Electric grid high impedance condition detection

Patent metadata

Field	Value
Publication number	US-10724977-B2
Application number	US-201916459329-A
Country	US
Kind code	B2
Filing date	Jul 1, 2019
Priority date	May 4, 2015
Publication date	Jul 28, 2020
Grant date	Jul 28, 2020

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 to determine a voltage of a secondary of a transformer, the method comprising:
under control of one or more processors configured with executable instructions:
receiving a plurality of voltage and current measurements of each of a plurality of meters associated with the transformer;
determining a size of a group of meters, from among the plurality of meters, that measured voltage change magnitudes that are greater than explained by corresponding current change magnitudes;
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 value;
averaging the calculated transformer secondary voltage value from each of the meters to calculate an averaged transformer secondary voltage value;
recognizing instances of impedance over an impedance threshold from among the calculated impedance values;
distinguishing from among the recognized instances, power diversion and infrastructure degradation, based at least in part on the size of the group of meters; and
reporting the averaged transformer secondary voltage value and at least one of infrastructure degradation and power diversion.

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

3. The method of claim 1 , wherein the method additionally comprises:
accessing a time series of paired voltage and current measurements; and
calculating an impedance value based on at least two pairs of measurements from within the time series.

4. The method of claim 1 , wherein the method additionally 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 a threshold value.

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

6. The method of claim 1 , wherein the method additionally comprises:
tracking data showing loads over time with respect to an individual meter; and
determining if calculated impedance over a first threshold value or impedance change over a second 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 , wherein the method additionally comprises:
comparing instances of the averaged transformer secondary voltage value of the transformer to a threshold of permitted voltage variability; and
responsive to the comparing exceeding the threshold of permitted voltage variability, flagging the transformer for possible electrical diversion.

8. A system, 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 utilize the data and to perform actions comprising:
calculating impedance values of a meter to obtain calculated impedance values, wherein the calculated impedance values are based at least in part on:
voltage and current measurements made at a plurality of different times; and
voltage and current measurements indicating a plurality of different load conditions;

utilizing at least some of the calculated impedance values to calculate a secondary voltage value of a transformer to which the meter is connected;
ranking a plurality of transformers based on calculated secondary voltage values;
determining that no transformer load change was contemporaneous with a change in the ranking of the plurality of transformers; and
responsive the determination, reporting possible theft.

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

10. The system of claim 8 , wherein the actions 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 a possible existence of an unauthorized transformer or an unauthorized load.

11. The system of claim 8 , wherein the actions additionally comprise:
comparing secondary voltages of transformers on a same feeder line;
establishing the ranking of the plurality of transformers based at least in part on the comparing;
detecting the change in the secondary voltage ranking; and
reporting the detected change.

12. The system of claim 8 , wherein the actions additionally comprise:
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. The system of claim 8 , wherein the actions additionally comprise:
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.

14. The system of claim 8 , additionally comprising:
one or more data concentrator devices, to process instances of secondary voltage values and/or instances of change between sequential updates of calculated transformer secondary voltage values.

15. One or more non-transitory computer-readable media storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising:
receiving a plurality of measured voltage and current values from a plurality of metrology devices of a plurality of meters, respectively;
calculating impedance values of each of the plurality of meters based on the plurality of measured voltage and current values to obtain calculated impedance values, wherein the calculated impedance values are based at least in part on measurements made at the plurality of meters;
utilizing the calculated impedance values for each of the plurality of meters, and at least some of the plurality of measured voltage and current values, to calculate, for each respective meter, a transformer secondary voltage value of a transformer;
averaging the calculated transformer secondary voltage values of the respective meters to calculate an averaged transfo

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

• Y04S40/20

  Information technology specific aspects, e.g. CAD, simulation, modelling, system security · CPC title

• Y04S10/52

  Outage or fault management, e.g. fault detection or location · CPC title