Abstract:
An apparatus and method for continuously monitoring substation disconnects and transmission line switches to detect improper closing of the disconnects or switches is disclosed. The method includes the step of providing an apparatus adapted to measure, process, and transmit data associated with a disconnect or switch. The method further includes the steps of positioning the apparatus on or in close proximity to the disconnect or switch, using the apparatus to collect data of the disconnect or switch and processing the data for transmission to a remote receiver, and transmitting the processed data to a remote receiver.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application relates to an apparatus and method for monitoring substation disconnects and transmission line switches. More particularly, it relates to an apparatus and method for continuously monitoring temperatures of substation disconnects and transmission line switches. 
         [0002]    Substation disconnects and transmission line switches are used to physically disconnect circuits to ensure that there is no electrical connection. There are different types of switches, some which rely on rotation of an arm,  FIG. 1 , and others where the arm rotates around a pivot point at one end of the arm,  FIG. 2 . The electrical connection between the two sides of the switch is made by the arm making electrical connection into “jaws”. 
         [0003]    When an operator closes a disconnect and the arm fits into the jaws, the operator has no way of knowing if the disconnect is fully closed or, if the arm has passed its optimum point. Instead, the operator relies on mechanical stops. Not fully or under closing of disconnects are one reason for overheating. 
         [0004]    If proper contact between the arm and jaws is not achieved, high resistance connections may result. With high currents, this connection may overheat and result in degradation of the jaws which may result in failure—catastrophic or nearly impossible to open the disconnect switch. See  FIG. 4 . 
         [0005]    Infrared inspections are the most common methods of identifying high risk disconnects. However, there are some drawbacks: (1) heating only happens at times of high loading—which may not be at the time of inspection; (2) inspections are generally performed one or two times per year; (3) only severely degraded units are identified as small temperature differences are hard to identify and diagnose. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    These and other shortcomings of the prior art are addressed by the present invention, which provides an apparatus and method for monitoring substation disconnects and transmission line switches on a continual basis. 
         [0007]    According to an aspect of the invention, a method of continuously monitoring substation disconnects and transmission line switches to detect improper closing of the disconnects or switches includes the step of providing an apparatus adapted to measure, process, and transmit data associated with a disconnect or switch. The method further includes the steps of positioning the apparatus on or in close proximity to the disconnect or switch, using the apparatus to collect data of the disconnect or switch and processing the data for transmission to a remote receiver, and transmitting the processed data to a remote receiver. 
         [0008]    According to another aspect of the invention, a method of continuously monitoring substation disconnects and transmission line switches to detect improper closing of the disconnects or switches including the steps of providing an apparatus having a temperature measurement device, a processor, and a transmitter. The method further including the steps of positioning the apparatus on or in close proximity to a disconnect or switch, positioning the temperature measurement device in thermal contact with the disconnect or switch, using the processor to process temperature measured by the temperature measurement device, and using the transmitter to transmit the processed temperature measurements to a remote receiver. 
         [0009]    A method of continuously monitoring substation disconnects and transmission line switches to detect improper closing of the disconnects or switches including steps of providing an apparatus having an arm position indicator, a processor, and a transmitter. The method further including the steps of positioning the apparatus on an arm of the disconnect or switch, using the arm position indicator to determine a location of the arm, using the processor to process a signal from the arm position indicator representative of the location of the arm, and using the transmitter to transmit the processed signal to a remote receiver. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    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: 
           [0011]      FIG. 1  shows an example of a disconnect with horizontal arms; 
           [0012]      FIG. 2  shows a disconnect where the arm moves in a vertical plane; 
           [0013]      FIG. 3  shows a transmission line disconnect; 
           [0014]      FIG. 4  is an infra-red image of two disconnects over-heating; 
           [0015]      FIG. 5  shows wireless disconnect sensors that measure temperature; 
           [0016]      FIG. 6  shows a wireless sensor installed on a moving arm; and 
           [0017]      FIG. 7  shows a wireless sensor installed on a stationary jaw side of disconnect. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring to the drawings, an exemplary apparatus for monitoring substation disconnects and transmission line switches according to an embodiment of the invention is illustrated in  FIGS. 5-7  and shown generally at reference numeral  10 . The apparatus  10  is an RF wireless sensor that can be installed on a moveable arm,  FIG. 6 , or on a stationary jaw side,  FIG. 7 . The apparatus  10  may be powered by a battery, by power harvesting from an AC magnetic field using a coil and inductor, and/or a battery or supercapacitor or combo thereof which is recharged by the AC magnetic field. 
         [0019]    The apparatus  10  includes electronics for monitoring conditions of the disconnects and switches as well as for providing data such as location and position. These electronics include an accelerometer for acceleration in one, two, or three dimensions (DC and/or higher sampling rate); a magnetometer to measure compass direction; a gyroscope; and a thermocouple for measuring temperature. In addition, the electronics measure the AC magnetic field. The thermocouple can measure the temperature of the arm or the jaw and is positioned as close as possible to the interface by extending the length of the thermocouple wire. 
