Connecting Distributed Generation to the Power Grid
A major determining factor in how the consumer-owned distributed generation is handled by the cooperative is the type and size of the distributed generation. Distributed generation is operated either “isolated” from the electrical power grid or “grid connected”. Isolated operation means the generation is not electrically connected or otherwise tied to the power grid. Grid connected operation means the generation is electrically connected to the power grid and power flows from the generator to the power grid.
When wind turbines and other types of distributed generation are connected into the power grid, they become part of a widespread interconnected network of power lines, protective devices, transformers, substations, and other generators. Each component of the power system has a job to do to provide safe, efficient, and reliable delivery of electric power.
If a consumer wants to interconnect generation to this network, precautions are taken to prevent that generation from causing adverse impacts to the other components and users of the power system.
The electrical distribution system of Oahe Electric is connected to the electrical transmission system of East River Electric Power Cooperative, Inc., which is Oahe Electric’s power and transmission service provider.
The transmission system of East River is, in turn, connected to the High Voltage Integrated Transmission System of the Western Area Power System (WAPA). Any distributed generation connected to the local distribution network must meet the rules and requirements of Oahe Electric, East River, and WAPA. WAPA has the ultimate authority and jurisdiction over any generation connected to the network.
WAPA has developed requirements for interconnecting distributed “consumer-owned” generation to the grid. The major breakpoint for these requirements is the size of the generator.
Generation Under 150 kW at a single site:
- WAPA not directly involved.
- Interconnection agreement with cooperative required.
- Purchased power contract with the local cooperative and its power supplier required.
Generation Over 150 kW up to 5000 kW at a single site:
- WAPA Interconnection Agreement and Transmission Study required.
- Interconnection agreement with the cooperative and/or transmission system required.
- Purchased power contract with the cooperative and/or its power supplier required.
In areas outside of WAPA’s integrated transmission system, other utilities, such as Excel Energy, Otter Tail Power Company, and Montana-Dakota Utilities, operate their own high voltage systems. These utilities have their own rules and regulations, which must be followed.