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Patexia Research
Patent No. US 11150291
Issue Date Oct 19, 2021
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Patent 11150291 - Functional reliability assessment for insulated power cable systems > Claims

  • 1. A method to test the functional reliability of a cable shield system for a high voltage cable circuit comprised of at least one segment along a cable route, the cable shield system including at least one segment of a conductive shield concentrically surrounding a phase of a corresponding segment of the high voltage cable circuit, the conductive shield extending along a circuit length and being physically connected to electrical ground potential during normal operation at least at one point along the circuit length, the conductive shield being connected at least at one ungrounded point via a connector link within a covered enclosure through a shield voltage limiter (SVL) to the electrical ground potential, the method comprising: electrically isolating a segment of the conductive shield from the electrical ground potential along the circuit length;supplying a test voltage of gradually increasing amplitude to the SVL;monitoring a voltage across the SVL and current through the SVL in response to the supplied test voltage; anddetermining the functional reliability of the cable shield system as a function of the monitored voltage across and current through the SVL.
    • 2. The method of claim 1, wherein the voltage across and current through the SVL are monitored by sensors in the covered enclosure.
    • 3. The method of claim 1, wherein the covered enclosure includes a heat sensor disposed to sense heat dissipated by the SVL; and wherein current flowing through the SVL is represented by detecting the dissipated heat.
    • 4. The method of claim 1, wherein the functional reliability of the cable shield system is determined at a location remote from the covered enclosure by transmitting to the remote location information representing the voltage across and current through the SVL.
      • 5. The method of claim 4, wherein the information representing the current through the SVL comprises heat information representing sensed heat dissipated by the SVL.
        • 17. The method of claim 5, wherein the functional reliability of the cable shield system is determined to be a functional condition when the heat information from the SVL at the voltage across the SVL is consistent with predetermined characteristics of the SVL.
      • 12. The method of claim 4, wherein wireless transmission is used to transmit voltage and current information to the remote location from the covered enclosure.
        • 13. The method of claim 12, wherein the wireless transmission comprises a low-power wide-area network (LP-WAN).
        • 15. The method of claim 12, further comprising storing, in a store disposed in or in the vicinity of the covered enclosure, information representing the voltage across the SVL and heat information representing the sensed heat dissipated by the SVL; and transmitting the stored voltage and heat information via the LP-WAN in response to a instructions received from the remote location.
      • 14. The method of claim 4, wherein a fiber optic cable is used to transmit voltage and current information to the remote location from the covered enclosure.
      • 16. The method of claim 4, wherein the functional reliability of the cable shield system is determined to be a functional condition when the current through the SVL at the voltage across the SVL is consistent with predetermined characteristic properties of the SVL.
    • 6. The method of claim 1, wherein the covered enclosure is a link box housing containing connector links for physically connecting the conductive shield of a respective phase of the high voltage cable circuit to the conductive shield of a different phase and to a respective SVL; and wherein the step of electrically isolating a segment of the conductive shield from the electrical ground potential comprises disconnecting the conductive shield from ground at all points of the segment of the cable shield section being tested.
      • 7. The method of claim 6, wherein the cable shield system includes a first link box in which the conductive shield of a first phase of the high voltage cable circuit is electrically connected to the conductive shield of a second phase of the high voltage cable circuit, and a second link box in which the conductive shield of the second phase of the high voltage cable circuit is electrically connected to the conductive shield of a third phase of the high voltage cable circuit and wherein a point of the conductive shield of the first phase of the high voltage cable circuit distant from the first link box is physically connected to the electrical ground potential during normal operation and a point of the conductive shield of the third phase of the high voltage cable circuit distant from the second link box is physically connected to the electrical ground potential during normal operation; and wherein the step of electrically isolating a segment of the conductive shield from the electrical ground potential comprises disconnecting the distant points of the conductive shield of the first and third phases of the high voltage cable from ground.
