Abstract:
An apparatus for measuring voltage in a broadband over power line system including a first load having a first predetermined impedance, and a second load having a second predetermined impedance. Wherein the apparatus is contained within a capacitor-based BPL coupler. Also a method of measuring a voltage and a phase angle in a broadband over power line system comprising attaching a voltage divider to a medium voltage power line, measuring a voltage and a phase angle at said voltage divider and calculating said voltage and the phase angle based on the measured voltage and the measured phase angle. Wherein the voltage divider may be placed within a coupler along the broadband over power line system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Appl. No. 60/996,270 filed Nov. 8, 2007, and U.S. Provisional Appl. No. 60/996,271 filed Nov. 8, 2007, the entire disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention is directed toward measuring the voltage and voltage phase angle on a power line in a broadband over power line (BPL) system. 
       BACKGROUND OF THE INVENTION 
       [0003]    Broadband communications services can be provided using one or more high-voltage cables of a power distribution network, while the power distribution network supplies electrical power. A radio-frequency signal at a first location (or node) is modulated with a data signal and coupled to a high-voltage cable serving as a transmission channel. At a second node the radio-frequency signal is coupled from the high-voltage cable to a demodulator for converting the modulated signal back to a data signal. Data is sent from the second node to the first node in a similar manner typically using a different band of frequencies. This full-duplex broadband service between the locations may simultaneously supply a variety of communication needs, such as telephone service, video service, Internet service, and other services requiring high-speed data transfers. Part of the BPL system is a coupler which connects the BPL equipment to a power line. The coupler provides physical connectivity to the line to transfer the BPL signal, but it can be used for other purposes too. 
         [0004]    Since data can be sent over the power line, various “smart grid” systems have been used. Such systems may read a customer&#39;s electric power meter remotely or even remotely manipulate devices at the customer site. Another use of such systems is to read various characteristics of the power line itself. Conventional methods of reading power line characteristics require specialized equipment to read the line and to collect the data. Detecting the presence and/or measuring the value of the voltage on the power line and measuring the voltage phase angle on multi-phase power lines are some of the best indicators of whether a power grid is about to malfunction or fail, causing power outages. 
         [0005]    Accordingly, there is a need and desire for reading the value and presence of voltage and voltage phase angles on power lines to identify and locate potential power outages. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    1. An apparatus for measuring voltage in a broadband over power line system including a first load having a first predetermined impedance, and a second load having a second predetermined impedance. Wherein the apparatus is contained within a capacitor-based BPL coupler. Also a method of measuring a voltage and a phase angle in a broadband over power line system comprising attaching a voltage divider to a medium voltage power line. Further comprising, measuring a voltage and a phase angle at the voltage divider and calculating the voltage and the phase angle based on the measured voltage and the measured phase angle. Wherein the voltage divider may be placed within a coupler along the broadband over power line system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic diagram of a BPL system constructed in accordance with an embodiment described herein; 
           [0008]      FIG. 2  is a block diagram of an apparatus for measuring voltage and voltage phase angle on a power line constructed in accordance with the embodiment described herein; 
           [0009]      FIG. 3  is a block diagram of an apparatus for measuring voltage and voltage phase angle on a power line where the measuring is contained in a capacitor-based coupler constructed in accordance with the embodiment described herein; and 
           [0010]      FIG. 4  is a schematic diagram of a system for measuring and comparing the voltage phase angles of multiple phases on a multi-phase power line constructed in accordance with an embodiment described herein. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof and show by way of illustration specific embodiments in which embodiments of the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice them, and it is to be understood that other embodiments may be utilized, and that structural, logical, processing, and electrical changes may be made. The progression of processing steps described is an example; however, the sequence of steps is not limited to that set forth herein and may be changed as is known in the art, with the exception of steps necessarily occurring in a certain order. 
         [0012]    Now referring to the figures, where like numerals designate like elements,  FIG. 1  is a schematic diagram of a BPL system  100  constructed in accordance with an embodiment described herein. BPL system  100  includes first, second, and third utility poles  105 ,  110 ,  115 ; a medium-voltage power line  120 ; a low-voltage power line  121 ; first, second, and third BPL regenerators  125 ,  130 ,  135 ; and a customer site  140  connected to the low-voltage power line  121  near the second regenerator  130  for receiving the broadband signal. First through sixth BPL couplers  145 - 150  are connected between the BPL regenerators  125 ,  130 ,  135  and the medium-voltage power line  120 . 
         [0013]    BPL system  100  further includes components  160 ,  165 ,  170 ,  175 , which can be any other typical components found in a power grid and connected to any part of the grid, e.g., transformers, arresters, reclosers, and taps. Each utility pole  105 ,  110 ,  115  connected to a respective regenerator  125 ,  130 ,  135  is a node A, B, C. Each node has two couplers  145 - 150  connected to it, one for receiving the BPL signal at a first frequency, and the other for transmitting the BPL signal at a second frequency. It should be noted that every utility pole in a power grid may not have a BPL regenerator. The medium-voltage power line  120  may be a single-phase or multi-phase power line, such as a three-phase power line. 
         [0014]      FIG. 2  is a block diagram of an apparatus  200  for measuring voltage or voltage phase angle on a power line constructed in accordance with an embodiment described herein. Apparatus  200  includes a first load  210  having a first predetermined impedance Z 1 . Apparatus  200  further includes a second load  220  having a second predetermined impedance Z 2 . The first and second loads  210 ,  220  are connected to each other at node D. The apparatus  200  is connected between the medium-voltage power line  120  and neutral wire  121 , and forms a voltage divider at node D. The neutral wire  121  may also be a ground wire. The phase angle can be measured at the node D of the voltage divider. The voltage V M  at the medium-voltage power line  120  can be calculated according to: 
         [0000]    
       
