Ground Fault Detection Circuit

• US 20140239967A1
• Filed: 02/21/2014
• Published: 08/28/2014
• Est. Priority Date: 02/22/2013
• Status: Active Grant

• Current Assignee: Nidec Control Techniques Limited (Nidec Corporation)
• Original Assignee: Control Techniques Limited (Nidec Corporation)
• Inventors: Towers, Mark, Davies, Dylan Wyn
• Granted Patent: US 9,541,593 B2
• Time in Patent Office: Days
• US Class Current: 324/509
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G01R 31/74 Testing of fuses
• CPC Class Codes: H02S 40/32 comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
• CPC Class Codes: H02S 50/10 Testing of PV devices, e.g. of PV modules or single PV cells testing of semiconductor devices during manufacturing H01L22/00
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A ground fault detection circuit comprising a fuse and a fuse detect circuit. The fuse and the fuse detect circuit are arranged to be coupled in parallel between a reference point and a second point of a monitored circuit for which ground faults are to be detected. The fuse detect circuit is further arranged to detect a fuse break indicative of a ground fault condition and disable at least a portion of the monitored circuit.

Claims

1. A ground fault detection circuit comprising:

a fuse;

a fuse detect circuit;

the fuse and the fuse detect circuit being arranged to be coupled in parallel between a reference point and a second point of a monitored circuit for which ground faults are to be detected;

wherein

the fuse detect circuit is further arranged to;

detect a fuse break indicative of a ground fault condition; and

disable at least a portion of the monitored circuit.

2. The ground fault detection circuit of claim 1 wherein a fuse break indicative of a ground fault is detectable by detecting at least a pre-determined voltage across the fuse or a signal indicative of current passing through the fuse, and optionally wherein the pre-determined voltage across the fuse is caused by the breaking of the fuse due to at least a pre-determined current flowing therethrough.

3. The ground fault detection circuit of claim 1 wherein the fuse detect circuit comprises a voltage monitor arranged to be coupled in parallel between the reference point and the second point of a monitored circuit for which ground faults are to be detected.

4. The ground fault detection circuit of claim 1 wherein the fuse detect circuit comprises at least two voltage monitors arranged to be coupled in parallel between the reference point and the second point of a monitored circuit for which ground faults are to be detected.

5. The ground fault detection circuit of claim 3 further comprising a potential divider coupled between each voltage monitor and the fuse, and optionally wherein the potential divider comprises resistors of a value between 100 k ohms and 100 M ohms.

6. The ground fault detection circuit of claim 1 wherein the fuse is rated between 1 A and 5 A.

7. The ground fault circuit of claim 1 wherein each voltage monitor is a voltage monitoring relay.

8. The ground fault circuit of claim 1 wherein the fuse detect circuit comprises an isolated DC or AC source arranged to inject a current into-the fuse, and optionally wherein the fuse detect circuit further comprises detection means arranged to detect the current that was injected into the fuse and that has passed through the fuse or a signal indicative thereof, and further optionally wherein the detection means of the fuse detect circuit is arranged to detect a current signal waveform, and further optionally wherein the detection means comprises a filter.

9. The ground fault detection circuit of claim 1 wherein the fuse detect circuit is further arranged to indicate a fault condition on an output.

10. The ground fault detection circuit of claim 1 wherein the second point of the monitored circuit is a positive connection or a negative connection.

11. The ground fault circuit of claim 1 wherein the circuit is tolerant to voltages of 600V or more, and optionally wherein the circuit is tolerant to voltages of 1000V or more.

12. The ground fault circuit of claim 1 wherein the reference point is a ground connection.

13. The ground fault circuit of claim 1 wherein the second point is a DC connection or an AC connection.

20. A ground fault detection system comprising:

the circuit of claim 1;

wherein a PV array is the monitored circuit;

and an inverter of the PV array is arranged to be disabled in response to detecting the fuse break indicative of a ground fault condition.

14. A method of detecting a ground fault comprising:

detecting by a fuse detect circuit a fuse break indicative of a ground fault condition;

the fuse and the fuse detect circuit arranged to be coupled in parallel between a reference point and a second point of a monitored circuit; and

disabling at least a portion of the monitored circuit in response to detecting the fuse break condition.

15. The method of claim 14 wherein detecting a fuse break indicative of a ground fault comprises detecting at least a pre-determined voltage across the fuse or a signal indicative of current passing through the fuse, and optionally wherein the pre-determined voltage across the fuse is caused by the breaking of the fuse due to at least a pre-determined current flowing therethrough.

16. The method of claim 14 wherein the fuse detect circuit comprises a voltage monitor arranged to be coupled in parallel between the reference point and the second point of a monitored circuit for which ground faults are to be detected.

17. The method of claim 14 wherein the fuse detect circuit comprises at least two voltage monitors arranged to be coupled in parallel between the reference point and the second point of a monitored circuit for which ground faults are to be detected.

18. The method of claim 14 wherein the fuse detect circuit comprises an isolated DC or AC source arranged to inject a current into-the fuse, and optionally wherein the fuse detect circuit further comprises detection means arranged to detect the current that was injected into the fuse and that has passed through the fuse or a signal indicative thereof, and further optionally wherein the detection means of the fuse detect circuit is arranged to detect a current signal waveform, and further optionally wherein the detection means comprises a filter.

19. The method of claim 14 wherein the fuse detect circuit is further arranged to indicate a fault condition on an output.