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Originally Posted by amino  Is it supposed to break itself when protecting other equipment? |
Yes. The MOV is a sacrificial part. Most surge arrestors include documentation that says you're supposed to replace them after they've been through an event like that. The nicer ones have lights on them to tell you if they've done their job and need to be replaced.
But I was under the impression that after they've been destroyed by shunting away a large transient, they're supposed to go open and not do anything at all, including not protect against future transients. I suspect that yours shorting out may be somewhat unusual.
I don't think any of us remote theorists can say whether the power switch on your step-down transformer had anything to do with it, but it's certainly something to keep an eye on in the future.