Abstract:
The present invention relates generally to detecting energy theft within an energy distribution system and more particularly to systems and methods for detecting energy discrepancies in voltages and/or currents reported by electric meters present in a distribution circuit, without requiring installation of additional hardware at the transformer. Typically, the location of each of at least two meters is determined with respect to a transformer. The line resistances within the distribution circuit are determined starting with a line resistance farthest from the transformer. Estimated line voltages are determined for at least one electric meter using the estimated line resistances, and the estimated voltages are compared to actual voltage readings for the at least one electric meter. The existence of line loss is determined based on this comparison.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims benefit of similarly titled U.S. provisional patent application Ser. No. 61/382,057 filed Sep. 13, 2010, which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to detecting energy theft within an energy distribution system. More particularly, the present invention relates to systems and methods for detecting energy discrepancies in voltages and/or currents reported by different electric meters present in a distribution circuit, without requiring installation of additional hardware at the transformer. 
     BACKGROUND OF THE INVENTION 
     Electricity theft is a problem that all electric utilities face. In fact, it is estimated that energy theft costs utilities billions of dollars annually, and these losses generally are passed along to customers in the form of higher rates. Unfortunately, electricity theft via fraud (meter tampering) or stealing (illegal connections) can also create situations that endanger lives and property. 
     An existing system and process for detecting energy theft includes first installing a meter at a distribution transformer. Energy theft is then detected if the energy measured at the transformer is greater than the aggregated energy reported by the electric meters installed at the different premises connected to the distribution transformer. This method is effective, but requires installation and maintenance of an extra meter for each distribution transformer. 
     Accordingly, there is a need in the art for systems and processes that effectively detect or identify potential energy theft, without the need for additional hardware implementation beyond the hardware (e.g., electric meters) installed at customer premises. 
     SUMMARY OF THE INVENTION 
     The exemplary embodiments herein describe a method that allows detection of energy theft solely based on the analysis of the information provided by the electric meters at the different customer premises connected to a transformer. The invention allows for such detection without the need for additional hardware installation. 
     In one aspect of the invention, a system is provided including a transformer, a first electric meter, and a second electric meter connected to a server. The first electric meter is connected to the transformer via a first electrical line, and the second electric meter is connected to the transformer via a second electrical line. The second electric meter is located a farther distance from the transformer than the first electric meter. The server determines the location of the first electric meter and the second electric meter with respect to the transformer. Once the location of the meters is determined, the server estimates the resistance along the electrical line located the farthest from the transformer (i.e., the second electrical line). The server may then calculate an expected voltage for the second electric meter based on the estimated resistance of the second electrical line. The server receives one or more actual voltage readings for the second electric meter and compares the expected voltage for the second electric meter with the one or more actual voltage readings for the second electric meter. The server can determine the existence of line loss along the second electrical line if there is a difference between the expected voltage and the actual voltage readings that is greater than a predetermined threshold. 
     In another aspect of the invention, the server may also estimate the resistance along the first electrical line. The server calculates an expected voltage for the first electric meter based on the estimated resistance of the second electrical line and the estimated resistance of the first electrical line. Actual voltage readings for the first electric meter are then received, and may be compared to the calculated expected voltage for the first electric meter. The server can determine the existence of line loss along the first electrical line if there is a difference between the expected voltage and the actual voltage readings that is greater than a predetermined threshold. 
