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It's cheaper to put wires in the air than underground, generally. The figure I've heard is it is ~10x more expensive to bury (and get an equivalent - buried conductor must be larger for the same ampacity since cooling is negatively impacted) vs. put wires in the air; this will vary depending on voltage level and loading, obviously.
Wiki User
∙ 12y ago
Wiki User
∙ 10y agoIf you are referring to the primary voltage wires that are on top of utility poles the voltage is extremely high as compared to everyday working voltages. Everyday working voltages are dangerous, high voltages even more so. If you inadvertently come into contact with them and you are grounded it could ruin a perfectly good day.
Wiki User
∙ 10y agoAluminium is usually preferred over copper. Although thicker conductors are needed, they are lighter and require less-expensive supporting structures.
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Advantages and disadvantages of underground and overhead cables?
Overhead transmission lines are less expensive, in most cases, significantly less expensive, than underground cables. Underground transmission cables require insulation, cooling systems, and -the most expensive feature- excavation!
What is underground power transmission?
power cables under ground rather then overhead.
What is expected life span of high voltage underground cables?
10yrs
How do you design an 11kv underground cable?
It is not necessary to design an 11 kv underground cable. There are several 11 kv underground cables already on the market. You can choose exactly which cable will fit best for your project and purchase it.
How capacitance effects are taken into account in transmission lines?
Natural capacitance exists between conductors at different potentials, including between those conductors and earth (ground). The value of such capacitance is significantly higher with underground cables than with overhead lines, due to the close proximity of the individual conductors in an underground cable. Capacitance results in line losses in both a.c. overhead and underground systems, due to the corresponding capacitive reactance (opposition to a.c.). In the case of long, high-voltage, underground or under-sea cables, the capacitance losses can be so high that d.c. transmission is used instead of a.c. (d.c. eliminates capacitive line losses). In addition to the line losses, the electric fields resulting from the capacitance can lead to insulation breakdown -making it essential that 'sharp corners', etc., are avoided in their design and construction. One of the reasons that high-voltage overhead conductors are 'bundled' (i.e. more than one conductor per line) is to reduce the stress on individual line conductors that would otherwise occur due to their relatively small diameters.
Advantages and disadvantages of underground and overhead cables?
Overhead transmission lines are less expensive, in most cases, significantly less expensive, than underground cables. Underground transmission cables require insulation, cooling systems, and -the most expensive feature- excavation!
What is underground power transmission?
power cables under ground rather then overhead.
Why overhead lines are far cheaper than underground cables for long distances and less economical for short distances?
First of all, the overhead lines are cheaper because they are bare, while underground cables are armoured and insulated, hence explaining the higher price. Overhead cables come of course with accessories like poles and insulators (mostly porcelain). For shorter distance, underground cables are preferred as the cost of pole erection does not exist.It's also worth pointing out that the cost of excavating a trench is more expensive than erecting an overhead line, and this cost escalates dramatically with higher voltage systems. For example, a 132-kV double-circuit underground line is between 5 and 8 times the cost of an overhead tower line, whereas an 11-kV single-circuit underground line is up to twice the cost of a wooden-pole overhead line.
How does electricity travels to your homes?
by power lines comuters fridgeyourater cell phone battery
Why are the cables of the national grid are above the ground and not buried underground?
undergroud cables would be: -much more expensive -much more difficult to repair -difficult to bury where they cross canals, rivers and roads. also, overhead cables are high above the ground, underground cables could affect people more because the cales wouldn't be very deep
Difference between overhead cables and under ground cables?
The principle difference between underground and overhead cable is thermal dissipation. With overhead cable, heat can dissipate into the air, and wind can improve the rate of thermal dissipation. On the other hand, overhead cable is exposed to solar gain that will result in some heating. With underground cable, heat dissipation is governed by the thermal conductivity of the soil. The Neher-McGrath formulas can be used to calculate thermal conductivity and the required derating of conductors. Comparing the two, an overhead cable generally has a higher thermal ampacity than an underground cable of the same material, dimensions and insulation.
What are overhead cables made of?
they are made of alluminium
What is the cable size that are used in 11kv system?
It depends on the power rating of the circuit but a common size would be 95 sq. mm up to about twice that. 11 kV systems are usually 3-phase 3-wire. Underground cables use copper while overhead ones tend to use uninsulated aluminium or aluminium conductor steel reinforced (ACSR) cables.
What happens to national grid cables in built up areas?
The cables are undergrounded in built up areas. The reason they're left as pilons where there is space for them is because it is cheaper to build, quicker to spot a fault and easier to maintain. Underground cables cost around twenty times as much as overhead cables, but are necessary in cities and built up areas.
Why are wires hung loosely in summer?
beacuse is good
What is the definition of suspension bridge?
A bridge with overhead cables to support it.
What are the dangers present when doing electrical work?
There are many dangers present when doing electrical work including overhead power cables and electrical wires which are obvious and then there are the less obvious ones like cables underground and loose live wires. It is advisable not to do electrical work if you are not a trained professional.
