--- title: "Demand forecasting steps at load center" subject: "Transmission and Distribution System Design" chapter: 6 key: "semester_8/transmission_and_distribution_system_design:demand-forecast-load-center-steps" source: https://www.bctengineer.com/q/semester_8/transmission_and_distribution_system_design/demand-forecast-load-center-steps site: BCT Engineering --- # Demand forecasting steps at load center Transmission and Distribution System Design · Chapter 6: Electrical Load Characteristics and Load Forecast - Asked in: 2080 Chaitra, 8 marks - 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/demand-forecast-load-center-steps - Whole chapter: https://www.bctengineer.com/md/semester_8/transmission_and_distribution_system_design/chapter-6 ## Question Discuss the steps together with the data required for demand forecasting at a distribution system load center level. ## Short answer Steps: classify consumers, project numbers and monthly consumption to design year with growth and coverage, compute daily energy and individual peak using load factor, sum class peaks weighted by contribution factor, then add losses and convert to kVA. Required data: consumer counts, monthly kWh, effective days, load factors, contribution factors, growth rates, and coverage factor. ## Answer Demand forecasting at a **load centre** (a village, town ward or the service area of one distribution transformer) estimates the peak demand and energy at a design year (usually the 5th year after commissioning, sometimes 10th/15th) so that the transformer, LT feeders and HT tap line can be sized. The method used in Nepal (NEA and IOE practice) is a consumer-class based end-use method. #### Data required | Data | Use | |---|---| | Number of households, shops, institutions, industries (potential consumers) by class | Base consumer count | | Average monthly consumption per consumer of each class (kWh) | Energy per consumer | | Number of effective (working) days per month for each class | Daily energy | | Daily load pattern / load factor of each class | Converts energy to peak | | Contribution (responsibility) factor of each class to the load centre peak | Combines class peaks | | Population (consumer) growth rate | Growth in consumer number | | Consumption growth rate per year | Growth in kWh per consumer | | Electrification coverage factor by design year | Fraction actually connected | | Project implementation period, power factor, loss allowance | Timing and kVA rating | These come from field survey, census data, NEA billing records of similar electrified areas and socio-economic studies. #### Steps 1. **Survey and classify consumers**: domestic, commercial, non-commercial (institutions, schools, offices), industrial, irrigation, street lighting. 2. **Base year consumption**: fix average monthly kWh per consumer of each class from similar electrified areas. 3. **Project consumer numbers** to the design year $n$: $N_n = N_0 (1+p)^n \times \text{coverage factor}$, where $p$ is population growth rate. Include the implementation period in $n$. 4. **Project consumption per consumer**: $E_n = E_0 (1+g)^n$, where $g$ is consumption growth rate. 5. **Daily energy per consumer**: $E_{day} = E_n / \text{effective days per month}$. 6. **Individual peak** from load factor: $P_{ind} = \dfrac{E_{day}}{24 \times LF}$. 7. **Class peak**: $P_{class} = N_n \times P_{ind}$ (times a coincidence factor if given). 8. **Load centre peak**: $P_{LC} = \sum (\text{contribution factor} \times P_{class})$. 9. **Add losses and convert to kVA**: $S = P_{LC}(1 + \text{loss allowance}) / \cos\phi$; then choose the next standard transformer size (25, 50, 100, 200 kVA…). 10. **Annual energy**: $\sum N_n E_n \times 12$ for revenue and loss studies. The result gives transformer rating, LT feeder loading, and the demand that the 11 kV feeder must carry. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which data set is needed for load-centre demand forecasting? A. Only the transformer nameplate B. Consumers by class, monthly kWh, effective days, load factor, contribution factor, growth rates and coverage factor C. Only the weather history D. Only the length of the LT lines Answer: B. Class-wise consumer numbers, consumption, load factors, contribution factors, growth and coverage are the inputs for the end-use method. (Key point: Data required) 2. How is the number of consumers in design year n projected? A. N0 (1+p)^n x coverage factor B. N0 x p x n C. N0 / (1+p)^n D. N0 + coverage Answer: A. Population growth p is compounded over n years (including implementation period) and multiplied by the coverage factor. (Key point: Consumer projection) 3. What is the correct order to get the class peak? A. Daily energy x 24 x LF, then multiply by N B. Monthly energy / effective days, then divide by (24 x LF), then multiply by N C. Monthly energy x LF, then divide by 24 D. Monthly energy / 30, then multiply by LF Answer: B. E_day = En/effective days, P_ind = E_day/(24 LF), P_class = N x P_ind. (Key point: Energy to peak) 4. How is the transformer size finally decided? A. Sum of class peaks only, in kW B. Sum of contribution factor x class peak, add loss allowance, divide by power factor to get kVA, then choose next standard size C. Average of class peaks in kW D. Annual energy divided by 8760 Answer: B. Load-centre peak is converted to kVA with losses and pf, then rounded up to a standard rating. 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