     In yet another aspect of the invention, a process for detecting the existence of line loss in electric meters present in a distribution circuit is provided. The process includes determining, by a processor, the location of each of at least two meters with respect to a transformer of the distribution circuit, each of the meters in electrical communication with an electrical line. The process also includes estimating, by the processor, a resistance of the electrical line at the location of each of the at least two meters, starting with a line resistance farthest from the transformer. Once the resistances are estimated, the process continues by calculating estimated line voltages for at least one electric meter using the estimated line resistances. The process then includes receiving, by the processor, actual voltage readings for the at least one electric meter such that a comparison of the estimated line voltage with the actual voltage readings for the at least one electric meter may be made. Finally, the process includes determining, by the processor, the existence of line loss if one or more of the comparisons result in a difference that is greater than a predetermined threshold. 
     These and other aspects of the invention will be better understood by reading the following detailed description and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic showing an example of a residential distribution circuit with a representative three meters; 
         FIG. 2  is a simplified schematic of  FIG. 1 ; 
         FIG. 3  is a first subcircuit of the schematic of  FIG. 2 ; and 
         FIG. 4  is a second subcircuit of the schematic of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     All terms used herein are intended to have their ordinary meaning in the art unless otherwise provided. 
     An exemplary embodiment allows for energy theft detection in a distribution circuit. Typically, a distribution circuit carries electricity from a transmission system and delivers it to consumer locations. The distribution circuits described herein typically comprise a transformer, which reduces distribution voltage to the relatively low voltages (e.g., 1 kV) required by lighting and interior wiring systems. The transformer may be pole-mounted or set on the ground in a protective enclosure. In any event, the transformer is in electrical communication with any number of consumer locations via, for example, an “electrical service” or “service drop” connection (e.g., and electrical wire). Each consumer location typically comprises a meter to determine the amount of electricity consumed at the location. 
     In one embodiment, the inventive methods require that at least two electric meters are present in the distribution circuit. Moreover, instantaneous current and voltage information should be available from all the delivery points (e.g., meters) within the transformer. 
     Equivalent Circuit 
     An exemplary residential distribution circuit in is illustrated in  FIG. 1 . As shown, the circuit comprises a number of electric meters (M 1 , M 2 , and M 3 ), such as those that are typically employed in North America to measure electricity usage at a location (e.g., a home, apartment, other residence, office or the like). Each of the meters (M 1 , M 2 , and M 3 ) are adapted to report an instantaneous voltage (V 1 , V 2 , V 3 ) and instantaneous current (I 1   a , I 1   b , I 2   a , I 2   b , I 3   a , and I 3   b ) corresponding to instantaneous electricity usage at the location. Moreover, each of the meters may experience an aggregate load during such electricity usage, which may be represented in the circuit diagram, for example, by any number of resistors on both sides of the circuit (e.g., R 3   a , R 3   b , R 6   a , R 6   b , R 8   a , and R 8   b ). 
     The electricity distribution circuit is shown to experience a resistance along the main electricity distribution line. The resistance may be modeled or represented by any number of resistors (e.g., R 1   a , R 1   b , R 4   a  and R 4   b ). Additionally, the circuit experiences a resistance along each line feeding to the multiple locations, wherein such resistance may be represented by any number of resistors (e.g., R 2   a , R 2   b , R 5   a , R 5   b , R 7   a , and R 7   b ). 
     Referring to  FIG. 2 , the schematic of  FIG. 1  is shown in a simplified state, where it assumed that the resistances of the conductors for both sides of the circuit are equal (i.e., R 1   a =R 1   b , R 2   a =R 2   b , R 4   a =R 4   b , R 6   a =R 6   b , R 7   a =R 7   b ). As shown, each of the meters (M 1 , M 2 , and M 3 ) reports an instantaneous voltage (V 1 , V 2 , V 3 ) and instantaneous current (I 1 =I 1   a +I 1   b , I 2 =I 2   a +I 2   b , I 3 −I 3   a +I 3   b ) corresponding to instantaneous electricity usage at a location. The aggregate load experienced by each of the meters (M 1 , M 2 , and M 3 ) on both sides of the circuit (R 3 =R 3   a +R 3   b , R 6 =R 6   a +R 6   b , R 8 =R 8   a +R 8   b ) is shown simply as one resistor per meter. 
     The resistance seen along the main electricity distribution line is represented by resistors R 1  and R 4 , where R 1 =R 1   a =R 1   b  and R 4 =R 4   a =R 4   b . Finally, the resistance along each line feeding to the multiple premises, is represented by resistors R 2 , R 5 , and R 7 , respectively, where R 2 =R 2   a =R 2   b ; R 5 =R 5   a =R 5   b ; and R 7 =R 7   a =R 7   b.    
     The exemplary electricity distribution circuit shown in  FIG. 2  (and  FIG. 1 ) is a single-phase, 3-wire circuit attached to ANSI Form 4S or 4A meters. Other types of distribution circuits and meter forms are possible in North America and throughout the world, with the inventive methods described herein being applicable to most of them. For example, for three phase distribution circuits, one skilled in the art recognizes that the methods described herein with respect to the exemplary single-phase circuit would need to be repeated for each of the three phases. Further, since the current distribution circuit configuration in Europe need only support 220 V services, not both 110 V and 220 V services, a typical European distribution circuit is in fact equivalent to  FIG. 2 . 
