testing and commissioning instrument-transformers
TRANSCRIPT
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
Primary Ins. Resistance Test
For Bar and Primary wound
CTs
DC voltage test at the ratedcrest voltage on the primary
winding
Secondary grounded
1 minute test
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TESTING INSTRUMENT
TRANSFORMERSCT Insulation Resistance: Bar Type and Primary Wound
DC Voltage test
Isolate Primary
Isolate & Gnd Secondary
Connect HV lead to H1/H2
Connect LV to Gnd /
2ndary
Test for 1 minute Record test value
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
Dielectric Withstand Test
For Bar and Primary wound
CTs
AC voltage test at the 75%factory test voltage
Secondary grounded
1 minute test
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TESTING INSTRUMENT
TRANSFORMERSCT Dielectric Withstand: Bar Type and Primary Wound
AC Voltage test
Isolate & Gnd Secondary
Connect HV lead to H1/H2
Connect LV to Gnd /
2ndary
Test for 1 minute
Record test value
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
2ndary Ins. Resistance Test
Test for secondary wiring
Secondary wiring isolated
and ungrounded 1000 VDC
1 minute test
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TESTING INSTRUMENT
TRANSFORMERSCT Secondary Circuit Insulation Test
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
2ndary Burden Test
Conducted in 2 parts
Part 1, 1A current injection
Measure circuit burden Part 2, four-wire resistance
measurement
Measure secondary
winding resistance Burden = part 1 + part 2
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TESTING INSTRUMENT
TRANSFORMERSPart 1: CT Secondary Circuit Burden Measurement
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TESTING INSTRUMENT
TRANSFORMERSPart 2: CT Secondary Winding Resistance Measurement
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TESTING INSTRUMENT
TRANSFORMERS
Total burden calculation
ZT = RCT + (RL + ZB)
WhereZT = Total burden ()
RCT = DC Winding resistance ()
RL = Lead resistance ()ZB = Device impedance ()
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
Saturation Test
Secondary winding excitation
test
Primary open circuited Step voltage increase,
current proportional
Test for knee-point voltage
Rapid rise is I-excitation 10% V = 50% I
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TESTING INSTRUMENT
TRANSFORMERSCT Saturation test
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
Ratio and Polarity test
Secondary winding excited at
1V per turn
Primary open circuited H1-H2 compared to X1-X2
Phase measured, ratio
calculated
Phase difference 0 meanspolarity correct
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TESTING INSTRUMENT
TRANSFORMERSCT Ratio and Polarity Test
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TESTING INSTRUMENT
TRANSFORMERS
CT Testing
Primary Insulation
Resistance
Dielectric Withstand Secondary Insulation
Resistance
Secondary Burden
Saturation Ratio and Polarity
Ratio and Polarity test (ALT)
Use individual meters, phase
angle and voltmeter
Secondary winding excited at1V per turn
Primary open circuited
H1-H2 compared to X1-X2
Phase measured, ratiocalculated
Phase difference 0 means
polarity correct
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TESTING INSTRUMENT
TRANSFORMERSCT Ratio and Polarity Test (alternate connections)
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TESTING INSTRUMENT
TRANSFORMERS
VT Testing
Insulation Resistance
Dielectric Withstand
Ratio and Polarity
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TESTING INSTRUMENT
TRANSFORMERS
VT Testing
Insulation Resistance
Dielectric Withstand
Ratio and Polarity
Insulation Resistance Test
DC voltage test at the rated
crest voltage
3 tests HV to Gnd
HV to LV
LV to Gnd
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TESTING INSTRUMENT
TRANSFORMERSVT Insulation Resistance Tests
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TESTING INSTRUMENT
TRANSFORMERS
VT Testing
Insulation Resistance
Dielectric Withstand
Ratio and Polarity
Dielectric Withstand Test
AC voltage test at the 75%
factory test voltage
Secondary grounded 1 minute test
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TESTING INSTRUMENT
TRANSFORMERSVT Dielectric Withstand Tests
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TESTING INSTRUMENT
TRANSFORMERS
VT Testing
Insulation Resistance
Dielectric Withstand
Ratio and Polarity
Ratio and Polarity test
Primary winding excited at
1V per turns ratio
Secondary open circuited X1-X2 compared to H1-H2
Phase measured, ratio
calculated
Phase difference 0 meanspolarity correct
Compare ratio with
nameplate
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NETA STANDARD
5. NETA Acceptance Testing Procedure
5.1 Visual and Mechanical Inspection
5.2 Electrical Test 5.2.1 Current Transformer
5.2.2 Voltage Transformer
5.3 Test Value Analysis 5.3.1 Visual and Mechanical
5.3.2 CT Electrical Test
5.3.3 VT Electrical Test
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TEST SET MANUAL
Module 3:
CT Tester
Module 2:
15 KV Insulation Resistance Test set
AC High Potential Test set
DC High Potential Test set
Digital Low Resistance Test set
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TEST FORMS
Current Transformer Test Form
Voltage Transformer Test Form
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