tony o'brien - australian winders

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  • Australian Winders

    Kwinana CASE STUDY, May 2014

  • Australian Winders

  • Australian Winders

  • Australian Winders

    PROGRESSIVE MEASURABLE

    INCREASE IN PD LEVELS.

    SLOT DISCHARGE

    DEGRADATION OF STRESS RELIEFCOATINGS IN SLOT SECTION AREA

    SLOT EXIT AT THE JOINT OFSLOT SEMI-CONDUCTIVE LAYER ANDGRADING LAYER

    NO INDICATION OF MAJORGROUNDWALL INSULATIONDEGRADATION

  • Australian Winders

  • Australian Winders

  • Australian Winders

  • Australian Winders

  • Australian Winders

    Slot 31 had no corona

    protection left!

  • PLEASE NOTE SLOT #6 CE

    Australian Winders

  • Australian Winders

  • Australian Winders

  • PLEASE NOTE SLOT #6 CE

    Australian Winders

  • Australian Winders

  • Australian Winders

  • Australian Winders

  • STATOR WINDING LEADS INVERSION

    Purpose: The Highest Gradient Across the Stator Ground Wall Insulation (Line to Ground Voltage)

    is At The Main Output High Voltage (HV) Lead End. Thus the HV Winding Side Incurs the Highest In-Service PD Degradation (Internally and Externally)

    The Lowest Dielectric Gradient Across the Stator Ground Wall Insulation Occurs at the Neutral End of the Winding. The Neutral Winding End Is Unaffected by the PD Damage

    By Reversing/Inverting Stator Leads (Active Side and Neutral Side), the Neutral Side which is Not Affected by PD Erosion is Now Connected to the HV Output Side. The Bars that were Previously Connected to the HV Side are Now Exposed to Very Low Voltage Stresses and are not Expected to Incur Further PD Degradation

    By Stator Winding Leads Inversion it is Possible to Appreciably Extend the Winding Life by Shifting Weaker Degraded Coils Near the Neutral End Under Lower Dielectric Stress

    Stator Leads Inversion Can Only Mitigate and Prolong Winding Life Due to PD Damage, and Before Embarking on the Lead Reversal, it is, of Course, Necessary to Fully Assess Stator Winding Condition Due to Other Degradation Mechanisms (Thermal, Mechanical and Environmental)

  • STATOR WINDING LEADS INVERSION

    Stator Winding Voltage Division: The Voltage to Ground Along Stator Phase Winding Divides Linearly from Full Voltage

    to Ground at Phase Terminals (Vph), to Zero Volts to Ground at Star Point as Depicted Below

  • STATOR WINDING LEADS INVERSION

    Lead Inversion Design: Design and Design Coordination was Done by

    GMECS (Dr. Michael Znidarich Director Electrical Machinery Consultant)

    3D Modelling and Drafting was Done by Owners Contractor D.A.K. Systems (David Knowling Owner)

    Manufacturing and Installation was Done byAustralian Winders (Tony OBrien - Managing Director/Owner)

  • STATOR WINDING LEADS INVERSION

    Design and Installation: Given Previous Failed Experience of OEM

    Attempting to Fit Inversion Leads on Sister Unit Under Incorrect Assumption the Stator Leads are Located Exactly as Per Original Design/Drawings, Following Design and Installation Strategy was Adopted:

    Design Inversion Leads with Site Fitting Allowance

    Site Trial Fit Inversion Leads and FinallyBraze Leads Connections In Situ

    Remove Inversion Leads, Transport to the Australian Winders Workshop and Insulate

    Finally Fit Inversion Leads, Brace, Blockand Insulate Connections

  • STATOR WINDING LEADS INVERSION

    Installation:

  • FINAL STATOR WINDING OFF-LINE PD TESTS

    Final Off-Line PD Test Results:

    The Final (as Left) Stator Winding Off-Line PD Tests were Carried Using Both Lower Frequency Band (100-800 kHZ) and Higher Frequency Band (2-20 MHZ). These Tests Provided an Indication of Effectiveness of Corona System Repairs, but not the Operational PD Reduction Contributed by the Inversion Leads

    In Every Case there was Significant Reduction in Off-Line PD Magnitudes, Signifying Good Success of Stator Winding PD Repairs

  • FINAL STATOR WINDING OFF-LINE PD TESTS

    Graphical Comparison of Off-Line PD Test Results:

  • ON-LINE PD TESTING FOLLOWING RETURN TO

    SERVICE

    On Line PD Test Results:

    The First On-Line Stator Winding PD Tests were Carried Immediately Post Refurbishment and Fitting of Inversion Leads Using Both Lower Frequency Band (100-800 kHZ) and Higher Frequency Band (2-20 MHZ), and Compared to the Test Results of Periodic On-Line PD Monitoring Obtained Before Repairs.

    When Using Low Frequency Band (100 800 kHZ), there was no PD Signal Detectable Above Background Interference.

    When Using High Frequency Band (2 20 MHZ) Phases U and V were Virtually PD Free, and Magnitude of PD Discharge for Phase W was Significantly Reduced

  • ON-LINE PD TESTING FOLLOWING RETURN TO

    SERVICEComparison of On Line PD Test Results (March 2014 Before Repairs and Leads Inversion) andNovember 2014 (Following Repairs and Leads Inversion):

  • CONCLUSION

    It Can be Concluded that Both,Applied PD Repair Strategies, and Application of Stator Phase/Neutral Inversion Leads Combined, Contributed to Significant Reduction in PD Activity and Extension of Stator Winding Operational LifeProject was completed 4 days ahead of schedule, with no LTIs