I. Product Overview
The 26/35kV fully cold-shrink three-core intermediate joint is a cold-shrink accessory specifically designed for intermediate connections of 26/35kV three-core power cables. Made of high-performance silicone rubber, it relies on its own elastic shrinkage to achieve insulation, electric field control, sealing and protection of the cable intermediate joint. No heating tools are required, and installation is convenient. It is widely used in intermediate connection scenarios of 35kV power cables to ensure the safe and stable operation of cable joints.
II. Product Characteristics
1. Insulation and electrical properties
- Made of high-quality silicone rubber, it has excellent insulation properties and can effectively withstand the working voltage of 26/35kV systems. Its power frequency withstand voltage and impact withstand voltage performance meet industry standards, ensuring the insulation safety of cable joints.
- With its own stress control structure, it can effectively and uniformly distribute the electric field in the cable joint, avoid partial discharge caused by electric field concentration, and improve the long-term operational reliability of the joint.
- After cold shrinking and retraction, it can fit tightly with the cable body and conductor connecting tube to form a continuous and reliable sealing structure, preventing moisture, rainwater, dust and oil from entering the cable joint. It has excellent moisture-proof, waterproof, anti-fouling and anti-salt spray performance, and IP68 protection.
2. Installation and Construction Characteristics
- With its fully shrinkable design, it requires no open flame or heating tools. Installation is achieved through the elastic retraction of the pre-expanded diameter, making the installation process safe and convenient, with no fire hazards. It is suitable for special construction scenarios such as indoor, outdoor, and explosion-proof applications.
- The complete set includes all the accessories needed for joint fabrication (insulating tube, stress tube, sealant, installation tools, etc.), eliminating the need to purchase additional parts during construction, significantly shortening joint fabrication time and reducing construction costs.
- After installation, the connector has a neat and aesthetically pleasing appearance, without the uneven shrinkage, bubbling, or deformation issues common in heat-shrink products. It exhibits good consistency and facilitates subsequent maintenance and inspection.
3. Environmental and Weather Resistance
- With excellent weather resistance, it can adapt to a wide temperature range of -40℃ to +90℃. The elasticity and insulation properties of silicone rubber do not decrease under high and low temperatures, and there is no risk of cracking, embrittlement or deformation. It is suitable for various scenarios such as indoor, outdoor, buried and cable trench.
- It is anti-aging, anti-ultraviolet, and resistant to ozone corrosion. It can be exposed to outdoor and buried environments for a long time, with a service life of more than 20 years. It requires no maintenance and reduces the cost of operation and maintenance.
- It is resistant to chemical corrosion and can adapt to harsh environments such as humidity, dust, salt spray, and mild acid and alkali. It has no risk of corrosion or degradation and is suitable for industrial and mining enterprises, coastal areas and other scenarios.
4. Mechanical and Adaptation Characteristics
- Silicone rubber materials have high mechanical strength, are tear-resistant and tensile-resistant, and can withstand mechanical stress during construction and operation without the risk of breakage or cracking. They are suitable for cable laying and tensile and bending conditions during operation.
- It is compatible with 26/35kV three-core power cables, covering common cross-sectional specifications, with strong versatility, and suitable for installation scenarios such as underground, cable trench, and cable well.
- The connector has a compact structure and small size, making it suitable for installation in narrow spaces without any space limitations.
