420 kV HVAC Cable System Qualification
Nexans qualified and delivered the first 420 kV subsea XLPE AC cable system back in 2007, and Nexans has since then delivered several 420 kV subsea cable systems, including what is currently the longest 420 kV subsea link of 32 km. The demand for transmission capacity is increasing, and to address this trend Nexans has executed an internal R&D program to further extend the transmission capacity of our 420 kV XLPE AC cable systems up to typically 1 GW for a single core link and typically 700MW for a three-core link. The extensive program involved type testing and pre-qualification testing.
The full system qualification test was successfully passed. Test specifications were according to the Cigré recommendation 490, the Cigré recommendation 623, and the IEC 62067 standard. For the subsea cable and accessories, the test water depth was set to 300 meters. The complete qualification included several loops of type test setups and several loops of prequalification test setups.
The Scandinavian Association for Testing of Electric Power Equipment (SATS) was the 3rd party inspector for all these tests and issued the test certificates accordingly.
A summary of the qualified Nexans products, tested as a part of this qualification project, is listed below.
- Single-core 420 kV cable.
- Three core 420 kV cable, up to 60 tons tensile force.
- Factory joint 420 kV, including the transition of different conductor cross-sections, and transition between different conductor materials.
- 420 kV offshore field and repair joints for single-core and three-core cable. Including transition between different conductor cross-sections, and transition between different conductor materials. For use in inline and hairpin installation.
- 420 kV subsea to land cable transition joint (cross-bonding joint) with different conductor cross-sections and transition between different conductor materials.
- 420 kV outdoor composite termination qualified for both silicone oil and SF6 gas insulation medium.
- 420 kV dry type GIS termination, including epoxy bushing (female) and electrical termination (male).
- All conductor connections for the accessories are made with a mechanical connector that does not require any special tools to install.
Nexans produces all the cable and accessories in-house to ensure total control of the product design, quality, and development, which has resulted in this successful qualification testing of a new 420 kV XLPE AC system. This system qualification will also qualify systems at lover voltage levels, such as 245 kV, 300 kV, and 362 kV.
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