Apparatus, method and system for spark testing an insulated cable

Apparatus, methods, and systems improve spark testing of insulated cables. According to embodiments described herein, a spark tester includes a conductive housing having an entryway, an exit, and a test chamber therebetween. The spark tester utilizes spring electrodes connected to an adjustment ring at one end of the housing and to a fixed structure at the opposite end of the housing. The adjustment ring is rotated such that the spring electrodes wrap around the test cable, contacting the test cable on all sides throughout the test chamber. The housing also includes an electrical contact for receiving and distributing a voltage across the housing and the spring electrodes. As the test cable is drawn through the spring electrodes, the grounded conductors within the test cable are monitored for a voltage spike, indicating an insulation defect that allowed a discharge from the spring electrodes to a test cable conductor.

BACKGROUND

Transmission cables used to transport electricity or communication signals are made up of one or more conductors surrounded by insulation material. Any imperfections in the insulation may lead to short circuiting and premature failure of the cable. For this reason, cables are typically subjected to spark testing as part of the manufacturing process. A popular method of spark testing includes introducing the insulated cable to a high voltage field while the one or more conductors inside the insulation remain grounded. Any imperfections in the insulation should result in a spark created between a conductor within the cable and the closest electrode that is providing the voltage. Common spark testing equipment includes bead testers. A bead tester includes a box having a large number of bead chains, or bead electrodes, hanging from the top of the box. The cable undergoing the spark testing will be pulled through the chains hanging from the top of the box. Voltage is then applied to the bead electrodes in an attempt to induce a spark when an imperfection in the insulation is located.

When the cable is physically contacting the source of the voltage, the bead electrodes, the conductor within the cable is as close as possible to the electrodes, assuring the highest percentage of success in locating imperfections. An electrode contacting the surface of the cable is more likely to induce a short circuit to the conductor through an imperfection in the intervening insulation than would an electrode that is an inch away from the cable, since the path from the electrode to the conductor is shorter when the electrode is contacting the cable. By utilizing a large number of bead chains within the box, there is a relatively high likelihood that the top and sides of the cable will come into contact with one or more bead electrodes containing the test voltage.

However, because gravity forces the bead chains to hang vertically straight down, the underside of the cable will never be in contact with the bead electrodes. Although, in many cases, the voltage from the bead electrodes closest to the underside of the cable is strong enough to induce a short circuit to the cable conductor when an imperfection on the underside of the cable is present. However, because the underside of the cable does not contact the bead electrodes, it is likely that some imperfections on the underside of the cable will be missed.

SUMMARY

It should be appreciated that this Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended for use in limiting the scope of the claimed subject matter.

Apparatus, methods, and systems provide for improved spark testing of insulated cables. According to embodiments described herein, a spark tester apparatus includes a conductive housing having an entryway and an exit. A cable being tested is able to pass through the housing via the entryway and exit. Either the entryway or exit includes an adjustment ring that can be rotated around the test cable passing through the housing. At least one elastic electrode is attached at one end to the adjustment ring and at the other end to the housing adjacent to the entryway or exit. The housing also includes an electrical contact for receiving and distributing a voltage across the housing and the elastic electrode.

According to further embodiments, insulation of a test cable is tested by inserting the test cable through an entryway of a conductive housing of a spark tester and out through an exit. An adjustment ring within the entryway is rotated around the cable. In doing so, a number of elastic electrodes that are each attached at one end to the adjustment ring and at the opposite end to the housing next to the exit are wrapped around the test cable. Wrapping the test cable with the elastic electrodes creates a test section within the housing where the entire circumference of the test cable touches the elastic electrodes. The test cable is drawn through the spark tester while a voltage is applied to the elastic electrodes. The grounded conductor within the test cable is monitored for any changes in voltage. If a voltage change is detected, then the portion of the insulation within the test section is determined to be defective. However, if a voltage change is not detected, then the portion of the insulation within the test section is determined to be not defective.

According to other embodiments, a spark tester system includes a test chamber with a rotatable adjustment ring. The adjustment ring is positioned within the test chamber to allow a test cable to enter the chamber at one end, pass through the adjustment ring, and exit the chamber at an opposite end. At least one elastic electrode is connected at a first end to the rotatable adjustment ring and at an opposite end to a fixed element of the spark tester. In doing so, when the adjustment ring is rotated with the test cable in place, the elastic electrode wraps around the test cable so that it touches the insulation of the cable for a defined length within the test chamber. The spark tester system includes instruments that control an amount of voltage supplied to the electrode from a power source and to detect an amount of voltage received by a grounded conductor within the test cable.

