Dell computer has no power

If you had a power surge of some kind that tripped the breaker and your system was not protected by a surge protector, it's possible that the power supply (in the computer) was damaged and will need to be replaced. These are readily available, relatively inexpensive, and can easily be checked by a reliable local tech with a load tester to see if that's the problem.
Please also see this article for general startup troubleshooting, including links regarding the power supply. The only other thing I can think to point towards is possibly the power switch itself, which can be bypassed by jumping a connection on the motherboard, but I'd start by checking the power supply and go from there. Replacements are usually about $30.00.

I hope this information allows you to resolve this issue. If you need further assistance, please post back with a comment to this thread.
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The PC power supplies are always connected to power, the so-called off state is in reality stand-by. I'm afraid that the cause of the breaker tripping (some power surge or something) has killed your PC's power supply unit.