Patent Publication Number: US-10775420-B2

Title: Non-contact multi-phase cable sensor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/401,656 filed on Sep. 29, 2016, the contents of which, in its entirety, is herein incorporated by reference. 
    
    
     GOVERNMENT INTEREST 
     The embodiments herein may be manufactured, used, and/or licensed by or for the United States Government without the payment of royalties thereon. 
    
    
     BACKGROUND 
     Technical Field 
     The embodiments herein generally relate to power usage monitoring, and more particularly to devices used for monitoring power usage in electrical devices. 
     Description of the Related Art 
     There are a number of devices for monitoring power usage. In general, these conventional devices require disabling power to the cable and using an electrician for proper installation (physical attachments) of voltage and current probes. An energized electric power cable generates low-frequency electric and magnetic fields that are related to the voltages and currents. Especially at wavelengths λ&gt;&gt;d, where d is the distance away from an energized conductor and λ is the signal wavelength, one may extract electrical information, such as voltage and current on each phase, with (near-field) electric and magnetic field theory and the Principle of Superposition. 
     Coulomb&#39;s and Biot-Savart&#39;s Laws, respectively, relate the electric and magnetic fields to the voltage V and current I on a single straight energized wire: 
                     E   _     =         ρ   ⁡     (   V   )           ɛ   0     ⁢   2   ⁢   π   ⁢           ⁢   d       ⁢       a   ^     r               (   1   )                 B   _     =           μ   0     ⁢   I       2   ⁢   π   ⁢           ⁢   d       ⁢       a   ^     φ               (   2   )               
where μ 0  and ε 0  are magnetic permeability and electric permittivity constants, ρ is the surface charge density on the wire, and a φ  and a r  are vectors pointing in the direction of the field in cylindrical coordinates. Superposition principles are used with Coulomb&#39;s and Biot-Savart&#39;s Laws in multi-wire configurations (i.e., 3-phase power cables). The boundary element method or electromagnetic models are typically used to solve for ρ(V).
 
