Abstract:
According to one aspect, embodiments of the invention provide a current monitoring device comprising a current transformer configured to be removeably coupled to a power line and to generate a reference signal having a level related to a current level of the power line, a sensor circuit connected to the current transformer and configured to be removeably coupled to a communications bus and to convert the reference signal to a digital reference signal and provide a signal indicative of the current level to the communication bus, and a housing containing the sensor circuit and the current transformer.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    At least one example in accordance with the present invention relates generally to systems and methods for monitoring a load center for current, power and energy usage. 
         [0003]    2. Discussion of Related Art 
         [0004]    A load center or panelboard is a component of an electrical supply system which divides an electrical power feed from a power line into different subsidiary circuit branches. Each subsidiary circuit branch may be connected to a different load. Thus, by dividing the electrical power feed into subsidiary circuit branches, the load center may allow a user to individually control and monitor the current, power and energy usage of each load. 
         [0005]    Current sensors are commonly used to monitor activity of a load center. For example, Current Transformers (CT) are commonly used to monitor current, power and/or energy consumption in a subsidiary or main branch of a load center. A CT may be used to measure current in a branch by producing a reduced current signal, proportionate to the current in the branch, which may be further manipulated and measured. For example, a CT coupled to a branch of a load center may produce a reduced current AC signal, proportionate to the magnitude of AC current in the branch. The reduced current AC signal may then either be measured directly or converted to a DC signal and then measured. Based on the signal received, the level of current in the subsidiary branch may be determined 
       SUMMARY OF THE INVENTION 
       [0006]    Aspects in accord with the present invention are directed to a system and method for monitoring a load center. 
         [0007]    In one aspect the present invention features a current monitoring device comprising a current transformer configured to be removeably coupled to a power line and to generate a reference signal having a level related to a current level of the power line, a sensor circuit connected to the current transformer and configured to be removeably coupled to a communications bus and to convert the reference signal to a digital reference signal and provide a signal indicative of the current level to the communication bus, and a housing containing the sensor circuit and the current transformer. In one embodiment, the sensor circuit is configured to receive power from the communications bus. 
         [0008]    According to one embodiment, the housing includes a first portion containing the current transformer and a second portion containing the sensor circuit, and wherein the first portion is rotatably coupled to the second portion. In one embodiment, the second portion of the housing includes an insulation displacement connector configured to couple the sensor circuit to the communication bus. In another embodiment, the second portion of the housing further includes a lid configured to lock the communication bus in place adjacent to the insulation displacement connector. 
         [0009]    According to one embodiment, the housing is configured to be rotated between a first position and a second position, wherein, in the first position, the first portion of the housing is rotated away from the second portion to allow external access to an interior chamber, and wherein, in the second position, the first portion of the housing is rotated towards the second portion so that the housing encompasses the interior chamber. 
         [0010]    According to another embodiment, the sensor circuit further includes a transceiver coupled to a microcontroller and configured to receive the digital reference signal and provide data related to the digital reference signal to the communications bus. In one embodiment, the transceiver is further configured to receive data from the communication bus indicative of at least one of voltage, frequency and phase information of the power line. In another embodiment, the microcontroller is configured to calculate power parameters of the power line using the digital reference signal and the data from the communications bus. 
         [0011]    In another aspect the present invention features a method for monitoring a power line within a load center, the method comprising coupling a current transformer to the power line within the load center, coupling a sensor circuit to a communication bus within the load center, generating, with the current transformer, a reference signal having a level related to a current level of the power line, converting, with the sensor circuit, the reference signal to a digital reference signal, and providing the digital reference signal to the communication bus. 
         [0012]    According to one embodiment, the act of coupling a current transformer to the power line includes encompassing the power line within the current transformer. In another embodiment, the act of coupling a sensor circuit to a communication bus includes piercing an outer insulation layer of the communication bus with at least one contact of the sensor circuit and connecting the at least one contact to an appropriate conductor within the communication bus. 
         [0013]    According to another embodiment, the method further comprises assigning a unique address to the sensor circuit over the communications bus. In one embodiment, the act of providing includes providing the digital reference signals to the communication bus at a time designated by an external controller. In another embodiment, the method further comprises receiving, with the sensor circuit, power from the communications bus. 
         [0014]    In one aspect the present invention features a device for monitoring current in a power line, the device comprising a current transformer configured to generate a reference signal having a level related to a current level of the power line, a sensor circuit configured to convert the reference signal to a digital reference signal and provide data related to the digital reference signal to a communication bus, and means for containing the current transformer and the sensor circuit within a single housing and coupling the single housing to the power line and the communications bus. 
         [0015]    According to one embodiment, the sensor circuit is configured to receive power from the communications bus. In another embodiment, the sensor circuit includes a transceiver coupled to a microcontroller and configured to receive the digital reference signal and provide data related to the digital reference signal to the communications bus. 
         [0016]    According to another embodiment, the transceiver is further configured to receive data from the communication bus indicative of at least one of voltage, frequency and phase information of the power line. In one embodiment, the microcontroller is configured to calculate power parameters of the power line using the digital reference signal and the data from the communications bus. 
         [0017]    In one aspect the present invention features a system for monitoring a plurality of circuit branches coupled to an input line, the system comprising a communication bus, a plurality of sensor circuits, each configured to be coupled to the communication bus and at least one of the plurality of circuit branches, wherein each sensor circuit is further configured to sample current in the at least one of the plurality of circuit branches, a controller configured to be coupled to the communication bus and the input line, wherein the controller is further configured to sample voltage on the input line, and wherein the controller is further configured to synchronize, via the communication bus, current sampling performed by the plurality of sensor circuits with the voltage sampling performed by the controller. 
         [0018]    According to one embodiment, the controller is further configured to receive, via the communication bus, current sampling data from at least one of the plurality of sensor circuits. In another embodiment, the controller is further configured to calculate at least one of RMS current, power, or energy usage of at least one of the plurality of circuit branches based on the current sampling data received from the at least one of the plurality of sensor circuits and voltage sampling data. In one embodiment, the controller is further configured to determine a phase angle of a voltage waveform at which current sampling and voltage sampling should occur. 
         [0019]    According to another embodiment, at least one of the plurality of sensor circuits includes a current transformer coupled to the at least one of the plurality of circuit branches. 
         [0020]    In another aspect the present invention features a method for monitoring a plurality of circuit branches coupled to a power line, the method comprising coupling a sensor circuit to each one of the plurality of circuit branches and to a communication bus, coupling a controller to the communication bus and to the power line, sampling, with at least one of the sensor circuits, current in at least one of the plurality of circuit branches, sampling, with the controller, voltage on the power line, and synchronizing, with the controller via the communication bus, the sampling of current by the at least one of the sensor circuits and the sampling of voltage by the controller. 
