Testing Ppt[1]

TESTING OF INSTRUMENT TRANSFORMERS

Presented by: M.Sayusha

CLASSIFICATION OF INSTRUMENT TRANSFORMERS



CURRENT

TRANSFORMERS



VOLTAGE TRANSFORMERS

CLASSIFICATION

OF

CT¶S

AND VT¶S

 Measuring Transformers  Protective Transformers  Special protection Transformers

TYPES OF TESTS Routine Tests Type Tests Special Tests Acceptance Tests

APPLICABLE STANDARDS Current

Transformers  IS 2705  IEC 60044-1 Voltage Transformers  IS 3156  IEC 60044-2

ROUTINE TESTS ON

CT¶S

 Accuracy Test  Composite Error measurement on Protection core  Exciting current measurement  Overvoltage interturn test  Power frequency dry withstand test on primary windings  Power frequency dry withstand test on secondary windings  Partial discharge measurement  Terminal marking and polarity

ACCURACY TEST

 Ratio Error(%)  Phase Angle Error(min) Measuring current transformers  Standard Accuracy classes are: 0.1,0.2,0.5,1,3 and 5

Protective

Current

Transformers

 Standard Accuracy Classes are: 5P,10P and 15P Special Protection Current Transformers  Turns Ratio Error (%) Actual turns ratio-Rated turns ratiox100 Rated turns ratio

Connection

Primary Injection

Diagram

Standard

CT

Measuring

CT

Secondary o/p

Accuracy Measurement

Burden

COMPOSITE

ERROR MEASUREMENT

 Composite error  Exciting current  Accuracy limit factor  Secondary Limiting Voltage(SLV) SLV=ALFxIs(VA/Is2+RCT)  Composite error in % Iex100/ALFxIs

Connection

Auto Transformer

Diagram

Ammeter CT

Voltmeter

Under Test

EXCITING CURRENT MEASUREMENT  Knee Point Voltage Auto Transformer

Ammeter

Voltmeter

Test CT

OVERVOLTAGE INTERTURN TEST  TO

CHECK

INTERTURN INSULATION

Connection Diagram

Interturn Tester

Test

CT

HIGH

VOLTAGE DRY POWER FREQUENCY WITHSTAND TEST ON PRIMARY

HIGH

VOLTAGE DRY POWER FREQUENCY WITHSTAND TEST ON SECONDARY

TYPE TESTS ON

CT¶S

 Short time current tests  Temperature rise test  Impulse test on primary winding  High voltage wet power frequency withstand tests  Determination of errors

SPECIAL TESTS  Measurement of Dielectric Dissipation factor(Tan)  Commissioning tests

ROUTINE TESTS ON VOLTAGE TRANSFORMERS  Accuracy Test  Induced Over voltage Withstand Test  Separate Source Withstand Test  High Voltage Power Frequency Withstand Test On Secondary Winding  Megger Test  Terminal marking and polarity test

ACCURACY TEST  Ratio Error(%)  Phase Angle Error(min) Measuring VT¶S Standard Accuracy classes are: 0.1,0.2,0.5,1.0 and 3 Protective VT¶S Standard Accuracy classes are: 3P and 6P