Electric grid high impedance condition detection

Patent metadata

Field	Value
Publication number	US-10338017-B2
Application number	US-201514702759-A
Country	US
Kind code	B2
Filing date	May 4, 2015
Priority date	May 4, 2015
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

Techniques for detecting high impedance conditions in an electrical grid are described herein. In one example, impedance is calculated for each of a plurality of locations within the electrical grid, such as at electrical meters. The impedances may be calculated as a change in voltage divided by a change in current, such as between sequential voltage/current measurements. Statistics may be maintained, including the calculated impedances. In three examples, statistics may be used to identify growth in impedance over multiple days, to identify growth in impedance over multiple hours, and to identify a meter for which impedance is higher than impedance for other meters attached to a single transformer. In a further example, instances of impedance over a threshold value may be identified, from among the maintained statistics. The instances of high impedance may be reported for reasons including cost and safety.

First claim

What is claimed is:

1. A method of configuring a plurality of meters that are measuring power provided by a transformer, to determine a voltage of a secondary of the transformer, wherein the transformer does not have a voltage meter, the method comprising:
under control of one or more processors configured with executable instructions:
making a plurality of voltage and current measurements at each of the plurality of meters associated with the transformer;
calculating impedance values of each of the plurality of meters associated with the transformer to obtain calculated impedance values, wherein the calculated impedance values are based at least in part on measurements made at each of the plurality of meters;
utilizing the calculated impedance values for each of the plurality of meters, and at least some of the plurality of voltage and current measurements, to calculate, for each respective meter, a transformer secondary voltage;
averaging the calculated transformer secondary voltages of the respective meters to calculate an averaged transformer secondary voltage value;
while power is provided to each of the plurality of meters, detecting at least one of:
an instance of the transformer secondary voltage value, calculated by averaging voltages of the plurality of meters, below a first threshold value; or
an instance of a change, between sequential updates of calculated transformer secondary voltage, that is greater than a second threshold value; and reporting the detected instance.

2. The method of claim 1 , wherein calculating the impedance values for each of the plurality of meters comprises:
dividing a change in measured voltage by a change in a measured current at each of the plurality of meters.

3. The method of claim 1 , wherein calculating the impedance values for each of the plurality of meters comprises:
accessing a time series of paired voltage and current measurements; and
calculating an impedance value based on two pair of measurements from within the time series.

4. The method of claim 1 , wherein calculating impedance values for each of the plurality of meters associated with the transformer comprises:
identifying growth in impedance in one or more of the plurality of meters over multiple calculated impedances associated with multiple days;
identifying growth in impedance in one or more of the plurality of meters over multiple calculated impedances associated with a day or less;
identifying a meter for which impedance is higher than impedance for other meters associated with the transformer; and
identifying a meter having impedance greater than the first threshold value.

5. The method of claim 1 , additionally comprising:
identifying meters that have impedance values over the first threshold value or instances of impedance change over the second threshold value;
locating at least one upstream meter of one or more of the identified meters; and
calculating the impedance of the at least one upstream meter.

6. The method of claim 1 , additionally comprising:
tracking data showing loads over time with respect to an individual meter; and
determining if calculated impedance over a third threshold value or impedance change over a fourth threshold value indicate power provided through degraded infrastructure or power diversion within an electrical grid based at least in part on the data showing loads over time.

7. The method of claim 1 , additionally comprising:
determining a size of a group of meters measuring voltage change magnitudes that are greater than explained by corresponding current change magnitudes; and
distinguishing power diversion from a high impedance condition based at least in part on the size of the group of meters.

8. A circuit card adapted for use in a meter, the circuit card comprising:
a processor;
memory in communication with the processor;
data, based on voltage and current measurements, maintained in the memory; and
an analytics application, operable by the processor and defined at least in part in the memory, to input the data and to perform actions comprising:
calculating impedance values at the meter to obtain calculated impedance values, wherein the calculated impedance values are based at least in part on the data, and wherein the calculated impedance values are based on measurements made at a plurality of different times and measurements indicating a plurality of different load conditions, wherein the calculated impedance values are based at least in part on measurements made at the meter;
utilizing at least some of the calculated impedance values to calculate a secondary voltage value of a transformer to which the meter is connected; and
while power is provided to the meter, detecting at least one of:
instances of the secondary voltage values of the transformer below a first threshold value; or
instances of change between sequential updates of calculated transformer secondary voltage values is greater than a second threshold value; and

reporting the detected instances.

9. The circuit card of claim 8 , wherein actions of the circuit card additionally comprise:
comparing the calculated secondary voltage value of the transformer to a threshold of permitted voltage variability; and
responsive to the calculated secondary voltage value exceeding the threshold of permitted voltage variability, flagging the transformer for possible electrical diversion.

10. The circuit card of claim 8 , wherein actions of the circuit card additionally comprise:
comparing the calculated secondary voltage value of the transformer to predicted voltage based at least in part on voltage falloff of transformers based on distance from a substation; and
responsive to the calculated secondary voltage value being less that predicted voltage, flagging possible unauthorized transformer or unauthorized load.

11. A system, comprising the circuit card of claim 8 , and a central office computing device, wherein the system is configured for acts comprising:
comparing secondary voltages of transformers on a same feeder line;
establishing a ranking of transformers based on secondary voltage;
detecting a change in the ranking; and
reporting the detected change in the ranking.

12. A system, comprising the circuit card of claim 8 , wherein the system is configured for acts comprising:
comparing secondary voltages of transformers on a same feeder line; and
providing information about a location of an unauthorized transformer based at least in part on the comparison.

13. A system, comprising the circuit card of claim 8 , wherein the system is configured for acts comprising:
determining if transformer load change was contemporaneous with a change in secondary voltage ranking of a plurality of transformers; and
responsive to failure of transformer load change to explain the change in secondary voltage ranking of the plurality of transformers, reporting possible theft.

14. A system, comprising the circuit card of claim 8 , wherein the system is configured for acts comprising:
identify a voltage drop at the transformer that is not correlated to current use measured by meters connected to the transformer; and
report a likelihood of power diversion located at the transformer.

15. A system, comprising the circuit card of claim 8 , wherein the system additionally comprises:
one or more data concentrator devices, to process instances of secondary voltage values and/or the instances of change between sequential updates of calculated transformer secondary voltage values.

16. One or more non-transitory computer-readable media storing comput

Assignees

• Itron Inc

Inventors

• Sonderegger Robert
• Driscoll Timothy James

Classifications

• H02J2103/30

  Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks · CPC title

• H02J13/12

  Monitoring network conditions, e.g. electrical magnitudes or operational status · CPC title

• H02J13/333 Primary

  the equipment forming part of substations · CPC title

• G06Q50/06

  Energy or water supply · CPC title

• G01R19/2513

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title