Micro-grid adaptive relaying

Patent metadata

Field	Value
Publication number	US-10593497-B2
Application number	US-201816217078-A
Country	US
Kind code	B2
Filing date	Dec 12, 2018
Priority date	Jan 29, 2018
Publication date	Mar 17, 2020
Grant date	Mar 17, 2020

Abstract

A system and method for changing protection settings groups for relays in a micro-grid between a grid-connected settings group and an islanded settings group. The method changes a power source relay from the grid-connected settings group to the islanded settings group before the micro-grid is disconnected from the utility grid, disconnects the micro-grid from the utility grid, and then changes a load relay from the grid-connected settings group to the islanded settings group after the micro-grid is disconnected from the utility grid. The method also changes the load relay from the islanded settings group to the grid-connected settings group before the micro-grid is connected to the utility grid, connects the micro-grid to the utility grid, and then changes the power source relay from the islanded settings group to the grid-connected settings group after the micro-grid is connected to the utility grid.

First claim

What is claimed is:

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.

Assignees

• S & C Electric Co

Inventors

• Pabst Paul Michael
• Higginson Michael James

Classifications

• H01H71/74 Primary

  Means for adjusting the conditions under which the device will function to provide protection · CPC title

• H02J3/38

  Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel · CPC title

• H01H47/002 Primary

  Monitoring or fail-safe circuits · CPC title

• H02H7/28

  for meshed systems · CPC title

• H02J3/388

  Arrangements for the handling of islanding, e.g. for disconnection or for avoiding the disconnection of power · CPC title