Abstract:
A system and method that detects and locates defects in solid insulation is disclosed. The system and method solves difficult detection and location problems, such as when the break is not close enough to another exposed conductor to fail a high-voltage breakdown test. The system tests insulated conductors using a high-voltage breakdown tester, a connection integrity tester capable of identifying unintended connections, a means of connecting the tester to the conductors, and an inflatable bladder that causes a conductive material attached to the two testers to conform to the shape of the conductor. The inflatable bladder may be used as part of a gas or liquid dispensing system for enhancing the effectiveness of the test.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims the benefit of earlier-filed U.S. patent application Ser. No. 60/209,942, filed Jun. 7, 2000, for “Device for Detecting and Locating Insulation Defects,” which is incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to devices and methods used to detect and locate defects in electric circuitry. More specifically, the present invention relates to devices and methods that locate defects in solid insulation covering electrical circuitry and wiring.  
           [0004]    2. Description of Related Art  
           [0005]    Presently, the industry commonly coats conductive wire or bundled cables with a solid insulating material to provide electrical isolation between wires. In addition, the insulation material also helps provide thermal insulation, strain relief, protection against mechanical damage and abrasion, chemical and corrosion protection, sealing, and limit signal distortion. The thickness and dielectric characteristics of these solid insulation materials are specifically chosen to maintain isolation, limit shock danger and signal distortion, while increasing power or signal delivery efficiencies seen in the conductor. As wire is used for a wide variety of purposes, there are differences in the type of insulation used. For example, a data communication cable may use a Teflon® FEP coat to promote transmission and provide physical protection.  
           [0006]    Occasionally the solid insulation surrounding a conductive wire or cable is damaged or defective and exposes the conductors. These defects in the insulation may be very small and difficult to see. Defects, such as cracking, often result from mechanical stresses imposed upon conductors having stiff or brittle insulation. Embrittlement of the solid insulation is a result of the normal aging of the insulation. Aging is often accelerated by operation at high temperatures over an extended period of time. The mechanical stresses may be caused by movement, short-circuit currents, thermal expansion and contraction of the conductors, and vibration. While the dielectric strength of insulation is generally not significantly reduced by brittleness alone, loss of isolation can result from the development of cracks. For this reason, close inspection of insulation should be made at frequent intervals, and repairs made as necessary.  
           [0007]    More specifically, it is important to know if insulating material surrounding a conductive wire or cable has been pierced or broken. Such a failure could be a precursor to an electrical system failure in whatever system the wire or cable is installed. For example, failure in the solid wire insulation could cause an aircraft or other vehicle to lose control, which may result in an accident. It is therefore desirable to find damaged insulation before a failure occurs so that appropriate repairs can be made.  
           [0008]    Unfortunately, the defect and fault detection methods presently available are counterproductive to the defect detection process. For example, high voltage breakdown tests are commonly used to find defects in solid insulation, but the necessary applied voltage required to find these insulation defects is often several times higher than the voltage rating of the insulation. Thus, performing the high voltage breakdown test itself can actually destroy or weaken the insulation and wiring being analyzed, thereby creating defects in the solid insulation. What is needed is a method of locating defects without requiring the use of high voltage. Alternatively, a method is needed that substantially reduces the voltage required to detect and locate defects and electrical isolation faults in the electrical pathways.  
           [0009]    High voltage is commonly used to find defects in solid insulation, but it is impractical to find defects when a single conductor&#39;s insulation is damaged using this technique because an arc has to be detected between at least two conductors. As such the high voltage breakdown test is only useful if a conductor or charged electrode is in the vicinity of the insulation defect. Often this defect is imperceptible, making it very difficult to intentionally place a conductor near the defect. What is needed is a device that brings one or more added conductor(s) in proximity to insulation failures, thus making the defects detectable using standard techniques.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention provides a system and method of detecting and locating defects in solid insulation. The invention performs this detection by holding conductive surfaces against the conductors via a bladder or diaphragm. The present invention has been developed in response to the current state of the art, and in particular, in response to these and other problems and needs that have not been fully or completely solved by currently available sensor or electronic detection applications. The present invention reduces the voltage required to detect and locate an insulation defect when performing insulation tests. These qualities are primarily accomplished through conforming and pressing conductive surfaces against and around the conductors being tested via the injection of a gas into an inflatable bladder. The present invention may include at least one conductive surface or electrode for evaluating the connectors or electrical paths for defects in solid insulation of a cable or wire harness. The invention may also include a tester to find insulation defects, the tester being capable of performing any one of several standard tests between conductors. The present invention may also include one or more inflatable bladders that are used to hold the conductive surfaces against the conductor.  