         [0021]    According to one embodiment, the act of synchronizing comprises detecting, by the controller, a voltage waveform on the power line, and determining, with the controller, a phase angle of the voltage waveform at which the acts of sampling current and sampling voltage should occur. In one embodiment, the act of synchronizing further comprises broadcasting, with the controller via the communication bus, to each one of the sensor circuits that the act of sampling current should begin, and initiating, after a predetermined delay following the act of broadcasting, the act of sampling voltage. In another embodiment, the act of synchronizing further comprises broadcasting, with the controller via the communication bus, to at least one of the sensor circuits that the act of sampling current should begin, and initiating, after a predetermined delay following the act of broadcasting, the act of sampling voltage. 
         [0022]    According to another embodiment, the method further comprises receiving, with the controller via the communication bus, current sampling data from at least one of the sensor circuits. In one embodiment, the method further comprises transmitting the current sampling data to an external client. In another embodiment, the method further comprises calculating, with the controller, at least one of RMS current, voltage or energy usage of at least one of the plurality of circuit branches based on the current sampling data received from the at least one of the sensor circuits and voltage sampling data. 
         [0023]    According to one embodiment, the method further comprises transmitting the at least one of RMS current, voltage or energy usage to an external client. In one embodiment, the act of transmitting includes transmitting the at least one of RMS current, voltage or energy usage wirelessly to an external client. In another embodiment, the method further comprises assigning, with the controller via the communication bus, unique addresses to each one of the sensor circuits. 
         [0024]    According to another embodiment, the method further comprises confirming, with the controller in response to the act of receiving current sampling data, that the current sampling data was received successfully, and entering, with the at least one of the sensor circuits, in response to the act of confirming, power save mode. In one embodiment, the act of entering power save mode comprises initiating a sleep timer, wherein the at least one of the sensor circuits remains in power save mode until expiration of the sleep timer. 
         [0025]    In one aspect the present invention features a system for monitoring a plurality of circuit branches coupled to an input line, the system comprising a communication bus, a plurality of sensor circuits, each configured to be coupled to the communication bus and at least one of the plurality of circuit branches, wherein each sensor circuit is further configured to sample current in the at least one of the plurality of circuit branches, a controller configured to be coupled to the communication bus and the input line, means for synchronizing current sampling performed by at least one of the plurality of sensor circuits and voltage sampling performed by the controller. 
         [0026]    According to one embodiment, the controller is further configured to receive, via the communication bus, current sampling data from the at least one of the plurality of sensor circuit. In one embodiment, the controller is further configured to calculate at least one of RMS current, power, or energy usage of at least one of the plurality of circuit branches based on the current sampling data received from the at least one of the plurality of sensor circuit and voltage sampling data. 
         [0027]    In another aspect the present invention features a system for monitoring a plurality of circuit branches coupled to an input line within a load center, the system comprising a plurality of current sensors, each configured to be coupled to at least one of the plurality of circuit branches and to produce a signal having a level related to a current level of the one of the plurality of circuit branches, a communications bus, a plurality of sensor circuits, each coupled to an associated one of the plurality of current sensors and configured to be coupled to the communication bus, wherein each one of the plurality of sensor circuits is configured to convert the signal from the associated one of the plurality of current sensors to a digital measurement signal and provide the digital measurement signal to the communication bus, and a controller configured to be coupled to the communication bus and configured to receive the digital measurement signal from each sensor circuit over the communication bus and transmit data related to the digital measurement signal from each sensor circuit to an external client. 
         [0028]    According to one embodiment, the controller is further configured to be located within the load center. In another embodiment, the system further comprises a wireless radio coupled to the controller, wherein the wireless radio is configured to transmit the data related to the digital measurement signal from each sensor circuit to an external client. 
         [0029]    According to another embodiment, each one of the plurality of sensor circuits is configured to be removeably coupled to the communication bus. In one embodiment, each one of the plurality of current sensors is configured to be removeably coupled to one of the plurality of circuit branches. In another embodiment, each one of the plurality of sensor circuits includes a secondary microcontroller coupled to the associated one of the plurality of current sensors and configured to convert the analog reference signal from the associated one of the plurality of current sensors to a digital measurement signal and provide the digital measurement signal to the communication bus. 
         [0030]    According to one embodiment, the controller includes a primary microcontroller configured to receive the digital measurement signal from each of the plurality of sensor circuits and provide the data related to the digital measurement signal from each of the plurality of sensor circuits to the external client. In one embodiment, the controller further includes a power module coupled to at least one of the plurality of circuit branches, wherein the primary microcontroller is further configured to measure at least one of voltage, phase and frequency of the at least one of the plurality of circuit branches and transmit data related to the at least one of the voltage, the phase and the frequency to at least one of the plurality of sensor circuits via the communication bus. 
         [0031]    According to another embodiment, the primary microcontroller is configured to assign a unique address to each one of the plurality of sensor circuits and to control communication on the communication bus. In one embodiment, the primary microcontroller is further configured to calculate power and energy parameters of the at least one of the plurality of circuit branches based on the digital measurement signal from at least one sensor circuit and the measured at least one of voltage, phase and frequency of the at least one of the plurality of circuit branches 
         [0032]    According to one embodiment, at least one secondary microcontroller is configured to receive the data related to the at least one of the voltage, the phase and the frequency from the primary microcontroller and calculate power and energy parameters of one of the plurality of circuit branches based on the digital measurement signal and the received data related to the at least one of the voltage, the phase and the frequency. 
         [0033]    In one aspect the present invention features a method for monitoring a plurality of circuit branches coupled to a power line within a load center, the method comprising coupling a current transformer to each one of the plurality of circuit branches, coupling a plurality of sensor circuits to a communication bus, wherein each of the sensor circuits is coupled to one of the current transformers, coupling a concentrator to the communication bus, generating, in each current transformer, a reference signal having a level related to a current level of one of the plurality of circuit branches, converting, with each of the plurality of sensor circuits, a reference signal from a corresponding current transformer to a digital measurement signal and providing the digital measurement signal to the communication bus, receiving, with the concentrator, the digital measurement signal from each sensor circuit over the communication bus, and transmitting data related to the digital measurement signal from each sensor circuit to an external client. 
         [0034]    According to one embodiment, the method further comprises managing communication over the communication bus with the concentrator. In one embodiment, the act of managing includes assigning, with the concentrator, a unique address to each one of the plurality of sensor circuits. In another embodiment, the act of transmitting includes transmitting the data related to the digital measurement signal from each sensor circuit wirelessly to an external client. 
