Abstract:
Systems and methods are disclosed for non-intrusively inspecting circuit breakers, which may include one or more connector assemblies. An X-ray unit may be placed at a first location around the circuit breaker while at least one digital imaging plate may be placed at a second location around the circuit breaker. The X-ray unit may generate X-rays, where at least a portion of the generated X-rays traverse a plane that includes at least a portion of the connector assembly and at least a portion of the at least one digital imaging plate. The image that includes at least a portion of the connector assembly may be retrieved from the digital imaging plate and inspected to determine a status of the circuit breaker.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Aspects of the present invention relate generally to circuit breakers, and more particularly, to systems and methods for non-intrusive inspections of high-voltage circuit breakers.  
         [0003]     2. Description of the Related Art  
         [0004]     High-voltage circuit breakers play an important protective role for high power machinery. Over time, however, these circuit breakers may wear down or experience other malfunctions and problems such as internal arcing. Therefore, these high-voltage circuit breakers must be routinely inspected for problems.  
         [0005]     Traditionally, the inspection process has been costly and disruptive to customers. In order to inspect the internal components of the circuit breakers, they must be disassembled. During this disassembly process, the gases utilized internally in the circuit breaker to control arcing, such as sulphur hexafluoride gas, must be carefully contained because they are typically environmentally unsafe. Upon completion of the inspection process, the circuit breaker is reassembled and refilled with gas. However, during the gas refill process, the purity of the gas may oftentimes be compromised, therefore reducing the operational reliability of the circuit breaker. Indeed, experience has shown that the disassembly and reassembly of circuit breakers may reduce their overall operational reliability.  
         [0006]     Thus, such an inspection process described above is deemed to be costly and disruptive to customers. Accordingly, there is a need in the industry for non-intrusive inspections of circuit breakers that are less costly and less disruptive than traditional methods.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0007]     Radiography equipment may be utilized to inspect circuit breakers at a customer site. The use of the radiography equipment allows inspections of these circuit breakers to be performed at a customer site without requiring the disassembly and reassembly of circuit breakers. Instead, the circuit breaker may be inspected by examining images of the internal components obtained through the radiography equipment.  
         [0008]     According to one embodiment of the invention, there is method for non-intrusively inspecting circuit breakers. The method includes receiving at least one circuit breaker, where the circuit breaker includes a tank having an interior with one or more connector assemblies, placing an X-ray unit at a first location of an exterior of the tank, and placing at least one digital imaging plate at a second location of the exterior the tank. The method further includes generating X-rays from the X-ray unit, such that at least a portion of the generated X-rays traverse a plane that includes at least a portion of the connector assembly and at least a portion of the at least one digital imaging plate, and retrieving an image from each digital imaging plate, wherein each image includes at least a portion of the connector assembly.  
         [0009]     According to an aspect of the invention, the at least one circuit breaker may be positioned at a customer location. According to another aspect of the invention, the method may further include inspecting the image for determining a status of the at least one circuit breaker. The connector assembly may include one or both of a stationary side contact and a moving side contact, and a template may be overlayed over the image of the stationary side contact for determining wear of the stationary side contact. According to another aspect of the invention, retrieving an image may include retrieving an image from each digital imaging plate via at least one scanner unit operable with the digital imaging plate. The image may be directly manipulated on a computer.  
         [0010]     According to another embodiment of the invention, there is a system for non-intrusive inspections of circuit breakers. The system includes a circuit breaker having at least one connector assembly, an X-ray unit at a first position of the circuit breaker for transmitting X-ray energy, where the transmitted X-ray energy is directed towards at least a portion of the at least one connector assembly, a digital imaging plate at a second position of the circuit breaker substantially opposite the first position for receiving the transmitted X-ray energy, where the digital imaging plate stores an image that is defined, at least in part, by the received X-ray energy, and a scanner unit in communication with a computer for retrieving the stored image from the digital imaging plate.  
