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Current Transformer Excitation, Ratio and Polarity Test Set


  • CTER-91
  • Overview  
  • Application  
  • Downloads  
  • Tests CTs mounted in transformers or switchgear
  • Tests without changing leads
  • With Model CTER-91 current transformers can be tested while mounted in transformers, oil circuit breakers breakers or switchgear - without moving bushings and CTs. Using the voltage-comparison method, Model CTER-91 provides a variable-voltage output up to 1000 volts and precision instrumentation for testing single and multi-ratio CTs.
  • Application

    Saturation Test

    The CTER-91 provides a variable voltage output and digital instrumentation for measuring the excitation voltage and excitation current that results as the voltage applied to the CT under test is increased. As the CT under test begins to saturate, a large increase in current will be detected for a small increase in voltage.

    Ratio Test

    The ratio test is performed by comparing a voltage applied to the secondary winding to the resulting voltage produced on the primary winding. For example, if 1 volt per turn is applied to the secondary winding, the voltage present on the primary winding would be 1 volt. More specifically, if 120 volts were applied to the secondary of a 600/5 current transformer (120:1 ratio), 1 volt would be present on the primary winding.

    Polarity Test

    Polarity of the current transformer under test is determined by special circuitry that divides the voltage applied to the secondary winding by either 10 or 100, depending on switch position, then adds the result to the primary voltage. An increase in magnitude indicates correct polarity, and a decrease shows incorrect polarity.