Page 44 - Analysis Report of Global Market in the Submarine Cable Field (2017)

Wire and Cable

Key Technology of DC Submarine Cable for ±320 kV

and Below Power Transmission

YANG Fan,ZHOU Zewei,ZHANG Yue,YE Xinhong,ZHENG Lin
Ningbo Orient Wires & Cables Co., Ltd., Ningbo 315801, Zhejiang,China

Abstract: With the development of ocean oil and gas industry in China, the use of flexible HVDC Submarine Cable more and more, as China's
offshore wind, tidal power, offshore large semi-submersible platform transmission provides the best way to power transmission, etc.Thus, successfully
developed the ±320 kV and below power transmission with flexible dc cable.Of the flexible high-voltage direct current submerged two research and
development of key technologies are introduced in detail, namely, by analyzing in the operation and in fatigue test, optimization design is submarine
cable mechanical properties, and to ensure the mechanical life and safety reliability of submarine cable is excellent;By electrical conductivity, space
charge, dielectric performance testing and analysis of the distribution of submarine cable insulation production process optimization, in order to
effectively restrain the space charge in insulation, guarantee the submarine cable excellent electrical properties.Can be expected, this kind of product
will be more and more applied in deep sea power transmission, offshore wind power, dynamic transmission in the fields such as petroleum platform
Key words: submarine cable; high-voltage; flexible DC; space charge; mechanics

1. Introduction Tab 1 Design requirements of physical and mechanical properties of HVDC
With the development of ocean oil and gas industry in China, the use of submarine cable
flexible HVDC Submarine Cable is increasing. HVDC Submarine Cable
provides the best way to power transmission for China's offshore wind,
tidal power, offshore large semi-submersible platform transmission
etc. Thus, our company successfully developed the ±320 kV and
below flexible DC power transmission cable(hereinafter referred to as
flexible HVDC submarine cable) . In the development of this flexible
HVDC submarine cable, two key technologies are found: A. Through
the analysis of the operation and the test of fatigue, the mechanical
properties of sea cables is optimized, In order to guarantee the excellent
mechanical life and safety reliability. B. through electrical conductivity,
space charge distribution, dielectric performance testing and analysis,
the production process of cable insulation is optimized, In order to
effectively restrain the space charge in the insulation, and ensure the
excellent electrical performance of the cable. This paper will elaborate on
the development of the HVDC cable from the above two aspects [1].
critical. According to the composition of the internal structure of the
2.Structural Design [2] flexible HVDC submarine cable (section), the tensile stiffness of Kt is
As flexible HVDC submarine cable performance should meet the mainly composed of a cable core tensile stiffness of Kt,c, armored layer
requirements of the electrical, thermal, mechanical, optical, water (i.e. tensile reinforcing member) tensile stiffness of Kt,a, and sheath
resistance and environmental of whole cable system engineering, tensile stiffness of Kt,s that is:
its structure design added water resistance, corrosion resistance, K = K +K +K
compressive strength and counterweight compared to the land cable. As t t,c t,a t,s (1)
shown in Figure 1 the structure of the flexible HVDC submarine cable. The armor layer tensile stiffness Kt,a provides the main tensile stiffness
of cable.
Figure 1 The structure of flexible HVDC submarine cable In the design of flexible HVDC cable armoring layer tensile stiffness of
Kt,a, using the following formula

(2)
In formula (2): K ta unit is MN, m means spiral steel wire armor layers,
subscript i means a spiral steel wire armored layer, n i is the number of
layer i spiral steel wire armor, A i means layer i single spiral armoring wire
cross-sectional area, E i means layer i single spiral steel wire armor elastic
modulus. θ means the cable twist per unit length, R c is the center
radius of the cable, R i is the layer i spiral armoring wire circle radius, α i
is the layer i of armored helix angle, A c as the center cross-section of the
3. Optimum design of mechanical properties cable, E c is the center elastic modulus of the cable.
Mechanical performance design is the most critical in the flexible
HVDC submarine cable. The design requirements are shown in table 1. Usually double layer spiral winding steel wire armor distributed outside
the cable core in order to improve the tensile capacity of DC submarine
3.1 Tensile property design cable, the two armored layer shall meet the following requirements: a.
The flexible HVDC submarine cable easily under tensile load and occur DC submarine cable diameter and the linear density (mass per unit
large tension during operation, so the tensile performance design is length) requirements. b. Torsion balance requirement, that is, the
winding angle of two layers of armored steel wire should be reversed. c.
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