         [0011]     According to an aspect of the invention, the stored image captures at least a portion of the at least one connector assembly. The portion of the at least one connector assembly may include a stationary side contact. According to another aspect of the invention, the system further includes a template, where the template is suitable for overlaying the retrieved image for determining wear on the stationary side contact. The template may include a plurality of concentric arcs drawn at different scales for determining wear on a tip of the stationary side contact. According to yet another aspect of the invention, the first position may be below the at least one connector assembly and the second position may be above the at least one connector assembly. Alternatively, the first position may be above the at least one connector assembly and the second position may be below the at least one connector assembly.  
         [0012]     According to another embodiment of the present invention, there is a method for on-site inspections of high-voltage circuit breakers. The method includes receiving a circuit breaker having a tank encapsulating at least one connector assembly, placing an X-ray unit at a first position exterior to the tank, placing a cassette having a digital imaging plate at a second position exterior to the tank, where the first and second positions lay on a plane that includes at least a portion of the at least one connector assembly, transmitting X-rays from the X-ray unit, where at least a portion of the X-rays traverses from the X-ray unit at the first position to the cassette at the second position, and retrieving an image from the digital imaging plate.  
         [0013]     According to an aspect of the present invention, the method further includes disengaging at least one connector assembly such that the moving side contact and the stationary side contact are in a locked-out position. According to another aspect of the present invention, the cassette further includes one or more filtering screens. According to another aspect of the invention, the method further includes analyzing the image to determine a status of the circuit breaker, where analyzing the image includes enlarging the image on a computer. Analyzing the image may also include overlaying a template over the image to determine the extent of wear of at least a portion of the connector assembly. According to yet another aspect of the invention, the plane is perpendicular to at least a portion of the at least one connector assembly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     Having thus described aspects of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:  
         [0015]      FIGS. 1A and 1B  illustrate exemplary system overview diagrams in accordance with exemplary embodiments of the present invention.  
         [0016]      FIG. 2  illustrates an exemplary connector assembly in accordance with exemplary embodiments of the present invention.  
         [0017]      FIG. 3A  illustrates a cross-sectional view of the X-ray unit, digital imaging plates, and circuit breaker in  FIG. 1A  in accordance with an embodiment of the present invention.  
         [0018]      FIG. 3B  illustrates a cross-sectional view of the X-ray unit, digital imaging plates, and circuit breaker in  FIG. 1B  in accordance with an embodiment of the present invention.  
         [0019]      FIGS. 4A and 4B  illustrate digital X-ray images obtained during the inspection process in accordance with embodiments of the present invention.  
         [0020]      FIG. 5  illustrates templates utilized to analyzing digital X-ray images in accordance with embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.  
         [0022]     Embodiments of the present invention are directed towards the use of radiography equipment, and in particular digital X-ray imaging equipment, for inspecting internal components of high-voltage circuit breakers. The use of digital X-ray imaging equipment allows digital images of these internal components to be obtained without moving or disassembling the circuit breakers. These X-ray images may then be digitally enhanced or manipulated as necessary in order to inspect the integrity of the internal components. The circuit breakers and the processes for utilizing the X-ray imaging equipment to inspect these circuit breakers will now be discussed below with reference to  FIGS. 1-5 .  
         [0023]     High-voltage circuit breaker overview  
         [0024]      FIGS. 1A and 1B  each illustrate an exemplary system overview of a high-voltage circuit breaker in accordance with embodiments of the present invention. In particular,  FIGS. 1A and 1B  show a high-voltage circuit breaker  100 . The circuit breaker  100  may include an interrupter tank  102  that serves as the exterior housing for the circuit breaker  100 . The interrupter tank  102  may vary in thickness and/or size depending on the desired operating specifications (e.g., voltage, amps, pressure, and the like) of the high-voltage circuit breaker  100 . For example, the interrupter tank  102  may be 914.4 mm (i.e., 36 inches) in diameter with a thickness of 0.375 m for a 362-kV circuit breaker according to an exemplary embodiment. Interrupter tank  102  may be fabricated of steel, carbon steel, and other alloys and materials as known to one of ordinary skill in the art. The interrupter tank  102  may be physically stabilized during operation by one or more supports  104 , which may be metal legs or stands according to an embodiment of the invention.  
