Influence of Oxygen-containing Filling Gas Mixtures on the Interruption Capability of MV Load Break Switches

Nowadays SF6 is commonly used as filling gas for medium voltage load break switches due to its outstanding insulating and arc-quenching properties. However, due to its high global warming potential the interrupting performance of alternative eco-friendly gases are investigated for such devices. This contribution investigates the thermal interruption capability of a medium voltage load break switch using two different oxygen-containing gas mixtures: dry air and a mixture of nitrogen, oxygen and carbon dioxide. The findings indicate an improved performance in comparison to pure nitrogen when considering an admixture of oxygen. In gas mixtures containing 80\% nitrogen, the addition of oxygen results in an enhanced thermal interruption capability compared to an equivalent proportion of carbon dioxide

Synthetic Testing of Load Current Interruption in Medium Voltage Load Break Switches

To conduct the mainly active load current test duty according to IEC 62271-103, a directly powered test circuit and therefore a medium voltage connection or a power generator is needed. A newly developed synthetic test circuit allows to replicate the current as well as the full transient recovery voltage (TRV) and the power frequent recovery voltage (RV) of the direct test circuit up to its crest value. It is dimensioned for voltage classes up to 52 kV and can be adapted to test currents between 630 A and 1250 A. The test circuit allows a detailed investigation of load break switches without costly high power sources and loads. Many parameters, like current and voltage steepness at current zero, as well as different parameters defining the TRV steepness can be varied individually