The cable branch box has been widely used in power distribution systems in recent years. It is broadly applicable in the 10kV cable distribution systems for urban industrial parks, residential areas, commercial zones, mining areas, and large enterprises such as steel, automotive, petroleum, chemical, and cement industries, as well as other scenarios where it serves as a ring network connection for power distribution. It is an ideal device for urban grid transformation.
There are several material options for the cable branch box: ordinary steel, aluminum-zinc coated steel, and mirror-finished stainless steel. Most boxes are made of metal, but metal boxes require rust prevention treatment, both externally and internally. If the distribution box is not well sealed, an "electric breathing" phenomenon can occur. What is electric breathing? When exposed to direct sunlight, due to the greenhouse effect, the box temperature can far exceed the external temperature. As the box heats up, the internal gas expands and forces air out. When sunlight is absent, the box temperature drops below the external temperature, and it absorbs external air. This is electric breathing. Metal boxes also face challenges in corrosion protection. Despite the many corrosion prevention methods, it is almost impossible for corrosion-resistant materials to fully penetrate the steel structure. Even with the emergence of nanotechnology, the issue of corrosion has not been fully resolved. Ensuring that the anti-corrosion material doesn’t peel and penetrates deeply is generally challenging. Thus, periodic maintenance of corrosion prevention is required, often annually. From an electrical perspective, the box material, whether iron or steel, is conductive, which necessitates a distance of no less than 2 cm between the bare conductor and the box body to prevent potential leakage. This requirement makes the box larger, and the wires need to be of higher quality with proper insulation measures to prevent conduction between the conductive parts and the steel material.
A new type of cable branch box material adopts eco-friendly SMC material (Sheet Molding Compound), which is a glass fiber-reinforced polyester that can resist corrosion from acid, alkaline, and saline soils, as well as air. Under such conditions, the box can guarantee a service life of 30 years. SMC composite material is a kind of resin-based composite, first appearing in Europe in the early 1960s, followed by developments in the U.S. and Japan around 1965. China introduced advanced SMC production lines and technologies from abroad in the late 1980s. The SMC composite material has the following advantages:
Good Electrical Performance
Fiber-reinforced polyester materials used in electrical products have the following electrical properties:
1. Insulation resistance (after 24h water immersion): 1.0x10 MΩ
2. Arc resistance: 180 seconds
3. Comparative tracking index (CTI): ≥600V
The insulation protection and anti-creep properties meet the relevant DIN/VDE standards. This material not only provides excellent electrical insulation but also maintains good dielectric performance at high frequencies, unaffected by electromagnetic effects, and does not reflect electromagnetic waves. These properties far surpass those of metal materials.
Chemical Corrosion Resistance
Fiber-reinforced polyester materials exhibit excellent resistance to acids, dilute alkalis, salts, organic solvents, seawater, and other corrosive substances, whereas metal materials are vulnerable to acid and seawater corrosion.
Lightweight and Strong
Specific strength and specific modulus are key indicators of a material's load-bearing capacity. The specific modulus of fiber-reinforced polyester materials is comparable to steel, but their specific strength can be up to four times that of steel.
Excellent Fatigue Resistance
The tensile strength of fiber-reinforced polyester materials is slightly better than that of steel. The fatigue limit of steel and most metal materials is 40%-50% of their tensile strength, while the fatigue limit of fiber-reinforced composites is generally higher, reaching up to 70%-80%.
Low Notch Sensitivity
When components are overloaded and some fibers break, the load is rapidly redistributed to the unbroken fibers, restoring mechanical balance. This is a unique advantage over metal components.
Low Thermal Conductivity and Small Expansion Coefficient
The thermal stress generated by temperature differences is much smaller in these materials compared to metals.
Superior UV and Aging Resistance
Among non-metallic materials, fiber-reinforced polyester has the best aging resistance. Tests show that, under different climates, the maximum surface aging thickness after 20 years is less than 50 microns. Most boxes have a minimum thickness of 5mm, which is less than 1% of the box thickness, meaning it has no significant effect on the mechanical properties of the box. Additionally, our company uses a special UV-resistant surface treatment, further enhancing its aging resistance.
Long Service Life
The history of use in Europe proves that the material can last at least 20 years. Simulated aging tests also confirm a service life of more than 20 years, far exceeding traditional materials such as metals. Some companies producing pipes from this material claim a service life of 50 years for their products.
Flame Retardant, Smoke-Free, and Non-Toxic
This material is flame retardant, with a flame retardancy rating of FV0 (the highest level for non-metallic materials). In high-temperature burning tests, its smoke generation level is classified as 15 (smoke level ranges from 1 to 100), and the smoke is non-toxic, with a toxicity rating of ZA1 (quasi-safety level 1).
Huayuan(HAMC) provides not only SMC but also SMC molding products.Huayuan was founded in 1994 and located in the hometown of Liangzhu—Gaoqiao, is a FRP professional group company with material production, mold production, and one-stop parts molding. The company has long been committed to productions of SMC BMC materials, SMC BMC molded parts, BMC injection parts molding processing services, SMC/BMC mold design and manufacturing.
The strong scientific, technological strength and R&D capabilities of the Composites can provide customers with SMC BMC composite integrated solutions. The annual production capacity of SMC BMC composite materials reaches 25,000 tons. The SMC and BMC materials produced by the company have passed UL and SGS certifications. FRP products branch has more than 60 SMC BMC professional molding press machine from 100T to 2500T, annual pressing capacity of 5 million pieces, and provides customers with SMC BMC molding products processing services in electrical, automotive, rail transit, construction and other industries.
