Practical measurements on power and current transformers
“This course contains the use of artificial intelligence. »
What you’ll learn
- Common electrical measurements on power and current transformers.
- Transformation ratio measurements.
- winding resistance measurement.
- Insulation measurement.
- Hourly index measurement.
Course Content
- Introduction + Power transformer measurements –> 5 lectures • 28min.
- Current transformer measurements –> 2 lectures • 16min.
Requirements
“This course contains the use of artificial intelligence. »
A series of tests and measurements is essential for the following applications for power transformers and current transformers (CTs):
- Initial energization
- Reenergization after repair
- Diagnostics after an internal fault
- Scheduled or on-demand measurements and tests
Main measurements:
1 – For power transformers
- Insulation resistance measurement (transformer insulation test)
- Tank insulation measurement
- Winding resistance measurement
- Transformation ratio measurement
- Determination of the vector group (clock number)
2 – For current transformers (CTs)
- Insulation resistance measurement
- Secondary winding resistance measurement
- CT ratio measurement
- Saturation or magnetization measurement
- Polarity determination (direction of transformation)
Currently, these measurements are performed using digital test equipment Modern instruments (digital primary injection system, digital megohmmeter, digital microohmmeter, etc.) are used. These devices are designed to apply classic or universal measurement methods, enhanced by modern technologies.
In this course, I will highlight some of these classic methods, which were used (and sometimes still are) before the advent of digital test equipment.
The resistance range of transformer windings extends from a few microohms to a few ohms. High-power transformers have lower winding resistances. Therefore, any measurement other than digital is very difficult. The classic voltmeter method is rarely used for low resistances, or is used with caution, especially for contact resistances during handling.