Abstract:
A power transmission line dip measurement method is disclosed. The dip measurement method includes installing a measurement instrument at a place where power line support points of steel towers can be seen from the ground, collimating the measurement instrument at the power line support point of one of the steel towers, transmitting a collimated value to a PDA in a wired or wireless manner, collimating the measurement instrument at the power line support point of the other steel tower, transmitting a collimated value to the PDA, calculating the collimated values to display a horizontal angle position of a dip base line, and adjusting an angle of the measurement instrument based on the horizontal angle displayed on a screen of the PDA by a worker, collimating the measurement instrument at a power line dip point as a dip base point, and displaying a dip value on the screen of the PDA.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a power transmission line dip measurement method, and more particularly to a power transmission line dip measurement method that is capable of easily and accurately constructing a power cable based on a designed dip during the construction of the power line at power transmission steel towers and, in addition, of accurately measuring a dip of an already constructed power line. 
         [0003]    2. Description of the Related Art 
         [0004]    Generally, the shortest straight distance between a straight line linking power line support positions of two power transmission steel towers and a vertex of a power line is referred to as a power line dip D. The vertex is the lowest point of a curve formed by the power line when the power line is connected to the power line support positions of the power transmission steel towers. 
         [0005]    A conventional power line dip measurement method is an indirect type measurement method in which two workers individually climb two steel towers that support a power line and observe a tangent of the power line using a dip chuck and an observation mirror over a predetermined length of the power line to calculate the maximum magnitude of a dip in a measurement section. 
         [0006]    In order to measure the power line dip D, the height between the power line support points and the tangent is actually measured at the steel towers, an observation point and a dip chuck installation points are set, and the power line is observed using an observation instrument, such as the observation mirror, such that the tangent of the power line coincides with an observation line. 
         [0007]    In the indirect type power line dip measurement using the tangent of the power line, however, all the processes are carried out on the steel towers, with the result that errors may be increased. In addition, the maintenance of accuracy is difficult due to the slope of the steel towers and complicated structure of the steel towers, with the result that measurement errors may be increased. 
         [0008]    Also, the workers must climb up several positions of the steel towers according to the positions of power lines, with the result that it is difficult to secure the safety of the workers, and therefore, the workers may be exposed to danger. In addition, power line dip measurement time is increased, and the number of necessary workers is increased. 
         [0009]    Also, it is difficult to perform accurate power line dip measurement and maintain the dip of the constructed power line for each phase and for each conductor. Furthermore, the dip difference between conductors may cause short circuits of wires. 
       SUMMARY OF THE INVENTION 
       [0010]    Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a power transmission line dip measurement method that is capable of automatically calculating the operating amount of a measurement instrument to a dip point using a vector calculation equation in which power line support points of two steel towers and the dip point are displayed as a space vector, thereby minimizing a measurement error. 
         [0011]    In particular, measurement with the naked eye of each individual worker using a simple measurement instrument during the construction of the lower line is improved, and, in addition, it is possible for a single worker to perform measurement without climbing the steel tower, thereby improving working efficiency and management efficiency. 
         [0012]    In accordance with the present invention, the above and other objects can be accomplished by the provision of a power transmission line dip measurement method including a measurement instrument installation step of installing a measurement instrument at a place where power line support points of two steel towers can be seen from the ground, a first collimation step of collimating the measurement instrument at the power line support point of one of the steel towers, a first transmission step of transmitting a collimated value to a personal digital assistant (PDA) in a wired or wireless manner, a second collimation step of collimating the measurement instrument at the power line support point of the other steel tower, a second transmission step of transmitting a collimated value to the PDA, an angle calculation step of calculating the transmitted collimated values to display a horizontal angle position of a dip base line, and a dip value display step of adjusting an angle of the measurement instrument based on the horizontal angle displayed on a screen of the PDA by a worker, collimating the measurement instrument at a power line dip point as a dip base point, and displaying a dip value on the screen of the PDA. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIGS. 1A and 1B  are conceptual views (plan and elevation, respectively) illustrating a conventional direct type power line dip measurement method; 
           [0015]      FIG. 2  is a conceptual view illustrating a power line dip measurement theory according to the present invention; 
           [0016]      FIG. 3  is a construction view illustrating dip measurement equipment according to the present invention; 
           [0017]      FIG. 4  is a flow chart illustrating a process of measuring a dip of an already constructed power line according to the present invention; 
           [0018]      FIG. 5  is a construction view illustrating a dip measurement screen of a personal digital assistant (PDA) during the measurement of the dip of the already constructed power line according to the present invention; 
           [0019]      FIG. 6  is a construction view illustrating a data result screen of the PDA during the measurement of the dip of the already constructed power line according to the present invention; 
           [0020]      FIG. 7  is a flow chart illustrating a process of measuring a dip of a power line to be constructed according to the present invention; 
           [0021]      FIG. 8  is a construction view illustrating a dip measurement screen of the PDA during the measurement of the dip of the power line to be constructed according to the present invention; 
           [0022]      FIG. 9  is a view illustrating a first embodiment of the dip measurement according to the present invention; 
           [0023]      FIG. 10  is a view illustrating a second embodiment of the dip measurement according to the present invention; and 
           [0024]      FIG. 11  is a view illustrating a third embodiment of the dip measurement according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0026]    First, a dip measurement method according to the present invention will be described with reference to  FIG. 2 .