Other apparatus and systems according to embodiments will be or will become apparent to one with skill in the art upon review of the following drawings and Detailed Description. It is intended that all such additional apparatus and/or systems be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.

DETAILED DESCRIPTION

The following detailed description is directed to apparatus, methods, and systems for testing the integrity of cable insulation. As discussed briefly above, typical spark testers rely on bead chain electrodes, which do not provide a uniform electrical field around the entire circumference of the cable being tested. Rather, the bottom or underside of the cable is subjected to less voltage than the top and sides of the cable since the insulation on the underside of the cable does not come into direct contact with the bead electrodes. Additionally, because adding, removing, and/or repositioning the bead chains in a typical bead chain spark tester is a process that is time consuming and cumbersome, the typical bead chain spark tester is not easily adjustable as to the amount of cable surface area contacted by the electrodes within the spark tester.

However, embodiments of the disclosure provided below describe a spark tester apparatus and system that provide electrodes that fully encompass the cable being tested. In doing so, the surface area of the cable in contact with the electrodes is maximized around the entire circumference of the cable for the desired amount of time within a test chamber. According to various embodiments, a spark tester utilizes spring electrodes that are connected to opposite ends of a spark tester housing and spaced evenly around a central axis through which the cable being tested will be drawn. Once the cable is pulled in place through the spark tester housing, an adjustment ring attached to one end of the spring electrodes is rotated such that the springs wrap around the cable, contacting the cable on all sides throughout the test chamber.

The embodiments described below provide a spark tester that is easily adjusted, operated, and maintained. Because a limited number of spring electrodes are used to provide a maximum amount of electrode contact, maintaining the spark tester is a simple matter of replacing a spring electrode as it gets stretched out or worn. Moreover, as will become clear from the disclosure below, the amount of surface area around the entire circumference of the cable that contacts one or more spring electrodes, as well as the length of contact within the test chamber, is easily adjustable by modifying the number of spring electrodes used within the spark tester and varying the amount of rotation of the adjustable ring. The various embodiments described herein may be utilized to test the insulation of power transmission cables, such as triplexed cable having three conductors, or other cables having fewer conductors, such as telecommunications cables.

In the following detailed description, references are made to the accompanying drawings that form a part hereof, and which are shown by way of illustration, specific embodiments, or examples. Referring now to the drawings, in which like numerals represent like elements through the several figures, aspects of a spark tester apparatus, method, and system will be described.FIG. 1shows a spark tester apparatus100according to embodiments described herein. The spark tester apparatus100includes a housing102and a number of spring electrodes106. The housing102may have two sides, a bottom, and two ends. The top of the housing is left open so that the test chamber within the housing may be viewed. This is advantageous when setting up the spark tester apparatus100so that the technician can easily see the spring electrodes106when wrapping them around the test cable, as well as for removing and replacing spring electrodes106. However, it should be appreciated that the housing102may have any number of sides and be configured according to any desired shape.

The housing102should have an aperture104in opposing ends to allow for the passage of the test cable through the spark tester apparatus100. The spring electrodes106are each attached at one end to an adjustment ring108, and at an opposing end to the housing102or other fixed structure at a position proximate to the aperture104. According to the embodiment shown inFIG. 1, when the spring electrodes106are in a setup configuration, they each extend from one end of the housing102to the other end of the housing102parallel to one another and evenly spaced around a central axis extending through the center of the apertures104. The test cable will be drawn through the spark tester apparatus100along this central axis during testing. According to one embodiment, the spring electrodes106are attached at each end using eye bolts110; however, any other suitable methods of attaching the end of a spring to a structure may also be used.

Throughout this disclosure, the spring electrodes106will be described as being steel springs. However, it should be appreciated that the spring electrodes106may be any elastic conductive material that is capable of receiving a voltage and transferring that voltage to a conductor within the test cable. Springs are used due to their ability to stretch to allow for wrapping around the test cable and to return to their approximate original length when unwrapped from the cable. Any material with similar properties, with or without coils, may be used within the scope of this disclosure. According to one embodiment, the spring electrodes106are continuous extension springs manufactured from spring-tempered steel, having 0.054-inch wire size, 0.5-inch outside diameter, with 18.52 coils per inch. The springs are cut to 18-inch relaxed lengths and the ends bent into loops for attachment to the eye bolts110.

