Electrical wiring inspection system

• US 20050212526A1
• Filed: 03/21/2005
• Published: 09/29/2005
• Est. Priority Date: 03/23/2004
• Status: Active Grant

• Current Assignee: Frederick K. Blades
• Original Assignee: Pass & Seymour Incorporated (Legrand SA)
• Inventors: Blades, Frederick K.
• Granted Patent: US 7,057,401 B2
• Time in Patent Office: Days
• US Class Current: 324/543
• CPC Class Codes: G01R 1/025 concerning dedicated user interfaces, e.g. GUI, or dedicated keyboards G01R31/31912 takes precedence
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G01R 19/2516 Modular arrangements for computer based systems; using personal computers (PC's), e.g. "virtual instruments"
• CPC Class Codes: G01R 27/16 Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
• CPC Class Codes: G01R 31/086 in power transmission or distribution networks, i.e. with interconnected conductors
• CPC Class Codes: G01R 31/54 Testing for continuity
• CPC Class Codes: G01R 31/58 Testing of lines, cables or conductors testing of electric windings G01R31/72
• CPC Class Codes: G01R 31/67 Testing the correctness of wire connections in electric apparatus or circuits

Abstract

A system for testing and documenting the electrical wiring in a building, for example, comprises a Portable Circuit Analyzer (PCA) that is connected to the building'"'"'s Load Center through an umbilical cord. The PCA is in wireless communication with a hand-held computer device, such as a personal digital assistant (PDA) as now widely available, provided with custom software according to the invention. The electrician connects the PCA in succession to each circuit in the building, operating each switch, and each fixture or appliance, while recording the test results of the circuit element on the PDA. The PCA measures the resistance and length of each circuit thus established. When the test process is completed, the PDA is enabled to generate a complete schematic diagram of the building, including, for example, an identification of the branch circuit to which each fixture, outlet, appliance, or other load or connection point is connected.

Claims

1. An electrical measuring system for testing an electrical power distribution system, the electrical power distribution system comprising a load center having branch circuit breakers and a ground, the system comprising:

a first electrical measuring device electrically and physically connected to the load center, the device being capable of monitoring electrical parameters, selected from the group comprising voltage and current, at the load center,

a second portable electrical device being supplied with a plurality of adapter connectors capable of being plugged into various types of receptacles on a branch circuit and capable of performing tests of said branch circuits by applying test loads across the contacts of the receptacles and measuring voltages on the contacts with respect to ground,

an umbilical conductor electrically connecting the first electrical device to the second portable electrical device, and

one or more computing circuits for controlling the tests and saving the results.

2. The system of claim 1 wherein the first electrical device is capable of monitoring current through each branch circuit breaker independently and identifying the branch circuit breaker through which the monitored current is flowing.

3. The system of claim 2 wherein the first electrical device monitors current flowing through each branch circuit breaker by measuring the voltage across it in synchronization with the application of the load by the second portable electrical device.

4. The system of claim 3 wherein a magnetic probe comprising a magnet with a wire electrically connected to it and a series current-limiting device, the combination encased in an insulating protective cover, is attached to the steel wire-retaining screw on each branch circuit breaker to measure the voltage across it.

5. The system of claim 2 wherein the first electrical device monitors current flowing through each branch circuit breaker by measuring the output of a current sensor, selected from a group comprising current transformers and Hall-effect sensors, in synchronization with the application of the load by the second portable electrical device.

6. The system of claim 1 wherein the second electrical device is adapted to automatically identify the type of adapter cable used.

7. The system of claim 1 wherein the second portable electrical device is capable of applying test loads between one of the conductors of the branch circuit and ground, with a return path through the umbilical conductor, to produce a non-canceling magnetic field around the branch conductor for the purpose of tracing it.

8. The system of claim 7 wherein a third portable electrical device is provided to indicate the proximity of, and the direction of current flow in, the branch conductor, the device comprising,

a two-axis magnetic field sensor producing two signals, each responsive to the strength and direction of the magnetic field in one orthogonal direction,

an electrical circuit capable of detecting the signals in synchronization with the application of the load by the second portable electrical device, and

a display device capable of indicating the strength and direction of the magnetic field.

