C. Recommendations

This chapter addresses how to enable storage projects to mitigate system impacts within the review process through three sets of recommendations. First, the chapter recommends interconnection procedure language to require that the information provided to customers through the screening results data be sufficiently detailed to enable the customer to understand the constraints identified and, thereby, how a project may be modified to address the constraints. Second, the chapter provides examples of detailed screen and study results that utilities could use to relay useful data to the customer. Finally, the chapter recommends interconnection procedure language that would alter the Supplemental Review and study processes to allow the customer to act on the information provided by implementing DER design modifications.

1. Interconnection Procedures Should Be Revised to Provide More Data on Failed Screens

Several state interconnection rules provide some direction to the utility in terms of the content relayed to the customer when Fast Track screening results are delivered. Updated interconnection rules portray this directive in varying levels of detail.((Code MD Regs. (April 6, 2021) (“If the small generator facility is not approved under a Level 2 review, the utility shall provide the applicant written notification explaining its reasons for denying the interconnection request.”); New York Standardized Interconnection Requirements (March 2021) I.C Step 4 [“…the utility shall provide the technical reasons, data and analysis supporting the Preliminary Screening Analysis results in writing.”])) These general guidelines often can be interpreted quite loosely and give a lot of leeway to the utility in terms of how much information is provided. This results in different approaches from different utilities and varying levels of information provided to the customer. More recent proposals to update interconnection procedures aim to give more specific guidance so that a minimum level of information is provided.((IL Commerce Comm., Dkt. 20-0700, Amendment of 83 Ill. Adm. Code 466 and 83 Ill. Adm. Code 467, Second Notice Order (Aug. 12, 2021) 466.100.b.5.B (“If one or more screens are not passed, the EDC shall provide, in writing, the specific screens that the application failed, including the technical reason for failure. The EDC shall provide information and detail about the specific system threshold or limitation causing the application to fail the screen.”); MA Dept. of Pub. Util. Dkt. 19-55, Massachusetts Joint Stakeholders Consensus Revisions to the Standards for Interconnection of Distributed Generation Tariff (“DG Interconnection Tariff”) to Address the Interconnection of Energy Storage Systems (Feb. 26, 2020) 3.3(e) (“If one or more Screens are not passed, the Company shall provide, in writing, the specific Screen(s) that the Application failed, including the technical reason for failure. The Company shall provide information and detail about the specific system threshold or limitation causing the Application to fail the Screen.”).)) To ensure that the customer has enough information to make design decisions, the rule should give as specific guidance as possible on what results should convey. Accordingly, it is recommended that the description of data and analyses (e.g., SGIP 2.2 Initial Review) be revised to specify the level of detail that should be provided as follows:

Within 15 Business Days after the Transmission Distribution Provider notifies the Interconnection Customer it has received a complete Interconnection Request, the Transmission Distribution Provider shall perform an initial review using the screens set forth below, shall notify the Interconnection Customer of the results, and include with the notification copies of the analysis and data underlying the Transmission Distribution Provider’s determinations under the screens. If one or more screens are not passed, the Distribution Provider shall provide, in writing, the specific screens that the Interconnection Request failed, including the technical reason for failure. The Distribution Provider shall provide information and detail about the specific system threshold or limitation causing the Interconnection Request to fail the screen.

2. Screening Results Should Provide Relevant and Useful Data

Ideally, when Fast Track screen results are provided, full information about each screen would be given such that the customer would be able to ascertain exactly what changes to the DER system could allow it to pass the screen (and thereby avoid the need for upgrades). More helpful still may be to provide suggested design changes that would reduce interconnection hurdles. Utilities may believe, however, that the latter goes beyond their responsibility in the interconnection process and prefer to simply relay information.