         [0035]    According to another embodiment, the method further comprises measuring, with the concentrator, at least one of voltage, phase and frequency of power provided to the plurality of circuit branches, and transmitting data related to the at least one of the voltage, the phase and the frequency to the plurality of sensor circuits via the communication bus. 
         [0036]    According to one embodiment, the method further comprises calculating, with the plurality of sensor circuits, power and energy parameters of the plurality of circuit branches based on the received data related to the at least one of the voltage, the phase and the frequency, providing data related to the power and energy parameters to the concentrator via the communication bus, and transmitting the data related to the power and energy parameters to the external client. 
         [0037]    In another aspect the present invention features a system for monitoring a plurality of circuit branches coupled to an input line within a load center, the system comprising a plurality of current transformers, each configured to be coupled to one of the plurality of circuit branches and to produce a signal having a level related to a current level of the one of the plurality of circuit branches, a plurality of sensor circuits, each coupled to an associated one of the plurality of current transformers, and configured to convert the signal from the associated one of the plurality of current transformers to a digital measurement signal, a concentrator configured to receive the digital measurement signals and transmit data related to the digital measurement signals to an external client, and means for providing the digital measurement signals from the plurality of sensor circuits to the concentrator over a bus. 
         [0038]    According to one embodiment, the concentrator is further configured to be located within the load center. According to another embodiment, the system further comprises a wireless radio coupled to the concentrator, wherein the wireless radio is configured to transmit the data related to the digital measurement signals to an external client. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0039]    The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various FIGs. is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
           [0040]      FIG. 1  is a circuit diagram of a load center in accordance with aspects of the present invention; 
           [0041]      FIG. 2A  is a schematic diagram of a smart CT prior to being coupled to a circuit branch in accordance with aspects of the present invention; 
           [0042]      FIG. 2B  is a schematic diagram of a smart CT after being coupled to a circuit branch in accordance with aspects of the present invention; 
           [0043]      FIG. 3A  is a schematic diagram of a smart CT prior to being coupled to a communication bus in accordance with aspects of the present invention; 
           [0044]      FIG. 3B  is a schematic diagram of a smart CT after being coupled to a communication bus in accordance with aspects of the present invention; 
           [0045]      FIG. 3C  is a schematic diagram of a smart CT locked together with a communication bus in accordance with aspects of the present invention; 
           [0046]      FIG. 4  is a circuit diagram of smart CT&#39;s coupled to a daisy chain bus in accordance with aspects of the present invention; 
           [0047]      FIG. 5  is a block diagram of a concentrator in accordance with aspects of the present invention; and 
           [0048]      FIG. 6  is a flow chart of a method of operation of a CT concentrator in accordance with aspects of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    Embodiments of the invention are not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Embodiments of the invention are capable of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing”, “involving”, and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
         [0050]    As discussed above, CT&#39;s may be utilized with a load center of an electrical supply system to monitor circuit branches and assist in providing efficient energy management. For instance, CT&#39;s may be coupled to circuit branches inside or outside of a load center. However, multiple challenges with CT&#39;s may arise as the electrical supply system grows in size and complexity. 
         [0051]    Existing methods and systems typically rely on a system of individual CT&#39;s, each connected to a main controller and measurement unit in a “hub and spoke” topology. In such a system, each CT requires dedicated cabling connecting it to the main controller and its measurement unit, so that the number of cables or wires increases linearly with the number of sensors. In addition, some jurisdictions have regulatory requirements on the amount of “gutter space” (i.e., space within the panelboard free of wiring and other electronic devices) available within a panelboard. Therefore, as the number of CT&#39;s increases, the amount of cabling and circuitry within a panelboard may become difficult to manage and violate regulatory requirements. 
         [0052]    In some instances it may even be difficult to physically place all of the desired CT&#39;s and corresponding circuitry within the load center, and due to the complexity of such a load center; installation, expansion and maintenance may also be expensive, difficult and even hazardous. 
         [0053]    At least some embodiments described herein overcome these problems and provide a relatively small, less complex and more manageable method and system for utilizing CT&#39;s to monitor circuit branches of a load center. 
         [0054]      FIG. 1  shows a load center  100  that includes a system for monitoring subsidiary circuit branches  102  of the load center  100  according to one embodiment of the current invention. The load center  100  includes a housing  101 . Within the housing  101 , the load center  100  includes a first input power line  104 , a second input power line  106 , a plurality of circuit branches  102 , a neutral line  108 , and a ground connection  110 . The first and second input power lines  104 ,  106  are each configured to be coupled to an external power source (e.g., a utility power system) (not shown). Each one of the plurality of circuit branches  102  is configured to be coupled between one of the input power lines  104 ,  106  and an external load  112  (e.g., an appliance, a power outlet, a light etc.). According to one embodiment, each one of the input power lines  104 ,  106  includes a circuit breaker  113  coupled between the input power line  104 ,  106  and circuit branches  102 . According to another embodiment, each one of the plurality of circuit branches  102  includes a circuit breaker  115  coupled between the input power line  104 ,  106  and an external load  112 . In one embodiment, the current rating of each of the circuit breakers  113 ,  115  may be configured based on the power required by the external load  112  to which the circuit breakers  113 ,  115  associated circuit branch  102  is coupled. The neutral line  108  is coupled to the ground connection  110 . According to one embodiment, the neutral line is coupled to the ground connection  110  via a neutral bus bar  116 . According to another embodiment, the ground connection  110  is coupled to the neutral line  108  via a ground bus bar  118 . 
         [0055]    Within the housing  101 , the load center  100  also includes a plurality of Current Transformers (CT)  114 , a plurality of smart sensor circuits  120 , a communication bus  122 , and a CT concentrator  124 . According to one embodiment, the communication bus  122  includes a plurality of wires. For example, in one embodiment, the communication bus  122  is a ribbon cable including 4 wires (a power line, a return line, D+ differential pair line, D− differential pair line); however, in other embodiments, the communication bus  122  may include any number and type of wires. Each one of the plurality of CT&#39;s  114  is coupled to at least one of the plurality of circuit branches  102 . According to one embodiment, CT&#39;s  114  may also be coupled to each input line  104 ,  106 . According to one embodiment, each CT  114  encompasses a corresponding circuit branch  102  or input line  104 ,  106 . Each one of the plurality of CT&#39;s is also coupled to a corresponding smart sensor circuit  120 . Each smart sensor circuit  120  is coupled to the communication bus  122 . 