         [0025]     In addition, the circuit breaker  100  may include a man way or other inspection port  106 . While inspection port  106  is shown as open in  FIGS. 1A and 1B  for illustrative purposes, it typically remains sealed during normal operation of the circuit breaker. According to an exemplary embodiment of the invention, the interrupter tank  102  may also contain gas, such as sulfur hexafluoride (SF 6 ) gas or other insulating gas, to prevent internal arcing during operation of the circuit breaker  100 .  
         [0026]     As shown through the open inspection port  106  of  FIGS. 1A and 1B , the circuit breaker  100  may include one or more contacts  108 ,  110  that form connector assemblies that comprise at least a portion of the internal components that may be inspected in accordance with an embodiment of the present invention. In particular, the circuit breaker  100  may include one or more stationary side contacts  108  (e.g., a male connector), each of which may be coupled to the corresponding one or more moving side contacts  110  (e.g., a female connector). According to an illustrative embodiment, there may be three sets of stationary side contacts  108  and moving side contacts  110 . During normal operation of the circuit breaker  100 , the stationary side contact  108  would be in communication with the moving side contact  110 . However, when a fault is detected or when the circuit breaker is being inspected, the stationary side contact  108  and moving side contact  110  may be disengaged in a locked-out position as shown in  FIGS. 1A and 1B .  
         [0027]      FIG. 2  illustrates a more detailed view of the stationary side contact  108  and moving side contact  110  shown through the open inspection port  102  in  FIGS. 1A and 1B . The stationary side contact  108  may be surrounded by the main contact  204 , which may be known as the “bird cage.” At an end of the main contact  204  are tungsten blocks  206 . The area  202 , which includes the shank and tip of the stationary side contact  108 , may be one area of interest that may be inspected in accordance with embodiments of the present invention. In particular, the tip and/or shank in area  202  may indicate signs of wear that may require maintenance. Likewise, the moving side contact  110  may include a guide  208  for facilitating the connection between the moving side contact  110  with the stationary side contact  108 . According to an embodiment of the invention, the guide  208  may be fabricated of Teflon. Like the stationary side contact  108 , the moving side contact  110  may also be inspected for signs of wear that may require maintenance, according to exemplary embodiments of the present invention.  
         [0028]     Radiography Imaging System  
         [0029]      FIGS. 1A and 1B  also disclose exemplary radiography equipment, and in particular X-ray equipment, for inspecting the internal components of the circuit breaker  100 . In particular, an X-ray unit  112  may be utilized in conjunction with one or more digital imaging plates  116 ,  118 ,  124 ,  126  of  FIGS. 1A and 1B  to obtain images for one or more of the stationary side contacts  108  and moving side contacts  110 . The X-ray unit  112  and corresponding digital imaging plates  116 ,  118 ,  124 , or  126  may be placed in various positions around the interrupter tank  102  without departing from embodiments of the present invention.  
         [0030]     According to an exemplary embodiment of the invention, one or more of the digital imaging plates  116 ,  118 ,  124 , and  126  shown in  FIGS. 1A and 1B  may contain photosensitive storage phosphors that retain the latent image determined from the received X-ray energy from the X-ray unit  112 . The digital imaging plates  116 ,  118 ,  124 ,  126  may be approximately 35 cm×43 cm (14″×17″), 35 cm×35 cm (14″×14″), according to an exemplary embodiment of the present invention. One of ordinary skill in the art will recognize that may other sizes of digital imaging plates are available and may be utilized as necessary.  
