[RE-wrenches] 2 PV utility interconnect disconnects?

[Joel Davidson]

Hello Kurt,

Thanks for looking at this problem.

The project manager works for a licensed PV contracting company that has been trying for several months to get this PV system approved. First, they were blocked by the Los Angeles Building & Planning's interpretation of the LA Fire Marshall's set-back guidelines (not regulations). Now LADWP's interconnection department is holding up the project. If the system had been installed last year as planned, this new rule would not have applied. There is no requirement like this in nearby Southern California Edison (SCE) territory.

(Pulling the meter is not acceptable to most fire departments, but that's a separate subject.)

My question is Do any other electric utilities require an additional disconnect switch on a PV system with a line-side tap?

Joel Davidson 

  ----- Original Message ----- 
  From: Kurt Albershardt 
  To: RE-wrenches 
  Sent: Saturday, February 21, 2009 12:08 PM
  Subject: Re: [RE-wrenches] 2 PV utility interconnect disconnects?


  On 2/21/09 10:24 AM, Joel Davidson wrote: 
    January 1, 2009 LADWP added another interconnection requirement. See page 8-11 at http://www.ladwp.com/ladwp/cms/ladwp004344.pdf


  I found what I think is the relevant section on p. 36 of the PDF (called out as p. 1-32 at the top of the page.)



    This is how a PV commercial project manager described this new requirement:

  I'm curious if this was an LADWP project manager, or someone managing projects for customers?



    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.

  They define

  generators using a closed-transition (“make-before-break”) type transfer switch or a multi- 
  breaker transfer scheme, or an electrical inverter that can be configured to operate in a utility 
  interactive mode constitute a potential back feed source into the Department’s electric system and are 
  classified as interactive generators.



    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.

  The wording appears to be:

   All interconnected generating systems shall be connected on the load side of the customer’s meter switch (main service disconnect device). 

  I'm wondering about the origins of this requirement.  How would they handle critical power systems (data centers, hospitals, etc. which are often fed by multiple services entering by different routes?)  How would they handle a premises with multiple service voltages?




    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. 

  The phrase "pull the meter" comes to mind here...




    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.


  Has this "project manager" ever heard of anti-islanding?  This fantasy scenario almost makes sense for a battery-backed PV system, but then the presence or absence of sunshine would not matter.  What about emergency backup gensets and UPS or flywheel systems?  They are protected from backfeeding by a transfer switch, so exempted, but UL 1741 does not qualify as such?











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