           [0011]    One or more conductive surfaces or electrodes are electrically attached to, placed against, or made part of an inflatable bladder. The bladder is inflated after being brought near or against the conductor. In one embodiment, the conductor is placed near or against the bladder before inflation. In another embodiment, the conductor is placed near or against the bladder after full or partial inflation. In either embodiment, once inflated the bladder presses the electrodes against the conductor.  
           [0012]    These added electrodes are used in conjunction with the conductive material in the conductor to determine the presence of insulation failures by means of various insulation tests, such as resistance measurements, time-domain reflectometry, standing wave tests, or high-voltage breakdown tests. Specifically, if an added electrode makes physical contact with conductive material in the conductor through damage in the insulation, a resistance measurement, standing wave tests, or time-domain reflectometry can be used to identify and locate the fault. If an added electrode doesn&#39;t make physical contact to conductive material in the conductor through the damage in the insulation, a high-voltage breakdown test can still be used to cause an arc to occur between the added electrode and the exposed conductive material in the conductor.  
           [0013]    One or more added electrodes may locate the position of the insulation fault since the arc or short-circuit will occur between the conductor with damaged insulation and the nearest added electrode. The added electrode and bladder configuration may also be moved along the cable to test different sections of the conductor.  
           [0014]    The system and method of the present invention finds defects in solid insulation by using conductive surfaces or electrodes held against the conductor via an inflatable bladder configuration. The system and method may use one or more standard insulation tests including resistance measurements, time-domain reflectometry, standing wave tests, high-voltage breakdown tests, and the like. The system and method uses one or more conductors that are attached to, placed against, or made part of an inflatable bladder for the purpose of finding the location of insulation defects. The portable inflatable bladder may be attached to a rigid or semi-rigid containment structure that can be moved along the conductor to test different regions of the conductor at different times. The system and method of the invention finds defects in solid insulation by using conductive surfaces held against the conductor using a portable inflatable bladder that may be slid between a conductor and any adjacent physical structure such as a wall, pipe, or bulkhead. The system and method may also use multiple bladders to test multiple sections of a conductor.  
           [0015]    The inflatable bladder may also be used as part of a gas or liquid dispensing system for enhancing the effectiveness of the test. In this configuration, the gas or liquid is introduced into the test area via the bladder and is used to increase the sensitivity of the test to insulation defects. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    In order that the manner in which the above recited and other advantages and objects of the invention are obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. Understanding that these drawing depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
         [0017]    [0017]FIG. 1 illustrates one embodiment of an inflatable bladder in accordance with the present invention;  
         [0018]    [0018]FIG. 2 illustrates one embodiment of an inflatable bladder, similar to the one shown in FIG. 1, used with an insulation defect detection system in accordance with one embodiment of the present invention;  
         [0019]    [0019]FIG. 3 illustrates an alternative embodiment of an inflatable insulation detection system with a flexible bladder containment fixture; and  
         [0020]    [0020]FIG. 4 illustrates one embodiment of a portable inflatable insulation detection system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.  
         [0022]    Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of inflatable bladders, test gases, various gas delivery and containment systems, different electrode probes, insulation testers, types of insulation, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.  
         [0023]    Reference throughout this specification to “circuitry,” “cables,” or “wires” mean conductors with or without solid insulation. Conductors provide electrical paths for electrical power or signals. A conductor is often created out of conductive materials. Typically conductive materials are a class of material incapable of supporting electric stress, such that when a charge is given to a conductive material it spreads to all parts of the material. Exemplary conductive materials include aluminum, copper, platinum, gold, silver, chromium, tungsten, nickel, combinations thereof, and the like. Exemplary conductors or electrical paths that may be tested by the present invention include cables, connectors, wire harness, backplanes, printed circuit boards, circuitry, wires, or other similar electrical apparatus. While the figures only illustrate two conductors, one skilled in the relevant art will recognize that the system may also be practiced with multiple conductors.  
         [0024]    Additionally, reference throughout this specification to “gas” means a state of matter in which the molecules are practically unrestricted by cohesive forces. Ambient air is an exemplary gas. Depending on the embodiment, the gas may be selected to help obtain a desired electric effect. For example, some configurations attempt to confine electric behavior between the conductors and the system&#39;s conductive surfaces. These embodiments may employ gases with an electron affinity to limit or dampen electric activity within the inflatable bladder.  
