DL/T 5490-2025 in English
VALIDDesign Code for Submarine Power Cable Lines
- Issued on:2025-09-28
- Implemented on:2026-03-28
- File Format:PDF
- Delivery:Via email within 5 business days
$422.00
| Standard No: | DL/T 5490-2025 |
| Document status: | VALID |
| Title in English: | Design Code for Submarine Power Cable Lines |
| Title in Chinese: | 海底电力电缆线路设计规程 |
| Language: | English |
| File Format: | Electronic (PDF) |
| Delivery: | Via email within 5 business days |
| Issued on: | 2025-09-28 |
| Implemented on: | 2026-03-28 |
| ICS Classification: | 29.240.20-Power transmission and distribution lines |
| Chinese Classification: | P62-Power transmission and transformation engineering |
| Professional Classification: | DL-Electricity |
| Related Keywords: | submarine cable design
submarine cable design technology submarine cable lines submarine power cable lines introduction background international submarine cable line design experience |
Introduction
Background and Technological Evolution of the DL/T5490-20xx Standard Revision
The DL/T5490-20xx standard, a key industry standard replacing the 2014 version, marks a new stage in the development of submarine cable design technology in my country. This revision is based on the National Energy Administration's 2022 energy sector industry standard formulation and revision plan. The drafting group conducted thorough research on domestic and international submarine cable line design experience and completed the technological upgrade based on extensive consultation.
The core driving force behind the standard revision stems from the rapid development of new energy projects such as offshore wind power and cross-sea power grid interconnection. With the popularization of emerging application scenarios such as offshore wind power transmission and high-voltage direct current transmission, the original standard can no longer meet the needs of engineering practice. The new standard expands its scope of application from a single 500kV AC to 110kV-330kV high-voltage AC and high-voltage direct current submarine cables, reflecting the forward-looking nature of technological development.
Comparison of Standard Scope and Technical Framework
| Technical Dimensions | DL/T5490-2014 | DL/T5490-20xx | Key Points of Technical Upgrades |
|---|---|---|---|
| Voltage Levels | 500kV AC | 110-500kV AC/DC | Covering all voltage levels, adding DC systems |
| Cable Types | Cross-linked polyethylene, oil-filled paper insulation | Adding selection principles for extruded insulation | Improving technical specifications for insulation materials |
| Application Scenarios | Traditional Cross-Sea Interconnection | Diverse Scenarios such as Offshore Wind Power Transmission | Adapting to the Development Needs of New Energy |
| Protection System | Basic Protection Requirements | Integrating Grounding, Overvoltage Protection, and Other Systems | Improving System Reliability |
Key Technical Requirements for Submarine Cable Route Selection
Route selection is the primary step in submarine cable design, directly affecting project feasibility, investment rationality, and operational reliability. Clause 3.1 of the standard clarifies the multi-dimensional considerations for route selection:
Natural Environmental Factors: Marine hydrology, meteorological conditions, seabed topography, and geological stability should be comprehensively considered. Priority should be given to sea areas with stable seabeds and slow currents, avoiding natural obstacles such as reefs.
Social Activity Factors: Cables must avoid military facilities and dumping grounds, and should preferably avoid nature reserves and tourist areas. Protective measures should be taken when intersecting with waterways and other pipelines; the horizontal distance in sea areas should not be less than 50m, and not less than 15m when restricted.
Engineering and Technical Factors: The spacing between parallel cables should not be less than 1.2 times the maximum water depth; this can be appropriately reduced for landing sections. Landing points should be selected in areas with stable coastlines that are not easily eroded, avoiding areas with bedrock, steep cliffs, or other hazardous geological features.
Cable Type and Structure Design Specifications
Evolution of Insulation Material Technology
Standard 4.2 clearly stipulates the requirements for cable insulation: AC submarine cables should preferably use cross-linked polyethylene insulation, or self-contained oil-filled paper insulation; DC submarine cables should use DC-specific cross-linked polyethylene insulation, and the use of ordinary cross-linked polyethylene insulation is strictly prohibited.
This regulation is based on the technical characteristics of space charge accumulation under a DC electric field. In DC applications, ordinary cross-linked polyethylene is prone to generating stray charges due to the influence of cross-linking residues, and at high temperatures, it easily forms local high field strength, leading to a reduction in insulation breakdown strength. DC-specific cross-linked polyethylene technology has been successfully applied in domestic projects such as the ±400kV Rudong offshore wind power project.