         [0020]    Referring to  FIG. 8 , a more detailed look at the apparatus  10  is provided. An electronics housing  11  includes a coil  12 , a battery  13 , a first electronic board  14 , a second electronic board  16 , an antenna  17  and matching strip-line PCB board  18 . The coil  12  includes a ferrite core with windings wrapped around the core and is adapted to harvest power from a magnetic field produced by current flowing in transmission lines. As shown, the battery  13  is a non-rechargeable battery and provides power to the apparatus  10  when there is no or low current flowing through the transmission lines to produce a magnetic field. The battery will last  2  years with no power. It should be appreciated that the battery may also be a rechargeable battery adapted to be recharged by the coil  12  when needed. 
         [0021]    The first electronic board  14  performs power harvesting, measurement and processing, storage of signals, and controls the whole measurement communications process. The board  14  has inputs for voltage from the coil  12  and a thermocouple assembly  20 . The voltage from the coil  12  is also harvested to power the apparatus  10  (if high enough—if too low switches to battery  13 ). The board  14  also includes a 3D accelerometer chip which takes samples from DC to 2000 samples per second, a magnetometer, and a gyro. 
         [0022]    The second electronic board  16  is an RF transmitter. The board  16  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  16  provides for two way RF communications to allow firmware of the apparatus  10  to be updated or reset and to allow data to be downloaded from the apparatus  10  to a remote location having computers or processors with software adapted to perform specified calculations. All of the electronics and RF communications are designed to be very low power to enable power harvesting and long battery life. 
         [0023]    The antenna  17  includes a stalk  21  that extends through the housing  11  and an antenna ball  22  and is electrically connected to the board  16 . 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. The matching strip-line PCB board  18  is electrically connected to the antenna  17  and sits behind the antenna  17  to ensure that power is fully transmitted to the antenna  17 . 
         [0024]    The thermocouple assembly  20  is electrically connected to the first electronic board  14  and is adapted to measure temperature. The thermocouple assembly  20  includes a thermocouple  23 , a thermocouple tip  24  which houses a portion of the thermocouple  23 , an insulator bushing  26  positioned adjacent to or behind the tip  24 , a spring  27  positioned adjacent to or behind the bushing  26 , and a plug and play connector  28  to electrically connect the thermocouple  23  to the board  14 . The thermocouple assembly  20  is the only thermal and electrically conductive component in contact with the conductor  20  to prevent heat sinking and to enable a single point ground so that currents do not flow through the sensor  10 . 
         [0025]    A local or wireless receiver is used to obtain readings from the apparatus  10 . The receiver may be a hand held receiver for use by an operator in the field; a local base station for downloading info to and from; or a cell phone or satellite network. Raw measurements may be sent to the receiver for processing or the measurements may be processed by the apparatus  10  and then sent to the receiver. 
         [0026]    In general the apparatus  10  may be mounted on or in close proximity to a stationary part of a disconnect or switch jaw, or on or in close proximity to a disconnect or switch arm. A thermocouple may be placed on or in close proximity to the jaw to measure temperature. The signal is then wirelessly transmitted to a local base or remote station and data is integrated. The wireless sensor can also be read during rounds inspections using a portable RF reader. 
       Scenario No. 1—Arm Pivots On One Side (FIG. 2) 
       [0027]    Since the apparatus  10  is installed on the arm and steady state acceleration is being measured, the orientation of the arm with respect to the jaw may be determined with respect to “earth” by using the acceleration measured in the x, y, and z planes. This orientation is monitored after every operation, and if the disconnect has not fully closed, or is in a strange position, this information can be used at the time operation to ensure that the jaw is fully closed. 
         [0028]    If a second “stationary” apparatus  10  is installed on the jaw side, a reference measurement on the stationary side will provide a more precise measurement since the whole assembly may move with time (e.g. foundation subsidence). 
         [0029]    Since the orientation measurement may be continuous, if the jaw shifts/arm alignment with expansion and contraction this may be identified and trigger a maintenance angle. The apparatus  10  includes a temperature measurement which is also known to be a good diagnosis technique under higher loading conditions and closer to failure. 
         [0030]    The apparatus  10  can also measure acceleration with a higher sampling rate, so that the acceleration curves and vibrations may be measured during opening and closing. These may also provide diagnostic information about the condition of the disconnect (mechanical gears, motors, joints, etc.). 
       Scenario No. 2—Rotational Type (FIG. 1) 
       [0031]    Acceleration will not change with respect to gravity in these types of disconnects. In this case, the magnetometer (compass direction) and Gyro can be utilized to provide similar information. If all three are combined even more information will be available to make a diagnosis. 
         [0032]    The measurement of AC magnetic field allows the temperature to be correlated to current flowing through the jaw/arm connection so that one can determine whether the resulting heating is normal or just a function of high loading conditions. 
         [0033]    The AC magnetic field may also be used to power the sensor. This may be used in concert with non-rechargeable batteries for times of low loading, or rechargeable super capacitors/batteries. 
         [0034]    The foregoing has described an apparatus and method for monitoring substation disconnects and transmission line switches. 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.