Summary

Current transformer (CTs) are generally reliable, accurate, and relatively inexpensive. However, they are used to monitor and protect critical systems and equipment and they are often located in and on high-cost equipment. Therefore, it is good practice to ensure that a current transformer is in good condition and able to perform as it is designed to, before it is put in service.

This 34-minute DVD describes how to demagnetize a CT, how to test a CT's ratio, and how to test a CT's insulation resistance.

Training Sessions

• Demagnetizing a Current Transformer – 7 minutes Explains why it may be necessary to demagnetize a current transformer. Describes the basic steps for demagnetizing a current transformer.
  
  
• Ratio Testing: Current Method – 8 minutes States the purpose of current transformer ratio testing. Describes the current method of checking the ratio of a current transformer.
  
  
• Ratio Testing: Voltage Method – 10 minutes Describes the voltage method of checking the full winding ratio of a CT. Describes the voltage method of checking the tapped winding ratios of a CT.
  
  
• Insulation Resistance Testing – 8 minutes Explains the purpose of testing current transformer insulation resistance. Describes the basic steps for testing the insulation resistance of a current transformer. Describes how to correct insulation resistance readings for temperature.

Support Materials Available

Student workbook, instructor guide.