9. The system of claim 7 wherein a third portable electrical device is provided to indicate the proximity of, and the direction of current flow in, the branch conductor, the device comprising,

a three-axis magnetic field sensor producing three signals, each responsive to the strength and direction of the magnetic field in one orthogonal direction,

an electrical circuit capable of detecting the signals in synchronization with the application of the load by the second portable electrical device, and

a display device capable of indicating the strength and direction of the magnetic field.

10. The system of claim 1 wherein the first electrical device, upon being plugged into a receptacle on a branch circuit, is adapted to sense the presence of voltage and in response initiate further measurements to be taken.

11. The system of claim 1 further including a portable computer programmed so as to allow an electrician to exercise control of the system, by selecting the tests to be performed, and to view the results of the measurements and calculations performed accordingly.

12. The system of claim 11 wherein the portable computer is wirelessly linked to the system via a radio transceiver.

13. A method enabling an electrician to test an electrical power distribution system, the electrical power distribution system having a load center and branch circuits with receptacles, the method comprising the steps of:

attaching a first electrical device to the load center, the device being capable of monitoring electrical parameters in the load center,

electrically connecting an umbilical conductor between the load center and a second portable electrical device, said second portable device being supplied with a plurality of adapter connectors capable of being plugged into various types of receptacles on a branch circuit, and being capable of performing various electrical tests,

moving about the branch circuits and plugging the second portable electrical device sequentially into receptacles, the device automatically performing various electrical tests at each receptacle, and

evaluating the condition of the branch circuit responsive to said tests.

14. The method of claim 13, wherein the first electrical device monitors current flow through the load center in synchronization with the second portable electrical device applying a test load between contacts in the receptacles.

15. The method of claim 14, wherein the test load is applied for a period of time during which the first electrical device monitors the current in each branch circuit breaker successively, thereby determining the circuit breaker through which the test load current is flowing.

16. The method of claim 15, wherein the current flowing through each circuit breaker is measured by measuring the voltage across the circuit breaker.

17. The method of claim 16, wherein contact is made with each circuit breaker, to measure the voltage across it, by using a magnetic probe that sticks to the wire-retaining steel screw in the circuit breaker.

18. The method of claim 13 wherein a portable computer is programmed so as to allow an electrician to exercise control of the system, by selecting the tests to be performed, and to view the results of the measurements and calculations performed accordingly.

19. The method of claim 18 wherein the portable computer uses the measurements to calculate the length and resistance of each wire tested, from the point of test to the load center, and from these parameters estimate the gauge of the wire.

20. The method of claim 18 wherein the portable computer uses the measurements and calculations to construct a label for the Load Center, the label listing the number, type and location of receptacles and lights on each branch circuit.

21. The method of claim 18 wherein the portable computer uses the measurements and calculations to construct a schematic diagram of the electrical power distribution system.

22. The method of claim 18 wherein the portable computer saves the measurements into data tables and records these tables onto a non-volatile medium.

23. The method of claim 13 further comprising circuits for monitoring high-frequency noise characteristic of electrical arcing while the electrician provides a stimulus to generate arcing, selected from the group of switching switches, physically tapping fixtures, turning ON or OFF appliances, or conducting load tests.

24. The method of claim 13, wherein the second portable electrical device applies a test load between a branch conductor at the receptacle and Ground at the load center, the return path being through the umbilical conductor, to produce a non-canceling magnetic field around the branch conductor for the purpose of tracing it.

25. The method of claim 24, wherein the electrician uses a third portable electrical device, the device being capable of sensing the strength and direction of the magnetic field in synchronization with the application of the test load, to locate the branch conductor.

26. The method of claim 25, wherein the portable electrical device senses the magnitude and direction of the magnetic field in two dimensions and provides a display responsive to the direction for the purpose of locating the conductor.

27. The method of claim 25, wherein the portable electrical device senses the magnitude and direction of the magnetic field in three dimensions and provides a display responsive to the direction for the purpose of locating the conductor.

28. A method for measuring the source resistance of each wire in a grounded branch circuit of an AC electrical power distribution system, the circuit having one or more Hot conductors, a Neutral conductor and a Ground conductor, the method comprising the steps of:

measuring with respect to the Ground conductor, the average DC level of the AC voltages on the Hot conductors and the Neutral conductor

applying a half-wave rectified load between each Hot conductor and alternately the Neutral conductor, and the Ground conductor, and remeasuring the the average dc level of the AC voltages therebetween, and

calculating the total source resistance of each wire responsive to the difference in the average DC level of the AC voltages.