     SUMMARY 
     In view of the foregoing, an embodiment herein provides a system comprising at least one electric field sensor, and at least one magnetic field sensor, wherein the at least one electric field sensor and the at least one magnetic field sensor are formed as an integrated sensor unit with a single electrical circuit, and wherein the integrated sensor is configured to measure power of an energized cable. 
     The integrated sensor may be configured to measure power on any of a 1-, 2-, and 3-phase power cable. The integrated sensor may be configured to perform simultaneous electric and magnetic field measurements of an energized conductor in the energized cable. The integrated sensor may adjust its own variable gain and variable offset based on a type of cable for which power is being measured. The integrated sensor may receive a DC single-ended voltage supply to power the integrated sensor. The electrical circuit may be formed on a printed circuit board (PCB). The at least one electric field sensor and the at least one magnetic field sensor may be formed on a same side of the PCB. The at least one electric field sensor may comprise an electric field transducer comprising an isolated conducting component (e.g., foil section) on the PCB, on the layer closest to the power cable. 
     The electric-field transducer may comprise any of a guard and a shield. The at least one electric field sensor may comprise a charge induction electric-field sensor. The charge induction electric-field sensor may be integrated into the PCB, and may include a guard (or driven shield) to minimize the effects of capacitive coupling to the rest of the PCB circuitry, and/or a shield to reduce the sensitivity to unwanted fields; e.g., originating away from the power cable being monitored. 
     The integrated sensor may be adjacent to the energized cable, and may be held in place with a cable tie or other fastener (e.g., Velcro® fasteners, etc.). The at least one magnetic field sensor may comprise multiple magnetic field sensors. The multiple magnetic field sensors may be configured to be arranged in a line across the energized cable. The at least one electric field sensor may be spaced apart from the at least one magnetic field sensor. The integrated sensor may be configured to measure voltage and current magnitudes and phases in real time for each conductor in the energized cable. The system may further comprise a signal conditioning module comprising a microcontroller, a digital-to-analog converter (DAC) operatively connected to the microcontroller, a variable gain circuit operatively connected to the DAC, and a differential operational amplifier operatively connected to the microcontroller, the DAC, and the variable gain circuit, wherein the at least one electric field sensor, the at least one magnetic field sensor, and the signal conditioning module are formed as an integrated sensor unit with a single electrical circuit. 
     The microcontroller may be configured to act as a master of the at least one electric field sensor and at least one magnetic field sensor. The integrated sensor may be operatively connected to the variable gain circuit. The system may further comprise a processor configured to program the integrated sensor through the microcontroller. The processor and the microcontroller may be one device. 
     These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which: 
         FIG. 1  is a schematic diagram of a sensor system according to an embodiment herein; 
         FIG. 2  is a schematic diagram of a split-phase power cable according to an embodiment herein; 
         FIG. 3  is a schematic diagram of a printed circuit board with several magnetic-field sensors and an electric-field sensor according to an embodiment herein; 
         FIG. 4  is a schematic diagram illustrating an example implementation of a sensor system using a split-phase (120/240-V) power cable according to an embodiment herein; 
         FIG. 5  is a schematic diagram illustrating a a charge induction electric-field electrode protected by a guard and a shield; 
         FIG. 6  is a schematic diagram illustrating yet another example implementation of a sensor system using a three-phase (120/208-V) NATO power cable according to an embodiment herein; 
         FIG. 7A  is a plot showing the horizontal (H y ) components of the magnetic field around an example three-phase power cable according to an embodiment herein; 
         FIG. 7B  is a plot showing the vertical (H z ) components of the magnetic field around an example three-phase power cable according to an embodiment herein; and 
         FIG. 8  is a system block diagram according to an embodiment herein. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. 
