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? _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
