## What is the Voltage Ratio Error and Phase Difference of the Voltage Transformer? What are the Factors that Affect the Error?

**What is the Voltage Ratio Error and Phase Difference of the Voltage Transformer? What are the Factors that Affect the Error?**

The voltage ratio error of the voltage transformer is the difference (expressed as a percentage) between the converted voltage value of the measured secondary side voltage and the actual value of the original primary voltage. It is mainly caused by the influence of leakage impedance. Voltage ratio error of voltage transformer.

The phase of the voltage transformer refers to the phase difference between the secondary voltage vector (-U2) and the primary voltage vector (U1) after the reverse phase, also known as the phase Angle error, which is mainly caused by iron loss. When the reversed secondary voltage is ahead of the primary voltage, the phase difference is positive. On the contrary, when the secondary voltage lags behind the primary voltage, the phase difference is negative.

The voltage ratio error and phase difference of the voltage transformer are not only related to the impedance and no-load current of the primary and secondary windings, but also related to the size of the secondary load and power factor. Generally, the main reasons for voltage transformer error are as follows:

The significant voltage fluctuation of the primary side of the voltage transformer causes the change of the magnetization current and causes the error.

The increase of the no-load current of the voltage transformer will increase the error. The variation of power supply frequency causes the variation of error to increase or decrease.

The secondary load of the voltage transformer is too heavy or the power factor is too low, that is, the impedance of the secondary circuit (the impedance of the instrument and the wire) exceeds the provisions, etc., which will increase the error.

When the secondary side is close to no-load operation, the error of the voltage transformer is minimal. Therefore, in order to make the measurement as accurate as possible, the secondary load of the voltage transformer should be minimized, that is, too many instruments and protection should not be connected, so as to avoid the large leakage voltage drop caused by excessive current, which will affect the accuracy of the transformer.