The project team reviewed screening results from utilities in Hawaii, Illinois, Minnesota, and North Carolina to determine the range of data currently provided. The type and amount of data provided varied significantly, with some utilities providing a simple “pass” or “fail” for each screen and others providing more detailed data. Given the likelihood of data being available to the utility during the screening process, a list of preferable screen results data is presented in the recommendations. With the exception of some of the data in Supplemental Review screen, this type of data has been provided by one or more of the utilities reviewed. Utilities should provide data for each screen when providing Fast Track results to the customer, as noted in Table 5 below. Additionally, some ideal screen result examples are provided following the table. Since utilities vary in their application of the Supplemental Review screens for voltage, power quality, and safety and reliability, full guidance cannot be given, but similarly detailed data should be provided for all screens applied.

Table 5. Data Provisions for Individual SGIP Screens

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The below examples contain screen language inclusive of the recommendations of Chapter IV.

3. Impact Study Results Should Provide Analysis of Alternate Options

System impact studies are much broader in scope and require more detailed analysis compared to the screening process. Identifying the universe of data and information to be provided in study results is therefore challenging and interconnection rules typically describe such results in broad terms. For instance, SGIP attachment 7 (system impact study agreement) states:

A system impact study shall consist of a short circuit analysis, a stability analysis, a power flow analysis, voltage drop and flicker studies, protection and set point coordination studies, and grounding reviews, as necessary. A system impact study shall state the assumptions upon which it is based, state the results of the analyses, and provide the requirement or potential impediments to providing the requested interconnection service, including a preliminary indication of the cost and length of time that would be necessary to correct any problems identified in those analyses and implement the interconnection. A system impact study shall provide a list of facilities that are required as a result of the Interconnection Request and non-binding good faith estimates of cost responsibility and time to construct.

While the Impact Study is meant to analyze the impact of the DER system described in the application, developers may be interested in tailoring the DER to avoid or mitigate any distribution system constraints. Data about these constraints may be limited at the time of application, due either to lack of access to the type of information described in Chapter VI or effects from earlier-queued systems. In addition to the full study results which are normally provided, it would be useful to provide interconnection customers with an analysis of potential changes to the DER system which would eliminate or reduce the need for distribution system upgrades.

From the developer perspective, a transparent, collaborative process between the utility and developer that helps to refine the proposed DER design in a manner that maximizes the benefits to the customer while also benefitting, or at least minimizing the impact on, the distribution system would be ideal. A step in this direction, without completely revamping the interconnection process, would be to provide a limited analysis of alternative DER configurations. For efficiency, studying these alternative configurations would best be done during the normal timeframe of the study, rather than requiring restudy after the results are delivered. Some utilities regularly provide this type of analysis as part of the study results, though they vary in how that information is evaluated or presented. As discussed below in Chapter VII.C.6, this analysis can be guided by discussion between the utility and developer. As an example, a reduced Nameplate Rating or modified power factor (PF) setting may be noted as a less expensive solution to an identified upgrade. Below is an example table similar to that provided in one utility’s study results and includes mitigations that address identified impacts.

Table 6. Example Study Results with Alternate Options

4. Processes Should Allow for Design Modifications to Mitigate Impacts

Interconnection customers may have various reasons to modify their projects during the interconnection process or after a project is already constructed (e.g., certain equipment is no longer available in the marketplace forcing the customer to change the identified equipment, policy changes may necessitate design changes, or the project may want to mitigate impacts). Therefore, it is important to have well-documented sections in the interconnection rules that provide guidance on whether and how design changes can be accommodated.

Currently, many state interconnection procedures have one overarching section which addresses what type of modifications can be made and how they will be evaluated; this is typically known as the “Material Modification” process.((See, e.g., Minnesota Distributed Energy Resources Interconnection Procedures, Section 1.6 (provides a process for identifying whether a proposed modification constitutes a material modification and specifies that modifications that are deemed to be material will require withdrawal of the interconnection application and resubmittal); California Rule 21 table F.1 defines Type I modifications under the Fast-Track process, while section Ee defines Type II Modifications referring to existing facilities, and each provide descriptions of changes that require a new interconnection application and those that do not; MA Dept. of Pub. Util. Dkt. 19-55, Hearing Officer Memorandum Announcing the Department of Public Utilities‘ Interim Guidance — Energy Storage Systems II, ESS Decision Tree (Feb. 28, 2020) provides interim guidance on DC- and AC-coupled systems that seek to add ESS after the initial interconnection application (https://fileservice.eea.comacloud.net/FileService.Api/file/FileRoom/11862820).)) SGIP defines a material modification as any modification that may have “a material impact on the cost or timing of any Interconnection Request with a later queue priority date.” Some states include a specific list of the types of changes that are, or are not, considered material.((See e.g., New York Standardized Interconnection Requirements, p. 39 (March 2021) (definition of material modification includes examples).)) In general though, changes that would require a re-evaluation or restudy of a project, such as an increase in Export Capacity, extension of operating profile, or addition or removal of ESS, are typically deemed material and thus require submittal of a new interconnection application.

