Method for detecting a fault condition in an electrical machine

• US 10,088,506 B2
• Filed: 10/03/2013
• Issued: 10/02/2018
• Est. Priority Date: 11/01/2012
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Rodriguez, Pedro, Pinto, Cajetan, Orman, Maciej, Orkisz, Michal, Ahrend, Ulf, Disselnkotter, Rolf, Rzeszucinski, Pawel, Ottewill, James
• Primary Examiner(s): Kundu, Sujoy
• Assistant Examiner(s): Sun, Xiuquin
• Application Number:
  US14/440,271
• Publication Number:
  US 20150276823A1
• Time in Patent Office: 1,825 Days
• Field of Search: 702 75
• CPC Class Codes: G01R 19/02 Measuring effective values, i.e. root-mean-square values
• CPC Class Codes: G01R 23/00 Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
• CPC Class Codes: G01R 31/34 Testing dynamo-electric machines
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/346 Testing of armature or field windings

Abstract

A method for identifying a fault condition in an electrical machine in which at least a stator or a rotor has parallel winding branches is disclosed. A measurement is carried out for obtaining a set of circulating current values between two parallel winding branches of which each winding branch includes a single coil. A frequency analysis is applied on the set of circulating current values to obtain at least one frequency component. A fault condition of the electrical machine is determined on the basis of the at least one frequency component.

Claims

1. A method for identifying a fault condition in an electrical machine in which at least a stator or a rotor has electrically parallel winding branches, the method comprising the steps of:

taking a first measurement, via at least one current sensor implemented in the electrical machine, for obtaining a first set of circulating current values between two electrically parallel winding branches, wherein each winding branch comprises a single coil;

applying, via a processor, a frequency analysis on the first set of circulating current values to obtain at least one frequency component;

identifying, via the processor, on the basis of the at least one frequency component, a type of fault condition of the electrical machine;

wherein the method comprises at least one of the following steps performed via the processor;

determining, on the basis that the at least one frequency component has a value (2k+1)f_s±

f_r, wherein k=(2, 3, . . . ), f_s=supply frequency and f_r=rotational frequency of the electrical machine, that the machine suffers from dynamic eccentricity;

determining, on the basis that the at least one frequency component has a value kf_s, wherein k=(2, 3, . . . ) and f_s=supply frequency, that the machine suffers from static eccentricity; and

determining, on the basis that the at least one frequency component has a value (2k+1)f_s, wherein k=(1, 2, 3, . . . ) and f_s=supply frequency, that the machine suffers from inter-turn short circuit in the stator;

performing maintenance on the electrical machine when the type of fault condition is identified.

2. The method according to claim 1, wherein the electrical machine is a synchronous electrical motor or generator.

3. The method according to claim 1, wherein the at least one current sensor comprises two current sensors for obtaining branch current signals from the two electrically parallel winding branches, and wherein the first set of circulating current values is calculated from the branch current signals using an operational amplifier of the processor or using a numerical subtraction after the branch current signals have been converted into a digital domain.

4. The method according to claim 1, wherein the at least one current sensor comprises a differential current sensor.

5. The method according to claim 4, wherein the first measurement is carried out between two opposite winding branches in circumferential direction of the stator, the at least one current sensor being arranged at the two opposite winding branches in the circumferential direction of the stator.

6. The method according to claim 1, wherein the method comprises the step of:

carrying out a second measurement corresponding to the first measurement, the two electrically parallel winding branches in the second measurement being different from those in the first measurement.

7. The method according to claim 6, wherein the two electrically parallel winding branches in the second measurement are in a different electrical phase than those in the first measurement.

8. The method of claim 6, further comprising the step of applying a space-frequency analysis, via the processor, to the first measurement and second measurement to extract spatial information to locate a position of the fault condition.

9. The method according to claim 1, wherein the method comprises the step of:

carrying out a measurement corresponding to the first measurement for winding branches in each electrical phase of the electrical machine.

10. The method according to claim 1, wherein a fault condition of the electrical machine is determined on the basis of more than one frequency component.

11. The method according to claim 1, wherein the method comprises the step of:

comparing an amplitude of the circulating current at the frequency component with a predetermined threshold value.

12. The method of claim 11, further comprising the step of using a computer simulation to obtain the predetermined threshold value, wherein different types of fault conditions are simulated in a simulation model corresponding to the electrical machine.

13. The method according to claim 1, wherein the method comprises the step of:

comparing a relative amplitude of the circulating current at the frequency component with a predetermined threshold value, wherein the relative amplitude is determined by an algorithm comprising a root mean square of the circulating current at the frequency component.

14. The method according to claim 1, wherein the first measurement is carried out during a transient operation of the electrical machine.

15. The method of claim 1, wherein the at least one current sensor is integrated into the two electrically parallel winding branches of the electrical machine.

16. The method of claim 1, further comprising the step of locating a position of the fault condition within the electrical machine when the type of fault condition is identified;

wherein the step of performing maintenance comprises performing maintenance on the electrical machine at the position of the fault condition.

17. A method for identifying a fault condition in an electrical machine in which at least a stator or a rotor has electrically parallel winding branches, the method comprising the steps of:

taking a first measurement, via at least one current sensor implemented in the electrical machine, for obtaining a first set of circulating current values between two electrically parallel winding branches, wherein each winding branch comprises a single coil;

applying, via a processor, a frequency analysis on the first set of circulating current values to obtain at least one frequency component;

comparing, via the processor, a relative amplitude of the circulating current at the frequency component with a predetermined threshold value, wherein the relative amplitude is determined by an algorithm comprising a factor

18. A method for identifying a fault condition in an electrical machine in which at least a stator or a rotor has electrically parallel winding branches, the method comprising the steps of:

taking a first measurement, via at least one current sensor implemented in the electrical machine, for obtaining a first set of circulating current values between two electrically parallel winding branches, wherein each winding branch comprises a single coil;

applying, via a processor, a frequency analysis on the first set of circulating current values to obtain at least one frequency component;

comparing, via the processor, a relative amplitude of the circulating current at the frequency component with a predetermined threshold value, wherein the relative amplitude is determined by an algorithm