Power Systems Study Project 2021

Objective of the Study

The objective of this study is to develop a capacity to conduct the analytical studies sufficient to allow valid and responsible engineering decisions to be made in the context of system planning and operation. To do this we will study the behaviour of a simple (but representative) 30 bus power system, as illustrated in figure 1. The various capabilities of the Power World software will provide sufficient analysis tools for our purpose. This project is to be conducted on an individual basis. The study specification provided below is flexible and its intent is to expose students to a realistic system and to observe and interpret its behaviour, rather than simply obtain results for a prescribed set of scenarios. Each student may use a different approach to the factors studied. 1. Begin by entering your “Base Case” system as given into Power World. The Base Case represents the normal high load condition. Examine the power flows and the voltage profile of the network. All load buses should be within normal system tolerances (i.e. 0.95 p.u – 1.06 p.u.). Use caution when entering the tap-settings for the transformers (e.g. tap 0.95 on the primary side produces the same effect as tap 1/0.95 on the secondary side). 2. Observe the system behaviour under the condition where any line or transformer is at fault or taken is out of service. This represents the N-1 contingency test. Are there any lines or transformers that can not be taken out of service without the system voltages departing from the acceptable limits (i.e. 0.95 p.u – 1.06 p.u.), or overloading of the remaining transformers and lines? In particular, are there sections of the network that are marginal? Power World has a Contingency function which may help. You can tabulate and summarise your results. 3. Define a light load case where the loads are about 40% of those shown. Power World has a Scale Case function which may be useful here (but please save a copy, since in part 5 you will return to the base case again). Are there any voltages that are unacceptably high or low (and why)? Suggest a remedial strategy to compensate for any voltages that are out of spec. and verify the effectiveness of the strategy (Note: this should not require any additional capital expenditure, since the light load is a normal situation, which happens every night. Instead, try to use the regulations that already exist in the system). Discuss the nature and source of problems associated with a lightly loaded system. 4. For the light load case repeat the N-1 contingency test. How does the system behaviour compare to the normal (base case) load? Maintenance schedules which require a transmission line or transformer to be taken out of service are commonly performed at times where the system is lightly loaded. What capacity does the system have to withstand another line or transformer tripping with one element already out of service for maintenance? This represents the N-2 contingency test. Study the N-2 contingency at light load and summarise your observations. 5. In parts 2, 3 and 4 you have studied the system ability to tolerate the loss of any line or transformer, under normal and light load. Now suggest a remedial course of action, which will address the problems identified in parts 2, 3 and 4 (this may include additional infrastructure). Note that the proposed modifications have to be effective but not overly expensive. N-1 contingency has to be fully satisfied at normal load and (with additional regulations) – at light load. N-2 contingency must be “mostly” satisfied at light load, with some exemptions. For, example, some buses are allowed to be “islanded” (have no power supply) under N-2 contingency. Discuss why it is ok in some cases. Verify the effectiveness of the proposed remedial strategy for the same conditions as studied in parts 1, 2, 3 and 4. ELEC 4100 POWER SYSTEMS STUDY PROJECT-2021 2 The result of part 5 is a modified, more secure and resilient, power system. There is no single “correct answer” to this: each student may have their own solution, as long as it is sensible and justifiable. 6. Take your modified power system under normal load as the new Base Case. A new industrial client is to be connected to the system under the new Base Case scenario. The client has premises located in the vicinity of bus 26 (the distance to the client is approximately the same as between bus 25 and bus 26), and has an anticipated 33kV demand of 18 MVA at 0.8pf lagging. Plan a connection for the new load with redundancy so that the client can still be supplied even if one line feeding it is lost. What effect will the new load have on the system performance? Can the system tolerate the loss of any line or transformer under the new conditions? 7. Now investigate the anticipated growth of all loads by 50% over the next 10 years, including the newly connected client. Increase all loads in 10% (or so) steps, up to 150% of the Base Case, to observe the limiting factors that the load growth will be facing. The purpose of this exercise is to see what reinforcements and new equipment might be included in the system development plan, as consumer demand increases over time. Make up your own mind as to what reinforcements – extra line, bus, or generation – you decide to add. Their addition should be staged over the next 10 years. Examine the modified system from the viewpoint of (N-1) security. 8. Develop PV and VQ curves for the newly connected bus 27 (new industrial client). Determine real and reactive power margins. Discuss potential voltage stability issues, and suggests ways to avoid or mitigate them. 9. What is typical of real power loss in the system? Choose whatever case you wish, and see what happens to losses when fixed generation is altered. Move some generation away from bus 1 to bus 2, or add a generator at a bus elsewhere. 10. Study transient (generator angle) stability for bus 5. Find critical clearing angle, and discuss how to avoid destabilisation of the power system due to the generator angle deviations.