However, in order to enable DER system design to be altered to respond to screening or study results, it is necessary to create a separate process that enables certain changes that might otherwise be deemed material. These changes should be treated differently from modifications proposed at other points in the process, so long as they are proposed at a designated time following the screening or study process and are specifically tailored to mitigate identified impacts. Changes proposed at other times or for other reasons should be reviewed under existing material modifications provisions. The following sections recommend where these changes should be allowed during the screening and study processes.

5. Allowance for Design Changes After Supplemental Review

Having the information provided via screen results as described in section VII.C.2 above should give a developer an understanding of the grid constraints at that location if a screen is failed. However, according to SGIP and most interconnection procedures today, if a screen is failed and the utility cannot determine that the system can still be safely and reliably interconnected, the project must then proceed to Supplemental Review or full study. During the Supplemental Review process, additional screens are applied which may provide further detail on whether system upgrades are required and also provide an opportunity to identify if modifications might be made to address the identified constraints. Allowing for a short period of design change and review, as necessary, would help more projects move forward quickly with minimal effects on the queue. These changes could incorporate some material modifications yet still allow for review without withdrawal and resubmittal of the application.

The recommended language below allows projects to redesign the DER system within certain constraints during Supplemental Review. This would allow for changes such as a decrease in nameplate capacity or Export Capacity, or potentially changes to the operating schedule (where such can be evaluated during the Supplemental Review process). This approach is not included in Initial Review since the achievable timeline would not be significantly different compared to application withdrawal and resubmittal. Additionally, most states have conservative, non-detailed Initial Review screens. Thus, after application of the initial Fast Track screens, the customer will not yet have sufficient information about whether upgrades are indeed required, and correspondingly, what project modifications may be needed or possible.((In response to failing the 15% of peak load screen (SGIP as modified per the recommendations of Chapter V, a customer could elect to install a non-exporting system. In response to failing the shared secondary transformer screen (SGIP as modified per Chapter V, a customer could elect to reduce Export Capacity.)) Thus, where states do include more detailed screens in Initial Review (e.g., comparing the operating schedule to available capacity evaluated on a seasonal or monthly basis) then this approach could be applied effectively within Initial Review as well.

To amend the Supplemental Review process in response to screen failures (SGIP section 2.4.5), the following changes are recommended:

If the proposed interconnection passes the supplemental screens in sections,, and above, the Interconnection Request shall be approved and the Transmission Distribution Provider will provide the Interconnection Customer with an executable interconnection agreement within the timeframes established in sections and below. If the proposed interconnection fails any of the supplemental review screens the Distribution Provider shall specify which screens the application failed, including the technical reason for failure, and the data and the analysis supporting the supplemental review. The Distribution Provider shall provide information and detail about the specific system threshold or limitation causing the Interconnection Request to fail the screen. If the Interconnection Customer chooses to amend the Interconnection Request to address the specific failed screens, the Interconnection Customer must submit an updated Interconnection Request demonstrating the redesign within ten Business Days after receiving the screen results. The redesign shall only include changes to address the screen failures or identified upgrades (which could include, for example, the addition of DC-coupled or AC-coupled energy storage). Increases in Export Capacity or changes in Point of Interconnection are not permitted and shall require the Interconnection Request to be withdrawn and resubmitted. The Distribution Provider will evaluate whether the redesign addresses the screen failure and notify the Interconnection Customer of the results of this evaluation within ten Business Days. This redesign option to mitigate impacts shall only be available one time during the Supplemental Review process. If and the Interconnection Customer does not amend or withdraw its Interconnection Request, it shall continue to be evaluated under the section 3 Study Process consistent with section below.