III. Technical Parameters
| Parameter categories | project | Technical indicators |
| Electrical parameters | Applicable system voltage | 26/35kV AC |
| Rated voltage | 35kV | |
| Power frequency withstand voltage (5min) | 95kV, non-breakdown | |
| Impact resistance (peak) | 200kV, non-breakdown | |
| Insulation resistance | ≥1000MΩ | |
| Partial discharge quantity | ≤5pC (at 1.5 times rated voltage) | |
| Structural and material parameters | Main material | silicone rubber |
| Applicable cable core count | Three-core | |
| Applicable cable cross-section | 25mm²~400mm² (select according to specifications) | |
| Protection level | IP68 | |
| Structural form | Fully shrinkable intermediate joint (complete set) | |
| Environmental parameters | Applicable altitude | ≤2000m (Customization available for high altitudes) |
| Ambient temperature | -40℃/ +90℃ (operating temperature), -40℃/ +70℃ (storage temperature) | |
| relative humidity | ≤100% (no condensation) | |
| Seismic resistance level | Level 8 | |
| Implementation Standards | GB/T 12706 “Extruded insulated power cables and accessories with rated voltage of 1kV (Um=1.2kV) to 35kV (Um=40.5kV)” and IEC 60840 “Test methods and requirements for extruded insulated power cables and accessories with rated voltage of 30kV (Um=36kV) and above to 150kV (Um=170kV)”. |
IV. Product Composition List
| Serial Number | name | use |
| 01 | Cold shrink joint insulation body | Provide main insulation and protection for cable joints |
| 02 | Insulating tape / Semi-conductive tape | Connector interface insulation and electric field control |
| 03 | Installation accessory box (sealing glue/cleaning agent/semi-conductive grease) | Clean cable surface, seal joint interfaces, and create a uniform electric field. |
| 04 | Metal pressure ring/fastener | Fixed joint and cable body |
| 05/06 | Conductor connecting tube / shielding braided tape | Cable conductor connection, joint shielding and grounding |
| 07 | Sandpaper/Cleaning cloth | Cable surface grinding and cleaning |
| 08 | Waterproof sealant/filler | Moisture-proof and waterproof seal for connectors |
| 09/10 | Insulating tape / Waterproof tape | Connector interface insulation and waterproofing |
| 11 | tape measure | Cable stripping length measurement |
| 12 | Protective gloves | Construction safety protection |
| 13 | Waterproof sleeve/protective tape | External waterproof and anti-fouling protection for the connector |
| 14 | Utility knife/wire stripper | Cable stripping and splice installation |
| 15 | Installation instructions/process card | Joint fabrication and construction instructions |
| 16 | Cable marking tape | Cable connector marking |
| 17 | Quality Certificate/Inspection Report | Product quality certification documents |
V. Scope of Application
- Applicable voltage level : 26/35kV AC power cable system.
- Applicable scenarios :
- Scenarios involving intermediate connections and extensions of 35kV three-core power cables;
- Cable joints in various scenarios, including underground installations, cable trenches, cable wells, and outdoor pole installations;
- Cable joints for special construction scenarios such as explosion-proof and fire-prohibited environments;
- Cable joints in harsh environments such as dampness, dust, and salt spray.
- Function and Purpose : Provides insulation, electric field control, sealing and protection for intermediate connections of 26/35kV three-core power cables, prevents moisture, rainwater and dust from entering the cable joint, ensures uniform electric field distribution at the joint, guarantees safe and stable operation of the cable joint, and avoids leakage, short circuit and fault tripping accidents caused by joint insulation failure, electric field concentration and poor sealing.
VI. Usage Conditions
1. Normal operating conditions
- Altitude: ≤2000m;
- Ambient temperature: -40℃ to +90℃; cable operating temperature shall not exceed the conductor’s long-term allowable operating temperature.
- Relative humidity: ≤100% (no condensation);
- Environmental conditions: No corrosive gases, no flammable or explosive media, no severe vibration or impact;
- Installation method: cold shrink installation. Simply pull out the support core wire to complete the shrinkage. The installation space must meet the bending radius requirements of the cable joint.
2. Special usage conditions (customization required)
- The altitude exceeds 2000m;
- The ambient temperature exceeds the range of -40℃ to +90℃;
- Severely polluted, salt spray, and chemically corrosive environments;
- High vibration and high impact conditions;
- Scenarios requiring non-standard cable cross-sections and special protection levels.
VII. Installation and Maintenance
1. Installation Requirements
- Before installation, inspect the product appearance. The silicone rubber connector should be free of cracks, damage, and bubbles. The support core wire should be intact and free of deformation. All accessories should be complete and undamaged.
- Cut the cable according to the cable joint manufacturing process. The cutting length must meet the joint specification requirements. Avoid damaging the cable insulation layer during the cutting process. After cutting, use a cleaning agent to clean the cable surface to remove oil, dust, and semi-conductive layer residue, and ensure that the surface is dry and clean.