Conductor Selection and Current Carrying Capacity Calculation
| Insulation Type | Continuous Operating Temperature (°C) | Short-Circuit Transient Temperature (°C) | Applicable Scenarios |
|---|---|---|---|
| Cross-linked Polyethylene (AC) | 90 | 250 | Mainstream AC Applications |
| Cross-linked Polyethylene (DC) | 70/90 | 180/250 | High Voltage DC Transmission |
| Self-contained Oil-filled (Mineral Oil) | 85 | 160 | Traditional High-Capacity Engineering |
| Adhesive Impregnated Paper Insulation | 60 | 175 | Specific DC Applications |
Submarine cables should preferably use copper conductors, and extruded insulated cables must adopt a water-blocking structure. Current-carrying capacity calculations must be performed in accordance with JB/T10181, taking into account the environmental conditions of the route area, soil characteristics, and protection methods. For DC cables, the effect of insulation temperature difference must also be considered.
Innovation in Laying Technology and Protection Measures
Selection of Laying Process
Standard Clause 7.1 specifies three main laying methods: **direct laying**, **laying and burying simultaneously**, and **laying first and then burying**. The selection criteria include cable characteristics, routing conditions, and construction requirements:
Laying and burying simultaneously** is suitable for short distances and favorable geological conditions, allowing for simultaneous laying and burying.
Laying first and then burying** is suitable for complex geological conditions and long-distance routes, avoiding the impact of variable marine weather on construction safety.
The calculation of laying length must consider routing conditions and laying errors. Additional length control standards are: 30-50m within 1km, 20-50m within 1-3km, and controlled at 5-10% of the route length when exceeding 3km.
Protection Measures System
Standard Clause 8.0 establishes a multi-layered protection system:
Buried Protection: The preferred method, with burial depth determined based on risk level and geological conditions.
Covering Protection: Methods such as riprap and interlocking concrete slabs are used, suitable for hard seabed areas.
Casing Protection: Materials such as steel pipes and concrete pipes are used, and mechanical strength needs to be checked.
The selection of protection measures should be based on the risk assessment results, comprehensively considering factors such as natural disasters and human activities to ensure the safe operation of cables.
Overvoltage Protection and Grounding System Design
Chapter 6 of the standard sets forth strict requirements for overvoltage protection and grounding: Surge arresters must be installed at the connection points between submarine cables and overhead lines; the power frequency induced voltage of the metal sheath of AC submarine cables should not exceed 300V on land and at landing, and should not exceed 1000V in the sea area.
Grounding system design should pay attention to the following: For single-core submarine cables, grounding wires should be led out from both ends of the metal sheath and armor layer, and the three phases should be directly grounded after interconnection; the grounding electrode must have corrosion resistance and meet the dynamic and thermal stability requirements of induced current and short-circuit current.
Standard Implementation Recommendations and Engineering Applications
Key Focus Areas in the Design Phase
In the feasibility study phase, a full tabletop route demonstration should be conducted, basic data such as marine planning and environmentally sensitive areas should be collected, and multiple feasible route schemes should be preliminarily determined.
The preliminary design phase requires a detailed route survey to obtain topographic, hydrological, and geological survey reports that meet national standards. The mapping scale should preferably be 1:5000 or 1:2000.
The construction drawing design phase should refine the cable laying and protection measures design, with a mapping scale of 1:1000 or 1:500 to ensure construction accuracy.
Technological Innovation Direction
As offshore wind power develops towards deeper waters, the standard encourages the use of advanced technologies such as J-type protective pipes and dynamic positioning laying vessels. Regarding cable materials, new materials such as polypropylene insulation have begun engineering trials and are expected to further improve cable performance in the future.
Operation and Maintenance Management Requirements
The standard emphasizes the full life-cycle management of submarine cables, requiring the establishment of protected areas, route markings, warning systems, and the provision of comprehensive monitoring facilities.
Spare parts management should consider system requirements, operating conditions, and failure rates to ensure emergency repair capabilities.
Environmental Protection and Occupational Health and Safety
Chapter 11 of the standard clearly defines environmental protection requirements: engineering design should comply with national environmental protection regulations, and priority should be given to engineering materials with minimal impact on the marine environment; necessary measures should be taken to prevent electromagnetic interference and reduce its impact on the surrounding environment.
Regarding occupational health and safety, measures such as fire prevention, explosion prevention, and drowning prevention are required. Lifesaving facilities must be provided for offshore operations, and underwater workers should be protected from hazards such as currents and low temperatures, complying with the safety requirements of GB26123.
The implementation of DL/T5490-20xx will significantly improve the design level of submarine cable lines in my country, provide technical support for the development of offshore new energy sources and cross-sea power grid interconnection, and promote the standardization and normalization of marine power transmission technology.
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