Electrical partial discharge pulse marker discrimination

• US 8,008,925 B2
• Filed: 07/16/2008
• Issued: 08/30/2011
• Est. Priority Date: 07/16/2008
• Status: Active Grant

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Siemens Energy Incorporated (Siemens AG)
• Inventors: Twerdochlib, Michael
• Primary Examiner(s): He; Amy
• Application Number:
  US12/174,292
• Publication Number:
  US 20100013494A1
• Time in Patent Office: 1,140 Days
• Field of Search: 324/536, 324/551
• US Class Current: 324/536
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/346 Testing of armature or field windings

Abstract

A marker pulse discriminator monitor that enables filtering of partial discharge pulses for monitoring the condition of a generator in a power plant system. The monitor detects partial discharge pulses emanating from the generator and includes a plurality of first modules connected to respective isophase buses adjacent to the generator. Each of the first modules generate a marker pulse in response to a partial discharge pulse. The monitor also includes an analyzer unit connected to the isophase buses adjacent to a step-up transformer. The analyzer unit receives each partial discharge pulse and each marker pulse and determines a differential value corresponding to a difference between a time of arrival of a partial discharge pulse and a time of arrival of a corresponding marker pulse to identify partial discharge pulses originating at the generator and to identify the isophase bus associated with the corresponding partial discharge pulse.

Claims

1. A method for detecting partial discharge pulses emanating from a generator on a conductor, the method comprising the steps of:

detecting a partial discharge pulse on the conductor at a first module;

detecting the partial discharge pulse on the conductor at a second module;

generating a marker pulse on the conductor at the first module in response to the detection of the partial discharge pulse at the first module;

detecting the marker pulse on the conductor at the second module;

determining a differential value corresponding to a difference between a time of arrival of the partial discharge pulse at the second module and a time of arrival of the marker pulse at the second module; and

using the differential value to identify whether the partial discharge pulse originated at the generator.

2. The method of claim 1, wherein the marker pulse is generated by the first module a predetermined time period after the partial discharge pulse is detected at the first module.

3. The method of claim 2, wherein the second module identifies a partial discharge pulse originating at the generator by identifying a differential value corresponding to the predetermined time period.

4. The method of claim 1, wherein the first module is located adjacent to the generator.

5. The method of claim 1, wherein the second module is located adjacent to a step-up transformer.

6. The method of claim 5, wherein the first and second modules are located between the generator and the step-up transformer, and including identifying a partial discharge pulse originating from the step-up transformer comprising:

detecting the partial discharge pulse at the second module before detecting the partial discharge pulse at the first module;

identifying a differential value equal to the sum of the predetermined time period and approximately twice the time period required for a pulse to travel between the first and second modules.

7. The method of claim 1, wherein the conductor comprises first, second and third isophase buses, each isophase bus connected to a respective first module, and the step of generating a marker pulse on the conductor comprises providing a unique time delay for each first module to produce a marker pulse after a partial discharge pulse is detected on a respective isophase bus.

8. The method of claim 7, including an analyzer unit comprising the second module and connected to all of the isophase buses, and the analyzer unit identifies the isophase bus associated with a partial discharge pulse based on a differential value corresponding to at least one unique time delay provided by at least one of the first modules.

9. In a system comprising an electrical generator connected to a step-up transformer by a conductor comprising a plurality of isophase buses, and a monitor comprising a plurality of first modules connected to respective isophase buses adjacent to the generator and an analyzer unit including one or more second modules connected to the isophase buses adjacent to the step-up transformer, a method for detecting partial discharge pulses emanating from the generator, the method comprising the steps of;

detecting one or more partial discharge pulses at respective first modules;

detecting the one or more partial discharge pulses at the analyzer unit;

generating a marker pulse for each of the one or more partial discharge pulses at the respective first modules;

detecting each marker pulse at the analyzer unit;

for each marker pulse, determining a differential value corresponding to a difference between a time of arrival of the partial discharge pulse at the analyzer unit and a time of arrival of a corresponding marker pulse at the analyzer unit; and

using each differential value to identify whether a corresponding partial discharge pulse originated at the generator and to identify the isophase bus associated with the corresponding partial discharge pulse.

10. The method of claim 9, wherein each of the marker pulses is generated a predetermined time period after a partial discharge pulse is detected on a respective isophase bus, and each first module has a unique predetermined time period associated with it different from the predetermined time period of any other first module.

11. The method of claim 9, wherein partial discharge pulses originating at the generator are identified by a first predefined set of differential values, and discharge pulses originating from the step-up transformer are defined by a second predefined set of differential values.

12. The method of claim 9, wherein analog pulse signals from all isophase buses are combined into a single analog signal, where the single analog signal comprises five-thirds electrical cycles of data.

13. The method of claim 12, wherein the single analog signal is digitized for analysis by the analyzer.

14. The method of claim 9, wherein analog pulse signals from all isophase buses are analyzed in real time based on an elapsed time between arrival of a partial discharge pulse and arrival of a marker pulse.

15. The method of claim 9, wherein the amplitude of each marker pulse is used to analyze the amplitude of a corresponding partial discharge pulse.

16. In combination with a system comprising an electrical generator connected to a step-up transformer by a conductor comprising a plurality of isophase buses, a monitor for detecting partial discharge pulses emanating from the generator, the monitor comprising:

a plurality of first modules connected to respective isophase buses adjacent to the generator, each of the first modules generating a marker pulse in response to a partial discharge pulse;

an analyzer unit including one or more second modules connected to the isophase buses adjacent to the step-up transformer; and

wherein the analyzer unit receives each partial discharge pulse and each marker pulse and determines a differential value corresponding to a difference between a time of arrival of a partial discharge pulse and a time of arrival of a corresponding marker pulse to identify a partial discharge pulse originating at the generator and to identify the isophase bus associated with the corresponding partial discharge pulse.

17. The monitor of claim 16, wherein the analyzer unit is connected to all of the isophase buses and combines the analog pulse signals from all isophase buses into a single analog signal.

18. The monitor of claim 16, wherein the analyzer unit comprises a second module associated with each of the isophase buses, each of the second modules performing a data capture and analysis operation for detecting partial discharge pulses on a respective isophase bus.