- After crimping the cable conductor connecting tube, grind the burrs at the crimped joint and clean the surface of the connecting tube. Install the cold shrink insulation tube, stress tube, and connector body in sequence. After adjusting the position, slowly pull out the support core wire to make the connector shrink evenly and ensure that each component fits tightly with the cable body without offset, air bubbles, or wrinkles.
- After installation, install the shielding braided tape and waterproof sleeve according to the process requirements, check that the grounding connection of the joint is reliable, and confirm that the joint shrinks evenly, without damage or gaps, and the installation is complete.
2. Maintenance Requirements
- Regularly inspect the appearance of the connectors. The silicone rubber connectors should be free of cracks, damage, discharge marks, and dirt accumulation. The connectors should fit tightly with the cables without looseness or gaps, and the waterproof sheaths should be intact and undamaged.
- Regularly test the insulation resistance and partial discharge of the joints to ensure that the performance meets the requirements and to promptly identify potential insulation hazards.
- Clean the surface of the connector to remove dust and dirt, keep the connector surface dry and clean, avoid corrosion from oil and chemicals, and regularly check the integrity of the waterproof sleeve to prevent the connector from getting damp.
- If any abnormalities such as cracks, damage, discharge, excessive insulation resistance, or damage to the waterproof sheath appear at the joint, the joint must be replaced in time, and operation with defects is strictly prohibited.
VIII. Precautions
- The product must be installed, debugged, and maintained by professional electrical personnel with high-voltage cable joint manufacturing qualifications. Operation by non-professionals is strictly prohibited.
- The product must be used with 26/35kV power cables of the corresponding cross-section and number of cores. It is strictly forbidden to use cables of different specifications, otherwise it will lead to insulation and sealing failure and cause safety accidents.
- The product must not be disassembled or modified without authorization, otherwise the warranty and safety guarantee will be lost. It is strictly forbidden to forcibly stretch or cut the joints to avoid damaging the silicone rubber material.
- During installation, cables must be stripped, conductor connectors crimped, and components installed according to process requirements to avoid damaging the cable insulation layer. Support core wires must be pulled out slowly to avoid uneven joint shrinkage or misalignment.
- When storing, it should be placed in a dry, ventilated, and cool environment, avoiding direct sunlight, high temperature, humidity, and compression. It is strictly forbidden to contact with sharp objects that may damage the connectors. The supporting core wires must be kept intact to avoid deformation.
- During operation, the condition of the joints should be checked regularly to avoid external pressure or collisions, and to prevent joint damage, seal failure, and damage to the waterproof sleeve.
IX. Model Description
| Model Identification | meaning |
| 26/35kV | Applicable system voltage levels: 26/35kV power cables |
| Total cold shrink | Installation method markings, fully shrinkable design. |
| Three-core | Compatible with cable core count markings, three-core cable |
| intermediate connection | Product type identification, cable joint |
| XXmm² | Compatible with cable cross-section markings, such as 70mm², 120mm², 240mm², 400mm², etc. |
X. Implementation Standards and Certification
- International Standard: IEC 60840 “Test methods and requirements for extruded insulated power cables and their accessories with rated voltages of 30kV (Um=36kV) and above up to 150kV (Um=170kV)”;
- National Standard: GB/T 12706 “Extruded Insulated Power Cables and Accessories with Rated Voltages from 1kV (Um=1.2kV) to 35kV (Um=40.5kV)”;
- The product has passed the type test of the National Wire and Cable Quality Supervision and Inspection Center and meets the national power industry standards.
XI. After-sales service
- Product warranty period: 18 months from the date of manufacture, or 12 months from the date of commissioning (whichever comes first).
- During the warranty period, products will be repaired or replaced free of charge if quality issues arise.
- We provide technical support, installation guidance, and customized services (adaptation to special specifications and working conditions).
Document Description
The technical parameters in this manual are based on standard operating conditions. Special operating conditions need to be customized according to actual needs. The final specifications shall be subject to the product technical agreement and type test report.
Appendix: Product outline diagram