     Data Analysis 
     Still referring to  FIG. 2 , the presence of non-measured energy in a distribution circuit creates discrepancies in the voltages and currents reported by the different electric meters (M 1 , M 2 , and M 3 ) present in the distribution circuit. It has been found that detection of these discrepancies provides a good indication of energy theft and can be used to trigger further investigation. 
     To enable this analysis, all meters (M 1 , M 2 , M 3 ) within a distribution circuit are configured to report instantaneous voltage (V 1 , V 2 , V 3 ) and current (I 1 , I 2 , I 3 ) samples periodically. For example, the meters may be programmed to report voltage and current readings at time intervals ranging from seconds to hours or even days. It will be appreciated that such samples may be manually determined or automatically determined. 
     To obtain snapshots in time of the different currents and voltages within the distribution circuit, all meters may be adapted to take their measurements simultaneously. Exemplary meters for use with the embodiments described herein are smart meters and retrofitted meters that include the necessary communications hardware and software including at least one microprocessor, radio, and memory. 
     Once the instantaneous voltage and current samples are procured, the analysis of the information may be completed in the following three steps: 
     1. Evaluation of the location of each meter within the distribution line 
     2. Evaluation of the resistance of the different lines 
     3. Verification of consistency in the reported voltages 
     In addition to circuitry and meters having the described measuring and reporting functionality, the system for performing the evaluation, verification and other steps of the data collection and analysis processes described herein includes at least a back-end processor programmed with software for implementing the processes. One skilled in the art recognizes that multiple processors, databases, servers, displays and the like may be used in various combinations to implement the invention. Additionally, meter data may be communicated to the back-end processor through wired, wireless or a combination of wired/wireless components and steps. 
     The methods described herein may be implemented within AMI, AMR, or Advanced Metering Management (AMM) technologies, including systems that measure, collect and analyze utility usage, from advanced devices such as electricity meters, through a network on request or a pre-defined schedule. Such infrastructure typically includes hardware, software, communications, customer-associated systems and meter data management software. The infrastructure collects and distributes information to customers, suppliers, utility companies and service providers. 
     The technology described herein may be incorporated into systems comprising mesh network technology. Mesh networks typically include at least one mesh gate and at least one mesh device, such as an electrical meter. The mesh gate may communicate with the meters over a mesh network. The mesh gate may also communicate with a server or processor over a wide area network. The mesh gate may form a mesh network with nearby meters and interface between the meters and the server. 
     Meter Location 
     To analyze the data, it is important for the system to know or determine the position of each meter (M 1 , M 2 , M 3 ) relative to the transformer. In one embodiment, the meter position can be inferred by analyzing the voltages (V 1 , V 2 , V 3 ) reported by each meter. The meter consistently reporting the highest voltage will typically be the closest to the transformer. The position of the other meters may then be determined based on their relative voltage. 
     However, depending on the resistance of the different lines and the current present on each line, it is possible that the voltage reported by a meter closer to the transformer may be less than the voltage reported by meters further down the distribution line. For this reason, in certain embodiments, the position of each meter may be determined statistically based on multiple samples. For example, any number of instantaneous voltage samples may be determined by the system for each meter. The average of the samples may be determined for each meter, and meter positions may be determined based on the average. In other embodiments, the position of each meter may be determined based on the respective median sample voltage of each meter. Of course, the location of the meters may simply be manually entered into the system by, for example, and operator. The operator may also update the meter position as new meters are installed or as older meters are removed. 
     Resistance Estimation 
     Still referring to  FIG. 2 , the resistances (R 1 , R 2 , R 4 , R 5 , R 7 ) of the different lines can be estimated by using at least two samples of the instantaneous voltages and currents. In one embodiment, this process begins by estimating the resistance of the line farthest from the transformer (e.g., R 7 ). 
     Referring to  FIG. 3 , a first subcircuit of  FIG. 2  is shown. The voltage (V 6 ) across R 5  can be expressed based on the current and voltage reported by meter M 2  (I 2 , V 2 ) and meter M 3  (I 3 , V 3 ). The following equations show this relationship for a first sample (Sample x):
 
