Optimizing electric field distribution in a composite shielded insulated tubular busbar body to reduce the risk of partial discharge requires comprehensive approaches across structural design, material selection, manufacturing processes, installation, and maintenance. By constructing a multi-layer shielding system, optimizing insulation parameters, controlling interface defects, and standardizing operating procedures, the electric field is uniformized and local electric field distortion is suppressed.
At the structural level, the multi-layer shielding system employed in the composite shielded insulated tubular busbar body is a key approach to optimizing electric field distribution. A semiconductor shielding layer wrapped around the conductor surface eliminates electric field concentration and prevents localized excessive field strength caused by sudden changes in conductor curvature. A metal mesh or copper foil shielding layer placed outside the main insulation layer not only shields against external electric field interference but also, through grounding, directs induced charges to the ground, preventing electric field accumulation on the insulation surface. A high-insulation-strength outer layer protects against electric field distortion caused by environmental factors. For example, a certain composite shielded insulated tubular busbar body adds a semiconducting buffer layer between the conductor and the insulation layer, reducing the range of electric field intensity fluctuations and significantly reducing the risk of partial discharge.
Material selection has a crucial impact on the uniformity of electric field distribution. The primary insulation material, such as polytetrafluoroethylene (PTFE) or cross-linked polyethylene (XLPE), must possess high dielectric strength, low dielectric loss, and excellent aging resistance. Its dielectric constant must match that of the conductor material to avoid electric field concentration caused by dielectric differences. The semiconducting shielding layer material must have controlled resistivity to ensure effective charge conduction without inducing eddy current losses due to excessive conductivity. For example, a semiconducting material composited with EPDM rubber and carbon black offers a stable volume resistivity and can achieve an electric field gradient transition. The metal shielding layer must be made of a highly conductive material, such as copper or aluminum, and a braiding process must be used to increase shielding coverage and reduce electric field leakage.
The precision of the manufacturing process directly impacts the uniformity of the electric field distribution. The conductor surface must be polished to remove defects such as burrs and scratches to prevent electric field distortion caused by surface roughness. The insulation layer should be vacuum impregnated or extruded to ensure material density and prevent the presence of air gaps or micropores.
For example, one company optimized the epoxy resin casting process to reduce the air gap ratio in the insulation layer, thereby increasing the partial discharge inception voltage. Interface treatment between the shielding layer and the insulation layer is also critical. Semi-conductive tape wrapping or spraying should be used to achieve a seamless connection between the layers and avoid electric field concentration caused by interfacial gaps.
Compliance with installation and maintenance procedures is crucial for the long-term stability of the electric field distribution. Equipotential design should be used at the joints of the composite shielded insulated tubular busbar body. Copper busbar transitions or silver plating of the contact surfaces should be used to reduce contact resistance and prevent local overheating and electric field distortion caused by poor connections. Mechanical stress should be avoided during installation. For example, flexible lifting straps should be used to secure the composite shielded insulated tubular busbar body to prevent deformation of the insulation layer due to compression. Temperature and humidity must be controlled in the operating environment, and dehumidification or air conditioning systems must be installed to prevent dielectric degradation caused by moisture in the insulation material. Regular monitoring of partial discharge levels, using ultrasonic or ultra-high frequency detection technology, can promptly identify potential defects and initiate remedial measures.
Furthermore, simulation analysis and experimental verification are important auxiliary tools for optimizing electric field distribution. Using finite element analysis software to create a three-dimensional electric field model of a composite shielded insulated tubular busbar body, the electric field distribution patterns under different structural parameters can be simulated, providing a theoretical basis for design optimization. For example, a study found through simulation that adding an intermediate capacitor screen to the insulation layer can improve axial electric field uniformity. Type testing and factory testing must strictly adhere to standards, such as conducting power frequency withstand voltage tests, partial discharge measurements, and lightning impulse tests, to ensure that the composite shielded insulated tubular busbar body maintains electric field stability under extreme operating conditions.
