In recent years

the incidents of axial vibration sensors of synchronous compensators in converter stations being misactivated by VFT interference frequently occur

which has seriously impaired the reliability of the DC transmission system. The study of the propagation characteristics of VFT interference is of great significance in analyzing the mechanism of interference coupling to the secondary system as well as in formulating the anti-interference measures for the axial vibration sensors. In this paper

the TGPRs of the main grounding grid

the secondary equipotential grid and signals of the axial vibration sensor are tested during the operation of the GIS switch in the converter station. The statistics and analysis of time and frequency domain characteristics of the test results are carried out

and the propagation characteristics of the VFT interference from the main grounding grid to the axial vibration sensor are finally obtained. The results show that the propagation links of the interference are sequentially the AC filter GIS busbar

the main grouding grid

the secondary equipotential grid

and the axial vibration sensor. When the interference propagates from the cable trench to the electronic device room

the spectral range increases from 15 MHz to 20 MHz

and the main frequency value increases; when it continues to propagate to the synchronous compensator body

the spectral range increases to 30 MHz

but the main frequency value decreases. The interference propagating from the main grouding grid to the secondary equipotential grid has a long duration

and the interference continuing to the axial vibration sensor has a larger high frequency component.