230kV cable intermediate joint, with its voltage level typically corresponding to the rated voltage of 127/220kV, is a critical component in high-voltage transmission lines. It primarily falls into two functional types and is widely adopted with a prefabricated structure.
1. Main Types and Differences:
Based on different electrical functions, 230kV cable intermediate joints are primarily divided into the following two types:
- Straight-through connector is primarily used to connect two sections of cable, maintaining the electrical connection of conductors while preserving the continuity of the metal sheath (such as copper tape or lead sheath). It is commonly employed in cable line connections to achieve length extension.
- Insulation joint In addition to connecting conductors, its key feature is to electrically insulate and disconnect the metal sheath or shielding layer at both ends of the joint. Used in cross-interconnected systems for high-voltage cables to reduce induced voltage in the sheath and circulating current losses, typically employed for long-distance lines.
2. Structure and Characteristics: The current mainstream product is the prefabricated modular intermediate joint, which is designed with full consideration for the operational requirements of high-voltage cables
Main structure: The joint core adopts high-precision prefabricated components (such as imported EPDM rubber or epoxy resin), with internal insulation and stress control parts pre-molded as a whole in the factory to ensure stable quality.
Insulation and Shielding: The main body features a fully dry structure, eliminating the risk of oil leakage. It incorporates precisely designed stress cones to evenly distribute the electric field and prevent partial discharge.
External Protection: Typically equipped with a fiberglass waterproof enclosure, internally filled with polyurethane or insulating waterproof sealant, it can be directly buried or installed in cable wells, effectively resisting mechanical stress and moisture intrusion.
3. Product Application: Primarily used for 230kV transmission lines, suitable for intermediate connections of XLPE-insulated power cables, ensuring the reliability and stability of mainline power transmission.
4. Applicable Standards: This product complies with the GB/Z 18890 standard "Rated Voltage 220kV Cross-linked Polyethylene Insulated Power Cables and Their Accessories" and relevant IEC standards.
5. Construction Key Points: Although the high-voltage cold-shrink process is similar in principle to medium and low-voltage ones, it requires extremely high precision. An improved technique involves adding an epoxy resin mixture for sealing treatment on the basis of cold-shrink joints, thereby enhancing waterproofing, moisture resistance, heat resistance, and electrical insulation performance.
