Design Rules for Environmentally Friendly Medium Voltage Load Break Switches

IEEE Transactions on Power Delivery, vol. 36, pp. 2668–2675

Abstract

Today's medium voltage distribution grids are often designed in a ring-structure with ring main units at their nodes. As these grids are mainly placed in urban areas, the space is limited and compact and reliable SF6filled switchgear is commonly used. However, SF6is the most potent greenhouse gas known and industry as well as decision makers are looking for possible replacements. In the course of substituting SF6in ring main units, the load break switch is the critical component. In the switch, the gas has to serve as both, insulating and quenching medium. This work investigates the influence of the design of a polymeric nozzle on the thermal interruption capability and dielectric recovery of a medium voltage load break switch. The experiments are performed in a nitrogen/carbon dioxide atmosphere with nozzles made from polytetrafluorethylene. The main influencing factor on the interruption capability is the applied blowing pressure. Additionally, the nozzle throat length as well as the throat diameter show significant impacts on the interruption capability. From the experimental findings, empirical design rules are derived to estimate the thermal interruption capability of arbitrary nozzle designs for a fixed contact diameter.

Authors 1

1. Martin Schaak

   Siemens (Germany)

   Affiliation as printed

   Siemens AG, Smart Infrastructure, Frankfurt am Main, Germany