         [0056]    According to one embodiment, each smart sensor circuit  120  is connected to the communication bus  122  so that each smart sensor circuit  120  is in electrical communication with the CT concentrator  124 . In one embodiment, each smart sensor circuit  120  is clamped onto the communication bus  122 . For example, in one embodiment, electrical contacts (not shown) of a smart sensor circuit  120  are pressed onto the communication bus  122  so that the electrical contacts pierce an insulation layer of the communication bus  122  and become electrically coupled to appropriate conductors within the communication bus  122 . In other embodiments, the smart sensor circuits  120  may be coupled differently to the communication bus  122 . For example, according to one embodiment, the smart sensor circuits  120  may be coupled to the communication bus  122  via a bus bar or daisy chained connectors (not shown). The connection of smart sensor circuits  120  to the communication bus  122  is discussed in greater detail below. 
         [0057]    According to one embodiment, the CT concentrator  124  includes a digital interface  125 , at least one analog interface  127 , a power module  126  and a Zigbee RF interface  128 . The communication bus  122  is coupled to the digital interface  125 . The power module  126  is coupled to at least one input power line  104 ,  106  via at least one branch circuit  102 . According to one embodiment (not shown), at least one CT  114  is coupled directly to at least one analog interface  127 . 
         [0058]    According to one embodiment, AC power is provided from an external source (e.g., a utility power system) to the input lines  104 ,  106 . AC power from the input lines  104 ,  106  is provided to each of the external loads  112 , via the circuit branches  102 . The circuit breakers  113  are configured to automatically open and prevent current in an input line  104 ,  106  if an overload or short circuit is detected in the input line  104 ,  106 . The circuit breakers  115  are configured to automatically open and prevent current in a circuit branch  102  if an overload or short circuit is detected in the circuit branch  102 . 
         [0059]    The power module  126  of the CT concentrator  124  receives AC power from at least one input line  104 ,  106 . Using the AC power, the power module  126  powers the CT concentrator  124 . In addition, the CT concentrator  124  measures the AC voltage, frequency and/or phase of the AC power. According to one embodiment, the CT concentrator  124  is configured to communicate the measured AC voltage, frequency and/or phase information to the smart sensor circuits  120 , via the communication bus  122 . For example, in one embodiment, the CT concentrator  124  transmits phase information of the AC power to the smart sensor circuits  120  so that the CT concentrator  124  may be synchronized with the smart sensor circuits  120 . The synchronization of the CT concentrator  124  with the smart sensor circuits  120  will be discussed in greater detail below. According to one embodiment, the CT concentrator is also capable of being powered by a battery. 
         [0060]    AC current passing through a circuit branch  102  or input line  104 ,  106  induces a proportionate AC current in its associated CT  114  which encompasses the circuit branch  102  or input line  104 ,  106 . According to one embodiment, where a CT  114  may be coupled to multiple circuit branches  102 , an AC current proportionate to the combined current in the multiple circuit branches is induced in the CT  114  which encompasses the multiple circuit branches. 
         [0061]    The smart sensor circuit  120  coupled to the CT  114  converts the proportionate AC current from the CT  114  into a digital value and then transmits the digital value, over the communications bus  122  to the CT concentrator  124 . In addition, the smart sensor circuit  120  may be configured to utilize the voltage, frequency and/or phase information received from the CT concentrator  124  over the communications bus  122 . For example, in one embodiment, the smart sensor circuit  120  utilizes the phase information received from the CT concentrator  124  to synchronize operation with the CT concentrator  124  such that current measurements performed by the smart sensor circuits  120  can by synchronized with voltage measurements made by the CT concentrator  124 . In another example, the smart sensor circuit  120  utilizes the voltage, frequency and/or phase information to calculate power and energy parameters such as RMS current, true and apparent power, and power factor of the circuit branch  102  or input line  104 ,  106 . This information is also converted into digital values and sent to the digital interface  125  of the CT concentrator  124  over the communications bus  122 . According to one embodiment, at least one CT  114  may also provide analog signals, proportionate to the AC current passing through the circuit branch  102 , directly to an analog interface  127  of the CT concentrator  124 . 
         [0062]    According to one embodiment, upon receiving the current information from the smart sensor circuits  120 , the CT concentrator  124  utilizes the measured voltage, frequency and/or phase information to calculate power and energy parameters such as RMS current, true and apparent power, and power factor of the circuit branch  102  or input line  104 ,  106 . 
         [0063]    According to one embodiment, upon receiving the current information and receiving and/or calculating the power information, the CT concentrator  124  transmits the current, power and energy information to an external client (e.g., a web server, in-home display, internet gateway etc.) via the wireless Zigbee RF interface  128  to assist in power management of the load center  100  and to assist in power management and control of a residence or other facility containing the system. The CT concentrator  124  may also transmit the current, power and energy information to an external client via a wired connection or a different type of wireless connection. 
         [0064]    By including a single communication bus  122  to which all smart sensor circuits  120  are coupled, a relatively small, less complex and more manageable method and system for utilizing a plurality of CT&#39;s  114  to monitor circuit branches  102  of a load center  100  is provided. 
         [0065]      FIGS. 2A and 2B  illustrate one embodiment of the process of coupling a CT  114  to a circuit branch  102 . According to one embodiment, a housing  205  includes a CT  114  and a smart sensor circuit  120  enclosed therein. In one embodiment, a first portion  214  of the housing  205  includes a CT  114  and a second portion  216  includes a smart sensor circuit  120 .  FIG. 2A  illustrates the first portion  214  prior to being coupled to a circuit branch  102  and  FIG. 2B  illustrates the first portion  214  after being coupled to a circuit branch  102 . 
         [0066]    The first portion  214  is coupled to the second portion  216  via a hinge  206 . The second portion  216  includes a button  202  coupled to a lever  204 . Prior to the first portion  214  being coupled to the circuit branch  102 , the lever  114  is in an upward position, allowing the first portion  214  to swing away from the second portion  216  and create an opening  208  by which a circuit branch  102  may be inserted. When connection to a circuit branch  102  is desired, a user may configure the first portion  214  so that the circuit branch  102  is inserted through the opening  208  into an interior chamber  209 . The user may then press down on the button  202 , causing the lever  204  to move in a downwards direction. The lever  204  presses against an outside portion  210  of the first portion  214 , causing the first portion  214  to swing towards the second portion  216  and capture the circuit branch  102  within the interior chamber  209  of the first portion  214 . According to other embodiments, the first portion  214  may be connected to the circuit branch  102  differently. For example, the first portion  214  may be manually placed around the circuit branch  102 . As discussed above, after the circuit branch  102  is encompassed by the first portion  214  (and hence also the CT  114 ), an AC current in the circuit branch  102  will produce a proportionate AC current within the CT  114 . 
