Abstract:
A high voltage impedance device with surface leakage proof configuration is applied in a divider. Aforementioned divider is assembled by a high impedance element, an inner case body and an outer case body. The high impedance element is sealed in the inner case body and a closed interlayer between the inner case body and the outer case body is filled with noble gas as an insulating layer. While the high impedance element is applied in high voltage, the closed interlayer can prevent the current-leakage from forming impedance paralleled with the high impedance element. The current-leakage is formed on the surface of insulting portion, or is formed by moisture, dust or corona effect. Therefore, the current-leakage proof divider may maintain the stability/linearity of the voltage division and then reduce the distance between two ends of the high impedance element effectively and still maintain the linearity of measuring voltage.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the invention 
       [0001]    The present disclosure relates to a high voltage (HV) impedance device, particularly a HV impedance device with surface leakage proof configuration applied in a HV divider. 
       2. Description of the prior art 
       [0002]    For high voltage equipment, the output voltages based on the voltage division rule are derived from a high-voltage (HV) impedance device in which there are several high impedance units installed in series for measuring high voltage and calculating required voltage values. However, leakage current will be detected at a high impedance unit installed in a humid or dusty environment when voltage applied at both ends of the high impedance unit is increased gradually and up to a certain level. Moreover, a parallel circuit induced by both the leakage current and the high impedance unit has a negative effect on measured voltage which may be deviated from linearity with higher voltage applied. Therefore, a HV impedance device restricted to applications of specific voltages is large enough for linearity of output voltages based on the voltage division rule and assembled in a HV divider which features a dramatic height and other drawbacks such as delivery or movement inconvenient or collapse. 
         [0003]    With the drawbacks summarized, how to design a compact HV impedance device for linearity of measured voltages is an important technical issue. 
       SUMMARY OF THE INVENTION 
       [0004]    To solve above problems, the present disclosure offers a high voltage (HV) impedance device without leakage current in high-voltage operation. 
         [0005]    In the prior arts to measure voltage values of high-voltage equipment, a HV divider is installed between a measuring point and the reference voltage and internally provided with multiple series-connected high impedance units through which low DC voltages based on the voltage division rule are derived for measurement of high DC voltages wherein each of the multiple high impedance units can be connected to a compensation circuit in parallel for measurement of high AC voltages. 
         [0006]    With high voltage applied at both ends of a HV divider, leakage current induced by the high voltage is detected at the surface of the insulating case of the HV divider and leakage current attributed to humid or dusty environment or the corona effect is generated at two end points. In this regard, the leakage current is equivalent to generation of parasitic resistance which coordinates high impedance units inside a HV divider to induce a parallel effect. The parallel effect aggravating resistance with voltage applied increasingly worsens linearity of voltages measured in a HV divider. To solve this problem, engineers extend the length between two end points of a conventional HV divider and increase resistance of external environment for no surface leakage current. Thus, a conventional HV divider is long enough for linearity of output voltages but criticized because of some drawbacks such as movement inconvenient and collapse. 
         [0007]    To avoid these drawbacks, the present disclosure offers a HV impedance device with surface leakage proof configuration applied in a HV divider. The HV impedance device comprises a high impedance unit, an inner case and an outer case: the high impedance unit is held in the inner case; the inner case and the outer case are insulators between which some interlayers with inert gas filled inside are developed and sealed for isolation. When high DC voltage is applied at both ends of the high impedance unit, the parallel effect, which could be activated by the high impedance unit inside the inner case and leakage current induced at an insulator&#39;s surface by the high voltage as well as leakage current attributed to other factors such as humid or dusty environment and corona effect, is inactive because of isolation of inert gas inside interlayers. Thus, with the length of a high impedance unit lowered effectively, the linearity of output voltages based on the voltage division rule is still maintained and the height of a HV impedance device in an identical high-voltage condition is further reduced for convenient movement and applications. 
         [0008]    The high impedance unit inside the inner case of a HV impedance device with surface leakage proof configuration applied in a HV divider in the present disclosure has one end, which contacts high DC voltage, and the other end, which is connected to a divider resistance element in series for linearity of DC output voltages and measurement of high DC voltages in the HV divider or even measurement of high AC voltages in the HV divider with the high impedance unit (the divider resistance element) and an compensation circuit connected in parallel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a better understanding of the aforementioned embodiments of the invention as well as additional embodiments thereof, reference should be made to the Description of Embodiments below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures. 
           [0010]      FIG. 1  is an exploded schematic view of a HV impedance device in an embodiment. 
