Electrical Testing

Transformer Services, Inc. provides and performs preventive maintenance of power transformers or components in accordance with manufacturer instructions to identify and correct potential problems before they affect operation or longevity.

The most effective preventive programs are oil sampling and testing, electrical testing and visual inspection. Together, these methods provide the information needed to establish the condition of the transformer and determine the necessary action in order to assure reliability and optimal performance of the equipment.

Electrical Testing

Accurate electrical tests measure several important values:

  • Insulating Resistance Value (DC Megger)
  • Power Factor (tests of winding & bushings)
  • SFRA
  • Transformer LTC Position Indicator
  • Transformer LTC Controller
  • Dewpoint test
  • SP-HIPOT – Applied Voltage test
  • Winding Resistance
  • Relationship of primary and secondary voltages (TTR)
  • Trip levels and accuracy of relays and low, medium, and high voltage circuit breakers

Test results are compared to manufacturer specifications and to guidelines set by the National Electrical Testing Association (NETA), National Emergency Management Association (NEMA), and Institute of Electrical and Electronics Engineers (IEEE). The results establish a baseline for comparison with future tests. Any repairs or calibration needed to bring equipment up to specification can be identified. Post-repair testing assures that proper corrective action has been taken.

In many cases, testing identifies the need for simple repairs and adjustments that may prevent costly repairs and downtime in the future.

Tests Performed
The range of tests includes:

  • Insulation Resistance
  • Transformer Turn Ratio
  • Winding Resistance
  • Power Factor

Current Transformer Test (CT)

  • Polarity
  • Tap Location
  • Saturation
  • Insulation resistance (Megger)

Equipment Used

TSI uses Doble and Omicron testing systems:

  • TTR Test Set
  • Power Factor Test Set
  • Insulation Resistance Test Set
  • Moisture/Dewpoint Test Set
  • Current and Voltage Power System Simulator
  • Current Transformer Excitation, Ratio, and Polarity Test Set
  • Sweep Frequency Response Analyzer
  • Current, Voltage & Resistance Multi-Meter
  • RTD (Resistive temperature Device) Temperature Calibrator

Test Report and Analysis
After the test program is completed, a report is compiled and results submitted to the customer. Results are compared to the equivalent factory tests values and to the performance standards set by NETA, IEEE and NEMA.