         [0067]      FIGS. 3A ,  3 B and  3 C illustrate the process of coupling the second portion  216  to a communications bus  122 .  FIG. 3A  illustrates the second portion  216  prior to being connected to a communications bus  122 .  FIG. 3B  illustrates the second portion  216  after being connected to a communication bus  122 .  FIG. 3C  illustrates the second portion  216  locked together with a communications bus  122 . According to one embodiment, the second portion  216  includes an Insulation Displacement Connector (IDC)  302  (e.g., an AVX series 9176 IDC). According to one embodiment, the IDC  302  may include a plurality of blades  304 . For example, if, as discussed above, the second portion  216  (and hence the smart sensor circuit  120 ) is configured to be coupled to a four-wire ribbon cable, the IDC  302  will include four blades, each blade configured to be coupled to a corresponding conductor within the cable. However, according to other embodiments, the IDC  302  may include any number of blades to adequately connect the smart sensor circuit  120  to the communications bus  122 . 
         [0068]    The second portion  216  may also include a locking lid  306  coupled to the second portion  216  via a hinge  308 . Prior to being coupled to the communications bus  122 , the locking lid  306  of the second portion  216  is swung away from the IDC  302 , allowing a user to place the communication bus  122  adjacent to the IDC  302 . The user presses down on the communication bus  122 , causing the communication bus  122  to press against the IDC  302 . The plurality of blades  304  of the IDS  302  pierce the outer insulation layer  310  of the communication bus  122 , each one of the plurality of blades  304  connecting with a corresponding conductor within the communication bus  122 . The user may then swing the locking lid towards the IDC  302  and press down on the locking lid to lock the communication bus  122  into place. According to other embodiments, the second portion  216  (and hence the smart sensor circuits  120 ) may be coupled to the communication bus  122  in a different manner. For example, smart sensor circuits may also be coupled to the communication bus  122  via a bus bar. Upon being coupled to the communication bus  122 , the smart sensor circuit  120  is in electrical communication with the CT concentrator  124 . 
         [0069]      FIG. 4  is a circuit diagram of a plurality of CT&#39;s  114  and smart sensor circuits  120  coupled to a communication bus  122 . Each CT  114  is coupled to a circuit branch  102 , or input line  104 ,  106 , as discussed above. For example, in one embodiment each CT  114  is configured to encompass a circuit branch  102 , or input line  104 ,  106 , as discussed in relation to  FIGS. 2A and 2B . Each smart sensor circuit  120  is coupled to a communication bus  122  as discussed above. According to one embodiment, the communication bus  122  may be a 4-wire ribbon cable including a power line  122   d , a D− differential pair line  122   c , a D+ differential pair line  122   b , and a return (ground) line  122   a . In one embodiment, the communication bus  122  is a RS-485 bus; however, according to other embodiments, a different type of bus may be used. 
         [0070]    Each smart sensor circuit  120  includes a microcontroller  402 . In one embodiment, the microcontroller  402  is a low power microcontroller (e.g., an STM8 low power microcontroller). According to one embodiment, the microcontroller  402  includes an analog interface  404 , a reference interface  406 , a power interface  408 , a return interface  410 , a transmission interface  412  and a reception interface  414 . According to one embodiment, the power interface  408  is coupled to the power line  122   d  and the return interface  410  is coupled to the return line  122   a . In this way, each smart sensor circuit  120  is powered by the communication bus  122 . According to another embodiment, each CT  114  is coupled in parallel between the analog interface  404  and the reference interface  406 . In one embodiment, each smart sensor circuit  120  also includes a burden resistor  415  coupled in parallel between the analog interface  404  and the reference interface  406 . 
         [0071]    Each smart sensor circuit  120  also includes a transceiver  403  (e.g., an RS-485 Transceiver). According to one embodiment, the transceiver  403  includes a first diode  416  coupled between the transmission interface  412  and the communication bus  122 , and a second diode  418  coupled between the reception interface  414  and the communication bus  122 . Also, in one embodiment, the transceiver  403  is coupled in parallel between the power  122   d  and return  122   a  lines. 
         [0072]    As discussed previously, AC current  416  in the circuit branch  102  or input line  104 ,  106  to which a CT  114  is coupled, will produce a proportionate AC current  418  in the CT  114 . The burden resistor  415  converts the proportionate AC current  418  into a proportionate AC voltage. Via the analog interface  404 , the microcontroller  402  receives the proportionate AC voltage and converts the proportionate AC voltage into a digital value. The microcontroller  402  then provides the digital value to the transmission line  122   b  via the transmission interface  412  and transceiver  403 , and transmits the digital value over the communication bus  122  to the CT concentrator  124 . In addition, the microcontroller  402  is configured to receive voltage, frequency and/or phase information from the CT concentrator  124 , via the reception line  122   c , the transceiver  403  and the reception interface  414 . As discussed above, the microcontroller  402  may use the additional voltage, frequency and/or phase information received from the CT concentrator  124  along with the received proportionate AC current  418  to calculate power and energy parameters of the circuit branch  102  or input line  104 ,  106  such as RMS current, true and apparent power, and power factor. This information may also be converted into digital values and transmitted to the CT concentrator  124  via the transmission interface  412 , the transceiver  403  and the transmission line  122   b . In one embodiment, the microcontroller  402  may also use the phase information received from the CT concentrator  124  to synchronize current measurements in the smart sensor circuits  120  with voltage measurements in the CT concentrator  124   
         [0073]      FIG. 5  is a block diagram of a CT concentrator  124 . As discussed above, the CT concentrator  124  has a digital interface  125  coupled to the communication bus  122 . The communications bus is coupled to a plurality of smart sensor circuits  120  and a plurality of CT&#39;s  114 . 
         [0074]    According to one embodiment, the CT concentrator  124  includes a power module  126 . In one embodiment, the power module  126  includes a single-phase power interface  502  configured to be coupled to a single-phase power supply. In another embodiment the power module  126  includes a three-phase power interface  504  configured to be coupled to a three-phase power supply. For example, the three-phase power interface  504  may be configured to receive power from a 3-phase delta or wye power connection. It is to be appreciated that the power supply coupled to the single-phase  502  or three-phase  504  interface is the same power supply coupled to the input lines  104 ,  106  and as described in relation to  FIG. 1 . Accordingly, power received by the power module  126  is substantially the same as power being provided to the circuit branches  102 . 
