[RE-wrenches] 2 PV utility interconnect disconnects?

[Joel Davidson]

Hello Matt,

Thank you very much for your detailed reply. In case you missed my first 
post on this issue, here it is again with the details.

January 1, 2009 LADWP added another interconnection requirement. See page 
8-11 at http://www.ladwp.com/ladwp/cms/ladwp004344.pdf

Here is how a PV contractor project manager working on a commercial project 
in LADWP territory described this new requirement:

When a customer, any customer, generates electrical power with the intention 
of supplying that power to the electrical grid, the connection to the grid 
has to be made below, or on the load-side, of one main switch for the 
property. In other words, the policy seems to be that the total electricity 
supplied to any building or property must be disconnected from the grid by 
one main switch.

This policy is in place for emergency situations, to where fire fighters or 
persons on the scene during an emergency would be able to completely shut 
down building power with one switch. This describes a scenario whereby the 
grid is disconnected from the building circuits, but the solar PV is still 
connected to the building circuits. Therefore, there is a basic flaw in this 
requirement; this scenario is only possible at nighttime- during the 
daytime, the solar PV system is energized and may still feed to the building 
electrical circuits, unless the main PV disconnect switch is opened. 
Therefore, during emergency situations in the daytime, a minimum of TWO 
switches are needed to completely disconnect power from the grid AND from 
the building circuits. This effectively negates LADWP's one-switch policy.

Referencing (an LADWP letter dated 23 January to the project manager) "the 
generator supply circuit shall be tapped on the load side of the customer's 
main service disconnect device". This may be accomplished by either 
connecting the solar PV circuit, 1. Via a circuit breaker inside the 
existing customer service panel (circuit breaker panel), which is a 
load-side tap, or 2. By tapping into the incoming electrical service above 
the service panel, which is a line-side tap. This is the result of both 
options:
1. In most cases, this will result in the service panel being replaced, and 
upgraded to a larger capacity. All existing circuits in the building will 
need to be re-fit with new circuit breakers, in addition to the solar PV 
circuit breaker. This can cost upwards of $10,000 on average, of additional 
expense per property.
2. Above the solar PV line tap, a new main circuit breaker must be 
installed, complete with an enclosure. This will then disconnect the LADWP 
incoming electrical service from the building service panel and the solar PV 
circuit. This will add from $3,000 to $6,000 to the project budget.

My comment: This situation is hard to describe in words, but picture a 
utility revenue meter feeding power into a customer service panel. The 
service panel cannot accommodate a PV system backfeed meter so the project 
manager submitted the interconnection 1-line drawing with the PV system 
feeding into the required
solar performance meter and then into the required lockable fused disconnect 
switch and then into a line-side tape between the revenue meter and the 
service panel bus. Now picture this new requirement's additional disconnect 
switch and circuit breaker between the line-side tape and the revenue meter. 
Do any other electric utilities require an additional disconnect switch on a 
PV system with a line-side tap?

Joel Davidson

----- Original Message ----- 
From: "Matt Lafferty" <gilligan06 at gmail.com>
To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
Sent: Wednesday, February 25, 2009 11:57 AM
Subject: Re: [RE-wrenches] 2 PV utility interconnect disconnects?