         [0031]     Before positioning one or more of the digital imaging plates  116 ,  118 ,  124 ,  126  around the interrupter tank  102 , one or more of the digital imaging plates  116 ,  118 ,  124 ,  126  may be placed in cassettes. According to an embodiment of the invention, the cassettes may be semi-rigid cassettes. Additionally, one or more screens may be placed in front of the digital imaging plates  116 ,  118 ,  124 ,  126  (“front screens”) while one or more screens may be placed behind the digital imaging plates  116 ,  118 ,  124 ,  126  (“back screens”) for filtering and/or intensifying the received X-ray energy from X-ray unit  112 . The one or more front screens and back screens may be fabricated from metallic foil, lead, or other filtering or intensifying material. The front screen may filter out undesirable longer wavelengths while the back screen may prevent back scattering, thereby producing clearer images obtained from one or more of the digital imaging plates  116 ,  118 ,  124 ,  126 . The front or back screens may vary in thickness, but may be 0.254 mm (i.e., 0.010 inches) according to an exemplary embodiment of the invention. One of ordinary skill in the art will recognize that other digital imaging plates may be utilized in accordance with embodiments of the invention, including those that utilize other compositions besides photosensitive storage phosphors.  
         [0032]     Once one or more of the digital imaging plates  116 ,  118 ,  124 , and  126  shown in  FIGS. 1A and 1B  have been exposed to the X-ray energy from X-ray unit  112  such that the desired latent image has been stored, the digital imaging plates  116 ,  118 ,  124 ,  126  may be processed by a scanner unit  120  to retrieve the latent image in digital form. According to one embodiment, the scanner unit  120  may be a General Electric (GE) CR100 desktop computed radiography scanner operating in conjunction with the Rhythm suite of software provided by GE Inspection Technologies. The scanner unit  120  may retrieve each latent image stored on digital imaging plates  116 ,  118 ,  124 ,  126  as a digital image viewable on computer  122 . The scanner unit  120  may retrieve the latent image by scanning the digital imaging plates  116 ,  118 ,  124 ,  126  with one or more laser beams. The laser beam may cause the latent image stored in the photosensitive storage phosphors in the digital imaging plates  116 ,  118 ,  124 ,  126  to be released as visible light. The visible light can then be captured by the scanner unit  120  and converted into a digital bit scream that encodes the digital image for the computer  122  according to an embodiment of the invention.  
         [0033]     The digital image can then be modified or manipulated via the computer  122 . For example, one or more filtering algorithms may be performed on the digital image to enhance the image. The digital image can also be enlarged to view the area of interest. Many other modifications or manipulations can be performed on the digital image as known to one of ordinary skill in the art. In addition or in the alternative, the digital image may also be printed, perhaps as a photograph, in exemplary embodiments of the present invention.  
         [0034]     Exemplary Inspection Process  
         [0035]     1. Positioning  
         [0036]     In accordance with an exemplary embodiment of the present invention, the X-ray unit  112  may be generally positioned under the stationary side contacts  108  and moving side contacts  110  around the interrupter tank  102  as shown in  FIG. 1A . If the X-ray unit  112  were positioned as shown in  FIG. 1A , then the digital imaging plates  116 ,  118  may generally be placed generally above the stationary side contacts  108  and moving side contacts  110 . According to an aspect of the invention, the X-ray unit  112  and the digital imaging plates  116 , 118  may be separated by less than 180 degrees around the interrupter tank  102  where the stationary side contacts  108  and moving side contacts  110  are not centered in the interrupter tank  102 . Alternatively, according to another aspect of the invention, the X-ray unit  112  and the digital imaging plates  116 , 118  may be separated by about 180 degrees around the interrupter tank  102 . The X-rays originating from the X-ray unit  112  may be captured and/or recorded by one or more corresponding digital imaging plates  116 ,  118 . For example, when inspecting stationary side contact  108 , X-ray unit or unit  112  may be positioned in an approximately perpendicular plane  115  that includes the desired portion of the stationary side contact  108 , where the emitted X-rays from the X-ray unit or unit  112  are recorded on digital imaging plate  116 . Similarly, the approximately perpendicular plane  117  may be utilized when inspecting the moving side contact  110 .  