         [0075]    According to one embodiment, the power module  126  also includes a DC interface  506 , a sensor interface  508  and an extra pin interface  510 . According to one embodiment, the extra pin interface  510  includes four additional pins (e.g., a transmission pin, a reception pin, a power module type pin and an auxiliary power pin). However, in other embodiments, the extra pin interface  510  may include any number and type of pins. According to another embodiment, the CT concentrator  124  may also include a battery pack  512  having a DC interface  514 . In one embodiment, the power module  126  and/or battery pack  512  is modular and may be removed from the CT concentrator  124 . 
         [0076]    According to one embodiment, the CT concentrator  124  includes a first DC interface  516  configured to be coupled to the DC interface  514  of the battery pack  512 , a second DC interface  518  configured to coupled to the DC interface  506  of the power module  126 , a sensor interface  520  configured to be coupled to the sensor interface  508  of the power module  126 , and an extra pin interface  522  configured to be coupled to the extra pin interface  510  of the power module  126 . The extra pin interface  522  includes four additional pins (e.g., a transmission pin, a reception pin, a power module type pin and an auxiliary power pin). However, in other embodiments, the extra pin interface  522  may include any number and type of pins. 
         [0077]    The first  516  and second  518  DC interfaces are coupled to a power management module  524 . The power management module  524  is coupled to a microcontroller  528 . The sensor interface  520  and the extra pin interface  522  are coupled to the microcontroller  528 . The CT concentrator  124  also includes a transceiver  530  coupled between the digital interface  125  and the microcontroller  528  and a non-volatile memory module  532  coupled to the microcontroller  528 . In one embodiment, the non-volatile memory module  532  includes Electrically Erasable Programmable Read-Only Memory (EEPROM); however, in other embodiments, the non-volatile memory module  532  may include any type of non-volatile memory (e.g., such as serial Flash memory). 
         [0078]    The CT concentrator  124  also includes a user interface  534  coupled to the microcontroller. In some embodiments, the user interface may include any type of controls which allows a user to interface with the CT concentrator  124 . (e.g., such controls include switches, buttons, LED&#39;s etc.). According to one embodiment, the CT concentrator  124  also includes a USB port  536  and a serial port  538 . 
         [0079]    The CT concentrator  124  also includes a wireless radio module and antenna  540 . In one embodiment, the wireless radio module is a ZigBee radio; however, in other embodiments, the wireless radio module  540  may be configured using a different wireless standard. According to one embodiment, the wireless radio and antenna  540  is coupled to the microcontroller  528 , an On/Off switch  542 , and a serial memory module  544 . 
         [0080]    The power module  126  receives AC power from a power source (e.g., a single-phase or three phase power source) (not shown), modulates and converts the received AC power to DC power, and provides DC power to the CT concentrator  124  via the DC interface  506  and the second DC interface  518 . The power management module  524  receives the DC power from the second DC interface  518  and provides appropriate DC power to components of the CT concentrator  124  (e.g., the microcontroller  528 ). According to another embodiment, the battery pack  512  may provide DC power to the CT concentrator  124  via the DC interface  514  and the first DC interface  516 . The power management module  524  receives the DC power from the first DC interface  516  and provides appropriate DC power to components of the CT concentrator  124  (e.g., the microcontroller  528 ). 
         [0081]    The power module  126  provides power signals received from the power source (e.g., single-phase or three-phase source) to the microcontroller  528  via the sensor interfaces  508 ,  520 . In one embodiment, the power signals include a voltage sense signal and a phase synchronization signal. According to another embodiment, the power module  126  also provides additional information to the microcontroller via the extra pin interfaces  510 ,  522 . For example, additional information may be provided to the microcontroller via a transmission pin, a reception pin, a power module type pin and an auxiliary power pin. 
         [0082]    The microcontroller  528  receives the power signal information from the power module  126 , via the sensor interface  520 . The microcontroller  528  measures the voltage, frequency and phase of the power being provided to the power module  126 . It is to be appreciated that as the power provided to the power module  126  is substantially the same as power provided to the circuit branches  102  (as discussed above), the voltage, frequency and phase measured by the microcontroller  528  in relation to the power module  126  is the same as the voltage, frequency and phase of the power being provided to the circuit branches  102 . 
         [0083]    Upon being powered, the microcontroller  528  begins to communicate with the smart sensor circuits  120  via the transceiver  530 , the digital interface  125  and the communication bus  122 . According to one embodiment, the microcontroller  528  may utilize the RS-485 physical communication protocol to communicate over the communication bus  122 . However, other physical communication protocols may be used. The microcontroller  528 , which acts as the primary controller, identifies which smart sensor circuits  120  are coupled to the communication bus  122 . The primary microcontroller  528  treats the microcontrollers  402  as secondary controllers and assigns each secondary microcontroller  402  (and hence smart sensor circuit  120 ) a unique address. According to one embodiment, each time a new smart sensor circuit  120  is coupled to the communication bus  122 , it is assigned a new address by the primary microcontroller  528 . 
         [0084]    According to one embodiment, the primary microcontroller  528  utilizes the Modbus serial communication protocol to define the communication and addressing on the communication bus  122 . The primary microcontroller  528 , using the Modbus protocol, assigns unique addresses to the smart sensor circuits  120  and sets the structure and format of the data that is transmitted over the communication bus  122 . For example, according to one embodiment, communication over the communication bus  122  using the Modbus protocol may be performed as described in U.S. patent application Ser. No. 13/089,686 entitled “SYSTEM AND METHOD FOR TRANSFERRING DATA IN A MULTI-DROP NETWORK”, filed on Apr. 19, 2011, which is herein incorporated by reference in its entirety. In one embodiment, the primary microcontroller  528  utilizes an auto addressing scheme. For example, the primary microcontroller  528  utilizes an auto addressing scheme as described in U.S. patent application Ser. No. 13/089,678 entitled “SYSTEM AND METHOD FOR AUTOMATICALLY ADDRESSING DEVICES IN A MULTI-DROP NETWORK”, filed on Apr. 19, 2011, which is herein incorporated by reference in its entirety. 
         [0085]    According to one embodiment, the Modbus protocol allows for up to  255  smart sensor circuits  120  to be simultaneously attached to the communication bus  122 . It also is to be appreciated that the number of smart sensor circuits  120  may be limited by the load center  100  itself. For example, in common residential load centers, the maximum number of branch circuits (and hence smart sensor circuits) is seventy-two. However, according to at least one embodiment, different communication protocols may be used by the primary  528  and secondary  402  microcontrollers to allow any number of smart sensor circuits  120  to be coupled to the communication bus  122  (e.g., for use in large, commercial load centers). 