     The embodiments herein provide for the integration of electric and magnetic field sensors for measuring power on 1-, 2-, or 3-phase power cables. Referring now to the drawings, and more particularly to  FIGS. 1 through 8 , where similar reference characters denote corresponding features consistently throughout the figures, there are shown exemplary embodiments. 
     As shown in  FIG. 1 , the embodiments herein provide a non-contact cable sensor system (hereinafter “sensor  10 ”). The sensor  10  may include a PCB  20  with electric- and magnetic-field sensors placed near the outer surface of a multi-conductor cable  30  and communicatively coupled to a processor  25 . The sensor  10  provides for a multi-channel sensor for simultaneous, real-time measurement of electric and magnetic fields near the surface of the power cables  30 . The power cables  30  may be energized 1-, 2-, or 3-phase cables, in example embodiments. Hall-effect sensors may be used to detect DC magnetic fields (associated with DC electric currents); however, Hall-effect sensors may also be used to detect AC fields (typically 50/60 Hz and harmonics). In a single-phase power cable  30 , the measured magnetic field is linear and in phase with the current. In a split-phase (e.g., 120/1240-V, sometimes called 2-phase)  31 , as illustrated in  FIG. 2 , the measured field is the superposition of the constituent fields from each conductor. In this case, multiple sensors are used to sense the combined field at several different locations and or orientations. Accordingly, in the split-phase (120/240-V) cable  31  shown in  FIG. 2  (with reference to  FIG. 1 ), which is typical of a 200-A home service entrance cable, three magnetic sensors  16   a - 16   c  are used to estimate the currents in the two conductors  11  (or two power conductors and a neutral). 
     As shown in  FIG. 3 , with reference to  FIGS. 1 and 2 , electric and magnetic field sensors  15 ,  16  are integrated into a PCB  20 ; i.e., one conductor part of a PCB  20 .  FIG. 3  shows the PCB  20  with several magnetic-field sensors  16   a - 16   c  and an electric-field sensor (e.g., sensing electrode  17 ). The sensors  16   a - 16   c  may be positioned on the bottom side  21   b , nearest the placement of the cable  30  (not shown in  FIG. 3 ). To condition sensor outputs, a current preamp (e.g., a variable offset circuit  56  and associated passive components) may be located on the top side  21   a  of the PCB  20  as well as the voltage amplifier (e.g., variable gain circuit  54 ) and analog-tri-digital converter (ADC)  52 . A microcontroller  50  may also be placed on the top side  21   a  of the PCB  20 . However, the specific layout may be adjusted to minimize PCB area, separate analog and digital grounds, and other design and/or manufacturing considerations. In the example embodiment shown in  FIG. 3 , the microcontroller  50  may be used only for gain control and other “smart sensing” functions. These functions may be eliminated or may perform additional processing tasks. Alternately, the analog signal may be routed to a separate processor board (e.g., processor  25  in  FIG. 1 ), or the sensor  16  may use analog signal processing. In another example, the processor  25  and microcontroller  50  may be one in the same; e.g., the same device with dual functionality. In such an example, the processing and calibration may occur integral to the cable sensor  10  and may transmit pre-configured or filtered processed monitoring or calibration events wirelessly. For example, the sensor  10  may provide information pertaining to wireless transmission and total power consumption, among other features. In another example, the sensor  10  may be configured as a battery-powered device. 
     The PCB  20  shown in  FIG. 3  does not show other active and passive circuit features commonly associated with printed circuit boards so as not to unnecessarily obscure the features associated with the embodiments herein. Many of these circuit features are standard components in printed circuit board technology and those skilled in the art would readily understand how and where such features would be configured on the PCB  20 . 
     The PCB  20  may preferably communicate with 1-Wire and Serial Peripheral Interface (SPI) protocols through a microcontroller  50  communicating with a processor  25  (shown in  FIG. 1 ) or other processing device, to obtain ideal sensor characteristics from the user through a Transducer Electronic Data Sheet (TEDS) compliant (IEEE std. 1451) interface. The 1-Wire protocol is a digital communication standard that allows several devices to communicate over a single electrical connection (not including ground). The 1-Wire protocol may be utilized to communicate digital information about each transducer in a TEDS compliant manner during sensor initialization, thereby providing a “smart sensor” capability. Additionally, the 1-Wire