With the development of intelligent GIS equipment, a lot of electronic equipments are integrated on the GIS. The very fast transient electromagnetic disturbance (VFTED) resulted from the GIS switching operation has potential impact on the electronic equipment by the electromagnetic coupling between the VFTED and the circuit of "sensor-cable-intelligent electronic device(IED)". In this paper, a theoretical model based on the transmission-line network was established first to calculated the coupling of the ground potential rise produced by switching operations to the circuit of "sensor-cable-IED". Then the validation of this model was verified when it was used to a simple configuration. Finally, based on this model, the disturbance voltages on the sensor/IED ports and those between the IED ports were calculated and the suppression effectiveness of the grounding of the cable shield layer on the disturbance voltages was investigated. The results show that the grounding modes have great influence on disturbance voltage. By choosing the appropriate grounding mode, electromagnetic disturbance caused by switching operations can be effectively suppressed.