 V 6 x =( R 7 *I 3 x )+ V 3 x   (1)
 
 V 6 x =( R 5 *I 2 x )+ V 2 x   (2)
 
     Using these equations, the relationship between resistances R 5  and R 7  may be expressed as follows: 
     
       
         
           
             
               
                 
                   
                     R 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           7 
                           * 
                           I 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           3 
                           ⁢ 
                           x 
                         
                         ) 
                       
                       + 
                       
                         V 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                         ⁢ 
                         x 
                       
                       - 
                       
                         V 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                         ⁢ 
                         x 
                       
                     
                     
                       I 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                       ⁢ 
                       x 
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
           
         
       
     
     A second sample (Sample y) may then be obtained to determine a second equation for R 5 : 
     
       
         
           
             
               
                 
                   
                     R 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   = 
                   
                     
                       
                         ( 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           7 
                           * 
                           I 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           3 
                           ⁢ 
                           y 
                         
                         ) 
                       
                       + 
                       
                         V 
                         ⁢ 
                         
                             
                         
                         ⁢ 
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                       - 
                       
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                         y 
                       
                     
                     
                       I 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                       ⁢ 
                       y 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
     Combining equations 3 and 4, the value of R 7  may be expressed as: 
     
       
         
           
             
               
                 
                   
                     R 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     7 
                   
                   = 
                   
                     
                       
                         ( 
                         
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                   ( 
                   5 
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     Using the same technique, the resistance R 5  can computed as follows: 
     
       
         
           
             
               
                 
                   
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                     ⁢ 
                     
                         
                     
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                     5 
                   
                   = 
                   
                     
                       
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                   ( 
                   6 
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     Each following stage in the distribution circuit can be estimated using the same method described above. To obtain the same condition as above, the voltage and current of the distribution line are estimated using the resistances previously computed. For example, the corresponding samples of V 6  and I 6  may be computed using R 7  as follows:
 
 V 6 x =( R 7 *I 3 x )+ V 3 x   (7)
 
 V 6 y =( R 7 *I 3 y )+ V 3 y   (8)
 
 I 6 x=I 2 x+I 3 x   (9)
 
 I 6 y=I 2 y+I 3 y   (10)
 
     Referring to  FIG. 4 , a second subcircuit of  FIG. 2  is shown. Once the above calculations are computed, the following two resistances (R 2  and R 4 ) can be computed as shown in the equations below: 
     
       
         
           
             
               
                 
                   
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                     ⁢ 
                     
                         
                     
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                   = 
                   
                     
                       
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                   ( 
                   12 
                   ) 
                 
               
             
           
         
       
     
     The quality of this estimate depends on the precision of the measurements and the different currents present during these measurements—a higher current typically produces a more accurate estimate since measurement errors are smaller relative to the higher reading. For this reason, multiple sample sets may be used to produce multiple estimates which may then be averaged or from which the median value may be ascertained. 
     Typically, the samples used should be different to avoid a division by zero when computing the resistances. Accordingly, sample sets that produce a division by zero may be discarded. 
     Voltage Consistency 
     Once the location of each meter within the distribution circuit is known and the different resistances are estimated, each sample reported by the meters can be used to compare the voltage reported by the meters and the voltage computed based on the reference circuit. 
     For example, using the reference circuit defined by  FIG. 2 , the voltages may be represented as follows:
 
 V 5 =V 1+( R 2 *I 1)  (13)
 
 V 6 =V 5−( R 4*( I 2 +I 3))  (14)
 
