MTEP15 Chapter 6.4 Seasonal Resource Assessment

MTEP15 Chapter 6.4 Seasonal Resource Assessment

MISO conducts seasonal resource assessments for the winter months of December, January and February as well as for summer months of June, July and August. Seasonal assessments primarily evaluate the near-term system performance expected, and prepare the operators with a focused look at the upcoming season. The MISO resource assessments coincide with NERC seasonal reliability assessments and MISO operational readiness workshops held prior to the assessment’s season.

The finding showed that the projected capacity levels exceed the Planning Reserve Margin Requirement in both the 2014-2015 winter and 2015 summer seasons, with adequate resources to serve load.

Seasonal Assessment Methods

MISO studies multiple scenarios at varying capacity resource levels, expected demand levels and forced outage rates. In order to align with intra-RTO expected dispatch, only 1,000 MW above the MISO South load and reserve margin were counted toward aggregate margins at coincident peak demand in all of the projected scenarios.

MISO coordinates extensively with neighboring reliability coordinators as part of the seasonal assessment and outage coordination processes, and via scheduled daily conference calls and ad-hoc communications as need arises in real-time operations. There is always the potential for a combination of higher loads, higher forced outage rates and fuel limitations. In the summer, unusually hot and dry weather can lead to low water levels and/or high water temperatures. This can impact the maximum operating capacity of thermal generators that rely on water resources for cooling, leading to added deratings in real time and lowering functional capacity. These situations would be resolved through existing procedures depending on the circumstances, and several scenarios are studied for each season to project the possible reserve margins expected.

Demand

Based on 20 years of historic actual load data, MISO calculates a Load Forecast Uncertainty (LFU) value from statistical analysis to determine how likely actual load will deviate from forecasts. A normal distribution is created around the 50/50 forecast based on a standard deviation equal to the LFU of the 50/50 forecast. This curve represents all possible load levels with their associated probability of occurrence. At any point along the curve it is possible to derive the percent chance that load will be above or below a load value by finding the area under the curve to the right or left of that point. MISO chooses the 90th percentile for the High Load scenarios. For more information regarding this analysis, refer to the Planning Year 2015 LOLE Study.

Demand Reporting

MISO does not forecast load for the Seasonal Resource Assessments. Instead, Load Serving Entities (LSEs) report load projections under the Resource Adequacy Requirements section (Module E-1) of the MISO Tariff. LSEs report their annual load projections on a MISO Coincident basis as well as their Non-Coincident load projections for the next 10 years, monthly for the first two years and seasonally for the remaining eight years. MISO LSEs have the best information of their load; therefore, MISO relies on them for load forecast information.

For these studies, MISO created a Non-Coincident and a Coincident peak demand on a regional basis by summing the annual peak forecasts for the individual LSEs in the larger regional area of interest.

Figure 6.4-1: Winter 2014-2015 Projected Reserve Margin scenarios (GW)

Figure 6.4-1: Winter 2014-2015 Projected Reserve Margin scenarios (GW)

2014-2015 Winter Overview

For planning year 2014-2015, MISO’s Planning Reserve Margin Requirement (PRMR) was 14.8 percent. For the 2014-2015 winter peak hour, MISO expected adequate resources to serve load, with a NERC-reported base projected reserve margin of 43.2 percent, which far exceeds the PRMR of 14.8 percent. The winter scenarios project the reserve margin to be in the range of 35.0 to 45.1 percent. Figure 6.4-1 represents an overview of these scenarios.

MISO’s 50/50 coincident peak demand for the 2014-2015 winter season was forecasted to be 103,238 MW including transmission losses, with 147,793 MW of capacity to serve MISO load during the 2014-2015 winter season. Excluded from the capacity are 3,811 MW of MISO South resources to align with the 1,000 MW intra-RTO contract path.

 

2014-2015 Winter Rated Capacity

For the 2014-2015 winter season, MISO projected 147,793 MW of existing certain capacity to serve MISO load during the winter. The capacity includes 1,614 MW of Behind-the-Meter Generation (BTMG) and 3,645 MW of Demand Resource (DR) programs, with 2,022 MW of Net Firm Imports. MISO expected 1,070 MW of wind capacity to be available to serve load for the winter.

MISO arrived at the Winter Rated Capacity value by reducing the Nameplate Capacity of its market footprint by multiple variables. The majority of the derates expected at-peak are due to resource interconnection limitations of 6,160 MW; thermal unit winter output reductions of 4,796 MW; and reductions due to the Effective Load Carrying Capability of wind resources of 10,052 MW. Capacity from the South, equal to its load and reserve margin requirement, was included in the regional total. Additionally, it assumed that 1,000 MW of excess capacity transferred to the North/Central region of the footprint.

For more information regarding methodology and assumptions of the Winter Rated Capacity, refer to Appendix A.2 of the 2014-2015 Winter Resource Assessment.

