AUTOMATIC IDENTIFICATION OF MULTIPLE POWER GRIDS USING DATA SYNCHRONIZATION

• US 20110004324A1
• Filed: 07/01/2009
• Published: 01/06/2011
• Est. Priority Date: 07/01/2009
• Status: Active Grant

• Current Assignee: Schneider Electric USA, Inc. (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Bickel, Jon A., Carter, Ronald W.
• Granted Patent: US 8,260,579 B2
• Time in Patent Office: Days
• US Class Current: 700/3
• CPC Class Codes: G01D 2204/47 Methods for determining the topology or arrangement of meters in a network
• CPC Class Codes: G01D 4/002 Remote reading of utility meters
• CPC Class Codes: H02J 13/00002 characterised by monitoring
• CPC Class Codes: H02J 13/00006 characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
• CPC Class Codes: H02J 3/02 using a single network for simultaneous distribution of power at different frequencies; using a single network for simultaneous distribution of ac power and of dc power
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H04Q 2209/60 for transmitting utility meters data, i.e. transmission of data from the reader of the utility meter
• CPC Class Codes: H04Q 2209/823 where the data is sent when the measured values exceed a threshold, e.g. sending an alarm
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/18 using switches, relays or circuit breakers, e.g. intelligent electronic devices [IED]
• CPC Class Codes: Y04S 10/30 State monitoring, e.g. fault, temperature monitoring, insulator monitoring, corona discharge
• CPC Class Codes: Y04S 20/12 Energy storage units, uninterruptible power supply [UPS] systems or standby or emergency generators, e.g. in the last power distribution stages
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading
• CPC Class Codes: Y04S 40/12 characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment

Abstract

A method of automatically identifying whether intelligent electronic devices (IEDs) in a power monitoring system are in multiple electrical grids. A controller sends an instruction to each IED in a predetermined time sequence such that each IED receives the instruction at a different time, commanding each IED to begin logging variation data indicative of frequency variations in a current/voltage signal monitored by the IED and to send the variation data to the controller and an associated cycle count of a point in the current/voltage signal. The controller receives the variation data and associated cycle count and determines a peak correlation using a data alignment algorithm on IED pair combinations. If the IEDs are on the same electrical grid, the peak correlations should occur at cycle count offsets that match the order that the IEDs received the instruction. Any discrepancies in the expected order of peak correlations are flagged, and the corresponding IEDs are determined to be on different grids.

Claims

1. A method of automatically identifying a plurality of independent electrical grids in a utility system that includes a plurality of intelligent electronic devices (IEDs) communicatively linked to a master controller in the utility system, comprising:

communicating from the master controller an instruction to each of the IEDs in a sequential order at a predetermined time interval (a) to begin storing variation data indicative of variations of an electrical characteristic in a corresponding monitored current or voltage signal being monitored by respective ones of the IEDs, and (b) to store a point on the signal as a periodic indicator value;

receiving from each of the IEDs the variation data and the corresponding periodic indicator value;

for a plurality of pair combinations of the IEDs, automatically correlating, via the master controller, the respective variation data from each of the pair combinations to produce a plurality of first correlation values and determining, responsive to the automatically correlating, via the master controller, whether a correlation criterion is satisfied for each of the pair combinations, wherein each of the first correlation values is associated with a corresponding first periodic indicator offset value, wherein the first periodic indicator offset value corresponds to a difference between the respective periodic indicator values for the pair combination; and

responsive to the correlation criterion not being satisfied for a flagged one of the pair combinations, storing an indication that the IEDs corresponding to the flagged pair combination are in different electrical grids.

2. The method of claim 1, wherein the correlation criterion is that no peak correlation value, which exceeds a predetermined amount, exists for the pair combination.

3. The method of claim 2, wherein the predetermined amount is at least 25% higher than the next highest correlation value for the pair combination.

4. The method of claim 1, wherein the correlation criterion is whether a peak correlation value of the first correlation values exceeds the other first correlation values by a predetermined amount.

5. The method of claim 4, wherein the predetermined amount is at least 25% higher than the next highest correlation value.

6. The method of claim 1, wherein the correlation criterion is whether an absolute value of the most negative of the first correlation values does not exceed an absolute value of the highest of the first correlation values by more than 25%.

7. The method of claim 1, wherein the determining whether the correlation criterion is satisfied includes:

determining whether a peak correlation value associated with a first pair combination of the IEDs occurs before a peak correlation value associated with the second pair combination of the IEDs; and

responsive to the peak correlation value associated with the first pair combination occurring after the peak correlation value associated with the second pair combination, determining that the correlation threshold is not satisfied.

