1. IMPACTS OF LARGE DISTRIBUTED GENERATORS ON CENTERPOINT ENERGY’S DISTRIBUTION SYSTEM 1 Presented by Ed Briggs, P.E. Manager of Electric Distribution Planning SWEDE Presentation May 9, 2014 CenterPoint Energy Proprietary and Confidential Information

2. SAFETY MOMENT PUBLIC AND EMPLOYEE SAFETY IS THE MOST IMPORTANT CONSIDERATION OF DG DESIGN, CONSTRUCTION AND UTILITY INTERCONNECTION ! 2

3. WHAT IS DISTRIBUTED GENERATION (DG) ? 3 Texas PUC Substantive Rule 25.211 An electric generating facility located at a customer’s point of delivery (point of common couple) of ten megawatts (MW) or less and connected at a voltage less than 60 kilovolts (kV) which may be connected in parallel operation to the utility system.

4. 4 DISTRIBUTED GENERATION BY FUEL TYPE

5. 5 Total Pending and Connected DGs Through 4/16/14

6. Large DG (7500+ KW) Statistics 6

7. WHATS DRIVING THE LARGE DISTRIBUTED GENERATION INTERCONNECTIONS? Emergency Response Service (ERS) or Demand Response Close transition-parallel with the utility grid for less than 1 second (closed transition switching) Parallel operation with power export option Parallel operation with no power export 7

8. LOAD VOLTAGE POWER FACTOR FAULT CURRENT CIRCUIT PROTECTION LATERAL FUSE COORDINATION EFFECTIVE GROUNDING RELIABILITY SAFETY 8 IMPACTS OF LARGE DISTRIBUTED GENERATION

9. DG SIZE RATING A GENERATOR NAME PLATE RATING SHOWS 2500 kVA @ 80% POWER FACTOR WHAT IS THE DG kW CAPACITY ?  2000 kW or 2500 kW ? SAME QUESTION AS ABOVE EXCEPT THE PRIME MOVER OF THE GENERATOR IS A DIESEL ENGINE RATED AT 1800kW WHAT IS THE DG kW CAPACITY ?  1800 kW or 2000 kW or 2500 kW ? 9

10. 12.47 kV DISTRIBUTION FEEDER DG STUDY 7 GENERATORS RATED AT 2500 kW EACH (7 X 2500 = 17,500 kW) PRIME MOVER DIESEL ENGINE RATED AT 1800kW ACTIVE GENERATION = 7 X 1800 = 12,600 kW 12.47 kV FEEDER RATED AT 12,960 kW DG VOLTAGE CONTROL @ 100%PF 10

11. 11 12.47kV FEEDER PEAK LOAD 10,260 kW 540 kVAR 99.9 PF DG SUB

12. DISTRIBUTIVE GENERATION SETUP (PCC IS POINT OF COMMON COUPLING) 12 Utility sourceUtility Source PCC 2 2500 kVA TRANSFORMER PCC 1 12.47 kV BUS TO SUBSTATION 2500 kW GENERATOR 480Y277V

13. DG TRIPS IF: VOLTAGE = 126V FOR 30 SECONDS VOLTAGE = 132V FOR 10 CYCLES CUSTOMER WANTS TO OPERATE DG AT 100% PF 13 DG VOLTAGE TRIP SETTING

14. CNP SUBSTATION VOLTAGE REGULATION IS SET AT 122V TO 125V FOUR CIRCUIT MODELING SENARIOS ARE:  SUMMER PEAK LOADING SUB AT 125V SUB AT 122V  OFF-PEAK LOADING SUB AT 125V SUB AT 122V 14 DG ANALYSIS

15. LOCATION AT PCC WITH SUB AT 125 V WITH SUMMER PEAK LOAD 15

16. 16 LOCATION AT PCC WITH SUB AT 122 V WITH SUMMER PEAK LOAD

17. 17 LOCATION AT PCC WITH SUB AT 125 V WITH OFF-PEAK LOAD

18. 18 LOCATION AT PCC WITH SUB AT 122 V WITH OFF-PEAK LOAD

19. 19 LOCATION AT PCC WITH SUB AT 125 V WITH SUMMER PEAK LOAD & EFFECTS OF CAPACITOR BANKS

20. 20 DG CAN REDUCE THE VOLTAGE AT PCC BUT RESULTS IN INCREASED kVAR WHICH RESULTS IN A 394 kVA DEMAND THUS A $$$$$ MONTHLY BILL

21. DURING OFF PEAK SEASON 4 DGs BACKFEEDS SUBSTATION TRANSFORMER WITH 2279 kW 21 Substation Transformer Circuits #1 #2 #3 2279 kW

22. 22 12.47kV FEEDER PEAK LOAD 10,260 kW 540 kVAR 99.9 PF DG SUB DG

23. At PCC with Sub at 125 V with Summer peak load & DG located near Sub 23

24. At PCC with Sub at 125 V with Summer peak load & DG located at end of circuit 24

25. 25 DG INCREASES CIRCUIT FAULT CURRENT AND CAUSES 100T FUSE NOT TO COORDINATE WITH 65T, MUST CHANGE LATERAL TO A FEEDER AT CUSTOMER EXPENSE Without DGs, I LG max = 2578 A With 7 DGs, I LG max = 3976 A 100 T fuse 65T fuse

26. DG ELEVATES FAULT CURRENT ON SUBSTATION BUS AND ADJACENT CIRCUITS 26  A FAULT ON ADJACENT CIRCUIT WILL BE FED BY DG CIRCUIT AND MAY RESULT IN TWO CIRCUITS OPERATING THUS IMPACTING RELIABILITY  LATERAL FUSE COORDINATION WILL NEED TO BE ASSESSED ON ADJACENT CIRCUITS DUE TO HIGHER FAULT CURRENT

27. Line to Ground Fault Currents 27

28. EFFECTIVELY GROUNDED SYSTEM PER IEEE STANDARD 142 28

29. EFFECTIVELY GROUNDED SYSTEM CHECK ? CUSTOMER’S HIGHSIDE RESISTIVE GROUNDING 24 OHM ON 12.47kV SIDE OF THE TRANSFORMER 29

30. CNP REQUIRES TRANSFER TRIP FOR DGs OVER 2000 kW. HOWEVER CIRCUIT SWITCHING CAN SCUTTLE THIS 30 Sub 1Sub 2 DG N.C.N.O. (TIE) N.C. Utility crew opens the N.C. switch Utility crew closes the tie switch DG will be transferred from a feeder from sub 1 to another feeder from sub 2 Lateral

31. SWEDE 2015 NEXT YEAR’S PRESENTATION DG ACTUAL DATA VERSUS MODELED THANK YOU ! 31

32. NEXT YEAR DG ACTUAL VERSUS MODELED THANK YOU ! 32 Any Questions ?