Published on EGEE 401: Energy in a Changing World (https://www.e-education.psu.edu/egee401)

Home > EGEE 401 > Unit 3, Lesson 5 > Power Grid

Power Grid

Viewing Assignment

Watch video, How the grid works [1] (BURN [2]: Radio, The Public Radio Energy Project, 4:24 min)

The electricity power grid is the physical system that delivers electricity from the place where it is generated to the site where it is used.

Basic concepts:

  • The electricity leaving the generating station enters a sub-station with a step-up transformer that raises the voltage extremely high for long-distance transmission.
  • When electricity travels through a conductor (wires), some energy is lost. Less energy is lost when the electricity is at a higher voltage. At a higher voltage, nearly the same amount of power can be transmitted but at a lower current. The amount of energy lost from the conductor (line losses) is directly proportional to the current. The less the current, the less the losses.  Typically in the U.S., line losses between generation and end-use are in the 6% to 8% range.
  • The high-voltage electricity is carried over transmission lines to local substations where a step-down transformer reduces the voltage to levels suitable for customer loads. Distribution lines carry the lower-voltage electricity from the local substations to customer sites.
Diagram of the Electricity Power Grid. See link in caption for text version.
The Electricity Power Grid.
Text Version [3]
Credit: U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability [4]

Reading Assignment

From Energy Explained, read How Electricity is Delivered to Consumers [5] (updated Dec 2016)

Simulation Assignment

The Power Grid is a simulation applet, developed at the University of Illinois in partnership with The Office for Mathematics, Science, and Technology Education (MSTE) in the College of Education and the Information Trust Institute.

  • Access the simulation applet The Power Grid [6].
  • Read the introduction paragraph.
  • BE SURE to follow note regarding browser compatibility.

User Guidelines

When the applet opens, power is being produced by four of the five generators. You can see the power moving from the generators through the substations and to the users in the Communities of Commerceton, Industryville, and Residenceburg.

Any power that is not used by the communities is sent to users in other systems. If the generators are not producing enough power, power will be purchased from other systems. In the applet this is indicated by the two External Systems. (This simulation is designed to blackout if both External Systems are disconnected from the system.)

The arrows show the direction the power is moving. The current is flowing out of the generators, through the substations and into the communities. Bigger arrows indicate more power.

The transmission lines in the applet have varying capacities. They range from 1000 MW to 2000 MW. The line flow for each line is noted near the line and changes as the power flow changes. (When a line is carrying less than 85% of its capacity, the arrows are green, indicating that the flows are within normal operating conditions. As the flow moves past 85% of the line capacity, the arrows turn orange, indicating that the lines should not be made to carry much more power. As the flow continues to increase past the maximum, the arrows turn red.) If a line remains overloaded for approximately 10 seconds, it automatically opens and a notification is displayed.

If a community demands more power than the transmission line that serves it can carry, the community will blackout. A community may also blackout if a line is damaged. In the applet as well as in reality, a transmission line problem in one area of the system can cause blackouts in several areas.

There are five generators represented in this simulation. The coal, hydropower and natural gas generators have adjustable outputs. The others do not. Click on the up and down arrows to the right of MW output labels to change the production.

While wind's output cannot be adjusted, its variation can be set from "none" to "High" using the slider below the system graphic.

All of the generators have connection switches that you can open or close.

 


Source URL: https://www.e-education.psu.edu/egee401/content/p5_p4.html

Links
[1] https://www.youtube.com/watch?v=1dZjohZPIqE#t=128
[2] http://burnanenergyjournal.com/about-burn/
[3] https://www.e-education.psu.edu/egee401/sites/www.e-education.psu.edu.egee401/files/image/lesson05/BetterGrid_LD.html
[4] http://energy.gov/oe/office-electricity-delivery-and-energy-reliability
[5] http://www.eia.gov/energyexplained/index.cfm?page=electricity_delivery
[6] https://credc.mste.illinois.edu/applet/pg