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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
    • 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
    • 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