Systems and methods for measuring electrical power usage in a structure and systems and methods of calibrating the same

Some embodiments can concern a method of using a power consumption measurement device. The method can include: determining first magnetic field readings from main electrical supply conductors using sensors; after determining the first magnetic field readings, electrically coupling a first calibration load to the electrical power infrastructure; while the first calibration load remains electrically coupled to the electrical power infrastructure, determining second magnetic field readings from the main electrical supply conductors using the sensors; calibrating the power consumption measurement device using at least in part the first magnetic field readings and the second magnetic field readings, after calibrating the power consumption measurement device, determining third magnetic field readings from the main electrical supply conductors; and determining an electrical power used by the electrical power infrastructure using at least the third magnetic field readings and the one or more calibration coefficients. Other embodiments are disclosed.

FIELD OF THE INVENTION

This invention relates generally to apparatuses, devices, systems, and methods for monitoring electrical power, and relates more particularly to such apparatuses, devices, systems, and methods that monitor electrical power in one or more main electrical power conductors at an electrical circuit breaker panel of a structure.

DESCRIPTION OF THE BACKGROUND

A structure (e.g., a home or a commercial building) can have one or more main electrical power conductors that supply the electrical power to electrical devices (i.e., the load) in the structure. Most structures use a split-phase electrical power distribution system with up to three main electrical power conductors. The main electrical power conductors enter the structure through an electrical circuit breaker panel. An electrical circuit breaker panel is the main electrical distribution point for electricity in a structure. Electrical circuit breaker panels also provide protection from over-currents that could cause a fire or damage electrical devices in the structure. Electrical circuit breaker panels can be coupled to and overlay at least part of the three main power conductors.

Different manufacturers of electrical circuit breaker panels, including, for example, Square-D, Eaton, Cutler-Hammer, General Electric, Siemens, and Murray, have chosen different conductor spacing and configurations for their electrical circuit breaker panels. Furthermore, each manufacturer produces many different configurations of electrical circuit breaker panels for indoor installation, outdoor installation, and for different total amperage ratings, of which 100 amperes (A) and 200 A services are the most common.

The different conductor layouts in the many different types of electrical circuit breaker panels result in different magnetic field profiles at the metal surfaces of the electrical circuit breaker panels. Moreover, the layout of the internal conductors (e.g., the main electrical power conductors) is not visible without opening the breaker panel and the manner in which the internal conductor layout translates into a magnetic field profile at the surface of the electrical circuit breaker panel requires a detailed knowledge of electromagnetic theory to interpret and model correctly. It is, therefore, difficult to measure accurately the magnetic field of the one or more main electrical power conductors at a surface of the electrical circuit breaker panel. If the magnetic field of the one or more main electrical power conductors at a surface of the electrical circuit breaker panel could be accurately determined, the electrical current and power being used by the load in the structure could be determined.

Accordingly, a need or potential for benefit exists for an apparatus, system, and/or method that allows a non-electrician to determine accurately the magnetic field and other parameters related to the one or more main electrical power conductors at the surface of the electrical circuit breaker panel.

The terms “couple,” “coupled,” “couples,” “coupling,” and the like should be broadly understood and refer to connecting two or more elements or signals, electrically, mechanically and/or otherwise. Two or more electrical elements may be electrically coupled but not be mechanically or otherwise coupled; two or more mechanical elements may be mechanically coupled, but not be electrically or otherwise coupled; two or more electrical elements may be mechanically coupled, but not be electrically or otherwise coupled. Coupling may be for any length of time, e.g., permanent or semi-permanent or only for an instant.

“Electrical coupling” and the like should be broadly understood and include coupling involving any electrical signal, whether a power signal, a data signal, and/or other types or combinations of electrical signals. “Mechanical coupling” and the like should be broadly understood and include mechanical coupling of all types.

The absence of the word “removably,” “removable,” and the like near the word “coupled,” and the like does not mean that the coupling, etc. in question is or is not removable.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENTS

Some embodiments can concern a method of using a power consumption measurement device. The power consumption measurement device can be mechanically coupled to a surface of a circuit breaker box overlying at least part of one or more main electrical supply conductors for an electrical power infrastructure of a structure. The method can include: determining one or more first magnetic field readings from the one or more main electrical supply conductors using one or more sensors in the power consumption measurement device; after determining the one or more first magnetic field readings, electrically coupling a first calibration load to the electrical power infrastructure; while the first calibration load remains electrically coupled to the electrical power infrastructure, determining one or more second magnetic field readings from the one or more main electrical supply conductors using the one or more sensors in the power consumption measurement device; calibrating the power consumption measurement device using at least in part the one or more first magnetic field readings and the one or more second magnetic field readings, after calibrating the power consumption measurement device, determining one or more third magnetic field readings from the one or more main electrical supply conductors using the one or more sensors in the power consumption measurement device; and determining an electrical power used by the electrical power infrastructure of the structure using at least the one or more third magnetic field readings and the one or more calibration coefficients. Calibrating the power consumption measurement device can include determining one or more first calibration coefficients for the power consumption measurement device using at least in part the one or more first magnetic field readings and the one or more second magnetic field reading.

Other embodiments can concern a method of calibrating a magnetic field sensor device. The magnetic field sensor device coupled to a first surface of a circuit breaker box. The circuit breaker box overlays an electrical power infrastructure of a building. The electrical power infrastructure has a first phase branch and a second phase branch. The magnetic field sensor device can include two or more magnetic field sensors. The method can include: determining a first amplitude and a first phase angle of a first magnetic field in the two or more magnetic field sensors of the magnetic field sensor device; receiving communications that a first load is coupled to the first phase branch of the electrical power infrastructure; while the first load is coupled to the first phase branch, determining a second amplitude and a second phase angle of a second magnetic field in the two or more magnetic field sensors of the magnetic field sensor device; receiving communications that a second load is coupled to the second phase branch of the electrical power infrastructure; while the second load is coupled to the first phase branch, determining a third amplitude and a third phase angle of a third magnetic field in the two or more magnetic field sensors of the magnetic field sensor device; and determining one or more calibration coefficients for the magnetic field sensor device at least in part using the first amplitude and the first phase angle of the first magnetic field in the two or more magnetic field sensors, the second amplitude and the second phase angle of the second magnetic field in the two or more magnetic field sensors, and the third amplitude and the third phase angle of the third magnetic field in the two or more magnetic field sensors.

Further embodiments can concern a system for monitoring electrical power usage in an electrical power infrastructure of a building. The building includes a circuit breaker box and electrical supply conductors of the electrical power infrastructure of the building. The system can include: (a) a power consumption measurement device configured to be coupled to a first surface of the circuit breaker box. The circuit breaker box overlying at least part of the electrical supply conductors for the electrical power infrastructure, the power consumption measurement device having one or more magnetic field sensors; (b) a first calibration device configured to be electrically coupled to the electrical power infrastructure, the first calibration module comprising one or more first calibration loads; and (c) a calibration module configured to run on a first processor and configured to at least partially calibrate the power consumption measurement device using data obtained from the one or more magnetic field sensors of the power consumption measurement device. The power consumption measurement device can be configured to obtain at least part of the data while at least one of the one or more first calibration loads is electrically coupled to the electrical power infrastructure and while the power consumption measurement device is coupled to the first surface of the circuit breaker box.

In yet still further embodiments, a magnetic field sensing device can include: (a) at least two magnetic field sensors configured to detect a magnetic field in a current carrying conductor; (b) a phase detector electrically coupled to outputs of the at least two magnetic field sensors; and (c) a phase indicator electrically coupled to the phase detector. The phase indictor can include a display that indicates when the at least two magnetic field sensors are in a predetermined position in relation to the current carrying conductor.

FIG. 1illustrates a view of an exemplary electrical power monitoring system100coupled to a circuit breaker panel190, according to a first embodiment.FIG. 2illustrates a block diagram of electrical power monitoring system100, according to the first embodiment.FIG. 3illustrates a cut-away view of circuit breaker panel190along conductor3-3, according to the first embodiment.

