The following video shows a 500 kV motor operated disconnect at Southern California Edison's Lugo substation near Hesperia, which is not designed to open under load. There is a switcher that is used to open the circuit, and then the disconnect opens up immediately after.
This switcher, however, had a history of one phase failing to open. When this happens, the disconnect opens with one phase still energised. Since this is not by design, there is no arc suppression and the result is really quite spectacular (see below).
Because of the history of failures at this site, a video camera was set-up to record the event each time the switcher was opened. There is actually about 25 amps flowing in this arc, which finally comes to an end when an upstream circuit breaker is opener.
Please note that you will need a relatively up-to-date version of Windows Media Player to watch this video. Any necessary software updates can be downloaded via the Microsoft Windows Update service.
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