[RE-wrenches] 2 PV utility interconnect disconnects?

[Richard L Ratico]

Hi Joel,

Here's a link to utility requirements in VT as of 1/8/08. 
See drawings #405 & #406 at the end of the document. 
Looks like a PITA for existing structures where a backfed breaker won't work.

http://www.cvps.com/CustomerService/Book01-08.pdf

Dick

Dick Ratico
Solarwind Electric
Bradford, VT 05033
VT #EM-4156
NH #10483 M 


--- You wrote:
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
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