35 kV LSZH Power Cables for Subway and Urban Rail Transit

Urban rail transit systems depend on a stable and carefully protected electrical infrastructure. Subways, light-rail lines, commuter railways, underground stations, tunnels, depots, and trackside substations all require power cables that can transmit energy reliably while also meeting strict fire-safety and environmental requirements. In these applications, cable performance cannot be judged only by current-carrying capacity. The cable must also limit smoke, reduce toxic or corrosive emissions, resist flame propagation, withstand mechanical and environmental stresses, and remain protected against biological damage caused by termites and rodents.

The 35 kV power cable for subway and urban rail transit is designed for precisely these demanding conditions. It combines medium-voltage electrical performance with low-smoke, halogen-free or low-halogen, flame-retardant, termite-resistant, and rodent-resistant characteristics. Its structure is intended to provide dependable service in enclosed underground spaces and other rail transit environments where evacuation, maintenance access, ventilation, and cable replacement may be difficult.

With rated voltage options of 21/35 kV and 26/35 kV, conductor sizes up to 630 square millimeters, a maximum continuous conductor operating temperature of 90 degrees Celsius, and a short-circuit temperature of up to 250 degrees Celsius, this product family can support a broad range of urban rail power distribution systems. It is manufactured according to GB/T 12706.3-2020 and related enterprise requirements, providing a controlled technical basis for production, inspection, and application.

The product is manufactured by Wuxi Guanghuan Cable Co., Ltd., a Chinese cable producer with extensive experience in power cables, electrical equipment wires and cables, bare conductors, railway cables, renewable-energy cables, and other specialized products. The manufacturer’s production scale, testing capability, technical personnel, certification systems, and quality-control procedures support the consistent manufacture of medium-voltage cables for infrastructure projects.

Power Cable for Subway and Urban Rail Transit (Rated Voltage 35kV)

1. The Role of Medium-Voltage Cables in Urban Rail Systems

Urban railways require several levels of electrical distribution. Traction systems may use dedicated power arrangements, while stations, signaling installations, ventilation equipment, lighting, communication systems, pumps, escalators, lifts, fire-protection equipment, and depot facilities require reliable auxiliary power. A medium-voltage network is often used to transfer electrical energy between substations and distribution points over practical distances while controlling transmission losses.

A cable installed in such a network must operate continuously under changing load conditions. It may be routed through cable trenches, tunnels, service corridors, shafts, stations, outdoor sections, bridges, substations, or areas close to vegetation and soil. These environments expose the cable to heat, moisture, dust, vibration, electromagnetic influences, installation stress, and possible contact with pests.

Underground rail systems create additional safety concerns. A cable fault can occur in an area with limited ventilation and restricted access. If an ordinary polymeric cable burns, dense smoke and corrosive halogen-containing gases may obstruct visibility, impair evacuation, damage electronic equipment, and complicate firefighting. For this reason, cable selection for metro and light-rail systems must consider fire behavior and smoke generation as seriously as electrical ratings.

The 35 kV subway and urban rail cable addresses these requirements through a coordinated design. The conductor and insulation system provide medium-voltage transmission performance, while the sheath and material formulation contribute to fire safety, environmental protection, and resistance to external biological attack.

2. Product Overview

This cable is a medium-voltage power cable developed for subways, light rail, urban commuter railways, and related transportation infrastructure. It is available in single-core and three-core configurations, with conductor cross-sections extending up to 630 square millimeters or below, depending on the selected construction and project requirements.

The main product characteristics include the following:

Rated voltage options of 21/35 kV and 26/35 kV.

XLPE insulation for stable electrical performance and high operating temperature capability.

Polyolefin-based sheathing options for low-smoke and halogen-free performance.

Low-halogen, low-smoke construction where the project specification permits or requires that alternative.

Flame-retardant performance, including ZA, ZB, or ZC grades when requested.

Protection against termite and rodent damage through specialized sheath and formulation design.

Maximum continuous conductor operating temperature of 90 degrees Celsius.