29. A method for measuring the source resistance of each wire in a branch circuit of an AC electrical power distribution system having a load center with a Ground, the circuit having one or more Hot conductors, the method comprising the steps of:

measuring with respect to Ground, the average DC level of the AC voltages on the various conductors of the branch circuit,

applying a half-wave rectified load between each Hot conductor and alternately the other wires in the branch circuit, and remeasuring the average DC level of the AC voltages on the various conductors of the branch circuit, and

calculating the total source resistance of each wire responsive to the difference in the average DC level of the AC voltages.

30. A method for measuring, on a branch circuit of an AC electrical power distribution system having a load center with a Ground, the resistance of each wire between a point of test and the load center and the source resistance of each wire at the load center, the method comprising the steps of

measuring at the point of test with respect to Ground, the average DC level of the AC voltages on the various conductors of the branch circuit,

measuring at the load center with respect to Ground, the average DC level of the AC voltage on the various conductors of the branch circuit,

applying a half-wave rectified load at the test point between each Hot conductor and alternately the other wires in the branch circuit, and then remeasuring at the load center with respect to Ground, the average DC level of the AC voltage on the various conductors of the branch circuit, and

calculating the source resistance of each wire at the test point, the source resistance of each wire at the load center, and the resistance of each wire between the point of test and the load center, this difference being the source resistance of each wire at the test point less the source resistance of each wire at the load center responsive to the different measured values for the average DC level.

31. A method for measuring the length of wires in a branch circuit of an AC electrical power distribution system having a load center, the circuit having two or more conductors physically coupled in close proximity to each other, the method comprising the steps of:

generating a fast-rising pulse at a first point on the branch circuit,

conducting the pulse down a transmission line to a second point in the branch circuit, the length and propagation speed of the transmission line being known,

coupling the pulse to the branch circuit at the second point, and

detecting the pulse at the first point on the branch circuit, while measuring the time interval between generation of the pulse and detecting it, less the propagation time of the pulse down the transmission line, and determining the length of the wire responsive to the measured time interval.

32. The method of claim 31 wherein the second point is the load center.

33. The method of claim 31 wherein the duration of the time interval is measured by integrating a constant during the time interval.

34. A method for an electrician to locate a Hot wire between a first point and a second point on a branch circuit of an AC electrical power distribution system having a load center, the second point being a shorter distance down the branch circuit from the load center than the first, the method comprising the steps of:

connecting a first electrical device at the first point, and a second electrical device at the second point,

connecting an umbilical conductor between the first device and the second, the umbilical conductor providing a current path that is physically separated from the branch circuit,

periodically applying a load between the Hot wire at the first point and a Neutral or Ground conductor at the second point, the umbilical conductor carrying the load current,

monitoring the resulting magnetic field around the Hot conductor with a third portable sensing device, the device being capable of measuring the strength and direction of a magnetic field, and

displaying signals based on the magnetic field measurements responsive to the proximity of the wire and the direction of the current flowing in the wire.

35. The method of claim 34 wherein the second point is the load center.

36. The method of claim 34 wherein the portable sensing device measures the direction of the magnetic field on two or more axes.

37. A method for an electrician to locate a non-energized wire between a first point and a second point on a branch circuit of an AC electrical power distribution system having a load center, the method comprising the steps of:

connecting a first electrical device at the first point and a second electrical device at the second point on the branch circuit,

connecting an umbilical conductor between the first device and the second, the umbilical conductor providing a current path that is physically separated from the branch circuit,

periodically applying a voltage with the first electrical device so as to force a current from the first device through the non-energized wire to the second device and through the umbilical conductor back to the first device thereby completing a current loop,

monitoring the resulting magnetic field around the wire with a third portable sensing device, the device being capable of measuring the strength and direction of a magnetic field, and

displaying signals based on the magnetic field measurements responsive to the proximity of the wire and the direction of the current flowing in the wire.

38. The method of claim 37 wherein the second point is the load center.

39. The method of claim 37 wherein the portable sensing device measures the direction of the magnetic field on two or more axes.