Immunity requirements for secondary equipment with regard to switching operations of disconnectors in substations

Switching operations of disconnectors in substations will give rise to a voltage and current damped oscillating wave on the busbars and produce electric and magnetic field simultaneously, which will coupled to the port of the monitoring and protection equipment at switchyard, affecting the performance of secondary equipment. This paper developed a measurement system, by which the characteristics of disturbance were obtained through field measurement in AIS and GIS substations with system voltage levels from 110kV to 1000kV. Based on the disturbance characteristics, the test levels of electrical fast transient (EFT), surge (impulse), damped oscillatory wave and damped oscillatory magnetic field immunity test are recommended.