sfra typical results v1

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    Together We Power

    The World

    SFRA Training

    Typical Results

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    SFRA Typical Results

    This presentation gives typical results fordifferent transformer windings and

    configurations.

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    SFRA Typical Results

    Wye-wye transformer (delta-delta)

    Delta-wye transformer (delta-star)

    Measurement Sense (H1-H0 v H0-H1)Variation due to LTC

    Effect of LTC Reversing Switch

    Variation due to DETC

    Effect of Oil results with and without

    Effects of Poor Grounding

    Effect of Magnetization

    Sister UnitsShort Circuit Tests

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    Wye-wye : HVs

    Note low frequency variations

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    Wye-wye: LVs

    Less dB down than HV

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    Wye-wye HV Short Circuit

    LV windings shorted

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    Another HV Wye

    HV winding three phases one DETC positions

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    Another HV Wye

    Detail three phases

    Center phaseTwo outer

    phases

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    Another HV Wye

    Detail three phases

    Center phase

    Two outer

    phases

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    Delta-wye HVs

    Typical response at low frequencies

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    Delta-Wye: LVs

    Less dB down than HV

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    Delta-Wye HV Short Circuit

    LV windings shorted together

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    Another Delta-Wye HV

    Note low frequency shape low MVA

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    Autotransformer HV

    HV Open Circuit

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    Autotransformer LV

    LV (common) winding typical result

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    Autotransformer tertiary

    Tertiary Open Circuit

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    Autotransformer HV

    HV LV and Tertiary compared

    HV (series) winding

    Tertiary winding

    LV (common) winding

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    Measurement Sense: H1-H0 v. H0-H1

    Effect is smaller when the two bushings are

    similar e.g. H1-H3 v H3-H1

    H0-H1

    H1-H0

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    Variation with LTC position

    16 Lower through 8 Lower for one winding

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    Variation with LTC position

    Low frequency detail

    16 Lower

    8 Lower

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    Variation with LTC position

    Mid frequency detail

    16 Lower

    8 Lower

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    Variation with LTC position

    High frequency tap position variation

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    Variation with Reversing Switch position

    One winding neutral from raise & lower

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    Variation with DETC position

    HV winding one phase three DETC positions

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    Variation with DETC position

    Low frequency detail

    Position A Position E

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    Variation with DETC position

    Low frequency detail

    Position A Position E

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    Variation with DETC position

    High frequency detail

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    Variation with and without oil

    LV winding

    With oil

    Lower

    resonant

    frequencies

    Without oil

    Higher

    resonant

    frequencies

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    Effect of Bad grounds

    Original and Bad Red lead ground

    Original

    Bad red lead

    ground

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    Effect of Bad grounds

    Original and Bad Black lead ground

    Original

    Bad red lead

    ground

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    Effect of Bad grounds

    Original and Bad Red & Black lead grounds

    Original

    Bad red and black

    lead grounds

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    Effect of Magnetization

    Low frequency variation is severe but identifiable

    Magnetization affects thecore response

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    Magnetization & Grounding variation

    HV winding

    High frequency variationdue to grounding

    Magnetization affects the

    core response

    Magnetized center phase

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    Sister Units showing Magnetization

    HV winding

    Magnetization variation

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    Sister Units showing Magnetization

    HV winding same unit, more magnetization

    Magnetization variation

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    HV Wye winding: Open and Short

    HV winding same unit, more magnetization

    Open circuit wye windingVery similar at high

    frequencies

    Short circuit wye winding

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    HV Delta winding: Open and Short

    HV winding same unit, more magnetization

    Open Circuit Similar at high

    frequencies

    Short Circuit

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    Typical Results - Conclusions

    Results vary between units depending onsize and type of unit

    Results vary with magnetization &grounding

    Results vary with tap changer positions Results vary with oil level

    Know what to expect see next slide!!!

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    One Transformer: HV, LV, SC & IW

    IW = Interwinding measurement

    HV Open Circuit

    H-X interwinding

    Short Circuit

    LV Open Circuit

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