         [0025]    Several other embodiments use a “test gas” in conjunction with the bladder to induce signs of insulation failure. In this context, the test gas is a gas that requires a lower voltage gradient for ionization than ambient air. These test gases do not have significant electron affinity and are referred to herein as electropositive. As such, the electropositive test gases exhibit an ionization point, breakdown, flashover, arcing, or corona discharge at a lower voltage gradient relative to ambient air. Exemplary test gases useful with the present invention include neon, helium, argon, xenon, krypton, radon, and combinations thereof. Helium, for example, has been shown to require a lower voltage gradient than air requires and is an excellent choice for the test gas. The noble test gases listed above have the added benefit that they are generally not chemically combining even during an arc. Other electropositive gases, which may or may not chemically combine with conductors and/or insulation may also be used.  
         [0026]    “Ionization” is the process by which neutral atoms or groups of atoms become electrically charged, either positively or negatively, by the loss or gain of electrons. An “ionized test gas” denotes the state of the test gas when atoms or groups of atoms within the test gas have become charged. The test gases may initially be introduced into the test area in a non-ionized state, but the test gas still requires a lower inducing voltage than ambient air for the occurrence of a noticeable voltage event, such as arcing or corona discharge.  
         [0027]    Reference is first made to FIG. 1 illustrating an inflatable bladder  10 . The bladder  10  includes a retentive film membrane  20 , a conductive surface  30  disposed on the film layer  20 , and a tubular inlet  40 . The retentive film membrane  20  includes overlapping body portions that define a cavity. In one embodiment, the membrane restricts the exodus of gas molecules from the cavity, causing the bladder  10  to inflate when gas is introduced into the cavity via the tubular inlet  40 .  
         [0028]    The membrane  20  may be constructed from a wide variety of materials and is preferably puncture resistant. The membrane  20  may also include multiple film layers bonded together. Exemplary membrane  20  materials used in creating the bladder  10  include a wide variety of balloon materials in commercial use today, such as nylon, latex, rubber, and plastics. Each of these balloon materials have many acceptable molecular configurations, such as polyethylene (for example, as producible from the resin “ELVAX 3120” marketed by DuPont E. I. De Nemours &amp; Co). While many of the membrane  20  materials used in the construction of the expandable bladder do not stretch, some configurations allow for stretching during the inflation process. The material being used in the membrane  20  characteristically determines the layer thickness. For example, polyethylene film membranes have a preferred thickness in the range of one (1.0) to three (3.0) mils. Furthermore, a membrane  20  may be created from multiple material layers bonded together increasing the overall thickness of the membrane on the bladder  10 .  
         [0029]    The conductive surface  30  is a conductor that can be charged with an inducing voltage so that a corona discharge or arc occurs between insulation defects and the conductive surface  30 . The conductive surface  30  is typically a deformable layer that can conform to the shape of a wire being tested. This ability helps ensure that physical contact will be made between the conductive surface  30  and any insulation defects on the wire in the test area. The conductive surface  30  is generally constructed from conductive materials, but may use numerous constructions or configurations. For example, the conductive surface  30  may be conductive mesh patches, metalized film layers, electrodes, bare wires, or the like. In one embodiment, the conductive surface  30  is integrated into the membrane  20 . Another embodiment places the conductive surface within the bladder  10 , using the membrane to insulate the conductive surface from unintended contact.  
         [0030]    Reference is next made to FIG. 2 illustrating an insulation detection and location system  100 . The system  100  is useful in testing the integrity of wires  110 ,  120 . More specifically, the system  100  tests solid insulation  130  around conductors  115 ,  125  by detecting and locating insulation defects, such as an exposed conductor  140 . The system  100  includes an inflatable bladder  150 , a gas source  160 , a conductive surface  170 , an insulation tester  180 , and a containment fixture  190 . The bladder  150  is connected via an inlet  155  to a feed tube  165  from the gas source  160 . Conductive surfaces  170 , such as copper mesh patches or electrodes, associated with the bladder  150  are electrically connected to the insulation tester  180  via at least one wire  185 . The system  100  also includes wires  190  that electrically connect the insulation tester  180  to the conductors  115 ,  125 . While FIG. 2 only illustrates two wires, one skilled in the relevant art will recognize, however, that the system may also be practiced with multiple wires.  
