power fuse. I try to compare it to a circuit breaker and could not figure it out because a circuit breaker has also a single disconnect and overcurrent device.

Can this installation (one LBS and two sets of power fuses) considered as service equipment?
 
enteng14 said:
Is this a violation of the Code?
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In my opinion, no. 230.205(A) seems to elude to a single disconnecting means; however, 230.205(B) states, "Type. Each service disconnect shall simultaneously disconnect all ungrounded service conductors that it controls . . ." I believe you may have multiple (6?) disconnecting means but the Code doesn't clearly say that.

Whoever the AHJ is in your area, talk to him/her and verify before you build something that has to be torn down and rebuilt. :)
 
Thank you sir for the reply.

I know that service equipment is compose of a service disconnect and an overcurrent protection, but does this configuration considered as service equipment?

It has one service disconnect but have 2 sets of fuses that serve different load.
 
I, personally, do not see a problem. In the diagram, it looks like you have a set of ground operable ganged, disconnecting switches and a couple of sets of cutouts with fuses installed; is that the case?

I would like to see an engineer jump in and answer or verify my answer to this question. I have worked in electric utility engineering for 38 years and am on Code Making Panel 10 but I am not an engineer. :)
 
charlie said:
I, personally, do not see a problem. In the diagram, it looks like you have a set of ground operable ganged, disconnecting switches and a couple of sets of cutouts with fuses installed; is that the case?

I would like to see an engineer jump in and answer or verify my answer to this question. I have worked in electric utility engineering for 38 years and am on Code Making Panel 10 but I am not an engineer. :)
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Yes, you are correct sir, it has a gang-operated loadbreak switch and two sets of cutouts that serves different transformers. My question is, can this be considered as the service equipment despite having couple of fuse cutouts?

I'm overwhelmed on your experienced in utility and in CMP despite a non-engineer person but have a vast experience.
 
enteng14 said:
. . . it has a gang-operated loadbreak switch and two sets of cutouts that serves different transformers. My question is, can this be considered as the service equipment despite having couple of fuse cutouts?
Click to expand...


I would still like for an engineer to verify my responses.​



In my opinion, this is fine. Thanks for the kudos. :)
 
jim dungar said:
This sounds alot like what I said I have designed (see post #3).
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Sorry Jim, I missed your response. It is difficult to see when your head is . . . and the sun is not shining there.
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