Analysis on electromagnetic compatibility immunity requirements for secondary equipment during switching transient operations in intelligent substation

Secondary equipment of intelligent substations, such as combined unit and intelligent terminals, is susceptible to the electromagnetic disturbance generated by switching transients in switchyard. To maintain the reliable operation of the secondary system, we need a realistic assessment of electromagnetic compatibility requirements. Thus we developed a measurement system for transient electromagnetic disturbance and obtained the disturbance characteristics in the ports of secondary equipment through the test in multiple intelligent substations with different voltage levels. Test results show that the waveforms of common-mode, differential-mode disturbances and magnetic field are all damped oscillation and the maximum amplitude of common-mode disturbances caused by the disconnector switching operations is close to 2 kV with main frequency more than 20 MHz. Damped oscillatory wave immunity test is recommended to take at least the third test level in IEC 61000-4-18. Damped oscillatory magnetic field test is recommended to take at least the fifth test level in IEC 61000-4-10 and damped oscillatory magnetic field test with oscillation frequencies of 3 MHz, 10 MHz and 30 MHz should be added.