Electricity Infrastructure: Overview and Issues (1) H. Scott Matthews February 13, 2003

Recap of Last Lecture  Current trans. system a 50-year project with significant govt funding  Generally paid for with gas (user) taxes  System of highways is ubiquitous, with most mileage and jurisdiction at the local level  But most use/miles traveled arterial

Energy Use in the US  Fuelwood dominant energy source from founding of colonies to late 19 th cent. (farms)  Total work from all types of engines did not exceed animals until mid-late 19 th century.  Coal (early 19 th century) surpassed fuelwood as dominant energy source  Petroleum and natural gas surpassed coal as dominant (total) energy source around  Consumption of these resources quadrupled in a single generation (urbanization too)

More Energy in US  Hydro & nuclear appeared around 1890 and 1957 respectively, yet have never gained dominance.  Recent developments include solar, geothermal, wind, ocean wave power  For much of history, US self-sufficient in energy for the most part (small coal imports from Britain during colonial times)  Production / consumption rates essentially balanced in US until ~ late 1950s, at which time production fell behind consumption.  During 1970s the gap widened greatly

History of Electricity/Grid  Electricity ‘system’ created in US 1881  Purpose was electricity for lights  Edison had first central generation plant with small local distribution system (DC only)  1881 cost: 24 cents/kWh! (now ~10 cents)  Early 1900’s - intercity transmission lines  As utilities crossed state lines, had state PUCs, federal oversight, regulation  1930s-1950s: rural electrification, federally- run electric generating plants (hydro)  1950s- now: nuclear power, environ. Controls, fuel costs, Three Mile Island

What is Electric Power Grid?  System of:  Generators (power plants)  Transmission Lines (wires)  Substations  Distribution Lines  Transformers  Control Devices  Users

Energy Used for Generation  Predominantly fossil fuels in US  Requires transport of fuel from source to power plant (recall transmission versus rail example last week)  Separate infrastructure problem

Generators  Generally something spinning an electrical generator (usually steam turbine) creating 3- phase AC power  Everyone knows what DC (direct current) is - e.g. batteries, fixed sources  Houses use single-phase AC (alternating current), 60 cycles/second (Hz), max 170V, min -170V, root-mean-square = 120V  Why AC grids?  Generators making AC!  Converting AC->DC easier than DC->AC  Transformers need AC (coming next)

Power Systems - Transmission  Instead of a ‘ground wire’, power systems use the ground (literally)  From generator, to substation to ‘step up’ voltage for trans. lines  155 to 765 kV!  Can be sent hundreds (thous?) of miles  Trans. Lines : 3 wires (one per phase)

Power Systems - Distribution  From trans. Line to power substation  Steps voltage down (resid: 7200V)  Splits power into a bus to feed off  Has circuit breakers for protection  Then to distribution bus(es)  Each distribution bus carries 3-phase lines closer to users  Users only need 1 phase, so the distribution bus keeps getting split until only 1 phase carried on poles  And another (small) transformer used on pole outside of house to step down to 240V

Other Issues  Its generally easy to site the distribution part of the grid  If you want electricity, you need to allow it  Its much harder to get power plants and transmission lines sited  Local/affected population may or may not be ‘served’ by them - no incentive  Transmission is probably most critical ‘systems engineering problem’ in grid  Electrification also led to ‘sprawl’ as it allowed firms to locate away from energy sources

Blackout of November 9, 1965  By 1965, electricity part of everyday life  Most of NE US (and Canada!) dark  Sign that we were not managing well  Six days to realize source of problem  1 relay failed at station in Canada (Niagara Falls)  Caused transmission line to go ‘open’  Caused series of cascading failures all the way back to New York City  Took only 15 minutes to blackout NE US  Caused people to rethink dependence  Until then, power systems design geared around ‘isolation’ to prevent damage