What precautions should be taken when installing cable distribution boxes?

Precautions for Cable Branch Box Installation

Cable branch boxes are a crucial component of the entire power supply network. They directly impact the normal operation of the entire power distribution system. Relevant departments and units should pay close attention to this and be familiar with the key technical considerations during the installation process. Only in this way can the operation and protection of cable branch boxes be handled with confidence, ensuring the safe and stable operation of the entire power distribution system. In the technologically advanced 21st century, cable branch boxes have largely entered the ranks of obsolete products, as they are older products, primarily air-insulated using heat-shrinkable materials.

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The modern use of cable distribution boxes is severely restricted. Their outer protective material is common rubber, which makes exposed ends prone to cracking during operation, and internal interfaces easily separate, leading to a decrease in the insulation of the entire line, which is extremely dangerous.

Distribution boxes primarily made of EPDM rubber are problematic. This rubber is relatively hard, and more importantly, it is highly flammable at high temperatures, easily causing what is known in electrical circuits as "creepage and arcing." Secondly, this material is prone to aging, not moisture-proof, and does not meet the requirements for long-term use. Not to mention, this rubber material itself is a toxic substance, causing irreparable environmental pollution.

Using silicone as the primary material, however, is highly advantageous. It is not only softer but also highly elastic, providing complete insulation. It is also effectively waterproof and moisture-proof in rain and snow, does not easily age, and is resistant to corona discharge. Most importantly, it does not require long-term maintenance, saving repair personnel a lot of future work.

It is a branch box with SF6 load breaking function. It can achieve the effect of a ring main unit. However, its price is much lower than that of a ring main unit. Moreover, it is very convenient for future repair and maintenance, and plays a great role in areas where it is inconvenient to install a power distribution room.

 

Differences between the two types of connectors (live contact and non-live contact)

 

Live contact connectors and non-live contact connectors differ significantly. The most important difference is that live contact connectors are silicone rubber connectors without an internal semiconductor insulating layer. However, they have an external conductive insulating layer and use a clamp grounding method. Non-live contact connectors, although also silicone rubber connectors, have a zero grounding voltage in practical measurements. However, they are prone to generating induced static electricity during practical use. Substations often operate in multi-circuit processes. If testing one circuit is required while nearby circuits are being energized, live contact cable connectors should be used.

Cable branch boxes present some problems during use. For example, these branch boxes are protection-free products. Therefore, no maintenance or protection secondary circuits are needed within the branch box. The outer casing of this type of branch box has an IP33 protection rating, and the exterior of the box is completely grounded. When working with a branch box under live conditions, its casing must not be opened, eliminating any possibility of live contact with the cable joints inside. In the event of an irresistible external force, such as a collision with a car, the function of both types of contact joints is the same. Therefore, under the same external conditions, in terms of operational reliability, non-live contact joints are more reliable and also have a lower price. Therefore, choosing non-live contact joints is more reasonable.

 

Precautions for the Installation and Operation of Cable Branch Boxes

 

♦Installation Conditions and Precautions

Currently, there are many types of outdoor cable branch boxes in my country. Therefore, their safety installation is extremely important. Construction personnel must ensure: correct installation of joints, proper installation process, orderly assembly of joints, and operation according to the manufacturer's provided installation instructions. Only by doing so can the cable branch box be used and operated normally.

♦Advantages of Using Cable Branch Boxes in Lines

The above examples illustrate the following advantages of using cable branches: they have adjusted previous line planning considerations, are not affected by geographical structures, and have opened up a new era; they are convenient to install even in areas with difficult line corridors, improving power supply efficiency and providing a better social environment; their functions are comprehensive and excellent, making a significant contribution to optimizing the network environment technically; although the investment is relatively large, it can reduce safety hazards and provide higher economic and social benefits; it also greatly improves work efficiency.

♦Conditions for Use and Related Precautions

Before formal operation, the grounding wires of different branch cables must be securely connected to the box. The box casing should also be effectively connected to the grounding grid. After installation, the cables and components should be tested according to relevant regulations.

 

Common Defects and Solutions

 

In my country, cable distribution boxes have experienced numerous defects. The primary causes and corresponding solutions for these defects are as follows:

♦Inadequate Installation Techniques

In fact, most defects are due to poor contact between the stress cone of the T-joint and the cable joint. Inspection reveals that even after some distribution boxes have been put into operation, many problems remain, with some stress cones partially collapsed. During installation, it is often found that the cable branch joints are relatively short, generally only about 0.5m. This damages the stress cone, leading to safety hazards. Therefore, the cable branch joints should be lengthened to about 1m to ensure proper installation of the T-joint.

♦Construction Problems During Branch Box Foundation Installation

Some municipal companies responsible for manufacturing cable distribution boxes tend to... The branch box was added according to the owner's own ideas, and the construction was not strictly in accordance with the drawings. Its width and depth are often less than required by the drawings. Currently, many backbone cables use large-scale cables. If the foundation is not up to standard, the bending radius of the cable may not be large enough, leading to problems with the vertical placement of the cable, making it impossible to secure the steel trough supporting the cable, causing the T-joint to be damaged by forces from both the lateral and longitudinal directions.

♦Cable Branch Box Moisture

Some cable branch boxes lack an insulating base plate at the bottom. This makes them prone to moisture absorption in moderately humid areas or during rainy or snowy weather, which can reduce insulation and cause short circuits. Sometimes, this can even render the entire cable branch box unusable.

 

Summary

The accelerating pace of urbanization has inevitably led to some conflicts between the planned routes of cable distribution boxes and the development of townships. Therefore, in order to adapt to the demands of social development and to ensure a safer and more stable power supply, it is necessary to adopt cable lines for power supply in townships, and to relocate cable distribution boxes to the future power distribution systems of townships.

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