           [0011]      FIG. 2  is a schematic view of an assembled HV impedance device in an embodiment. 
           [0012]      FIG. 3  is another exploded schematic view of a HV impedance device in an embodiment. 
           [0013]      FIG. 4  is a sectional view for the second end at the bottom of a HV impedance device applied in a HV divider in an embodiment. 
           [0014]      FIG. 5  is a sectional view for the first end at the top of a HV impedance device applied in a HV divider in an embodiment. 
           [0015]      FIG. 6  is an equivalent circuit diagram for a HV impedance device applied in a HV divider in an embodiment. 
           [0016]      FIG. 7  is another equivalent circuit diagram for a HV impedance device applied in a HV divider in an embodiment. 
           [0017]      FIGS. 8 and 9  are schematic views of a HV impedance device applied in a HV divider and comprising a shrink foot device in an embodiment. 
           [0018]      FIG. 10  is an exploded schematic view of a shrink foot device in an embodiment. 
           [0019]      FIG. 11  is a perspective schematic view of a shrink foot installed in a HV impedance device. 
           [0020]      FIG. 12  is an exploded schematic view of an end-point protecting unit and a shrink foot device in a HV impedance device. 
           [0021]      FIG. 13  is a schematic view of a shrink foot device in a closing mode. 
           [0022]      FIG. 14  is a schematic view of a shrink foot device in an open mode. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    The following description is about embodiments of the present invention; however it is not intended to limit the scope of the present invention. 
         [0024]    Refer to  FIG. 1  which is an exploded schematic view illustrating a high voltage (HV) impedance device  1  with surface leakage proof configuration applied in a HV divider in an embodiment. The HV impedance device  1  is provided with an inner case  14  and an outer case  15 , both of which are insulators, between a first end  11  and a second end  12 : the inner case  14  is a hollow tube (for example, a cylindrical tube) with an inner space  140  in which a high impedance unit  13  is installed and an insulating material  140  or inert gas is filled ( FIG. 2 ); the outer case  15 , which is a hollow tube (for example, a cylindrical tube) with outer diameters at both ends greater than outer diameters of other tubes, is integrated with the inner case  14  for development of a gap taken as a closed interlayer  16  ( FIG. 2 ) to prevent leakage current at end points between the inner case  14  and the outer case  15 . 
         [0025]    The gap between the inner case  14  and the outer case  15  is an enclosed space with sealing units (for example,  0 -rings) or sealing materials filled at both ends of the inner case  14  and the outer case  15  for a sealing function; a groove  141  is configured at each of two ends of the inner case  14  for coupling of a first sealing unit  1011  so that an enclosed space, the interlayer  16  in which inert gas such as sulfur hexafluoride (SF 6 ) is filled for performance of anti-interference, reduced surface leakage current at the activated high impedance unit  13 , and surface resistance between two end points, is developed by the inner case  14  and the outer case  15 . The high impedance unit  13  is not limited to either a single high resistor or multiple high resistors installed in series; a second sealing unit  1012  is added between a cover  10  and an end point of the inner case  14  for development of multiple inter-layers  16  and effective prevention of leakage current between two end points (the first end  11  and the second end  12 ). 
         [0026]    The first end  11  and the second end  12  are electrically connected to one of conductive points  131  on the high impedance unit  13 , respectively. Moreover, the HV impedance device  1  is provided with a cover  10  which is located at the first end  11  (the second end  12 ) and has five openings, one at the center (contact opening  21 ) and four (openings  20 ) at the edge, by which each of the two covers  10  is fastened at one end of the outer case  15  with the openings  20  penetrated by fixing elements  1013  (for example, screws or bolts), wherein the outer case  15  has four mounting holes at rims of two ends which are opposite to the four openings  20  at the edge of the cover  10  for secure connection, fastening, and better stability of the first end  11  (the second end  12 ). 
         [0027]    The high impedance unit  13  consists of multiple high resistors (over 100MΩ for each) installed in series and withstanding voltage up to 10 kV. 
         [0028]    A conventional high-voltage impedance DC divider is provided with a long case between two high-resistance end points (the first end  11  and the second end  12 ) for preventions of surface resistance at the case between two high-resistance end points under high voltage and the parallel effect attributed to surface resistance and high resistance, reducing the high resistance directly, and worsening linearity of measured output voltages based on the voltage division rule. In the present disclosure, a HV impedance device  1  with surface leakage proof configuration applied in a HV divider prevents leakage current because of an insulated structure developed by the inner case  14 , inert gas inside the interlayer  16 , the outer case  15  and the covers  10 . With identical high voltage applied between the conductive points  131 , the HV impedance device  1  with surface leakage proof configuration is characteristic of a compact overall length and a downsizing effect compared with other conventional high-voltage impedance dividers. 