8. The method of claim 7, wherein the determining whether the correlation criterion is satisfied includes:

responsive to the variation data being stored, communicating from the master controller an instruction to each of a first pair of the IEDs in a sequential order at a time interval to begin storing second variation data indicative of the electrical characteristic in the corresponding monitored current or voltage signal being monitored by respective ones of the first pair of the IEDs;

receiving from each of the first pair of the IEDs the second variation data;

determining which of the first correlation values for the first pair of the IEDs has a maximum value to produce a first peak correlation value, and wherein the first periodic indicator offset value corresponding to the first peak correlation value is a first peak periodic indicator offset value;

automatically correlating the second variation data to produce a plurality of second correlation values, wherein each of the second correlation values is associated with a corresponding second periodic indicator offset value;

responsive to the automatically correlating the second variation data;

determining which of the second correlation values for the first pair of the IEDs has a maximum value to produce a second peak correlation value, and wherein the second periodic indicator offset value corresponding to the second peak correlation offset value is a second peak periodic indicator offset value, and

determining whether an absolute difference between the first peak periodic indicator offset value and the second peak periodic indicator offset value exceeds a predetermined threshold; and

responsive to the absolute difference exceeding the predetermined threshold, determining that the correlation criterion is not satisfied.

9. The method of claim 1, wherein the periodic indicator value is a cycle count that corresponds to a number of full or half cycles of the monitored current or voltage signal.

10. The method of claim 9, wherein each of the cycles indicates a periodic crossing of zero volts or amps by the monitored current or voltage signal.

11. The method of claim 1, further comprising:

responsive to the variation data being stored, communicating from the master controller an instruction to each of a first pair of the IEDs in a sequential order at a time interval to begin storing second variation data indicative of the electrical characteristic in the corresponding monitored current or voltage signal being monitored by respective ones of the first pair of the IEDs;

receiving from each of the first pair of the IEDs the second variation data;

determining which of the first correlation values for the first pair of the IEDs has a maximum value to produce a first peak correlation value, and wherein the first periodic indicator offset value corresponding to the first peak correlation value is a first peak periodic indicator offset value;

automatically correlating the second variation data to produce a plurality of second correlation values, wherein each of the second correlation values is associated with a corresponding second periodic indicator offset value;

responsive to the automatically correlating the second variation data;

determining which of the second correlation values for the first pair of the IEDs has a maximum value to produce a second peak correlation value, and wherein the second periodic indicator offset value corresponding to the second peak correlation offset value is a second peak periodic indicator offset value, and

determining whether an absolute difference between the first peak periodic indicator offset value and the second peak periodic indicator offset value exceeds a predetermined threshold; and

responsive to the absolute difference exceeding the predetermined threshold, determining that the correlation criterion is not satisfied.

12. The method of claim 1, responsive to the correlation criterion being satisfied for a flagged one of the pair combinations, storing an indication that the IEDs corresponding to the flagged pair combination are in the same electrical grid.

13. The method of claim 12, wherein the predetermined threshold is zero or less than the absolute difference between the first and second peak periodic indicator values.

14. The method of claim 1, wherein the master controller is one of the IEDs.

15. The method of claim 1, wherein the variation data is indicative of frequency variations or amplitude variations in the monitored current or voltage signal and wherein the electrical characteristic is a frequency or amplitude of the monitored current or voltage signal.

16. The method of claim 4, further comprising determining a level of symmetry of the first correlation values relative to the peak correlation value as a function of the first periodic indicator offset values, and responsive to the level satisfying a criterion, determining that the correlation criterion is satisfied.

17. The method of claim 16, wherein the level of symmetry is determined by applying a correlation function to the first correlation values to produce a symmetry correlation value, the criterion including whether the symmetry correlation value exceeds about 0.75.

18. A method of automatically identifying a plurality of independent electrical grids in a utility system that includes a plurality of intelligent electronic devices (IEDs) communicatively linked to a master controller in the utility system, comprising:

communicating from the master controller an instruction to each of the IEDs to begin storing variation data indicative of variations of an electrical characteristic in a corresponding monitored current or voltage signal being monitored by respective ones of the IEDs;

storing a first time that the instruction is communicated from the master controller to each of the IEDs;

determining a second time corresponding to a time that the IED has started to store the variation data;

receiving from each of the IEDs the variation data;

for a plurality of pair combinations of the IEDs, automatically correlating, via the master controller, the respective variation data from each of the pair combinations to produce a plurality of first correlation values and determining, responsive to the automatically correlating, via the master controller, whether a peak one of the first correlation values occurs between the first time and the second time for one of the IEDs in the respective pair combination; and

responsive to the peak one of the first correlation values not occurring between the first time and the second time, storing an indication that the IEDs corresponding to the pair combination are in different electrical grids.

19. The method of claim 18, wherein the determining the second time includes communicating to the master controller an acknowledgement that the variation data is being stored.

20. The method of claim 18, wherein the instruction is communicated to each of the IEDs in a sequential order at a predetermined time interval.