"As per the rule we should use "present tense" after time clause, including "when". But since it's a hypothetical sentence I should use "past" tense here, shouldn't I? Is my sentence correct?"
It's not a matter of rules. It never is.
The problem is fictitious in this case for "when" is redundant here, unnecessarily put in, just to complicate things. You are already stating the time, which is the cut-off time. Never mind if you are speaking hypothetically. You say "I (would) smile to her every time we (met) meet", not "I smile to her every time WHEN we meet". Likewise, you say "… every time the electricity supply (was/is) cut off", not "every time WHEN the electricity supply (was/is) cut off". So, your sentence is neither correct nor incorrect, only unreal.
A different question would be, "When I (met) meet her, I (would) smile to her every time" (or, rather more awkwardly, "I (would) smile to her every time, when I (met) meet her"), meaning you can't refrain from it, that for whatever whatever the reason you never fail to do it. That's not the case in your example.
As I said, it's never a matter of rules. It's a matter of the function the rules serve. You need to grasp it to know how to use—or not to use—the rule, or to see why it's not relevant.