The embodiment shown inFIG. 1shows six spring electrodes106used within the housing102. The spring electrodes106are spaced out evenly around the central axis of the housing102to ensure continuous coverage around the circumference of the test cable. Although six spring electrodes106are shown, any number of spring electrodes106may be used. The number used may depend upon the diameter of the adjustment ring108to which the spring electrodes106are attached. For example, the greater the diameter of the adjustment ring108, the greater the number of spring electrodes106that may be required to achieve the same density of electrode contact points on the surface of the test cable given the same rotation of the adjustment ring108as that achieved with a smaller diameter adjustment ring108.

The diameter of the adjustment ring108may depend on the maximum cable diameter to be tested within the spark tester apparatus100. According to one embodiment, the adjustment ring108has a diameter of five inches and six spring electrodes106are used. The adjustment ring108is a conductive ring that is rotatably secured within the aperture104. The adjustment ring108may frictionally engage the housing102, or may rotate with the assistance of bearings. The adjustment ring108may be positioned within the aperture104on the end of the housing102in which the test cable enters the spark tester apparatus100, or within the aperture104on the end of the housing102in which the test cable exits the spark tester apparatus100. According to various embodiments, the adjustment ring108may include markings109, numbers, text, or other indications of rotational displacement to allow a technician to properly position the adjustment ring108repeatedly with a high degree of accuracy. A pin or any other means for locking the adjustment ring108into position may be employed to ensure that the adjustment ring108remains in the proper position throughout a test session.

The housing102further includes an electrical contact112for receiving power from a power source and distributing the power through the conductive housing102to the spring electrodes106. According to one embodiment, the electrical contact112may simply be a conductive fastener with corresponding aperture in the housing102for securing an electrical cable114to the housing102. The electrical contact112and corresponding electrical cable114may be positioned at any location on the housing102.

It should be noted that the disclosure provided herein is not limited to the configuration shown inFIG. 1. For example, according to another embodiment, the housing102has open ends and the adjustment ring108is attached to the bottom and/or one or more sides of the housing102. In this embodiment, a fixed ring or other fixed structure must be secured to the bottom and/or sides of the housing102at the opposite end to provide a fixed anchor location for the opposing ends of the spring electrodes106. According to a further embodiment, the spark tester apparatus100does not include a housing102. Rather, the adjustment ring108and a corresponding fixed ring are mounted directly in a safety compartment302(shown inFIG. 3), without requiring a separate housing102.

Turning now toFIG. 2, the spark tester apparatus100as configured for testing a cable according to various embodiments presented herein will be described.FIG. 2shows a test cable202traversing the spark tester apparatus100and test chamber defined by the walls of the housing102. In this configuration, the adjustment ring108has been rotated to wrap the spring electrodes106around the test cable202. As can be seen, the spring electrodes106wrap around the test cable202creating a test section204in which the entire circumference of the test cable202is contacting the spring electrodes106. It should be appreciated that the adjustment ring108may be rotated in either direction such that the helical twist of the spring electrodes106extend from left to right in a clockwise or a counter-clockwise direction around the test cable202. According to one embodiment, the adjustment ring108is rotated in a direction such that the helical twist of the spring electrodes106is in the same direction as the lay of the test cable202.

As the test cable202is drawn through the spark tester apparatus100, the test cable202is subjected to a consistent, uniform voltage along the entire surface of the test cable202, rather than just along the top and sides of the cable as is often the circumstance when using typical bead chain spark testers. As mentioned above, the spark tester apparatus100also provides greater adjustability than typical bead chain spark testers. Looking atFIG. 2, the test section204may be shortened or lengthened according to the line speed at which the test cable202is drawn through the spark tester apparatus100by altering the rotational displacement of the adjustment ring108. To lengthen the test section204, the adjustment ring108should be further rotated to provide more turns of the spring electrodes106around the test cable202. Similarly, to shorten the test section204, the rotational displacement of the adjustment ring108should be decreased to reduce the number of turns of the spring electrodes106around the test cable202.

