Wimshurst Machine

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Wimshurst Machine

• two large contra-rotating discs mounted in a
  vertical plane, two cross bars with metallic
  brushes, and a spark gap formed by two metal
  spheres.
• two insulated disks and their metal sectors
  rotate in opposite directions passing the crossed
  metal neutralizer bars and their brushes.
• imbalance of charges is induced, amplified, and
  collected by two pairs of metal combs with points
  placed near the surfaces of each disk.
• The positive feedback increases the accumulating
  charges exponentially until a spark jumps across
  the gap.
• The accumulated spark energy can be increased by
  adding a pair of Leyden jars, an early type of
  capacitor suitable for high voltages

2
Van de graf generator

• an electrostatic machine which uses a moving belt
  to accumulate very high electrostatically stable
  voltages on a hollow metal globe.

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Van de graaff generator

• Video http//www.youtube.com/watch?vsy05B32XTYY

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Faradays Disk

• A copper disc rotating between
• the poles of a horseshoe magnet.
• produced a small DC voltage,
• and large amounts of current.
• First electromagnetic generator

5
Dynamos

• First generator able to produce electricity for
  industrial purposes
• First dynamo was built by Hippolyte Pixii in
  1832.
• a stationary structure, which provides a constant
  magnetic field, and a set of rotating windings
  which turn within that field.
• Magnetic field may be provided by one or more
  permanent magnets or by one or more
  electromagnets, which are usually called field
  coils.

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Pixii's dynamo
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Dynamos

• Produce a direct current
• Basis for later devices such as the electric
  motor, the alternating-current alternator, and
  the rotary converter.
• Developed as a replacement for batteries

8
Modern electrical power plants

• Boiler Unit Almost all of power plants operate
  by heating water in a boiler unit into super
  heated steam at very high pressures. The source
  of heat from combustion reactions may vary in
  fossil fuel plants from the source of fuels such
  as coal, oil, or natural gas. Biomass, waste
  plant parts, solid waste incinerators are also
  used as a source of heat. All of these sources of
  fuels result in varying amounts of air pollution,
  as well as carbon
• In a nuclear power plant, the fission chain
  reaction of splitting nuclei provides the source
  of heat.

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Modern electrical power plants

• The super heated steam is used to spin the blades
  of a turbine, which turns a coil of wires within
  a circular arrangements of magnets.

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Modern Electric power plants

• Cooling Water After the steam travels through
  the turbine, it must be cooled and condensed back
  into liquid water to start the cycle over again.
  Cooling water can be obtained from a nearby river
  or lake. An alternate method is to use a very
  tall cooling tower, where the evaporation of
  water falling through the tower provides the
  cooling effect.

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Getting the electricity from the plant to the
light switch
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Power transmission

• Power plants are not located near population
  centers
• Need to get the power from the plant to the users
• Edison created the first power system in New York
  City in 1882.
• Used direct current. Could only deliver
  electricity to customers closer than 1.5 miles
  away from the power station.
• Westinghouse proposed using AC current, which
  could be more easily and cheaply transmitted.
  Resulted in the War of Currents
• Edison waged a PR campaign, claiming AC current
  was far more dangerous as at frequencies near
  60HZ, it had a greater potential to cause cardiac
  fibrillations.
• He and his workers publically electrocuted
  animals to make their point.
• Edison opposed capital punishment, but in an
  effort to make his point about AC current, he
  secretly funded the development of the first
  electric chair.

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Power transmission

• Energy is lost in transmission lines
• Materials that allow electrons to flow through
  them (current) are called conductors.
• Every conductor has some resistance to the flow
  of current.
• Energy is lost as the current flows through the
  transmission lines
• Relationship between voltage, current and the
  resistance to current flow is given by V IR

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Power transmission

• The losses in the line are proportional to the
  resistance and the current squared or RI2 and the
  power in the line is proportional to VI (voltage
  times current)
• The solution to these losses is to transmit the
  power at much higher voltages than the users
  need, and step the voltage down along the way.
  That way the current in the line is low, so the
  power losses are low.
• So the voltage is increased before the
  electricity leaves the power station and then
  decreased as needed.
• This is accomplished with a device called a
  transformer

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Transformers

• No not these guys..

