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  • CASE STUDY – INDIAN BASIN UTILITY INTERCONNECTION
    • JAN. 2002
  • 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
  • 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
    View slide
  • 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
    View slide
  • PLANT ELECTRICAL SYSTEM LAYOUT
  • 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
  • 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
  • GAS TURBINE GENERATION AND 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
  • DIESEL GENERATION and 4160 V SYSTEM
  • DIESEL GENERATION and 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.
  • 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
  • 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
  • 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
  • DISTRIBUTION CIRCUIT ARRESTOR OVER VOLTAGE
  • 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
  • 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
  • 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
  • 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
  • LOAD ENCROACHMENT ELEMENT
  • 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
  • UTILITY VOLTAGE NORMAL
  • UTILTIY FREQUENCY NORMAL
  • CLOSE CIRCUIT CONTROL
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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
  • EVENT REPORT WAVEFROM GRAPHIICS
  • PHASOR PLOT GRAPHICS
  • 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
  • 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