Performance Comparison Of Terminal Blocks At Different Voltage Levels
As the core component of electrical connections, terminal blocks exhibit significant differences in performance at different voltage levels, mainly reflected in material voltage resistance, structural design, safety protection, and differentiation of applicable scenarios.
Low voltage scenario (≤ 500V)
Low voltage terminal blocks are often made of copper or copper alloy materials, utilizing their high conductivity and ductility to achieve stable connections. For example, plug-in terminals enhance their oxidation resistance through tin plating treatment, making them suitable for frequent plugging and unplugging scenarios such as electronic devices and instruments; Spring type terminals use elastic metal sheets to clamp wires, with strong seismic resistance, and are commonly used in scenarios such as distribution boxes and lighting systems that require quick wiring. The design of low-voltage terminals emphasizes compactness, such as U-shaped terminals that use screws to crimp wires, which have a simple structure and low cost, and are widely used in home circuit renovation.
Medium and high voltage scenarios (1kV-35kV)
Medium and high voltage terminals need to withstand higher electric field strength and have stricter material selection. Aluminum or copper aluminum composite materials have become the preferred choice for solar photovoltaic systems and medium voltage distribution cabinets due to their electrochemical corrosion resistance. For example, the DTL copper aluminum nose solves the potential difference problem when directly connecting copper and aluminum through a transition layer design, avoiding poor contact caused by high-temperature oxidation. Structurally, the medium and high voltage terminals adopt a thickened insulation layer and anti arc design. For example, circular terminals can maintain a creepage distance of ≥ 25mm at 10kV voltage by increasing the internal aperture and insulation sleeve thickness to prevent arc flashover.
Ultra high voltage scenario (≥ 110kV)
Ultra high voltage terminals must meet reliability requirements in extreme environments. Stainless steel or high-strength alloy materials have become mainstream, with a tensile strength of over 600MPa and the ability to withstand mechanical stress caused by short-circuit currents. For example, the SC copper nose uses a special crimping process to achieve a contact surface resistance of ≤ 0.5 μ Ω, ensuring that the temperature rise does not exceed 65K under a short-circuit current of 200kA. In addition, the ultra-high voltage terminal adopts a double insulation structure, such as JG type terminals wrapped with a silicone rubber insulation layer outside the copper conductor and then fitted with an epoxy resin shell, with a withstand voltage level of up to 220kV, suitable for substations, high-voltage transmission lines and other scenarios.
The core logic behind performance differences
The demand for terminal performance increases exponentially with the improvement of voltage levels. In low voltage scenarios, contact resistance and temperature rise are the main contradictions; In medium and high voltage scenarios, it is necessary to focus on addressing insulation breakdown and electrochemical corrosion; In ultra-high voltage scenarios, it is necessary to balance mechanical strength, thermal stability, and electromagnetic compatibility. For example, the standard contact resistance for low-voltage terminals is ≤ 5m Ω, while for ultra-high voltage terminals it needs to be ≤ 0.1m Ω to reduce line losses. In addition, high-voltage terminals must pass the lightning impulse test (1.2/50 μ s waveform, peak voltage ≥ 200kV) under the IEC 62271 standard to ensure stable operation even under extreme voltage fluctuations.
Industry Trends and Standards
With the acceleration of new energy grid integration and smart grid construction, terminal blocks are developing towards high voltage, high current, and modularity. For example, dedicated terminals for photovoltaic inverters have achieved 1500V DC withstand voltage, while integrating temperature sensors for real-time monitoring. In terms of international standards, IEC 60947-7-1 requires an IP20 protection level for low voltage terminals, while GB/T 14048.7 stipulates that medium and high voltage terminals must pass a salt spray test (96 hours, 5% NaCl solution) to adapt to high humidity environments in coastal areas. These standards drive terminal manufacturers to continuously optimize material formulations and structural designs, such as using nano coating technology to improve insulation performance, or optimizing contact surface pressure distribution through finite element analysis to achieve a balance between performance and cost.
