Abstract:
A Sensor for detecting radio-frequency oscillations of a voltage, and an arrangement of a sensor for detecting radio-frequency oscillations of the voltage in a line. The sensor ( 10 ) has a capacitor ( 15 ) whose first connection can be connected to the line ( 11 ). According to the invention, the second connection of the capacitor is associated with a current transformer ( 18 ) and a bush ( 19 ) for outputting a measured signal. The invention furthermore provides for a sensor ( 10 ) to be arranged in an intermediate space ( 13 ) between the line ( 11 ) and a shield ( 12 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is the National Stage of International Application No. PCT/DE00/03318 and claims the benefit thereof. This application claims the benefit of Federal Republic of Germany Application No. 19949172.0, filed Oct. 12, 1999, both incorporated by reference herein in their entirety.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to a sensor for detecting radio-frequency oscillations of the voltage in a line, with the sensor having a capacitor whose first connection can be connected to the line. A sensor such as this is used for detecting radio-frequency voltage oscillations in power stations.  
         BACKGROUND OF THE INVENTION  
         [0003]    Discharges and flash-overs can occur for various reasons in power stations. These lead to radio-frequency pulses, which are transmitted to one or more lines. In order to protect a power supply with high quality, these pulses must be detected and evaluated.  
           [0004]    Sensors for detecting such oscillations are known, which have a capacitor whose first connection can be connected to the line. One or more resistors are associated with the second connection of this capacitor. The voltage drop across the resistor or resistors is measured, and is used to detect the radio-frequency oscillations. The known sensors have the disadvantage that a number of separate components are required. The space requirement for fitting these components is comparatively high. In addition, assembly is costly.  
         SUMMARY OF THE INVENTION  
         [0005]    One object of the present invention is thus to provide a sensor which has fewer components, requires less space, and is easier to install.  
           [0006]    According to the invention, this object is achieved for a sensor of the type mentioned initially in that a second connection of the capacitor is associated with a current transformer and a bush for outputting a measured signal.  
           [0007]    The sensor according to the invention is smaller than the known sensors. It can be produced as a compact unit, and can thus easily be installed. In particular, there is no longer any need to install separate components successively, so that the installation process is considerably simplified and speeded up.  
           [0008]    The second connection is advantageously also associated with a spark gap, which is connected in parallel with the current transformer. When unacceptably high loads occur, a short circuit occurs in the spark gap, and the current transformer is protected against being overloaded.  
           [0009]    In one advantageous development, the second connection of the capacitor is grounded via the current transformer and the spark gap. The oscillations recorded by the capacitor are dissipated through the ground path, and only the measured signal is emitted.  
           [0010]    According to one advantageous refinement, the sensor has an elastically mounted element for pressing against the line, and this element is connected to the first connection of the capacitor. The elastic mounting compensates for any manufacturing or installation tolerances.  
           [0011]    According to one advantageous development, the element is spherical and is loaded by a compression spring. The use of a spherical element results in a defined contact area being provided between the element and the line. The compression spring that is used for contact pressure can be produced and installed easily, so that the production and installation costs are reduced.  
           [0012]    The position of the element can advantageously be adjusted with respect to the sensor, in particular in the longitudinal direction of the sensor.  
           [0013]    In consequence, the contact separation between the element and the line is adjustable, for matching to the respective application. In particular, a single sensor can be used for a number of different applications.  
           [0014]    The invention furthermore relates to an arrangement of a sensor, in particular of a sensor as described above, on a line for detecting radio-frequency oscillations of the voltage, with the line being surrounded by a shield. According to the invention, the sensor is arranged in an intermediate space between the line and the shield. This arrangement requires only a small amount of space, is simple to install, and can be retrofitted to existing systems.  
           [0015]    The sensor is advantageously attached to the shield. No additional components are required, so that the design and installation are simplified, and the cost is reduced.  
           [0016]    In one advantageous refinement, the sensor has a bush for outputting a measured signal, and this bush is arranged outside the shield. Cables for tapping off the measured signal can be connected to the bush quickly and easily, and can be laid outside the shield.  
           [0017]    According to one advantageous development, the sensor is arranged on a connecting plate which can be attached to the shield. The sensor can be installed on the connecting plate in advance, and the connecting plate is then attached to the shield. This speeds up the installation process.  
           [0018]    The shield is advantageously provided with an insert for attachment of the sensor. This insert can be retrofitted to existing shields, so that the sensor according to the invention and the arrangement according to the invention can also be installed retrospectively in already existing systems.  
           [0019]    According to one advantageous refinement, the shield is grounded. No special safety measures are then necessary in order to prevent contact with the shield. Furthermore, the grounding of the capacitor which is provided according to the invention can be produced via the shield. There is no need for any separate grounding cables.  
