Field evaluation of industry´s first self-protected, light-triggered thyristor

A description is given of the industry´s first self-protected, light-triggered thyristor to be developed, fabricated, and field-demonstrated. This device is installed on a 13.8 kV, 40 MVAr AC switch using 16 series-connected devices operating in one phase of a static VAr compensator at the Minnesota Power Co.´s Shannon substation. The light-triggered thyristor was designed with internal overvoltage protection (safe turn-on at a preset overvoltage level) and with significantly improved dv/dt withstand characteristics. In the process, the AC switch in the static VAr compensator was redesigned to incorporate 16 instead of the originally installed 24 series-connected thyristors