         
           
             
               
                 
                   
                     V 
                     M 
                   
                   = 
                   
                     
                       V 
                       D 
                     
                     * 
                     
                       ( 
                       
                         
                           
                             Z 
                             1 
                           
                           + 
                           
                             Z 
                             2 
                           
                         
                         
                           Z 
                           2 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0015]    where V M  is the voltage at the medium-voltage power line, V D  is the voltage measured across the second load  220  at node D, and Z 1  and Z 2  are the respective impedances of the first and second loads  210 ,  220 . 
         [0016]      FIG. 3  illustrates a further embodiment of an apparatus  300  for measuring voltage and voltage phase angle on a power line in a BPL system constructed in accordance with an embodiment described herein. The apparatus includes a voltage divider built into one of the BPL couplers  145 - 150 , the coupler being represented in this case by capacitor-based BPL coupler  301 . The first load  310  is the predetermined native capacitance of the capacitor-based BPL coupler  301 . The second load  320  may be a resistor or other resistive device. The second load  320  is built into the BPL coupler  301 . The apparatus  300  forms a voltage divider at node D. The apparatus  300  is connected between the medium-voltage power line  120  and the low-voltage power line  121 . 
         [0017]    The voltage V M  at the medium-voltage power line  120  can be calculated according to: 
         [0000]    
       
         
           
             
               
                 
                   
                     V 
                     M 
                   
                   = 
                   
                     
                       V 
                       D 
                     
                     * 
                     
                       ( 
                       
                         
                           
                             Z 
                             C 
                           
                           + 
                           
                             Z 
                             2 
                           
                         
                         
                           Z 
                           2 
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0018]    where V M  is the voltage at the medium-voltage power line, V D  is the voltage measured across the second load  320  at node D, Z C  is the capacitance  310  of the capacitor-based BPL coupler  301 , and Z 2  is the impedance of the second load  320 . 
         [0019]    Another exemplary method of measuring the phase angle of a medium-voltage power line  120  is to isolate a 60 Hz frequency from the RF BPL signal and measure the 60 Hz frequency. Adding a shift capacitor to the sensor shifts the voltage phase angles by 90°, which should be taken into account when comparing phase angles from multiple medium-voltage power lines. A shift resistor may also be used in place of the shift capacitor; however it may increase the capacitance, and this affects the RF BPL signal. 
         [0020]      FIG. 4  illustrates a schematic diagram of a system  400  for measuring voltage phase angle on a BPL system on a multi-phase power line. Medium-voltage power lines  422 ,  423 ,  424  each have an apparatus  401 ,  402 ,  403  for measuring their respective phase angles, consistent with an embodiment of the present invention. Ideally, the phase angles of each phase in the multi-phase power line system are equal. The respective phase angles of the medium-voltage power lines  422 ,  423 ,  424  are then communicated to a phase angle comparing device  450 . Phase angle comparing device  450  may be a processor configured to receive phase angle measurements, or a circuit configured to receive values (such as voltages) representing the detected phase angles, and output another value (such as another voltage) representing a difference between the detected phase angles. It should be understood that several methods of comparing measured phase angles are known in the art, and the phase angle comparing device  450  is not limited to the above-described embodiments. The respective phase angles are compared to each other, and if they are not equal, or not within a predetermined tolerance, correction may be required. The voltage phase angles and the comparison results may be reported automatically to a remote location (not shown) such as a power station or office, for instance by a data collection device (not shown). The result may be the comparison alone or a warning that correction is needed. 
         [0021]    In both  FIGS. 2 and 3 , the power on the medium-voltage power line  120  can also be calculated according to: 
         [0000]        P=V   M   *I   (3) 
         [0022]    where P is the power, V M  is the voltage at the medium-voltage power line, and I is a current measured at the medium-voltage power line  120 . 
         [0023]    The determined voltage and voltage phase angle at the medium-voltage power line V M  and power P may be reported automatically to a remote location such as a power station or office, for instance by a data collection device. 
         [0024]    The processes and devices in the above description and drawings illustrate examples of methods and devices of many that could be used and produced to achieve the objects, features, and advantages of embodiments described herein. For example, embodiments include receiving and transmitting the same signal frequency at each node A-C while still avoiding interference. Thus, the embodiments are not to be seen as limited by the foregoing description of the embodiments, but only limited by the appended claims.