ECE 476 POWER SYSTEM ANALYSIS Lecture 18 Markets, Fault Analysis Muhammad Abdul Retha lefte Al-Badri Department of Electrical and Computer Engineering

Announcements Be reading Chapter 7 HW 7 is 12.26, 12.28, 12.29, 7.1 due October 27 in class. Correct case for 12.29 was emailed out; demo of OPF during class US citizens and permanent residents should consider applying for a Grainger Power Engineering Awards. Due Nov 1. See http://energy.ece.illinois.edu/grainger.html for details. The Design Project, which is worth three regular homeworks, is assigned today; it is due on Nov 17 in class. It is Design Project 2 from Chapter 6 (fifth edition of course). For tower configuration assume a symmetric conductor spacing, with the distance in feet given by the following formula: (Last two digits of your EIN+50)/9. Example student A has an UIN of xxx65. Then his/her spacing is (65+50)/9 = 12.78 ft.

Why not pay as bid? Two options for paying market participants Pay last accepted offer What would be potential advantages/disadvantages of both? Talk about supply and demand curves, scarcity, withholding, market power

In the News: Electricity Price Caps Texas (ERCOT) is considering raising the maximum wholesale price cap from $3000/MWh to $6000/MWh to encourage more electric supply. Average price in 2010 was $40/MWh, down from $86/Mwh in 2008. ERCOT is not subject to most federal regulations Source: Wall Street Journal, Oct 3, 2011

Market Experiments

Fault Analysis The cause of electric power system faults is insulation breakdown This breakdown can be due to a variety of different factors lightning wires blowing together in the wind animals or plants coming in contact with the wires salt spray or pollution on insulators

Fault Types There are two main types of faults symmetric faults: system remains balanced; these faults are relatively rare, but are the easiest to analyze so we’ll consider them first. unsymmetric faults: system is no longer balanced; very common, but more difficult to analyze Most common type of fault on a three phase system by far is the single line-to-ground (SLG), followed by the line-to-line faults (LL), double line-to-ground (DLG) faults, and balanced three phase faults On very high voltage lines faults are practically always single line to ground due to large conductor spacing

Worldwide Lightning Strike Density Units are Lightning Flashes per square km per year; Florida is top location in the US; very few on the West Coast, or HI, AK. This is an important consideration when talking about electric reliability! Source: http://science.nasa.gov/science-news/science-at-nasa/2001/ast05dec_1/

Lightning Strike Event Sequence Lighting hits line, setting up an ionized path to ground Tens of millions of lightning strikes per year in US! a single typical stroke might have 25,000 amps, with a rise time of 10 s, dissipated in 200 s. multiple strokes can occur in a single flash, causing the lightning to appear to flicker, with the total event lasting up to a second. Conduction path is maintained by ionized air after lightning stroke energy has dissipated, resulting in high fault currents (often > 25,000 amps!)