Maximum conductor temperature of 250 degrees Celsius during a short circuit, subject to the applicable short-circuit duration and system design.

Insulation verification through 3.5 U0 alternating-current and direct-current voltage resistance tests.

Installation temperature guidance and controlled minimum bending radii for armored and unarmored cables.

The cable can therefore be selected for projects where electrical capacity, fire safety, biological resistance, and installation reliability must be considered together rather than separately.

3. Product Construction

3.1 Conductor

The conductor is designed to provide the required current-carrying capacity and direct-current resistance in accordance with the applicable standard. Copper conductor versions are identified in the supplied product models. Depending on the specification, the conductor may be manufactured as a compacted or stranded conductor to achieve the required electrical, mechanical, and installation characteristics.

Conductor quality has a direct effect on cable losses, voltage drop, heat generation, and long-term operating efficiency. Consistent stranding and dimensional control are therefore important during production. The conductor must be free from significant surface defects that could affect the insulation interface or create local electrical stress concentrations.

3.2 XLPE Insulation

Cross-linked polyethylene insulation is used because it offers a favorable combination of dielectric strength, thermal capability, moisture resistance, and mechanical stability. The rated continuous conductor temperature of 90 degrees Celsius allows the cable to support substantial loading while maintaining an appropriate operating margin.

XLPE insulation must be applied with close control of thickness, concentricity, cleanliness, and surface quality. In medium-voltage cables, small contaminants, voids, protrusions, or irregularities can increase electrical stress and contribute to partial discharge or premature insulation deterioration. For this reason, modern production lines use controlled extrusion, online dimensional monitoring, and carefully managed material handling.

3.3 Metallic Components and Optional Armoring

Depending on the application, the cable may be supplied as armored or unarmored. Armoring can improve mechanical protection where the cable may be exposed to impact, compression, pulling forces, or other external hazards. The selection should be based on the cable route, installation method, grounding arrangement, electromagnetic requirements, and project standards.

Metallic screens or other conductive layers may be incorporated as required by the medium-voltage design. These components help control the electric field, provide a path for fault current, and support safe connection to the grounding system. Correct installation of screens, joints, terminations, and bonding connections is essential for the cable to perform as designed.

3.4 Outer Sheath

The outer sheath is one of the most important features of this product family. A polyolefin sheath can provide low-smoke, halogen-free, and reduced-toxicity performance under fire conditions. It also protects the underlying cable components from moisture, abrasion, environmental stress, and installation-related damage.

The sheath formulation is additionally adapted for resistance to termites and rodents. Biological damage can expose insulation, reduce mechanical protection, and eventually create a serious electrical fault. In rail infrastructure, where cable routes may pass through soil, vegetation zones, service ducts, tunnels, or poorly accessible areas, this protection can reduce the risk of unplanned outages and costly replacement work.

4. Electrical Performance

4.1 Rated Voltage

The product is available with rated voltage designations of 21/35 kV and 26/35 kV. The designation U0/U represents the rated voltage between the conductor and earth and the rated voltage between conductors, respectively. The correct voltage class must be selected according to the network configuration, grounding method, fault-clearing time, and applicable project specification.

Before procurement, the user should verify the system’s nominal voltage, highest system voltage, earthing arrangement, expected fault duration, and requirements for single-core or three-core operation. These factors influence insulation coordination, screen design, accessory selection, and installation practices.

4.2 Conductor Temperature

The permissible maximum continuous conductor temperature is 90 degrees Celsius. This rating supports a practical balance between current capacity, insulation life, and thermal stability. Actual ampacity depends on conductor size, installation arrangement, ambient temperature, thermal resistivity of surrounding materials, grouping, ventilation, burial depth, and the presence of other heat sources.

For rail projects, cable load calculations should account for the real installation environment rather than relying only on catalog values. Cables installed in a confined tunnel, grouped in a service channel, or surrounded by low-thermal-conductivity materials may have a lower permissible current than cables installed in open air.

