Abstract:
A sensor and method for identifying a downed power transmission conductor or structure is disclosed. The method includes the steps of securing a sensor to a power transmission conductor or structure, using the sensor to measure inclination of the power transmission conductor or structure, comparing the measured inclination to a set threshold, and alerting a utility if the measured inclination exceeds the set threshold.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to a sensor and method for identifying downed power transmission conductors and structures, and more particularly, to a sensor and method used to determine the inclination of power transmission conductors and structures. 
         [0002]    Power transmission conductors (or bundles of them) are attached to support structures (poles or towers) utilizing attachment hardware and other structures such as insulators. Unfortunately, these physical connections can fail for a number of reasons:
       1. Failure of hardware/insulator under wind or ice loading;   2. Fires on a wooden pole may cause the hardware to disconnect;   3. The pole itself may fail; or   4. The conductor itself may fail.       
 
         [0007]    As a result of a failure, the power transmission conductor can either fall to the ground or hang closer to the ground creating a dangerous situation. If the conductor comes in contact with the ground it may cause protection to operate and the circuit to become denergized. If the protection does not operate it can be a hazard. If the conductor does not electrically come in contact with a grounded object, the protection will not operate. This will result in a low hanging conductor which may come in contact with humans or animals resulting in a hazard (a similar condition may happen if the conductor itself fails). 
         [0008]    Accordingly, there is a need for a sensor than can notify a utility about such failures and low hanging conductors to permit the utility to take corrective actions such as: (1) denergizing the circuit, (2) deploying a field crew to repair the asset, and (3) make local authorities aware of the hazard in order to barricade the hazard. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    These and other shortcomings of the prior art are addressed by the present invention, which provides a sensor secured to a power transmission conductor or structure to alert a utility that the power transmission conductor or structure is down. 
         [0010]    According to one aspect of the present invention, a method for identifying a downed power transmission conductor or structure includes the steps of securing a sensor to a power transmission conductor or structure, using the sensor to measure inclination of the power transmission conductor or structure, comparing the measured inclination to a set threshold, and alerting a utility if the measured inclination exceeds the set threshold. 
         [0011]    According to another aspect of the invention, a method for identifying a downed power transmission conductor or structure including the steps of providing a sensor having an accelerometer adapted to measure inclination in three axes, securing the sensor to a power transmission conductor or structure, using the accelerometer to measure the inclination of the power transmission conductor or structure, comparing the measured inclination to a pre-determined threshold, and transmitting an alert to a utility when the measured inclination exceeds the pre-determined threshold. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The subject matter that is regarded as the invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
           [0013]      FIG. 1  is a perspective view of a sensor according to an embodiment of the invention; 
           [0014]      FIG. 2  shows electronics of the sensor of  FIG. 1 ; 
           [0015]      FIG. 3  shows electronics of the sensor of  FIG. 1 ; 
           [0016]      FIG. 4  shows inclinations and accelerations of the sensor of  FIG. 1  installed on a power transmission conductor; 
           [0017]      FIG. 5  illustrates a system of sensors of  FIG. 1  used to monitor power transmission conductors and structures; and 
           [0018]      FIG. 6  is a perspective view of the sensor of  FIG. 1  connected to a jaw assembly for attachment to a power transmission conductor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring to the drawings, an exemplary sensor for identifying downed power cables and/or structures according to an embodiment of the invention is illustrated in  FIG. 1  and shown generally at reference numeral  10 . The sensor  10  is an RF sensor which attaches to power transmission conductors and/or support structures such as towers, poles, insulators, and any other suitable support structure or attachment device. 
         [0020]    In general, the sensor  10  includes an electronics module  12 ,  FIG. 2 , contained in an electronics housing  11  that utilizes an accelerometer to measure the inclination of a power transmission conductor or support structure. If the conductor and/or structure changes in inclination outside of the normal everyday changes in inclination expected, utility personnel would be alerted. A sensor  10  attached to a conductor would inform on the status of a conductor, while a sensor  10  attached to a structure would inform on the condition of the structure (e.g. pole). The sensor  10  may also measure a transient acceleration event when “failure” happens. It should be appreciated that the electronics housing  11  may be of different forms or designs based on the application of the sensor  10 . It should also be appreciated that the electronics module  12  may include different layouts and circuits. The form, layout, or shape of the electronics housing  11  and electronics module  12  are for illustrative purposes only. 
         [0021]    Referring to  FIGS. 2 and 3  an example electronics module  12  is shown. The electronics module  12  may include a coil  13  for capturing magnetic fields to power the sensor  10 , a battery  14  for providing power to the sensor  10  when the sensor  10  is not powered by magnetic fields, a first electronic board  16 , a second electronic board  17 , an antenna  18  and matching strip-line PCB board  19 . The coil  13  includes a ferrite core with windings wrapped around the core and is adapted to couple with a magnetic field to harvest power therefrom and to measure the amount of current flowing. It should be appreciated that the battery  14  may be a non-rechargeable or rechargeable battery adapted to be recharged by the coil  13  when needed. Further, it should be appreciated that a supercap lithium battery combination may be employed for high power and lower temperature operation. 
