This application is suited for configuration in which generation is utilized onsite and disconnected from SCE’s grid. Momentary Parallel Operations option within Rule 21 allows for generation to connect in parallel with the grid for less than one second. After connecting, the microgrid would separate from the grid to provide backup service to accommodate customer needs.
All technologies or combination of technologies are qualified for this option, but this system must have adequate equipment and/or controls to separate the microgrid from SCE’s grid when the grid is unavailable (e.g., a power outage) or when disconnection is desired. This method of operation can use a momentary closed transition back to and from the grid. A typical simplified diagram is depicted on Figure 4.
FIGURE 4: Behind-The-Meter (BTM) Microgrid Application with Momentary Parallel Backup Generation
Legal Requirements:
- Must submit a Rule 21 Interconnection Application Indicating Momentary Operation
- SCE provide approval of requested operating mode
Operating Rules:
Normal Operating Rules:
- Operates isolated from the grid. BTM Microgrid parallels with the grid on a momentary basis to transfer between microgrid operation and normal grid connected operation.
Microgrid Operation:
- Separate (disconnect) the BTM microgrid (customer needs and generation) from the SCE grid by opening a device designed for that purpose such a breaker or a disconnect device (typically via an ATS)
- The control systems and/or equipment may parallel momentarily with the SCE grid
- Transition to BTM microgrid operation shall can be momentary closed transition where the SCE grid system and the microgrid generation are in parallel for less than one (1) second
Return to Normal Operation:
- When SCE grid returns to normal, customer needs can be transferred to the SCE grid via a momentary closed transition.
Rule 21 Interconnection Rates and Rules:
- Rule 21 application operating under the Momentary Operation Option
- Customer to submit Rule 21 interconnection request to SCE. Visit www.sce.com/gridinterconnection for more information.
- Acknowledgement from SCE on adequacy of transfer is scheme is required
Cost Responsibility in Various Microgrid Ownership/Operational Models:
Customer liable for testing, operating and maintaining all equipment necessary to maintain a safe operation of the Generating Facility under normal operation or under a Microgrid operations
Application Checklist:
- Submit an Interconnection Application with the following requirements:
a. Technical information related to the generator and transformation
b. Single Line Diagram
c. Sequence of operations
- SCE provide approval of requested operating mode As-built Single Line Diagram
- Received Permission To Operate (PTO) from SCE