5T- Voltage Transformers

Voltage Transformers

There are two types of voltage transformers, magnetic voltage transformers (VT) and capacitive voltage transformers (CVT). The magnetic voltage transformers are most economical for voltages up to about 145 kV and the capacitive voltage transformers for voltages higher than 145 kV. A CVT can also be used together with the Power Line Carrier (PLC) devices that are used for communication over the high voltage transmission circuits. Voltage transformers are together with current transformers known as instrument transformers. Voltage transformers are in most situations connected between phase and ground.

The standard that describes voltage transformers in details is IEC 186. The main functions of voltage transformers are:

• To transform voltages from high value to a value that can be easily handled by protection relays and instruments
• To insulate the metering circuit from the primary high voltage.
• To give standardization possibilities for instruments and protection relays to a few rated voltages

This course is suitable for engineers and technicians with a desire to understand the fundamental theory and operating principles of voltage transformers. Presented details cover basic engineering laws, measuring error, voltage factor, burden and accuracy class, non-linear burdens, different voltage transformer winding connections, Ferro resonance and specific applications for protection schemes. Upon successful completion engineers will be able to address different terms related to voltage transformers, understand their operational principles and various applications.