Detection of electrical theft from a transformer secondary

Patent metadata

Field	Value
Publication number	US-10732203-B2
Application number	US-201715651860-A
Country	US
Kind code	B2
Filing date	Jul 17, 2017
Priority date	May 3, 2015
Publication date	Aug 4, 2020
Grant date	Aug 4, 2020

Abstract

Techniques for identifying electrical theft are described herein. In an example, a secondary voltage of a transformer may be inferred by repeated voltage and current measurement at each meter associated with the transformer. A difference in measured voltage values, divided by a difference in measured current values, estimates impedance at the meter. The calculated impedance, together with measured voltage and current values, determine a voltage at the transformer secondary. Such voltages calculated by each meter associated with a transformer may be averaged, to indicate the transformer secondary voltage. A transformer having lower-than-expected secondary voltage is identified, based in part on comparison to the secondary voltages of other transformers. Each meter associated with the identified transformer may be evaluated to determine if the unexpected voltage is due to a load on the transformer. If a load did not result in the unexpected secondary voltage, power diversion may be reported.

First claim

What is claimed is:

1. A method of operating a smart meter, comprising:
measuring, at a metrology device of the smart meter, a first voltage level and a first current level;
calculating, by operation of a processor of the smart meter, an impedance value based at least in part on the first voltage level and the first current level;
comparing, by operation of the processor of the smart meter, the calculated impedance value to a first threshold value;
measuring, at the metrology device, a second voltage level and a second current level;
calculating, by operation of the processor, an impedance change value based at least in part on the first voltage level, the first current level, the second voltage level, and the second current level;
comparing, by operation of the processor, the calculated impedance change value to a second threshold value;
responsive to the comparison to the first threshold value or the comparison to the second threshold value, distinguishing, by operation of the processor, between circuit degradation and theft at the smart meter; and
reporting, by operation of a radio of the smart meter, based on the distinguishing, circuit degradation or theft.

2. The method of claim 1 , wherein the distinguishing and reporting comprise:
comparing a load at the smart meter to a third threshold value of past recorded loads; and
reporting, in response to loads below the third threshold value, an indication of circuit degradation.

3. The method of claim 1 , wherein the distinguishing and reporting comprise:
recording instances of measured voltage and current over time to develop historical loads measured at the smart meter;
distinguishing loads below a third threshold value of the historical loads from loads above the third threshold value of the historical loads; and
reporting degraded infrastructure when the loads are below the third threshold value.

4. The method of claim 1 , wherein the distinguishing comprises:
recording instances of voltage and current measurements over time to develop a history of loads at the smart meter; and
comparing a current load to historical loads measured by the smart meter.

5. The method of claim 1 , additionally comprising:
measuring voltage and current at a plurality of different times to obtain a time series of voltage and current measurements; and
calculating a change in voltage divided by a change in current, wherein the change in voltage and the change in current are based on differences between voltage and current measurements from among the time series.

6. The method of claim 1 , additionally comprising:
calculating a transformer secondary voltage value, based at least in part on the calculated impedance value at the smart meter; and
reporting the calculated transformer secondary voltage value.

7. The method of claim 1 , wherein the distinguishing and reporting comprise:
comparing a load at the smart meter to a third threshold value of past recorded loads; and
reporting, in response to loads above the third threshold value, an indication of theft at the smart meter.

8. The method of claim 1 , wherein the distinguishing and reporting comprise:
recording instances of measured voltage and current over time to develop historical loads measured at the smart meter;
distinguishing loads below a third threshold value of the historical loads from loads above the third threshold value of the historical loads; and
reporting theft when the loads are above the third threshold value.

9. A smart meter device, comprising:
a metrology device of the smart meter device, to measure a voltage and a current;
a processor configured to:
calculate an impedance value based at least in part on the voltage and the current;
detect that the calculated impedance value is over a threshold value;
distinguish whether the calculated impedance value being over the threshold value is caused by circuit degradation or by theft;
calculate a transformer secondary voltage value, based at least in part on the calculated impedance value at the metering device;
report the calculated transformer secondary voltage value; and
report, based on the distinguishing, circuit degradation or theft.

10. The device of claim 9 , wherein the distinguishing comprises:
determining a change in impedance that is coincident with a change in a load measured by the metrology device.

11. The device of claim 9 , wherein the distinguishing comprises:
recording the voltage and current measurements over time to develop a history of loads at the metering device; and
comparing a current load to historical loads measured by the metering device.

12. The device of claim 9 , additionally comprising:
obtaining a time series of voltage and current measurements; and
calculating a change in voltage divided by a change in current, wherein the change in voltage and the change in current are based on differences between voltage and current measurements from among the time series of voltage and current measurements.

13. One or more computer-readable media storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising:
measuring, at a metering device, a voltage and a current;
calculating, at the metering device, an impedance value based at least in part on the voltage and the current;
detecting that the calculated impedance value is over a threshold value;
distinguishing whether the calculated impedance value being over the threshold value is caused by circuit degradation or by theft;
calculating a transformer secondary voltage value based at least in part on the impedance value;
reporting the calculated transformer secondary voltage value; and
reporting, based on the distinguishing, circuit degradation or theft.

14. The one or more computer-readable media of claim 13 , wherein the distinguishing additionally comprises:
recording the measured voltage and current over time to develop historical loads measured at the metering device;
distinguishing loads within a second threshold value of the historical loads from loads not within the second threshold value of the historical loads;
reporting degraded infrastructure when the loads are within the second threshold value; and
reporting theft when the loads are not within the second threshold value.

15. The one or more computer-readable media of claim 13 , wherein the distinguishing additionally comprises:
recording the voltage and current measurements over time to develop a history of loads at the metering device; and
comparing a current load to historical loads measured by the metering device.

16. The one or more computer-readable media of claim 13 , wherein:
measuring voltage and current at a plurality of different times comprises obtaining a time series of voltage and current measurements; and
calculating the impedance value at the metering device comprises calculating a change in voltage divided by a change in current, wherein the change in voltage and the change in current are based on differences between voltage and current measurements from among the time series of voltage and current measurements.

17. The one or more computer-readable media of claim 13 , wherein calculating the transformer secondary voltage comprises:
calculating the transformer secondary voltage value, based at least in part on the calculated impedance value at the metering device such that the transformer secondary voltage value is the measured voltage at the metering device plus the quantity of the calculated impedance value at the metering device times the

Assignees

• Itron Inc

Inventors

• Driscoll Timothy James
• Sonderegger Robert

Classifications

• G01R22/066 Primary

  Arrangements for avoiding or indicating fraudulent use · CPC title

• G01R19/165

  Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values · CPC title

• G01R11/24 Primary

  Arrangements for avoiding or indicating fraudulent use · CPC title