Why do High Voltage Transmission lines have three lines??
111070
High voltage transmission lines have three line (sometimes two sets of three lines) because they supply three-phase electicity.  The high voltage is reduced in transformers to supply houses.  Houses usually receive power from two of the three phases and the loads on the three phases must be balanced say within a given neighborhood.  Any one phase to ground will supply 110V AC for example to light a light bulb.  The two phases supply 220V AC for clothes dryers and electric ranges and perhaps a central A/C system.  A machine shop with large motors would use all three phases which supply 440V AV.\n\nElectricity can often be compared with the flow of water where pressure is like voltage and current is like flow rate.  For the original old DC electric systems, the generator was like a pump that pushed water through a single line passing it through a light bulb and into the water table (ground).  For a single phase AC system the generator is like a pump the pushes a spurt of water to the house through the light bulb into the ground than sucks a spurt in the reverse direction back to the pump, 60 times a second.  A three phase system is like having three separate water piston pumps on the same shaft that discharge one after the other into three separate lines at 60 spurt cycles a second each.  Obviously the power will depend on the pressure (voltage) and the number of phases (lines) connected to a load.  In addition to the three wires in a three-phase system, there is also a forth wire that ensures a very good connection with the ground (a ground wire).  Both the generator and the house system must be well grounded.  Hope that helps a little.  BTW, a high voltage system often has a fourth wire on top for lightning strikes.
817738
I think you've mis-stated your question.\n\nLIGHTNING ARRESTOR - A protective device that provides a very low resistance path to any voltage above its rated value. \n\nIn effect, a lightning arrestor will protect the phase of the device wiring *and, subsequently the device itself) immediately downstream (away from the strike). A 3-phase machine will require 3 arrestors, one per phase.
92400
Usually a delt system is compared with a "Y" (wye) system.  A delta is a Greek letter often represented as a three-sided triangle and a Y is a letter with three members (two arms and one leg).  The important feature is threeness.\n\nElectrical power is supplied in three phases (single-phase, two-phase and three-phase) involving voltages of 110, 220 and 440 Volts, respectively.  Single phase is used for light bulbs, two-phase is used for heaters (such as clothes dryers and kitchen ranges) and three phase is used for very large motors.  Alternating current (AC) forms a sinusoid and in three-phase current the sinusoids are out of phase (reaching peak voltages at different times (but 60 times per second each) and this delivers high voltage and maximum power.\n\nThere are two common methods of winding transformers and motors to take advantage of three-phase current and these are referred to as "delta windings" and "Y-windings."  For purposes of circuit analysis they are equivalent.
93370
Under average conditions a power line carries current to \nan appliance designed for the voltage . Cross country power lines operate for supply to cities at very high voltages and if dropped into the salt water would complete the circuit to ground overloading the circuit causing a circut breaker to disconnect .if the breaker fails the \n"short circuit" would overload the supply equipment and\nburn it out. The ultimate breaker may also be a fuse.
1117712
switch Line 1 and 3. this is the industrial stander. you can also switch any of the two line but you should only do L1 and L3
80787
it shouldnt mater that much, 3 phase power fires one after another, if all three have the same voltage, amperage, and Hz. the only thing, that i can think of, is to make sure that they are cycling in order. DO NOT CONECT TO MOTOR, if the motor is conected and the wires are conected in the improper order, it will not run backwards, it will cause severe damage, as far as i know. runing backwards would only work in 2 Phase power, Maby. Be carefull when using multi-meters with 3 Phase power, i read on my meter that that source can be unpredictable and very dangerous. A good meter and good judgement can do a lot of help in this situation. I think that if you just guess and hook them all up, and be ready to turn it off quickly, then if it is incorect you just switch your b and c wires and it should work. if you have a meter i think that some power setups have the a and b lines at 115vac and c is higher, MABY! i do not know for sure how to discover for sure what they are, but i dont think that ossiliscopes are the corect tool for the job. good luck
691721
Electric field lines are a convenient way to sketch an electric field, but in real life, the field is continuous and exists in every direction.\n\nThe lines do not cut each other because they join points of equal field strength, like isobars on a weather map or contour lines on a relief map.\n\nThe lines will never cross because each line represents a specific value, and field strength decreases steadily as you move away from the source.  Crossing lines would mean that there is a point where the field strength is two values at the same time, which is obviously impossible.