       A normal vector, an azimuth angle, and a perpendicular angle of a plane formed by a power line support point Pa of a steel tower A, a power line support point Pb of a steel tower B, and a point Pc obtained by adding an arbitrary number, for example 100, to a z-coordinate value of a center point C between the power line support point Pa and the power line support point Pb are defined as N, h, and v, respectively.   When an arbitrary point, distant from a positional point P 1  of a measurement instrument by 1 meter, of an imaginary line that links the positional point P 1  and a power line dip point X is defined as P 2 ,       
 
         [0000]        hd= 1.0*sin( v ) 
         [0000]        P 2 x=P 1 x÷hd *sin( h ); (x-coordinate of P2) 
         [0000]        P 2 y=P 1 y+hd *cos( h ); (y-coordinate of P2) 
         [0000]        P 2 z=P 1 z+ 1*cos( v ); (z-coordinate of P2)       An equation of a straight line passing through the two points P 1  and P 2  is represented as follows:         
         [0000]        P=P 1 +t ( P 2 −P 1)  (A), (where, t is an arbitrary real number, and P is an arbitrary point)       Normal vector N         
         [0000]        N =( Pb−Pa )×( Pc−Pa )·(cross product) 
         [0000]        Nx =( Pby−Pay )*( Pcz−Paz )( Pbz−Paz )*( Pcy−Pay ); (x-coordinate of N) 
         [0000]        Ny =( Pbz−Paz )*( Pcx−Pax )−( Pbx−Pax )*( Pcz−Paz ); (y-coordinate of N) 
         [0000]        Nz =( Pbx−Pax )*( Pcy−Pay )−( Pby−Pay )*( Pcx−Pax ); (z-coordinate of N) 
         [0000]      mag=sqrt( Nx*Nx+Ny*Ny+Nz*Nz ) 
         [0000]        Nx=Nx /mag (normalize) 
         [0000]        Ny=Ny /mag 
         [0000]        Nz=Nz /mag       an equation of a plane including the three points Pa, Pb and Pc is represented as follows:         
         [0000]      P·N=d  (B) 
         [0032]    In Equations A and B, 
         [0000]      ( P 1+ t ( P 2 −P 1))· N=d    
         [0033]    A value of t is calculated and substituted into Equation A so as to calculate an intersection point IP. 
         [0000]    
       
         
           
             
               
                 
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         [0000]        IPx=P 1 x+t ( P 2 x−P 2 x ); (x-coordinate of IP) 
         [0000]        IFy=P 1 y+t ( P 2 y−P 1 y ); (y-coordinate of IP) 
         [0000]        IPz=P 1 z+t ( P 2 z−P 1 z ); (z-coordinate of IP) 
         [0000]      −&gt;Dip value ( D )=( Paz+Pbz )/2 −IPz    
         [0035]      FIG. 3  is a construction view illustrating equipment for dip measurement according to the present invention. The dip measurement equipment includes a measurement instrument  10  for collimating a position, a personal digital assistant (FDA)  20  which a worker carries to perform a process, and a personal computer (PC)  30  to which measurement data are transmitted and stored. 
         [0036]    &lt;A Process of Measuring a Dip of an Already Constructed Power Line&gt; 
         [0037]      FIG. 4  is a flow chart illustrating a process of measuring a dip of an already constructed power line according to the present invention. 
         [0038]    First, the measurement instrument  10  is installed at a place where the two steel towers A and B can be seen to measure a dip value of a power line  1  in a state in which the power line  1  is installed at the steel towers A and B between which a dip measurement section is defined (ST  1 ). 
         [0039]    Subsequently, the measurement instrument  10  is collimated at the power line support point Pa of the steel tower A (ST  2 ), and then an “A” icon on a measurement screen of the PDA  20  as shown in  FIG. 5  is touched by a worker such that a collimated value is transmitted from the measurement instrument  10  to the PDA  20  (ST  3 ). 
         [0040]    Subsequently, the measurement instrument  10  is collimated at the power line support point Pb of the steel tower B (ST  4 ), and then a “B” icon on the measurement screen of the FDA  20  is touched by the worker such that a collimated value is transmitted from the measurement instrument  10  to the PDA  20  (ST  5 ). 
