Distributed generation interconnection

[jacksonlord]

This is a very basic question, but when distributed energy generation like solar interconnects to the distribution system, do they have to tie in directly to a substation? If so, how can medium-size generation be built on the distribution lines themselves without having to make large upgrades?

 

[davidbeach]

No need for a substation connection. Generally connected on the customer side of the meter.

 

[jacksonlord]

Thanks. But what about distributed gen with a little more size that's selling wholesale power directly to the utility? Like 1 or 2 MW?

 

[davidbeach]

Doesn't generally start to become an issue until the 10MW range. But it also depend on the interconnection requirements of the serving utility.

 

[jacksonlord]

Thanks again. Can I ask you some more questions?:

I'm reading some information on a distribution circuit connected to a substation. It has numbers like Circuit Capacity (say, 9 MW) and Circuit Peak Load (say, 7 MW). Then it refers to the substation "bank" which has different numbers for Sub Bank Capacity (34 MW) and Sub Bank Peak Load (33 MW).

How do the circuit numbers relate to the sub numbers when the utility is looking at new distributed generation on that circuit?

 

[davidbeach]

There's more than one feeder on that transformer. Beyond that you really need to be talking to the utility, there are no one size fits all answers.

 

[jacksonlord]

ok thanks

 

[MAS2000]

I can add that if the utility circuit is rated 9 MVA or more and provided that all other criteria for connection of distributed generation is met (voltage profile, power quality, etc); then your Dist Gen can be accepted, no matter what the load is on that circuit.

The only concern could be the island mode operation of your Dist Gen when the utility feed is lost.

M.A.Sh.
Elect. Engr.

 

[odlanor]

I guess that distributed energy generation like solar interconnects to the distribution system directly to a substation. Distribution Utility have contract with Customers.
Solar energy does do not have a power quality energy.
Any disturb , interconnection protection remove distributed generation from the system.
Utility does not permit island system to distributed generation.
That`s an interpretation of my country.

 

[MAS2000]

I agree with odlanor that in majority of cases the intertie protection will disconnect the dist generation and will not permit island operation, but I know instances where island operation is permitted after detailed studies have indicated that power quality can be maintained during island operation. Here by power quality I mean voltage maintained within statutory limits; frequency maintained; and sufficient fault level available to ensure that system faults are isolated by correct operation of protection. The solar dist gen has disadvantage of having very lower fault levels and thereby it is advisable to allow island operation.
I don't agree that solar dist gen only interconnects to the substation. In UK solar farms and smaller scale solar dist gen can be interconnected on the utility owned feeder lines.

M.A.Sh.
Elect. Engr.

 

[musaUKPN]

Correction above: .......not advisable to connect solar dist gen... because of low fault levels.........

musa UKPN