         [0086]    According to one embodiment, once all of the smart sensor circuits  120  have been identified and assigned addresses by the primary microcontroller  528 , a user, via the user interface  534 , may associate each smart sensor circuit  120  with a specific load (e.g., sensor # 12  is assigned to an air conditioner; sensor # 13  is assigned to a Refrigerator, etc.). 
         [0087]    Once the identification and addressing of the smart sensor circuits  120  is complete, the primary microcontroller  528  monitors the smart sensor circuits  120 . The primary microcontroller  528  determines which smart sensor circuits  120  are attempting to communicate over the communication bus  122  and controls communication on the bus  122  to eliminate conflicts or data collision. In addition, according to one embodiment, the primary microcontroller  528  provides power parameter information to the smart sensor circuits  120 . For example, as discussed above, the primary microcontroller  528  measures the voltage, frequency and phase of the power being provided to the power module  126  (and hence the circuit branches  102 ). When needed by a smart sensor circuit  120 , the primary microcontroller  528  transmits the parameter information to the smart sensor circuit  120 , via the transceiver  530  and communication bus  122 . 
         [0088]    As discussed above, each smart sensor circuit  120  measures the current through an associated circuit branch  102  or input line  104 ,  106 . According to one embodiment, using the measured current and the received additional parameter (e.g., voltage, frequency and phase) information from the primary microcontroller  528 , a smart sensor circuit  120  calculates power information such as RMS current, true and apparent power, and power factor of the associated circuit branch  102  or input line  104 ,  106 . The calculated current and/or power information is transmitted to the primary microcontroller  528 , via the communication bus  122 , digital interface  125 , and transceiver  530 . In one embodiment, the power information is transmitted to the primary microcontroller  528  at a time and rate determined by the microcontroller  528 . As discussed above, according to one embodiment, the primary microcontroller  528  may also receive analog current information directly from a CT  114 , via an analog interface  127 . 
         [0089]    According to one embodiment, upon receiving the calculated current from the smart sensor circuits  120 , the primary microcontroller  528  utilizes the measured voltage, frequency and/or phase information to calculate power and energy parameters such as RMS current, true and apparent power, and power factor of the circuit branch  102  or input line  104 ,  106 . 
         [0090]    The current, power and energy information is provided to the wireless radio module and antenna  540  by the primary microcontroller  528 . The wireless radio module and antenna  540  wirelessly transmits the current, power and energy information to an external client (e.g., a web server, in-home display, or internet gateway) to provide electric power and energy consumption data to end users or other interested parties. According to one embodiment, the current, power and energy information may also be provided to an external client through a wired connection (e.g., via the USB port  536  or serial port  538 ). According to another embodiment, the current, power and energy information may be provided to an external client through another type of interface, such as en Ethernet or Power Line Communication (PLC) port (not shown). 
         [0091]    In one embodiment described above, each smart sensor circuit  120  determines power information for its associated branch circuit and transmits the information to the CT concentrator  124 . In another embodiment, which will now be described with reference to  FIG. 6 , the CT concentrator  124  synchronizes current measurements by each smart sensor circuit  120  with voltage measurements performed by the CT concentrator  124 . This allows the CT concentrator  124  to calculate power information based only on current information received from the smart sensor circuits  120 . 
         [0092]      FIG. 6  is a flow chart of a method of operation of the CT concentrator  124  of  FIG. 5 , according to one embodiment. At block  602 , the CT concentrator  124 , and hence the smart sensor circuits  120 , are powered up. At block  604 , the primary microcontroller  528  of the CT concentrator assigns unique addresses to each smart sensor circuit  120 , via the communications bus  122 . According to one embodiment, the primary microcontroller  528  utilizes an auto addressing scheme, as discussed above. At block  606 , the primary microcontroller  528  broadcasts parameter information to each smart sensor circuit  120 , via the communication bus  122 . According to one embodiment, the parameter information includes at least one of frequency (or period), the number of samples per period, and a defined sleep timer. In another embodiment, the broadcast information includes scaling parameters. According to another embodiment, the broadcast information includes previous cycle computation results (e.g., for RMS current, power, energy). 
         [0093]    At block  608 , the primary microcontroller  528  requests each smart sensor circuit  120  to acknowledge the receipt of the broadcast information via the communication bus  122 . According to one embodiment, at block  608 , the primary microcontroller  528  also requests that each smart sensor circuit  120  transmit its sensor type (e.g., 20A, 80A, or 200A current transformer) to the primary microcontroller  528  via the communication bus  122 . At block  610 , the primary microcontroller  528  creates an inventory of all of the sensor circuits  120  and their type (e.g., by model number). At block  612 , the primary microcontroller  528  transmits to each smart sensor circuit  120  that the smart sensor circuit  120  should enter power save mode. 
         [0094]    According to one embodiment, once a smart sensor  120  enters power save mode, a sleep timer is enabled. In one embodiment, the use of the sleep timer is intended to limit the overall power consumption of the system. For example, in one embodiment, when a smart sensor  120  is in power save mode, the smart sensor  120  will not communicate on the communication bus, and hence will require a lower level of power, until the sleep timer has expired. By placing at least a portion of the smart sensors  120  in power save mode, the total number of smart sensors  120  requiring full power is limited and the total power consumption of the system may be reduced. According to one embodiment, the sleep timer is programmable. In one embodiment, the sleep timer is configured with a time equal to slightly less than the total number of smart sensors  120  multiplied by the period over which current is to be sampled. 
         [0095]    For example, according to on embodiment, the sleep timer is configured with a time (T) calculated with the following formula: 
         [0000]        T =( s− 2)* t +( t/ 2); 
         [0000]    where: 
         [0096]    s represents the total number of smart sensors  120 , and 
         [0097]    t represents the sample period defined by the primary microcontroller  528 . 
         [0098]    In one example, where the sample period is 20 ms and the system includes a total of 6 smart sensors  120 , the time T is calculated as 90 ms. In this example, after a smart sensor  120  has conducted measurements and finished transmitting current sample raw data, it will enter power save mode for 90 ms and will not sample current again until time T (90 ms) has expired. However, in other embodiments, the sleep timer may be configured differently. 
         [0099]    In one embodiment, smart sensors  120  currently in power save mode are configured to exit power save mode early (i.e., before the expiration of time T), to prepare for current sampling which will begin upon the expiration of time T. For example, in one embodiment, smart sensors  120  currently in power save mode are configured to exit power save mode 10 ms early. In such an embodiment, the total time each smart sensor  120  will be awake is 30 ms (20 ms period in addition to 10 ms awakening period). Hence, by staggering the current sampling performed by the smart sensors  120 , the number of smart sensors  120  requiring power at the same time is limited and as a result, the total power consumption of the system is reduced. This is particularly useful for battery operated systems. 