protocol may be implemented with software in the microcontroller  50  that also performs other “smart sensing” functions, Which saves power and board space, and keeps the component count and cost down. In accordance with an embodiment herein, the processor  25  records the sensor outputs, and communicates with other devices and end users, typically via a network. In various examples, the processor  25  may be a personal computer running MATLAB® software, for example, in a laboratory environment, or the processor  25  may be a low-power microcontroller or a field-programmable gate array (FPGA) running embedded code in an operational environment. Other implementations of the processor  25  are also possible in accordance with the embodiments herein. The PCB  20  automatically adjusts sensor gains and offsets based on the type of cable  30  and user parameters, which maximizes dynamic range autonomously. The sensor  10  may be used with a calibration procedure that allows original current and voltage information to be extracted. Many possible calibration methods exist and may be used in accordance with the embodiments herein. 
     In contrast to conventional devices, the sensor  10  provided by the embodiments herein may be adjacent to the cable  30  such that the sensor  10  may be placed near or in contact with (e.g., “clipped” or “strapped” onto) the outside of an insulated cable  30  in order to monitor overall power usage. For example, the clipping or strapping may occur using a flexible strap with hook and loop-type fasteners such as Velcro® fasteners, or using electrical tape or other electrical adhesive wrapped around the sensor  10  and cable  30 , Additionally, the sensor  10  may be permanently fixed to the insulated cable  30 . The sensor  10  does not require power to be shut-off by an electrician for installation. Accordingly, the embodiments herein provide for a non-invasive, non-interruptive technique, which may be readily installed or moved by a user. 
     The sensor  10  comprises one or more electric field sensors  15  and one or more magnetic field sensors  16  integrated on a PCB  20 , with signal conditioning processes also on the PCB  20 . The magnetic field sensors  16  may be configured as Hall-Effect (B field) sensors  16   a - 16   c  that monitor the varying currents on the cable  30 , where N magnetic sensor outputs are used to estimate up to N line currents. The one or more magnetic field sensors  16  may measure the magnetic field at N locations. Both types of sensors  15 ,  16  are integrated directly on the single PCB  20 . 
     The example embodiment shown in  FIG. 3  provides a single cable sensor  10  with three Hall-effect sensors  16   a - 16   c  and one E-field sensor  15  to detect two-line currents and one neutral current in a typical 200-A, 120/240-V split-phase home power cable. While the examples herein describe Hall-effect sensors, the embodiments herein are not restricted to these types of sensors. Other example sensors which may be utilized include magneto-resistive (MR) sensors, including anisotropic magneto-resistive (AMR), giant magneto-resistive (GMR), tunnel magneto-resistive (TMR), colossal magneto-resistive (CMR), and extraordinary magneto-resistive (EMR) sensors. Other chip-scale sensors, including small coil-based sensors, fluxgates, or other types of magnetometers, may also be used. The embodiments herein provide for using two of these cable sensors to detect 3-phase currents in a 3-phase power cable. 
     As mentioned, the magnetic field may be measured by a Hall-Effect (B-field) sensor  16 , in an example. In one embodiment, as shown in  FIG. 4 , with reference to  FIGS. 1 through 3 , three one-dimensional Hall-Effect sensors  16   a - 16   c  are arranged in a line across an energized power cable  30  to measure the magnetic field at three spatially diverse locations. In the example sensor system implementation shown in  FIG. 4 , the three magnetic sensors  16   a - 16   c  are positioned transverse to the power cable  30  being sensed. If the power conductors are oriented generally parallel to the cable (as is normally the case in conventional systems), then the sensed field at each of the three sensor locations is essentially the same at power frequencies. Accordingly, the three sensors  16   a - 16   c  are positioned transverse to the power cable  30  (or around the cable  30  in another example), where the fields in a multi-conductor cable are expected to vary. In an example, these sensors  16   a - 16   c  may provide an accurate measurement of a ±10 mT magnetic field in the azimuthal direction. The output voltage of the magnetic sensor  16  is linear with a magnetic field strength up to a maximum chip output of 50-mV amplitude, for example. Accordingly, the magnetic sensitivity Ω for the sensor may be calculated as: 
     