Electrical power monitoring system100can also be considered a system for monitoring electrical power usage of a structure (i.e., a building). Electrical power monitoring system100can also be considered a device and system for determining the predicted current used by one or more electrical device (i.e., the load) in a structure. Electrical power monitoring system100is merely exemplary and is not limited to the embodiments presented herein. Electrical power monitoring system100can be employed in many different embodiments or examples not specifically depicted or described herein.

In some examples, electrical power monitoring system100can include: (a) at least one sensing device110(i.e., a power consumption measurement device); (b) at least one computational unit120; and (c) at least one calibration device180.

In some examples, system100can be used on breaker panels from different manufacturers and on different types of breaker panels from the same manufacturer. In addition, in some examples, system100can be easily installed by an untrained person (i.e., a non-electrician) without opening the breaker panel box and exposing the uninsulated electrical power conductors inside.

Also as shown inFIG. 1, a conventional breaker box or circuit breaker panel190can include: (a) two or more individual circuit breakers191; (b) two or main circuit breakers192; (c) a panel196with an exterior surface; and (d) a door197that provides access to circuit breakers191and192. At least a portion of main electrical power conductors193,194, and195can be located within circuit breaker panel190. “Circuit breaker panel” can also refer to and include fuse boxes, which are still common in buildings with older electrical systems. The electrical power infrastructure of a structure can include at least circuit breaker panel190and main electrical power conductors193,194, and195. In some examples, circuit breaker panels can also refer to any type of electrical distribution panel used to provide electricity to a structure.

Main electrical power conductors193,194, and195are electrically coupled to main circuit breakers192and supply the electrical power to electrical devices (i.e., the load) in the structure. Panel196overlies at least part of main electrical power conductors193,194, and195and associated circuitry to protect people from inadvertently contacting these energized electrical power conductors. Usually, panel196is composed of steel or another metal.

Door197covers circuit breakers191and192and is typically closed for aesthetic reasons but can be opened to allow access to the levers of the circuit breakers191and192within circuit breaker panel190. As shown inFIG. 3, when door197is closed, panel region398can have a panel region depth399. The panel region depth399is typically 13 millimeters (mm) to 20 mm to allow door197to close without hitting the circuit breaker levers189. The depth of panel region depth399limits the permissible thickness of sensing device110that is mounted in panel region398. That is, in various examples, sensing device110can fit within panel region depth399so that the door of the breaker panel can be kept closed while sensing device110is in operation. In many examples, sensing device110has a depth of less than 20 mm. In the same or different examples, sensing device110can have a depth of less than 13 mm.

Residential and small commercial electrical service is typically 240 volt split phase service. This refers to the utility providing two 120 V alternating current (AC) source conductors (e.g., power conductors193and194) that are 180 degrees out of phase, along with a neutral conductor (e.g., power conductor195) that can be used to return current from either power conductor193or194. Power conductors193,194, and195are the “feeder” or “main” electrical power conductors that carry the incoming power from the utility before being split up into branch circuits that serve different loads. By sensing the magnetic fields generated by power conductors193,194, and195, system100can sense the total current drawn by all loads from the utility because all loads in the structure are coupled in parallel to power conductors193,194, and/or195.

In the United States, many different types of electrical loads are found in a building served by a 240 V split phase utility service. The electrical loads can be divided into two categories of loads: (a) 120 V loads; and (b) 240 V loads.

The 120 V loads can primarily include lower-wattage loads, i.e., loads plugged into standard 3-prong 120 V 15 A or 120 V 20 A outlets, and small appliances with less than ˜2 kW (kilowatt) power draw. These loads are wired in individual circuits between power conductors193and195pair (the “first phase branch” or the “193-195 leg” of the wiring circuit) or power conductors194and195pair (the “second phase branch” or the “194-195 leg” of the wiring circuit). When wiring a structure, electricians attempt to balance the anticipated wattage of loads and outlets on each leg, but this is not an exact process so current in the 193-195 leg and the 194-195 leg are likely to be unbalanced because a different total wattage is typically drawn from each pair. When a 120 V load is turned on, its current flows from the utility, through power conductor193or194through the main and circuit level circuit breakers, to the load, and then back to power conductor195and back to the utility.

The 240 V loads are typically large appliances (e.g., electric dryer, stove, air conditioner compressor, electric baseboard heaters) that consume more than two kW (kilowatts). In this case, the load current flows between power conductors193and194and no load current flows in power conductor195. Because of the 180 degree phase relationship between the voltages on power conductors193and194, the total voltage is 240 V.

Computational unit120can be configured to receive the output signal from calibration device180and/or sensing device110via communications module221and process the output signal to determine one or more parameters related to the electrical power usage of the structure (e.g., the electrical power used by the structure and the electrical current in main electrical power conductors193,194, and195). In some embodiments, computational unit120can be a personal computer (PC).

Controller225can be a microcontroller such as the MSP430 microcontroller manufactured by Texas Instruments, Inc. In another embodiment, controller225is a digital signal processor such as the TMS320VC5505 digital signal processor manufactured by Texas Instruments, Inc. or a Blackfin digital signal processor manufactured by Analog Devices, Inc.

Processing module222can be configured use current measurements from sensing device110to determine one or more parameters related to the electrical power usage of the structure (e.g., the electrical current and electrical power of main electrical power conductors193,194, and195). As will be explained below, calibration calculation module229can be configured to use current measurements from sensing device110to calibrate electrical power monitoring system100(e.g., calculate the calibration coefficients for sensing device110).

In some examples, processing module222and calibration calculation module229can be stored in memory226and configured to run on controller225. When computational unit120is running, program instructions (e.g., processing module222and/or calibration calculation module229) stored in memory226are executed by controller225. A portion of the program instructions, stored in memory226, can be suitable for carrying out methods1800and2000(FIGS. 18 and 20, respectively) as described below.

Calibration load module227can include one or more calibration loads. As will be explained below, the one or more calibration loads can be temporarily electrically coupled to, for example, the first phase branch of the electrical power infrastructure of structure to help calibrate electrical power monitoring system100.

In some examples, user communications device134and control mechanism132can be detachable from the rest of computational unit120and wirelessly communicate with the rest of computational unit120.

Electrical voltage sensor228can be used to determining the amplitude and phase angle of the voltage across the electrical power infrastructure. The phase angle of the current across is equal to the phase angle measured by electrical current sensors211minus the phase angle of the voltage measured using electrical voltage sensor228. That is, the phase angle of the current can be calculated in reference to the zero point crossing of the voltage.

In some examples, sensing device110can communicate the current measurement made by electrical current sensors211to computation unit120so the phase angle of the current can be calculated. In other examples, computational device120can communicate the voltage measurement by electrical voltage sensor228to sensing device110so the phase angle of the current can be calculated. In other examples, electrical voltage sensor228can be located in calibration device180.

Power source223can provide electrical power to communications module221, a processing module222, user communications device134, controller225, memory226, calibration load module227, and/or control mechanism132. In some examples, power source223can coupled to electrical connector128that can be coupled to an electrical wall outlet of the electrical power infrastructure.

User communications device134can be configured to display information to a user. In one example, user communications device134can be a monitor, a touch screen, and/or one or more LEDs (light emitting diodes).

Control mechanism132can include one or more buttons configured to at least partially control computational unit120or at least user communications device134. In one example, control mechanism132can include a power switch (i.e., an on/off switch) and/or a display switch configured to control what is displayed on user communications device134.

Still referring toFIGS. 1 and 2, sensing device110can include: (a) two or more or magnetic field sensors or electrical current sensors211; (b) a controller213; (c) a user communications module214; (d) a communications module215; (e) a power source216; and (f) a coupling mechanism219. Controller213can be used to control electrical current sensors211, user communications module214, communications module215, and power source216.

Electrical current sensors211can include an inductive pickup, a Hall effect sensor, a magnetoresistive sensor, or any other type of sensor configured to respond to the time varying magnetic field produced by the conductors inside circuit breaker panel190.

In various examples, sensing device110can be configured to be coupled to a surface of panel196using coupling mechanism219. In some examples, coupling mechanism219can include an adhesive, a Velcro® material, a magnet, or another attachment mechanism.

