Demand forecasting steps at load center

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

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.