315912
Other than direct discharges from lightning, fluctuations in the magnetic field can generate currents in the electrical grid.  This happens as a result of solar activity such as solar wind and flares bombarding the Earth's magnetic field causing it to flex.\n\nLong distance transmission lines are especially vulnerable to this as their length is enough to act as a generator from the magnetic changes.  Grids can shut down and transformers have been melted  due to power surges generated by strong solar storms.
509021
"The audible noise emitted from high-voltage lines is caused by the discharge of energy that occurs when the electrical field strength on the conductor surface is greater than the 'breakdown strength' (the field intensity necessary to start a flow of electric current) of the air surrounding the conductor. This discharge is also responsible for radio noise, a visible glow of light near the conductor, an energy loss known as corona loss and other phenomena associated with high-voltage lines.
36968
Electric distribution uses the ground as a return leg of the circuit.  The voltage in your house, or in overhead lines, is held at a voltage above ground.  So you are completing a circuit.
831085
"Three-phase electrical generation is very common. Three separate coils in the generator stator are physically offset by an angle of 120° to each other. Three current waveforms are produced that are equal in magnitude and 120° out of phase to each other."\n\nFrom Wikipedia, the free, online encyclopedia at:\nhttp://en.wikipedia.org/wiki/Alternating_current\n\nMore on three-phase on Wikipedia at:\nhttp://en.wikipedia.org/wiki/Three_phase\n\nFurther links are available on both pages...\n\nHope this helps!
295646
Receiving end voltage being greater than sending end voltage in a transmission line is known as ferranti effect. All electrical loads are inductive in nature and hence they consume lot of reactive power from the transmission lines. Hence there is voltage drop in the lines. Capacitors which supply reactive power are connected parallel to the transmission lines at the receiving end so as to compensate the reactive power consumed by the inductive loads. As the inductive load increases more of the capacitors are connected parallel via electronic switching. Thus reactive power consumed by inductive loads is supplied by the capacitors thereby reducing the consumption of reactive power from trans line. However when the inductive loads are switched off the capacitors may still be in ON condition. The reactive power supplied by the capacitors add on to the transmission lines due to the absence of inductance. As a result voltage at the receiving end or consumer end increases and is more than the voltage at the supply end.This is known as ferranti effect.
24264
Electric current flows between two points, if the points have different potentials. When a bird touches a wire, the bird will have the same potential as the wire.\n\nIf the bird reaches two wires at the same time, there can be different potentials, so the bird can be 'electrocuted'. That's why the wires need to be far enough from each other.\n\nIf somebody reaches the wire and the ground at the same time, there can also be different potentials... That's why the wires need to be far enough from the ground.
283243
Try here:\n\nhttp://en.wikipedia.org/wiki/Overhead_lines\n\nHope this helps
694070
because it's not referenced to ground to begin with.\nbut if you have a wye to delta transformer then the wye transformer will be referenced to ground (center tap).\n\nDelta transformers are for more of the industrial (large 3 phase motors) application anyway.  hence there really is no need to reference it to ground.
431144
The only reason you get shocked when you touch one phase and ground in the commercial power distribution system is because the commercial power distribution system uses a grounded system where the earth itself is used instead of a wire.  Commercial power distribution I believe (and I may be wrong on this) uses Wye (pronounced "Y") connected three phase power with the center grounded allowing the earth itself to be used in place of the fourth wire.  In a balanced 3-phase system (all loads draw the same amount of power from all three phases) the center is not required, but few people have three phase blenders, so only a single phase of the power is sent to an outlet along with the neutral which is grounded.  If you look at Naval electrical distribution systems, they are ungrounded.  Navy schools teach that the use of an ungrounded system raises reliability because two faults to ground on two different phases are required to disable the electrical distribution system, and that in ideal conditions one can touch a single phase and ground and not be shocked.  Berkeley challenges this and I have included a link to their web sight.  I believe the truth is somewhere in the middle because I have touched a single phase and ground and been shocked.  It was a 440V wire, and I definitely felt it, but it was not nearly as sever as being shocked by an outlet (115V) so ungrounded reduced the severity, but did not eliminate the shock.  The electricity that I felt was probably from capacitance in the insulation.  To any one who cares, I managed to shock myself while removing a dead front fuse.  Dead front fuses are "idiot proof", but you know what happens every time they make something that is "idiot proof"?  They make a better idiot to go with it.  (:
927155
The addition of a neutral wire with a three phase electrical supply allows a lower voltage, single phase sub-assembly or appliance to be powered by the same line in (one phase to neutral).\nThree phase alone merely conducts between phases.