Chapter 4.1: Reliability Assessment and Compliance
System reliability is the primary purpose of all MTEP planning cycles. To fulfill this purpose, MISO planners study reliability from multiple perspectives to confirm the transmission system has sufficient capacity to provide reliable service to customers.
Continued reliability of the transmission system is measured by compliance with regional and local Transmission Owner (TO) planning criteria. These standards define minimum requirements for long-term system planning and require explicit solutions for violations that occur in a two-, five- and 10-year timeframe. As planning coordinator, MISO is required to identify a solution for each identified violation that could otherwise lead to overloads, loss of synchronism, voltage collapse, equipment failures or blackouts.
The results of these reliability analyses, along with the proposed mitigating transmission projects, were presented and peer-reviewed at a series of Subregional Planning Meetings (SPM) that were held in December 2014, May 2015 and August 2015. Each project included in MTEP Appendix A is the preferred solution to a transmission need when its implementation timeline requires near-term progress towards regulatory approval and construction.
The details of the MTEP15 reliability assessment are summarized in this chapter and the complete results are presented later in Appendix D of this MTEP15 report.
MTEP reliability assessment is a holistic study process that begins with MISO building a series of study cases. Using these models, MISO staff performs an independent reliability analysis of its transmission system. This independent assessment results in identification of system needs, which are mapped to project submittals by the area transmission planning entities. Finally, MISO staff coordinates with area transmission planners to verify needs, identify alternative solutions and resolve gaps where additional system upgrades may be required (Figure 4.1-1).
In MTEP 2015, MISO conducted regional studies using the following base cases and sensitivity cases developed collaboratively with our stakeholders:
- 2017 Summer Peak (wind at 20 percent)
- 2017 Light Load (wind at 90 percent)
- 2020 Summer Peak (wind at 20 percent)
- 2020 Shoulder Peak (wind at 40 percent)
- 2020 Shoulder Peak (wind at 90 percent)
- 2020 Light Load (wind at 90 percent)
- 2020 Winter Peak(wind at 30 percent)
- 2025 Summer Peak (wind at 20 percent)
Interchanges, generation, loads and losses are inputs into each planning model used in the MTEP15 reliability analysis.
MISO member companies and external Regional Transmission Organizations use firm drive-in and drive-out transactions to determine net interchanges for these models. These are documented in the 2014 series Multiregional Modeling Working Group (MMWG) interchange. MISO determines the total generation dispatch needed for each of the models after aggregating the total load with input received from TOs.
Generation dispatch within the model-building process is complex. Inputs from a variety of processesand expected shifts in the generation portfolio within the MISO footprint are key factors in this complexity.
Inputs in the dispatching process include:
- Generation retirements
- Generator market cost curves
- Generator deliverable capacity designation
- Wind generation output modeling under various system conditions
- Incremental generation needed to meet applicable renewable mandates
Loads are modeled based on direct input from MISO members. Generation dispatch is based on a number of assumptions, such as the modeling of wind. For example, wind generation is dispatched at 20 percent of nameplate in the summer peak case and 90 percent of nameplate in the shoulder and light-load cases. These wind dispatch levels were selected through MISO planning stakeholder process. More information on the models may be found in Appendix D2 of this report.
NERC Reliability Assessment
MISO conducts baseline reliability studies to ensure its transmission system is in compliance with three sets of standards:
- Applicable North American Electric Reliability Corp. (NERC) reliability standards
- Reliability standards adopted by Regional Entities (RE) applicable within the transmission provider region
- Local Transmission Owner (TO) planning criteria after it is filed and approved by Federal Energy Regulatory Commission (FERC)
Based on the NERC reliability assessment performed by MISO, potential thermal and voltage reliability issues are identified. MISO and its TOs are required to develop and implement solutions for each identified constraint. The majority of these identified violations may be mitigated via system reconfiguration, generation redispatch or implementation of an operating guide. For all other issues, mitigations, in the form of a future proposed transmission upgrade, will be identified for the projected thermal and voltage issues. These network upgrade mitigations will be investigated further in future MTEPs.
The results of these analyses create a cohesive long-term system reliability assessment, as well as documentary evidence for future NERC compliance. The complete study is available in Appendices D2-D8 of this report, which is posted on the MISO SFTP site. Each MTEP assessment undergoes three specific types of analysis: steady-state, dynamic stability and voltage stability.
