Does 691 Apply

[kingpb]

Does 691 apply to microgrid applications were the PV is 5MW or more, but intended for facility consumption first, and selling second?
Would this also apply if say you 7MW total, 2MW PV being consumed, but exporting 5MW or more?

 

[jaggedben]

Yes.

The NEC does not care whatsoever about the buying and selling of energy.

 

[pv_n00b]

The NEC does care in 691 about what loads the PV system powers.

691.4(4) The electrical loads within the PV electric supply station shall only be used to power auxiliary equipment for the generation of the PV power.

NEC 691 would not apply in the OP's situation because of this. It is targeted at generation stations that are intended to generate energy to sell to the grid.

 

[jaggedben]

The NEC does care in 691 about what loads the PV system powers.

NEC 691 would not apply in the OP's situation because of this. It is targeted at generation stations that are intended to generate energy to sell to the grid.

Yes but the actual definitions in 691 are vague enough that, with respect to the OPs description, it just depends.

For example I would argue that a ground mount 5MW generating array that is separated from the rest of the facility could be an 'electric supply station'. Whereas a roof mounted array on a building with loads is arguably not. (How would you comply with 691.4(2) when the roof needs repairs, or if there's any non-PV equipment up there?)

The physical arrangement matters to 691. The economic arrangement does not. That is, not among distinct parts of a facilit(ies) where none are exclusively controlled by a utility.

 

[ggunn]

Yes but the actual definitions in 691 are vague enough that, with respect to the OPs description, it just depends.

For example I would argue that a ground mount 5MW generating array that is separated from the rest of the facility could be an 'electric supply station'. Whereas a roof mounted array on a building with loads is arguably not. (How would you comply with 691.4(2) when the roof needs repairs, or if there's any non-PV equipment up there?)

The physical arrangement matters to 691. The economic arrangement does not. That is, not among distinct parts of a facilit(ies) where none are exclusively controlled by a utility.

I would think that a 5MW PV system would be connected at medium voltage outside any customer's meter; in that case the point would be moot.

 

[kingpb]

Physical Arrangement:

A combination of ground mount, roof top, and canopy, connected through multiple 480V switchboards; aggregating up to plant MV distribution system, with BESS, total is just over 5MW PV. The facility load is at most half the connected PV, so expectation is to export approx. 2.5MW depending on weather conditions.
The way I was reading it was anything 5MW or more automatically fell into 691, which creates issues for large behind the meter microgrids.

It sounds like it's only 691, IF 5MW or more AND the intent is to only generate. Then it has to meet requirements of 691, otherwise it is only 690 requirements.

 

[wwhitney]

A combination of ground mount, roof top, and canopy, connected through multiple 480V switchboards; aggregating up to plant MV distribution system, with BESS, total is just over 5MW PV.

So does the system topology contain a single dividing point, where on one side there is over 5MW of PV inverters and no loads; and on the other side there all the premises loads?

If so, it seems hard to me to argue that the scope in 690.1 and the definitions in 690.2 don't mean that the whole system is subject to 691. In which case your roof top PV arrays would be prohibited by 690.4(5).

However, the Informational Note in 690.1 suggests this is not the intention, as you are not operating the system "for the sole purpose of providing electric supply to a system operated by a regulated utility for the transfer of electric energy." But Informational Notes are not enforceable, so if they conflict with the actually wording of the section, the actual wording controls.

If you don't have such a single dividing point, then I think you could argue you have multiple Electric Supply Stations, none of which are "large scale," and hence none of which are subject to Article 691.

Cheers, Wayne

 

[jaggedben]

I really don't think it was the intent of the CMP to prohibit more than 5MW aggregate generation among multiple installations on a property without fencing it all off. To the extent they put that in an informational note rather than the binding requirements, I think they screwed up.

Physical Arrangement:

A combination of ground mount, roof top, and canopy, connected through multiple 480V switchboards; aggregating up to plant MV distribution system, with BESS, total is just over 5MW PV.

I'd call that multiple separate systems under 5MW that neither meet the requirements of 691 nor are subject to it.

(That said, I'm a little surprised you can meet all of the 705 requirements between your various systems and the service point.)

It sounds like it's only 691, IF 5MW or more AND the intent is to only generate. Then it has to meet requirements of 691, otherwise it is only 690 requirements.

Reading the whole article again, I think that's correct. 691 assumes a direct connection to the utility. In my opinion they should have made allowances for large facilities (university campuses, airports) to follow 691 for systems that feed load in separate locations.

I always regarded 691 as optional; as in, if you fence it off (and etc.) then your engineer can slide on the letter of 690 if following industry practice for utility scale installations. Otherwise, you're subject to 690. Reading the Scope again, they didn't make this crystal clear. Par for the course in the NEC, I guess.

 

[pv_n00b]

The way I was reading it was anything 5MW or more automatically fell into 691, which creates issues for large behind the meter microgrids.

Yeah, there is a whole list of items the PV generator has to comply with in addition to the 5MW requirement. It's written more clearly in the 2023 NEC, (6) was added and (7) was just moved from the opening scope to the list. The complete list is:

(1) Electrical circuits and equipment shall be maintained and operated only by qualified persons.

(2) Access to PV electric supply stations shall be restricted in accordance with 110.31. Field-applied hazard markings shall be applied in accordance with 110.21(B).

(3) The connection between the PV electric supply station and the system operated by a utility for the transfer of electrical energy shall be through medium- or high-voltage switch gear, substation, switch yard, or similar methods whose sole purpose shall be to interconnect the two systems.

(4) The electrical loads within the PV electric supply station shall only be used to power auxiliary equipment for the generation of the PV power.

(5) Large-scale PV electric supply stations shall not be instal⁠led on buildings.

(6) The station shall be monitored from a central command center.

(7) The station shall have an inverter generating capacity of at least 5000 kW.

Several of these would make a microgrid installation with local consumption improbable.

 

[jaggedben]

The changes in 2023 make what I said here more valid:

I always regarded 691 as optional; as in, if you fence it off (and etc.) then your engineer can slide on the letter of 690 if following industry practice for utility scale installations. Otherwise, you're subject to 690. Reading the Scope again, they didn't make this crystal clear. Par for the course in the NEC, I guess.

Comply with the list pv_noob posted and you get to call it the thing and take advantage of the rest of the article.

...


Several of these would make a microgrid installation with local consumption improbable.

Actually (3) is the kicker. That makes it impossible to use 691 while feeding the MV network of even a very large facility (think airport or university campus) where you still might meet the rest of the list. So I have to essentially take back my post #2; in this case the NEC does care exactly where the energy goes.

 

[pv_n00b]

I always regarded 691 as optional; as in, if you fence it off (and etc.) then your engineer can slide on the letter of 690 if following industry practice for utility scale installations. Otherwise, you're subject to 690. Reading the Scope again, they didn't make this crystal clear. Par for the course in the NEC, I guess.

I miss the old days too. If the fence was too high for the AHJ to climb over you could do anything you wanted to do inside. Quick close the gate, I see an AHJ car coming down the road.