Experiment Study on the Influence of Gas Humidity and Purity on the Property of 40.5 kV N2 Insulated Switchgear

Sulfur hexafluoride (SF6) has excellent insulating and arc quenching properties, but it has strong greenhouse effect which is 23900 times of CO2. Nitrogen (N2) is an environmental-friendly gas with good insulation performance and is developed to use in gas insulated equipment in recent years. In this paper, the effect of humidity and purity on N2 insulated switchgear was researched. A 40.5 kV N2 insulated switchgear was taken as the test object. Short-duration power-frequency withstand voltage test and lightning impulse voltage test were carried out under different gas purity and humidity. The test results showed that N2 mixed with 20% O2 can pass both tests. N2 containing 650 ppm, 1200 ppm and 2380 ppm water can pass both tests. While the water content increased to 12700 ppm, the switchgear cannot pass the test. From the aspects of ionization energy and electronegativity, the test results were analyzed. The results can provide guidance and basis for the maintenance and operation of N2 insulated switchgears.