The adjustment ring108should be displaced an amount that allows for the desired length of the test section204without creating so many turns of the spring electrodes106around the test cable202that friction between the spring electrodes106and the test cable202will damage the spring electrodes106or the test cable202. To further adjust the spark tester apparatus100, spring electrodes106may be added or removed. A proper configuration of the spark tester apparatus100may be obtained for any given test cable202diameter and line speed that satisfies industry cable engineers association (ICEA) or other industry specifications through trial and error without undue experimentation. As an illustrative example, according to one embodiment, six continuous extension 18-inch relaxed length spring-tempered steel springs, each having 0.054-inch wire size, 0.5-inch outside diameter, and 18.52 coils per inch are utilized as the spring electrodes106. For plexed electrical test cables202up to one inch in diameter, a 300-degree adjustment ring108rotation provides at least six inches of test section204for a maximum line speed of 200 feet per minute. For test cables202of over one inch in diameter, a 240-degree adjustment ring108rotation provides similar results.

FIG. 3illustrates a spark tester system300according to various embodiments described herein. The spark tester system300includes the spark tester apparatus100installed within a safety compartment302. The safety compartment302includes a testing compartment302A and a lid302B. When installing the test cable202and configuring the spark tester apparatus100for testing, the lid302B is raised. However, because the housing102of the spark tester apparatus100is conductive and is subjected to high voltages during testing, for safety purposes, the lid302B is closed to cover the spark tester apparatus100when testing commences. The electrical cable114supplies power from a power source to the housing102via the instruments306. The instruments may include any type and quantity of instruments necessary or desired to conduct spark-testing procedures. At a minimum, the instruments306should be capable of controlling the amount of voltage supplied to the spring electrodes106from the power source and to detect an amount of voltage received by one or more grounded conductors within the test cable202. The spark tester system300includes a base304that is sized to position the spark tester system300at the appropriate height and/or position within the manufacturing line in which the test cable202is being tested.

According to one embodiment, the spark tester apparatus100of the spark tester system300is interchangeable with an existing bead chain spark tester. To remove the spark tester apparatus100, a technician must simply remove the electrical cable114from the electrical contact112, unbolt or otherwise remove applicable fasteners securing the spark tester apparatus100to the testing compartment302A, and remove the spark tester apparatus100. A reverse procedure may be used to add a bead chain spark tester to the testing compartment302A. By designing the spark tester apparatus100to be interchangeable with a bead chain spark tester, existing equipment in manufacturing facility may be replaced in an economical way, prioritizing the manufacturing lines that would most benefit from the improved spark testing provided by the embodiments described herein. It should also be appreciated that due to the lack of reliance on gravity, the embodiments provided herein may be configured horizontally, vertically, or at any angle between. This improvement over existing spark testers allows the spark tester apparatus100to be placed in unconventional locations in a manufacturing facility.

Turning now toFIG. 4, an illustrative routine400will be described for testing the integrity of insulation surrounding a grounded conductor of the test cable202according to various embodiments presented herein. The routine400will be described with respect to the spark tester system300shown inFIG. 3. The routine400begins at operation402, where the test cable202is inserted through the aperture104in one end of the housing102of the spark tester apparatus100and out of the aperture104in the opposite end of the housing102. From operation402, the routine400continues to operation404, where the spring electrode parameters are determined. The spring electrode parameters include any configuration parameters corresponding to the spark tester apparatus100according to the test being performed. For example, given the diameter of the test cable202and the line speed, the technician or computing device determines the number of spring electrodes106to use and the corresponding rotational displacement to impose on the adjustment ring108.

The routine400continues from operation404to operation406, where the spark tester apparatus100is configured according to the determined parameters. The type and quantity of springs are added to the spark tester apparatus100and the adjustment ring108is rotated to the desired position, which wraps the spring electrodes106around the test cable202. The lid302B is closed and the spark tester system300is ready to operate. From operation406, the routine400continues to operation408, where the test cable202is drawn through the housing102and corresponding test chamber. The routine continues from operation408to operation410, where the appropriate voltage is applied to the spring electrodes106using the instruments306. From operation410, the routine400continues to operation412, where a determination is made as to whether a voltage change in the conductors within the test cable202has been detected.

If a voltage change has not been detected, then the routine400proceeds from operation412to operation416and continues as described below. However, if a voltage change has been detected at operation412, the routine400continues to operation414, where the section of the test cable202that is within the test chamber is marked as defective. This defective section may then later be inspected and repaired. From operation414, the routine400continues to operation416, where a determination is made as to whether the testing is complete. If the testing is complete, as indicated by the entire length of test cable202being drawn through the spark tester apparatus100or by a line stoppage, then the routine400ends. However, if the testing continues, then the routine400returns to operation412and continues as described above.