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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