High impedance fault detector

1. An electrical grid system comprising;

a phase conductor;

a neutral conductor;

a neutral-to-ground conductor segmenting the neutral conductor and configured to conduct current flow between the neutral conductor and the ground; and

a fault detection sensor including:

a current sensor configured to sense current flowing along the neutral-to-ground conductor; and

a controller having an electronic processor, the controller configured to:

receive signals indicative of the current flowing through the neutral-to-ground conductor form the current sensor;

determine a noise attribute of the neutral-to-ground conductor based on the received signals; and

output an occurrence of a fault in the electrical grid system when the noise attribute of the neutral-to-ground conductor exceeds a threshold.

2. The electrical grid system of claim 1 , wherein the controller is further configured to monitor the received signals for the occurrence of at least one of a first type event and a second type event associated with the current flowing through the neutral-to-ground conductor.

3. The electrical grid system of claim 2 , wherein the controller is further configured to:

monitor the received signals for the occurrence of the first type event by executing a first fault detection algorithm; and

monitor the received signals for the occurrence of the second type event by executing a second fault detection algorithm.

4. The electrical grid system of claim 3 , wherein the controller is further configured to execute the first fault detection algorithm and the second fault detection algorithm simultaneously.

5. The electrical grid system of claim 2 , wherein the first type event includes a reversal in a direction of current flow along the neutral-to-ground conductor from a normal direction to a reverse direction.

6. The electrical grid system of claim 5 , wherein the controller is further configured to:

receive, from a second current sensor configured to sense a reference current flowing through the phase conductor, second signals indicative of the current flowing through the phase conductor; and

determine the direction of current flow along the neutral-to-ground conductor based on the received second signals.

7. The electrical grid system of claim 5 , wherein the controller is further configured to determine that the fault has occurred when an amount of time for which the current flowing through the neutral-to-ground conductor flows in the reverse direction exceeds a first predetermined amount of time.

8. The electrical system of claim 5 , wherein the first type event further includes an increase in magnitude of the current flowing through the neutral-to-ground conductor above a predetermined normal current threshold, wherein the controller is further configured to:

determine whether the magnitude of current flowing through the neutral-to-ground conductor has increased above the predetermined normal current threshold in an amount of time that is less than a second predetermined amount of time.

9. The electrical grid system of claim 2 , wherein the second type event is the occurrence of significant random noise on the neutral-to-ground conductor indicative of an arcing fault.

10. A method for determining whether a fault has occurred in an electrical grid system comprising a phase conductor, a neutral conductor, a neutral-to-ground conductor segmenting the neutral conductor and configured to conduct current flow between the neutral conductor and ground, and a fault detection sensor including a current sensor and a controller having an electronic processor, the method comprising:

sensing, by the current sensor, current flowing along the neutral-to-ground conductor;

receiving, by the controller, signals indicative of the current flowing through the neutral-to-ground conductor from the current sensor;

determining, by the controller, a noise attribute of the neutral-to-ground conductor based on the received signals; and

reporting, by the controller, that a fault has occurred in the electrical grid system when the noise attribute of the neutral-to-ground conductor exceeds a threshold.

11. The method of claim 10 , further comprising monitoring, by the controller, the received signals for the occurrence of at least one of a first type event and a second type event associated with the current flowing through the neutral-to-ground conductor.

12. The method of claim 11 , further comprising:

monitoring, by the controller, the received signals for the occurrence of the first type event by executing a first fault detection algorithm; and

monitoring, by the controller, the received signals for the occurrence of the second type event by executing a second fault detection algorithm.

13. The method of claim 12 , further comprising:

executing, by the controller, the first fault detection algorithm and the second fault detection algorithm simultaneously.

14. The method of claim 11 , wherein the first type event includes a reversal in a direction of current flow along the neutral-to-ground conductor from a normal direction to a reverse direction.

15. The method of claim 14 , further comprising:

receiving, by the controller, from a second current sensor configured to sense a reference current flowing through the phase conductor, second signals indicative of the current flowing through the phase conductor; and

determining, by the controller, the direction of current flow along the neutral-to-ground based on the received second signals.

16. The method of claim 14 , further comprising:

determining, by the controller, that the fault has occurred when an amount of time for which the current flowing through the neutral-to-ground conductor flows in the reverse direction exceeds a first predetermined amount of time.

17. The method of claim 14 , wherein the first type event further includes an increase in magnitude of the current flowing through the neutral-to-ground conductor above a predetermined normal current threshold, further comprising:

determining, by the controller, whether the magnitude of current flowing through the neutral-to-ground conductor has increased above the predetermined normal current threshold in less than a second predetermined amount of time.

18. The method of claim 11 , wherein the second type event is the occurrence of significant random noise on the neutral-to-ground conductor indicative of an arcing fault.

19. A fault detection sensor comprising;

a current sensor configured to sense current flowing along a neutral-to-ground conductor included in an electrical grid system, the neutral-to-ground conductor segmenting a neutral line of the electrical grid system; and

a controller having an electronic processor, the controller configured to:

receive signals indicative of the current flowing through the neutral-to-ground conductor form the current sensor;

determine a noise attribute of the neutral-to-ground conductor based on the received signals; and

output an occurrence of a fault in the electrical grid system when the noise attribute of the neutral-to-ground conductor exceeds a threshold.

20. The fault detection sensor of claim 19 , wherein the controller is further configured to monitor the received signals for the occurrence at least one of a first type event and a second type event associated with the current flowing through the neutral-to-ground conductor.

21. The fault detection sensor of claim 20 , wherein the controller is further configured to:

monitor the received signals for the occurrence of the first type event by executing a first fault detection algorithm; and

monitor the received signals for the occurrence of the second type event by executing a second fault detection algorithm.

22. The fault detection sensor of claim 21 , wherein the controller is further configured to execute the first fault detection algorithm and the second fault detection algorithm simultaneously.

23. The fault detection sensor of claim 20 , wherein the first type event includes a reversal in a direction of current flow along the neutral-to-ground conductor from a normal direction to a reverse direction.

24. The fault detection sensor of claim 23 , wherein the controller is further configured to:

receive, from a second current sensor configured to sense a reference current flowing through a phase conductor included in the electrical grid system, second signals indicative of the current flowing through the phase conductor; and

determine the direction of current flow along the neutral-to-ground conductor based on the received second signals.

25. The fault detection sensor of claim 23 , wherein the controller is further configured to determine that the fault has occurred when an amount of time for which the current flowing through the neutral-to-ground conductor flows in the reverse direction exceeds a first predetermined amount of time.

26. The fault detection sensor of claim 23 , wherein the first type event further includes an increase in magnitude of the current flowing through the neutral-to-ground conductor above a predetermined normal current threshold, wherein the controller is further configured to:

determine whether the magnitude of current flowing through the neutral-to-ground conductor has increased above the predetermined normal current threshold in an amount of time that is less than a second predetermined amount of time.

27. The fault detection sensor of claim 20 , wherein the second type event is the occurrence of significant random noise on the neutral-to-ground conductor indicative of an arcing fault.

28. The electrical grid system of claim 1 , wherein the neutral-to-ground conductor is provided on a supply-side of a substation.

29. The method of claim 10 , wherein the neutral-to-ground conductor is provided on a supply-side of a substation.

30. The fault detection sensor of claim 19 , wherein the neutral-to-ground conductor is provided on a supply-side of a substation.