IPWG: Proposed Technical Screening Criteria (20220411)

Transmission Owner Sector Feedback on Proposed Technical Screening Criteria presented at the April 11, 2022 Meeting of the Interconnection Process Working Group

May 2, 2022

The MISO Transmission Owners (Owners or TOs) appreciate the opportunity to comment on Proposed Technical Screening Criteria for Distributed Energy Resources and Distributed Energy Resource Aggregations presented by MISO at the April 11, 2022 Meeting of the Interconnection Process Working Group (IPWG), and provide the feedback below for MISO’s consideration.

Do the proposed screens accurately capture potential transmission system reliability impacts?

Owners are concerned with MISO’s proposal to use summer peak load for screening rather than off-peak load for both the TO and MISO screens.  Owners would prefer that the evaluation of impact of an interconnecting DER or collection of interconnected DERs be determined at shoulder peak or at both shoulder and peak. 

Are there gaps in the coverage of the proposed technical screens (i.e., false negative outcome)?

• If only one model is to be used, MISO should use a summer off-peak case instead of a summer peak case because impact to the transmission system is most likely to happen during that time when load levels are low.   Additionally, the Owners are concerned that if MISO is focusing on the peak scenario, issues may be masked.  To ensure that issues are not masked, and the worst-case scenario is evaluated, a daytime minimum load should be evaluated at for the purposes of screening as the daytime minimum load would likely be the worst case scenario.
• The Owners are also concerned that the 5MW injection requirement can lead to gaps and feel that the determination of whether a MISO study is needed should be based on TO studies.
• Discussion is needed regarding  how MISO will handle transmission upgrades that are below the 5 MW threshold, such as relay changes or a simple transmission jumper additions/replacements; it is the Owners understanding that these would need a MISO FCA to be upgraded.

Are there alternative screening criteria that should be evaluated?

if impact is identified by the Owner, MISO should perform a study.  TOs need flexibility in identifying the potential need for upgrades due to the impact of a DER interconnections. 

• Many distribution substations have load levels that would result in backfeed with an injection from a DER of less than 5MW, and any backfeed will require coordination of protection. Even if backfeed does not occur, if the DER aggregation is at least 50% of the substation load, coordination of protection is required. 
• While the Owners understand the intent of the screening criteria, there is a need to ensure that the screening criteria is not set too high to trigger additional studies and potentially miss reliability issues with DER interconnections.

MISO’s proposed 1% line loading change screen

A 1% line-loading change screen is reasonable as a starting threshold, but only up to a 1MW impact.  For example, DER could impact the transmission system up to 1 MW (1 MVA) without MISO involvement, but If DER exceeded the 1 MW threshold, then the 1% rule would apply. 

• Owners would like to understand how this proposed screening criteria would impact the 5MW fast track study, specifically, would the1% impact be requested to be added to the 5MW Fast Track process?  Owners support consistency and clarity on when a study would be required.

• Do the proposed screens accurately capture potential transmission system reliability impacts?
• Are there gaps in the coverage of the proposed technical screens (i.e., false negative outcome)?
• Power injection will occur before peak load is exceeded.
• Xcel Energy is currently seeing Power Injection during the daytime hours when load is not at peak.
• Adding the Line Loading Change is appropriate as an additional criteria for impact.
• Are there alternative screening criteria that should be evaluated?
• Given what we have already experience with DER, Xcel Energy recommends the MW screen be reduced from 5MW to 0MW and retain the 1% line flow change screen.

• Do the screens allow for passing through projects without potential transmission system reliability impacts?
• Assuming the question is could the screening pick up a project for study that does not have a reliability impact?
• That is possible but the alternative would be a greater risk where the screening does not pick up a reliability impact and issues occur in real-time operations.
• Are the screens practical to implement?
• Yes, a MW power injection screen would be practical to implement from the utility side.

ITC Holdings thanks MISO for the opportunity to comment on the Proposed Technical Screening Criteria for DER Interconnection Requests discussed at the IPWG.

ITC has the following comments regarding the 5 MW Power Injection Criteria MISO has proposed.  While typically this criterion of 5 MW at peak will suffice to identify areas of concern for power injection into the transmission system there are a couple of conditions that could cause concerns with this criterion.

1. ITC is concerned with MISO’s proposal to use summer peak load for screening rather than shoulder-peak load for both the TO and MISO screens.  Owners prefer that the evaluation of impact of an interconnecting DER or collection of interconnected DERs be determined at shoulder peak or at both shoulder and peak.
2. ITC is concerned that the 5MW injection requirement can lead to gaps, and fells that the determination of whether a MISO study is needed should be based on TO studies, and if impact is identified by the Owner, MISO needs to do a study.  TOs need flexibility in identifying the potential need for upgrades due to the impact of a DER interconnections.  Many of distribution substation have load levels that would result in backfeed with an injection from a DER of less than 5MW, and any backfeed will require coordination of protection. Even if backfeed does not occur, if the DER aggregation is at least 50% of the substation load, coordination of protection is required.  Additionally,
   1. if the overall capability of the transformer power is being injected to the transmission system has a capacity of less that 5 MW.  For this case, using a criteria greater than the capability of the transformer, before you exceed threshold one and still looking to exceed a second threshold does not seem to make sense.
   2. If the power injected into the transmission system at an shoulder peak time would again exceed the capability of the transformer yet not exceed either of the two identified MISO thresholds seems to be cause for concern.
3. ITC would like to understand how this proposed screening criteria would impact the 5MW fast track study, specifically, would the1% impact be requested to be added to the 5MW Fast Track process?  ITC supports consistency and clarity on when a study would be required.
4. MISO’s 1% line loading change screen is reasonable.

The proposed screens, >= 5 MW injected onto the transmission system at peak AND >= 1% of Summer rating change in line flow, which are based on and similar to standard Affected System impact criteria, provide a useful starting point for discussion.  In response to MISO’s specific questions, these appear practical to implement and have no specific problems obvious to us beyond what we note below. 

We do have some concerns.  In particular, it’s not clear to us that peak-demand models provide the appropriate basis for evaluating DER impacts.  A 5 MW injection during peak conditions may correspond to a much larger injection during other conditions that prevail during many hours of the year.  If such injections were to occur at multiple points within a given area, very significant impacts could result, and MISO’s proposal does not appear to provide assurance that such impacts could be managed.

Finally, we note our understanding that the Affected System are applied by MISO as OR criteria—that is satisfaction of any one element would trigger the screen—while MISO proposes to apply the two criteria in question on an AND basis—so that both would have to be satisfied to trigger the screen.  To the extent that MISO proposes these criteria in order to achieve some consistency with Affected System study criteria, this change to AND logic represents a departure.

SunEnergy1 supports the criteria proposed by MISO. It is consistent with screening criteria used on other affected systems. It also strikes a balance between ensuring system reliability and reasonable study efforts. Two things to clarify in future languages 1) Clarify that criteria are to be applied to the aggregate impact of DERs to be studied, not individual DERs. 2) Need future design when the distribution line is not radially connect to a single transmission substation -- the distribution lines are networked.

Thank you the opportunity of providing feedback.

Kun