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transmission of power

transmission of power

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• 1. Topic 12: Electromagnetic induction
• 12.3: Transmission of electrical power
• 2. Energy losses
• Energy is lost when it is transmitted
• At the power transmission lines
• transformers
• 3.
• Large amounts of electrical energy Are transmitted each second, from the power stations to the consumers, often over large distances.
• Since power = current x voltage, we could use:
• either a) a low voltage and a high current,
• or b) a high voltage and a low current.
• 4.
• Why does the National Grid always use method (b)?
• Remember that a current always produces heat in a resistor.
• If the cables have resistance R, and carry a current I, the energy converted to heat each second is I 2 R
• P = I 2 R
• 5.
• This means that in method (a) the high current produces a lot of heat in the cables and little of the energy from the power station gets to the consumer.
• Method (b) is used because the low current minimises the power loss.
• Transformers at each end of the system step the voltage up and then down.
• 6. Losses in transformers
• Copper losses: the wires have some resistance
• Hystereis loss: Magnetising and demagnetising uses power
• Eddy currents: small currents form in the core
• 7. Transmission of Power
• 8.
• At the power station side:
• Voltage is stepped up with a transformer to 275000 V
• This reduces electrical loss in the transmission lines
• 9.
• At the end of the line
• Voltage is stepped-down with a transformer to
• 33000 V: heavy industry
• 11000 V: Light industry
• 230 V : Homes
• 10. Health risks
• How many transformers are there in your home?
• How many electric fields are you exposed to everyday?
• What about wireless internet?
• Can these pose a threat to our health?
• 11.
• Electric fields from power lines and mobile phone masts are all around us
• Electric fields are known to interact with tissues by inducing electric fields and currents in them.
• Some studies have found a higher rate of cancer in people living close to power lines
• 12. How can these fields do this?
• Results from animal studies conducted so far suggest that electric fields do not initiate or promote cancer.
• Electric fields and magnetic fields were classified as possibly carcinogenic to humans based on epidemiological studies of childhood leukaemia
• 13.
• &quot;Possibly carcinogenic to humans&quot; is a classification used to denote an agent for which there is limited evidence of carcinogenicity in humans and less than sufficient evidence for carcinogenicity in experimental animals.
• 14. What about high-voltage power lines?
• Do not touch them!!
• Again no risk of cancer has been found