The utility model provides a voltage sensor who is fit for transformer substation's in -site measurement, includes equalizer ring, primary voltage sensing unit, acquisition and transmission unit, lift platform. The primary voltage sensing unit adopts parallel plate capacitor to constitute high -pressure electric capacity and low pressure electric capacity fills the air in, has formed a gas capacitor, high pressure electric capacity comprises the gas capacitor that 3 three pole pitchs are 1.5m, low pressure electric capacity comprises the gas capacitor that 1 pole pitch is 0.04m, high pressure electric capacity and low pressure electric capacity are through the series connection partial pressure. Low pressure electric capacity below is arranged in to the acquisition and transmission unit, and both link to each other through optic fibre. The acquisition and transmission unit is connected gradually and is formed by signal processing module, AD conversion module, FPGA triplex. The subsequent processing terminal can be given through optical fiber transmission to the signal of acquisition and transmission unit output. The utility model discloses can realize having shortened the check -up cycle to electronic voltage transformer's electrified check -up, the operating is simplified step has been avoided because of the loss that the power failure caused, has improved electronic voltage transformer on -line calibration's the degree of accuracy and reliability.