Method and device for detecting a contact point on a shaft of a rotating machine

1. A method for indicating a fault on a machine having a rotating shaft, the method comprising:

providing at least one predetermined ground connection to the shaft;

injecting a test current into the shaft for detection purposes;

determining a grounding state of the shaft using a characteristic of an electrical flow to ground through the at least one ground connection during operation of the machine; and

detecting at least one touching point on the shaft based on a value of the test current and the grounding state;

indicating the fault upon the detection of the at least one touching point.

2. The method as recited in claim 1 , wherein the characteristic includes a current.

3. The method as recited in claim 1 , wherein the at least one predetermined ground connection is formed using at least one grounding module electrically connected to the shaft and having a grounding resistor, and wherein the grounding state is determined by measuring a voltage to ground across the grounding resistor.

4. The method as recited in claim 1 , wherein a current of the electrical flow is evaluated as being positive.

5. The method as recited in claim 1 , wherein the test current is injected into the shaft using the at least one ground connection.

6. The method as recited in claim 5 , wherein the at least one ground connection includes at least one of a grounding brush and a sliding contact forming an electrical contact with the shaft.

7. The method as recited in claim 5 , wherein the at least one grounding connection is formed by a grounding module and the test current is applied to the shaft at least indirectly using the grounding module.

8. The method as recited in claim 1 , further comprising performing a comparison of the value of the test current with a difference between a first total ground current flowing to ground via the at least one ground connection including the test current and a second total ground current flowing to ground via the at least one ground connection without the test current.

9. The method as recited in claim 8 , further comprising determining a conductivity of the touching point from the comparison.

10. The method as recited in claim 1 , wherein the characteristic includes evaluating only a DC component of the electrical flow.

11. The method as recited in claim 10 , further comprising one of averaging over time and filtering a total ground current flowing to ground via the at least one ground connection.

12. The method as recited in claim 1 , wherein the at least one ground connection is formed using at least one grounding module in contact with ground and in contact with the shaft via at least one grounding brush.

13. A device for detecting a touching point on a machine having a rotating shaft, the device comprising:

at least one grounding module having a grounding brush forming a contact with the shaft and at least one grounding resistor; and

a unit having an at least indirect contact to the shaft, the unit configured to inject a defined test current into the shaft and to tap off a voltage across the at least one grounding resistor, wherein the unit is configured to measure and/or evaluate the touching point based on a value of the test current and of a characteristic of a flow of electricity to ground via the at least one grounding resistor.

14. The device as recited in claim 13 , wherein the at least indirect contact to the shaft is formed via the grounding module.

15. The device as recited in claim 13 , wherein the unit and the at least one of the grounding modules form a single part.