         [0037]      FIG. 3A  shows a cross-sectional view of the X-ray unit  112 , digital imaging plates  116 ,  118 , and circuit breaker  100  taken along line &#39; 3 A-&#39; 3 A in  FIG. 1A . As shown in  FIG. 3A , the connector assembly  302  which include the stationary side contact  108  and the moving side contact  110  may not necessarily be centered in the interrupter tank  102 . The X-ray unit  112  will then be generally placed below the connector assembly  302  while the digital imaging plate  116  or  118  will generally be placed above the connector assembly  302 . A perpendicular shot will then be taken by the X-ray unit such that the shot is substantially perpendicular to the stationary side contact  108  or the moving side contact  110 . In accordance with an embodiment of the present invention, one or more perpendicular shots will be taken for each stationary side contact  108  and moving side contact  110  that is to be inspected. Because the tip of the stationary side contact  108  may be obscured by the tungsten blocks  206  shown in  FIG. 2 , the X-ray unit  112  and corresponding digital imaging plate  116  or  118  may be positioned such that the perpendicular shot does not block a view of the tip of the stationary side contact  108 .  
         [0038]     Likewise, in an alternative embodiment of the present invention, as shown in  FIG. 1B , the X-ray unit  112  may instead be generally positioned above the stationary side contacts  108  and moving side contacts  110  around the interrupter tank  102 . As shown in  FIG. 1B , the corresponding digital imaging plates  124 ,  126  may then be generally positioned below the stationary side contacts  108  and moving side contacts  110 . According to an aspect of the invention, the X-ray unit  112  and the digital imaging plates  124 ,  126  may be separated by less than 180 degrees around the interrupter tank  102  where the stationary side contacts  108  and moving side contacts  110  are not centered in the interrupter tank  102 . Alternatively, according to another aspect of the invention, the X-ray unit  112  and the digital imaging plates  124 ,  126  may be separated by about 180 degrees around the interrupter tank  102 . For example, the X-ray unit  112  may be positioned in an approximately perpendicular plane  130  that includes the desired portion of the moving side contact  110 , where the emitted X-ray energy from the X-ray unit  112  is captured and/or recorded on digital imaging plate  124 . Similarly, the approximately perpendicular plane  128  may be utilized when inspecting the stationary side contact  108 .  
         [0039]      FIG. 3B  shows a cross-sectional view of the X-ray unit  112 , digital imaging plates  124 ,  126 , and circuit breaker  100  taken along line &#39; 3 B-&#39; 3 B shown in  FIG. 1B . The X-ray unit  112  will then be generally placed above the connector assembly  302  while the digital imaging plate  124  or  126  will generally be placed above the connector assembly  302 . A perpendicular shot will then be taken by the X-ray unit such that the shot is substantially perpendicular to the stationary side contact  108  or the moving side contact  110 . Again, one or more perpendicular shots will be taken for each stationary side contact  108  and moving side contact  110  that is to be inspected. Because the tip of the stationary side contact  108  may be obscured by the tungsten blocks  206  shown in  FIG. 2 , the X-ray unit  112  and corresponding digital imaging plate  116  or  118  may be positioned such that the perpendicular shot does not block a view of the tip of the stationary side contact  108 .  
         [0040]     One of ordinary skill in the art will recognize that other variations in the positioning of the X-ray unit  112  and digital imaging plates for the image shots are possible. For example, the X-ray unit and the corresponding digital imaging plates may be positioned on a horizontal plane covering one or more of the stationary side contacts or moving side contacts. Where necessary, a stand  114 , crane, or other elevating means may be utilized to placed the X-ray unit  112  in the desired position according to an exemplary embodiment of the present invention.  
         [0041]     While the above-described process discloses inspecting the stationary side contacts  108  and/or moving side contacts  110 , one of ordinary skill in the art will readily recognize that other inspections for circuit breaker  100  may be performed. For example, the interrupter tank  102  of circuit breaker  100  may be inspected using the above-described process for the detection of foreign objects.  
