SOPD Load Forecasting & Energy Scheduling 5 — Questions and Answers
Question 1: Which metric BEST measures the accuracy of a load forecast over time?
- Peak demand growth rate
- Mean Absolute Percentage Error (MAPE) (Correct answer)
- Standard deviation of generation output
- Frequency deviation integral
Correct answer: Mean Absolute Percentage Error (MAPE)
MAPE expresses forecast error as a percentage of actual load, allowing comparison of accuracy across different load levels and time periods.
Question 2: A system operator must schedule hydro generation for a river system with limited reservoir capacity. The MOST important constraint in this schedule is:
- Generator reactive power limits
- Water discharge requirements and downstream flow obligations (Correct answer)
- Transmission line impedance values
- Minimum stable generation for thermal units
Correct answer: Water discharge requirements and downstream flow obligations
Hydro scheduling must respect water availability, reservoir storage limits, minimum downstream flow requirements, and environmental/regulatory discharge obligations.
Question 3: When an energy schedule is 'tagged' through an energy management system (EMS), this means the schedule has been:
- Rejected by the neighboring control area
- Confirmed and approved for interchange between control areas (Correct answer)
- Flagged as a potential reliability violation
- Assigned to a specific transmission path for billing
Correct answer: Confirmed and approved for interchange between control areas
Tagging an interchange schedule confirms it has been approved by all relevant control areas and is ready for implementation as a binding energy transfer.
Question 4: Load forecasting accuracy typically DECREASES as the forecast horizon increases because:
- Computer processing power limits longer-term calculations
- Weather and economic uncertainties compound over longer time periods (Correct answer)
- NERC standards prohibit forecasts beyond 24 hours
- Long-term forecasts must use different software than short-term forecasts
Correct answer: Weather and economic uncertainties compound over longer time periods
Longer forecast horizons accumulate uncertainty in weather forecasts, economic conditions, customer behavior, and unforeseen events, reducing forecast accuracy.
Question 5: A control area's 'load-following' service differs from 'regulation' service in that load-following:
- Responds to automatic generation control signals every 4 seconds
- Addresses slower, predictable load changes over minutes to hours (Correct answer)
- Is procured only from intermittent renewable resources
- Operates exclusively during emergency frequency events
Correct answer: Addresses slower, predictable load changes over minutes to hours
Load-following resources address gradual, predictable demand changes over minutes to hours, while regulation addresses fast, random fluctuations via AGC signals.
Question 6: Which of the following BEST describes the purpose of a 'load shape' in energy scheduling?
- The geographic distribution of load across substations
- The hourly or sub-hourly pattern of demand over a day or week (Correct answer)
- The reactive power profile of industrial customers
- The seasonal capacity factor of a generating unit
Correct answer: The hourly or sub-hourly pattern of demand over a day or week
A load shape describes the time-varying pattern of electricity demand, showing how load rises and falls across hours of the day or days of the week.
Question 7: During energy scheduling, if a generator's 'must-run' status is designated, this means the unit:
- Must operate at maximum output at all times
- Must remain online regardless of economic dispatch results due to reliability needs (Correct answer)
- Is required to provide all spinning reserves for the system
- Can only be committed during peak demand periods
Correct answer: Must remain online regardless of economic dispatch results due to reliability needs
Must-run status requires a unit to stay online because it provides essential reliability services (such as local voltage support) that cannot be replaced by economic dispatch decisions.
SOPD Load Forecasting & Energy Scheduling 5
Which metric BEST measures the accuracy of a load forecast over time?