         [0029]    Refer to  FIG. 3 , which is a schematic view of the HV impedance device  1  applied in a HV divider in another embodiment. In the embodiment, the HV impedance device  1  is provided with two end-point protecting units  17  at two end points (the first end  11  and the second end  12 ), respectively: the end-point protecting unit  17  is a component made of a conductive material and consisting of a hollow circular and tubular protecting ring  171  and a tabular protecting board  172  that is surrounded by the protecting ring  171  and has five openings, one at the center through which one of the two end points (the first end  11  and the second end  12 ) as well as the high impedance unit  13  are linked and other four openings  174  at the rim; the five openings are opposite to the five openings  20  on the cover  10  and used to fix the protecting unit  17  on the second end  12  of the outer case  15  through four fixing elements  1013 . 
         [0030]    Refer to  FIG. 4 , which is a sectional view for the second end  12  at the bottom of the HV impedance device  1  applied in a HV divider in an embodiment. As shown in  FIG. 4 , the conductive point  131  at one end of the high impedance unit  13  inside the inner case  14  is extracted from the center (contact opening  21 ) on the cover  10  and the center of the protecting board  172  and taken as an end portion E P  which is connected to one end of a variable resistor VR (or a semi-variable resistor) at a circuit board  19  fixed on the protecting board  172 . The variable resistor VR has the other end connected to the protecting ring  171  at which a reference voltage P REF  is set for development of a series circuit by the variable resistor and the high impedance unit  13 . On the protecting ring  171 , there are two openings on the circular tubular side, one opening (opening  175 ) for a current lead introduced and connected to an end portion E P  and the other opening in which a BNC connector  173  at the other end of the current lead is embedded, so that a contact extracted from the BNC connector  173  is created for direct voltage measurement by a voltmeter (as shown in a dotted line in  FIG. 4 ) or output from an end portion E P  via a connected coaxial cable. The height of the circular and tubular protecting ring  171 , h, is above the end portion E P  and the variable resistor for no contact interference induced by a foreign object during voltage measurement. The current lead is wrapped by an insulating layer for no short circuit at the end portion E P  or the protecting ring  171 . 
         [0031]    Referr to  FIG. 5 , which is a sectional view for the first end  11  at the top of the HV impedance device  1  applied in a HV divider in an embodiment. As shown in  FIG. 5 , the center of the protecting board  172  surrounded by the protecting ring  171  allows the first end  11  and the high impedance unit  13  to be conductively connected to the end-point protecting unit  17  for convenient contact between the protecting ring  171  and measured high voltage wherein the end-point protecting unit  17  is fixed on the first end  11  in the outer case  15  when the openings  20  and the corresponding openings  174  on the protecting board  172  are penetrated by the fixing elements  1013 . 
         [0032]    Refer to  FIG. 6 , which is a DC equivalent circuit diagram for the HV impedance device  1  applied in a HV divider in an embodiment. As shown in the DC equivalent circuit diagram, the high impedance unit  13  links the variable resistor in series and further the reference voltage P REF  for measurement of high voltage V 0  with a digital or analogue voltmeter VM installed between an end point and the end portion E. 
         [0033]    Refer to  FIG. 7 , which is an AC equivalent circuit diagram for the HV impedance device  1  applied in a HV divider in an embodiment. As shown in the AC equivalent circuit diagram with architecture similar to the DC equivalent circuit diagram, the measurement of high AC voltage V 0  is available in the HV impedance device  1  when the high impedance unit  13  (the variable resistor VR also) and a resistance compensation element Cc (for example, a frequency compensation element including capacitors or inductors) are connected in parallel. 
         [0034]    Referring to  FIGS. 8 and 9 , the HV impedance device  1  applied in a HV divider in another embodiment comprises a shrink foot device  3  linking the bottom of the circular and tubular protecting board  172  at the second end  12  and having a plurality of shrink feet  33 , each of which has one end pivotally fitted at the shrink foot device  3  and is stretched or retracted horizontally when force is applied on the shrink foot  33 . Because of the shrink feet  33  stretchable/retractable horizontally, the HV impedance device  1  can be operated stably and supported in a horizontal direction particularly with the shrink feet  33  stretched. 
