System and method for detecting ground fault in a dc system

Patent metadata

Field	Value
Publication number	US-10191101-B2
Application number	US-201414556744-A
Country	US
Kind code	B2
Filing date	Dec 1, 2014
Priority date	Dec 1, 2014
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

A ground fault detection system for locating a ground fault in a direct current (DC) power transfer system is provided. The system includes a ground fault detection component and a current sensor. The ground fault detection component includes a first switch and a first resistive element electrically coupled to each other in a series configuration. The ground fault detection component also includes a second switch and a second resistive element electrically coupled to each other in a series configuration. Furthermore, the current sensor is operatively coupled to a load and is configured to measure a fault current at the load upon switching at least one of the first switch or the second switch to a conducting state.

First claim

The invention claimed is:

1. A ground fault detection system for locating a ground fault in a direct current (DC) power transfer system comprising:
a ground fault detection component comprising:
a first switch and a second switch;
a first resistive element and a second resistive element;
wherein, the first switch is electrically coupled to the first resistive element and the second switch is electrically coupled to the second resistive element in a series configuration respectively,
a current sensor operatively coupled to a load and configured to measure a fault current at the load upon switching at least one of the first switch or the second switch to a conducting state; and
a DC grounding component coupled to the ground fault detection component in a parallel configuration between a positive rail and a negative rail of a first DC bus, wherein the DC grounding component is configured to provide a balanced ground reference voltage at a neutral point;
wherein the DC grounding component comprises a third resistive element and a fourth resistive element, a first capacitive element and a second capacitive element, or a combination thereof for providing the balanced ground reference voltage.

2. The ground fault detection system of claim 1 , wherein the first switch and the second switch comprises a mechanical switch or a semiconductor switch.

3. The ground fault detection system of claim 1 , wherein a grounding impedance of the DC grounding component is higher than a detector impedance of the ground fault detection component.

4. The ground fault detection system of claim 1 , wherein the first switch is switched to a conducting state upon occurrence of the ground fault on a negative rail of a DC bus in the DC power transfer system and the second switch is switched upon occurrence of the ground fault on a positive rail of the DC bus in the DC power transfer system.

5. The ground fault detection system of claim 1 , wherein the first switch and the second switch are configured to switch continuously based on a predefined switching pattern to locate the ground fault in the DC power transfer system.

6. A direct current (DC) power transfer system comprising:
a power source configured to provide DC power,
a DC bus configured to transmit DC power from the power source;
at least one load operatively coupled to the DC bus;
a ground fault detection system operatively coupled to the DC bus comprising:
a ground fault detection component comprising:
a first switch and a second switch;
a first resistive element and a second resistive element;
wherein, the first switch is electrically coupled to the first resistive element and the second switch is electrically coupled to the second resistive element in a series configuration respectively;
at least one current sensor operatively coupled to the at least one load and configured to measure a fault current at the at least one load upon switching at least one of the first switch or the second switch to a conducting state; and
a DC grounding component coupled to the ground fault detection component in a parallel configuration between a positive rail and a negative rail of the DC bus, wherein the DC grounding component is configured to provide a balanced ground reference voltage at a neutral point;
wherein the DC grounding component comprises a third resistive element and a fourth resistive element, a first capacitive element and a second capacitive element, or a combination thereof for providing the balanced ground reference voltage.

7. The DC power transfer system of claim 6 , wherein the first switch is switched to a conducting state upon occurrence of the ground fault on a negative rail of the DC bus in the DC power transfer system and the second switch is switched upon occurrence of the ground fault on a positive rail of the DC bus in the DC power transfer system.

8. The DC power transfer system of claim 6 , wherein a grounding impedance of the DC grounding component is higher than a detector impedance of the ground fault detection component.

9. The DC power transfer system of claim 6 , wherein the first switch and the second switch are configured to switch continuously based on a predefined switching pattern to locate the ground fault in the DC power transfer system.

10. The DC power transfer system of claim 6 , wherein at least one load comprises an electric motor, an energy storage element or a combination thereof.

11. The DC power transfer system of claim 6 , wherein the current sensor comprises a current transformer.

12. A method comprising:
identifying a ground fault in a DC power transfer system;
switching at least one of a first switch and a second switch in a ground fault detection component upon identification of the ground fault in the DC power transfer system;
passing a fault current through at least one of a first resistive element and a second resistive element upon switching the first switch or the second switch respectively to increase a magnitude of the fault current;
measuring the fault current at one or more loads upon increasing the magnitude of the fault current using a current sensor operatively coupled to each load; and

detecting a location of the ground fault based on a measured fault current at each load;
wherein a balanced ground reference voltage is provided to the ground fault detection component at a neutral point by a DC grounding component coupled to the ground fault detection component in a parallel configuration between a positive rail and a negative rail of a first DC bus; and
wherein the DC grounding component comprises a third resistive element and a fourth resistive element, a first capacitive element and a second capacitive element, or a combination thereof for providing the balanced ground reference voltage.

13. The method of claim 12 , further comprising switching the first switch and the second switch continuously based on a predefined switching pattern.

14. The method of claim 12 , wherein switching at least one of the first switch or the second switch comprises switching the first switch upon occurrence of the ground fault on a negative rail of a DC bus in the DC power transfer system and switching the second switch upon occurrence of the ground fault on a positive rail of the DC bus in the DC power transfer system.

15. The method of claim 12 , further comprising switching at least one of the first switch or the second switch at a fixed frequency to generate an alternating ground current or a direct ground current and measuring the alternating ground current or the direct ground current using a current transformer to detect the location of the ground fault.

16. The method of claim 12 , further comprising isolating the load corresponding to a detected location of the ground fault from a DC bus in the DC power transfer system.

Assignees

• Gen Electric

Inventors

• Dong Dong
• Pan Yan
• Lai Rixin

Classifications

• G01R31/008 Primary

  on air- or spacecraft, railway rolling stock or sea-going vessels · CPC title

• G01R31/085

  in power transmission or distribution lines, e.g. overhead · CPC title

• G01R31/08 Primary

  Locating faults in cables, transmission lines, or networks · CPC title

• G01R31/025 Primary

  Physics · mapped topic

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title