Electrical network impedance determination

Patent metadata

Field	Value
Publication number	US-11366149-B2
Application number	US-202016936403-A
Country	US
Kind code	B2
Filing date	Jul 22, 2020
Priority date	Jul 26, 2019
Publication date	Jun 21, 2022
Grant date	Jun 21, 2022

Abstract

The present disclosure relates to the determination of impedances in an electrical network. Methods and apparatuses for determining one or more impedances within a root and branch network are disclosed. The impedance of a common root part and the impedance of a branch of the electrical network may be determined based on the current in the common root part, the current in a branch of the electrical network and the voltage across the common root part and the branch. By determining the impedance of different parts of the electrical network in this way, the network may be monitored over time and the location of any faults or impending faults in the network may be identified more exactly without requiring invasive network probing and testing.

First claim

The invention claimed is:

1. A system for determining an impedance of an electrical network, wherein the electrical network comprises a common root part, a first branch and a second branch, wherein the first branch and the second branch are both coupled to the common root part of the electrical network, the system comprising:
an electrical network monitoring unit configured to:
determine a plurality of electrical measurement data sets, each electrical measurement data set comprising: a measure of current through the common root part, a measure of current through the first branch, a measure of current through the second branch, a measure of voltage across the first branch and common root part, and a measure of voltage across the second branch and common root part;
define, using the plurality of electrical measurement data sets, a set of simultaneous equations that define a relationship between current, voltage and impedance of the first branch, the second branch, and the common root part; and
determine, by solving the set of simultaneous equations, one or more of: an impedance of the common root part, an impedance of the first branch, an impedance of the second branch.

2. The system of claim 1 , wherein at least one of the electrical measurement data sets is linearly independent from at least one other of the electrical measurement data sets.

3. The system of claim 1 , wherein each set of each electrical measurement data set corresponds to a different point in time.

4. The system of claim 3 , wherein the measures of current and voltage in a first electrical data set of the plurality of electrical data sets are taken at a first point in time and the measures of current and voltage in a second electrical data set of the plurality of electrical data sets are taken at a second point in time, and wherein at least one of the following applies:
the current in the first branch at the first point in time is different to the current in the first branch at the second point in time;
the current in the second branch at the first point in time is different to the current in the second branch at the second point in time;
the current in the common root part at the first point in time is different to the current in the common root part at the second point in time.

5. The system of claim 4 , wherein at least one of the following applies:
the current in the first branch at the first point in time is different to the current in the first branch at the second point in time by at least a current difference threshold;
the current in the second branch at the first point in time is different to the current in the second branch at the second point in time by at least a current difference threshold;
the current in the common root part at the first point in time is different to the current in the common root part at the second point in time by at least a current difference threshold.

6. The system of claim 1 , wherein the measure of current through the common root part is a measure of change in current through the common root part, and
wherein the measure of current through the first branch is a measure of change in current through the first branch, and
wherein the measure of current through the second branch is a measure of change in current through the second branch, and
wherein the measure of voltage across the first branch and common root is a measure of change in voltage across the first branch and common root part, and
wherein the measure of voltage across the second branch and common root is a measure of change in voltage across the second branch and common root part.

7. The system of claim 6 , wherein the electrical network monitoring unit is further configured to:
detect a transition in the current that exceeds a current transition threshold in at east one of: the first branch, the second branch, the common root part; and
determine an electrical data set of the plurality of electrical data set to correspond to the detected transition, such that the measures of current and voltage in the electrical data set are indicative of the changes in current and voltage corresponding to the detected transition.

8. The system of claim 1 , wherein the measure of voltage across the first branch and common root part is a difference between a voltage measurement taken at the common root part and a voltage measurement taken at the first branch, and
wherein the measure of voltage across the second branch and common root part is a difference between the voltage measurement taken at the common root part and a voltage measurement taken at the second branch.

9. The system of claim 1 , wherein the electrical network monitoring unit is further configured to:
monitor a condition of at least part of the electrical network based on the determined one or more of: the impedance of the common root part, the impedance of the first branch, or the impedance of the second branch.

10. The system of claim 9 , wherein monitoring the condition of at least part of the electrical network comprises determining whether or not a fault has occurred in the at least part of the electrical network.

11. The system of claim 10 , wherein the electrical network monitoring unit is further configured to detect a fault in the common root part if at least one of the following conditions is met:
the measure of impedance of the common root part exceeds a maximum threshold value; or
the measure of impedance of the common root part is below a minimum threshold value.

12. The system of claim 10 , wherein the electrical network monitoring unit is further configured to detect a fault in the first branch if at least one of the following conditions is met:
the measure of impedance of the first branch of exceeds a first branch maximum threshold value; or
the measure of impedance of the first branch is below a first branch minimum threshold value.

13. The system of claim 10 , wherein the electrical network monitoring unit is further configured to generate an electrical network condition report based at least in part on the determined one or more of:
the impedance of the common root part, the impedance of the first branch, or the impedance of the second branch.

14. The system of claim 1 , further comprising:
a first current sensor coupled to the electrical network monitoring unit and arranged to measure current in the first branch;
a second current sensor coupled to the electrical network monitoring unit and arranged to measure current in the second branch;
a third current sensor coupled to the electrical network monitoring unit and arranged to measure current in the common root part;
a first voltage sensor coupled to the electrical network monitoring unit and configured to measure a voltage at the first branch relative to a reference potential;
a second voltage sensor coupled to the electrical network monitoring unit and configured to measure a voltage at the second branch relative to the reference potential; and
a third voltage sensor coupled to the electrical network monitoring unit and configured to measure a voltage at the common root part relative to the reference potential; and
wherein the first voltage sensor and third voltage sensor are arranged such that a difference between the measured voltage at the common root part and the measured voltage at the first branch is the measure of voltage across the first branch and common root part of the electrical network, and
wherein the second voltage sensor and third voltage sensor are arranged such that a difference between the measured voltage at the common root part and the measured voltage at the second branch is the measure of vo

Assignees

• Analog Devices International Unlimited Co

Inventors

• Stuart John
• Danesh Seyed Amir Ali
• Martini Luca

Classifications

• G01R27/18 Primary

  Measuring resistance to earth {, i.e. line to ground} · CPC title

• G01R31/086

  in power transmission or distribution networks, i.e. with interconnected conductors · CPC title

• G01R27/08 Primary

  Measuring resistance by measuring both voltage and current · CPC title

• G01R27/16

  Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line · CPC title

• G01R31/50

  Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58) · CPC title