Winter Reserve Margin Scenarios

MISO’s projected 2014-2015 MISO Winter Rated Capacity varies by scenario (Figures 6.4-2 through 6.4-6). MISO chose the 90th percentile of the normal distribution around a 50/50 load forecast for the High Load scenarios, which was 110,597 MW for the 2014-2015 winter. For more information regarding each scenario, refer to Appendix A.3 of the 2014-2015 Winter Resource Assessment.

The Anticipated Scenario contains additional assumptions (Figure 6.4-3). MISO expects that any Energy Resource without firm point-to-point Transmission Service Rights will serve load locally, termed Energy Only. The portion of Energy Only from the MISO South region is excluded from the calculation to align with 1,000 MW contract path limitation.

 

In real-time, during normal operating conditions, MISO must carry Operating Reserves above load to maintain system reliability. The amount of Operating Reserves required to clear on a daily basis for the 2014/2015 winter season was 2,400 MW, which is called on as a last resort before load shed (Figure 6.4-4). These reserves are made up of a combination of Regulating Reserves, Spinning Reserves and Supplemental Reserves.

The High Demand, High Outage Scenario has added assumptions (Figure 6.4-5). Beginning with the Anticipated Reserves from the Anticipated Scenario (Figure 6.4-3), the load is increased to show the higher load from a 90/10 forecast. A higher forced outage rate is assumed, using the highest historical forced outage rate applied to the capacity resources available. An extreme forced outage rate is applied to the Extreme Scenario (Figure 6.4-6), based on information from the polar vortex of the 2013-2014 winter.

 

 

2015 Summer Overview

For planning year 2015-2016, MISO’s PRMR is 14.3 percent, which is 0.5 percentage points lower than the previous year’s requirement of 14.8 percent. During the 2015 summer peak hour, MISO expected adequate resources to serve load, with a NERC-reported base projected reserve margin as 18.0 percent, which exceeds the requirement of 14.3 percent by 3.7 percentage points. The summer scenarios project the reserve margin to be in the range of 14.4 to 20.1 percent (Figure 6.4-7).

MISO’s 50/50 coincident peak demand for the 2015 summer season was forecasted to be 127,319 MW including transmission losses, with 150,270 MW of capacity to serve MISO load. Excluded from the capacity are 3,806 MW of MISO South resources to align with the 1,000 MW intra-RTO contract path.

2015 Summer Rated Capacity

For 2015, MISO projected 150,270 MW of capacity to serve MISO load during the 2015 summer season. The capacity includes 4,413 MW of Behind-the-Meter Generation and 5,938 MW of Demand Resource programs, while removing 56 MW of Net Firm Exports. MISO expected 1,325 MW of wind capacity to be available to serve load this summer. Capacity from the South equal to its load and reserve margin requirement was included in the regional total. Additionally, 1,000 MW of excess capacity was assumed to be transferred to the North/Central region of the footprint.

MISO arrived at the Summer Rated Capacity value by reducing the Nameplate Capacity of its market footprint by multiple variables. The majority of the derates expected at-peak are due to resource interconnection limitations (3,616 MW); thermal unit summer output reductions (11,765 MW); and reductions due to the Effective Load Carrying Capability of wind resources (9,534 MW). Also, any MISO South capacity over the total of South Load, South reserve margin requirement, and 1,000 MW of contract path was not included in the regional value. This means that 3,806 MW of MISO South excess capacity was excluded from the calculation to align with 1,000 MW contract path limitation.

For more information regarding methodology and assumptions of the Summer Rated Capacity, refer to Figure 6.4-13.

Reserve Margin Scenarios

MISO’s projected 2015 MISO Summer Rated Capacity varies by scenario (Figures 6.4-8 through 6.4-10). MISO chose the 90th percentile of the normal distribution around a 50/50 load forecast for the High Load scenarios, which was 133,599 MW for the 2015 summer. For more information regarding each scenario, refer to the MISO 2015 Summer Resource Assessment.

The Probable Scenario uses additional assumptions (Figure 6.4-9). MISO expects that any Energy Resource without firm point-to-point Transmission Service Rights will serve load locally, termed Energy Only. The portion of Energy Only from the MISO South region is excluded from the calculation to align with 1,000 MW contract path limitation. In addition, 0.2 GW of capacity is included from provisional wind that is connected to the system but with an incomplete interconnection process. Finally, any units designated as System Support Resources (SSR) or Under Study through the Attachment Y process are considered available, as well as units that received a waiver from participating in the Planning Resource Auction but will still run for the summer.

The High Demand, High Outage scenario has added assumptions (Figure 6.4-10). Beginning with the Probable Reserves from the Probable Scenario (Figure 6.4-9), the load is increased to show the higher load from a 90/10 forecast. Also a higher forced outage rate is assumed, using the highest historical forced outage rate applied to the capacity resources available.

2015 Summer Risk Assessment

MISO performs a probabilistic assessment on the region to determine the percent chance of utilizing Load Modifying Resources and Operating Reserves or having to curtail firm load. A risk profile is generated from this analysis (Figure 6.4-11).

