POWER FLOW DESIGN PROJECT
1. Problem and Report
A skeleton power system is shown in Figure 1. The characteristics of the skeleton system and the system to be designed are provided in Section 2. The performance criteria and methods to meet the criteria are provided in Section 3. Using a power flow program, manual calculations and your knowledge, design the power system to meet the criteria while minimizing the cost of equipment and dispatching generation in the most economical manner.
The report on your study will be presented in the following form:
1.1 Selecting 100 MVA base and 345 kV for the region enclosing buses 4 and 10, the impedance diagram for the final system and supporting calculations are provided. Use Figure 2 as a base.
1.2 Final system flow diagrams with voltages for the following conditions. Use Figure 2 as a base.
1. Heavy loads, all lines in service
2. Heavy loads, one 345 kV line out
3. Light loads, all lines in service
1.3 Completed Tables 1 and 2 showing transformer tap schedules, generator voltage
schedules, shunt reactor and capacitor schedules, and generator loading for the following conditions:
1. Heavy loading, one 345 kV line out. (Table 1)
2. Light loading, all lines in. (Table 2)
1.4 Calculations for fixed reactor sizing on the 345 kV line ends.
Give reactor size in MVAR and kV rating.
1.5 Calculations for series compensation sizing. Give your selected Series Compensation in per cent.
1.6 Provide justification for any added transmission lines or other equipment.
1.7 Graduate Students: In addition to the Problem and Report section above, determine if line additions could have been reduced by replacing ACSR conductor on some lines with ACCR conductor of the same size.
1. New Transmission line construction costs: $3M/mile (bundled or unbundled);
2. Reconductoring to add line bundling to existing transmission line cost: $1M/mile
3. Generation construction cost:
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Technology
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Capital Cost ($/kW)
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Availability (My numbers)
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Effective Cost
|
Min Size (My numbers)
|
|
Coal
|
2,800+ ($1k for CO2 sequestration)
|
1
|
2,800+ ($1k for CO2 sequestration)
|
750 MW
|
|
Combined Cycle
|
1,300
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1
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1,300
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350 MW
|
|
Nuclear
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5,800 - 8,000
|
1
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5,800 - 8,000
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500 MW
|
|
Solar PV
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2,400 (Inc Govt' Subsidies)
|
1
|
2,400 (Inc Govt' Subsidies)
|
2 MW
|
|
Solar Thermal
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4,900 (Inc Govt' Subsidies)
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»1 (on peak)
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4,900 (Inc Govt' Subsidies)
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2 MW
|
|
Wind
|
1,700 (Inc Govt' Subsidies)
|
0.4
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4,250 (Inc Govt' Subsidies)
|
10 MW
|
The suggested sequence of activities to complete your studies and prepare your report are given in Section 4 on Page 5.
2. Power System Characteristics
2.1 Transmission Lines
2.1.1 230 kV Lines
1. All 230 kV lines have 795KCM ACSR 26/7 conductor and have flat spacing of 17.8 feet. <<< second project should be calculated as 17.2 feet
2. The scale on the system diagram in Figure 1 is one inch = 50 miles.
3. Circuit constants can be obtained by use of nominal pi for 230 kV lines
2.1.2 345 kV Lines
1. Bus 4 is 300 miles from Bus 6
2. The 345 kV lines have the following characteristics:
25 foot flat spacing between phases
2 conductors per phase spaced at 18 inches
954 KCM 54/7 conductor
3. Use the equivalent pi model to represent the 345 kV lines.
2.2 Generating Stations
2.2.1 Units 1 and 2
1. The 2 units are identical with the following rating: 22.0 kV, 300MW, 0.9 pf lagging, 0.9 pf leading
2. The 2 3-phase transformers are identical with the following rating, connections and no-load taps: 350 MVA, 21:345 kV, 8.0% reactance 2 - 2 ½% taps above nominal, 2 - 2 ½% taps below nominal 21 kV delta : 345 kV grounded wye
2.2.2 Units 3, 4, and 5
Three identical units rated at 200 MW and 0.95 pf lagging, 0.95 pf leading. All units are regulated to hold constant voltage on the 230 kV bus.
2.2.3 Units 6 and 7
Two identical units rated at 350 MW and 0.85 pf lagging, 0.85 pf leading. Both units are regulated to hold constant voltage on the 230 kV bus. These units control the slack bus.
