Underground wiring refers to cables installed and buried under the ground. These cables which give electrical power and communications are covered underground rather than suspended overhead as aerial cables several meters aboveground. Big town areas with tall buildings often need underground wiring, as underground cables are less exposed and therefore not so dangerous than overhead cables, as well as less of an eyesore.
An underground cabling consists of one or more conductors that have high conductivity, such as copper which can withstand high voltage, or aluminium. This will make up the main part of the cable. Covering the main is a layer of insulation that helps to avoid leakage and ensures a high- degree of safety.
It is usually used in such location as urban areas where overhead line rights of way are not available. Near airports and other location where overhead lines may endanger lives, and in scenic areas where appearance is an important consideration.
The underground cables have more advantages than the overhead lines; they have less voltage drops, small chances of developing faults and have small maintenance costs. However, they are more costly to manufacture, and their cost may vary depending on the construction as well as the voltage rating.
Types of underground cables
The underground cables are defined by two ways; by the voltage capacity, or by the construction.
By Voltage
LT cables: Low-tension cables with a highest capacity of 1000 V
HT Cables: High-tension cables with a highest of 11KV
ST cables: Super-tension cables with a rating of those 22 KV and 33 KV
EHT cables: Extra high-tension cables with a rating of those 33 KV and 66 KV
Extra super voltage cables: with highest voltage ratings beyond 132 KV
By Construction
Belted cables: Highest voltage of 11KVA
Screened cables: Highest voltage of 66 KVA
Pressure cables: Highest voltage of more than 66KVA
Advantages
There are too many benefits in underground wires more than aerial cables. Overhead power and communications lines take up a lot of space, as they need poles to gives them overground and because the cables take up space by buildings and trees.
Underground wires are famous in densely located areas where space is small. Additionally, when installed underground, cables require a small band of land than aerial cables would need.
Underground cabling require a smaller surrounding strip of about 1–10 meters to install (up to 30 m for 400 kV cables during the work), whereas an overhead wires requires a surrounding strip of about 20–200 meters wide to be kept permanently clear for safety, alimony and repair.
Underground cables can’t be damaged by human activity like in can’t damage by accident or can’t be theft that’s why it more secure.
Underground cables will not give harm to low-flying aircraft or to wildlife.
It is less dangerous than ariel power lines and it is wild friendly.
Its maintenance is low
It has small voltage drops
Less faults
Not damaged or to shaking and shorting due to vibrations, wind, accidents, etc.
Very difficult to steal, make illegal connections or sabotage
No harm or danger to wildlife or low flying aircraft.
Disadvantages
Very much Costly.
Difficult in choose and mend broken wires.
Broken to wires or electrocution can bother to people digging the ground and if they are unaware of the wires’s existence.
Laying Of Underground Cables
Underground cabling are, of course, implied to be installed or establish under the ground. The safety of underground cable network mostly bet on upon proper laying of wire, quality of cable common and branch connections etc. There are three types of methods laying underground cables, those are - (1) direct laying, (2) draw-in system and (3) solid system. These all methods are explained below.
Direct Laying Of Underground Cables
This method is the mostly famous because it is simple and cheap. The wires to be undergrounded by using this method should have the serving of bituminised paper and hessian tape that because to provide safety against corrosion and electrolysis.
Draw-In System
In this method, cast iron or concrete pipes or ducts are hidden underground with draining at perfect positions with the wire route. The wires are then get into the pipes from the drain.
Solid System
For this method, the cable is ungrounded by troughing of cast iron, stoneware, asphalt or treated wood. If the cable is underground into the position, the troughing is premeated with a bituminous of asphaltic combo and then hidden over.
Summar
Underground wires are suitable for places where it is hard to use overhead lines due to barriers and dangers presented by the overhead lines. There are so many types of cables mostly planning to handle a big range of voltages. All of the cable type has its advantages as well as disadvantages. However, all advantages of underground cables outweigh their disadvantages.
コメント