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Transformers

• A device that transfers energy from one
  electrical circuit to another using the concept
  of induction
• A changing current in the first circuit (the
  primary) creates a changing magnetic field. This
  changing magnetic field induces a changing
  voltage in the second circuit (the secondary).
  This effect is called mutual induction.

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Transformers

• The number of coils in the windings determine if
  the voltage is increased (stepped up) or
  decreased (stepped down)
• If the number of coils in the secondary is larger
  than the primary, voltage is stepped up, if it is
  less it is stepped down.

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Power transmission

• At the power station, the generator produces
  13-25kV.
• A step up transformer boosts this to 115 to 765
  kV.
• Substations reduce the voltages for local
  distribution.
• Transformers on power poles reduce it further to
  the 240 V generally fed into our homes.

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Power Transmission
20
Health Risks from Power Lines

• Power lines are live, if you touch them (and are
  in contact with the ground) you provide the
  current a path to ground. AC currents can induce
  heart fibrillations and cause death.
• NO strong link to overhead power lines and
  increased cancer due to the lines themselves.

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Power Grid

• A network of power transmission systems
• Usually more than one path between points on a
  network

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Power Grid

• The US and Canadian power companies are
  integrated into a single power grid
• Allows backups in case of emergencies, utilities
  can trade electrical energy and it is economical
• Circuit breakers (devices which cut off the flow
  of electricity through the circuit) protect
  against sudden surges in power
• They can isolate the problem and help the grid
  reroute the power flow
• If the problem is not isolated, the problem can
  spread throughout major portions of the grid,
  causing power interruptions we call blackouts.

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US Power Grid

• Three grids cover the contiguous 48 states and
  parts of Canada and Mexico and are known as the
  Western Interconnection, the Eastern
  Interconnection, and the Electric Reliability
  Council of Texas (ERCOT) Interconnection.
  Collectively they make up what is called the
  national power grid
• Each grid may be broken up into smaller power
  sharing arrangements, described below.
• ECAR - East Central Area Reliability Coordination
  Agreement
• ERCOT - Electric Reliability Council of Texas
• FRCC - Florida Reliability Coordinating Council
• MAAC - Mid-Atlantic Area Council
• MAIN - Mid-America Interconnected Network
• MAPP - Mid-Continent Area Power Pool
• NPCC - Northeast Power Coordinating Council
• SERC - Southeastern Electric Reliability Council
• SPP - Southwest Power Pool
• WSCC - Western Systems Coordinating Council

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Power interruptions

• Dropouts -momentary (milliseconds to seconds)
  loss of power typically caused by a temporary
  fault on a power line.
• Brownouts -a drop in voltage in an electrical
  power supply, so named because it typically
  causes lights to dim. Can occur if the demand for
  electricity on the grid is greater than what it
  can produce
• Blackouts - total loss of power to an area
• Note that it doesnt take a bad storm to cause
  problems with power line. If demand increases and
  the power on the line increases, the lines heat
  up and stretch, causing them to sag. If they come
  in contact with a tree, then the line can short
  out.

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2003 Blackout

• Affected much of the Northeastern US and parts of
  Canada August 14, 2003.
• Timeline (Thank you Wilkipedia)
• 1215 p.m. Incorrect telemetry data renders
  inoperative the state estimator, a power flow
  monitoring tool operated by the Ohio-based
  Midwest Independent Transmission System Operator
  (MISO). An operator corrects the telemetry
  problem but forgets to restart the monitoring
  tool.
• 131 p.m. The Eastlake, Ohio generating plant
  shuts down. The plant is owned by FirstEnergy, an
  Akron, Ohio-based company that had experienced
  extensive recent maintenance problems.
• 202 p.m. The first of several 345 kV overhead
  transmission lines in northeast Ohio fails due to
  contact with a tree in Walton Hills, Ohio.
• 214 p.m. An alarm system fails at
  FirstEnergy's control room and is not repaired.
• 227 p.m. A second 345 kV line fails due to
  contact with a tree.