2.2.4 Economy of Units
The economy of generation by the various units is reduced in the following sequence:
1. Units 3, 4, and 5 (least expensive)
2. Units 1 and 2
3. Units 6 and 7 (most expensive)
2.2.5 Loading of Units
1. If a unit is on line, it must have a minimum load of 30% of the unit MW rating.
2. 15% spinning reserve must be provided at all times.
2.3 345 kV Southern Line Terminal
The 3-phase transformer banks at the southern line terminal of the 345 kV lines have the following ratings, connections and taps: 400/500/650 MVA, OA/FA/FOA, 6.0% reactance on the lowest MVA rating 230 kV grounded wye: 345 kV grounded wye 2 - 2 ½ % taps above nominal, 2 - 2 ½ % taps below nominal on the high side of the transformer.
2.4 Loads
The loads shown in Figure 1 are for the annual system peak ( MW/MVAR) The annual minimum MW loads are 25 % of the annual MW peak loads at 0.98 power factor lagging.
System Voltages
2.4.1 Generator Voltages
The generator voltages can be varied between 0.95 per unit and 1.05 per unit.
2.4.2 230 kV Bus Voltages
230 kV bus voltages must be held within a range of 0.99 per unit to 1.02 per unit for any system condition and loading level.
2.4.3 345 kV Bus Voltages
345 kV voltages can not exceed 1.1 per unit for any system condition and loading level.
2.5 Contingency Operation
All system criteria must be met for all first contingency conditions. That is, loss of any single system element: line, transformer, or generator.
Must recheck criteria after making changes.
3. Performance Criteria and Methods to Meet Criteria
3.1 Voltage on the open end of the 345 kV lines shall not exceed 1.1 per unit when the voltage at the closed end of the line is 1.05 per unit and the series capacitors are bypassed.
Add fixed shunt reactors at the two ends of each 345 kV line to meet this criterion. Model the reactors by modifying line susceptance.
3.2 No system element shall be overloaded for a first contingency.
Add transmission lines, bundled conductors or modify buses, if necessary, to meet this criteria.
3.3 The voltage on all 230 kV buses must be between 0.99 per unit and 1.02 per unit for all of the following conditions:
1. Heavy loading, one 345 kV line out
2. Light loading
3. Base Case*
Use the following methods to meet these criteria, as required:
1. Switched shunt reactors and capacitors
2. Generator terminal voltage limits between 0.95 and 1.05 per unit
3. Winter and summer transformer tap schedules
3.4 The voltage angle between Bus 4 and the load end of one 345 kV line shall not exceed 30 degrees when the other 345 kV line is out of service.
Add series capacitors, if necessary, to meet this criterion.
Represent the series compensation by reduction of the Z - pi.
- Base case is defined as the heavy loaded system with optimum transformer taps and including any fixed shunt reactors, series capacitors and transmission lines that were added to meet the Performance Criteria.
4. Suggested Sequence for Power Flow Problem
4.1 Make calculations for the system model using 100 MVA base and kV bases of 22 kV, 230 kV and 345 kV.
4.2 Prepare impedance diagram
4.3 Prepare data for computer program input
4.4 Make computer data file
4.5 Run preliminary base case. (Heavily loaded system.) Hint: You will need to add fictitious generators at buses to get the power flow to solve.)
4.6 Determine series capacitor requirements for the 345 kV lines assuming you'll need to ship all 600 MW from generators 1 and 2 over one line (one line out) under heavily loaded case.
4.7 Determine fixed shunt reactor requirements under lightly loaded case to compensate for the Ferranti Effect on the 345 kV lines.
4.8 Determine the need for additional lines or equipment
Must recheck criteria after making changes. Take costs into account.
7.9 Determine the generator voltage schedules, transformer tap schedules and switched shunt reactor and capacitor requirements for voltage control for base case. (See definition of the base case: heavily loaded etc.)
7.10 Determine the generator voltage schedules, transformer tap schedules and switched shunt reactor and capacitor requirements for voltage control for lightly loaded case.
7.11 Fill in the schedule templates for the heavily loaded case with one line out of service and the lightly loaded case.
Attachment:- Assignment Files.rar