08-11-2012, 05:03 PM
How The Grid Works
1Grid Works.ppt (Size: 2.58 MB / Downloads: 75)
Evolving Transmission Grid— Evolving Issues
Before 1920 transmission was not an identifiable asset
By mid-century, transmission was being built to serve local needs and for reliability and cost control purposes; very little interstate grid existed
As larger generator plants located farther from load, transmission expanded, reducing what was needed to serve load
In the 1960s and 1970s, voltages increased, transmission helped reduce reserves, costs, and blackouts
Transmission integration increased bulk power transactions, market integration
Today’s National Grid
Key network infrastructure vital to the nation’s economy
A nationwide164,000-mile, highly-integrated network of transmission lines and control facilities, interconnecting over 750,000 MW of generating capacity to millions of customers in all regions, and 3000 utilities
The Challenges Facing Transmission Investment
Aging and deteriorating infrastructure
More dispersed sources of generation
Wholesale competition among generators
Complex bulk power markets
Arrival of the digital economy
Electricity consumption doubled after 1980; consumer electronics increase
Basic Definitions
Voltage – electrical “pressure” measured in volts. For power systems we typically measure in 1000’s of volts or kilovolts (kv)
Current – the movement of electrons through a conductor measured in Amperes (A)
Power – Rate at which electricity does work. Measured in Watts or more typically kilowatts (kW) or megawatts (MW)
Energy – The amount of work that can be done by electricity. Measured in Watt-hours or more typically kilowatt-hours (kWh) or megawatt-hours (MWh).
Components of the Grid: Transmission
Used to move power long distances from generators to load with low losses.
Highly interconnected for enhanced reliability
The “interstate system” for electricity
Traditionally built to enhance reliability for vertically integrated utilities.
Now a critical part of the electric markets
Interconnected Operation
Power systems are interconnected across large areas. For example, most of North America east of the Rockies (with exceptions for Quebec and most of TX) is an interconnection.
Individual utilities within each interconnection own and operate a small portion of the system (a balancing area).
Transmission lines known as “tie lines” connect the individual utilities to each other.