       
         
           
             
               
                 
                   Ω 
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                         V 
                         out 
                       
                       B 
                     
                     = 
                     
                       5 
                       ⁢ 
                       
                         V 
                         T 
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
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     In the embodiment shown in  FIG. 3 , there may be one electric field sensor  15  and three magnetic field sensors  16   a - 16   c  located on the bottom side  21   b  of the PCB  20 . The electric field (or E-field) sensor  15  is used to monitor the voltage on a voltage-regulated power system (meaning the phase and magnitude of the voltage waveform are nearly constant). In an example, the electric field sensor  15  may be configured as a charge induction electric-field sensor. 
     In one example shown in  FIG. 5 , with reference to  FIGS. 1 through 4 , the transducer electrode  41  may be configured as a patch of copper or other conductive material on the bottom layer of the PCB  20 . Surrounding this is a guard  42 , which is driven at the electrode potential with a feedback circuit. In this way, no charge is induced on the electrode  41  by the surrounding circuitry: Δq=C*ΔV=(C)(0)=0. Surrounding this is a shield  43 , which is held at (AC) ground. In this way, the shield  43  will zero out the electric field inside, and all induced charges (and currents) due to the shield-to-guard capacitance will end up on the guard  42 , where they are not added to the charges/currents on the sense electrode  41 . 
     The guard  42  and shield  43  span multiple layers of the PCB  20  with conducting vias  44 . Many vias  44  may be used to help shield the sides of the electrode  41 . However, as a rule of thumb, good shielding may be obtained by making the width of the copper traces several times the distance between the PCB layers, and only a single via may be necessary to connect the parts of the guard  42  or shield  43  on each layer together. 
     In an embodiment, the driven guard  42  and shield  43  are used to create a passive E-field transducer  40  with desired directional sensitivity (i.e., toward the power cable), while minimizing the external (clutter) E-field from other sources. Moreover, by constructing the electrode  41 , guard  42 , and shield  43  out of conducting copper in three layers of a multi-layer PCB  20 , the cost of the electrode  40  is minimized. 
     The output current from the charge induction electric-field sensing electrode  17  is proportional to the derivative of the external E-field, as given by: 
                     i   out     =       dQ   dt     =       ɛ   ⁢           ⁢     A   eff     ⁢       d   ⁢           ⁢     B   Z       dt       =     ωɛ   ⁢           ⁢     A   eff     ⁢     E     z   ⁢           ⁢   0       ⁢     sin   ⁡     (       ω   ⁢           ⁢   t     +   φ     )                     (   4   )               
where ε is the free space permittivity, ω is frequency, φ is the E-field phase, E z0  is the amplitude of the electric field, and A eff  is the effective area of the charge induction electric-field sensing electrode  17 . The effective area is the physical area of region  18 , multiplied by an enhancement factor that is determined by the geometry of the sensor. For flat electrodes, this enhancement factor may be approximately one, in one example. The current of the charge induction electric-field sensing electrode  17  is fed into a transimpedance amplifier (not shown) with a gain of 1 V/mA. The final output of the charge induction electric-field sensing electrode  17  is:
 
