Why are transformers needed in the national grid?

Answer 1

They step down the voltage from the main power generating stations at different intervals so that for a domestic power service it is delivered at 240V.

Additional answer

When you pass electricity through wires you warm the wires up. This heat is a total loss of energy. So you want to keep the loss to a minimum. The heating effect of electricity is increased with an increase in amperage (the current). The amount of power that goes through the wires is a function of the voltage x amps. So to transmit a certain amount of power with the minimum heat loss you keep the current down which mean pushing the voltage up. This is why the transmission wires near the generating station carry very high volatges. But these voltages are unsafe for use in domestic circuits so they have to be reduced by a series of Transformers from the high voltages in the main lines to lower voltages at substations to even lower voltages in the home.

For more information see the answers to the Related questions shown below.

Answer 2

When you pass electricity through wires you warm the wires up. This heat is a total loss of energy. So you want to keep the loss to a minimum. The heating effect of electricity is increased with an increase in amperage (the current). The amount of power that goes through the wires is a function of the voltage x amps. So to transmit a certain amount of power with the minimum heat loss you keep the current down which mean pushing the voltage up. This is why the transmission wires near the generating station carry very high volatges. But these voltages are unsafe for use in domestic circuits so they have to be reduced by a series of transformers from the high volatges in the main lines to lower voltages at substations to even lower voltages in the home.

Answer 3

Well, the short answer is "to change the voltage", but I'm going to assume you already knew that and you're asking why that's a good thing in the specific case of power lines. It has to do with the transmission characteristics of electricity.

Basically, what it comes down to is that some power is lost in transmitting the electricity through the miles and miles of wire between the power plant and your house. This is actually even worse than a total loss, since some of that power actually causes the lines to heat up, which makes them not conduct as well, so even more power is lost!

It turns out that the power loss is proportional to the resistance of the wire, so we could do a little better by using either better conductors or thicker wire, but that adds to the expense of the wire itself, and also the weight, which means the poles need to be spaced closer together.

However, power loss is also proportional to the current squared. So reducing the current... the amperage, in other words... has a much greater effect. If we can drop the current by a factor of two, we drop loss by a factor of 4. If we can drop the current by a factor of 10, we drop loss by a factor of 100.

So, how do we drop the current but deliver the same power? Power is voltage times amperage, so if we want to cut the amps in half, we can double the voltage and still get the same power. In the case of power lines, it's even better to raise the voltage by a factor of 15, or even 150 in the case of long-distance transmission lines, and therefore drop the current by a huge factor.

There are issues with very high voltages... which is why those long-distance power pylons look different than the regular residential poles. So there will be substations that drop the 200,000V or so used in the long-distance lines back down to say 20,000 for the local lines, and the transformers on the poles drop it down still further so that you don't need 5 feet of glass insulation to keep it from sparking in your house.

(Incidentally, this is why the generators don't just put out a jillion volts in the first place... high voltage is great for sending power long distances, but it's horrible to work with because it takes lots of insulation to keep it from arcing over and becoming, effectively, a giant person-sized bug zapper).

Answer 4

Electrical generators work at about 11,000 volts which is not enough to transmit power over long distances over about 5 miles. Therefore step-up transformers are used to connect them to the local grid on 132 kV or the supergrid on 275 or 400 kV (in the UK)

Answer 5

For systems that require more than one voltage. Also, electricity travels further distances with less loss at higher voltages (more efficient).

Answer

For a given load, the higher the supply voltage, the lower the resulting load current. High voltages are essential in electricity transmission/distribution systems in order to minimise the currents flowing through the lines, otherwise (1) the resulting voltage drops would be enormous, (2) the line conductors would need to have huge cross-sectional areas, and (3) the line losses would be excessive. Without high voltages, electricity transmission would be impossible due to factors (1) and (2).

Answer 6

The higher the voltage used in transmission lines the lower the energy lost caused by the resistance of the wires. See related links.

Answer 7

The role of the transformer in the national grid is to change the voltage. Depending on the type of transformer it can make the voltage higher, or lower.

Answer 8

Loss is I*I*R. If high current is transmitted, there is more loss. We can send the same power by reducing current and step up the voltage. This is only to reduce the transmission loss.

Answer 9

Generating stations, substations, inter ties, service step downs.

Answer 10

i asked the question so why am i being asked to answer the question? *confused*