4.3 Short-Circuit Capability

During a short circuit, the conductor may reach a maximum temperature of approximately 250 degrees Celsius for the specified short-circuit duration. The supplied technical material refers to a maximum duration of five seconds in the product overview and also contains a separate reference to five minutes in a detailed description. Because short-circuit withstand time is a critical design parameter, the final project documentation, test certificate, and applicable standard should be used to confirm the exact duration for the selected cable construction.

Short-circuit performance depends on conductor size, conductor material, initial operating temperature, fault duration, screen and metallic component design, and the effectiveness of the protection system. Protective relays and circuit breakers should be coordinated so that the actual clearing time remains within the cable’s verified thermal withstand capability.

4.4 Insulation Testing

The cable is required to pass 3.5 U0 alternating-current and direct-current voltage resistance tests. These tests provide evidence that the insulation system can withstand an elevated electrical stress beyond normal operating voltage. Routine and type testing should be conducted with suitable equipment, calibrated instruments, controlled procedures, and documented results.

For medium-voltage cables, electrical testing should be complemented by checks for conductor resistance, insulation dimensions, screen continuity, sheath integrity, partial discharge where applicable, and visual quality. Testing at the factory does not eliminate the need for careful site inspection and commissioning tests after installation.

5. Low-Smoke and Halogen-Free Safety

Fire safety is a defining advantage of this cable over conventional cables that use materials capable of producing dense smoke and corrosive halogen gases. In a subway environment, smoke can travel rapidly through tunnels, platforms, stairways, ventilation paths, and station corridors. Reduced smoke improves visibility and can support evacuation and firefighting operations.

For the halogen-free cable, light transmittance during combustion is specified as not less than 60 percent. This indicates that smoke density is controlled to preserve a higher degree of visibility than would normally be expected from many conventional cable materials. The total acid gas emission is specified as no higher than 5 milligrams per gram of material burned.

The pH value of gases produced during combustion is not less than 4.3, and the conductivity is not more than 10 microsiemens per millimeter. These indicators are important because corrosive gases can damage metal structures, control panels, signaling equipment, communication devices, and electronic components even after the fire has been extinguished.

The product range also includes a low-halogen, low-smoke option. The supplied data identifies a light transmittance requirement of not less than 30 percent for the low-halogen cable and distinguishes its acid-gas behavior from the halogen-free product. Project engineers should therefore select the construction according to the fire-safety classification stated in the tender documents and local regulations.

Flame-retardant grades ZA, ZB, and ZC may be supplied according to request. These grades should be specified clearly at the procurement stage because the required flame-retardant performance can influence the material system, test program, cable identification, and acceptance documentation.

6. Resistance to Termites and Rodents

Termite and rodent damage is a significant but sometimes underestimated cause of cable failure. Termites may attack or penetrate certain sheath materials, particularly when cables are installed near soil, vegetation, or construction zones. Rodents may gnaw cable sheaths and insulation in tunnels, substations, equipment rooms, depots, and maintenance areas.

Damage may begin as a small defect but develop into moisture penetration, screen corrosion, insulation deterioration, tracking, or an earth fault. In a rail system, the resulting interruption can affect train operation, passenger services, signaling, station facilities, and emergency systems.

The specialized outer sheath and additive system used for this cable are intended to create a physical and chemical barrier against biological attack. The design aims to make the cable less attractive or less vulnerable to termites and rodents while maintaining the flexibility and electrical properties required for installation.

This feature provides an advantage over standard medium-voltage cables that may offer suitable electrical performance but lack specialized biological protection. It can be particularly valuable in tropical, subtropical, humid, agricultural, forest-adjacent, and underground environments. Nevertheless, cable protection should be combined with sound route design, sealing of ducts, pest control, inspection, and maintenance.

7. Installation Requirements

7.1 Installation Temperature

The general installation guidance specifies that the ambient temperature should not be lower than 0 degrees Celsius. If installation is performed below this temperature, preheating may be required to prevent excessive stiffness, sheath cracking, or damage during bending and pulling.

