A battery energy storage system is often pictured as containers of cells — but from the grid's point of view, a BESS is a power plant that can also consume, and it must connect like one. The interconnection scope is where storage projects succeed or stall.
The connection chain
- PCS (Power Conversion System). Bidirectional inverters that convert the battery's DC to grid-frequency AC and back, and set how the system behaves electrically.
- Step-up transformer. PCS output at low voltage steps up to the connection voltage — 20 kV, 63 kV or higher.
- Switchgear and protection. Breakers, disconnectors and relays coordinated with the utility's own protection.
- Metering and SCADA. Revenue-grade metering at the point of connection, and dispatch integration with the grid operator.
Grid code: the real gatekeeper
Every jurisdiction's grid code specifies how a connected BESS must behave: staying connected through voltage dips (ride-through), responding to frequency deviations, limiting harmonics, and following operator dispatch. Compliance is demonstrated through studies at design stage and tests at commissioning.
| Scale | Typical connection | Interconnection scope |
|---|---|---|
| Cabinet / C&I | LV or 20 kV | PCS, LV switchboard, metering |
| Container / distribution | 20-63 kV | Step-up transformer, MV switchgear, protection, SCADA |
| Utility-scale farm | 63-230 kV | Dedicated substation bay, grid studies, compliance testing |
Below the PCS, a BESS project is a battery project. Above the PCS, it's a substation project — and it should be engineered by people who build substations.
Powerst delivers BESS from cabinet to container scale together with the interconnection scope — transformer, switchgear, protection and SCADA — as one integrated package.
It depends on size: commercial systems at LV or 20 kV, container-scale at 20-63 kV through a step-up transformer, and utility-scale farms at 63 kV and above through a dedicated substation bay.
The Power Conversion System — the bidirectional inverter stage that converts battery DC to grid AC and back. It defines the system's electrical behavior.
Utility-scale systems usually do — either a dedicated bay in an existing substation or a new step-up substation. Smaller systems connect through MV switchgear and a transformer.
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