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© 2019 Caterpillar and SEL Compensator Ground Fault Coverage Through a Delta-Wye Transformer – A Case Study Dustin Hohenbery Caterpillar Ryan McDaniel, Harish Chaluvadi, and Michael J. Thompson Schweitzer Engineering Laboratories, Inc.

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  • © 2019 Caterpillar and SEL

    Compensator Ground Fault Coverage Through a Delta-Wye Transformer –

    A Case Study

    Dustin HohenberyCaterpillar

    Ryan McDaniel, Harish Chaluvadi, and Michael J. ThompsonSchweitzer Engineering Laboratories, Inc.

  • • Case study• Initial analysis• Dynamic compensator characteristic• Transformer connection effects on distance elements• Case study using dynamic compensator characteristic• Summary

    Overview

  • • Ground fault on Line L1

    • Breaker 1 relay trips

    • Breaker A relay does not trip

    • BT trips

    Case Study Overview

    B

    Main B Relay

    Bus-Tie RelayA

    Main A Relay

    13

    4

    Utility Sub X Utility Sub Y

    2

    Line L1

    Line L2

    Line L2Line L1

    Bus BBus A

    51N51

    21C51 51N21C51 51N

    BT

  • Breaker 1 Event Report

  • Breaker A Event Report

  • Initial Compensator Distance Analysis

    PPCOMP AB AB R

    PPCOMP BC BC R*

    TORQUE

    S1 V I • Z1S2 V I • Z1

    PPCOMP IM • (S1• S2 )

    = −

    = −

    =

    PPCOMPTORQUE

    Reach

    VA

    PPCOMP Balance

    0 10 20 30 40 50 60

    8000600040002000

    0–2000–4000–6000–8000

  • Initial Mho Distance Analysis

    PPMHO(SELF) PP PP R

    PPMHO(SELF) PP

    *TORQUE

    S1 V I • Z1

    S2 V

    PPMHO(SELF) RE • (S1• S2 )

    = −

    =

    =

    MHO(SELF) Torque

    Reach

    VA

    MHO(BC) BalanceMHO(CA)MHO(AB)

    15000100005000

    0-5000

    –10000–15000–20000–25000–30000

    0 10 20 30 40 50 60

  • • Compensator includes two relays Three-phase relay (3PCOMP)

    Phase-to-phase relay (PPCOMP)

    • PPCOMP evaluates V1 / V2 at relay reach point

    Compensator Review

    R R R

    R R R

    V1 I1 • Z1 V1C= = 1< V2 I2 • Z1 V2C

    −θ

  • Compensator PerformanceEvaluate Without and With Transformer (YD11)

    Z1S Z1RZ1L

    ES ER

    S R

    Z1R

    Fault Point

    Z1S Z1R

    ES ER

    S R

    Z1R

    Fault Point

    Z1L

  • Dynamic Compensator CharacteristicBC Fault With No Transformer

    PPCOMPMHO(BC)MEM

  • Dynamic Compensator CharacteristicBC Fault With Transformer

    PPCOMPMHO(BC)MEM

  • Dynamic Compensator CharacteristicBCG Fault

    PPCOMPMHO(BC)MEM

    No transformer With transformer

  • Dynamic Compensator CharacteristicBCG Fault With Transformer

    PPCOMPMHO(BC)MEM3PCOMP

  • Dynamic Compensator CharacteristicCG Fault With Transformer

    PPCOMPMHO(BC)MEM3PCOMP

  • Dynamic Compensator CharacteristicFault With Transformer

    BCG fault – no load CG fault – heavy load

    PPCOMPMHO(BC)MEM3PCOMP

  • Revisit Case Study

    PPCOMPMHO(BC)MEM3PCOMP

  • Revisit Case Study

    MHO(PP)COMP

  • • PPCOMP offers unreliable performance for close-in ground faults, including PPG

    • Excessively long reach settings hinder performance• Lines with tapped loads require special attention• Compensated mho elements offer more reliability for

    close-in ground faults through a transformer

    Summary

  • Dynamic Compensator CharacteristicBC Fault With No Transformer

    PPCOMPMHO(BC)MEM

    Compensator Ground Fault Coverage Through a Delta-Wye Transformer – �A Case StudyOverviewCase Study OverviewBreaker 1 Event ReportBreaker A Event ReportInitial Compensator Distance AnalysisInitial Mho Distance AnalysisCompensator ReviewCompensator Performance�Evaluate Without and With Transformer (YD11) Dynamic Compensator Characteristic�BC Fault With No TransformerDynamic Compensator Characteristic�BC Fault With TransformerDynamic Compensator Characteristic�BCG FaultDynamic Compensator Characteristic�BCG Fault With TransformerDynamic Compensator Characteristic�CG Fault With TransformerDynamic Compensator Characteristic�Fault With TransformerRevisit Case StudyRevisit Case StudySummaryDynamic Compensator Characteristic�BC Fault With No Transformer