Commissions may want to require that the customer pay a fixed fee for the additional review, or require that a deposit on the actual costs of the review be provided by the customer.

6. Allowance for Design Changes Within Full Study

a. Study Options

As mentioned in VII.C.3 above, it is helpful for alternate configurations to be evaluated during the Impact Study, such that a developer can choose to reduce interconnection costs with modifications to the initial DER design that have already been evaluated by the utility. Since the utility will have studied the alternate configurations already, this should allow the developer to avoid further study and move straight to an interconnection agreement as long as they agree to change the design in line with the options that were studied.

During the scoping meeting, the developer should indicate the types of DER system changes they would be open to considering. For utilities that can evaluate an operating schedule as discussed in Chapter IX, a reduction in Export Capacity for certain hours of the year could be considered. This would help a developer take advantage of an ESS’s customizable nature, designing around constraints that may exist for only a small portion of the year (for example, low loading).

It is recommended that the developer and utility agree during the scoping meeting to evaluate up to three different options, one being the original design (or as agreed to be modified during the scoping meeting). The other two options could contain a number of changes to system parameters such as, but not limited to:

  • Reduction in Nameplate Rating or Export Capacity
  • Modification to DER voltage regulation
  • Operating profile modification (e.g., a fixed discharge/export schedule or a reduction in Export Capacity for certain hours of the year)
  • Dynamic control (e.g., commanded curtailment)

The utility should indicate how each type of alternate DER design can be incorporated into the study. It is recommended that the analysis of alternate designs be memorialized in the System Impact Study agreement (e.g., SGIP Attachment 7), though flexibility to change alternate options through mutual agreement should be maintained as the study is underway.

While these types of analyses are not required by interconnection rules today, it may be beneficial for Commissions to explore if and how such practices could be harmonized and codified.

Design modification outside of those options already evaluated may require further study and can be accommodated by the process set forth below.

b. Post-Results Modifications

Due to high interconnection cost estimates, even within the options studied per the previous discussion, modifications to the DER system outside the alternate options may be desired. A process for modifications in the study process, similar to that proposed above for Fast Track projects, is desirable and will help ESS projects move forward with changes to system design or a modified operating profile. Most interconnection rules already include some measure for allowing changes deemed “non-material,” but it is recommended that an explicit process be defined for modifications after study results are delivered.((For example, Maine Chapter 324 section 12(D)(1) specifies this type of modification specific to the full study (Level 4) process.))

It is recommended that a new section be added to the interconnection rules, such as a new section 3.4.10 for SGIP, as follows.

3.4.10 A one-time modification of the Interconnection Request is allowed as a result of information from the system impact study report. If the Interconnection Customer chooses to amend the Interconnection Request to address the specific system impacts, the Interconnection Customer must submit an updated Interconnection Request demonstrating the redesign within fifteen Business Days after receiving the system impact study results from the Distribution Provider under section 3.5.1. The redesign shall only include changes designed to address the specific system impacts or identified upgrades (which could include, for example, the addition of DC-coupled or AC-coupled energy storage). This redesign option to mitigate impacts shall only be available one time during the Study Process. Increases in Export Capacity or changes in Point of Interconnection are not permitted and shall require the Interconnection Request to be withdrawn and resubmitted.

The Distribution Provider shall notify the Interconnecting Customer within ten Business Days of receipt of the modified Interconnection Request if any additional information is needed. If additional information is needed or document corrections are required, the Interconnection Customer shall provide the required information or corrections within ten Business Days from receipt of the Distribution Provider notice.

The actual costs to Distribution Provider for any necessary restudies as a result of a modification described above shall be paid by the Interconnection Customer. Such restudies should be limited to the impacts of the modification and shall be billed to the Interconnection Customer at cost and not for work previously completed. The Distribution Provider shall use reasonable efforts to limit the scope of such restudies to what is necessary. The revised impact study shall be completed within fifteen business days.


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