         [0035]    With high voltage applied at both ends, the voltage at each ohmic contact in a conventional HV impedance device is greater than voltage in environment, particularly in a humid or dusty workplace in which a leakage path is easily generated from an ohmic contact to external environment and has negative effects such as poor stability of output voltages based on the voltage division rule or parasitic resistance in parallel among ohmic contacts. Different from a conventional HV impedance device, the HV impedance device  1  with the high impedance unit  13  surrounded and protected by inert gas inside a closed interlayer  16  ( FIG. 3 ) and isolated from leakage current is characteristic of a reduced height of a HV divider and good linearity of measured voltages under same external environmental conditions. 
         [0036]    Refer to  FIG. 10 , which is an exploded schematic view of the shrink foot device  3  in the first embodiment. The shrink foot device  3  comprises a base board  31 , a gear  32 , a plurality of shrink feet  33  and a base cover  34 . The base board  31  comprises several connecting portions (for example, sockets) thereon for connecting shrink feet  33 ; the gear  32 , which is placed on one plane of the base board  31 , is driven by the shrink feet  33  for rotation relative to the base board  31 ; each shrink foot  33  comprises a pivot end  330  ( FIG. 11 ), which is pivotally fitted at a connecting portion of the base board  31  through connectors  35  for swing of the shrink foot  33 , and a gear end  331 , which is defined and engaged with the gear  32  partially for a plurality of shrink feet  33  surrounding the gear  32  peripherally; each shrink foot  33  with the other end defined as an extremity end  332  can be swung and drive the gear  32  to rotate itself and further activate other shrink feet  33  for leaving or approaching the gear  32 . 
         [0037]    The base cover  34  is mounted on the gear  32  and the shrink feet  33 ; both the gear  32  and the shrink feet  33  between the base cover  34  and the base board  31  are connected to the connecting portions (sockets) on the base board  31  with connectors  35  (a screw/nut unit or rivets), held in a storage space developed by the base cover  34  and the base board  31 , and placed on an identical plane. In another embodiment, the base board  31  has an annular exterior which matches the gear  32  with a ringlike shape as well as the shrink feet  33  coupled with the gear  32  in a closing mode. 
         [0038]    Refer to  FIG. 11 , which is a perspective schematic view of a shrink foot  33  in the present disclosure. The pivot end  330  of each shrink foot  33  is pivotally fitted at the base board  31  through connectors  35  (for example, a pivotal screw and a retaining nut) and adjacent to the gear end  331  of the shrink foot  33 ; each shrink foot  33  has an arc-shaped inner side  333  leaning on the periphery of the gear  32  in a closing mode; the gear end  331  is a curved structure driving the gear  32  to rotate in an opening mode. 
         [0039]    In another embodiment, each shrink foot  33  comprises a pad body  3321  on one plane of the extremity end  332 ; relatively, the base cover  34  comprises a plurality of placing openings  341  indenting from the rim for holding the pad bodies  3321  in a closing mode. 
         [0040]    Furthermore, the base board  31  has the other plane fixed at another device through contacts. Refer to  FIG. 12 , which is an exploded schematic view of the shrink foot device  3  in the second embodiment. In the second embodiment similar to the first embodiment, the shrink foot device  3  further comprises an end-point protecting unit  17  mounted on the other plane of the base board  31  and comprising the protecting ring  171  and the protecting board  172  on which some ohmic contacts are designed. 
         [0041]    Refer to  FIG. 13 , which is a schematic view of the shrink foot device  3  in a closing mode. Referring to  FIG. 14 , the extremity end  332  of a shrink foot  33  is first swung and extracted from the shrink foot device  3  under control of a user and followed by other shrink feet  33 , which are driven and swung by the gear  32  with the gear ends  331  of the shrink feet  33  rotating, for unfolding all shrink feet  33  quickly. On the other hand, to retract the shrink foot device  3 , a user needs to swing and push the extremity end  332  of a shrink foot  33  toward the shrink foot device  3  and retract other shrink feet  33  through the gear  32  quickly. 
         [0042]    In the present disclosure, the shrink foot device  3  is a footstand of the HV impedance device  1  and connected to one end of the HV impedance device  1  through connectors  35 . To remove or place the HV impedance device  1  that is a heavy appliance usually, a user should extract a single shrink foot  33  at first by which other shrink feet  33  are driven and stretched for development of a stable footstand; to retract the shrink foot device  3 , a single shrink foot  33  should be pushed into the footstand in which all shrink feet  33  can be held. Thus, the shrink foot device  3  coordinates other devices for better stability of the HV impedance device  1  effectively. 
         [0043]    The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.