State Grid Microfilm Relay

What is a microgrid relay?

In smaller microgrids, relays are commonly utilized for control, metering, and protection functions. In larger microgrids, the functionality of the microgrid controls is predominantly performed in one or more centralized controllers.

Are multifunction protective relays a good choice for Microgrid controls?

Multifunction protective relays are an economical choice for microgrid controls because the hardware is commonly required at the point of interface (POI) to the electric power system (EPS) and at each distributed energy resource (DER). The relays at the POI and DER provide mandatory protection and human safety.

Are relay-based controls a cost-effective solution for small Microgrids?

Relay-based controls are a cost-effective solution for smaller microgrids. The additional cost, complexity, and testing of centralized controller-based systems are generally only warranted on large microgrids with more than 10 MW of generation. These large microgrids can include many DERs, loads, and complex topologies.

Are centralized microgrid control capabilities provided by microprocessor-based relays?

X. OPTIONAL CENTRAL CONTROLLER This paper focuses on the microgrid control capabilities provided by microprocessor-based relays. For a variety of reasons, some microgrid owners may add a centralized microgrid controller to augment relay functionality. Relay-based controls are a cost-effective solution for smaller microgrids.

What happens if a POI relay opens a microgrid?

Once the POI relay opens and separates the microgrid, a high-speed load-shedding system response may be required to turn around the voltage and/or frequency. If the microgrid has less generation than load, the system DERs will experience an overburden condition and a frequency decay.

Does 81rf islanding prevent microgrid blackouts?

81RF islanding prevents microgrid blackouts and simultaneously meets interconnect requirements. A25A functionality is performed in multifunction protective relays. Although the relays are commercial and off-the-shelf, the functionalities described in this paper must be designed and tested by skilled engineers.