Youve just been hired as a new power engineer with Kyle and Weber Wind (KWW), one of the countrys leading wind energy developers. KWW has identified the rolling hills to the northwest of the Metropolis urban area as an ideal location for a new 200 MW wind farm. The local utility, Metropolis Light and Power (MLP), seems amenable to this new generation development taking place within their service territory. However, they are also quite adamant that any of the costs associated with transmission system upgrades necessary to site this new generation be funded by KWW. Therefore, your supervisor at KWW has requested that you do a preliminary transmission planning assessment to determine the least cost design.Hence, your job is to make recommendations on the least cost design for the construction of new lines and transformers to ensure that the transmission system in the MLP system is adequate for any base case or first contingency loading situation when the KWW wind farm is installed and operating at its maximum output of 200 MW. Since the wind farm will be built with Type 3 DFAG wind turbines, you can model the wind farm in the power flow as a single, equivalent traditional PV bus generator with an output of 200 MW, a voltage setpoint of 1.05 per unit, and with reactive power limits of 100 Mvar. In keeping with KWW tradition, the wind interconnection point will be at 69 kV, and for reliability purposes your supervisor requests that there be two separate feeds into the interconnection substation.The following table shows the available right-of-way distances for the construction of new 69 kV and/or new 138 kV lines. All existing 69 kV only substations are large enough to accommodate 138 kV as well.
Design Procedure
1. Load DesignCase1 into PowerWorld Simulator. This case containsthe initial system power flow case, and the disconnected KWW generator and its interconnection bus. Perform an initial power-flow solution to determine the initial system operating point. From this solutionyou should find that all the line flows and bus voltage magnitudes arewithin their limits. Assume all line MVA flows must be at or below100% of their limit values, and all voltages must be between 0.95 and1.10 per unit.
2. Repeat the above analysis considering the impact of any singletransmission line or transformer outage. This is known as n-1 contingency analysis. To simplify this analysis, PowerWorld Simulatorhas the ability to automatically perform a contingency analysisstudy. Select Tools, Contingency Analysis to show the ContingencyAnalysis display. Note that the 57 single line/transformer contingencies are already defined. Select Start Run (toward the bottomright corner of the display) to automatically see the impact of removing any single element. Without the KWW generation the system has no contingency (n-1) violations.
3. Using the available rights-of-ways and the transmission line parameters/costs given in the table, iteratively determine the least expensivesystem additions so that the base case and all the contingences result inreliable operation points with the KWW generation connected with anoutput of 200 MW. The parameters of the new transmission lines(s)need to be derived using the tower configurations and conductor typesprovided by the instructor. In addition, the transmission changes you propose will modify the total system losses, indicated by the yellowfield on the one-line. While the system losses are not KWWs responsibility, your supervisor has asked you to consider the impact your design changes will have on the total system losses assuming the system operates in the studied condition for the next five years. Hence, youshould minimize the total construction costs minus the savings associated with any decrease in system losses over the next five years.
4. Write a detailed report including the justification for your final recommendation.
To simplify the analysis, several assumptions are made:1. You need only consider the base case loading level given in DesignCase1. In a real design, typically a number of diferent operating points/loading levels must be considered.
2. You should consider all the generator real power outputs, includingthat of the new KWW generation, as fixed values. The change in thetotal system generation due to the addition of the 200 MW in KWWgeneration and any changes in the system losses are always pickedup by the system slack.
3. You should not modify the status of the capacitors or the transformer taps.
4. You should assume that the system losses remain constant over the five-year period, and you need only consider the impact and new design has on the base case losses. The price for losses can be assumed to be $50/MWh.
5. You do not need to consider contingencies involving the new transmission lines and possibly any transformers you may be addin
6. While an appropriate control response to a contingency might be todecrease the KWW wind farm output (by changing the pitch on thewind turbine blades), your supervisor has specifically asked you notto consider this possibility. Therefore the KWW generator shouldalways be assumed to have a 200 MW output.Available New Rights-of-Ways for Design Case 1