How to apply common mode and differential mode separately in edge box surge testing?

According to IEC61000-4-5 surge testing, differential mode surges are applied to the power supply ports of the edge box, with a source impedance of 2Ω between L and N (1.2/50μs). Common mode surges are applied between L-PE and N-PE, with a source impedance of 12Ω. The signal port is used for common mode testing only, with a line-to-ground source impedance of 42Ω. For actual wiring, during differential mode testing, the isolation transformer and disconnect switch are set to the LN position. For common mode testing, LN is shorted before applying surges to PE. The output of the surge generator is correctly connected, and the polarity coupling decoupling network (CDN) ensures that the EUT power supply is not affected. The edge box uses 1kV for differential mode and 2kV for common mode. A TVS 5.0SMDJ33CA is selected, with a VRWM of 28.2V and a clamping voltage of 53.3V, which can effectively protect against surges.