When a 15-amp breaker switch seems to be sending too much power
Is there too much voltage/amperage going through this circuit? 


There is most likely too much voltage, as ArchonOSX commented. 


  How?


You miswired it and got 240V. You can check this using a voltage tester.


  Shouldnt the 15-amp breaker switch keep this from happening?


No, the job of the breaker is not to block too much voltage but to disconnect the circuit when too much current is flowing. This is mostly to protect the wiring in the wall from overheating and setting fire to your home. It won't protect a 100W incandescent bulb or anything similar. Those normally draw less than 1 Amp - far below the 15A breaker rating.

In the case of overvoltage, a higher current may briefly flow through your appliance/lamp but the appliance dies before the current reaches the breaker's limit.


  I am doing some wiring from a subpanel


Sorry to be a killjoy but I suggest you don't. At least until you have gained a higher level of understanding of household electricity. Since the higher voltage can fairly easily kill you, a family member or a visitor, you might want to pay an electrician to fix this for you properly and then consider taking some evening classes in the subject (if available in your part of the world).



Useful links


https://diy.stackexchange.com/tags/circuit-breaker/info
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