1. Introduction: With the rapid development of the socio-economy, the types of cables used in power construction have also increased significantly, and construction techniques have become increasingly scientific and sophisticated. As a result, mineral-insulated cables have emerged. In a certain project, this type of cable was extensively used. Compared with conventional cables, both the construction quality and the construction schedule have been greatly improved.

2 Construction Method Features

This type of cable has its own unique characteristics in terms of construction difficulty, methods, and processes. Since the outer sheath of this cable model is drawn from copper tubes of a specific length, both the cable length and the number of conductors are subject to certain limitations, as specifically demonstrated below:

2.1 Since the length of the copper pipe is fixed, the larger the wire core, the greater the outer diameter and the shorter the forming length. The maximum length is around 100 meters.

2.2 Since its outer casing is made by drawing copper tubing, its outer diameter is subject to certain limitations. Therefore, for cables larger than 35 mm² that do not have five cores, only a combination of one four-core cable and one single-core cable can be used.

2.3 Therefore, the cable is entirely made of copper and minerals, both of which are non-combustible materials. Moreover, it has relatively high strength, allowing it to be directly laid openly on supports.

2.4 Its inherent non-combustibility and mineral-based, pollution-free nature ensure that it does not produce any harmful gases or secondary pollution whatsoever. In fact, it can truly be described as an environmentally friendly, green product.

2.5 Long service life: Mineral materials are high-temperature resistant and not easily aged.

3 Laying Methods and Transportation

3.1 Laying Method

Compared to plastic-insulated cables, mineral-insulated cables can be installed using the following installation methods:

1. Secured along the bracket

When cables are secured to supports, it is required that each support be equipped with cable clamps to ensure proper fixation. In certain applications, the angle steel brackets used for fixing must take into account their fire resistance rating.

2. Install along walls and ceilings

During installation, the mineral-insulated cable must first be straightened and then securely fixed to the wall or ceiling. Once installed, the cable should appear neat and aesthetically pleasing, and its fixing intervals must comply with the specified requirements. At bends, the cable’s bending radius must meet the prescribed standards, and cable clips should be used to secure the cable 100 mm on either side of the bend.

When cables of various specifications are laid simultaneously, the bending radius of each cable shall be determined based on the bending radius of the cable with the largest diameter, and the cables shall be laid neatly and uniformly.

3. Installed concealed within walls

Grooves must be chiseled into the walls before the cables are laid and secured. Once the cables have been installed and passed the insulation test, crack-resistant plaster should be applied immediately to protect the cables from damage. This same method can also be used for concealed cable installation on ceiling slabs; however, during groove-chiseling, care must be taken not to compromise the structural integrity of the building.

To secure cables inside walls, you can use expansion bolts embedded in the wall and fasten the cables with cable clips.

When the cable-laying route crosses rivers, lakes, or other bodies of water, mineral-insulated cables can also be laid underwater to enable passage across rivers, streams, and lakes.

When laying cables, operations must be carried out strictly in accordance with the requirements of the construction specifications to meet national acceptance standards and ensure that the installation is economical, practical, and aesthetically pleasing.

3.2 On-site Transportation

During on-site construction, mineral-insulated cables can be handled manually. Since the production of mineral-insulated cables is constrained by raw materials, their length cannot be as long as that of other types of cables. For cables with smaller cross sections, longer lengths are possible; however, for cables with larger cross sections, the maximum length is only a few tens of meters. Consequently, these cables are not very heavy—indeed, even the heaviest cable reel weighs only about 150 kilograms. With just three or four people, it’s entirely feasible to move such cables anywhere on the job site.

Of course, if site conditions permit and the handling equipment is available, mechanical handling is also an option. However, during handling, proper protection of the cables should be ensured to prevent damage.

4 Construction Preparation

4.1 Material Preparation

1. Copper clips for cable binding, or copper and iron binding wires.

2. After the cables have been laid, cable nameplates should be hung at both ends of each cable. The nameplates should indicate the cable model, specifications, length, as well as the starting and ending points and the month and year of installation, for future reference. Therefore, all types of nameplates must be prepared in advance.

3. Supporting attachments

Mineral-insulated cable accessories include four categories: installation accessories, intermediate connection accessories, termination accessories, and sealed insulation accessories.

Installation accessories mainly include cable clamps for securing cables and cable hooks used in overhead installations. Cable clamps can be either standard clamps designed for fixing other cables, or copper clamps, or plastic-coated copper wires and iron wires used for tying and securing cables. Copper clamps are made from flat copper strips, with thicknesses ranging from 1 to 2 mm depending on the cross-sectional size of the cable; they can be supplied as a complete set by cable manufacturers or can be manufactured independently. The number of installation accessories required can be estimated based on the cable spacing and the method of cable fixation.

The intermediate connection accessories are used for splicing cables at intermediate points, and their specifications should be selected according to the specifications of the mineral-insulated cables being used. For a given circuit with several intermediate joints, the number of intermediate connection accessory sets required will correspond to the number of intermediate joints.

Terminal accessories are used for connecting and securing both ends of the cable, and their specifications should also be selected according to the specifications of the mineral-insulated cable being used. Each circuit requires two sets of terminal accessories.