In order to accurately analyze the interference of arc discharge on a 110 kV Rogowski coil electronic transformer in the process of switching on and off capacitive small current of disconnector, a dynamic arc model is established using a TACS module of ATP-EMTP. Referring to the standard GB 1985—2014, a small current test circuit of disconnector opening and closing capacitance is established. Combining with the dynamic arc model, the maximum current amplitude of electromagnetic interference is 576 A, the maximum voltage amplitude is 1.8 p.u, and the transient current frequency is up to 210 kHz. At the same time, the ground capacitance and grounding resistance of the transformer are analyzed. The influence of factors on the parameters of the arc model of the disconnector is studied. The corresponding experimental circuit is set up. The small open-close capacitive current of the disconnector is measured. By comparing the voltage and current waveforms of arc discharge produced by actual measurement and simulation, the correctness of the established arc model is verified. This work is supported by National Natural Science Foundation of China (No. 51507091) and Research Fund for Excellent Dissertation of China Three Gorges University (No. 2019SSPY068).