Appendix E1.5.1 documents contingencies tested in steady-state analysis. These contingencies were used in the MTEP15 2017 summer peak and shoulder peak models; the 2020 summer peak, shoulder peak, winter peak and light-load models; and the 2025 summer peak model. All steady-state analysis-identified constraints and associated mitigations are contained in the results tables in Appendix D3, demonstrating compliance with applicable NERC transmission standards.
Dynamic Stability Analysis
Appendix E1.5.2 documents types of disturbances tested in dynamic stability analysis. Disturbances were simulated in MTEP15 2020 light load, shoulder (wind at 40 percent), shoulder (wind at 90 percent) and summer peak load models. Results tables listing all simulated disturbances along with damping ratios are tabulated in Appendix D5, demonstrating compliance with applicable NERC transmission standards.
Voltage Stability Analysis
Appendix E1.5.3 documents types of transfers tested in voltage stability analysis. A summary report with associated P-V plots is documented in Appendix D4.
Subregional Planning Meetings
MISO presents the project proposals and reliability study results to stakeholders through a series of public Subregional Planning Meetings (SPM). The locations of these SPMs are determined based on the five MISO planning subregions (Figure 4.1-2). The five MISO planning subregions are: Central (blue), East (red), South‑Arkansas (purple), South‑Mississippi, Louisiana and Texas (yellow) and West (green).
Additionally, Technical Study Task Force (TSTF) meetings are convened for each MISO planning subregion on an as-needed basis to discuss confidential system information (Table 4.1-1). These meetings are open to any stakeholders who sign Critical Energy Infrastructure Information (CEII) and non-disclosure agreements.
|4-Nov-14||Central TSTF Meeting (closed)||Web-ex/conf. call|
|3-Dec-14||West SPM No. 1||Eagan, Minn.|
|5-Dec-14||East SPM No. 1||Detroit, Mich.|
|8-Dec-14||Central SPM No. 1||Carmel, Ind.|
|9-Dec-14||South SPM No. 1 (Ark.)||Little Rock, Ark.|
|11-Dec-14||South SPM No. 1 (Miss., La., Texas)||Metairie, La.|
|10-Feb-15||West TSTF Meeting (closed)||Web-ex/conf. call|
|11-Feb-15||South TSTF Meeting (closed)||Metairie, La.|
|13-Feb-15||West TSTF Meeting (closed)||Web-ex/conf. call|
|26-Mar-15||Michigan TSTF Meeting||Livonia, Mich.|
|9-Apr-15||South TSTF Meeting (closed)||Web-ex/conf. call|
|1-May-15||East SPM No. 2||Novi, Mich.|
|5-May-15||South SPM No. 2 (Ark.)||Little Rock, Ark.|
|8-May-15||Central SPM No. 2||Carmel, Ind.|
|11-May-15||South SPM No. 2 (Miss., La., Texas)||Metairie, La.|
|19-May-15||West SPM No. 2||Eagan, Minn.|
|26-Jun-15||Michigan TSTF Meeting||Jackson, Mich.|
|24-Jul-15||South TSTF Meeting||Web-ex/conf. call|
|27-Jul-15||West SPM No. 3||Eagan, Minn.|
|30-Jul-15||Central SPM No. 3||Carmel, Ind.|
|4-Aug-15||East SPM No. 3||Cadillac, Mich.|
|4-Aug-15||South SPM No. 3 (Ark.)||Little Rock, Ark.|
|6-Aug-15||South SPM No. 3 (Miss., La., Texas)||Metairie, La.|
Table 4.1-1: MTEP15 Technical Study Task Force and Subregional Planning Meeting schedule
After MISO completes the independent review of all proposed projects and addresses any stakeholder feedback received during the SPM presentations, MISO staff formally recommends a set of projects to the MISO Board of Directors for review and approval. These projects make up Appendix A of the MTEP15 report and represent the preferred solutions to the identified transmission needs of the MISO reliability assessment. Proposed transmission upgrades with sufficient lead times are included in Appendix B for further review in future planning cycles. Details of the project approval process and the approved transmission projects reviewed this cycle are summarized in Chapter 2 and Appendix D1 of the MTEP15 report.