Communications module215can be electrically coupled to electrical current sensors211and controller213. In some examples, communications module215communicates the voltages or other parameters measured using electrical current sensors211to communications module221of computational unit120. In many examples, communications module215and communications module221can be wireless transceivers. In some examples, electrical signals can be transmitted using WI-FI (wireless fidelity), the IEEE (Institute of Electrical and Electronics Engineers) 802.11 wireless protocol or the Bluetooth 3.0+HS (High Speed) wireless protocol. In further examples, these signals can be transmitted via a Zigbee (IEEE 802.15.4 wireless protocol), Z-Wave, or a proprietary wireless standard. In other examples, communications module215and communications module221can communicate electrical signals using a cellular or wired connection.

User communications module214can be configured to display information to a user. In one example, user communications module214can be a LCD (liquid crystal display), and/or one or more LEDs (light emitting diodes).

Controller213can be configured to control electrical current sensors211, communications module215, user communications module214, and/or power source216.

Calibration device180can include: (a) a communications module281; (b) an electrical connector282; (c) a calibration load module283; (d) a user communication device184; (e) a controller285; and (f) a power source289. In some examples, communications module281can be similar or the same as communications module215and/or221. Electrical connector282can be an electrical power plug in some examples. User communication device184can be configured to display information to a user. In one example, user communication device184can be one or more LEDs.

According to Ampere's Law, magnetic fields are generated by current carrying conductors, as shown inFIG. 4. That is, the magnetic field generated by a given conductor is a three-dimensional vector field, which can be decomposed into components in each of the X, Y, and Z axes. In an alternating current system, these magnetic fields are time varying in magnitude, but maintain the same vector angle with respect to the coordinate basis. Thus, when referring to the X axis, for example, the field may at any instant be pointing in the +X direction or the −X direction as the AC current reverses direction at the line frequency of, for example, 60 Hz. It is intended that a magnetic field component in the X direction may refer to either +X or −X depending on the direction of current flow at a particular instant.

The magnetic field lines obey the “right hand rule” of Ampere's law; if the thumb of a person's right hand is aligned with the direction of current flow in the conductor, the field lines wrap around the conductor perpendicular to that conductor and in the direction of the person's fingers.

Some embodiments are primarily concerned with the magnetic field component that is oriented perpendicular to the plane of the circuit breaker panel (along the “Z” axis) because these are the field components that can be easily sensed by a magnetic field sensor (i.e., sensing device110) outside the metal cover of circuit breaker panel190.

As shown inFIG. 5, because power conductors193and194have a 180 degree phase difference, at any moment in time, the direction of the magnetic field lines loop in opposite directions.

Thus, according to Kirchhoff's Current Law, the total current through a given feed conductor (i.e., power conductors193,194, and/or195) is the sum of all of the load currents drawn from that conductor. The magnitude of the magnetic field generated by each of the conductors (i.e., power conductor193,194, or195) is therefore directly proportional to the sum of the currents drawn on all branch circuits connected to that conductor. The direction of the magnetic field lines from a given conductor does not change as the currents on the branches.

System100can be configured to sense the magnetic fields generated by at least power conductors193and194in order to address the three possible load cases: (a) 120 V load between the 193-195 leg, (b) 120 V load between the 194-195 leg, and (c) 240 V load between 193-194 leg. In most cases it is not necessary to sense the magnetic field generated by the power conductor195(i.e., the neutral conductor) because any current drawn through power conductor195is either sourced by power conductor193or194.

FIG. 6illustrates an example of electrical current sensor211, according to the first embodiment. In these examples, electrical current sensor can include: (a) one or more sensors641and642; (b) one or more amplifiers647and648; (c) one or more filters649and650; (d) one or more phase detectors651; (e) at least one differential amplifier652; and (f) at least one digitizer653.

In some examples, system100can be configured to assist the user in the proper placement of sensing device110by indicating the proper placement with user communications module214. In some examples, system100can determine proper placement by detecting an approximately 180 degree phase difference between sensors641and642that are disposed on opposite sides of a conductor (i.e., electrical power conductor193or194). In the same or different examples, user communications module214can be co-located with sensing device110or user communications module214can be used and can be remote and linked to sensing device100over a wireless network.

The purpose of ferromagnetic cores643and645is to concentrate the magnetic field from sensing coils644and646to yield a larger sensor output voltage at the output terminals of sensing coils644and646. The voltage at the output of sensing coils644and646is given by Faraday's law. That is, the voltage depends on the applied AC magnetic field, the physical dimensions of the coil and wire, the number of turns of wire in the coil, and the magnetic permeability of the core. In other examples, sensors641and642do not include the ferromagnetic cores643and645, respectively.

As shown inFIG. 7, when electrical current sensor211is coupled to circuit breaker panel190, one of sensors641and642can be located on each side of a conductor (i.e., electrical power conductor193or194). In this embodiment, the induced voltage on sensor641is 180 degrees out of phase with sensor642because the magnetic field enters sensor642from the bottom while the magnetic field enters sensor641from the top.

A plot of the phase relationship between the voltage on sensors641and642is shown inFIG. 8. Referring toFIG. 8, when the AC current flowing in the conductor (i.e., electrical power conductor193or194) induces a voltage V(sensor) at sensing coils644and646. This voltage, V(sensor) is proportional to the current, I(sensor) carried by the conductor (i.e., electrical power conductor193or194) i.e., V(sensor)=k*I(sensor). The constant of proportionality, k, can be found by drawing a known current through the conductor by temporarily connecting a calibration load (i.e., calibration load module283or227(FIG. 2)) to a circuit served by the conductor (i.e., electrical power conductor193or194) and measuring the voltage induced in sensors641and642(FIG. 6). In some cases, more than one known current may be drawn to establish a multi-point calibration of the constant of proportionality.

Referring again toFIG. 6, this configuration of two sensors (i.e., sensors641and642) can be exploited to yield a sensing device110that automatically communicates to a user that it has been correctly placed with respect to a given current carrying conductor while rejecting interference from other sources, including other nearby conductors. This ability is useful in the electrically noisy environment found in a circuit breaker panel where there are many conductors near a particular conductor of interest.

Specifically, in some embodiment, the output of each of sensors641and642can be amplified using amplifiers648and647, respectively and then filtered using filters650and649, respectively. The output of filters650and649can be presented to phase detector651coupled to a phase indicator619in user communications module214(e.g., one or more LEDs). User communications module214is configured to indicate to the user that sensors641and642have been correctly placed with respect to a given current carrying conductor. The user can be instructed to move the sensor across the region where the main electrical power conductors are to be found, and stop movement once the phase indicator indicates that the phase difference between signals of sensors641and642is approximately 180 degrees. For example, when signals from sensors641and642are approximately 180 degrees out of phase, a green LED could light-up on the top of sensing device110.

Amplifiers648and647and filters650and649are optional in some examples. The purpose of amplifiers648and647and filters650and649are to increase the signal level while rejecting noise at undesired frequencies and thus to increase the signal to noise ratio of the signals of sensors641and642in noisy environments. Amplifiers648and647can be operational amplifiers such as the type TL082 manufactured by Texas Instruments, Inc. Filters650and649can be either lumped element passive filters or active filters implemented with operational amplifiers. In general filters650and649are bandpass filters configured to pass the AC line frequency (e.g., 60 Hz in the US and Canada, or 50 Hz in Europe and Japan) while rejecting out of band noise.

Phase detector651can be either an analog phase detector circuit or a digital phase detector. A digital phase detector can be implemented with combinational logic, with programmable logic, or in software on a controller. In one embodiment, an integrated phase detector circuit such as the phase detector contained in the type 4046 or 74HC4046 phase locked loop integrated controllers manufactured by Texas Instruments, Inc. can be employed. In another embodiment, phase detector651is implemented by digitizing the sensor signals with an analog to digital converter, and then fitting an arctangent function to the vector of received samples from sensors641and642. In a further embodiment, the filtering and phase detection functions are combined by using a periodogram based maximum likelihood estimator such as a complex fast Fourier transform (FFT) algorithm to find the signal magnitude and phase angle at only the AC line frequency while rejecting noise at other frequencies.