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Timeline

• 305 p.m. A 345 kV transmission line known as
  the Chamberlain-Harding line fails in Parma,
  south of Cleveland, due to a tree.
• 317 p.m. Voltage dips temporarily on the Ohio
  portion of the grid. Controllers take no action.
• 332 p.m. Power shifted by the first failure
  onto another 345 kV power line, the Hanna-Juniper
  interconnection, causes it to sag into a tree,
  bringing it offline as well. While MISO and
  FirstEnergy controllers concentrate on
  understanding the failures, they fail to inform
  system controllers in nearby states.
• 339 p.m. A FirstEnergy 138 kV line fails.
• 341 p.m. A circuit breaker connecting
  FirstEnergy's grid with that of American Electric
  Power is tripped as a 345 kV power line
  (Star-South Canton interconnection) and fifteen
  138 kV lines fail in rapid succession in northern
  Ohio. Later analysis suggests that this could
  have been the last possible chance to save the
  grid if controllers had cut off power to
  Cleveland at this time.
• 346 p.m. A sixth 345 kV line, the Tidd-Canton
  Central line, trips offline.
• 406 p.m. A sustained power surge on some Ohio
  lines begins an uncontrollable cascade after
  another 345 kV line (Sammis-Star interconnection)
  fails.
• 40902 p.m. Voltage sags deeply as Ohio draws
  2 GW of power from Michigan, creating
  simultaneous undervoltage and overcurrent
  conditions as power attempts to flow in such a
  way as to rebalance the system's voltage.
• 41034 p.m. Many transmission lines trip out,
  first in Michigan and then in Ohio, blocking the
  eastward flow of power around the south shore of
  Lake Erie. Suddenly bereft of demand, generating
  stations go offline, creating a huge power
  deficit. In seconds, power surges in from the
  east, overloading east-coast power plants whose
  generators go offline as a protective measure,
  and the blackout is on.
• 41037 p.m. The eastern and western Michigan
  power grids disconnect from each other. Two 345
  kV lines in Michigan trip. A line that runs from
  Grand Ledge to Ann Arbor known as the
  Oneida-Majestic interconnection trips. A short
  time later, a line running from Bay City south to
  Flint in Consumers Energy's system known as the
  Hampton-Thetford line also trips.

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Timeline

• 41038 p.m. Cleveland separates from the
  Pennsylvania grid.
• 41039 p.m. 3.7 GW power flows from the east
  along the north shore of Lake Erie, through
  Ontario to southern Michigan and northern Ohio, a
  flow more than ten times greater than the
  condition 30 seconds earlier, causing a voltage
  drop across the system.
• 41040 p.m. Flow flips to 2 GW eastward from
  Michigan through Ontario (a net reversal of 5.7
  GW of power), then reverses back westward again
  within a half second.
• 41043 p.m. International connections between
  the United States and Canada begin failing.
• 41045 p.m. Northwestern Ontario separates
  from the east when the Wawa-Marathon 230 kV line
  north of Lake Superior disconnects. The first
  Ontario power plants go offline in response to
  the unstable voltage and current demand on the
  system.
• 41046 p.m. New York separates from the New
  England grid.
• 41050 p.m. Ontario separates from the western
  New York grid.
• 41157 p.m. The Keith-Waterman, Bunce
  Creek-Scott 230 kV lines and the St.
  Clair-Lambton 1 and 2 345 kV lines between
  Michigan and Ontario fail.
• 41203 p.m. Windsor, Ontario and surrounding
  areas drop off the grid.
• 413 p.m. End of cascading failure. 256 power
  plants are off-line, 85 of which went offline
  after the grid separations occurred, most due to
  the action of automatic protective controls.

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2003 Northeastern Blackout

• 50 million people in the dark
• Cost economy 1 billion dollars