         [0031]    As previously mentioned, the wires  110  and  120  generally include at least one coating of solid insulation  130  to prevent arcing between neighboring conductors. Insulation  130  applied directly over conductors  115  and  125  is often called the primary insulation, since it determines most of the insulation properties of an individual wire. Sheath insulation, commonly called the jacket, brings several conductors together in a single cable configuration. The sheath insulation predominately offers mechanical protection. However, it does affect the electrical performance of the cable. Exemplary insulation materials used in data communication cables include FHF film (Teflon® FEP), Halar ECTFE, Compounded PVC, and other polymer resins. Other insulation systems for conductors include impregnated fiber products, laminated and molded products, polyester film, polyamide film, adhesive tapes, composite products, insulating paper, mica products, fiberglass sleeving, fiberglass tape, polyester non-woven fabrics, thermoplastic systems (asphalt-mica), thermosetting systems (polyester-mica or epoxymica), and other compounds know to one of skill in the art. Defects in these insulation systems are often difficult to see, which make them particularly dangerous. The present invention tests the insulation integrity without subjecting the insulation to damaging voltage levels. Furthermore the conductive surfaces of the bladder  150  can help pinpoint the location of unseen insulation defects.  
         [0032]    The system  100  of the present invention detects and locates defects  140  in solid insulation  130 . The system  100  performs this detection by holding conductive surfaces against or around the wires  110 , 120 . More specifically, the containment fixture  190  forces the bladder  150  or diaphragm to inflate around the surfaces of the wires  110 ,  120 . If restricted by the containment fixture  190 , the bladder  150  and the conductive surfaces associated with the bladder  150  conform and press against and around the wires  110 , 120  being tested once inflated via the injection of a gas from the gas source  160 .  
         [0033]    As previously mentioned, the bladder  150  may include at least one conductive surface or electrode for evaluating the wires  110 ,  120  for defects  140  in the solid insulation  130 . These conductive surfaces may be sensitive, flexible electrodes or copper mesh patches affixed to the surface of the bladder  150 . In one embodiment, the conductive surface includes a conductive mesh interwoven into the bladder. By disposing the conductive mesh over the entire exterior surface, the entire bladder  150  is conductive. The present invention may also include one or more inflatable bladders that are used to customize the insulation tests and more effectively hold the conductive surfaces against the conductor being tested.  
         [0034]    When the bladder  150  inflates, it conforms the conductive surfaces against the wires  110 ,  120  being tested, the insulation tester  180  is capable of performing any one of several standard insulation tests, such as resistance measurements, time-domain reflectometry, standing wave tests, or high-voltage breakdown tests. The insulation tester  180  performs the tests between conductors  115 ,  125  and the conductive surfaces  170  associated with the bladder  150  according to the type of contact achieved between the conductors  115 ,  125  and tester  180 . In one embodiment, if an added electrode  170  makes physical contact with conductive material in one of the conductors  115 ,  125  through a defect or damage  140  in the insulation  130 , a resistance measurement, standing wave test, or time-domain reflectometry can be used to identify and locate the fault.  
         [0035]    Resistance measurements are made between the conductors  115 ,  125  and copper mesh patches or electrodes  170  associated with the bladder  150 . If the measurements indicate that a short circuit has been detected, the failure is known to be in the region of the copper mesh patches  170  where it was detected. If the system  100  is using multiple electrodes  170 , the detection of the short circuit may also give away the location of the insulation failure. After the resistance measurement test is complete, a high-voltage may be applied between the copper mesh patch  170  and the conductors  115 ,  125 . If an arc occurs, the fault is known to be in the region of the copper mesh patch  170  where the arc occurred.  
         [0036]    If the electrodes  170  do not make physical contact with conductor  125  in the damaged wire  120 , a high-voltage breakdown test can be used to cause an arc to occur between the added electrode  170  and the exposed conductor  140  in the wire  120 . One or more added electrodes  170  associated with the bladder  150  may locate the position of the insulation fault since the arc or short-circuit will occur between the wire  120  with damaged insulation  140  and the nearest added electrode  170 . The added electrode  170  and bladder configuration may also be moved along the wires  110 ,  120  to test different sections of the conductor.  