The supplied product information also states that when the cable is laid at an ambient temperature of 0 degrees Celsius, there is no need for preheating or a fall limitation. The installer should follow the final approved installation manual for the specific cable construction, because permissible handling conditions may vary according to sheath formulation, cable diameter, storage history, and local weather conditions.

7.2 Minimum Bending Radius

Respecting the minimum bending radius is essential. Excessive bending can deform the insulation screen, damage the sheath, increase mechanical stress, or cause a permanent change in cable geometry. The minimum radius is expressed as a multiple of the cable’s outside diameter, represented by D.

Application condition	Single-core unarmored	Single-core armored	Three-core unarmored	Three-core armored
Minimum bending radius during installation	20D	15D	15D	12D
Minimum bending radius near connection box or terminal	15D	12D	12D	12D

Near a connection box or terminal, bending should be carefully controlled. Formed guide plates, suitable rollers, and temporary supports can help maintain the required radius. The cable should not be forced into a sharp turn simply because the available termination space is limited.

7.3 Cable Pulling

During pulling, the installation team should control pulling tension, sidewall pressure, pulling speed, roller spacing, and cable twisting. The pulling equipment must be suitable for the cable mass and route length. Excessive tension can stretch or deform the cable, while poor roller placement can create localized pressure and damage the sheath.

For single-core cables, the installation arrangement should also consider induced currents, magnetic effects, cleat spacing, phase arrangement, and the bonding method of metallic screens. These factors can influence heating and ampacity. The cable manufacturer’s installation recommendations and the project’s electrical design should be followed together.

7.4 Terminations and Joints

Medium-voltage terminations and joints should be installed by trained personnel using approved accessory systems. The insulation screen must be removed to the specified dimensions, the semiconductive layers must be handled carefully, and the stress-control components must be positioned accurately.

Contamination, moisture, sharp tool marks, incorrect screen-cutting dimensions, insufficient crimping, or poor sealing can cause premature failure. In underground stations and tunnels, joint locations should be selected to allow inspection, drainage control, and safe maintenance access.

8. Model Options

Two representative product codes are identified in the supplied technical information. The first is (FZ-FSY)-WD-TYJY, described as a copper-conductor, XLPE-insulated, polyolefin-sheathed, non-halogen, low-smoke power cable for subway and light-weight track, with ultraviolet protection and termite and rodent resistance.

The second is (FZ-FSY)-DD-TYJV, described as a copper-conductor, XLPE-insulated, polyolefin-sheathed, low-halogen, low-smoke power cable for subway and light-weight track, also incorporating ultraviolet protection and termite and rodent resistance.

These models allow project designers to match fire performance and environmental requirements to the conditions of each route. A fully halogen-free solution may be preferred in enclosed stations, tunnels, evacuation paths, and areas containing sensitive electronic equipment. A low-halogen option may be selected where the project standard permits it and where a different balance of cost and performance is required.

Flame-retardant classifications ZA, ZB, and ZC can be supplied on request. The final code should be confirmed against the required conductor material, number of cores, cross-sectional area, armor, sheath color, screen construction, fire rating, and certification package.

9. Applications in Rail Transit Projects

9.1 Subway Main Lines

The cable is suitable for medium-voltage power supply networks serving subway lines. It can be used between receiving substations, distribution substations, station electrical rooms, and other designated power facilities, subject to the project’s electrical design.

9.2 Underground Stations and Tunnels

Underground stations and tunnels are among the most appropriate applications because they combine restricted ventilation with high passenger density and difficult maintenance conditions. Low-smoke and halogen-free properties can reduce the consequences of a fire, while termite and rodent resistance helps protect cable routes that may be difficult to inspect regularly.

9.3 Light-Rail and Urban Commuter Railways

Light-rail and commuter-rail systems may include both underground and open-air sections. The cable’s ultraviolet protection and environmental sheath properties make it adaptable to routes where sections of the network are exposed to sunlight, weather, soil, or trackside biological risks.