 V 2 ′=V 6−( R 5 *I 2)  (15)
 
 V 3 ′=V 6−( R 7 *I 3)  (16)
 
     The percentage of discrepancy can be computed by comparing the voltage reported by the meter (V 2 , V 3 ) and the voltage computed by the reference circuit (V 2 ′, V 3 ′): 
     
       
         
           
             
               
                 
                   
                     % 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     discrepency 
                   
                   = 
                   
                     
                       
                         absolute 
                         ⁡ 
                         
                           ( 
                           
                             
                               V 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 2 
                                 ′ 
                               
                             
                             - 
                             
                               V 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               2 
                             
                           
                           ) 
                         
                       
                       
                         V 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                     
                     * 
                     100 
                   
                 
               
               
                 
                   ( 
                   17 
                   ) 
                 
               
             
             
               
                 
                   
                     % 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     discrepency 
                   
                   = 
                   
                     
                       
                         absolute 
                         ⁡ 
                         
                           ( 
                           
                             
                               V 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 3 
                                 ′ 
                               
                             
                             - 
                             
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                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               3 
                             
                           
                           ) 
                         
                       
                       
                         V 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                       
                     
                     * 
                     100 
                   
                 
               
               
                 
                   ( 
                   18 
                   ) 
                 
               
             
           
         
       
     
     Equations (17) and (18) are reflective of measured discrepancy with respect to M 2  and M 3 , respectively. 
     Possible energy theft is signaled when the percentage of discrepancy is higher than a certain threshold. For example, if the percentage of discrepancy of the voltage reported by the meter and the voltage computed by the reference circuit exceeds about 50%, about 25%, about 10%, about 5%, about 1% or even about 0.5%, a possible energy theft may be occurring at the corresponding location in the distribution circuit. Accordingly, in one embodiment, if the percent discrepancy exceeds the threshold, the system may raise a flag or otherwise alert an operator. The operator may then investigate the discrepancy and correct the situation 
     For simplicity, the different equations presented have been based on the reference circuit shown in  FIG. 2  containing three electric meters. One skilled in the art recognized that the same logic applies to any distribution circuit with at least two meters. 
     Unless specifically stated otherwise as apparent from the foregoing discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, can refer to the action and processes of a data processing system, or similar electronic device, that manipulates and transforms data represented as physical (electronic) quantities within the system&#39;s registers and memories into other data similarly represented as physical quantities within the system&#39;s memories or registers or other such information storage, transmission or display devices. 
     The exemplary embodiments can relate to an apparatus for performing one or more of the functions described herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a machine (e.g. computer) readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs and magnetic-optical disks, read only memories (ROMs), random access memories (RAMs) erasable programmable ROMs (EPROMs), electrically erasable programmable ROMs (EEPROMs), magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a bus. 
     Some exemplary embodiments described herein are described as software executed on at least one processor, though it is understood that embodiments can be configured in other ways and retain functionality. The embodiments can be implemented on known devices such as a server, a personal computer, a special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit element(s), and ASIC or other integrated circuit, a digital signal processor, a hard-wired electronic or logic circuit such as a discrete element circuit, or the like. In general, any device capable of implementing the processes described herein can be used to implement the systems and techniques according to this invention. 
     It is to be appreciated that the various components of the technology can be located at distant portions of a distributed network and/or the internet, or within a dedicated secure, unsecured and/or encrypted system. Thus, it should be appreciated that the components of the system can be combined into one or more devices or co-located on a particular node of a distributed network, such as a telecommunications network. As will be appreciated from the description, and for reasons of computational efficiency, the components of the system can be arranged at any location within a distributed network without affecting the operation of the system. Moreover, the components could be embedded in a dedicated machine. 
     Furthermore, it should be appreciated that the various links connecting the elements can be wired or wireless links, or any combination thereof, or any other known or later developed element(s) that is capable of supplying and/or communicating data to and from the connected elements. The terms determine, calculate and compute, and variations thereof, as used herein are used interchangeably and include any type of methodology, process, mathematical operation or technique. 
     The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed since these embodiments are intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims. All publications cited herein are incorporated by reference in their entirety.