# Distribution grids, mini-grids and interconnectors: How it works

From substation to meter, and solar mini-grids where wires end

Source page: https://www.materialinsights.org/energy/e_distribution/explain/

What this tab covers How the energy actually moves, step by step: the science that makes it work and the engineering that makes it practical.

Distribution networks take power from high-voltage substations and deliver it at falling voltages along local lines to every meter. Mini-grids do the same job for a village or site with their own generation, and interconnectors join national grids so they can trade and back each other up.

#### Step by step

1. **Primary substation**Transformers take power from the transmission grid and lower it to medium voltage, for example the 20 kV used across most of France's distribution network.
2. **Medium-voltage feeders**Overhead lines or underground cables carry power through towns and countryside, with switchgear that can isolate faulty sections.
3. **Distribution transformer**A pole-mounted or ground-mounted transformer near the street lowers the voltage again to the low voltage used by homes and shops.
4. **Service line and meter**A short cable connects each building; a meter, increasingly smart or prepaid, records use for billing.
5. **Mini-grid alternative**Where the main grid does not reach, a local solar-battery plant with diesel backup feeds its own small network serving a few hundred customers.
6. **Interconnector**At borders, AC lines or HVDC links join national systems so surplus or cheaper power can flow where it is needed.

#### The science

Heat lost equals current squared times resistance, so voltage is kept as high as practical for as long as possible and lowered only near the customer. Low-voltage circuits carry high currents, so losses per kilometre are relatively high in this last stage. Transformers work only on AC, one reason distribution is AC. In a solar mini-grid, panels make DC, batteries store DC, and inverters convert it to AC for the local network.

#### The engineering

Distribution is the largest part of the grid by length: Enedis in France alone runs about 1.4 million km of lines. Networks are mostly radial (branching like a tree) so faults can be isolated, increasingly with automated switches, sensors and remote control. Third-generation mini-grids are privately run solar-hybrid systems with prepaid smart meters and remote monitoring, often designed to connect to the main grid later.

#### Key numbers
 Enedis distribution network, France About 1.4 million km^[15](https://www.enlit.world/library/enedis-and-abb-partner-on-sf6-free-switchgear) Mini-grids installed worldwide (about 2021) 21,557 in 131 countries and territories, serving over 48 million people^[7](https://openknowledge.worldbank.org/bitstreams/dc000258-8524-594f-a2ee-e1ee7a256f6b/download) Typical third-generation mini-grid 50 to 100 kWp solar, 200 to 500 kWh batteries, 200 to 800 customers^[7](https://openknowledge.worldbank.org/bitstreams/dc000258-8524-594f-a2ee-e1ee7a256f6b/download) European cross-border exchange capacity 116 GW in 2024^[10](https://ember-energy.org/latest-insights/money-on-the-line-scaling-electricity-interconnection-for-europes-energy-future/) People without electricity About 750 million, about 80% in sub-Saharan Africa^[19](https://www.iea.org/reports/building-the-future-transmission-grid/executive-summary)

#### Sources

1. [Mini Grids for Half a Billion People: Market Outlook and Handbook for Decision Makers (2022 edition)](https://openknowledge.worldbank.org/bitstreams/dc000258-8524-594f-a2ee-e1ee7a256f6b/download) World Bank ESMAP, 2022
2. [Money on the line: scaling electricity interconnection for Europe's energy future](https://ember-energy.org/latest-insights/money-on-the-line-scaling-electricity-interconnection-for-europes-energy-future/) Ember, 2025
3. [Enedis and ABB partner on SF6-free switchgear](https://www.enlit.world/library/enedis-and-abb-partner-on-sf6-free-switchgear) Enlit World, 2025
4. [Building the Future Transmission Grid: Executive summary](https://www.iea.org/reports/building-the-future-transmission-grid/executive-summary) IEA, 2025

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_distribution/index.md)
- [Overview](https://www.materialinsights.org/energy/e_distribution/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_distribution/correlation/index.md)
- [Efficiency and losses](https://www.materialinsights.org/energy/e_distribution/efficiency/index.md)
- [Technology advances](https://www.materialinsights.org/energy/e_distribution/advances/index.md)
- [Value chain](https://www.materialinsights.org/energy/e_distribution/valuechain/index.md)
- [Geopolitics and regulation](https://www.materialinsights.org/energy/e_distribution/geopolitics/index.md)
- [Unit economics](https://www.materialinsights.org/energy/e_distribution/economics/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_distribution/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_distribution/links/index.md)