Phase indicator619can be any device that indicates to a user that the desired phase relationship between input signals of sensors641and642has been reached. In some embodiments, the phase indicator can be one or more LEDs. In other embodiments, phase indicator619can be a graphical or numerical display such as a liquid crystal display (LCD), or an audio tone that indicates to the user that the voltages of sensors641and642are nearly 180 degrees out of phase.

Differential amplifier652can be used to combine the signals from sensors641and642to yield a voltage or current signal proportional to current in the main electrical power conductor once the correct phase relationship has been established. This signal can be used as an input for calculations performed by controller213. In the same or different example, communications module215can be used to convey to computational unit data including: (a) the proper placement of sensors641and642as indicated by the sensor phase relationship as well as (b) the differentially sensed signal from sensors641and642.

Turning to another embodiment,FIG. 9illustrates an example of sensing device910, according to a second embodiment.FIG. 10illustrates an example of sensing device910over electrical power conductors193and194, according to the second embodiment. In this example, a linear array of sensors9411,9412, . . . ,941Ncan be used where N is a number between 2 and 10. In other examples, N can be other numbers such as 4, 6, 8, 20, 50, or 100. One purpose of this linear array of sensors is to allow controller213to select automatically one or more pairs of sensors9411,9412, . . . ,941Nso the user does not have to manually place sensing device910in the correct placement. In some embodiments, sensing device910can be used instead of sensing device110in system100ofFIG. 1.

As shown inFIG. 10, the linear array of sensors9411,9412, . . . ,941Nis coupled to multiplexers955and956, which selects at least one sensor from sensors9411,9412, . . . ,941Nfor use as a magnetic field sensor to yield a signal proportional to current in main electrical power conductors193and/or194.

In another embodiment, more than one conductor of electrical power conductors193and194are simultaneously sensed by sensing device910. In this embodiment, controller213controls multiplexers955and956such that two distinct sensors from sensors9411,9412, . . . ,941Nare selected that are adjacent to two different current carrying power conductors193and194. In this embodiment, controller213controls multiplexers to select sensors based on the amplitude or phase angle of the sensor signal. In some embodiments, multiple sensor from sensors9411,9412, . . . ,941Nare multiplexed under control of controller213to select distinct sensors, each of which having preferential magnetic field coupling to a distinct current carrying conductor.

Referring again toFIG. 1, system100can use calibration in some examples to achieve accurate current measurement in electrical power conductors193and194. The potential need for calibration can be due to poorly controlled installation geometry, for example, when sensing device110or910(FIG. 9) is installed by an untrained user.

FIG. 11illustrates an example of calibration device180, according to the first embodiment. Calibration device180is shown inFIG. 11as a single circuit calibration device that is configured to switch a single calibration load to a single incoming conductor (i.e., electrical power conductor193or194) to complete a circuit between a the incoming conductor, the single calibration load, and the neutral or return conductor (i.e., electrical power conductor195). The switching signal is used to temporarily complete the circuit with the calibration load, which is used by calibration method1800ofFIG. 18.

In the embodiment ofFIG. 11, calibration load module283can be designed to calibrate the measurement of a single current carrying conductor (a feeder to the branch circuit) being measured by sensing device110. In this embodiment, a single calibration load1188is switched by switch1187between the line conductor (e.g., main electrical power conductors193and194) and the neutral conductor (e.g., main electrical power conductor195) under the control of a switching signal from a controller285. In the United States, switched load1105can be used with a 120 V outlet. In other countries, switched load1105can be used with 240 V and other voltage outlets.

It should be appreciated that while calibration load1188and the calibration loads inFIGS. 14-17are drawn as a resistor, calibration load1188and other calibration loads inFIGS. 14-17can be any load including a reactive load, such as an inductor or capacitor, with or without a resistive component. Additionally, the calibration load can be a load with a variable resistance. Furthermore, it should be appreciated that while switch1187and other switches inFIGS. 14-17are drawn as mechanical relay switches, the switches can be other forms of switching devices. For example, the switches can be a semiconductor switches such as a solid state relays, triacs, transistors such as a FETs (filed-effect transistors), SCRs (silicon-controller rectifiers), BJTs (bipolar junction transistors), or IGBTs (insulated-gate bipolar transistors), or other controllable switching devices.

As shown inFIG. 11, communications module281is coupled to controller285to enable the transfer of calibrated current measurements from calibration device180to computational unit120. In some examples, communications module281can include a receiver and transmitter. Communications module281can include any form of wired or wireless communication device operating at any frequency and with any data link protocol. In one embodiment, communications module281includes a 2.4 GHz transceiver part number CC2500, available from Texas Instruments, Inc. In another embodiment, communications module281includes a 900 MHz transceiver, part number CC2010, available from Texas Instruments, Inc. In some embodiments, communications module281can communicate using any of the following communication protocols: WiFi (IEEE 802.11), Zigbee (IEEE 802.15.4), ZWave, or the SimpliciTI protocol. In another embodiment, a proprietary data communication protocol is employed. In further embodiment, the communication link between communications module215and communications modules281and/or221is achieved through the monitored conductor. In this embodiment, the communication link is comprised of power line communication (PLC) formed by injecting a transmitted signal into at least one conductor of the branch circuit to which the calibration device is coupled.

In the example shown inFIG. 11, power source289can include a Power source289. Power source289can include an isolation transformer and a DC power supply. Power source289converts the incoming line voltage from an AC power line voltage, such as 120 V in the US and Canada, or 220 V in Europe, to a low DC voltage such as 3.3 V or 5 V DC to power controller213and other elements of calibration device180.

Controller285can receive a sample of the incoming AC power line voltage, converted by level translator1173to a lower voltage AC signal that is proportional to the incoming AC power line voltage. In some embodiments, the incoming AC power line voltage is 120 V AC while the lower voltage AC signal is within the range of 0 to 3.3 V. In some embodiments, level translator1173is employed to shift the low voltage signal from a bipolar signal that alternates between +V and −V to a unipolar signal between 0 V and VDD, or another unipolar signal range that is within the valid voltage range of analog-to-digital converter1177. Analog-to-digital converter1177can sample the incoming low voltage signal as shown inFIG. 12. In the same or different embodiments, filter1172can restrict the frequency range of the low voltage signal to the AC line frequency.

In many examples, analog-to-digital converter1177can be integrated with controller285, or it may be separate from controller213but coupled to controller285. The sampled AC line voltage enables controller213to measure the incoming AC line voltage to calibrate more accurately system100by calculating the current drawn by calibration load1188given the sampled low voltage signal, which is proportional to the AC line voltage. Furthermore, the sampled low voltage signal may be used to develop a phase reference that is synchronous to the AC line voltage.

In some embodiments, controller285uses a squared low voltage signal to develop a phase reference. In these embodiments, squaring device1174creates the square low voltage signal. The squared low voltage signal can be a square wave that has the same period and zero crossing timing as the low voltage AC signal. This relationship between the squared signal and the low voltage signal is shown inFIG. 13. In some embodiment, squaring device1174can include a Schmitt trigger, a comparator, or a digital logic gate such as an inverter or a transistor level shifter. The square wave amplitude is chosen to be a logic level that is compatible with controller285. The squared signal does not contain information about the amplitude of the incoming AC line voltage but it does contain phase information because the positive and negative-going edges of the squared signal are synchronous to the zero crossings of the incoming AC line voltage.

In some embodiments, the phase reference derived from either the low voltage signal or its squared counterpart is used to measure the relative phase angle between the calibrated current measurement reported by sensing device110and the incoming power line voltage. This relative phase angle measurement between voltage and current is used to account accurately for the power factor of reactive loads connected to the power conductor that is measured by sensing device110. The power factor is the cosine of the phase angle between the voltage and current waveforms. This power factor can be computed directly from a sampled low voltage signal, or it may be indirectly computed in the case of the squared low voltage signal by fitting a sinusoid of the proper frequency to the edge transitions in the squared signal.

