CASE STUDY – INDIAN BASIN UTILITY INTERCONNECTION

1. CASE STUDY – INDIAN BASIN UTILITY INTERCONNECTION JAN. 2002

2. INDIAN BASIN GAS PLANT • Marathon Oil Co. Gas Processing Plant • Five Synchronous Generators Totaling 3.48MVA • Gas Turbine and Diesel Driven Equipment • No Export Agreement with Utility

3. INTERCONNECTION BENEFITS • Utility Provides a Source Instantaneous Energy when needed, Increasing Plant Electrical Reliability • Plant Operating Costs are Reduced by Using Fuels from Process • On-Site Generation can Maintain Critical Operations when Utility source is Unavailable, Creating Electrical Supply Redundancy

4. CASE STUDY CONTENT • Utility Interconnection and Interconnection Protection and Control • Directional Overcurrent Protection Improves Plant Protection Selectivity • Techniques used to Monitor Protection Quality • Logical Next Steps and Conclusions

5. PLANT ELECTRICAL SYSTEM LAYOUT

6. UTILITY SOURCE AND POINT OF COMMON COUPLING (PCC) • PCC resides at the low side of the 12470 – 480vac 1000 kva transformer • 1600 A, 480 V Circuit Breaker #352 Interconnect breaker • 480 V Plant Bus Feeds Critical Plant Loads

7. INTERCONNECTION EQUIPMENT • PCC resides at the low side of the 12470 – 480vac 1000 kva transformer • 1600 A, 480 V Circuit Breaker #352 Interconnect breaker to Plant 480 V Bus • 480 V Plant Bus Feeds Critical Plant Loads

8. GAS TURBINE GENERATIONAND CRITICAL PLANT LOADS • Three 800Kw 0.8 Power Factor Generators Feed the Plant 480 V Bus • Automatic Load and Var Controls • The Plant Electrical System is Predominantly High Resistance Grounded • 480 V Plant Bus Feeds Critical Motor Control Centers, Process Loads and Building Loads

9. DIESEL GENERATION and 4160 V SYSTEM

10. DIESEL GENERATIONand 4160 V PLANT LOADS • Two 540Kw 0.8 Power Factor Generators Feed the Plant 4160 V System • Fixed Load and Voltage Regulations Controls • The 4160 V Plant Electrical System is Predominantly High Resistance Grounded • 4160 V System Feeds Two Large Motors and Small Process Loads.

11. ELECTRICAL SYSTEM TIE EQUIPMENT • 480 – 4160 V 1500 kva Transformer Connects the 480 V and 4160 V Systems • 1600 A, 480 V Circuit Breaker #552 Tie breaker • 4160 V Plant Bus Feeds Large Motor Loads

12. UTILITY SOURCE TRANSFORMER CONNECTION • Utility Advantages of the Ground Wye High Side Configuration • Utility distribution system remains solidly grounded even if plant generation feeds the distribution circuit • Utility Advantages of the Delta Low Side Configuration • Zero Sequence Isolation, no ground fault contribution from plant generation

13. UTILITY SOURCE TRANSFORMER CONNECTION • Plant Advantages of Grounded Wye High Side Configuration • Plant generation does cause utility distribution circuit arrestor damage during short periods of back feed • Plant Advantages of Delta Low Side Configuration • Zero sequence isolation, plant can operate with a High Resistance Grounded (HRG) system

14. DISTRIBUTION CIRCUIT ARRESTOR OVER VOLTAGE

15. UTILITY INTERCONNECTION PROTECTION • The SEL-351 Multifunction Microprocessor Relay • Protection and control • Event and sequential event reports • Programmable display messaging • Failsafe Alarm Contact Provides System Status

16. VOLTAGE PROTECTION ELEMENTS • Single Level Over Voltage and Under Voltage Protection • Under voltage protection set at 94% of nominal with 120 cycle delay • Over voltage protection set at 132% of nominal with 120 cycle delay • System Utilizes Open Delta Connected Potentials

17. FREQUENCY PROTECTION ELEMENTS • Single Level Definite Time Over and Under Frequency Protection • Under frequency set at 59.25 Hz with five cycle delay • Over frequency set at 60.25 Hz with five cycle delay • Under Voltage Frequency Disable Set at 40 V

18. ISLANDING PROTECTION ELEMENT • Load Encroachment Element • Detects load flow to the utility via positive sequence impedance calculations • Detects three-phase reverse power flow as small as 125 Kw • Reverse power time delay of four seconds allows plant generation control time to compensate after a load shed occurs

19. LOAD ENCROACHMENT ELEMENT

20. RECOMMENDED ENHANCEMENTS • Inadvertent Energization of the Utility Distribution System • Programmable close interlock contact to prevent #352 interconnect breaker closing if distribution system is de-energized • Use SEL-351 check synch element as an additional layer for out of synch close protection

21. UTILITY VOLTAGE NORMAL

22. UTILTIY FREQUENCY NORMAL

23. CLOSE CIRCUIT CONTROL

24. PROTECTION SYSTEM MONITORING • Utilize Loss of Potential Indication to Operate Protection System Abnormal Alarm Contact • Control Protection Element Operation with Loss of Potential Status if Interconnection is Critical

25. PLANT DISTRIBUTION 480-4160V TIE PROTECTION • SEL-351 Multi-Function Microprocessor Relay • Provide Fast Low Set Overcurrent Protection • Not sensitive to loading • Secure for disturbances on the utility feeder • Additional Overcurrent Protection for Balanced Fault Conditions • Less sensitive and secure during motor starting operations on the 4160 vac system

26. FAST LOW SET PROTECTION • Definite Time Directional Negative Sequence Element • Operates for unbalance faults on the 4160V system • Two cycle definite time delay avoids tripping on negative sequence transients

27. BALANCED FAULT PROTECTION • Set Above Load and Motor Starting Inrush • High set non-directional definite time overcurrent • Non-directional extremely inverse time over current element • This Combination Operates During Balanced Fault Conditions and is Secure During Motor Starting Inrush

28. ADVANTAGES OF TIE PROTECTION SYSTEM • Closed Tie Continuity • For unbalanced disturbances on the utility distribution system • For motor starting operations on the 4160V system • Fast Clearing of Unbalanced Faults on the 4160V System Minimizes Effects to the 480V Plant Bus

29. RECOMMENDED ENHANCEMENTS TO TIE PROTECTION • Use SEL-351 check synch element as an additional layer for out of synch close protection • Utilize Loss of Potential Indication to Operate Protection System Abnormal Alarm Contact • Control Protection Element Operation with Loss of Potential Status

30. PROTECTION QUALITY MEASUREMENTS • Sequential Event Reports • Time tagged protection system element status report • Unused levels of over current protection used for monitoring via sequential event reports • Unused levels of over current protection are not programmed for tripping

31. EVENT ANALYSIS • Event Reports Capture System Disturbances • Provide greater detail with pre and post fault data • Graphical representations of voltage and current waveforms along with frequency magnitudes • Protection system element status time synchronized with voltage and current waveforms • Phasor plots of voltage current and sequence quantities

32. EVENT REPORT WAVEFROM GRAPHIICS

33. PHASOR PLOT GRAPHICS

34. DISPLAY MESSAGING • Protection System Display Messaging • Add descriptive text into rotating display based on protection element status • Enhances protection system targeting • Provides additional information to operating personnel

35. CONCLUSIONS • Multi-functional Microprocessor Relays are Well Suited for Interconnection Protection • Interconnection Protection • Over and Under Frequency Elements • Over and Under Voltage Elements • Non-Islanding Protection • Close Interlock Control • Monitor Protection System Performance