Cable fault detection

• US 7,725,295 B2
• Filed: 04/30/2009
• Issued: 05/25/2010
• Est. Priority Date: 11/01/2006
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Madwesh, Ajay C., Stoupis, James, Lubkeman, David, Mousavi, Mirrasoul
• Primary Examiner(s): TSAI, CAROL S W
• Application Number:
  US12/433,580
• Publication Number:
  US 20090281740A1
• Time in Patent Office: 390 Days
• Field of Search: 702/59, 702/60, 702/185, 324/532, 324/527, 324/512, 324/536, 324/543, 324/522, 324/539, 361/100, 361/81
• US Class Current: 702/185
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72

Abstract

A cable fault detection component (168) receives input data indicative of a fault in an electrical power system. The component (168) analyzes the input data to determine if the fault is indicative of a temporary or self-clearing cable fault and generates corresponding output data (276). In one implementation, the cable fault detection component (168) is implemented as a software module which operates on a computer (105) of a substation intelligence system (104).

Claims

1. A method of analyzing an anomaly in a cable carrying AC power, the method comprising:

detecting an anomaly with regard to the AC power in the cable;

upon detecting the anomaly, recording data concerning characteristics of the AC power for a predetermined period of time, the data comprising oscillographic data indicative of a time varying signal of cable current;

transmitting the data to an analysis location; and

at the analysis location, analyzing the data to determine whether the anomaly is a cable fault, the analyzing comprising;

performing a Fourier transform of the data; and

using the Fourier transformed data to determine whether the anomaly is a cable fault; and

wherein the Fourier transformed data comprises domain data indicative of a frequency component of the cable current, wherein the frequency domain data includes a peak at the AC power frequency and wherein a magnitude of the peak is indicative of the fundamental cable current.

2. The method of claim 1, wherein the anomaly is an overcurrent burst.

3. The method of claim 2, wherein the predetermined period of time is greater than one cycle of the AC power frequency.

4. The method of claim 1, further comprising receiving a value for the predetermined period of time from a user through a human machine interface.

5. The method of claim 1, wherein the step of detecting the anomaly is performed at a location remote from the analysis location.

6. The method of claim 1, wherein the step of detecting the anomaly is performed by a protective relay.

7. The method of claim 6, wherein the anomaly is an overcurrent burst and the step of detecting the anomaly is performed by an overcurrent protection element of the protective relay.

8. The method of claim 7, wherein the overcurrent protection element is an instantaneous ground time overcurrent protection element.

9. The method of claim 6, wherein the anomaly is a voltage deviation.

10. A method of analyzing an anomaly in a cable carrying AC power, the method comprising:

detecting an anomaly with regard to the AC power in the cable;

upon detecting the anomaly, recording data concerning characteristics of the AC power for a predetermined period of time;

transmitting the data to an analysis location; and

at the analysis location, analyzing the data to determine whether the anomaly is a cable fault, the analyzing comprising;

performing a Fourier transform of the data, the Fourier transformed data comprising data representative of cable current; and

using the Fourier transformed data to determine whether the anomaly is a cable fault, comprising;

determining whether the cable current exceeds a predetermined threshold value so as to comprise an overcurrent event; and

if the cable current exceeds the predetermined threshold value, determining whether a duration of the overcurrent event is less than a threshold fault duration.

11. The method of claim 10, wherein the step of using the Fourier transformed data further comprises determining whether the overcurrent event began at or near a voltage peak.

12. The method of claim 11, wherein the anomaly is determined to be a cable fault if predetermined criteria is met, the predetermined criteria comprising:

the cable current exceeding the predetermined threshold value so as to comprise an overcurrent event, the overcurrent event beginning at or near a voltage peak, and the overcurrent event having a duration that is less than the threshold fault duration.

13. The method of claim 12, wherein the predetermined criteria further comprises the detection of precipitation.

14. The method of claim 10, wherein the step of detecting the anomaly is performed by a protective relay.

15. The method of claim 14, wherein the protective relay comprises a plurality of overcurrent protection elements that are selectable by a user through a human machine interface to perform the detection of the anomaly, and wherein the method further comprises receiving a selection of a first one of the overcurrent protection elements to perform the detection of the anomaly.

16. The method of claim 15, wherein the first one of the overcurrent protection elements is an instantaneous ground time overcurrent protection element.

17. The method of claim 14, wherein the anomaly is a trip of an overcurrent protection element of the protective relay.