The power factor is the ratio of the real power flowing in the conductor compared to the apparent power flowing in the conductor. In some embodiments, it is preferential to report to the user of system100the real power flowing in electrical power conductors193,194, and195to better approximate the reading of a utility-supplied electrical power meter. In these embodiments, the phase information provided by the low voltage signal is critical to compute properly the predicted power.

Because the calibration load1188dissipates current when it is switched on using switch1187, calibration load1188is subject to heating. This heating can endanger the safe operation of calibration load1188by causing thermal damage to calibration load1188itself, or to other components within the housing of calibration device180, or to people or things that are proximate to calibration device180.

In some embodiments, controller285includes a temperature sensor1186such as a bimetallic thermostat, a thermistor, or a semiconductor temperature sensor. In some embodiments, temperature sensor1186interrupts the switching signal to turn off calibration load1188when calibration load1188or the housing of calibration device180is too hot.

In further embodiments, controller285checks temperature reading of temperature sensor1186prior to turning on calibration load1188to ensure that calibration load1188or the housing of calibration device180is not too hot at the beginning of the calibration process. In still further embodiments, controller285can performs an extrapolation to determine if calibration load1188is likely to become too hot after a typical period of operation of calibration load1188. In this embodiment, controller285acts to defer the calibration process until the process can be completed without calibration load1188or the housing of calibration device180becoming too hot.

In some embodiments, there are two different control mechanisms by which a controller controls the switching signal to switch1187. The two methods correspond to two different processor locations that run the calibration process to obtain a calibrated current measurement.

In a first method, controller285is co-located with and controls calibration load module283. Controller285also can obtain sensor readings from sensing device110(via communications module281) and controller213. Controller285performs the calibration process (described below in reference toFIG. 18) and obtains the calibrated current measurement. In these examples, calibration calculation module229can be located in calibration device180, and not computational unit120.

In the first method where controller285runs the calibration process, communications module281receives incoming signal measurements from sensing device110and/or computational unit120. Controller285can calculate the calibrated current measurements using method2000ofFIG. 20. After calculating the calibrated current measurements, calibration device180can communicate the calibrated current measurements to computational unit120for display and other uses.

In a second method, a remote processor, such controller225(FIG. 2) or controller213(FIG. 2), commands calibration load1188to switch on and off and this controller (controller225or controller213) performs the calibration method1800ofFIG. 18and obtains the calibrated current measurement as described in method2000ofFIG. 20.

When the second method is being used with controller225in control of the calibration, controller225receives a message via a communication link from controller285. In some embodiments, controller225sends a message to turn on the calibration load for a specified period of time. In some embodiments, this period of time is selected from one or more predetermined periods of time. In other embodiments, calibration load1188is turned on until a turn-off message is received by controller285or until the expiration of a time-out timer or the activation of temperature sensor1186indicating that calibration load1188or its housing is too hot.

In further embodiments, controller285independently makes a decision to turn on the calibration load for a particular period of time. In some examples, controller285switches calibration load1188on and off for a particular period of time, while contemporaneously, previously, or at a later time sending a notification to controller225indicating that calibration load1188has been switched on. In this embodiment, controller213uses a known time offset between the messages received from controller285to synchronize the flow of the calibration procedure to calibration load1188on/off times indicated by a message received from controller285via a communication link. In further examples, controller285switches calibration load1188on and off in a sequence that is known to controller213and/or225(FIG. 2).

FIG. 11illustrates one example of switched load1105in calibration device180. Other possible configurations of the switched load are shown inFIGS. 14-17.

In this embodiment, switched load1405can be configured to calibrate the measurement of a single current carrying conductor (a feeder to the branch circuit labeled “Line”) being measured by sensing device110. In this embodiment, controller285can switch between calibration loads1188and1441to provide two different sets of measurement to use in the calibration process. In other examples, switched load1405can include three or more switch of three or more calibration loads.

In this embodiment, switched load1505can be designed to calibrate the measurement of two current carrying conductor (a feeder to the branch circuit labeled “Line1” and “Line2”) being measured by sensing device110. In this embodiment, two distinct calibration loads1588and1541can be switched between individual line conductors and the neutral conductor under the control of a switching signal from controller285. Controller285can control switching signals to electrically couple calibration loads as follows:

In this embodiment, switched load1605can also be configured to calibrate the measurement of more than one current carrying conductor (a feeder to the branch circuit labeled “Line1” and “Line2”) being measured by sensing device110. In this embodiment, two distinct calibration loads1588and1541are switched to enable calibration loads1588and1541to be connected either individually with a neutral return, or in a pair to the Line1-Line2pair as is common in a split phase power system. Controller285can control switching signals to electrically couple calibration loads as follows:

In the embodiment, switched load1705is also configured to calibrate the measurement of more than one current carrying conductor (a feeder to the branch circuit labeled “Line1” and “Line2”) being measured by sensing device110. In this embodiment, a single calibration load1788is switched to enable the calibration of two conductors plus a neutral as is common in a split phase power system. Switches1787and1743can be single pole double throw (SPDT) switches. Switches1787and1743can be used with calibration load1788to couple different combinations of the branch circuit conductors. Switched load1705can be cheaper to implement compared to switched load1605(FIG. 16) due to the single calibration load employed. Controller285can control switching signals to electrically couple calibration loads as follows:

Calibration LoadsSwitch EnabledCoupledEffectSwitch 1787 is in the 1Calibration loadPermit the calibration ofposition, switch 1743 is in1788 witha measurement of athe 1 position, and switchneutral returnfeeder to the branch1742 is in the 1 position.circuit labeled Line 2Switch 1787 is in the 0Calibration loadPermit the calibration ofposition, switch 1743 is in1788 witha measurement of athe 1 position, switch 1742neutral returnfeeder to the branchis in the 1 position.circuit labeled Line 1Switch 1787 is in the 0Calibration loadPermit the calibration ofposition, switch 1743 is in1788 in seriesa split phase electricalthe 0 position, switch 1742between Line 1system from a single splitis in the 1 position.and Line 2 withphase calibration deviceno neutral returnSwitch 1787 is in the 0 or 1NoneNoneposition, switch 1743 is inthe 0 or 1 position, andswitch 1742 is in the 0position (i.e., adisconnected position).

In many examples, both phase lines of electrical infrastructure need to be calibrated. Accordingly, one of the calibration devices of FIGS.11and14-17would need to be plugged into the first phase branch and the second phrase branch. In the example shown inFIG. 2, calibration device180is the first calibration device and computational unit120includes the second calibration device. In other examples, a single calibration device (e.g., a calibration device with one of switched load1505,1605, or1705) can be coupled to a 240 V outlet, which is coupled to both the first and second phase branch.

In the embodiment where one of the calibration devices of FIGS.11and14-17is plugged into each of the first phase branch and the second phrase branch, the calibration devices need to be able to communicate to each other, the sensing device, and the computation unit. Several different methods of communication could be implemented. For example, all of the calibration device could receive and transmit data. In other examples, one calibration device (e.g., calibration device180ofFIG. 1) could transmit data and the second calibration device (e.g., computational unit120ofFIG. 2) could receive data.

In some embodiments, the two calibration device can be in radio communication. For example, communications module281and communications module221ofFIG. 2can include a radio. The calibration devices are configured to determine if they are on different electrical phase branches by reporting the phase angle of the observed 60 Hz cycle to the other calibrators. In some examples, one calibration device can wirelessly report to the other calibration device when a zero crossing occurs in electrical current or voltage. An overlap in the received wireless messages will occur in the messages when both calibration devices are installed on the same electrical phase branch. If an offset exists between the observed zero crossing and the received message, the calibration devices are installed on different electrical phase branches.

In the same or different example, user communication device184on calibration device180(FIG. 1) can include a single red/green LED. A green LED can indicate that the two calibration devices are installed correctly on the two different phases. For example, the user first installs calibration device180ofFIG. 1(i.e., the transmitting calibration device) into an arbitrary electrical outlet. Then the user installs computational unit120ofFIG. 1(i.e., the receiving calibration device) into another electrical outlet. The LED of user communication device184can light up red to indicate that they are both on the same phase or green if they are on different phase branches. The user can move the second calibrator to different outlets until the green indicator of user communication device184is shown.