> Joel,
>
> You are describing an NEC compliant configuration. Independent of the
> "utility". Determining whether or not the interpretation/requirement is
> excessive will require some additional information and will vary by 
> project.
>
> For instance: Per the NEC, a Supply Side connection (what we lovingly 
> refer
> to as "line-side") has several inherent requirements, besides the actual
> physical connection method. These requirements will determine what the
> appropriate configuration would be.
>
> The short list includes:
>
> * Location of connection point (For net-metered installs: Between the
> Revenue Meter and the Customer Service disconnect)
> * Length of tap conductors. (< 10' in most cases)
> * Location of first disconnect device. (Accessible, grouped, etc.)
> * Location and setting of first overcurrent protection device. (May or may
> not be integral to the disconnect device)
>
> It is critical to understand that a service disconnect does not 
> necessarily
> include overcurrent protection. See below for some examples. A lot of guys
> use unfused safety switches for their load-side connections. A load-side
> connection (breaker) has overcurrent protection ahead of the "disconnect".
> Remember that, what we call the "disconnect" is/was a utility requirement.
>>From an NEC perspective, the breaker serves as a disconnect and 
>>overcurrent
> protection device.
>
> Many guys miss a fundamental difference between the load-side and
> supply-side cases... The location of the overcurrent protection device
> relative the service disconnect. If you use a fused 
> safety-switch/disconnect
> within the appropriate proximity, then you have the "code" side covered.
>
> Once you have covered the NEC aspects, then you get down to the generator
> requirements of the ESP utility. They may have collective bargaining
> agreements or other requirements that say "visible, lockable, accessible 
> to
> utility, not accessible to customer". The last clause is a sticky one.
> Basically, it has been interpreted as: Customer is prohibited from 
> operating
> the switch or replacing fuses. If you go back through the older
> interconnection agreements, this is, in fact, the case. The "utility"
> disconnect is to be operated and accessed by utility personnel ONLY!. Read
> 'em. It's in there. The way utilities have interpreted and "enforced" or
> "not enforced" the letter of the interconnection agreement (it's really a
> contract) has varied. Often by local service center. One place requires 
> that
> a utility lock be installed on the disconnect with the handle "up" so the
> customer cannot operate it. The next town over, in the same utility, they
> don't bother. That kind of stuff. Besides the innocent differences, they
> could also just have hard-headed pricks in the engineering department of
> their distribution services division. Modern inverters are NOT the same
> thing as a spinning turbine, but some of the legacy perspectives are that 
> a
> "generator is a generator" and that "a single standard is easier to
> maintain". Think about this: If you are an old-time utility engineer, why 
> in
> the world would you want to draft up and implement a separate standard for
> inverter-based generation when you only have 10 years to go until
> retirement? If you can spend your energy for the next 10 years having
> another meeting and protesting and procrastinating and walking from one 
> side
> of the campus to the other and doing safety inspections on office chairs,
> why not? Oh, yeah. I know those guys. They wrap themselves in the almighty
> "safety and reliability" flag. Their seniority in the organization gives
> them influence that, frankly, might not be justified. Nevertheless, it is 
> a
> fact. In some cases, retirement is the only solution. Some AHJs go in this
> cupboard, too.
>
> Back to some real-world examples that should help drive the principle 
> home.
> The "misunderstanding" some installers have.
>
> In my travels, I have found a few, probably less than 10, that didn't have
> OCP at all. I've also found a location that has a couple of relatively 
> large
> systems, with multiple inverters on each, that didn't have OCP until the
> inverter branch circuit breakers in the IDPs (Inverter Distribution
> Panel)located on the roof! The latter is on a multi-story, modern office
> building, and has 2 separate interconnections set up the same way. One of
> the systems is rated at ~75A max and the other is ~125A max. 3-Phase. To 
> be
> clear, we are talking about 2 independent generation circuits that are
> (still) connected to the supply-side of 800A & 1200A services without OCP.
> To be clear, the shortest of the two circuits is ~130' one-way. To be 
> clear,
> this was installed by an electrical contractor.
>
> To be clear, all of these examples were signed off by the local AHJ and by
> the ESP utility. That doesn't make it right! Some of them have been
> corrected now and some haven't.
>
> The tragic thing is that, from a purely utility lineperson's perspective,
> the unfused disconnect is just fine! He or she can slap the handle, 
> isolate
> the generator, slap a lock on the handle, and go sit in the truck to wait
> for the line-crew to say "all clear".
>
> The NEC and the NESC and the collective bargaining agreements aren't, 
> shall
> we say, harmoniously aligned.
>
> So, to answer your question Joel, the specifics of an individual project
> must be considered in order to determine whether or not the requirements 
> are
> excessive.
>
> A long time ago, in a life far away, I dealt with the standardization 
> issues
> at SMUD. I was able to get the meter shop to accept a set of standards 
> about
> meter and disconnect locations based on the application. Doing the heavy
> lifting of writing it up and doing all the drawings basically took the
> "power to say no" away from distribution services and meter shop. Back 
> then,
> there was an all out war over whether or not PV was gonna survive.
> Distribution services was doing everything they could to squash it, and 
> the
> meter shop basically just had heartburn over not having a clear standard 
> and
> procedure they could expect to be followed for solar installations. (Lots 
> of
> "pre-Matt" history in all that...) I did a 1-hour presentation to the 
> Meter
> Shop, including field meter techs. I also did a 1/2 day training with my
> contractors and SMUD's Solar Specialists... Everybody got a copy in a 
> binder
> to put in their trucks. They were very grateful and the standard became a
> good quality control measure. Whenever one of the SMUD Solar Specialists 
> or
> Contractors weren't following the approved standards, I didn't have to be
> the babysitter any more. Everybody had the same set of rules. If the
> interconnection piece wasn't right, the Meter Shop didn't hook it up and 
> the
> contractor didn't get paid. No more, "I followed the plans and they were
> wrong". No more, "don't tell Matt we're gonna do it this way". Everybody 
> had
> to buck up.
>
> No more trying to install solar on houses and outbuildings that didn't 
> have
> suitable electrical service provisions. The customer had to upgrade BEFORE
> the solar crews came! (Quality Control step 1)
>
> The plans had to be right or the contractor didn't install it. (Quality
> Control step 2)
>
> The Meter Shop didn't change out the revenue meter or set the generation
> meter if any part of the job wasn't up to snuff. (Quality Control step 3)
>
> Added Benefit: Distribution services had to shut up. The Meter Shop became 
> a
> positive ally instead of not having a lot of good things to say.
>
> It was SMUD specific, related to the packaged PV systems we were 
> installing
> at the time. (SMA SWR-2500's with 20 ea. KC-120's). Even though the 
> standard
> was limited to residential systems having 2 or less Sunny Boy 2500's, it
> takes 18 drawings and individual descriptions to cover. When I wrote it, I
> kept an eye toward making it in a template format so it could be useful
> elsewhere in the future. For instance, a generic inverter could be
> represented and the amperage of the breakers & disconnects and fuses
> wouldn't need to be called out.
>
> I uploaded a PDF of this to the Wrench FTP server and asked Michael to 
> move
> it to the public side. Let me know off list if you don't see it here:
> ftp://ftp.re-wrenches.org/pub/
>
>I still have all the original dwg's and wmf's and word document... If you
> have a good reason for wanting any of that, let me know. I won't release
> them in that format without taking my name and SMUD logos off them for
> <hopefully> obvious reasons. Nothing personal, mind ya. After a 
> soft-scrub,
> I'd be happy to pass it along for good purposes.
>
> Happy standardizing!
>
> Matt Lafferty
>
>
> -----Original Message-----
>
> PV installers in the LADWP area are being told to put a disconnect switch
> and circuit breaker between the revenue meter and the customer's service
> panel if we use a line-side tap. Do any other electric utilities require 
> PV
> system disconnect switch and a 2nd additional disconnect switch on a PV
> system with a line-side tap?
>
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