        • 8. The method of claim 7, wherein the step of supplying a test voltage to an end of the shield segment that has been isolated from the electrical ground potential comprises supplying a gradually increasing DC voltage to the end of the shield segment that has been isolated from the electrical ground potential.
        • 9. The method of claim 7, wherein the step of supplying a test voltage to an end of the shield segment that has been isolated from the electrical ground potential comprises supplying a gradually increasing AC voltage to the end of the shield segment that has been isolated from the electrical ground potential.
          • 10. The method of claim 9, wherein the current through the SVL exhibits a phase shift relative to the voltage across the SVL; and the step of monitoring the current through the SVL comprises monitoring the phase shift of the current relative to the voltage across the SVL.
            • 11. The method of claim 10, wherein the phase shift of the current through the SVL relative to the voltage across the SVL is related to the power factor exhibited by the SVL, and the monitored phase shift is indicative of the functional reliability of the SVL.
  • 18. An evaluating system to test the functional reliability of a cable shield system for a high voltage cable circuit comprised of at least one segment along a cable route, the cable shield system including at least one segment of a conductive shield concentrically surrounding a phase of a corresponding segment of the high voltage cable the conductive shield extending along a circuit length and being physically connected to electrical ground potential during normal operation at least at one point along the circuit length, the conductive shield being connected to a link box that includes a connector link to electrically connect the conductive shield of one phase of the high voltage cable circuit through a shield voltage limiter (SVL) to the electrical ground potential, the evaluating system comprising: a voltage source for providing, during a test, a test voltage of gradually or stepwise increasing amplitude;a connector for supplying the test voltage from the voltage source to an end of the at least one segment of the conductive shield distant from the link box and that has been isolated from the electrical ground potential, thereby supplying a voltage across the SVL;at least one sensor disposed within the link box for providing information representing the voltage across and current flowing in the SVL in response to the test voltage;a transmitter for transmitting sensor information to a location remote from the link box; anda processor supplied with sensor information from the link box acquired during the test for determining the functional reliability of the cable shield system as a function of the voltage and the current information.
    • 19. The evaluating system of claim 18, wherein current increases through the SVL disproportionally when the voltage across the SVL exceeds a conduction voltage threshold.
    • 20. The evaluating system of claim 18, wherein the at least one sensor includes a heat sensor disposed to sense heat dissipated by the SVL; and the current information is represented by the sensed heat.
      • 30. The evaluating system of claim 20, wherein the processor determines a nonconformance condition of the shield system when the sensed heat is more than a predetermined amount when the voltage across the SVL is less than a conduction voltage threshold.
    • 21. The evaluating system of claim 18, wherein the voltage source provides a gradually increasing DC voltage to an isolated shield segment.
    • 22. The evaluating system of claim 18 wherein the voltage source provides a gradually increasing AC voltage to an isolated shield segment.
      • 23. The evaluating system of claim 22, wherein the current through the SVL exhibits a phase shift relative to the voltage across the SVL; and the sensors include circuitry for sensing the phase shift of the current relative to the voltage across the SVL and as an indication of the functional reliability of the SVL.
    • 24. The evaluating system of claim 18, wherein the transmitter comprises a wireless transmitter.
      • 25. The evaluating system of claim 24, wherein the wireless transmitter comprises a low-power wide-area network (LP-WAN).
      • 27. The evaluating system of claim 24, further comprising a store disposed in or in the vicinity of the link box to store the sensor and voltage information, and wherein the transmitter wirelessly transmits the sensor and voltage information.
    • 26. The evaluating system of claim 18, wherein the transmitter comprises a fiber optic transmitter.
    • 28. The evaluating system of claim 18, wherein the processor determines a functional condition of the shield system when the sensor information at the voltage across the SVL is consistent with predetermined characteristic properties of the SVL.
    • 29. The evaluating system of claim 18, wherein the processor determines a nonfunctional condition of the shield system when the sensor information is less than a predetermined amount when the voltage across the SVL exceeds a conduction voltage threshold.
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