Transformers Movie Info

How are transformers used in power stations?

How are they used in power stations? I know they are used for changing voltage from one circuit to another and I know power stations have 'step up' transformers but how exactly are they used? Do they need to increase the voltage for the national grid for some reason? And do they have any step down transformers? I dont know if all power stations are the same but this is for a gas power station that uses big turbines. Any help greatly appreciated

Public Comments

1. i think that the generators create dc voltage and therefore a transformer is used to convert it to 3 phase ac voltage.


2. Step-up transformer: Electricity loses some of its energy as it travels down wire cables, but high-voltage electricity loses less energy than low-voltage electricity. So the electricity generated in the plant is stepped-up (boosted) to a very high voltage as it leaves the power plant.

   Step-down transformer: Once the electricity reaches its destination, another transformer converts the electricity back to a lower voltage safe for homes to use.

   edit:

   http://www.explainthatstuff.com/transformers.html

   simple explenation of transformers and there uses hope it helps..



3. P = EI (Power = Voltage x Current). If you wish to transmit a given amount of electrical power (kwh kilowatt-hours) you have a choice (using transformers) of having very high current or very high voltage. High current means a high flow rate of electrons and that means a very large (copper or aluminum) cable must be used (actually three cables for three-phase power supplies). Using high voltage instead reduces the amount (and weight) of metal conductor required. The strength of high tension towers and insulators can also be reduced. Generally the voltage selected is a matter of engineering and economics. The less power wasted heating the transmission cables the less fuel must be consumed (and the less greenhouse gases, mercury and acids will be released).


4. Optimus Prime is responsible for turning the turbines. Megatron works the water coolers.


5. Within a power station the Generators produce electricity at a set voltage. The voltage is normally of a range that is efficient for industrial purposes.

   This voltage is often in the 4KV to 6 KV range. This varies from jurisdiction to jurisdiction. But the details don't matter.

   The station will use some of this energy to run the service equipment for the station. Some of this equipment will use energy in the same value as the produced energy but usually it will be at a higher or lower voltage. Transformers will be used to raise the voltage to as high as 33,000 volts for some equipment or to as low as 120 volts for lights etc.

   The station will also produce energy for distribution to the Grid. Thus step up transformers will be used to increase the voltage to whatever the grid voltage might be. In Ontario Canada for instance this grid voltage could be any of 45,600 volts, 115,000 volts, 230,000 volts or 500,000 volts.

   The higher voltages are used for longer transmission distances. Losses in line voltages are inversely proportional to voltage. That is losses are greater for lower voltages. Thus there is advantage to transmission at higher voltages.



6. Many large power stations are operating alternating current generators.Almost all power stations are stepping up generated voltages to higher voltages for transmission to distant load centers.Power stations are also provided with automatic capacitor contactors for increasing MVARs in a station.


7. Power stations generate electricity using 3 phase generators, this is then fed to a three phase step up transformer to 33kv (it used to be 132kv but now is 33kv) this is for the convenience of transmission of the power overland. When it reaches the area it is required by the consumer it is then fed to 3 phase step down transformers to 440v. Industry normally use 3 phase, but for domestic use each of the phases(Red,Yellow or blue) are distributed to separate streets at 240v, this being the result of 1 phase and neutral. ( The supply generator would be grounded via its outer casing which would be the consumers earth or neutral


8. A power station will have three categories of power transformer:

   generator transformer

   unit transformer

   station transformer

   The generator transformer is three phase and is connected to the output terminals of the power station generator. There is a transformer for every generator at a power station. The voltage is stepped up from typically 22.5kV to 400kV in the UK. Sometimes it is only stepped up to 275kV depending on the surrounding grid network. The voltage is stepped up at a power station to increase the voltage and this is done to reduce the current. (Np/Ns = Vp/Vs = Is/Ip i.e. inversley proportional to current).

   Reducing the current reduces the I^R losses during transmission.

   The number of generator transformers depends on the number of units. Not all power stations are the same. A coal, nuclear or oil power station might have x number of units, therefore x number of steam turbines and hence x number of generators and x number of transformers connected to the grid.

   A CCGT site is less straight forward. For example you might have a 2+1 arrangement i.e. two GTs running 2 generators, plus 1 HRSG running one generator via a steam turbine. Therefore for one unit of a CCGT you could have three generator transformers. If the CCGT is a 2 x 2 + 1 arrangement it will have two units as described above therefore six generators and six generator transformers.

   The other category of transformer I mentioned above i.e. unit and station are used in a power station to feed the auxiliary supplies i.e. power is taken off the grid to start up some pumps etc and these are the step-down transformers you mentioned. It's a complicated distribition system but amongst other things it gives the station flexibility to bypass supplies during run-up for routine maintenance etc.