1. Sean A. Kufel, P.E. Power System Engineering, Inc. April 20, 2015 Distributed Generation System Impact Analysis with Computer Modeling Tools IEEE Rural Electric Power Conference www.powersystem.org

2. © 2015 Power System Engineering, Inc. Session Summary Goal: Developing a reliable, efficient process for performing DG system impact studies. Data Requirements Modeling Generation –Types of generator models & adding generation –Types of analysis –Common modeling errors Focus on steps where errors or confusion are common NOT: Instructions on using any modeling program DISCLAIMER(S): I am not a programmer. I am not endorsing any particular modeling application. 2

3. © 2015 Power System Engineering, Inc. System Impact Analysis Goals Common impacts of DG that can be identified with computer modeling: Voltage rise Conductor/equipment overload Inadequate device interrupt rating Reverse power flow Potential for islanding 3

4. © 2015 Power System Engineering, Inc. Data Requirements Utility side: –Electrical model of distribution system area where DG is proposed, including: Source impedance, including substation power transformer System conductors Major system equipment – transformers, regulators, capacitors & protective devices Substation area/feeder peak demand –Historical minimum load in area/on feeder Often estimated at around 25% of peak if historical hourly data is not available –Protective device settings –Regulator/LTC settings 4

5. © 2015 Power System Engineering, Inc. Data Requirements Applicant/Developer/Generation side: –Number of generators to be installed and total aggregate capacity –Proposed facility one-line/three-line diagram –Expected peak generator output & how the generation will be used (back-up only, intermittent operation, on-site load service, power export, etc.) –Location of proposed interconnection (preferably in reference to distribution system) 5

6. © 2015 Power System Engineering, Inc. Data Requirements Applicant/Developer/Generation side: –Generator data: Operating voltage Ratings: kW, kVA, power factor Fault information –Steady-state, transient & subtransient reactance values or generator equivalent circuit for rotating machines –For PV with inverter(s), fault current is typically a multiple of rated output (150% is often used) –Other equipment data: Inverter ratings, solar panel data for PV installations Ratings & impedances of any generator step-up transformer units (GSU) 6

7. © 2015 Power System Engineering, Inc. Impedance DataEquivalent Circuit Generator Fault Information 7

8. © 2015 Power System Engineering, Inc. Milsoft WindMil®Eaton CYME Modeling Programs 8 SynerGEE, eTap, Dapper, etc.

9. © 2015 Power System Engineering, Inc. Types of Generator Models Generic Generator Two operating modes: –Negative load (constant kW output) –Swing kVAR (hold desired voltage by adjusting kVAR output) Fault output based on generator impedances 9

10. © 2015 Power System Engineering, Inc. Types of Generator Models Specific GeneratorsCommon types: –Synchronous & Induction –Wind turbine –Solar array –Others Operating modes & fault contributions dependent upon type of generation Mostly the same as generic for synchronous machines 10

11. © 2015 Power System Engineering, Inc. Generic Generator Pros/Cons Con: –Sometimes need to perform impedance calculations when only fault duty is available Pro: –Conversion utilities are often built in 11

12. © 2015 Power System Engineering, Inc. Pro: Possible to create extremely detailed generator models with LOTS of specific data Possible (?) to run highly specific analysis depending upon program modules & capabilities Con: Hyper-specific data generally not needed for snapshot analysis Lots of specific data can be overwhelming Specific Generator Pros/Cons 12

13. © 2015 Power System Engineering, Inc. Information Overload? 13

14. © 2015 Power System Engineering, Inc. Add Generation to the Model 14

15. © 2015 Power System Engineering, Inc. Peak LoadMinimum Load Voltage Drop/Load Flow Analysis 15

16. © 2015 Power System Engineering, Inc. Common Error: Generators not included in analysis Voltage Drop/Load Flow Analysis 16

17. © 2015 Power System Engineering, Inc. Collecting Results From on-screen result boxes: 17

18. © 2015 Power System Engineering, Inc. Collecting Results Via custom reports: 18

19. © 2015 Power System Engineering, Inc. Voltage Drop/Load Flow Analysis Other things to check: –Substation/source power factor, before & after generation is added –Native loads in all protective zones upline of the generation (with generation offline) Aid in determining if islanding is possible –Current flow through equipment with generation online –Reverse power flow through equipment and/or substations when generation is operating (more likely and higher at minimum load) 19

20. © 2015 Power System Engineering, Inc. Checking Protective Zone Loads 20

21. © 2015 Power System Engineering, Inc. Turning on Power Flow Arrows (If Available) 21

22. © 2015 Power System Engineering, Inc. Short-Circuit Analysis 22

23. © 2015 Power System Engineering, Inc. Gen Z: Steady-state or “None”Gen Z: Subtransient Short-Circuit Analysis: General 23

24. © 2015 Power System Engineering, Inc. Coordination Analysis 24

25. © 2015 Power System Engineering, Inc. CYME TCC Settings  Device Coordination Check Device-Device Coordination Setup 25

26. © 2015 Power System Engineering, Inc. GeneratorFeeder Recloser Short-Circuit Analysis: Fault Flow 26 End of Protective Zone 1

27. © 2015 Power System Engineering, Inc. Short-Circuit: Reverse Fault Flow 27 Initiate fault immediately upline of protective device

28. © 2015 Power System Engineering, Inc. Short-Circuit: Fault Flow Locations to check during fault flow: –End of protective device zones Especially in direct path between generation and source Especially for electronically-controlled reclosers –Check ground pickup setting versus minimum fault flowing through device with generation contributing –Source side of devices in direct path between generation and source –Other feeders on substation 28

29. © 2015 Power System Engineering, Inc. System Impact Study Model Use Keys Develop a process and stick to it Double-check entered data Document analysis results clearly Keep track of model changes made to improve system conditions –Probably not a good idea to alter the working model of your existing system if you are a utility, especially if it is an enterprise or shared model Step back and sanity-check results 29

30. © 2015 Power System Engineering, Inc. 30 QUESTIONS & DISCUSSION

31. © 2015 Power System Engineering, Inc. 31 Power System Engineering, Inc. Name: Sean A. Kufel, P.E. Title: Electrical Engineer Direct: (740) 568-9220 x11 Mobile: (216) 544-8614 Email: kufels@powersystem.org www.powersystem.org Thank You: IEEE 2015 REPC Attendees!