Source - Substation (Wikipedia)
Source: Substation - Wikipedia
Summary
A Substation is a node in the electrical generation, Electric Power Transmission, and Electric Power Distribution system. Substations transform voltage (high to low or reverse), switch circuits, and protect the system from faults. Between generator and consumer, power may flow through several substations at different voltage levels. There are ~55,000 substations in the US alone.
Key types
| Type | Function |
|---|---|
| Transmission substation | Connects two or more transmission lines. May include transformers between voltage levels, voltage control devices (capacitors, SVCs), phase-shifting transformers. |
| Distribution substation | Steps down from transmission/subtransmission to medium voltage (2.4–33 kV) for local distribution feeders. Isolates faults between transmission and distribution. |
| Collector substation | Aggregates power from distributed generation (wind farms, solar plants) at ~35 kV and steps up to transmission voltage. Reverse of a distribution substation. |
| Converter substation | Associated with HVDC, traction power, or interconnection of asynchronous networks. Contains power electronics for frequency/AC-DC conversion. |
| Switching station | Operates at a single voltage level without transformers. Used for circuit switching, fault isolation, backup. |
Key components
- Transformers: voltage conversion (the core function)
- Circuit breakers: interrupt fault currents automatically
- Disconnect switches: provide isolation for maintenance (cannot interrupt load current)
- Busbars: conductors connecting equipment within the station
- Surge arrestors: protect against lightning and switching surges
- SCADA: remote supervisory control — substations are generally unattended
Design considerations
- Reliability vs. cost tradeoffs in bus arrangements: ring bus, double bus, or “breaker and a half” configurations for redundancy.
- Modern substations may implement IEC 61850 standard for communication.
- Can be outdoor, indoor, underground, or gas-insulated (GIS) for urban settings.
Relevance to flexibility
Substations are the physical nodes where voltage transformation and switching happen — the infrastructure through which all grid flexibility flows. Distribution substations are particularly important for flexibility because they are the boundary between the transmission grid (TSO domain) and the distribution grid (DSO domain). As DER penetration grows, distribution substations become points where bidirectional power flows must be managed, congestion monitored, and flexibility services coordinated. Collector substations for wind/solar are also relevant — they are where variable generation enters the grid.