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Adapting Cable Accessories for Onshore & Offshore Substations

June 10, 2017 • ARTICLE ARCHIVE, Cable Accessories, Substation
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Offshore Certification & Installation

In the case of offshore substations, environmental conditions as well as special applications during project handling have to be considered. Apart from saltwater conditions and high UV radiation, there is limited space available. The entire substation has to be installed and fully tested onshore and later is transferred offshore where the sea cable part is finally connected. A full product family of pluggable systems on medium and high voltage level is mandatory.

Fig. 12: High & medium voltage connection on transformer on offshore substation Alpha Ventus. cable accessories Adapting Cable Accessories for Onshore & Offshore Substations Screen Shot 2016 07 15 at 14

Fig. 12: High & medium voltage connection on transformer on offshore substation Alpha Ventus.
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Pluggable cable accessories offer a fully encapsulated solution for offshore substations. The outer part has to be touch proof and at ground potential. All metal as well as heat shrink parts have to withstand harsh salt fog conditions (DIN 81243) and high UV radiation. An offshore certification for encapsulated pluggable systems requires not only the design and classification of materials but also includes salt fog tests and ageing tests under UV radiation.

Pluggable cable accessories require less space and also offer the possibility of separating parts of the system from transformers to gas insulated switchgear to cable system. Installation and testing of these items can be done individually and connection of the sea cable can finally be accomplished with minimum effort, leading to a fully tested substation.

Fig. 13: Testing of offshore substation Borkum 2. cable accessories Adapting Cable Accessories for Onshore & Offshore Substations Screen Shot 2016 07 15 at 14

Fig. 13: Testing of offshore substation Borkum 2.
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Dry HV Cable Accessories for Ultra-Bendable EPR Cable

Ultra-Bendable HV cables

Ultra-bendable high voltage cables are suitable especially for offshore applications, where high flexibility, very small bending radii and mobile or fixed installation are all required. Moreover, due to their features as discussed above, this cable type can be used for onshore substations as well as other applications where available space is limited.

Adaptation of Dry Type Cable Accessories for Ultra-Bendable HV Cables

In order to guarantee proper jointing and termination of ultra-bendable HV cables, it was necessary to develop a new type of mechanical torque connector, specially suited for highly flexible copper conductors. The behaviour and design of this product have been successfully verified with a test based on IEC 61238-1 (second edition, 2003-05) for 800 mm2 conductor cross-section (Fig. 14).

Fig. 14: Set-up for conductor connector electrical tests based on IEC 61238-1  cable accessories Adapting Cable Accessories for Onshore & Offshore Substations Screen Shot 2016 07 15 at 14

Fig. 14: Set-up for conductor connector electrical tests based on IEC 61238-1.
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Fig. 15: Type test set-up for Um=170 kV and 800 mm2 copper conductor according to IEC 60840. cable accessories Adapting Cable Accessories for Onshore & Offshore Substations Screen Shot 2016 07 15 at 14

Fig. 15: Type test set-up for Um=170 kV and 800 mm2 copper conductor according to IEC 60840.
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In addition, the performance of HV cable joints, outdoor terminations and dry type pluggable connectors installed on ultra-bendable HV cable has been verified through design and type tests according to IEC 60840 for Um=170 kV and conductor cross-section up to 800 mm2.

Special Applications of Dry Type Cable Accessories for Ultra-Bendable HV Cables

Ultra-bendable high voltage cables and dry type pluggable terminations combine the advantages of compact and flexible design and are therefore also suitable for:

• Temporary installation on construction sites;
• Back-up solution;
• Connection between test equipment and test objects (e.g. during commissioning).

An example of exploiting these benefits are cable links equipped with dry type pluggable connectors or outdoor terminations, allowing transport on a drum mounted on a trailer (see Fig. 16).

Fig. 15: Type test set-up for Um=170 kV and 800 mm2 copper conductor according to IEC 60840. cable accessories Adapting Cable Accessories for Onshore & Offshore Substations Screen Shot 2016 07 15 at 14

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