Understanding Power Dissipation in Transmission Lines

In summary, when high voltages are used for power transmission, the power dissipated through resistance is reduced due to voltage division. However, current must also be minimized to reduce losses, as the R in i^2R represents the resistance of the conductors. On the other hand, v^2/R losses are related to the conductance between the conductors, which is minimal in dry weather but can increase in wet conditions.
  • #1
miss photon
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how does a transformer work?
 
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http://en.wikipedia.org/wiki/Transformer" [Broken] for an explanation of working and principles. In future, for complete explanation of concepts, start with your textbook or look for online resources.
 
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  • #3
Wow, sometimes Wickepedia gives really good explanations!
 
  • #4
arunbg said:
http://en.wikipedia.org/wiki/Transformer" [Broken] for an explanation of working and principles. In future, for complete explanation of concepts, start with your textbook or look for online resources.

hey, thanks for the link. but i still have a doubt. for transmission of power, high voltages are used so as to reduce current in the wires. then power dissipation thru resistance would be i^2*R.but it can also be written as v^2/R. so what's the actual difference bwtn power supplied and power dissipated?
 
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  • #5
miss photon said:
hey, thanks for the link. but i still have a doubt. for transmission of power, high voltages are used so as to reduce current in the wires. then power dissipation thru resistance would be i^2*R.but it can also be written as v^2/R. so what's the actual difference bwtn power supplied and power dissipated?
First thing you have to know is that P = v^2/r, where 'v' is voltage dropped across the resistive load. Internal resistances across a high voltage power line tend to be small compared to the main load, and hence voltage dropped across them is far smaller. This becomes even smaller with higher voltages. Therefore 'v' becomes small and hence power dissipated is low. Note that this 'v' is not the entire voltage of the power line, but merely a small fraction of it. This is called voltage division.
In the case of current however, no such division takes place in the power lines and in P=i^2r, 'i' actually stands for the total current in the lines. Thus the current has to be minimized to reduce loss.
 
  • #6
miss photon said:
hey, thanks for the link. but i still have a doubt. for transmission of power, high voltages are used so as to reduce current in the wires. then power dissipation thru resistance would be i^2*R.but it can also be written as v^2/R. so what's the actual difference bwtn power supplied and power dissipated?

the "R" in i2R losses in transmission lines is the resistance of the actual conductors that the current flows through. a v2/R should be more consisely called v2G losses and G would refer to the conductance between the conductors. i don't know what it's like around a high tension transmission line when it's raining or drizzling or misting or foggy (there might be some measurable inter-cable conductance or leakage, but when it's dry, that conductance, G, is pretty much 0. however, you have i2R losses all of the time, dry or not, because although air makes a pretty good insulator when it's dry, the conductivity of the cables is no better in dry weather than in wet.
 

1. What is a transformer?

A transformer is an electrical device that is used to transfer electrical energy from one circuit to another through the principle of electromagnetic induction. It consists of two or more coils of wire, called windings, that are wound around a laminated iron core.

2. How does a transformer work?

A transformer works by using the principle of electromagnetic induction. When an alternating current (AC) flows through the primary winding, it creates a changing magnetic field around the iron core. This changing magnetic field then induces a current in the secondary winding, which is connected to a different circuit. This allows the transfer of electrical energy from the primary circuit to the secondary circuit.

3. What are the two types of transformers?

The two main types of transformers are step-up transformers and step-down transformers. A step-up transformer increases the voltage from the primary circuit to the secondary circuit, while a step-down transformer decreases the voltage. Transformers can also be categorized as either single-phase or three-phase, depending on the number of input and output windings.

4. What are the main components of a transformer?

The main components of a transformer include the primary and secondary windings, the iron core, and the insulation between the windings and core. The primary winding is connected to the source of electrical energy, while the secondary winding is connected to the load. The iron core is used to concentrate the magnetic field and improve the efficiency of the transformer.

5. What is the efficiency of a transformer?

The efficiency of a transformer is the ratio of output power to input power, expressed as a percentage. In an ideal transformer, the efficiency would be 100%, meaning all the electrical energy from the primary circuit is transferred to the secondary circuit without any losses. In real transformers, there are energy losses due to factors such as resistance in the windings and hysteresis in the core, leading to an efficiency of around 95-98%.

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