           [0020]    Advantageous refinements and developments of the invention are described in the dependent claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The invention will be described in more detail in the following text with reference to an exemplary embodiment which is illustrated schematically in the drawing, in which:  
         [0022]    [0022]FIG. 1 shows a schematically illustrated arrangement of a sensor according to the invention;  
         [0023]    [0023]FIG. 2 shows a schematic illustration of the circuit on which the sensor is based;  
         [0024]    [0024]FIG. 3 shows a complete schematic illustration of the arrangement according to the invention; and  
         [0025]    [0025]FIG. 4 shows an enlarged illustration of a contact point of the sensor. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    [0026]FIG. 1 shows, schematically, a sensor  10  according to the invention, which is held in an intermediate space  13  between a live line  11  and a grounded shield  12 . The sensor  10  has a contact point  14 , a capacitor  15 , which is held on both sides by plates  16 ,  17  composed of aluminum, a current transformer  18  and a bush  19 . The bush  19  is arranged outside the shield  12 .  
         [0027]    The lower plate  17  is connected to a connecting plate  20  via an insulated intermediate plate  23 . The intermediate plate  23  is used for isolation of the capacitor  15 . Screws, which are illustrated schematically, are used for attachment.  
         [0028]    The sensor  10  is attached to an insert  21  via the connecting plate  20 . The insert  21  is connected to the shield  12  in a manner which is not illustrated in any more detail, for example via a welded joint. It is once again attached by means of schematically illustrated screws. One or more seals  22  is or are arranged between the connecting plate  20  and the insert  21 , for shielding and for oscillation damping.  
         [0029]    The contact point  14  is adjustable as shown by the arrow  27  in the direction of a longitudinal axis  26  of the sensor  10 . This makes it possible to adjust the contact separation between the contact point  14  and the line  11 .  
         [0030]    The sensor  10  is held completely in the intermediate space  13 . The bush  19  is accessible from outside the shield  12 , so that only a small amount of effort is required to lay further cables. Furthermore, the entire sensor  10  has a compact construction and can be completely installed in advance, together with the connecting plate  20 . The insert  21  can be retrofitted in already existing shields  12 , so that the sensor  10  according to the invention can also be fitted retrospectively, with only a small amount of effort.  
         [0031]    [0031]FIG. 2 shows a schematic illustration of the circuit that is used. The capacitor  15  of the sensor  10  is connected to the line  11  via a first connection  24 . The connection is made via the contact point  14 . The second connection  25  of the capacitor  15  is associated with the current transformer  18  as well as the bush  19  and a spark gap  30 . The spark gap  30  is connected in parallel with the current transformer  18 , between its connections  28 ,  29 . Grounding is provided downstream from the connection  29 . Voltage oscillations which are detected in the line  11  produce a signal which is emitted to the bush  19  via the capacitor  15  and the current transformer  18 . The signal can be tapped off at the bush  19 , and can be supplied to an evaluation unit, which is not illustrated in any more detail. If unacceptably high loads occur, a short circuit occurs in the spark gap  30 . This reliably prevents damage to the current transformer  18 .  
         [0032]    [0032]FIG. 3 shows a schematic overall illustration of the arrangement of the sensor  10  according to the invention. The sensor  10  is held entirely in the intermediate space  13 . Only the insert  21  as well as the connecting plate  20  and the bush  19  project outward beyond the shield  12 . The space which is additionally required for fitting the sensor  10  is thus minimal.  
         [0033]    [0033]FIG. 4 shows the contact point  14  of the sensor  10  enlarged. The contact point  14  has an outer housing  31 , in which an inner housing  32  is held. The outer housing  31  and the inner housing  32  are connected to one another via a thread, which is not illustrated in any more detail. Adjustment can thus be carried out, as shown by the arrow  27 , along the longitudinal axis  26  of the sensor  10  by rotating the inner housing  32  with respect to the outer housing  31 .  
         [0034]    A sphere  33  is arranged in the inner housing  32 , and is loaded by a compression spring  34 . When installed, the sphere  33  makes contact with the line  11 , and is connected via a connection  35  to the first connection  24  of the capacitor  15 . Any voltage oscillations which occur in the line  11  are absorbed by the sphere  33 , and are passed on to the capacitor  15  via the connections  35 ,  24 , and from the capacitor  15  via the current transformer  18  to the bush  19 . The adjustment capability in the direction of the longitudinal axis  26  as shown by the arrow  27  allows the contact separation to be adjusted. The use of the sphere  33  avoids local damage to the line  11  and enlargement of the contact surface area between the line  11  and the sphere  33 . This ensures an essentially constant contact surface area over lengthy time periods.  
         [0035]    The capacitance of the capacitor  15  as well as the configuration of the current transformer  18  and of the spark gap  30  depend on the individual situation. However, the capacitance of the capacitor  15  can normally be chosen to be less than in existing sensors. If, for example, a voltage of 30 kV is applied to the line  11  then, according to the invention, a capacitance of only 10 nF is now required, in comparison to 100 nF in the past. In this case, the spark gap  30  is designed for 400 V.  
         [0036]    The sensor  10  according to the invention has a compact construction, and can be installed quickly and easily. There is no longer any need to fit separate components. The arrangement according to the invention considerably reduces the space required for fitting the sensor  10 . Furthermore, it can be retrofitted into already existing systems, with minimal effort.