Micro-grid adaptive relaying

1. 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:

sending a signal to a controller from a switch relay associated with a micro-grid disconnect switch that disconnects the micro-grid from the utility grid telling the controller that the switch relay is about to open the disconnect switch and disconnect the micro-grid from the utility grid;

sending a signal from the controller to 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 that instructs the power source relay to change from the grid-connected settings group to the islanded settings group before the switch relay opens the disconnect switch;

causing the switch relay to open the disconnect switch to disconnect the micro-grid from the utility grid;

detecting that the switch relay has opened the disconnect switch in a load relay in the micro-grid that controls the position of a load circuit breaker that connects and disconnects a load to and from the micro-grid; and

causing the load relay to change from the grid-connected settings group to the islanded settings group in response to detecting that the disconnect switch is open.

2. The method according to claim 1 wherein sending a signal to the controller from the switch relay is in response to detecting a fault current in the utility grid.

3. The method according to claim 1 wherein detecting that the switch relay has opened the disconnect switch includes receiving a disconnect signal from the switch relay by the load relay on a high speed control line.

4. The method according to claim 3 wherein the high speed control line is a fiber optic line.

5. The method according to claim 1 wherein the at least one power source is a plurality of distributed power sources.

6. The method according to claim 1 wherein sending a signal from the controller to the power source relay includes sending the signal on a relatively slow supervisory control and data acquisition (SCADA) line.

7. 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.

8. The method according to claim 7 wherein detecting that the switch relay has closed the disconnect switch includes receiving a connect signal from the switch relay by the load relay on a high speed control line.

9. The method according to claim 8 wherein the high speed control line is a fiber optic line.

10. The method according to claim 7 wherein the at least one power source is a plurality of distributed power sources.

11. The method according to claim 7 wherein sending a signal from the controller to the power source relay includes sending the signal on a relatively slow supervisory control and data acquisition (SCADA) line.

12. 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.

13. The method according to claim 12 further comprising changing the second relay from the islanded settings group to the grid-connected settings group before the micro-grid is connected to the utility grid, connecting the micro-grid to the utility grid, and changing the first relay from the islanded settings group to the grid-connected settings group after the micro-grid is connected to the utility grid.

14. The method according to claim 13 wherein the first relay is a power source relay that controls a power source circuit breaker that connects and disconnects at least one power source to and from the micro-grid, and the second relay is a load relay that controls the position of a load circuit breaker that connects and disconnects a load to and from the micro-grid.

15. The method according to claim 14 wherein the at least one power source is a plurality of distributed power sources.