How to ensure EMC of voltage sampling for power FTU?

Voltage sampling EMC assurance requires consideration of high-voltage isolation and noise suppression. A resistor divider plus isolation amplifier scheme is adopted. The voltage divider resistors are high-voltage thin-film resistors with an accuracy of 0.1% and a power margin of 2 times. The isolation amplifier is an ISO7240C with an isolation voltage of 3kVrms. An RC filter (10kΩ + 1nF) with a time constant of 10μs is added to the sampling input. PCB design: 15mm slots are used between the high-voltage and low-voltage sections, and the creepage distance is greater than 8mm. Coaxial cables are used for the sampling lines, with the outer shield grounded. With this design, the voltage sampling accuracy is 0.2%, the common-mode rejection ratio is greater than 120dB, and it meets the surge test requirements of IEC 61869 and IEC 61000-4-5 standards.