         [0042]     2. Radiography Equipment Operating Parameters  
         [0043]     According to one embodiment of the invention, the operating parameters (e.g., intensity, time, and film to focal distance (FFD), etc.) of the X-ray energy from X-ray unit  112  to one or more digital imaging plates  116 ,  118 ,  124 ,  126  may vary depending at least in part on the size (e.g., diameter, thickness, etc.) of the interrupter tank  102  of the circuit breaker  100 , and the density of the component to be inspected (e.g., male connector, female connector, etc.). As an example, for a carbon steel interrupter tank  102  with a 914.4 mm (i.e., 36 inches) diameter and a thickness of 0.375 m, the exposure of one or more of digital imaging plates  116 ,  118 ,  124 ,  126  from X-ray unit  112  may be generally between approximately 200 KV-300 KV at approximately 14-22 milliamp minutes (MAM), or more specifically between approximately 240 KV-270 KV at approximately 15-21 MAM. In particular, when the stationary side contact  108  is being inspected, the X-ray unit  112  may emit X-ray energy at approximately 240 KV for approximately 15 MAM according to an exemplary embodiment. On the other hand, when the moving side contact  110  is being inspected, the X-ray unit  112  may emit X-ray energy at approximately 240 KV for approximately 15 MAM according to an exemplary embodiment. In addition, the FFD, which may depend at least in part on the size of the interrupter tank  102 , may be approximately 152 cm (e.g., 60 inches) in the exemplary embodiment. Many other variations will be well-known to one of ordinary skill in the art  
         [0044]     3. Analysis of Digital Images  
         [0045]      FIGS. 4A and 4B  disclose exemplary digital images obtained in accordance with embodiments of the present invention. In particular,  FIG. 4A  shows a digital X-ray image of the moving side contact  110  and  FIG. 4B  shows a digital X-ray image of the stationary side contact  108 . The digital images can also be modified, manipulated, enhanced, and/or printed via the computer  122  as necessary. The digital images shown in  FIGS. 4A and 4B  may be analyzed to determine if any maintenance needs to be performed on the moving side contact  110  and/or the stationary side contact  108 . In particular,  FIG. 4A  may be examined to determine deformation of the moving side contact  110  along with pitting on the Teflon guide  208 . With respect to the stationary side contact  108 , the shank and tip shown in area  202  may be examined for wear and “arc striking.” 
         [0046]     In accordance with exemplary embodiments of the present invention, templates may also be utilized to determine the extent of wear on the tip of the stationary side contact  108 . Referring to  FIG. 5 , the image of the tip of the stationary side contact  108  may be compared to the templates shown in  FIG. 5 . The templates in  FIG. 5  show scaled versions of outlines of stationary side contacts  108 . In an exemplary embodiment of the present invention, there templates may be scaled from an actual size to about 35% larger than actual size as shown in  FIG. 5 . One of ordinary skill in the art will recognize that many other scalings can be utilized. Each of these templates shows concentric arc patterns that can be used to determine the extent of wear on the tip of the stationary side contact  108 . More specifically the image of the tip of the stationary side contact  108  can be aligned to the appropriate template shown in  FIG. 5 , and the concentric arcs allows a determination to be as to the amount of wear (e.g., distance between concentric arcs=1 mm) on the tip.  
         [0047]     According to one embodiment of the present invention, the template shown in  FIG. 5  can be printed on a transparency. The transparency can then be overlaid over an image of the tip of the stationary side contact  108 . The correctly-scaled template on the transparency will be placed over the image of the tip of the stationary side contact  108 . The concentric arcs on the correctly-scaled template will then be utilized to determine the extent of wear on the tip of the stationary side contact  108 .  
         [0048]     In accordance with another embodiment of the present invention, a computer algorithm on computer  122  may digitally determine the extent of wear on the digital image of the stationary side contact  108 . In one embodiment, the computer  122  may receive a digital image of the tip of the stationary side contact  108 . The computer algorithm may apply digitally-stored templates over the digital image of the tip in order to determine the correct scaling. The computer algorithm will then determine the difference between the expected tip curvature and the actual tip curvature for determining wear on the tip. Many other variations of the computer algorithm will be readily recognized by one of ordinary skill in the art.  
         [0049]     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.