9.4 Depots and Maintenance Facilities

Rail depots include workshops, storage buildings, inspection tracks, substations, control rooms, and equipment areas. These locations require reliable power distribution and may experience vehicle movement, vibration, dust, and pest activity. A mechanically robust and biologically resistant medium-voltage cable can support dependable operation in these facilities.

9.5 Power Supply for Auxiliary Systems

In addition to traction-related systems, the cable may serve station lighting, ventilation, drainage pumps, fire-protection equipment, escalators, lifts, communication systems, and other auxiliary loads. The conductor size and installation arrangement must be selected through a complete load study.

10. Advantages Compared with Conventional Cable Solutions

10.1 Integrated Fire-Safety Design

Many conventional medium-voltage cables are selected primarily for voltage, current, and mechanical requirements. The present product adds low-smoke, halogen-free or low-halogen, and flame-retardant performance to the design. This integrated approach is particularly valuable in public transportation systems where the consequences of smoke and corrosive gases can be severe.

10.2 Protection against Biological Damage

Ordinary cable sheaths may not be designed for sustained termite or rodent exposure. This product family specifically addresses those hazards. The additional protection can help reduce emergency repairs, service interruptions, and the risk of hidden damage in inaccessible sections.

10.3 Broad Conductor Range

Conductor cross-sections up to 630 square millimeters allow the product range to serve different load levels and route configurations. This gives designers greater flexibility when balancing voltage drop, short-circuit capacity, installation space, and future expansion requirements.

10.4 Adaptability to Armored and Unarmored Installations

Both armored and unarmored configurations can be considered according to the route. This allows the cable to be matched to different mechanical conditions instead of applying one construction to every part of a rail network.

10.5 Suitable for Confined Environments

The product is designed with underground and enclosed environments in mind. Its smoke and gas performance, combined with XLPE insulation and specialized sheath protection, offers a more complete solution than a cable selected only for electrical capacity.

10.6 Support from a Broad Product Portfolio

The manufacturer supplies not only medium-voltage power cables but also electrical equipment wires, overhead conductors, railway cables, photovoltaic cables, wind-power cables, energy-storage cables, and other specialized products. This breadth can simplify procurement and technical coordination for large infrastructure contractors requiring several cable categories.

11. Manufacturing Capabilities

Wuxi Guanghuan Cable Co., Ltd. was founded in 1998 and is located in Guanlin Town, Yixing City, Jiangsu Province, an area recognized for its concentration of cable manufacturers. The company operates across a site of more than 100,000 square meters, including more than 45,000 square meters of building area.

The company reports more than 70 production and testing lines and employs more than 140 people, including over 30 technical professionals. Its reported annual sales revenue is approximately RMB 2 billion, with annual output value exceeding RMB 3 billion. These resources support the manufacture of large quantities of standardized products while maintaining dedicated processes for specialized cable designs.

For medium-voltage rail transit cables, manufacturing capability is not limited to extrusion capacity. It also includes conductor preparation, insulation extrusion, semiconductive layer application, screening, sheathing, armoring where required, dimensional measurement, electrical testing, packaging, and traceable quality documentation.

Online eccentricity monitoring is used to observe the concentricity of extruded layers during production. This is important because uneven insulation thickness can create an unbalanced electrical field and reduce the available safety margin. Continuous process monitoring allows operators to identify deviations earlier than end-of-line inspection alone.

High-voltage series-resonance test equipment is used for high-voltage testing, while partial-discharge detection equipment supports the evaluation of insulation quality in medium-voltage products. These capabilities are especially relevant to rail transit cables, where long service life and stable insulation performance are essential.

Material control is another important part of manufacturing. Insulation and sheath compounds must be stored, identified, dried or conditioned where required, and processed within controlled parameters. Incorrect material handling can affect electrical strength, mechanical flexibility, smoke performance, and long-term aging behavior.