         [0041]    Subsequently, a “?” icon on the measurement screen of the PDA  20  is touched by the worker, with the result that a horizontal azimuth angle v of a dip base line is automatically calculated and displayed (ST  6 ). 
         [0042]    Subsequently, the worker horizontally adjusts the angle of the measurement instrument  10  based on the calculated horizontal azimuth angle v to set the measurement instrument  10  at the dip center point C. After that, the worker lowers the measurement instrument  10  such that the measurement instrument  10  is collimated at the power line dip point X where the measurement instrument  10  joins the power line  1 , and then touches a “dip point” icon on the measurement screen of the FDA  20 . 
         [0043]    As a result, the calculated measurement dip value is displayed on a data result screen of the FDA  20  as shown in  FIG. 6  such that the worker can confirm the dip value (ST  7 ). 
         [0044]      FIGS. 9 to 11  illustrates dip values measured by the above-described method in a state in which a station point at which the measurement instrument  10  is located is set to a base point (0, 0, 0). As can be seen from  FIG. 9 , a slope dip value of 8.160 is measured. As can be seen from  FIG. 10 , a slope dip value of 9.706 is measured. As can be seen from  FIG. 11 , a slope dip value of 9.102 is measured. 
         [0045]    &lt;A Process of Measuring a Dip of a Power Line to be Constructed&gt; 
         [0046]      FIG. 7  is a flow chart illustrating a process of measuring a dip of a power line to be constructed according to the present invention. 
         [0047]    First, the measurement instrument  10  is installed at a place where points, at which a power line will be supported, of the two steel towers A and B between which a dip measurement section is defined can be seen (ST  1 ). 
         [0048]    At this time, a worker inputs a designed dip value into a dip input column on a measurement screen of the PDA  20  as shown in  FIG. 8  (ST  1 - 1 ). 
         [0049]    Subsequently, the measurement instrument  10  is collimated at the power line support point Pa of the steel tower A at which the power line is supported (ST  2 ), and then an “A” icon on the measurement screen of the PDA  20  is touched by the worker such that a collimated value is transmitted from the measurement instrument  10  to the PDA  20  (ST  3 ). 
         [0050]    Subsequently, the measurement instrument  10  is collimated at the power line support point Pb of the steel tower B at which the power line is supported (ST  4 ), and then a “B” icon on the measurement screen of the PDA  20  is touched by the worker such that a collimated value is transmitted from the measurement instrument  10  to the PDA  20  (ST  5 ). 
         [0051]    Subsequently, a “?” icon on the measurement screen of the PDA  20  is touched by the worker, with the result that a horizontal angle and a perpendicular angle of a dip base line are automatically calculated and displayed (ST  6 ). 
         [0052]    Subsequently, the worker horizontally adjusts the horizontal angle and the perpendicular angle of the measurement instrument  10  based on the calculated horizontal angle and the calculated perpendicular angle, the measurement instrument  10  is collimated, and finally the construction of the power line is performed (ST  8 ). 
         [0053]    Meanwhile, an “a” icon and a “b” icon on the measurement screens of the PDA as shown in  FIGS. 5 and 8  are used when the power line support points Pa and Pb of the steel towers cannot be seen or are interfered with. After the measurement instrument  10  is collimated at a perpendicular line of the power line support point Pa, the “A” icon is touched, and, after the measurement instrument  10  is collimated at the power line support point Pa, the “a” icon is touched. As a result, interference due to trees or the like may be compensated for. 
         [0054]    When using the dip measurement method according to the present invention, therefore, it is possible to design dip construction more accurately and objectively than using the conventional dip measurement method in which measurement with the naked eye of each individual worker using a simple measurement instrument is performed during the construction of a power line. 
         [0055]    Also, it is possible for a single worker to perform direct measurement without an assistant worker, thereby achieving efficient management of labor. 
         [0056]    Also, it is not necessary for a worker to climb the tower, and therefore, it is possible for any one to perform measurement although he/she is not a qualified electrical engineer for power transmission, thereby preventing the occurrence of an accident. 
         [0057]    Also, it is possible to directly measure the power line dip point, which will become the dip base point, thereby eliminating the necessity of error connection. 
         [0058]    As is apparent from the above description, during the measurement of a dip of an already constructed power line or during the measurement of a dip of a power line to be constructed, the dip of the power line is automatically calculated by a measurement method using a vector calculation equation in which power line support points of two steel towers and a dip point are set to an imaginary space vector, thereby minimizing a measurement error due to individual calculation. 
         [0059]    In particular, measurement with the naked eye of each individual worker using a simple measurement instrument during the construction of the lower line is improved, and, in addition, it is possible for a single worker to perform measurement without climbing the steel tower, thereby improving working efficiency and management efficiency. 
         [0060]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.