Experimental Analysis and Suppression for Very Fast Transient Disturbance in Device Power Port During Switching Operation in GIS Substations

Abstract

Transient electromagnetic disturbance induced by disconnector and circuit breaker operations in gas insulated switchgear (GIS) has a serious impact on electronic equipment in substation secondary system. Typical forms of transient electromagnetic disturbance are space electromagnetic radiation and transient enclosure voltage (TEV) in GIS. Transient electromagnetic disturbance can be easily coupled to the internal of electronic devices in many ways and one of the coupling paths is power ports of electronic devices. This paper highlights the coupling mechanism and characteristics of electromagnetic disturbance to electronic equipment through its power port. Discharge in a SF6 gap is used to simulate the complex electromagnetic process generated by switching operations in GIS, and then the coupled electromagnetic disturbance in power supply ports of common field operation devices is measured in order to obtain the coupling mechanism and characteristics of electromagnetic disturbance during switching operations. Discharge experiment results show that the main frequency components of electromagnetic disturbance in power supply ports are 1.2 MHz and 8.2 MHz, and meanwhile there are also 20–60 MHz and 120–140 MHz frequency components. The relationship between power port coupled disturbance and TEV on shielding box in test system is nearly linear. Furthermore, a deeply suppression isolation transformer is designed to decrease electromagnetic disturbance based on frequency characteristics of electromagnetic disturbance, and the structure and installation method of the transformer are given. Shielding performance tests are carried out to the transformer through frequency sweep and discharge experiment. Results show the shielding effectiveness of the transformer is up to −60 dB at the frequency components lower than 20 MHz and −40 dB below 68 MHz, which demonstrates that the suppression structure can protect the power port of secondary equipment in substation.