My Time in CURENT

1. My Time in CURENT Graham Treasure

2. Quick Recap • First semester • Electrical theory • Introduction to programming • I already gave this talk • Second Semester • Applications of knowledge from first semester • I will focus on this

3. Power Systems • Consists of generators, loads, buses, and lines • 3 Types of Buses • Swing Bus (Vθ) • Generator Bus (PQ) • Load Bus (PV) • 4 Variables; but with a combination of buses, we can still obtain all of them

4. 4 Bus System from book ‘Power System Analysis’, John J. Grainger

5. Power Flow Calculation • First, I learned to do it in Matlab using Power Systems Toolbox • This involves intensive tabulation of data • Next, I learned to draw it as a one line diagram in PSAT

6. 9 Bus System

7. Dynamic Simulation • How a power system responds to a fault • We used three types • Line Fault • Bus Fault • Generator Trip • This helps us find ways to improve power system stability. • Right now, we just simulated the response.

8. Line/Bus Fault • These occur when a line or bus becomes grounded • No change in generation/load • System returns to its original state after the fault is cleared • Faults generally do not last longer than five cycles (<0.1s) due to protection relays

9. Generator Trip • This occurs when a generator goes offline • Overload, inspection, or just turned off • Unlike bus/line faults, the system does not return to its original state • Frequency oscillates until its new state • Generator Trip vs. Load Shedding

10. Electric Physics • Power and Voltage relation • Once the limit is reached, the line trips and the whole system crashes • Leading to blackouts like the Northeast Blackout of 2003 • Thus, we need to know the maximum load available at the load buses.

11. Main Project • Given the 39 Bus New England Power System, determine which bus (in the Connecticut area is the most vulnerable.) This area is a load center, so any system crash will likely be on buses 4, 7, 8, 12, 31 (attached to 6)

12. How • Start with the loadflow file of this system • Alter the load for one bus • Run a powerflow calculation • ^^ All this can be recorded in Python and redone by simply altering and rerunning the program. • Raise the load on the bus until the system diverges. • Then go back and forth until divergence is found within a 10 MW range

13. Main Project • Simulations on PSSE for Buses

14. WHY? • When load in a system is increased, it generally affects the loads in proportion to the original voltage. • SO to find the most vulnerable bus, we must increase the loads on all the buses in the system. The previous tests can give us a good starting point.

15. New Simulations • Increased load in increments • Per unit voltage can be determined in a loadflow calculation

16. Data As you can guess, copy and paste came in real handy.

17. Data

18. Pop Quiz: Why didn’t all of the voltages drop?

19. Answer: Someare generator buses! In power flow, the voltages of the generators are fixed. Not always the case in dynamics

20. Conclusion • When the power flow of the system increases, we should watch bus 31, as it has the lowest load limit. • This does not mean other should be ignored • Loads can vary independently, so another bus may reach its limit first • This is based on a constant PQ load model. Thus, it is a preliminary test. The load may be modeled by current, impedance, induction motor, or a combination of them.