Triggered current limiters for closing bus ties, bypassing reactors and improving power quality

Abstract

Current limiting fuses have been commonly applied in protective systems for decades. They are effective for controlling peak currents and for limiting fault energy. Triggered current limiters (TCLs) are higher continuous current, electronically controlled variants of the more conventional technology. They are applied in the traditional current limiting fuse roles, but in addition, adapt readily to unique applications such as bypassing (shunting) current limiting reactors and closing system ties between adjacent buses. Bypassing reactors with TCLs can eliminate the continual losses and regulating voltage drop associated with current limiting reactors. This application provides full protection during a fault and load continuity following a fault. By closing system ties through a TCL the user may improve switching flexibility, better balance transformer loads, and/or start large motors with less system voltage sag. This paper investigates the practicality, the benefits and the limitations of TCLs in these specialized applications. It also introduces the concept of using TCLs for power quality enhancements on critical circuits where a bus fault may cripple an adjacent unfaulted bus.