Wrenches,
January 1, 2009 LADWP added another interconnection requirement. See page
8-11 at http://www.ladwp.com/ladwp/cms/ladwp004344.pdf
This is how a PV commercial project manager 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 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.
My question: Do any other electric utilities require an additional
disconnect switch on a PV system with a line-side tap?
Joel Davidson
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