         [0037]    In the case of the high voltage breakdown test, high voltage is applied between the conductors  110 ,  120  via wires  190  electrically attached to a high-voltage breakdown tester  180 . The high voltage breakdown tester  180  includes a high voltage supply and a current-sense module. The high-voltage breakdown tester  180  also tests the isolation of the electrical paths created by conductors  115 ,  125  for electrical signals. The tester  180  is used to determine the amount of electrical insulation between conductors  115  and  125 . The high voltage breakdown tester  180  performs a “hipot test” by applying a high voltage (AC or DC) potential between conductors  115  and  125  and sensing the current flow (AC or DC). The high voltage supply may provide between about 50 Volts and about 15,000 Volts. The amount of current sensed or the current change over time is used to determine the quality of insulation or isolation between conductors  115  and  125 . If multiple conductors are being tested for insulation/isolation, patterns may be used to apply the voltage between conductors such that all conductors to be tested for insulation/isolation defects have voltage applied between them at some time during the test.  
         [0038]    The effectiveness of the high voltage breakdown test can be dramatically improved by filling the bladder  150  with a test gas. The lower voltage gradient of the test gas when compared to ambient air helps the system to check the solid insulation around conductors at a lower voltage potential. The test gas is directed or confined within the bladder  150  such that it envelops the area to be tested. When high voltage is applied between conductors  110 ,  120  and the conductive surfaces are exposed and physically close, an arc occurs through the test gas and the insulation tester  180  records a current surge. Prior to arcing, the added test gas exhibits a very high electrical resistance. Once a sufficient voltage gradient is applied, the test gas “breaks down” or ionizes and has very low effective resistance. With the lower resistance it is easier for an electrical arc to form between the conductors  115 ,  125  and the conductive surface  170 . In an effort to promote this effect at a lower voltage, the voltage gradient for the breakdown of the test gas used in the present invention is substantially lower than for ambient air. Exemplary test gases useful with the present invention include neon, helium, argon, xenon, krypton, radon, and combinations thereof.  
         [0039]    In one embodiment the system  100  uses a conductive containment fixture  190  that conforms the inflatable bladder  150  as the bladder  150  fills with a test gas. In one configuration, the containment fixture  190  is a rigid component of the bladder  150 . Another configuration inserts a separate bladder  150  into the containment fixture  190  prior to inflation of the bladder  150 . The inducing test voltages are then applied between the conductors  115 ,  125  and the conductive containment fixture  190 . In this embodiment, it is important to use a test gas to lower the voltage levels required for testing, because the separation between the fixture  190  and the conductors  115 , 125  is greater than in the other described embodiments, which use a conductive surface  170 .  
         [0040]    Reference is next made to FIG. 3 illustrating a flexible test gas insulation detection and location system  200 . The system  200  tests the integrity of wires  210 ,  220 . More specifically, the system  200  tests solid insulation  230  around the conductors  215  and  225 , detecting and locating insulation defects, such as exposed conductor  240 .  
         [0041]    The system  200  includes a conductive inflatable bladder  250 , a test gas source  260 , a flexible containment fixture  270 , and an insulation tester  280 . Using an electropositive test gas in conjunction with the insulation tester  280  and the conductive bladder  250  allow the system  200  to perform high-voltage breakdown testing at considerably lower test voltages than ambient air. The test gas is delivered to the bladder  250  via an inlet  255  from a feed tube  265  from the test gas source  260 . Upon inflation of the conductive bladder  250 , the test gas begins to fill the spaces adjacent the wires  210 ,  220  via orifices  257 . Once the concentration of test gas in the test area is sufficient to lower the voltage gradient, the tester  280  may perform a high voltage breakdown test. The conductive bladder  250  is electrically connected to the insulation tester  280  via at least one wire  285 . The system  200  also includes wires  290  that electrically connect the insulation tester  280  to the conductors  210 ,  220 .  
         [0042]    The conductive inflatable bladder  250  may be made from various inflatable materials, such as plastic coated with a metalized copper, rip stop nylon, foam rubber, and the like. One embodiment uses a flexible stretching barrier to retain the test gas and apply pressure on the wires  210 ,  220 . Just as with the illustrated embodiment in FIG. 2, the system  200  may apply a variety of insulation tests to the conductors depending on the type of contact between the bladder  250  and the conductors  210 , and  220 . The insulation tests include resistance measurements, time-domain reflectometry, standing wave tests, high-voltage breakdown tests, and the like.  
         [0043]    The flexible containment fixture  270  provides the system  200  with useful mobility, while maintaining the primary fixture function of retaining the bladder  250 . The fixture  270  accomplishes this retention in a manner that compresses the bladder  250  against conductors  210  and  220 . The mobility allows the system  200  to be used along curvatures in the conductors without requiring the conductors to be straightened. The flexible containment fixture  270  is preferably constructed from an insulating material so that it does not electrically interfere with the bladder  250 .  