12. Quality Management and Certifications

The company has obtained ISO 9001 quality management certification, ISO 14001 environmental management certification, ISO 45001 occupational health and safety certification, and ISO 50001 energy management certification. It also reports certification or recognition related to intellectual property, green management, social responsibility, and after-sales service.

These systems provide a framework for controlling procurement, production, inspection, nonconformance management, corrective action, environmental responsibilities, energy use, worker safety, and customer support. For large rail projects, a formal management system is valuable because cable quality must remain consistent across repeated manufacturing batches and long delivery schedules.

The company also reports CCC, TÜV, product carbon footprint, and China energy-saving and environmentally friendly product certifications for relevant products. The exact certificate applicable to a particular 35 kV cable should be confirmed during technical review, because certifications may differ according to model, voltage class, conductor size, and construction.

Qualification and capability verification for power cables and conductors conducted by the State Grid Corporation of China is another indication of the manufacturer’s experience with formal electrical-product assessment. Such experience can support the documentation and technical discipline required for infrastructure procurement.

13. Production and Inspection Process

13.1 Incoming Material Inspection

Conductors, insulation compounds, semiconductive materials, sheath compounds, metallic components, fillers, tapes, and packaging materials should be verified before entering production. Inspection may include dimensions, appearance, electrical properties, identification, batch traceability, and supplier documentation.

13.2 Conductor Processing

Conductor wires are drawn, annealed where applicable, stranded, compacted, and inspected according to the selected design. Process control focuses on dimensional uniformity, strand arrangement, surface condition, resistance, and mechanical integrity.

13.3 Insulation Extrusion

The XLPE insulation and associated semiconductive layers are applied through controlled extrusion. Temperature, pressure, line speed, cooling, cleanliness, and dimensional stability are monitored. The goal is to produce a smooth and concentric insulation system with minimal defects.

13.4 Cross-Linking and Cooling

The insulation is cross-linked under controlled conditions to achieve the required thermal and electrical properties. Cooling must be managed to minimize internal stress and preserve dimensional stability. Process records can help identify the conditions under which each production batch was manufactured.

13.5 Screening and Sheathing

Metallic screening components and the outer protective sheath are applied after the insulation system has been inspected. The sheath extrusion process must maintain thickness, surface quality, color, marking, and concentricity. For termite- and rodent-resistant products, the protective compound must be correctly formulated and uniformly distributed.

13.6 Final Testing

Final inspection may include conductor resistance, dimensional measurements, voltage withstand, sheath integrity, screen continuity, appearance, marking, and packaging checks. Type tests, sample tests, and routine tests are selected according to the product standard, contract, and project requirements.

14. Project Selection Guidance

When selecting this cable for a rail transit project, the engineering team should begin with the network voltage and grounding system. The rated voltage must correspond to the system’s operating and fault conditions. The required conductor cross-section should then be calculated from continuous load, voltage drop, short-circuit capacity, installation method, grouping, ambient conditions, and future expansion.

The fire environment should be evaluated separately. A tunnel with limited ventilation and high passenger occupancy may justify a halogen-free cable even if a lower classification is technically permitted elsewhere. Areas containing signaling, communication, and control equipment may also benefit from reduced corrosive emissions.

Biological exposure should be considered during route planning. If the cable passes through soil, landscaping areas, agricultural land, humid service corridors, or locations known for rodent activity, termite- and rodent-resistant construction can provide a meaningful additional layer of reliability.

Mechanical protection must also be reviewed. Armored construction may be appropriate where the cable faces impact, crushing, or difficult handling conditions. Unarmored cable may be suitable where the route already provides sufficient protection and where the installation design benefits from a smaller diameter and lower weight.

Finally, the project should define the required documentation. This may include product drawings, construction descriptions, material certificates, routine test reports, type-test reports, factory acceptance records, installation instructions, inspection plans, and certificates of conformity.

