The long-term sealing reliability of DC cable connectors is a key element in ensuring the safe and stable operation of cable systems. Their design must comprehensively consider material properties, structural optimization, process control, and environmental adaptability, utilizing multiple technical approaches to form a systematic solution.
The selection of sealing materials is fundamental. DC cable connectors must utilize elastomeric materials that are highly compatible with the cable insulation, such as silicone rubber and EPDM. These materials not only offer excellent weather resistance, UV resistance, and chemical stability, but also maintain elastic deformation capabilities during long-term thermal cycling. For example, silicone rubber maintains sealing performance within a temperature range of -50°C to 200°C and is insensitive to DC electric fields, preventing sealing failure due to material aging. Furthermore, the sealant selected must be compatible with the cable sheath material to ensure reliable bonding with the main material, such as cross-linked polyethylene (XLPE) or ethylene propylene diene rubber (EPR).
In terms of structural design, DC cable connectors generally utilize a composite structure combining multiple barriers and elastic compensation. First, a three-dimensional protection system is created through radial sealing rings and axial compression devices. The radial sealing ring utilizes the elasticity of its material to fill the microscopic gaps between the cable and the connector, while the axial compression mechanism maintains long-term pressure through bolts or snap-fit structures. Second, a multi-level sealing interface is established, such as a primary sealing layer, a secondary sealing layer, and a dust barrier, gradually reducing the path for moisture intrusion. Third, elastic compensating elements, such as bellows or springs, are introduced to absorb displacement caused by thermal expansion and contraction, preventing cracking on the sealing surface due to stress concentration. For example, in high-voltage DC cable connectors, the transition zone between the stress cone and the reinforced insulation layer adopts a tapered design, combined with an elastic bushing, to both equalize the electric field and enhance the sealing effect.
Process control is critical to sealing reliability. Connector manufacturing must be completed in a clean environment, with strict control over temperature, humidity, and dust particles. When crimping or welding conductors, the contact resistance between the connector and the core must be less than 1.2 times that of the core of the same length to prevent local overheating that may cause degradation of the sealing material. During insulation treatment, silicone grease should be evenly applied to the primary insulation surface to enhance sealing and reduce electric field concentration. Before installing the inner and outer sheaths, sealant should be applied to the joints to ensure that no air gaps exist. For example, wrap-around connectors use a gradient wrapping of multiple layers of semi-conductive tape and insulating tape to form a dense protective layer. This, combined with the shrinkage of the heat shrink tubing, creates a seamless seal.
Environmental adaptability is designed to address the specific operating conditions of DC cables. In humid environments, connectors must be condensation-resistant by using built-in desiccant or hydrophobic materials to absorb moisture. For buried cables, the connector outer sheath should be made of high-density polyethylene (HDPE) and equipped with a metal protective shell to prevent corrosion from chemical substances in the soil. In environments with frequent vibration, such as rail transit, the connector structure should include a buffer layer, using rubber gaskets or spring dampers to reduce the impact of mechanical stress on the sealing surface.
Long-term reliability verification requires support from simulation experiments and actual operating data. In accelerated aging tests, connectors must be continuously operated under combined conditions of high temperature, high humidity, and high voltage to detect degradation of sealing performance. For example, in an environment of 85°C and 85% relative humidity, the sealing interface must remain leak-free for 720 hours. In actual projects, online monitoring systems collect real-time parameters such as connector temperature and partial discharge, combined with regular inspections, to detect sealing defects in advance.
The long-term sealing reliability of DC cable connector structures relies on the deep integration of materials science, structural mechanics, and manufacturing processes. By optimizing the sealing system, strengthening structural compensation, strictly controlling the manufacturing process, and improving environmental adaptability, the connector's service life can be effectively extended, providing a solid foundation for DC transmission systems.