         [0044]    An additional advantage of the system  200  is the ability to synchronize the testing with the release of the test gas. In fact, the tester  280  may conduct a purity test between various electrodes in the bladder  250  that provide calibrated arc gaps to determine the concentration of the test gas in the test area.  
         [0045]    [0045]FIG. 4 illustrates a portable flat insulation detection and location system  300 . The system  300  can be used to wrap around the wires  310 ,  320  to test their electrical integrity. More specifically, the system  300  tests the solid insulation  330  around the conductors  315  and  325 , detecting and locating insulation defects, such as exposed conductor  340 . The system  300  includes a selectively defigurable inflatable bladder  350 , a compressed air source  360 , and an insulation tester  380 . The conductive surfaces may be embodied as conductive sheets  390 . The conductive sheets  390  are electrically connected to the insulation tester  380  via at least one wire  385 . The system  300  also includes wires  395  that electrically connect the insulation tester  380  to the conductors  310 ,  320 .  
         [0046]    Using the selectively defigurable portable bladder  350 , the illustrated embodiment may be wrapped around or placed behind the conductors  310 ,  320  prior to inflation. The compressed air or gas is delivered to the bladder  350  via an inlet  355  from a feed tube  365  from the gas source  360 . Upon inflation of the bladder  350 , the support and pressure from bladder  350  force the conductive sheets  390  to fill the open spaces adjacent to the wires  310 ,  320  and conform to the surface of the wires  310  and  320 . In one embodiment, the bladder  350  is wrapped around the wires  310 ,  320  prior to inflation. The bladder  350  is secured closed so that the subsequent inflation predominately forces the conductive sheets  390  to conform to the wires  310  and  320  on the interior of the system  300 . Another embodiment allows the bladder  350  to be slid between wires  310 ,  320  and any adjacent physical structure such as a wall, pipe, or bulkhead prior to inflation. In one embodiment, the bladder  350  is transparent thereby making visible any corona activity around the solid insulation  330 .  
         [0047]    After inflation, the tester  380  determines what type of contact is made between the exposed conductor  340  and the conductive sheets  390 . Specifically, if the conductive sheets  390  make physical contact with conductor  325  in the wire  320  through damage  340  in the insulation, a resistance measurement, standing wave tests, or time-domain reflectometry can be used to identify and locate the fault. If conductive sheets  390  do not make physical contact to conductor  325  in the wire  320  through the damage  340  in the insulation, a high-voltage breakdown test can still be used to create an arc between the added electrode  390  and the exposed conductor  340  in the wire  320 . One or more conductive sheets  390  may locate the position of the insulation fault since the arc or short-circuit will occur between the wire  320  with damaged insulation  340  and the nearest conductive sheet  390 . The selectively defigurable bladder configuration of system  300  may also be moved along the wire to test different sections of the wires  310 ,  320 .  
         [0048]    As with the other illustrated embodiments, the system  300  may also be used in hazardous fuel rich environments at a substantially reduced risk of harm. By reducing the voltage necessary to detect and locate insulation defects, the system  300  also reduces the likelihood of an errant spark igniting the fuel. Furthermore, in the wrap around configuration, system  300  contains the arcing within the folds of the inflatable bladder  350 .  
         [0049]    In summary, a system and method of the present invention finds defects in solid insulation by using conductive surfaces or electrodes held against a conductor via an inflatable bladder configuration. The system and method uses one or more standard insulation tests including resistance measurements, time-domain reflectometry, standing wave tests, high-voltage breakdown tests, and the like. In one embodiment, the system and method uses the inflatable bladder as part of a gas or liquid dispensing system where the gas or liquid is used to increase the sensitivity of the defect testing to insulation defects. The system and method uses one or more conductors that are attached to, placed against, or made part of an inflatable bladder for the purpose of finding the location of insulation defects. The system and method finds defects in solid insulation by using conductive surfaces held against a conductor using a portable inflatable bladder that may be attached to a rigid or semi-rigid structure that can be moved along the conductor to test different regions of the conductor at different times. The system and method finds defects in solid insulation by using conductive surfaces held against the conductor using a portable inflatable bladder that may be slid between a conductor and any adjacent physical structure such as a wall, pipe, or bulkhead. The invention may also use multiple bladders to test multiple sections of a conductor.  
         [0050]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.