Planning Criteria, Assessment Practices and Tools

New May 1, 2020  – Updated Planning Criteria (20):  ATC’s updated Planning Criteria (20) can be found here.  No substantive changes except to update the version number to match the 2020 Assessment year.  Previously updated to include the single line to ground fault type as part of the stability studies for NERC Planning Events that are only defined as three phase faults in Table 1 of the TPL standard.  Replaced Pmax/Qmax with machine MVA base for active power and reactive damping calculation.  Added NERC’s recommendation on momentary cessation .

New May 1, 2020 – Updated Planning Assessment Practices (20):  ATC’s updated Planning Assessment Practices (20) can be found here.  No substantive changes except to update the version number to match the 2020 Assessment year.  Previously the 5% Transmission Reliability Margin (TRM) rating reduction requirement for MISO generation interconnection studies was removed.

The following versions of the criteria and assessment practices Planning Criteria version 19.2 and Planning Assessment Practices version 7.2 were used for the 2019 Assessment.

Planning Criteria

We employ various system planning criteria to plan, design, build and operate our transmission system in a safe, reliable and economic manner to meet the needs of its customers while maintaining compliance with NERC standards. This criteria applies to the ATC transmission system operated at 69-kV and above.

These criteria may be revised from time to time in response to changes in industry standards, new system conditions, new technologies and new operating procedures, as appropriate. These criteria are subject to change at any time at ATC’s discretion. Situations that could precipitate such a change could include, but are not limited to, new system conditions, extraordinary events, safety issues, operation issues, maintenance issues, customer requests, regulatory requirements and Regional Entity or NERC requirements.

Planning Assessment Practices

American Transmission Company (ATC) generally subscribes to the zone approach to transmission planning assessment using a multi-level planning concept. Diagrams of the planning zones for which regional plans have been developed by ATC are attached in the response to Part 3 of Federal Energy Regulatory Commission (FERC) Form 715 and show the existing transmission facilities, 100-kV and above, within ATC’s transmission system.

The concept behind the zone approach to transmission planning is to develop plans that consider all of the needs, limitations and developments within each zone and develop an overall plan for the zone (that is, a plan that emphasizes projects that serve multiple purposes or solve multiple limitations within the zone). In addition, ATC’s transmission planning philosophies incorporate the concept of multi-level transmission planning. When carrying out a comprehensive transmission planning process, consideration must be given not only to transmission needs, zone needs and ATC-wide needs, but also to plans of other transmission providers. Solutions identified via planning activities within each level are vetted against those in adjacent levels until the most effective overall comprehensive plan is developed. ATC’s planning process will continue to develop the first three levels (individual, zone, ATC-wide). ATC is participating with other Transmission Owners, such as ComEd, DPC, NSP and ITC, which are within or may be affected by the MISO territory, when assessing regional needs.

ATC employs the long-standing practice of using power flow analysis to identify needs and limitations and to evaluate alternative mitigation measures. ATC identifies limitations and needs by simulating non-simultaneous and selected simultaneous outages of each line, transformer, bus section, and generator. ATC does implement operating guides, such as opening lines and bus sections, to mitigate limitations (overloads, low voltages, etc.) during extreme flow conditions.

ATC also conducts dynamic stability analyses within each of its zones to assess the ability of its system to withstand power system disturbances. Many of these analyses have been or are being conducted in conjunction with proposed generation interconnections. Other independent analyses are being conducted to assess dynamic and/or voltage stability performance.

ATC develops transmission projects to address the congestion issues in its footprint and beyond. ATC uses the PROMOD model to analyze congestion across the ATC footprint and surrounding systems and develops projects that will relieve the congestion.

Further, ATC works with neighboring transmission owners, stakeholders and MISO to develop transmission projects that provide multiple benefits including reliability, economic and public policy benefits. These projects are often more strategic and regional in nature to help provide benefit to multiple areas as well as maintain reliability in the ATC footprint well into the future. These projects are evaluated using traditional reliability planning tools, PROMOD for economic benefits and a combination of traditional first contingency incremental transfer capability (FCITC) analysis and economic analysis to quantify their public policy benefits.

As part of MISO, ATC participates in the MISO Transmission Expansion Planning (MTEP) process. ATC participates actively in all portions of MISO’s planning efforts, including numerous committees and task forces, in regional and economic study efforts and in development of the MTEP.

ATC solicits public and other stakeholder input on the identification of ultimate solutions through its iterative planning process. Projects may be modified as potential solutions listed in this assessment and further developed to address the specific needs identified by all stakeholders. The solutions selected to address the needs and limitations identified will reflect the input of transmission planning process stakeholders, including customers, state and local officials, the public, and coordination with other planning processes, to the extent possible.

Specific opportunities for public and stakeholder participation in the planning process are provided in accordance with ATC’s portion of the MISO tariff, Attachment FF – ATCLLC. In particular, this tariff, filed with and approved by FERC, addresses portions of FERC Orders 890 and 1000 calling for open, inclusive and transparent planning processes. Attachment FF – ATCLLC coverage includes planning processes and functions as well as opportunities for stakeholders to participate. The planning processes and functions include:

  1. Network adequacy planning
  2. Economic project planning
  3. Generation-transmission interconnections
  4. Transmission-distribution interconnections
  5. Transmission-transmission interconnections
  6. Transmission service requests
  7. Public policy

Provisions include opportunities for stakeholders to provide input to the planning processes in terms of assumptions and projects, providing review of interim results, and examination of final results.

ATC participates in regional transmission assessments conducted by the Reliability First (RF) Transmission Performance Subcommittee (TPS), the NERC ERAG Reliability Assessments and MISO Reliability Assessments.

In addition to those listed in its planning criteria, ATC considers a number of other factors in its transmission planning process.

Planning tools

Our planning engineers frequently use the following computer applications to simulate the impact of potential future events on the transmission system. The same applications are used to determine how proposed solutions would address any identified adverse impacts.

Ventyx PROMODpredicts the cost of producing energy to serve customers.
Burchett Inc. PROMOD Analysis Tool (PAT)post-processing analytic capability for PROMOD results
PowerGem TARAcalculates linear (DC) and non-linear (AC) power flow, performs N-1/N-1-1 reliability analysis, calculates transfer limits, determines preventive and corrective dispatch
Siemens (PTI) PSS/Ecalculates static and dynamic power flows
PowerTech VSAT/TSAT/PSAT/SSATVSAT calculates the capability of the system to transfer power from one area to another while respecting voltage limitations. TSAT assesses the dynamic behavior of the system under specified condition. PSAT calculates static power flows. SSAT analyzes the small signal stability of the system
Power World Corp PowerWorldcalculates static power flows with a visual interface
V&R Energy Systems Research POM/OPMdetermines “Expected Unserved Energy”, a measure of the ability of the system to deliver resources to meet customer demand.
PSCADPSCAD is a three phase electromagnetic transient (EMT) simulation program that can analyze power flows that include “electronic power” devices. Electronic power devices, (such as those that wind and solar renewable generation employ), have extremely fast internal switching transients, that traditional power flow programs (e.g. PSS/E) fail to detect.
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