POCO and Voltage Drop Disagreement

[A-1Sparky]

Maybe they are giving you a hard time because you are not from the area. It happens.

Definitely a possibility. Although, the POCO manager told me that they've never granted a variance in the 25 years since the policy was implemented.

 

[kwired]

Definitely a possibility. Although, the POCO manager told me that they've never granted a variance in the 25 years since the policy was implemented.

Hard to believe they have such a policy if they serve industrial or agricultural customers whether big or small. If it is just a policy for dwellings I can maybe see it.

 

[A-1Sparky]

I believe it just applies to dwellings.

 

[mwm1752]

Will the POCO accept a 100A service with a 480' lateral using 250 MCM AL -- you are a 3% VD A 240V and that is based upon a continuous load of 90A. As long as your load calcs fit into the 90A NEC is happy.

 

[weressl]

I'm pretty confused myself. I've never done work in Vermont before and am used to dealing with the POCOs in my area of NY. I know people with 800' driveways who have 4/0s secondaries and have had no problems at all with voltage drop. POCO brought up the issue before connecting and made them sign a waiver releasing them from liability should voltage drop be a problem.

Ahh....welcome to the Peoples Socialist Republic of Vermont, where we still practice what the Soviets have abandoned.

 

[Smart $]

I believe it just applies to dwellings.

Idle speculation suggests the policy was made because of less-than-qualified persons putting in services with typical sized conductors, likely not even aware of voltage drop considerations. Rather than dealing with problems resulting from such, the POCO implemented the policy.

 

[tortuga]

Here is one for the utility engineers on this thread.
If I recall in the padmounts there is a primary current limiting fuse that has a minimum interrupting amps and sometimes a optional secondary "breaker" that can be adjusted?
Is there some point at which a bolted L-N fault will not draw enough available fault current to blow the primary current limiter (like a C10) ?

Say they put this service in as they should and size the service lateral as they do with the NESC and lower ambient temp 'k' value. Underground ambient of 20C K=17.3.
2/0 - 2/0 -1/0 AL? 90A load 500 feet one way voltage drop is 5.9% (standard utility stock wire) etc.
Say we have the optional 2.5% taps on the primary and we cant hit one without overvoltaging the closer homes.
So we are delivering 226V at the meter.

If you have a L-N bolted fault on the coldest day of the year 500' away at the meter base and its a 37.5 kva padmount 65C rise with a 1.93%z at 85C with a C10 fuse 2.4kv to ground primary. Or something standard like that.
How long would it take that primary to blow?

 

[hurk27]

Here is one for the utility engineers on this thread.
If I recall in the padmounts there is a primary current limiting fuse that has a minimum interrupting amps and sometimes a optional secondary "breaker" that can be adjusted?
Is there some point at which a bolted L-N fault will not draw enough available fault current to blow the primary current limiter (like a C10) ?

Say they put this service in as they should and size the service lateral as they do with the NESC and lower ambient temp 'k' value. Underground ambient of 20C K=17.3.
2/0 - 2/0 -1/0 AL? 90A load 500 feet one way voltage drop is 5.9% (standard utility stock wire) etc.
Say we have the optional 2.5% taps on the primary and we cant hit one without overvoltaging the closer homes.
So we are delivering 226V at the meter.

If you have a L-N bolted fault on the coldest day of the year 500' away at the meter base and its a 37.5 kva padmount 65C rise with a 1.93%z at 85C with a C10 fuse 2.4kv to ground primary. Or something standard like that.
How long would it take that primary to blow?

Shouldn't take a utility engineer to figure out what size bolted fault will hit the primary fuse at, I could do the math but kind of worn out as I just got off a 12 hour day, but first the primary fuse in most all cases are not set to protect the secondary conductors or even the transformer for that matter, the primary fuse is to protect the primary line ahead of the transformer, and in most cases where the utility is under the gun to have low outage ratings demanded by most state utility commissions, these fuses can be sized for 200% fault levels, in most cases they would rather have conductors burn free and drop on the ground then to have other customers out of power, here in Indiana this low outage level doesn't apply to CO-OPs just public/private utilities.

While conductor impedance can play a part in how the OCPD can react to a fault, but before you ever get to the point that a bolted fault will fail to open the secondary breaker you will have a extreme voltage drop problem

 

[A-1Sparky]

Just an update on my situation for you guys...

I met with the POCO's manager and head lineman on Friday and we came to an agreement. They are going to remove the existing transformer and replace it with a junction box. From there, they are going to extend the primary power about 120'-130' and relocate the existing transformer there. I can then set my meter can next to that and go the 250' to my house. All at the cost of about $1,500. I still disagree with having to do it this way, but it ended up costing much less than I had anticipated. I don't have to upsize my wire or conduit now, so I save some money there. In the end, I gave in because I just want to get to work while the weather is nice. But I know I was right. Thanks to everyone for the replies and suggestions.

 

[kwired]

Just an update on my situation for you guys...

I met with the POCO's manager and head lineman on Friday and we came to an agreement. They are going to remove the existing transformer and replace it with a junction box. From there, they are going to extend the primary power about 120'-130' and relocate the existing transformer there. I can then set my meter can next to that and go the 250' to my house. All at the cost of about $1,500. I still disagree with having to do it this way, but it ended up costing much less than I had anticipated. I don't have to upsize my wire or conduit now, so I save some money there. In the end, I gave in because I just want to get to work while the weather is nice. But I know I was right. Thanks to everyone for the replies and suggestions.

Sounds like you are lucky just to get them to compromise some. Many POCO get an idea and don't want to change it in that kind of situation.

 

[A-1Sparky]

Sounds like you are lucky just to get them to compromise some. Many POCO get an idea and don't want to change it in that kind of situation.

Yeah, I was expecting a much worse outcome.