In other embodiments, wireless communication can also exist between each of sensing device110, calibration device180, and computational unit120. In this embodiment, sensing device110can detect the two electrical phases in the breaker panel. As calibration device180cycles through its electrical loads, calibration device180can notify sensing device110and sensing device110can determine which phase calibration device180is coupled to. Computational unit120can also report to sensing device110when it begins its load cycle. Sensing device110observes which phase angles these changes are occurring to infer that the calibrators are installed on two different phases.

In still another example, a non-wireless communication method can be used to communicate between calibration device180, and computational unit120. In these examples, communications modules221and/or281can include a signal injector and/or signal receiver. In this example, calibration device180and computational unit120can send a signal over the electrical power infrastructure. For example, a simple 1 kHz (kilohertz) tone can be used. In the same or different examples, the signal consists of an amplitude modulated voltage injected on to one or more conductors of the electrical power infrastructure. In another embodiment, the signal consists of an amplitude modulated current drawn from the electrical power infrastructure. In a further embodiment, the signal consists of a frequency modulated voltage or current. In one embodiment, computational unit120can be designated as a transmitter of the signal, while calibration device180can be designed as the receiver. When calibration device180is plugged into an electrical outlet, user communication device184can light up a green LED if it cannot detect the presence of the signal being transmitted by the first device. If calibration device180and computational unit120are coupled to separate phase branches, calibration device180and computational unit120could not detect signals placed on the electrical power infrastructure by the other.

If calibration device180detects the signal, then a red light can indicate the two calibration devices are on the same phase. At this point, the user can be instructed to move either one of calibration device180or computational unit120to a different electrical outlet. In yet another embodiment, instead of communications modules221and281including a signal injector and/or receiver, communications modules221and281can include powerline communication (PLC) modules to allow calibration device180and computational unit120to communicate over the electrical power infrastructure.

Turning to another embodiment,FIG. 18illustrates a flow chart for an embodiment of a method1800of calibrating an electrical monitoring system, according to an embodiment. Method1800is merely exemplary and is not limited to the embodiments presented herein. Method1800can be employed in many different embodiments or examples not specifically depicted or described herein. In some embodiments, the activities, the procedures, and/or the processes of method1800can be performed in the order presented. In other embodiments, the activities, the procedures, and/or the processes of the method1800can be performed in any other suitable order. In still other embodiments, one or more of the activities, the procedures, and/or the processes in method1800can be combined or skipped.

Method1800can be considered to describe a general method of calibrating a sensing device. This method can involve determining one or more calibration coefficients that can be used to calculate the predicted current in the electrical power infrastructure of the structure in method2000ofFIG. 20. The method described below can be used to accurately calculate the calibration coefficients regardless of the position of the sensing device110(FIG. 1) on panel196(FIG. 1) with the exception of the following points: (a) if electrical current sensors211(FIG. 2) are placed so far away from the main power conductors193and194(FIG. 1) that almost no discernable signal from main power conductors193and194is measured; and (b) if all of the electrical current sensors211(FIG. 2) are placed very close to neutral electrical power conductor195(FIG. 1) and far away from electrical power conductors193and194.

Method1800inFIG. 18includes an activity1860of obtaining and storing one or more first baseline measurements. In some examples, sensing device110(FIG. 2) can be used to obtain first baseline measurements using electrical current sensors211(FIG. 2). These first baseline measurements can include the nominal current flowing in at least one of power conductor193or194(FIG. 1) due to electrical devices that are drawings electrical power. Additionally, at every sensor (e.g., sensors641and642(FIG. 6) or sensors9411,9412, . . .941N(FIG.9)), an amplitude and phase measurement can be made. Each amplitude reading, L, is stored with the name Lold-Nand each phase reading, Ø, is stored with the name Øold-N, where N is the number of the sensor. In some examples, the first baseline measurements are made on both the first phase branch and a second phase branch.

In some examples, activity1860also includes determining the amplitude and phase angle of the voltage. The phase angle of the voltage can be used to help calculate the phase angle of the current. In some examples, electrical voltage sensor228ofFIG. 2can be used to determine the phase angle of the voltage.

Subsequently, method1800ofFIG. 18includes an activity1861of temporarily coupling a first known calibration load to the first phase branch. In some examples, calibration device180(FIGS. 1 and 11) can coupled one of the calibration loads in switched loads1105,1405,1505,1605or1705ofFIGS. 11,14,15,16, and17, respectively.

Next, method1800ofFIG. 18includes an activity1862of obtaining and storing one or more first calibration measurements on the first phase branch. In some examples, sensing device110(FIG. 2) can be used to obtain the first calibration measurements from electrical current sensors211(FIG. 2). In some examples, the first calibration measurements are performed while a known calibration load from switched load1105,1405,1505,1605, or1705ofFIGS. 11,14,15,16, and17, respectively, is coupled to first phrase branch (e.g., Line1inFIGS. 15-17). This first known calibration load will pull a known current Lcal-1. These first calibration measurements can include the nominal current flowing in at least one of power conductor193or194(FIG. 1) due to appliances that are drawings electrical power and the first known calibration load.

For example, at every sensor (e.g., sensors641and642(FIG. 6) or sensors9411,9412, . . .941N(FIG.9)), an amplitude and phase angle measurement is made. Each amplitude reading, L, is stored with a name such as Lnew-N-1and each phase angle reading, Ø, is stored with the name such as Ønew-N-1, where N is the number of the sensor.

In some examples, activity1862also includes determining the amplitude and phase angle of the voltage. The phase angle of the voltage can be used to help calculate the phase angle of the current. In some examples, electrical voltage sensor228ofFIG. 2can be used to determine the phase angle of the voltage.

Method1800inFIG. 18continues with an activity1863of disconnecting the first know calibration load and temporarily coupling a second known calibration load to a second phase branch. In some examples, calibration device180(FIGS. 1 and 11) can coupled one of the calibration loads in switched load1405,1505, or1605ofFIGS. 14,15, and16, respectively. In some examples, the second known calibration load is coupled to a second phase branch (e.g., Line2inFIGS. 15-17).

Subsequently, method1800ofFIG. 18includes an activity1864of obtaining and storing second calibration measurements on the second phase branch. In some examples, sensing device110(FIG. 2) can be used to obtain the second calibration measurements from electrical current sensors211(FIG. 2). These second calibration measurements can include the nominal current flowing in at least one of power conductor193or194(FIG. 1) due to appliances that are drawings electrical power and the second known calibration load. In some examples, the second calibration measurements are performed while a known calibration load is coupled to the second phrase branch (e.g., Line2inFIGS. 15-17). The second known calibration load will pull a known current Lca1-2.

For example, at every sensor (e.g., sensors641and642(FIG. 6) or sensors9411,9412, . . .941N(FIG.9)), an amplitude and phase angle measurement is made. Each amplitude reading, L, is stored with the name Lnew-N-2and each phase angle reading, Ø, is stored with the name such as Ønew-N-2where N is the number of the sensor.

In some examples, activity1864also includes determining the amplitude and phase angle of the voltage. The phase angle of the voltage can be used to help calculate the phase angle of the current. In some examples, electrical voltage sensor228ofFIG. 2can be used to determine the phase angle of the voltage.

Method1800inFIG. 18continues with an activity1866of obtaining and storing one or more second baseline measurements. In some examples, sensing device110(FIG. 2) can be used to obtain the second baseline measurements from electrical current sensors211(FIG. 2). This second baseline measurements can include the nominal current flowing in at least one of power conductor193or194(FIG. 1) due to appliances that are drawings electrical power. The purpose of this second baseline reading is to ensure that the baseline load observed in activity1861has not changed during the calibration process. If the measurements in activity1866are equal to the measurement from1861within a predetermined amount, the measurements from activity1866can be discarded. If the measurements in activity1866are outside the predetermined amount, the measurement from1861can be discarded. In other examples, activity1866can be skipped.