15. Maintenance and Service-Life Considerations

Although the cable is designed for long-term operation, maintenance remains important. Inspection teams should check accessible cable routes for sheath damage, abnormal heating, water accumulation, movement, loose cleats, signs of pest activity, and unauthorized modifications.

Thermal monitoring can help identify overloaded circuits, poor connections, unbalanced phase conditions, or ventilation problems. Where the cable is installed in a tunnel or enclosed room, ventilation and drainage should be maintained so that the surrounding environment does not unnecessarily accelerate aging.

Joint boxes and terminations deserve particular attention. These are common locations for installation errors, moisture ingress, mechanical stress, and overheating. Inspection intervals should be based on the importance of the circuit, environmental conditions, operating history, and the railway operator’s maintenance procedures.

When a cable is damaged, repairs should use compatible accessories and procedures. Improvised repairs, unsuitable tapes, incorrect screen bonding, or unapproved jointing methods can compromise medium-voltage insulation and invalidate the original design assumptions.

16. Sustainability and Environmental Considerations

Low-smoke and halogen-free materials can reduce the corrosive and toxic impact of a fire. This is beneficial not only for passenger safety but also for the protection of station equipment and the reduction of post-fire cleanup and replacement requirements.

The company’s environmental management and energy management systems provide a framework for controlling production-related environmental impacts. Its reported green-factory and product carbon-footprint recognitions may also support infrastructure owners seeking to improve environmental performance across the project life cycle.

Durability is itself an environmental advantage. A cable that resists biological attack, remains electrically stable, and avoids premature replacement reduces the material, labor, transport, and disposal impacts associated with repeated repairs. Proper selection, installation, and maintenance are therefore important parts of sustainable cable use.

17. Why Manufacturer Capability Matters

Specialized rail transit cables require more than a generic cable catalog. The manufacturer must understand the interaction between electrical insulation, fire performance, mechanical protection, environmental exposure, and installation requirements. It must also be able to produce consistent cable lengths, manage large project orders, provide technical documents, and respond to inspection or customization requests.

A company with multiple production lines and broad experience in energy, rail, construction, and industrial cable categories can coordinate materials and manufacturing resources more effectively. Its technical personnel can support model selection, conductor sizing, cable construction, test planning, and installation questions.

Wuxi Guanghuan Cable Co., Ltd. has developed a portfolio of more than 100 product categories and over 30,000 specifications under its registered product range. This product breadth is relevant to rail projects because the same project may require medium-voltage power cables, low-voltage equipment wires, control cables, overhead conductors, communication-related products, and cables for renewable or storage systems.

The company’s combination of production scale, testing equipment, quality systems, technical staff, and project experience gives it the foundation to supply cable products for demanding infrastructure applications. For purchasers, the key benefit is not only the individual cable specification but also the ability to obtain consistent technical support and documented quality throughout the project.

18. Frequently Asked Questions

Q1: What is the main application of this 35 kV cable?

It is primarily designed for medium-voltage power distribution in subways, light-rail systems, urban commuter railways, tunnels, underground stations, depots, and related transportation infrastructure.

Q2: What rated voltage options are available?

The product information identifies rated voltage options of 21/35 kV and 26/35 kV. The appropriate option must be selected according to the railway network design and grounding conditions.

Q3: Is the cable halogen-free?

The product family includes a halogen-free, low-smoke construction and a low-halogen, low-smoke construction. The halogen-free model is generally preferred where strict fire-safety and low-corrosion requirements apply.

Q4: What is the maximum continuous conductor temperature?

The maximum permissible continuous conductor temperature is 90 degrees Celsius, subject to the applicable installation and loading conditions.

Q5: What is the short-circuit conductor temperature?

The specified maximum short-circuit conductor temperature is 250 degrees Celsius. The permitted duration must be confirmed in the final technical documentation because the supplied material contains inconsistent references to short-circuit duration.

Q6: Can the cable resist termites and rodents?

Yes. The specialized sheath and material design provide termite- and rodent-resistant performance, making the cable suitable for routes exposed to biological damage.

