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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