Electrical Testing of Power Transformers

 Electrical Testing of Power Transformers 

 Here is an outline based on the contents of the document Electrical Testing of Power Transformers:

 Introduction:

✅ History of power transformers

✅ Importance of transformers in high-voltage grids

✅ Purpose of electrical testing

 Voltage Stresses & Dielectric Integrity:

 Types of voltage stresses:

✅ Lightning over-voltages

✅ Switching over-voltages

✅ Temporary over-voltages

 Transformer insulation verification

 Test voltages

✅ Alternating voltages

✅ Impulse voltages

 Routine Tests:

 Measurement of Winding Resistance:

✅ Purpose and standards

✅ Measuring circuit and procedure

 Voltage Ratio & Vector Group Verification:

✅ Importance of voltage ratio

✅ Vector group classification and verification

 Short-Circuit Voltage & Load Loss Measurement:

✅ Purpose and procedure

✅ Measuring circuit and interpretation

 No-Load Loss & No-Load Current Measurement:

✅ Importance of no-load loss

✅ Measuring procedure

Separate Source AC Withstand Voltage Test:

✅ Purpose and standards

✅ Measuring circuit and procedure

Switching & Lightning Impulse Tests:

✅ Differences between switching and lightning impulses

✅ Measuring circuit and waveform analysis

Partial Discharge Measurement:

✅ Purpose and test methods

 Induced Voltage Test:

✅ Purpose and standards

 Insulation Resistance Measurement:

✅ Purpose and standards

 Test on Tap-Changers & Auxiliary Equipment:

✅ Functionality tests for tap-changers

 Check of Built-in Current Transformers:

✅ Standards and measuring procedure

 Type Tests:

 Temperature Rise Measurement

✅ Hot-spot measurement

 Measurement of Cooling Losses

 Sound Level Measurement

 Special Tests:

1.  Measurement of Zero-Sequence Impedance
2.  Harmonics Measurement of No-Load Current
3.  Frequency Response Analysis (FRA) Measurement
4.  FDS Measurement for Moisture Estimation
5.  Measurement of Insulation Capacitances & Loss Factor (tan δ)
6.  Measurement of Excitation Current with 400V
7.  Calibration of Winding Temperature Indicator (WTI)

Conclusion:

 The document outlines transformer testing procedures, including routine, type, and special tests to ensure reliability. Routine tests check winding resistance, voltage ratio, and insulation. Type tests assess temperature rise and sound levels, while special tests evaluate impedance, frequency response, and insulation. It highlights the importance of these tests for transformer integrity.