Q7: What is the largest conductor cross-section available?

The production range covers conductor cross-sections up to 630 square millimeters or below, depending on the selected cable design.

Q8: What bending radius should be used?

For installation, the minimum bending radius is 20D for single-core unarmored cable, 15D for single-core armored and three-core unarmored cable, and 12D for three-core armored cable. D means the cable’s outside diameter.

Q9: Can armored versions be supplied?

Yes. The product information provides separate installation requirements for armored and unarmored cables. The final construction should be selected according to mechanical exposure, route design, grounding, and project specifications.

Q10: What fire-performance options are available?

Low-smoke, halogen-free and low-halogen constructions are available, and ZA, ZB, or ZC flame-retardant cable grades may be supplied according to request.

Q11: What standard governs production?

The supplied information identifies GB/T 12706.3-2020 as the applicable enterprise technical standard basis. Project-specific standards and acceptance requirements should also be reviewed before ordering.

Q12: Why is low smoke important in subway applications?

Low smoke improves visibility during evacuation and firefighting. It can also reduce the amount of corrosive contamination deposited on electrical, signaling, communication, and control equipment.

Q13: Does the cable require preheating during installation?

General guidance specifies an installation ambient temperature of no lower than 0 degrees Celsius, with preheating required if the temperature is lower. The approved installation manual for the exact cable construction should be followed.

Q14: What testing is performed on the cable?

Testing may include conductor resistance, dimensional inspection, voltage withstand, sheath integrity, screen continuity, and other routine, sample, or type tests. The cable is specified to pass 3.5 U0 alternating-current and direct-current voltage resistance tests.

Q15: What information should be provided when requesting a quotation?

The purchaser should provide rated voltage, conductor material, conductor cross-section, number of cores, armor requirement, screen arrangement, sheath type, fire classification, required cable length, installation environment, applicable standards, delivery schedule, and required inspection documentation.

19. Conclusion

The 35 kV power cable for subway and urban rail transit is engineered for the combined electrical, environmental, and safety demands of modern rail infrastructure. Its medium-voltage XLPE insulation system supports reliable power transmission, while low-smoke and halogen-free or low-halogen sheath options help reduce the risks associated with fire in enclosed public spaces.

Its resistance to termites and rodents provides an additional advantage over conventional cables that may be vulnerable to biological damage. The availability of armored and unarmored constructions, conductor sizes up to 630 square millimeters, multiple fire-performance options, and voltage ratings of 21/35 kV and 26/35 kV allows the product to serve varied rail transit layouts.

Reliable cable performance also depends on manufacturing discipline. Controlled extrusion, online eccentricity monitoring, high-voltage testing, partial-discharge detection, material management, formal quality systems, and documented inspection procedures all contribute to product consistency. The manufacturer’s broad cable portfolio, technical resources, certifications, and production capacity further support its ability to serve complex infrastructure projects.

For subway, light-rail, and urban commuter railway applications, the correct cable is one that protects more than the power circuit. It must also protect passengers, railway personnel, equipment, maintenance operations, and the continuity of transportation services. By combining electrical stability with fire safety and biological resistance, this 35 kV product family provides a practical solution for demanding urban rail power networks.

References

1. GB/T 12706.3-2020, Power Cables with Extruded Insulation and Their Accessories for Rated Voltages from 1 kV to 35 kV.

2. Technical product information for 35 kV power cables for subway and lightweight track, including product construction, operating characteristics, model codes, and installation requirements.

3. Technical documentation concerning low-smoke, halogen-free cable combustion performance, acid-gas emission, pH value, conductivity, and light transmittance.

4. Manufacturer quality-management, environmental-management, occupational-health, and energy-management system information.

5. Medium-voltage cable installation and maintenance principles for railway power distribution systems.

6. General engineering practices for XLPE-insulated power cables, cable terminations, cable joints, screen bonding, and short-circuit coordination.

Product: Power Cable for Subway and Urban Rail Transit (Rated Voltage 35kV)