Design and Manufacturing of ±200kV HVDC in Zhoushan Flexible DC Transmission Project

A Talk On Jicable 15 To Be Presented By: Ming Hu, Zhongtian Technology Submarine Cable Co., Ltd, Nantong(China), email:[email protected] ,Tel: +860513-83599667

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ BACKGROUND

Zhoushan multi-terminal flexible DC transmission project in Zhejiang province is China first five-terminal DC transmission project

103km ±200kV submarine fiber optic composite power cable linking Dinghai and Daishan

Transmitting capacity of 400MVA with conductor cross section of 1000mm2.

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Zhoushan flexible DC transmission project

Zhoushan flexible DC transmission  China highest voltage and project project longest HVDC Dinghai-Daishan Daishan-Qushan  Chinese first flexible DC transmission project using the HVDC-YJQ41- HVDC-YJQ41- systems all made in China 200kV 200kV Cable type  Five terminal HVDC system 1×1000+2× 1×300+2× 10B1+2×2B4 10B1+2×2B4

insulation XLPE XLPE 泗礁 洋山 thickness 16.0mm 17.5mm 衢山

Transmitting 400MVA 100MVA 岱山

length 103km 34.2km 舟山

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France 200kV submarine power cable main parameter

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Insulation thickness design of HVDC submarine cable

Electrical stress distribution

rated load 1000A

Soil thermal resistivity 1.5K·m/W， When rated current is1000A，max temperature 35, buried depth in electric filed in conductor shied is ground 700mm. Max temperature of 13.9kV/mm，min electrical filed in conductor is 70 insulation shied is 11.3V/mm.

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Insulation thickness design of HVDC submarine cable

Electrical stress distribution

the current is 0A and max electric field in conductor shield is 15.4kV/mm, min electric field in insulation shield is 10.3kV/mm. At full load and no load, insulation thickness of 200kV cable with 1000mm2 is 16.0mm. electric field in insulation is less than permitted value 20kV/mm. Safety margin of insulation meet the requirement.

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Production process

DC submarine power cable is composed of insulated cores, fiber optic unit and outer protective layer The flow chart is shown as below:

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Factory joint

Factory splice is mainly applied in the long submarine power cable exceeding the maximum continuous manufacturing length for the connection of pieces of insulated cores before armoring is applied. A transition joint has been made for connecting land cable. The mechanical and electrical performance of factory splice shall be identical to or close to that of the original cable.

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Routine voltage test

The DC submarine cable length (factory splice included) from Dinghai- Daishan island in Zhoushan is 51km, voltage test for which shall use negative

DC voltage of 370kV (1.85U0) applied between the conductor and metallic screen for 60min and no break down in insulation shall occur.

The power cable is equivalent to a big that will be injected with substantial electric charges during the DC voltage test process and after the voltage test the charges shall be released through discharge treatment

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Mechanical test

CIGRE TB 496 type test process, coiling test and tensile bending test are carried out to verify the stability of fiber optic unit and if it can withstand the great mechanical force.

Coiling test Bending tensile test

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France prequalification test the submarine cable with factory splice shall undergo the all performance type test according to CIGRE 496 and the prequalification test shall also be carried out in the Zhoushan marine transmission research center. Currently, the prequalification test has already been performed for eight months.

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Conclusion

ZTT uses the method of FEA to simulate and analyze the electric stress of DC cable for Zhoushan multi-terminal flexible DC transmission project. In the case of both empty and full load, the electric stress at any point of the insulation is lower than the permissible operation stress of insulation material and large insulation safety margin is considered. ±200kV XLPE insulated DC submarine fiber optic composite power cable and DC land power cables designed and produced by ZTT have passed all performance test and are under prequalification test. Zhoushan multi-terminal HVDC transmission demonstration project has started successfully, which indicates that the domestic developed DC cable system has been officially put into operation and will face the test of the long-term operation.

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France Thanks You!

www.zttcable.com [email protected]

• Jicable’15, 21 ‐ 25 June 2015 ‐ Versailles ‐ France