Summary

Current transformers (CTs) are a link between transmission and distribution systems, and instruments that monitor the currents and other electrical values in the system. They are also the link between T&D systems and equipment, and devices that protect those systems and equipment. And they are the link between T&D systems and revenue metering instruments.

This 34-minute DVD describes the application, construction, accuracy class ratings, and operation of current transformers in typical installations at substations. Two methods of checking current transformer polarity are also covered.

Training Sessions

• CT Application and Construction – 7 minutes States the functions of a current transformer. Describes common current transformer applications in a substation. Describes the construction of common substation current transformers.
  
  
• CT Accuracy Class and Operation – 11 minutes Explains the meanings of CT accuracy class ratings. Describes the basic operation of a current transformer. Explains saturation in a CT core. Describes a CT's turns ratio and current ratio as they relate to the CT's current and voltage output.
  
  
• Polarity Testing: DC Kick Method – 9 minutes Explains why the polarity of a current transformer is checked. Describes the DC kick method of checking the polarity of a current transformer.
  
  
• Polarity Testing: Current Method – 7 minutes Describes the current method of checking the polarity of a current transformer.

Support Materials Available

Student workbook, instructor guide.