ELC4394, Smart Grid, Test 2: Planning the Future ERCOT Grid. Version 140303.
Take-Home Test. Due in Class, Monday, March 31, 2014.
(You are not to discuss this test with anyone, unless in the presence of and with the approval of Dr. Grady)
Introduction
The year is 1914. Entrepreneurs who own small power plants that provide power for ice-making plants in the larger cities are considering interconnecting them with transmission lines to improve reliability.
Eventually, larger, more efficient power plants that require cooling lakes will be situated outside cities. One large plant can serve several metro areas. There is even a futuristic plan to develop an electric rail system, the Interurban,” along the transmission right-of-way from Dennison-Dallas-Waco. The Interurban will make it possible for Texans to take convenient daily round trips to downtown Dallas for business and shopping.
Forward-thinking entrepreneurs believe that one day electricity will be in every home, thus presenting a tremendous business opportunity. Home air conditioning may even develop, providing even more business.
Thinking years ahead of their time, the entrepreneurs plan to build 500 MW power plants to provide the expected 3 kW peak load per person load (that number includes not just residences, but all the loads of a city). Thus, a city of 100,000 people would have a peak summer load of 300,000 kW, or 300 MW. A city of
1,000,000 would require 3,000 MW (a.k.a. 3 GW). Eventually Texas could have 20 million people, requiring
20,000,000 * 3 kW = 60,000,000 kW = 60 GW. Even at low periods, such as spring/fall evenings, the demand would be approximately 40% of summer peak. Imagine that one kWh, the amount of physical energy that a hard-working human can provide in one day, might sell for only $1 (adjusted for 1914). 60
GW amounts to $60 million per hour. $$$$$! Even if the cost per kW eventually, and over decades, drops by a factor of 10, to $0.1, the income per hour will still be $6 million.
Project Objectives
Your job is to design the transmission network and reactive support requirements for the future ERCOT.
Focus on two load/generation conditions which bound the design problem:
1. Summer Peak,
2. Spring/Fall Minimum.
Design Requirements:
Minimum cost, while meeting the following constraints:
There are two types of single contingencies to study:
1. The sudden outage of any double-circuit 345 kV transmission line,
2. The sudden loss of any generator
Single contingencies should not cause
1.
An overload on any transmission line,
2.
An overload on any generator,
3.
No voltage greater than 1.05 pu,
4.
No voltage less than 0.95 pu.
Exceptions to the above may be acceptable if the cost is excessive, but details for such exceptions need to be made clear so that a reasonable cost versus risk engineering decision can be made.
Reporting:
Your report is to be a Word document, prepared with simulation results, explanations, and cost estimates, as if you were writing it for the entrepreneurs. Following the steps given here will lead you to a system that works. If you wish, you may innovate by investigating ways to save money by taking on small risk, and perhaps increase your chance of being awarded this huge project.
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ELC4394, Smart Grid, Test 2: Planning the Future ERCOT Grid. Version 140303.
Take-Home Test. Due in Class, Monday, March 31, 2014.
(You are not to discuss this test with anyone, unless in the presence of and with the approval of Dr. Grady)
I. Procedure for Developing the Summer Peak Case, Ignoring Contingencies
Step 1. Begin with the summer peak case, ignoring contingencies. Place one double-circuit 345 kV line in each corridor. “Shrink” the grid so that each corridor is only 10% actual length. Fix generator voltages at
1.02 pu. Remove Qgen limits on generators. Enter the area P interchange requirements consistent with the schematic, employing equal division of losses. Solve with PCFLO, and then determine how many additional double-circuit lines each corridor needs, ignoring any line outage contingency requirements.
Step 2 (hand calculations). Using your transmission plan from Step 1 and actual corridor km, estimate total km of 345 kV circuits and total capacitive line charging. Compare total capacitive line charging to total reactive load power.
Step 3 (hand calculations). Estimate the I 2 R and I 2 X transmission line losses for the summer peak condition.
With these estimates, plus those from Step 2, to estimate required Pgen from generators, and required
Qgen from generators and added shunt capacitors.
Step 4. Lengthen the double-circuit lines to full length and solve with PCFLO. Create row “PCFLO Step 4” in a results table that gives the following sum totals for all ERCOT. Include “Est. Line Charging” from Step 2.

Pgen,

Pload,

Ploss = Pgen - Pload,

Qgen,

Qload,

Qloss = Qgen - Qload.

Est. Line Charging from Step 2

System Cost (not used in Step 4)
Ploss is due to I 2 R. Qloss is due to I 2 X, minus capacitive line charging. Use solved area Pgens to determine the number of 500 MW generators needed for each area.
Step 5. If the number of generators in an area cannot supply area Qgens from Step 4, add 100MVAr increments of shunt capacitance or reactance to bring area generators within Q limits. Solve with PCFLO to confirm. Create results table row “PCFLO Step 5.” Compute the cost of your system and enter it into the table.
For calibration purposes, all students should have the exact same results for Step 5.
II. Procedure for Developing the Summer Peak Case, Including Contingency Constraints
Based upon your experience in Steps 1 – 5, design and confirm via PCFLO the upgrades needed so that the summer peak case satisfies design constraints on page 1. Explain changes needed, giving simulation results, and compute cost of upgrades.
III. Central Texas Going Green
Central Texas wants to replace 1 GW of local generation by building wind farms. During summer peak, coastal wind farms near Valley Bus 5 will produce the 1 GW. During Spring/Fall minimum, wind farms near
West Texas Bus 7 will produce the 1 GW. Central Texas will have to pay for the grid upgrades, including the
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1, HOU
2, DFW
ELC4394, Smart Grid, Test 2: Planning the Future ERCOT Grid. Version 140303.
Take-Home Test. Due in Class, Monday, March 31, 2014.
(You are not to discuss this test with anyone, unless in the presence of and with the approval of Dr. Grady) possibility of new transmission lines from Central Texas to West Texas, 450 km. Develop a plan, with cost.
Also, examine the impact that “Going Green” will have on losses in the other ERCOT areas.
• Summer Peak, 3 kW per person, 20 million people, 60 GW
•
Winter Peak, 80% of Summer Peak
• Summer/Winter Nightime, 50% of Daily Peak
• Spring/Fall Minimum, 40% of Summer Peak
• Approx 5% losses.
• Load pf = 0.90 (OK to use Q / P = 0.5).
Bus 7
400 km
Bus 2
DFW
250 km
Bus 6
COAL
BUS
LOAD
% OF
TOTAL
SUMMER
GEN
% OF
TOTAL
SPRING/
FALL GEN
% OF
TOTAL
WIND
250 km
400 km
30%
25%
45%
10%
25%
10%
Bus 3
CTX
3, CTX
4, SA
5, VAL
5%
20%
10%
5%
10%
10%
5%
5%
15%
200 km
Bus 4
300 km
Bus 1
HOU
6, COAL 5% 15% 15%
7, WIND 5% 5% 25%
Generators:
500 MW, pf(leading) ≥ 0.90, pf(lagging) ≥ 0.95. Cost = $1.5 million per MW.
SA
400 km
Transmission Lines:
Double-circuit 345 kV, 2-bundled conductors per phase, 400A per conductor,
500 MVA per circuit, 1000 MVA for both circuits.
Cost = $1 million per double-circuit km. Transmission line constants for each circuit are:
• R = 0.00306 pu per 100 km,
• X (60 Hz) = 0.0314 pu per 100 km,
• Capacitive line charging = 50 MVAr per 100 km.
Bus 5
VAL
Shunt Reactive Capacitors and Reactors:
Switchable in steps of 100 MVAr. Cost = $0.15 million per MVAr.
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