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Question

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Are interconnection limitations an issue only in the Northeast, or have other US regions also had utility interconnection limitations?

I was reading this article about Massachusetts cluster study by National Grid. It said a lot of projects had to be halted due to the interconnection limitations of the grid. Is this an issue in all states, or just specific to Massachusetts?

 

Answers

This cluster study is not unique to MA or Northeast. Since we are talking about distributed generation interconnection, each utility has some variation of hosting capacity analysis or some other distribution system studies that indicate where they have capacity on the system to interconnect.

 

Evan Dent's picture
Evan Dent on Oct 20, 2020

Thanks for the response!

Same issue anywhere as Distributed Solar is connected behind Distribution Transformers.  Which are sized to give firm capacity for Peak Demand. 

For 'reverse' operation with MW scale Generation the basic method works with the Trough demand plus the Transformer rating as the firm Generation capacity.  Then however you can allow connections which are configured for 'Active Network management' (expression used by UK Distribution Network Operators) to ensure the Generation can be pulled back to ensure security of supply is not compromised in real time.

Thus I was looking at a GB South West 132/33kV substation with 137MW firm Transformer capacity and a Peak demand of 147MW!!!  Min demand @80MW.  But with 120MW of embedded Generation and another 130MW of Applications approved.  Thus the whole lot is under if Active Network Management.

And there are also of course restrictions on the main Supergrid if you suddenly get applications for large amounts of Generation which can be built quickly!!

I was looking at Bridgewater - Western Power Distribution.

https://www.westernpower.co.uk/our-network/active-network-management-anm

 

And as regards the Distribution and Transmission interface.

https://www.westernpower.co.uk/transmission-active-network-management-tanm-and-appendix-g

https://www.tneigroup.com/news/active-network-management-good-practice-guide

https://www.energynetworks.org/industry-hub/resource-library/open-networks-2019-ws1a-p5-anm-flex-stackability.pdf

Several Utilities in the US and other countries are upgrading existing transmission and subtransmission lines using high-capacity, low-sag ACCC Conductor. While many projects sit in the queue waiting for funding, the ACCC Conductor actually serves to reduce line losses by 25 to 40% or more which qualifies it for Green Bond financing - often only considered for generation investments. If the engineering teams and planners reach out to the sustainability folks and financiers, they may see their projects move forward in the queue. 

The interconnection processes in all regions are having similar challenges due to many different factors.  Some of these factors are caused by lack of information, over "booking" of the queue, roller rights, and limited load data and outdated forecasting methodologies.  Also, the models used to perform these analyses were not designed to handle the volume and type of resources being connected to the grid.  Also, regulatory policies vary across Federal and State jurisdictions which complicate the process.  In addition, PURPA policies for resources choices are not consistent across the grid as to who has "first call" interconnection rights.

The lack of universal standards for the control and operations of these non-utility resources that are grid connected are causing delays as well.  Also, physical and cybersecurity has become and important issue at the Federal level.  The uncertainty as to what is required and who pays for these requirements is up for debate and discussion and can be contradictory from jurisdiction to jurisdiction. 

The ultimate goal needs to be focused on grid reliability, security and resiliency at an acceptable cost and integrated with other goals such as renewable resources, storage and DSM programs. The challenge is determining the proper economic and technical evaluation methodologies that result in the lowest optimum cost versus savings.  When artificial "credits or added on" are forced into these analyses, the resulting grid and its operations will not be the optimal or best solution for all parties.  When these non-optimum solutions are selected, then someone has to pay for these higher costs.  Typically, when the utilities are required to build and operate these non-optimum solutions, these higher costs are included in the cost-to-serve calculations and may result in higher rates and costs to all customers or to a subset of customer classes.

CAISO area the constraint has been (mainly) CPUC. There are IROL/SOL limits on existing paths, but, those are currently being addressed. It seems as though transmission, at least here, is ramping up. Curious if there are other criteria, CCTG vs. RENEWABLE? NYISO, PJM seems to be pretty favorable for renewable generation, right?

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