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EP-4741843-A1 - INTEGRATED SPACE CHARGE MONITORING FOR HIGH VOLTAGE CABLES

EP4741843A1EP 4741843 A1EP4741843 A1EP 4741843A1EP-4741843-A1

Abstract

There is provided apparatus for enabling space charge distribution measurement of a high voltage cable (110). The apparatus comprises: a compartment (140; 240; 340; 440) for holding a pulsed electro-acoustic, PEA, sensor (260; 360) in contact with the high voltage cable; and a coupling structure (130; 230; 330; 424; 529) configured to couple the compartment to the high voltage cable between a base of a termination device (120; 420) of the high voltage cable and a ground screen (150; 450) of the high voltage cable.

Inventors

  • Doedens, Espen
  • SINGH, BIRENDER
  • FRISK, Nils-Bertil

Assignees

  • Nexans

Dates

Publication Date
20260513
Application Date
20251030

Claims (15)

  1. Apparatus for enabling space charge distribution measurement of a high voltage cable (110), the apparatus comprising: a compartment (140; 240; 340; 440) for holding a pulsed electro-acoustic, PEA, sensor (260; 360) in contact with the high voltage cable; and a coupling structure (130; 230; 330; 424; 529) configured to couple the compartment to the high voltage cable between a base of a termination device (120; 420) of the high voltage cable and a ground screen (150; 450) of the high voltage cable.
  2. The apparatus of claim 1, wherein the coupling structure comprises a cable gland (130; 230; 330).
  3. The apparatus of claim 1, wherein the coupling structure comprises a base plate (424) of the termination device.
  4. The apparatus of claim 1, wherein the coupling structure comprises a cable clamp or a cable covering (529).
  5. The apparatus of any preceding claim, wherein an interior (241; 341) of the compartment is accessible from an exterior of the compartment without removal of the coupling structure from the high voltage cable.
  6. The apparatus of claim 5, wherein the compartment has an opening (349) through which the PEA sensor is received, in use, and a closure (342) for closing the opening, wherein the closure is configured to connect to or form part of the PEA sensor (360).
  7. The apparatus of any preceding claim, wherein the compartment comprises a spring (244) for holding the PEA sensor in contact with the high voltage cable.
  8. The apparatus of any preceding claim, wherein the compartment comprises at least one cable bushing (247, 248; 347, 348) that extends through a wall of the compartment.
  9. The apparatus of any preceding claim, comprising a holder (550) for holding a thermal sensor (251), wherein the coupling structure is further configured to couple the holder to the high voltage cable between the base of the termination device and the ground screen.
  10. A system comprising the apparatus of any preceding claim and a PEA sensor housed within the compartment of the apparatus.
  11. The system of claim 10, further comprising a thermal sensor for measuring a temperature of the high voltage cable between the base of the termination device and the ground screen.
  12. The system of claim 10 or claim 11, further comprising one or more electrodes for delivering an electrical pulse to the high voltage cable.
  13. An assembly comprising a high-voltage cable, a termination device through which the high voltage cable passes, a ground screen connected to the high voltage cable, and the apparatus of any of claims 1 to 9, wherein the apparatus is coupled to the high voltage cable so that the compartment is between a base of the termination device and the ground screen.
  14. A method for enabling space charge distribution measurement of a high voltage cable, the method comprising: providing the apparatus of any of claims 1 to 9; mounting the apparatus to the high voltage cable between a base of a termination device of the high voltage cable and a ground screen of the high voltage cable; and, while the apparatus is mounted to the high voltage cable: accessing an interior of the compartment; placing the PEA sensor in the compartment in contact with the high voltage cable; and sealing the compartment.
  15. A method of maintaining the system of any of claims 10 to 12, the method comprising: accessing an interior of the compartment of the system; removing the PEA sensor from the interior of the compartment; placing the PEA sensor or a further PEA sensor in the interior of the compartment in contact with the high voltage cable; and sealing the compartment.

Description

FIELD OF THE INVENTION Aspects relate to systems and methods for apparatus, systems and methods for enabling space charge distribution measurement of a high voltage cable, and to methods of maintaining systems for space charge distribution measurement of a high voltage cable. BACKGROUND High voltage cables, particularly high voltage direct current, HVDC, cables are used in electrical power distribution or transmission systems. Such power cables generally comprise a central part or core made of conductive material, layers of insulating material and protective layers including a metallic water barrier. Some of the layers of insulating may comprise materials whose function is to control the electrical field around the central part of the cable. Some electrically insulating materials used in these layers, such as the dielectric insulation, can exhibit conductivity gradients and charge carrier traps which give rise to a space charge and a non-uniform distribution of the electrical field. Non-uniform distribution of the electrical field can cause high concentrations of the electrical field in parts of the cable. Such high concentrations may cause the electrical insulation of the cable to age prematurely and ultimately break down. The measurement of the spatial location of these charges makes it possible to determine the charge accumulation mechanisms and avoid such a rupturing of insulation. It is also an indicator of the state of health of the cable. There are acoustic techniques for measuring spatial distribution of space charges, in which an acoustic pulse is excited and is propagated in a sample being studied. One of these acoustic techniques is known as the pulsed electro-acoustic, or PEA, technique. In the PEA technique, a PEA sensor, which incorporates an acoustic transducer, such as a piezoelectric transducer or a pressure transducer or pressure sensor, is provided in contact with a semiconductive or dielectric material. The PEA sensor measures oscillations or vibrations resulting from excitation of the space charges in the material when an electrical field pulse is applied. Traditionally, the PEA technique was applied in a dedicated "measurement cell" and samples of material were tested. Recently, it is becoming common to perform the PEA method on operational high voltage cables. In such methods, a short portion of the cable is selected along its length and sensing apparatus is applied. The protective, outer layers of the cable have poor acoustic properties that prevent the PEA method being accurately performed, so to apply the sensing apparatus, the outer semiconductive layer are first accessed through the protective layers by stripping back the cable. Stripping back the cable requires significant modification to the cable, and for relatively large sensing apparatus to be attached to the cable. Moreover, the cable then has to be re-sealed with the apparatus attached, so as to prevent water ingress. Other difficulties may be encountered, such as chemical residue outgassing, which may hamper efforts to obtain good quality measurements. Altogether, this results in an arduous and cumbersome process, as well as one that may potentially result in water ingress or poor measurements. SUMMARY OF THE INVENTION The present invention is defined by the appended claims and in the following: According to a first aspect, there is provided an apparatus for enabling space charge distribution measurement of a high voltage cable. The apparatus comprises: a compartment for holding a pulsed electro-acoustic, PEA, sensor in contact with the high voltage cable; and a coupling structure configured to couple the compartment to the high voltage cable between a base of a termination device of the high voltage cable and a ground screen of the high voltage cable. The apparatus provides a way of mounting a PEA sensor to a high voltage cable to enable accessible and convenient space charge distribution measurement. The part of the cable between the base of the termination device and the ground screen is a part that lacks protective layers, as this would ordinarily be protected and covered by other components, such as cable glands. Providing apparatus to connect a PEA sensor to this part of the cable therefore enables an efficient way of integrating space charge distribution measurement. Furthermore, the termination and ground screen are conveniently located, meaning that the apparatus will be accessible for installation of the PEA sensor and maintenance, and for connection of equipment for monitoring and providing pulses. This is especially useful for undersea cables, where locations other than the termination may be difficult to access. Additionally, other solutions, which integrate PEA sensors elsewhere may require dedicated sensing equipment, which may be difficult to locate. The compartment may be sealed against the cable or may be sealable against the cable. The compartment may be sealed against the cable, at least in part, by th