they are made of alluminium
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.
Much of the newer overhead cables is made of aluminum with steel reinforcing it for strenght purposes. Aluminimum is much cheap, and much lighter, thus it is cheaper to use vs. copper for high voltage transmission, and copper has a lower resistance which means more electricity can get through the wire/ cable, which means more electricity can get around the world quicker. most people should use copper becasue it has a lower resistance where aluminuim has a bit of a high resistance not to much but a bit so that is why you use copper not alominuim.
cables get hot because they have too much current running through them. heating wires are made to run hot. cables are not. get larger wire
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.
because of heat cables expand
beacuse is good
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!
A bridge with overhead cables to support it.
power cables under ground rather then overhead.
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.
Transmission cables are made of conductors and insulating material covering that conductor.
by power lines comuters fridgeyourater cell phone battery
Much of the newer overhead cables is made of aluminum with steel reinforcing it for strenght purposes. Aluminimum is much cheap, and much lighter, thus it is cheaper to use vs. copper for high voltage transmission, and copper has a lower resistance which means more electricity can get through the wire/ cable, which means more electricity can get around the world quicker. most people should use copper becasue it has a lower resistance where aluminuim has a bit of a high resistance not to much but a bit so that is why you use copper not alominuim.
By overhead cables, supported on masts, at very high voltage, to reduce the effects of resistance in the wires.
Many early telegraph cables were made of iron wire, but all modern ones are copper.
VGA cables are cables which are used with computer electronics. The cables are primarily used to connect the monitor to the computer. Some of these cables are made for specific monitors or devices.
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.