--- title: "Small area forecasting with load growth curve" subject: "Transmission and Distribution System Design" chapter: 6 key: "semester_8/transmission_and_distribution_system_design:small-area-load-growth-curve" source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/small-area-load-growth-curve site: BCT Engineering --- # Small area forecasting with load growth curve Transmission and Distribution System Design · Chapter 6: Electrical Load Characteristics and Load Forecast - Asked in: 2074 Bhadra, 4 marks - Video: [Load Growth Characteristics - Load Forecasting -Power System Planning and Reliability](https://www.youtube.com/watch?v=kQqElTphg3w) — Ekeeda - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/small-area-load-growth-curve - Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-6 ## Question Explain the small area load forecasting with the help of load growth curve of small area. ## Short answer Small-area load follows an S-curve: a dormant phase with near-zero load, rapid growth after development starts, and saturation at full build-out. Forecasting uses Gompertz curve fitting and land-use simulation to predict growth onset. ## Answer **Small area load forecasting** predicts the load of small zones (a feeder area, a grid cell of a few hectares) so that the location and timing of new substations, transformers and feeders can be planned. The load of a small area follows an **S-shaped growth curve** (Gompertz-type), unlike the smooth growth of a large area: ```text Load ^ ___________ saturation | _/ | _/ | / rapid growth | _/ | _/ | __________/ dormant +-----------------------------------> Years | I | II | III ``` 1. **Dormant period (I):** the land is vacant or farmland; load is almost zero for many years. 2. **Rapid growth (II):** once development starts (new roads, housing, shops), load rises very fast, often over 5–10 years. The timing of this start is hard to predict. 3. **Saturation (III):** the area is fully developed; load grows slowly, only through higher consumption per consumer. **Forecasting using the curve:** - Each small area is located on its S-curve. Areas in the growth phase are forecast by fitting a Gompertz curve, $P(t) = a\,e^{-b e^{-ct}}$, to recent data, with the saturation level $a$ taken from land area × load density of the planned land use. - Areas in the dormant phase cannot be trended; their start of growth is predicted by the **simulation (land-use) method** using zoning plans and infrastructure development. - The sum of small-area forecasts is checked against the large-area (system) forecast. The curve shows why trending alone fails for small areas and why spatial land-use information is required. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What shape does a small-area load growth curve have? A. Straight line B. S-shaped (Gompertz-type) C. Falling exponential D. Sine wave Answer: B. Load stays near zero, grows rapidly, then saturates. (Key point: Curve shape) 2. What are the three stages in order? A. Saturation, growth, dormant B. Dormant, rapid growth, saturation C. Rapid growth, dormant, saturation D. Dormant, saturation, rapid growth Answer: B. Vacant land gives almost zero load, development gives fast growth, then the area is fully developed. (Key point: Three stages) 3. How are areas in each stage forecast? A. Growth phase by fitting a Gompertz curve with saturation from land area x load density; dormant areas by land-use simulation B. All areas by linear trend C. Dormant areas by Gompertz fitting D. Saturated areas by Delphi only Answer: A. Dormant areas cannot be trended, so their growth start is predicted from zoning and infrastructure plans. 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