In some examples, activity1866also includes determining the amplitude and phase angle of the voltage. The phase angle of the voltage can be used to help calculate the phase angle of the current. In some examples, electrical voltage sensor228ofFIG. 2can be used to determine the phase angle of the voltage.

Subsequently, method1800ofFIG. 18includes an activity1867of determining the calibration coefficients. In some examples, activity1867include applying a sensor calibration equation (s) to the baseline measurement and each of the calibration measurements to solve for the calibration factors of sensing device110(FIG. 1) to yield a calibrated current measurement in the at least one conductor that is sensed by sensing device110. In some examples, calibration calculation module229(FIG. 2) can determine the calibration coefficients as described below.

FIG. 19illustrates a flow chart for an exemplary embodiment of activity1867of determining the calibration coefficients, according to the first embodiment. In some examples, activity1867can broadly include calculating the calibration coefficients, ØM, K1, K2, Y1, and Y2. In other examples, other calibration coefficients can be determined.

Referring toFIG. 19, activity1867includes a procedure1971of determining potential calibration coefficients for the first phase branch. In some examples, for each sensor 1 through N (where N is the number of sensors in the electrical current sensor), procedure1971can include calculating XN-1and ØM-N-1using Lold-N, Øold-N, Lcal-1, Lnew-N-1, and Ønew-N-1, where:
XN-1=[√{Lold-N2+Lnew-N-12−2*Lold-N*Lnew-N-1*Cos(Øold-N−Ønew-N-1)}]/Lcal-1
and
ØM-N-1=Ønew-N-1−Sin−1[(Lold-N*Sin(Øold-N−Ønew-N-1))/(XN-1*Lcal-1)]

Additionally, in some examples, if ØM-N-1>180°, then
ØM-N-1=ØM-N-1−180°
and
XN-1=XN-1*(−1)

Activity1867inFIG. 19continues with a procedure1972of determining potential calibration coefficients for the second phase branch. In some examples, for each sensor 1 through N, procedure1972can include calculating XN-2and ØM-N-2using Lold-N, Øold-N, Lcal-2, Lnew-N-2, and Ønew-N-2where:
XN-2=[√{Lold-N2+Lnew-N-22−2*Lold-N*Lnew-N-2*COS(Øold-N−Ønew-N-2)}]/Lcal-2
and
ØM-N-2=Ønew-N-2−Sin−1[(Lold-N−Ønew-N-2))/(XN-2*Lcal-2)]

Additionally, in some examples, if ØM-N-2>180°, then
ØM-N-2=ØM-N-2−180°
and
XN-2=XN-2*(−1)

Subsequently, activity1867ofFIG. 19includes a procedure1973of checking the validity of the measurements. In procedure1973, if ØM-N-1=ØM-N-2within a predetermined tolerance (e.g. 0.1%, 1%, 5%, 10%, or 20%) for each sensor 1 through N, the measurements for the sensor are kept. If ØM-N-1≠ØM-N-2, within the predetermined tolerance, the phase angles for that sensor are discarded.

Next, activity1867ofFIG. 19includes a procedure1974of determining a statistical mode, Ømode, for ØM-N-1for the sensors not discarded in procedure1973. In some examples, the statistical mode is the most frequently occurring phase angle within the predetermined tolerance for the sensors not discarded in procedure1973.

Activity1867inFIG. 19continues with a procedure1975of determining a first part of the calibration coefficients. In some examples, from the remaining sensors, procedure1975includes choosing the sensor with the highest value XN-1and assign XN-1=K1and XN-2=K2and ØM-N-1=ØM-K. This chosen sensor will be referred to as sensor K from hereon. Sensor K can be discarded from the list of available sensor candidates for the rest of activity1867.

Subsequently, activity1867ofFIG. 19includes a procedure1976of determining a second part of the calibration coefficients. In some examples, from the remaining sensors, procedure1976includes choosing the sensor with the highest value XN-2and assign XN-2=Y1and XN-2=Y2and ØM-N-2=ØM-Y. This chosen sensor will be referred to as sensor Y from hereon.

Next, activity1867ofFIG. 19includes a procedure1977of determining a third part of the calibration coefficients. In some examples, ØMis calculated where:
ØM=[ØM-Y+ØM-K]/2

The example of the formulas used to determine the calibration coefficients above are just exemplary. In other examples, other formulas (e.g., linear, non-linear, quadratic, and/or iterative equations) can be used to calculate the same or different calibration coefficients.

For example, the sensing device can be calibrated (and the predicted current determined) using only sensor. In this example, the sensor is placed at a location such that the magnetic field from main electrical power conductors193and194(FIG. 1) is symmetric at the sensor. That is, the magnetic field from main electrical power conductors193and194(FIG. 1) is symmetric at the sensor. In addition, in this example, sensor Z is at a location where the magnetic field from main electrical power conductor195(FIG. 1), representing the neutral return conductor, is small and can be ignored.

Let us call the sensor at this point where the magnetic fields are symmetric sensor Z. In this example, the current measured in sensor Z is equal to
Lz=Kz*Lpredicted
where Lzis the current measured by sensor Z, Kzis a constant, and Lpredictedis the predicted combined current in the first phase branch and the second phase branch.

In this example, the baseline current measurement made at sensor Z in activity1860or1866can be stored as Lz-baseline. The first calibration measurements made at sensor Z can be stored at Lz-caland the current of the first known calibration load can be ΔP. In this example, Kzcan be calculated where:
Kz=(Lz-cal−Lz-baseline)/ΔP

In other examples, other calibration equations can be used that require more than two calibration measurements. In these examples, activities1861-1866(FIG. 18) can be repeated as many times as needed with different calibration loads to obtain the needed number of calibration points.

After procedure1977is complete, activity1867of calculating of the calibration coefficients is complete.

Referring again toFIG. 18, method1800ofFIG. 18continues with an activity1868of storing the calibration coefficients. In some examples, the calibration coefficients can be stored in memory226of computational unit120ofFIGS. 1 and 2. In the same or different examples, the calibration coefficients can be stored in memory of sensing device110and/or calibration device180ofFIG. 1. In still other embodiments, the calibration coefficients can be transmitted to a remote server for storage and use. After activity1868, method1800is complete.

FIG. 20illustrates a flow chart for an embodiment of a method2000of determining the predicted current in the electrical power conductors. Method2000is merely exemplary and is not limited to the embodiments presented herein. Method2000can be employed in many different embodiments or examples not specifically depicted or described herein. In some embodiments, the activities, the procedures, and/or the processes of method2000can be performed in the order presented. In other embodiments, the activities, the procedures, and/or the processes of the method2000can be performed in any other suitable order. In still other embodiments, one or more of the activities, the procedures, and/or the processes in method2000can be combined or skipped.

Method2000describes a general method of determining the predicted electrical power (and/or electrical current) used in the electrical power conductors. This method involves using several predetermined calibration coefficients (see method18ofFIG. 18) to determine the predicted current in the electrical power infrastructure of the structure. The method described below can be used to accurately calculate the predicted currents regardless of the position of the sensing device110(FIG. 1) on panel196(FIG. 1) with the exception of the following points: (a) if electrical current sensors211(FIG. 2) are placed so far away from the main power conductors193and194(FIG. 1) that almost no discernable signal is measured; and (b) if all of the electrical current sensors211(FIG. 2) are placed very close to neutral electrical power conductor195(FIG. 1) and far away from electrical power conductors193and194. In some examples, method2000can broadly include calculating the predicted current, L1-predictedand L2-predicted(as would be reported by the electrical utility providing the electrical power) on each branch of electrical power infrastructure (e.g., the first and second phase branches).

In some examples, method1800ofFIG. 18and method2000can be combined to create a method of using a power consumption measurement device. Alternatively, method1800ofFIG. 18combined with method2000can be considered a method of determining the predicted current (and/or electrical power) in the electrical power conductors. In these embodiments, method1800can be performed once to determine the calibration coefficients and method2000can be repeatedly before to determine the predicted current (and/or electrical power) being used by the load of the structure at various times.

