Voltage Transformer (VT) is a specialized device for measuring voltage in high voltage power systems. It is mainly used to reduce the high voltage to a low voltage within the safe and measurable range, and is provided for the use of measuring instruments, protective devices and control equipment.
The main function of voltage transformer is to reduce the voltage. In power systems, high voltages are not conducive to direct measurement and use. Equipment and instruments operating at high voltages are not only expensive, but there is also a risk of electric shock and damage. By using voltage transformers, high voltages can be reduced to a safe range for measurement, monitoring and control.
The principle of operation of voltage transformers is based on electromagnetic induction. When the main circuit passes through the wires in the winding, the change in voltage causes a change in the magnetic field in the winding, which generates a corresponding induced electromotive force in the secondary winding. The induced electromotive force is proportional to the main circuit voltage, so the voltage on the main line can be determined by measuring the voltage on the secondary winding.
Voltage transformers serve several important functions in power systems. First, they are used to measure and monitor the voltage of the power grid. Voltage measurement is one of the core indicators of power system operation, and it can be used to assess the stability of the grid, troubleshoot faults, and adjust power loads. Secondly, voltage transformers are also used for protection devices, such as differential and overcurrent protection, which detect faults and abnormalities in circuits and take timely protective measures to prevent equipment damage and grid paralysis. Finally, voltage transformers are also used in control devices, such as regulating transformers and automated switches, to ensure stable operation of the power grid and power quality.
However, voltage transformers cannot be used to measure DC voltage directly. This is because the transformer works based on the principle of electromagnetic induction, and DC current does not have a changing magnetic field and therefore cannot generate an induced electromotive force. Also, since DC voltage does not change over time, it is not possible to derive an accurate voltage value from an active measurement. Therefore, other types of sensors or measuring devices are required when measuring DC voltage.
To summarize, a voltage transformer is an indispensable device in a power system that reduces high voltage to a safe and measurable range and makes it available for use by measurement, protection and control equipment. However, voltage transformers cannot be used to measure DC voltages because their principle of operation is based on electromagnetic induction and DC currents do not have a magnetic field to generate an induced electromotive force. Therefore, when measuring DC voltages, other suitable measuring devices are required.
