Electric Power Distribution
The final stage of electricity delivery: carrying power from the Electric Power Transmission system to individual consumers. Managed by distribution system operators (DSOs) — in Sweden, these are the elnätsföretag (grid companies), e.g. E.ON Energidistribution, Ellevio, Vattenfall Eldistribution.
How it works
- Distribution Substations receive power from the transmission/subtransmission grid and step voltage down to medium voltage (2–33 kV).
- Primary distribution lines (feeders) carry medium-voltage power along streets, overhead or underground.
- Distribution transformers near customer premises step down to utilization voltage (230/400 V in Sweden/Europe).
- Service drops connect individual customers.
Network configurations
- Radial: tree-like, each customer has one supply path. Common in rural/suburban areas. Includes emergency reconfiguration capability.
- Network: multiple parallel supply paths. Used in dense urban areas for higher reliability.
Regional specifics (Europe / Sweden)
- 50 Hz, 230 V single-phase / 400 V three-phase
- Typical urban/suburban substation: 150 kVA to 1 MVA, serving a few hundred houses
- Average load sizing: 1–2 kW per household, with peak draw allowance of ~10x
- Large industrial/commercial customers may have own transformers at 11–33 kV
The distribution grid is changing
Traditionally a passive, one-way delivery system. Now becoming an active, bidirectional network due to:
- Distributed generation: rooftop solar, small wind, microgeneration
- Electric vehicles: both as load and potential storage (V2G)
- Heat pumps: significant new load
- Battery storage: behind-the-meter and grid-scale
This transformation is what makes Flexibility at the distribution level necessary. The DSO must manage bidirectional flows, local Congestion Management, and voltage quality — challenges that didn’t exist when power only flowed one way. Demand Response and other flexibility mechanisms become essential tools for DSOs managing this transition.
Market structure
Distribution remains a regulated Natural Monopoly — unlike generation and retail, which were liberalized starting in the 1970s–1990s. The DSO owns and operates the physical network but (in unbundled markets) does not sell energy. The Clean Energy Package formalizes this: the Electricity Market Directive requires DSOs to act as neutral market facilitators (Art. 31(5)), to procure flexibility via market-based procedures (Art. 32), and prohibits DSO ownership of energy storage (Art. 36, with derogations). In practice, Swedish DSOs use both Villkorade Avtal (conditional connections with curtailment obligations) and local flexibility markets to manage congestion.