Pressurization and heating device and method for insulation system restoration of a power cable
A pressurisation and heating device for restoring an insulation system of a power cable, the pressurisation and heating device including: a first part including a first channel configured to receive a portion of the power cable, a second part including a second channel configured to receive a portion of the power cable, wherein the pressurisation and heating device is configured to be set in a closed state in which the first channel faces the second channel thereby forming a heating chamber extending from a first end to a second end, opposite the first end, of the pressurisation and heating device, wherein the pressurisation and heating device is configured to be pressurised to obtain a pressure higher than atmospheric pressure inside the heating chamber when the power cable is arranged sealed in the heating chamber, wherein the pressurisation and heating device has an at least 20 cm long axially extending section which is primarily made of material at most having a conductivity of the order of 1000 S/m at 20° C.
1. A pressurisation and heating device for restoring an insulation system of a power cable, the pressurisation and heating device comprising:
a first part including a first channel configured to receive a portion of the power cable,
a second part including a second channel configured to receive a portion of the power cable,
wherein the pressurisation and heating device is configured to be set in a closed state in which the first channel faces the second channel thereby forming a heating chamber extending from a first end to a second end, opposite the first end, of the pressurisation and heating device,
wherein the pressurisation and heating device is configured to be pressurised via a gas flowed into the heating chamber, to obtain a pressure higher than atmospheric pressure inside the heating chamber when the power cable is arranged sealed in the heating chamber,
wherein the pressurisation and heating device has an at least 20 cm long axially extending section which is primarily made of material at most having a conductivity of the order of 1000 S/m at 20° C., wherein the axially extending section is at least a portion of the pressurisation and heating device.
2. The pressurisation and heating device as claimed in claim 1 , wherein the material at most has a conductivity of the order of 100 S/m at 20° C.
3. The pressurisation and heating device as claimed in claim 2 , wherein the material comprises fibre reinforced polymer.
4. The pressurisation and heating device as claimed in claim 2 , comprising a high frequency, HF, heating coil extending around the heating chamber in the axially extending section when the pressurisation and heating device is in the closed state.
5. The pressurisation and heating device as claimed in claim 2 , wherein the material at most has a conductivity of the order of 10 S/m at 20° C.
6. The pressurisation and heating device as claimed in claim 2 , wherein the material at most has a conductivity of the order of 0.0001 S/m at 20° C.
7. The pressurisation and heating device as claimed in claim 1 , wherein the axially extending section is at least 30 cm long.
8. The pressurisation and heating device as claimed in claim 7 , wherein the axially extending section is at least 40 cm long.
9. The pressurisation and heating device as claimed in claim 1 , wherein at least 70% of the axially extending section is made of material at most having a conductivity of the order of 1000 S/m at 20° C.
10. The pressurisation and heating device as claimed in claim 9 , wherein as at least 80% of the axially extending section is made of material at most having a conductivity of the order of 1000 S/m at 20° C.
11. The pressurisation and heating device as claimed in claim 1 , wherein the material comprises fibre reinforced polymer.
12. The pressurisation and heating device as claimed in claim 1 , comprising a high frequency, HF, heating coil extending around the heating chamber in the axially extending section when the pressurisation and heating device is in the closed state.
13. The pressurisation and heating device as claimed in claim 12 , wherein the HF heating coil extends around the heating chamber at a location which is in a range of ±30% from a centre of the pressurisation and heating device measured from the first end towards the second end.
14. The pressurisation and heating device as claimed in claim 13 , wherein the range is ±10%.
15. A heating assembly comprising the pressurisation and heating device as claimed in claim 1 , and at least one external HF heating coil configured to be arranged around the pressurisation and heating device in the axially extending section.
16. A method of restoring an insulation system around a conductor of a power cable, using the pressurisation and heating device as claimed in claim 1 , the method comprising:
a) placing the power cable having a restoration insulation system layer arranged around a conductor in one of the first channel and the second channel,
b) setting the pressurisation and heating device in the closed state,
c) pressurising the heating chamber, and
d) heating the restoration insulation system layer while the heating chamber is pressurised, by outer heating inside the pressurisation and heating device and by inner heating of the restoration insulation system layer by feeding a high frequency, HF, heating coil arranged around the heating chamber in the axially extending section with current to induce a current in the conductor.
17. The method as claimed in claim 16 , comprising performing steps a)-d) for each of a plurality of restoration insulation system layers.
18. The method as claimed in claim 16 , wherein in step d) the outer heating and the inner heating are performed simultaneously.
19. The method as claimed in claim 16 , wherein the outer heating and inner heating is performed in a noble gas atmosphere inside the heating chamber.
20. The method as claimed in claim 16 , wherein prior to step d) the restoration insulation system layer is an uncured insulation system layer, and wherein in step d) the outer heating and the inner heating is for curing the restoration insulation system layer.