When lightning causes a substation to be shut off and the system switches to another line, a momentary power outage occurs. In this case, the system temporarily becomes open, so it is [OPEN].

(However, while it becomes open on the high-voltage lines from the substation, when considering household outlets, the nearest pole transformer or factory transformer equipment is DC short-circuited, so it cannot be said to be completely open.)

Momentary voltage drops occur due to voltage drops at substations or power-on of large nearby loads, so the open state does not occur, making it [SHORT].

Also, if another device connected to the same power system short-circuits due to some accident, it will also be [SHORT] mode.

Note that IEC 61000-4-11 does not explicitly state this point.