SYSTEMS, METHODS, AND DEVICES FOR MONITORING A CAPACITOR BANK

• US 20130204554A1
• Filed: 09/29/2011
• Published: 08/08/2013
• Est. Priority Date: 09/30/2010
• Status: Active Grant

• Current Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Original Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Inventors: Tuckey, David T., Lupin, Jean-Marc
• Granted Patent: US 10,330,725 B2
• Time in Patent Office: Days
• US Class Current: 702/58
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G01R 31/2843 In-circuit-testing
• CPC Class Codes: G01R 31/64 Testing of capacitors
• CPC Class Codes: G06F 15/00 Digital computers in general details G06F1/00 – G06F13/00; Data processing equipment in general

Abstract

Systems, methods, and devices for monitoring one or more capacitor banks are presented herein. One concept of the present disclosure is directed to a method of monitoring at least one capacitor bank having a plurality of steps. The method includes: receiving measurements indicative of voltages and/or currents on electrical lines coupled to the steps of the capacitor bank by corresponding contactors; receiving information indicative of the respective statuses of the contactors; timestamping the measurements and contactor status information; storing the timestamped measurements with corresponding timestamped contactor status information; determining a rate of change of a parameter indicative of or derived from at least the measurements associated with at least one of the steps in the capacitor bank; comparing the determined rate of change with a baseline rate of change to produce a deviation; determining if the deviation satisfies a criterion; and, if so, indicating the deviation satisfied the criterion.

Claims

1. A method of monitoring at least one capacitor bank having a plurality of steps, the method comprising:

receiving measurements indicative of voltages or currents or both on respective electrical lines operatively coupled to the plurality of steps of the capacitor bank by corresponding contactors;

receiving status information indicative of respective statuses of the contactors;

timestamping the measurements and the contactor status information;

storing the timestamped measurements with corresponding ones of the timestamped contactor status information;

for at least some of the stored timestamped measurements and contactor statuses, determining a rate of change of a parameter indicative of or derived from at least the measurements associated with at least one of the plurality of steps in the capacitor bank;

comparing the determined rate of change with a baseline rate of change to produce a deviation;

determining if the deviation satisfies a criterion; and

responsive to the deviation satisfying the criterion, indicating the deviation satisfied the criterion.

2. The method of claim 1, wherein the comparing includes determining a difference between the baseline rate of change and the determined rate of change, wherein the deviation satisfies the criterion if the difference exceeds a predetermined threshold, and wherein the indicating includes, responsive to the difference exceeding the predetermined threshold, displaying an indication that the associated step has a potential problem.

3. The method of claim 1, further comprising:

determining a confidence level for each of the steps in the capacitor bank, the confidence level indicating a confidence of a potential problem for each of the steps; and

indicating the confidence level for each of the steps.

4. The method of claim 3, wherein the confidence level includes a high level, a medium level, and a low level, the method further comprising:

assigning the high level of confidence to respective ones of the steps when the respective step always, within a period of observation, yields a deviation between the determined rate of change for that step and the baseline rate of change;

assigning the medium level of confidence to respective ones of the steps in a two-step combination which yield a deviation for any of the steps not assigned the high level of confidence; and

assigning the low level of confidence to respective ones of the steps in a combination of steps not associated with any deviations between the determined rate of change for that step and the baseline rate of change.

5. The method of claim 4, further comprising:

communicating at least one instruction to cause a disconnection of the respective ones of the steps assigned the high level of confidence.

6. The method of claim 1, further comprising:

disregarding respective ones of the measurements that are unstable due to a recent status change of one or more of the corresponding contactors.

7. The method of claim 6, wherein the disregarding includes discarding respective ones of the measurements taken within a predefined interval after the recent status change of the one or more corresponding contactors.

8. The method of claim 6, further comprising:

comparing a set of status information values from a previous measurement interval to a set of status information values in a current measurement interval; and

concluding that the measurements are unstable if the previous set of status information values is different from the current set of status information values.

9. The method of claim 1, further comprising:

normalizing the measurements against a normalizing parameter.

10. The method of claim 9, wherein the normalizing parameter includes voltage magnitude, measured frequency, measured reactive power, or ambient temperature.

11. The method of claim 1, wherein the determining the rate of change includes identifying discrete steps in the measurements, and removing the discrete steps when determining the rate of change.

12. The method of claim 1, wherein the determining the rate of change includes calculating a best-fit curve and measuring the slope of the best-fit curve at a predefined interval.

13. The method of claim 1, further comprising:

calculating a value for a predetermined parameter from the received measurements, wherein the calculating the predetermined parameter and the receiving status information are substantially synchronized.

14. The method of claim 1, wherein the receiving the status information includes receiving the status information from the contactors or receiving the status information from a power factor correction (PFC) controller operatively connected to the contactors.

15. The method of claim 1, wherein the baseline rate of change is a preset value for a given type of parameter.

16. The method of claim 1, further comprising:

determining a new baseline rate of change each time the received status information includes a new contactor status combination not previously received.

17. The method of claim 1, further comprising:

determining the baseline rate of change for one electrical phase of a phase-specific measurement from measurements for at least two other electrical phases.

18. The method of claim 1, wherein the determined rate of change and the baseline rate of change are in units of percent change of the predetermined parameter per unit time.

19. One or more machine-readable non-transitory storage media including instructions which, when executed by one or more processors, cause the one or more processors to perform operations associated with a capacitor bank monitoring system, the operations comprising:

receiving measurements indicative of voltages or currents or both on respective electrical lines operatively coupled to a plurality of steps in a capacitor bank by corresponding contactors;

receiving status information indicative of respective statuses of the contactors;

timestamping the measurements and the contactor status information;

storing the timestamped measurements with corresponding ones of the timestamped contactor status information;

for at least some of the stored timestamped measurements and contactor statuses, determining a rate of change of a parameter indicative of or derived from at least the measurements associated with at least one of the plurality of steps in the capacitor bank;

comparing the determined rate of change with a baseline rate of change to produce a deviation;

determining if the deviation satisfies a criterion; and

responsive to the deviation satisfying the criterion, indicating the deviation satisfied the criterion.

20. A capacitor bank monitoring system for monitoring a plurality of capacitor banks each having a plurality of steps, each of the steps including at least one capacitor, the monitoring system comprising:

one or more processors; and

one or more memory devices storing instructions which, when executed by the one or more processors, cause the capacitor bank monitoring system to perform the following operations;

receiving measurements indicative of voltages and currents on respective electrical lines selectively coupled through corresponding contactors to the plurality of steps in each of the plurality of capacitor banks;

receiving status information indicative of a respective binary status of each of the contactors;

timestamping the measurements and the contactor status information;

storing each of the timestamped measurements with a corresponding combination of the timestamped contactor status information;

for each contactor status combination, calculating a rate of change indicative of degradation of each of the steps in each of the capacitor banks;

comparing the calculated rate of change with a baseline rate of change to determine if a deviation exists between the baseline rate of change and the calculated rate of change;

if the deviation exists, analyzing the deviation to determine if the deviation satisfies a criterion; and

if the deviation satisfies the criterion, outputting a notification indicating that the deviation satisfies the criterion.