The primary side of voltage transformer is grounded by star connection, and the secondary side is grounded by star connection. What are the functions?

For a symmetrical three-phase system, the line voltage is equal to three times the root sign of the phase voltage. If it is a rough measurement, any phase voltage or line voltage can be measured.

For three-phase monitoring or occasions requiring accurate measurement:

1. If only line voltage is measured, three-phase voltage can be measured by V-connection of two voltage transformers and three voltmeters.

At present, some measuring devices with vector operation function, such as DT digital transmitter developed by Hunan Yinhe Electric Co., Ltd., each transmitter has two measuring channels, and one digital transmitter can measure the three-phase voltage of transformer VV connection.

2. If it is necessary to measure the phase voltage and line voltage, the Y-shaped connection of three transformers should be adopted to measure the three-phase voltage. After measuring the three-phase voltage, the three-phase line voltage can be accurately calculated by vector operation. On the other hand, the phase voltage cannot be inferred by measuring the outlet voltage.