         [0022]    The first electronic board  16  performs power harvesting, measurement and processing, storage of signals, and controls the whole measurement communications process. The board  16  has inputs for voltage from the coil  13  and measures the voltage from the coil  13  to get a measurement of current flowing through a conductor. The voltage from the coil  13  is also harvested to power the sensor  10 . The board  16  also includes a 3D accelerometer chip  20  which takes samples from DC to greater than 100 Hz. The accelerometer  20  is a solid state accelerometer. 
         [0023]    The second electronic board  17  is an RF transmitter. The board  17  is adapted for plug and play so that different RF boards can be utilized to enable different communications protocols, frequencies, and/or methods. The board  17  provides for two way RF communications to allow firmware of the sensor  10  to be updated or reset and to allow data to be downloaded from the sensor  10  to a remote location having computers or processors with software adapted to perform specified calculations. Additionally, the RF communications may be point-to-point (sensor  10  to a base station), mesh (sensor  10  to sensor  10  to sensor  10  to repeater to . . . base station), sensor  10  to satellite, and sensor  10  to handheld or vehicle mounted receiver. All of the electronics and RF communications are designed to be very low power to enable power harvesting and long battery life. 
         [0024]    The antenna  18  includes a stalk  21  that extends through the housing  11  and an antenna ball  22  and is electrically connected to the board  17 . The diameter of the ball and the height of the stalk are optimized for both RF transmission and omni-directional beam pattern. Further, the shape of the antenna ball is optimized to prevent corona. A matching strip-line PCB board  23  is electrically connected to the antenna  18  and sits behind the antenna  18  to ensure that power is fully transmitted to the antenna  18 . 
         [0025]    In operation, the sensor  10  can perform on board measurements and algorithms/calculations for present conductor and ambient temperature—rolling average, present current, maximum temperature, current at the time of maximum temperature, histogram of temperatures (# of minutes/hour in a specific temperature range), inclination in three axes, raw vibration waveforms in three axes—10 second clips, Fast Fourier Transform of the waveform to provide frequency content of vibration waveform, and calculate displacement from the acceleration measured. 
         [0026]    For purposes of determining whether a power transmission conductor or structure is downed, the sensor  10  uses the accelerometer  20  to determine inclination and acceleration in three axes. The sensor  10  may measure itself and compare against a threshold (either inclination or transient) or send data to a base station or server where the data is analyzed. If the data measured is out of compliance with the threshold, then an alarm is sent to the utility, indicating that a conductor or structure is down. Example measurements are shown in  FIG. 4 . 
         [0027]    The sensor  10  may be used in different forms for different applications. For example, the sensor  10  may be employed on a power transmission conductor; an insulator; or a support structure. In the case of the support structure, the sensor  10  is secured directly to the structure, see  FIG. 5 . In the case of a power transmission conductor, the sensor  10  may be connected to a jaw assembly  31 ,  FIG. 6 , such as that described in U.S. application Ser. No. 13/551,085, hereby incorporated herein by reference, and secured to the power transmission line using the jaw assembly  31 . In the case of insulators, the sensor  10  is integrated into another chassis adapted for use with insulators, such as that described in U.S. patent application Ser. Nos. 13/728,462 and 13/728,484, hereby incorporated by reference. As shown in  FIG. 5 , a plurality of sensors  10  may be used in their differing forms at the same time. 
       Example of Power Transmission Cable Use 
       [0028]    As shown in  FIG. 6 , when using the sensor  10  on a power transmission conductor  30 , the sensor  10  is connected to a jaw assembly  31 . As shown, the jaw assembly  31  includes a first jaw  32  pivotally attached to a second jaw  33  via pivot joint  34  to allow the jaw assembly  31  to move between an open position, to receive a conductor  30  therein, and closed position, to secure the sensor  10  to the conductor  30 . The jaw assembly  31  is secured in the closed position by a fastener  36  which extends through the first and second jaws  32 ,  33 . The fastener  36  may be tightened by a standard wrench or socket type tool. The jaw assembly  31  is designed to allow the sensor to be placed on an energized conductor with a hot stick. 
         [0029]    The jaw assembly  13  further includes an adjustable clamping assembly having first and second clamping mechanisms  37 ,  38 . Both clamping mechanisms  37  and  38  include a concave inner surface to complement the rounded outside surface of the conductor  30 . The inner surfaces also include a plurality of steps that act like teeth to secure the sensor  10  to the conductor  30 . Together, the concave inner surfaces and steps of the clamping mechanisms  37 ,  38  allow the clamping assembly to mate with and secure the sensor  10  to various sized conductors, i.e., conductors of different diameters. As shown, the clamping assembly is made of a thermoplastic; however, other suitable materials may be used. 
         [0030]    Clamping mechanism  38  includes elongated slots  39  and  40  adapted to receive fasteners therethrough. The slots  39 ,  40  allow the clamping mechanism  38  to be slidably mounted to jaw  33  to allow the clamping assembly to be moved from a non-clamping position, to receive conductors of varying diameters, to a clamping position to secure the sensor  10  to the conductor  30 . 
         [0031]    The foregoing has described a sensor for identifying downed power cables and structures. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.