 V   out =1000 i   out   =βωE   z0  sin(ω t +φ)  (5)
 
where i out  is used from Eq. (4) and a constant β is introduced as being equal to 1000εA eff , which represents a frequency-independent transducer gain. This generates a relationship constant for reverse-calculating the electric field E (neglecting phase differences):
 
                   βω   =       V   out     E             (   6   )               
where β is presented in physically-meaningful units.
 
     The number and relative position of the sensors  15 ,  16   a - 16   c  are selectively chosen to maximize the signal diversity when placed over a typical 120/240-V split-phase power cable that may be used to provide 200-A utility service to a typical home. Other number and configuration of these transducers are possible for other specific scenarios. For example, as shown in  FIG. 6  (with reference to  FIGS. 1 through 5 ), using two PCBs  20  (with a total of six H-field and 2 E-field transducers), a cable sensor to a 3-phase (120/208-V, 200-A) military power cable  32  may be realized. As such, in the 3-phase (120/208-V) cable typically used with 60-kW military generators, two sets of three magnetic sensors  16   a - 16   c  are used to measure the field at additional points “around” the cable  32 , and to better estimate the three phase currents. 
       FIGS. 7A and 7B , with reference to  FIGS. 1 through 6 , are plots showing the horizontal (H y ) and vertical (H z ) components of the magnetic field around an example three-phase power cable according to an embodiment herein. In the plots of  FIGS. 7A and 7B , three of the larger conductors (top two and bottom right) are energized to an rms voltage of 120 V, and are 120 degrees out of phase with each other. Each of these conductors carries 100 A rms, in phase with their respective voltages. The bottom left conductor and the four remaining conductors are grounded and carry no current. The strength and direction of the magnetic field vary significantly around the cable, and may be measured at multiple locations to more accurately measure the power flow in the cable. 
     Other implementations include using pairs of cable sensors on 480-V, 3-phase power cables. The arrangement of E-field sensors  15  and B-field sensors  16   a - 16   c  around a multi-conductor cable  32  enables the transducers to have good spatial diversity relative to the conductors. In general, this provides good mathematical diversity of the resulting signals, which may provide more accurate estimation of conductor power after a calibration procedure. 
     The sensor  10  adjusts itself on start-up based on the type of cable  30  to increase the usable dynamic range and linearity of its output. The sensor  10  uses a signal conditioning module  45  comprising a microcontroller  50 , digital-to-analog converter (DAC)  52 , variable gain circuit  54 , and variable offset circuit (e.g., an operational amplifier (op-amp))  56 , with the DAC  52 , variable gain circuit  54 , and variable offset circuit  56  configured on the top layer  21   a  of the PCB  20 . In one embodiment, the DAC  52  comprises an 8-channel DAC. The connections of sensors  15 ,  16   a - 16   c  to the signal conditioning module  45  are shown in  FIG. 8 , with reference to  FIGS. 1 through 7B .  FIG. 8  shows four transducers that are managed over a single 1-Wire interface  65 . The sensor  10  optimizes its own gain voltage and offset voltage using the signal conditioning module  45  in the following manner: (1) The microcontroller  50  reads ferroelectric random-access memory (FRAM) (not shown) for current DAC outputs on the eight channels of the DAC  52 . (2) The microcontroller  50  changes the digital value for one of eight DAC channels through the SN bus  60 . (3) The DAC  52  sets the corresponding analog output voltage to a desired variable circuit input  62 . (4) The variable gain circuit  54  and/or variable offset circuit  56  outputs changes  63 . (5) The output signal  64  is measured by the analog-to-digital converters (ADCs) (not shown) of the microcontroller  50 . Based on the ADC measurement the microcontroller  50  increases or decreases the DAC  52  setting (then repeats steps 1-5 above), or keeps the DAC  52  setting and stores the setting in FRAM. This automatic gain control (AGC) feature is particularly useful with 10-12 bit ADCs, which are available at lower power and cost than 16-24-bit ADCs, and are often included in microcontroller chips. In this way, the sensor  10  may adapt to a wide variety of power cables  30 , without the need to use a high-performance ADC. 
     The differential output currents of all the magnetic field sensors (e.g., Hall-Effect sensors)  16   a - 16   c  and the electric field sensor (e.g., charge induction electric-field sensor)  15  are operatively connected to the variable gain circuit  54 , wherein the variable gain circuit  54  may change the gain magnitude across an 80-dB (1-10000 times) range depending on a supplied gain voltage V g . This may provide a total operating range up to 140 dB, even with a 10-12 bit ADC with only approximately 60 dB of instantaneous dynamic range. The variable gain circuit  54  and associated resistors (not shown) and capacitors (not shown) constitute a variable gain circuit. 
     The DC offset of the output signal  64  is slightly dependent on both the input DC offset and V g , so one may ensure a DC offset at 1.65 V, for example, with the variable offset circuit  56  immediately following the variable gain circuit  54 . The variable offset circuit  56  common-mode voltage (V CM ) pin(s) (not shown) are connected to different channels on the DAC  52 . Accordingly, the voltage may be varied on each of the V CM  pins, thereby varying the DC offset of the variable offset circuit  56  output. The variable offset circuit  56  and associated capacitors (not shown) constitute a variable offset circuit. The microcontroller  50  acts as the master for the SPI  60  and 1-Wire devices on the electric field sensor  15  and magnetic field sensor  16 , but as a slave 1-Wire device for a 1-Wire compatible processor  25 . 
     The individual sensor gains are automatically adjusted on demand by the processor  25  to maintain a high Signal-to-Noise Ratio (SNR) for optimal performance. The sensor  10  may be turned on with a DC voltage (e.g., DC+3.3V single-ended supply). The embodiments herein are not restricted to a DC+3.3 V single-ended supply. With a calibration procedure, the voltage and current magnitudes and phases may then be extracted in real time for each conductor in the cable  30 . 
     Generally, the sensor  10  provides for an integration of electric and magnetic field sensors  15 ,  16  into a PCB  20  for performing voltage and current measurements on multi-conductor cables  30  without “tapping” any of the wires. In use, the bottom of the sensor  10  may be placed near (or attached to) the outside of a multi-conductor energized power cable  30 , such as a service-entrance power cable to a building. 
     In one embodiment, the sensor  10  may be configured as a 1.25″×2″ sensor unit PCB  20 , for example, for simultaneous electric and magnetic field measurements of an energized conductor in the cable  30 . The sensor  10  adjusts its own output characteristics (gain, offset) on start-up dependent on the type of cable  30  to which the sensor  10  is attached. In this way, the sensor  10  may be used to estimate voltage and current; however, the cable sensor  10  provided by the embodiments herein does not require power outages or other special safety regulations for installation. Sensor calibration parameters, output gain, output DC offset, and device ID information may readily be extracted or altered by any 1-Wire or SPI master device as long as a +3.3V supply is provided for the sensor  10 . 
     The sensor  10  provided by the embodiments herein may be used for mobile power monitoring and energy auditing. The sensor  10  allows voltage and current monitoring without service outage and electrician. For example, the sensor  10  allows for externally monitoring of residential homes without permits or electricians for installation, mobile power monitoring for tactical microgrids, etc. The embodiments herein allow for measuring power on multi-conductor cables  30 , extracting current and voltage information for load detection, non-invasive monitoring of data across communications lines, and monitoring device health of systems and loads. In some embodiments, one or more sensors  10  may be used as an electromagnetic field acquisition module or processor as described in U.S. patent application Ser. No. 14/274,259 filed May 9, 2014 and entitled, “Method and Apparatus for Power Quality and Synchrophasor Monitoring on Power Lines,” the complete disclosure of which, in its entirety, is herein incorporated by reference. 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others may, by applying current knowledge, readily modify and adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein may be practiced with modification within the spirit and scope of the appended claims.