         [0100]    At block  614 , the primary microcontroller  528  senses the voltage, frequency and/or phase of the power signal information received from the power module  126  via the sensor interface  520 . For example, according to one embodiment, the primary microcontroller  528  senses voltage and/or frequency through a voltage sense signal and the primary microcontroller  528  senses phase through a phase synchronization signal. As discussed above, according to some embodiments, the power signal information received from the power module  126  may be correlated to single, double or 3-phase power. 
         [0101]    At block  616 , the primary microcontroller  528  computes the RMS voltage for all phases that are present (e.g., 1, 2, or 3). Also at block  616 , the primary microcontroller  528  compares the RMS voltage to the primary microcontroller&#39;s  528  nominal voltage to confirm that the RMS voltage and phase signal(s) are correct. For example, according to one embodiment, if the primary microcontroller  528  is connected to a utility system in North America, the primary microcontroller  528  will confirm that it is measuring a 120V, 60 Hz signal. However, in another embodiment, if the primary microcontroller  528  is connected to a utility system in Europe, the primary microcontroller  528  will confirm that it is measuring a 220V, 50 Hz signal. 
         [0102]    At block  618 , the primary microcontroller  528  determines the appropriate phase angle at which synchronized measurements will be taken. According to one embodiment, the phase angle may be configured as any phase angle, and does not have to be limited to a zero crossing. In some embodiments, the phase angle may be configured at an angle other than at a zero crossing to intentionally avoid noise which may exist at the zero crossing. 
         [0103]    At blocks  620  and  622 , synchronized sampling by the primary microcontroller  529  and the smart sensor circuits  120  begins at the previously determined phase angle. For example, according to one embodiment, at block  620 , the primary microcontroller  528  communicates to all of the smart sensor circuits  120  simultaneously to start sampling current in their respective circuit branches  102  at the predetermined phase angle. Also, at the same time as block  620 , the primary microcontroller  528  at block  622  initiates voltage sampling of the power signal information received from the power module  126  at the previously determined phase angle to synchronize the voltage measurements with the current measurements made by all of the smart sensor circuits  120 . According to one embodiment, the primary microcontroller  528  samples voltage over the same period of time in which the smart sensor circuits  120  sample current. 
         [0104]    According to another embodiment, instead of communicating to all of the smart sensor circuits  120  simultaneously, the primary microcontroller  528  communicates to at least one specific sensor (e.g., a sensor having a unique address) to begin sampling current in the respective circuit branch  102 . In this way, the primary microcontroller  528  is able to start sampling current in at least one specific type of circuit branch (e.g., a circuit branch coupled to a specific type of load). By only sampling current in a select number of circuit branches  102 , the overall power consumption of the system may be reduced. 
         [0105]    According to one embodiment, each smart sensor circuit  120  which is controlled to begin sampling will sample current in the smart sensor circuits  120  respective branch over a predefined period of time for a predefined number of samples, the time and number of samples being previously set by the primary microcontroller  528  in the broadcast parameter information. In one embodiment, the current sampling raw data is stored in a buffer of each smart sensor circuit  120 . 
         [0106]    At block  624 , upon completing voltage sampling for the given period, the primary microcontroller  528  requests that each smart sensor circuit that was sampling current, transmit the current sampling raw data for the given time period from the buffer to the primary microcontroller  528  via the communication bus  122 . According to one embodiment, the current sampling raw data is time-stamped. 
         [0107]    At block  626 , upon confirming receipt of the current sampling raw data, the primary microcontroller  528  broadcasts to the previous current sampling smart sensors  120  that the smart sensors  120  should enter power save mode, making more power available for other smart sensors (as discussed above). 
         [0108]    According to one embodiment, at block  626 , using the received current data and measured voltage data, the primary microcontroller  528  calculates the RMS current, power (e.g., 4 quadrant) and/or energy usage of the circuit branches  102  associated with the smart sensors  102  from which the primary microcontroller  528  received the raw current sampling data. According to one embodiment, the primary microcontroller  528  may automatically take into account any communication delay between the primary microcontroller  528  and the smart sensors  102  when making its current, power and/or energy calculations. After calculating the current, power and energy information, the primary microcontroller  528  may repeat blocks  620  to  628  for another smart sensor  120  or group of smart sensors  120 . 
         [0109]    In at least some embodiments, the use of the primary microcontroller  528  to individually control the synchronization of the smart sensor circuits  120 , eliminates any need to individually wire each smart sensor circuit  120  with phase synchronization signals from the power module. Phase Locked Loop (PLL) circuitry within the smart sensor circuits  120  may also be eliminated, as the primary microcontroller  528  will control the synchronization. By allowing the primary microcontroller  528  to select the phase angle at which sampling will occur, the flexibility of the system may be increased. For example, any appropriate phase angle may be selected to provide the most desirable results. 
         [0110]    Even though examples in accordance with the present invention are described herein in reference to a load center, other examples may be utilized within any electrical system in which current, power and energy of a power line are desired to be monitored. It also is to be appreciated that examples in accordance with the present invention may be utilized to monitor any type (e.g., commercial or residential) or size system. 
         [0111]    Even though examples in accordance with the present invention are described herein as utilizing a current transformer  114  capable of being clamped onto a circuit branch  102 , other examples may utilize a different type of current sensor. For example, current sensors utilizing shunt resistance, hall-effect, and toroidal (solid core) current transformers may be used. 
         [0112]    In at least some examples in accordance with the present invention described herein communication between the sensor circuits  120  and the CT concentrator  124  is conducted over a wired interface (i.e. the communication bus  122 ). Other examples may utilize a wireless interface. For example, communication between the sensor circuits  120  and the CT concentrator  124  may be performed in compliance with a wireless standard such as the ZigBee RF4CE standard or the IEEE 802.15 standard as described in U.S. patent application Ser. No. 12/789,922 entitled “SYSTEM FOR SELF-POWERED, WIRELESS MONITORING OF ELECTRICAL CURRENT, POWER AND ENERGY”, filed on May 28, 2010, which is herein incorporated by reference in its entirety. 
         [0113]    By including only a single communication bus within a load center, rather than individual dedicated connections (e.g., “hub and spoke wiring”), and connecting all smart CT&#39;s to a CT concentrator within the load center via the single communication bus; a relatively small, less complex and more manageable method and system for utilizing a plurality of CT&#39;s to monitor circuit branches of a load center is provided. 
         [0114]    Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.