Utility Owned vs Customer Owned Transformers Pros vs Cons

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Besoeker

Besoeker

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UK
iwire said:
In my opinion let the utility own it.

They will handle replacement, the running costs etc.

On the other hand if the customer owns it the customer will also have to provide and handle the upkeep of a MV service disconnect and OCP.

I see no benefit at all unless the customer has other uses for MV
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Yep. I agree with that. Let the utility pay for upkeep and energy consumtion. It may be low - around 2% but why pay for it if you don't have to...
And for residentiak and commercial where there is no need for MV, that has to be the better option.

At the risk of being admonished yet again for expanding the topic I'll throw in one more consideration.
The PCC. Point of common coupling. If you have dirty power electronics better to keep it in your own back yard.
IMHO of course.
 
jtinge

jtinge

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Location
Hampton, VA
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Sr. Elec. Engr
philly said:
This is usually what I see as well. Large industrial commercial/industrial complex that has a utility service entrance at the distribution voltage and then overhead lines that drop down into various service entrances. Are these really considered service entrances anymore if all these service entrances are behind the main utility meter where the overhead lines come onto the property? I have seen cases where the utility lines come onto the property, hit a utility meter and then travel overhead on property to various riser poles where there are gang operated switches, and fused cut-outs before it drops down to a transformer. What is considered the "service entrance" in this case?
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It depends on the location of the service point location. If the overhead or underground cables come from the load side of a customer owned over current protection device like in a customer owned substation that is supplied by the utility, then all those cables would be feeders and would fall under Art 225 requirements. If they fed transformers, then those transformers would be separately derived systems and you would follow Art 250 requirements for system bonding jumpers instead of main bonding jumpers.
 
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jim dungar

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Please stay on the topic of transformer ownership.
We can move to a new thread if you would like to discuss forum policies.
 
Besoeker

Besoeker

Senior Member
Location
UK
jim dungar said:
Please stay on the topic of transformer ownership.
We can move to a new thread if you would like to discuss forum policies.
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Well said that man.

I mentioned the harmonics issue in that it may be a consideration when deciding about ownership. The high voltage side will have a lower impedance and thus LV percentage THD won't be reflected on the HV side.
 
P

philly

Senior Member
electrofelon said:
I dont think that would fly. I think you would have multiple issues with definitions of various things. Also I am not sure if these transformer integral disconnects are rated for load breaking? Maybe others will have some comments here.
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I cant seem to find anything in the NEC that would prevent using this internal VFI switch as the service disconnect. In fact Exhibit 230.30 in the 2014 NEC handbook appears to illustrate this exact case with the service disconnect integral to the customer owned transformer.

I did check and this switch is rated for load breaking capacity.

So what defines exactly where the "service point" is weather its on the primary or secondary. Is this usually recognized as wherever the utility has their metering installed?
 
electrofelon

electrofelon

Senior Member
Location
Cherry Valley NY, Seattle, WA
philly said:
I cant seem to find anything in the NEC that would prevent using this internal VFI switch as the service disconnect. In fact Exhibit 230.30 in the 2014 NEC handbook appears to illustrate this exact case with the service disconnect integral to the customer owned transformer.

I did check and this switch is rated for load breaking capacity.

So what defines exactly where the "service point" is weather its on the primary or secondary. Is this usually recognized as wherever the utility has their metering installed?
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I am curious about using the transformer disconnect/OCPD as the service disconnect. I could also not find anything that specifically disallows it other than 230.82. There is also 230.66, but I think we are talking MV here so that wouldnt apply. Perhaps someone else will comment.

IMO Metering doesnt effect the location of the service point. Note that most self contained meter sockets are located on the NEC side of the service point (around here anyways). We also frequently have CT cabinets on the NEC side of the service point. I would say that nothing defines the service point, it is just a point that is declared and is. On the supply side of it the NEC does not apply and the utility owns the equipment, and the opposite on the load side.
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I would also point out that if the utility owns the transformer they have to handle the work on the MV side of it.

A fair number of electrical contractors (especially smaller ones) are not well experienced in dealing with MV so you may wish to make it the POCO's problem.
 
Tony S

Tony S

Senior Member
Location
Resting under the Major Oak UK
petersonra said:
A fair number of electrical contractors (especially smaller ones) are not well experienced in dealing with MV so you may wish to make it the POCO's problem.
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That’s a problem wherever you are. Before I retired, every three years I had to go on a training course with the local DNO (PoCo) to carry out switching operations. Does the US have a similar system?

Our electrical regulations BS7671 don’t cover MV, you have to follow BS7430 (private network operator code of practice).
 
mbrooke

mbrooke

Batteries Included
Location
United States
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Technician
iwire

iwire

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Location
Massachusetts
electrofelon said:
Not really sure what you mean. Thats the way it is in the states. Most electricians and EC's dont do MV work. I can pull MV cables and put on a load break elbow, but thats about it for me.
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Pretty much the same for me at the companies I have worked for.

We will pull the MV cable and sub out the terminations and testing.
 
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