Micro-grid adaptive relaying

A method changing protection settings groups for relays in a micro-grid between a grid-connected settings group suitable for higher fault currents and a more stable frequency and voltage when the micro-grid is electrically coupled to a utility grid and an islanded settings group suitable for lower fault currents and a less stable frequency and voltage when the micro-grid is disconnected from the utility grid, said method comprising:

• sending a signal from a controller to a load relay that controls the position of a load circuit breaker that connects and disconnects a load to and from the micro-grid that instructs the load relay to change from the islanded settings group to the grid-connected settings group;
• causing a switch relay associated with a micro-grid disconnect switch that disconnects the micro-grid from the utility grid to close the disconnect switch and connect the micro-grid to the utility grid after the load relay has changed its settings group;
• detecting that the switch relay has closed the disconnect switch in a power source relay in the micro-grid that controls a power source circuit breaker that connects and disconnects at least one power source to and from the micro-grid;
• and
• causing the power source relay to change from the islanded settings group to the grid-connected settings group in response to detecting that the disconnect switch is closed.

A method for changing protection settings groups for relays in a micro-grid between a grid-connected settings group suitable for higher fault currents and a more stable frequency and voltage when the micro-grid is electrically coupled to a utility grid and an islanded settings group suitable for lower fault currents and a less stable frequency and voltage when the micro-grid is disconnected from the utility grid, said method comprising:

• changing a first relay in the micro-grid from the grid-connected settings group to the islanded settings group before the micro-grid is disconnected from the utility grid;
• disconnecting the micro-grid from the utility grid;
• and
• changing a second relay in the micro-grid from the grid-connected settings group to the islanded settings group after the micro-grid is disconnected from the utility grid.