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13.6 Power Plants and the Electrical Grid

13.6 Power Plants and the Electrical Grid. Transmission Efficiency and Current. Power is lost in a transmission wire To solve for lost power P=VI P=(IR)(I) P =

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13.6 Power Plants and the Electrical Grid

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  1. 13.6 Power Plants and the Electrical Grid

  2. Transmission Efficiency and Current • Power is lost in a transmission wire • To solve for lost power P=VI P=(IR)(I) P = Assume a generator produces 300MW of power at a current of 30kA, which travels through transmission wire with resistance of 0.1Ω. P = P = P= 90 MW Therefore 90MW of power is lost which is equivalent to 30% • Loss of power is proportional to current squared • reducing current will reduce power loss. • increasing voltage will decrease current

  3. Increasing the Voltage Increasing the voltage (using step up transformer) to decrease current from 30kA to 3kA P = P = P= .9 MW This is a power loss of 0.3% which has been significantly reduced. Transformers only work with AC current, therefore AC current is more efficient than DC current

  4. Electrical Power Grid • A giant circuit with many parallel circuits fed by a number of power plants. • Step-up transformers used to minimize energy loss • Voltage can’t be increase too high otherwise it will discharge through the air and transfer to the ground. • A number of different substations have step-down transformers to bring the voltage down to a level that can be used in the homes

  5. Electrical Power Grid Cont… • Energy is fed into the grid by demand • Energy is not easily stored • If too much is generated, they sell it to other users (US) • If more is needed, they buy it from other producers (US) • The delivery fee listed on your electricity bill is there to cover the costs of maintenance of the grid

  6. AC Generators used in Power Plants • Contain multiple coils and armatures • Permanent magnets are not used. Hard to find strong enough magnets, magnets lose magnetism due to strong magnetic fields in the coils themselves. • Electromagnets are used • The current to create the electromagnet comes from • the generator itself • DC generator that uses permanent magnets and an external source such as falling water

  7. Homework • Pg 612 #’s 1-6

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