Referring toFIG. 20, method2000includes an activity2061of performing a first set of measurements using a first electrical current sensor. In various embodiment, one of electrical current sensors211(FIG. 2) can be used to perform the first set of measurements. In some examples, activity2061can include measuring an amplitude and phase angle at the sensor K. The amplitude reading can be stored with the name LKand the phase angle reading can stored with the name ØK.

In some examples, activity2061also includes determining the amplitude and phase angle of the voltage. The phase angle of the voltage can be used to help calculate the phase angle of the current. In some examples, electrical voltage sensor228ofFIG. 2can be used to determine the phase angle of the voltage.

Subsequently, method2000ofFIG. 20includes an activity2062of performing a second set of measurements using a second electrical current sensor. In various embodiment, one of electrical current sensors211(FIG. 2) can be used to perform the first set of measurements. In some examples, activity2063can include measuring an amplitude and phase angle of the current at the sensor Y. The amplitude reading can be stored with the name LYand the phase angle reading can stored with the name Øy.

In some examples, activity2062also includes determining the amplitude and phase angle of the voltage. As discussed above, the phase angle of the current is equal to the phase angle measured by the sensor minus the phase angle of the voltage. In some examples, electrical voltage sensor228ofFIG. 2can be used to determine the phase angle of the voltage.

Next, method2000ofFIG. 20includes an activity2063of determining a predicted electrical power used in a first phase branch. In some examples, activity2063can include determining amplitude, L1, of the first phase branch and phase angle, Ø1, of the first phrase branch using the calibration coefficients OM, K1, K2, Y1, and Y2where:
L1=[√{(LK/K2)2+(LY/Y2)2−2*(LK/K2)*(LY/Y2)*Cos(ØK−ØY)}]/[(K1/K2)−(Y1/Y2)]
and
Ø1=Tan−1[{(LK/K2)*Sin(ØK−ØM)−(LY/Y2)*Sin(ØY−ØM)}/{(LK/K2)*Cos(ØK−ØM)−(LY/Y2)*Cos(ØY−ØM)}]

In some examples, the predicted power, P1-predicted, in the first phase branch can be the electrical power in the first phrase branch as would be reported by the electrical utility. In some embodiments, the predicted current, L1-predicted, in the first phase branch is:
P1-predicted=V*L1*COS(Ø1)
where V is the voltage measured in activity2062.

Method2000inFIG. 20continues with an activity2064of determining a predicted electrical power used in a second phase branch. In some examples, activity2064can include determining amplitude, L2, of the second phase branch and phase angle, O2, of the second phrase branch using the calibration coefficients ØM, K1, K2, Y1, and Y2where:
L2=[√{(LK/K1)2+(LY/Y1)2−2*(LK/K1)*(LY/Y1)*Cos(ØK−ØY)}]/[(K2/K1)−(Y2/Y1)]
and
Ø2=Tan−1[{(LK/K1)*Sin(ØK−ØM)−(LY/Y1)*Sin(ØY−ØM)}/{(LK/K1)*Cos(ØK−ØM)−(LY/Y1)*Cos(ØY−ØM)}]

In some examples, the predicted electrical power, P2-predictedin the second phase branch can be the electrical power in the second phrase branch as would be reported by the electrical utility. In some embodiments, the predicted current, P2-predicted in the second phase branch is:
P2-predictedV*L2*COS(Ø2)
where V is the voltage measured in activity2062.

In a second example where the sensing device is using only one sensor Z, determining the predicted power, Ppredictedis relatively simple. In this example, sensor Z has been placed at a location such that the magnetic field from main electrical power conductors193and194(FIG. 1) is symmetric at sensor Z and sensor Z is at a location where the magnetic field from main electrical power conductor195(FIG. 1) is small and can be ignored. In this example, the electrical power measured in sensor Z can be calculated where:
Ppredicted=V*Lz/KZ
and where V is the voltage measured in activity2062, Lzis the current measured by sensor Z in activity2061, Kzis a constant (already determined in activity1867ofFIG. 18).

Method2000inFIG. 20continues with an activity2065of using and/or reporting the predicted current in the first and second phase branch. The total predicted electrical power, Ppredicted, is the sum of the predicted electrical power in the first phrase branch and the predicted electrical power the second phrase branch:
Ppredicted=P2-predicted+P1-predicted

In some examples, the electrical power used by the load in the structure (i.e., Ppredicted) can be displayed to the user on user communications device134of computational unit120(FIGS. 1 and 2). In other examples, the electrical power used (and/or the predicted current) can be communicated to the electrical utility providing the electrical power or can be reported to other entities.

In yet other embodiments, the predicted current can be used in disaggregating loads based on step change and phase angle between the observed current and voltage. Computational unit120can determine and assign a step change (the increase or decrease in current) to one or more electrical device in the structure to indicate its usage. Further disaggregation can be accomplished by observing the presence of 120 V and 240 V appliances from the current data on each phase branch. In addition to aggregate current step changes, step changes on each individual phase branch further identifies the presence of a different load or appliance (i.e., similar loads installed at different locations in the building). The change in phase angle observed due to a device's internal reactance allows the identification of inductive loads (i.e., fans, motors, microwaves, compressors). The predicted reactance is not required, but rather the observed raw phase angles are sufficient as long as they are associated with a device a priori. In some examples, the momentary change in current consumption on the electrical power infrastructure can constitutes a device's start-up characteristic, which can characterize residential appliances. This technique involves the use of template matching on a known library of start-up signatures to classify unknown loads. This feature space is much less susceptible to overlapping categories of devices and is able to separate many devices with similar load characteristics. For example, two motors with similar real and reactive power consumption can exhibit highly different start-up features, and thus be disaggregated. This approach can be appropriate for electrical devices that consume large current loads or at least consume large currents during start-up. Using these activities, loads on the electrical power infrastructure can be disaggregated.

FIG. 21illustrates an example of a first location of two electrical current sensors relative to main electrical power conductors193,194, and195(FIG. 1), according to an embodiment. The location of the two electrical current sensors shown inFIG. 21were used to test calibration method1800ofFIG. 18and current determination method2000ofFIG. 20. Loads coupled to main electrical power conductors193,194, and195(FIG. 1) were randomly switched on and off. While randomly switching on and off the loads, the actual current was monitored using a current monitor. The predicted currents were also calculated using methods1800and2000ofFIGS. 18 and 20after measurements were taken with the two electrical current sensors.FIG. 22illustrates a graph comparing the currents predicted by the methods ofFIGS. 18 and 20compared to the measured currents. As shown inFIG. 22, the predicted currents closely mirror the measured currents.

FIG. 23illustrates an example of a second location of two electrical current sensors relative to main electrical power conductors193,194, and195(FIG. 1), according to an embodiment. The location of the two electrical current sensors shown inFIG. 23were used to also test calibration method1800ofFIG. 18and current determination method2000ofFIG. 20. Loads coupled to main electrical power conductors193,194, and195(FIG. 1) were randomly switched on and off. While randomly switching on and off the loads, the actual current was monitored using a current monitor. The predicted currents were also calculated using methods1800and2000after measurements were taken with the two electrical current sensors.FIG. 24illustrates a graph comparing the currents predicted by the methods ofFIGS. 18 and 20compared to the measured currents. As shown inFIG. 24, the predicted currents closely mirror the measured currents.

Although the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the spirit or scope of the invention. Accordingly, the disclosure of embodiments of the invention is intended to be illustrative of the scope of the invention and is not intended to be limiting. It is intended that the scope of the invention shall be limited only to the extent required by the appended claims. For example, to one of ordinary skill in the art, it will be readily apparent that activities1860,1861,1862,1863,1864,1865,1866,1867, and1868ofFIG. 18, procedures1971,1972,1973,1974,1975,1976, and1977ofFIG. 17, and activities2061,2062,2063,2064, and2065ofFIG. 20may be comprised of many different activities, procedures and be performed by many different modules, in many different orders that any element ofFIG. 1may be modified and that the foregoing discussion of certain of these embodiments does not necessarily represent a complete description of all possible embodiments.