Things you need to know about cable laying

Power cables are a large category of electrical products
used to transmit electricity and realize electromagnetic energy conversion.
All industrial production, transportation, construction projects and facilities, modern agriculture and scientific research, military equipment or military facilities, space, ocean exploration and social life are closely related
to cable products.
Do you have a comprehensive and detailed understanding of cable laying? What do we need to pay attention to in cable laying? Below we can understand
from seven aspects.

1 General Provisions

The path selection of the cable should avoid the cable from mechanical external force, overheating, corrosion and other hazards, to ensure that the cable path is the shortest, easy to lay, maintenance, should avoid the place to be excavated construction, oil-filled cable line through the undulating terrain, should ensure the reasonable configuration
of the oil supply device.
The upper and lower left and right changes of the cable in any laying method and all its path conditions should meet the allowable bending radius requirements
of the cable.
The allowable bending radius of the cable should meet the requirements
of cable insulation and its structural characteristics.
For self-capacitant lead-clad oil-filled cables, the allowable bending radius can be calculated
as 20 times the outer diameter of the cable.
If the number of cables in the same channel is large, if it is laid on a multilayer bracket on the same side
.
The configuration of the cable arrangement on the same layer of bracket should comply with the following regulations: the control and signal cables can be close to each other or stacked in multiple layers
.
In addition to the same circuit of the single-core power cable for AC system can adopt a zigzag (three-leaf) configuration, multiple power cables of the important same circuit should not be stacked
.
Except for single-core cables for AC systems, power cables should have a gap
of 1 times the outer diameter of the cable between each other.
The phase sequence configuration and the distance between the phases of the single-core power cable for AC system should meet the normal induced voltage of the metal sheath of the cable at the same time not exceeding the allowable value, and should ensure that the cable cross-section is determined
according to the principle of continuous working current selection.
Single-core power cables that are not arranged in a zigzag configuration, when there are two circuits and more configurations in the same path, mutual influence
should be counted.
When the single-core power cable for the AC system is close to the public communication line, it is advisable to maintain a technically and economically advantageous cable path, and if necessary, the following measures to suppress the induced potential can be taken: the cable bracket forms an electrical path, and the influence of
other parallel cable inhibitors is included.
The reinforced concrete structure of the cable tunnel is welded and connected by steel mesh
.
Parallel metal shield wires or hood boxes, etc.
are appropriately attached along the cable route.

2 When the cable is laid along the pipeline that transports flammable gas in the air, it should be configured on the side of the pipeline with a low degree of danger, and should comply with the following regulations: when the flammable gas is heavier than the air, the cable should be configured above
the pipeline.
When flammable gases are lighter than air, the cable should be arranged under
the pipe.
The cable and its pipes and trenches should be tightly blocked
with non-combustible materials when passing through the walls and plate holes between different areas.
There should be no connectors in the cable route; If joints are used, they must be explosion-proof
.

2.
Laying method selection

The choice of cable laying method should be selected according to the engineering conditions, environmental characteristics, cable type, quantity and other factors, as well as the principle of reliable operation, easy maintenance and technical economic
reasonableness.

3.
Direct burial and laying underground

The path selection of direct buried laying cables should comply with the following regulations: should avoid areas that contain strong acid and alkali corrosion or stray current electrochemical corrosion
.
2) When there is no protective measures, it is advisable to avoid termite hazard areas, heat source influences and areas that are vulnerable to external damage
.

4.
Laying of protective tubes

The inner wall of the cable protection pipe should be smooth and burr-free
.
The selection should meet the mechanical strength and durability required by the conditions of use, and should meet the following regulations: when it is necessary to use a pipe to suppress electrical interference to the control cable, a steel pipe
should be used.
When AC single-core cables are threaded through a single pipe, steel pipes
that are not separated by magnetic circuits shall not be used.

5.
Laying of cable structures

The size of the cable structure should be determined according to all the cables accommodated, and the configuration of the cable should not hinder the safe operation, meet the space required for the work of laying facilities and maintenance patrol activities, and should comply with the following regulations: 1) The net height of the passage in the tunnel should not be less than 1900mm; In local sections of shorter tunnels that cross with other channels, the clear height can be reduced, but should not be less than 1400mm
.
2) The net height of the closed working well should not be less than 1900mm
.
3) The net height of the cable mezzanine chamber shall not be less than 2000mm, but should not be greater than 3000mm
.
The net height of the cable mezzanine of civil buildings can be slightly reduced, but the short-distance space for personnel activities in the cable configuration shall not be less than 1400mm
.

6.
Laying underwater

The selection of underwater cable path should meet the requirements
of cable invulnerability to mechanical damage, reliable protection, convenient laying operation, and economic reasonableness.
Underwater cables must not be suspended in water and should be buried underwater
.
In navigable waterways and other waters that need to prevent external mechanical damage, the cable should be buried in a trench at an appropriate depth under the water, and should be firmly covered and protected; The burial depth of shallow water should not be less than 0.
5m, and the burial depth of deep-water channel should not be less than 2m
.
It is strictly forbidden to cross or overlap
underwater cables.
Adjacent cables should be adequately spaced safely
.
The horizontal distance between the underwater cable and the industrial pipeline should not be less than 50m; When restricted by conditions, it shall not be less than 15m
.
In the section where the underwater cable is led to the shore, protective measures
suitable for the laying conditions should be taken.
On both sides of the underwater cable, conspicuous warning signs
should be installed.

7.
Laying in other utilities

Non-mineral insulated cables used in important wooden building facilities through wooden bridges, docks, planks and other public structures should be laid in
non-combustible protective pipes or trough boxes.
Cables in public facilities such as traffic bridges, tunnels or underground shopping malls should have reliable measures
to prevent cable fire hazards and avoid external damage.
Cables on highways and railway bridges should take measures
to prevent vibration, thermal expansion and contraction and long-term stress fatigue caused by the fracture of the metal sleeve under the influence of wind.

In this way, cable laying is also a huge and complicated project, through the above methods, you can intuitively understand how the cable is successfully
laid.