It is always possible for a combination of higher loads, higher forced outage rates, fuel limitations, low water levels and other factors to lead to the curtailment of firm load. The Loss of Load Expectation (LOLE) model that MISO utilizes for PRMR takes into account the uncertainties associated with load forecasts (i.e., 50/50 v. 90/10) and generation outages (both forced and scheduled).

The chance of realizing an event is where the risk profile intersects the event range (Figure 6.4-11). As shown, the probabilistic analysis indicated a 74.1 percent chance of MISO calling a Maximum Generation Emergency Event Step 2b to access Load Modifying Resources; a 7.8 percent chance of initiating further steps to access Operating Reserves; and a 2.7 percent chance of curtailing firm load during 2015 summer peak hour.

The reserves available in the Probable Scenario are shown after forced outages are applied, showing the amount of Generation, Behind-the-Meter Generation, Demand Resource and Operating Reserves expected (Figure 6.4-12). In real-time, during normal operating conditions, MISO must carry Operating Reserves above load to maintain system reliability. The amount of Operating Reserves required to clear on a daily basis for the 2015 summer season was 2,400 MW, which is called on as a last resort before load shed. These reserves are made up of a combination of Regulating Reserves, Spinning Reserves and Supplemental Reserves.

For more information regarding the risk assessment methodology, assumptions and variables, refer to Appendix A.1 of the MISO 2015 Summer Resource Assessment.

MISO Summer Rated Capacity Methodology

The calculation of MISO Summer Rated Capacity resources is easier to describe by separating into thirteen parts (Figure 6.4-13) and as described in the following list. Separation of the Winter Rated Capacity is similar, with additional details found in the MISO 2014-2015 Winter Resource Assessment.

  1. Nameplate capacity is the summation of the maximum output from the latest commercial model. This reflects the amount of registered generation available internal to MISO.
  2. Inoperable resources is the summation of approved mothballed or retired units determined through the Attachment Y process, which are still represented in the latest commercial model.
  3. Thermal derates on-peak is the summation of differences in unit nameplate capacities and the latest Generator Verification Test Capacity (GVTC) results, excluding inoperable resources.
  4. All other derates is the summation of differences in non-wind intermittent resource nameplate capacities and the resource averages of historical summer peak performance, excluding inoperable resources.
  5. Transmission-limited resources is the summation of differences in GVTC and the unit’s Total Interconnection Service (TIS) rights based on latest unit deliverability test results. Transmission-limited resources for wind is the summation of differences in nameplate capacity and TIS.
  6. Not-in-service units and provisional wind: Units that are registered in the latest commercial model, but are not in service yet; the wind units that are connected to the system but their interconnection process is not completed yet.
  7. Wind derates on-peak is the summation of the differences in wind unit Nameplate Capacities and the unit wind capacity credit, which is determined based on the Effective Load Carrying Capability of wind. This excludes Inoperable Resources and Transmission-Limited MWs.
  8. Energy-only resources are the ones that have Energy Resource Integration Rights (ERIS) without a firm point to point Transmission Service Right.
  9. Scheduled maintenance: Scheduled generator outages from June 1, 2015 through August 31, 2015 were pulled from MISO’s Control Room Operator’s Window (CROW) outage scheduler on March 17, 2015. The data pulled met the following criteria: 1. Mapped to the latest commercial model; 2. Outage Request Status is equal to Active, Approved, Pre-Approved, Proposed, Study, or Submitted; 3. Request priority is equal to planned; 4. Equipment request type is equal to Out of Service (OOS) or “Derated To 0 MW.” This calculation amounts to an expected scheduled maintenance of 574 MW. In order to calculate the expected scheduled outages on peak, MISO calculates the amount of outages on a daily basis assuming that if a unit is out for as little as one hour, that unit will be out for that entire day. The highest amount of outages during the month of July is assumed to be equal to the amount of outage during summer peak conditions.
  10. MISO anticipated the net firm interchange to be exporting 56 MW for the 2015 summer.
  11. 3,806 MW of MISO South resources were excluded from the available capacity to align with 1,000 MW intra-RTO contract path.
  12. Behind-the-Meter Generation is the summation of approved and cleared load-modifying resources identified as Behind-the-Meter Generation through the Resource Adequacy (Module E) process. Based on the planning year 2015-2016 Planning Resource Auction, 4,413 MW of BTMG cleared to be available for the 2015 summer season.
  13. Demand resource: MISO currently separates contractual demand resource into two separate categories, Direct Control Load Management (DCLM) and Interruptible Load (IL).IL is the magnitude of customer demand (usually industrial) that, in accordance with contractual arrangements, can be interrupted at the time of peak by direct control of the system operator (remote tripping) or by action of the customer at the direct request of the system operator. The amount of registered and cleared load-modifying resources identified as demand resource through the Resource Adequacy (Module E) process is 5,938 MW for the 2015 summer season. DCLM is the magnitude of customer service (usually residential) that can be interrupted at the time of peak by direct control of the applicable system operator. DCLM is typically used for “peak shaving.” In MISO, air conditioner interruption programs account for the vast majority of DCLM during the summer months.