You may find that the main breaker trips repeatedly but there are no apparent electrical problems. Keep track of when this usually happens. It could be that running a large number of appliances at the same time is drawing current in excess of the main breaker's capacity and resulting in an overload of your electrical system. (Often the culprit can be a relatively small appliance that uses a great deal of current, such as a blow dryer or space heater.) There are 2 solutions to this problem: 1) reduce the load on your electrical system or 2) hire a licensed electrician to upgrade your home's electric panel.
Power Out Troubleshooting
If, on the other hand, you have no trouble resetting the branch breakers and the main breaker does not trip, the problem may be due to a faulty appliance or other piece of electrical equipment. Narrow down the possibilities by reconnecting all devices that were plugged in previously, 1 by 1, to see whether any of them causes a tripped breaker. If so, repair or replace the item.
Turn off or unplug as many appliances and electronic devices as possible throughout your home. Go back to the circuit breaker and flip all the breakers off. Turn the main breaker switch on and off several times, finishing in the "on" position. Then reset each of the breakers, one at a time. If this causes the main breaker to trip or if you are unable to reset one of the branch breakers, you'll know that you have a problem with that circuit, which will need professional electrical repair.
When the problem is limited to your home – or only 1 part of your home – grab a flashlight and take a look at any ground-fault circuit interrupter (GFCI) receptacles, your circuit breakers, main breaker, or fuse box to troubleshoot the electrical failure. On GFCI receptacles, which are usually found in bathrooms and kitchens, try pushing the reset button. If that isn’t the solution, you will need to see if a breaker has tripped or a fuse has blown.
Investigate to see whether the power failure is limited to just a part of your home. If you're working in the kitchen, for example, try clicking on a light switch in the living room. If the electricity is not functional anywhere in your house, look outside. See whether lights are visible at your neighbors' or phone them to ask if they have power. In an apartment building, look to see whether the hallway lights are on.
When the power outage affects more than just your home, check your utility outage map to see if there is a larger outage in your area and get updates on the estimated restoration time.
Turn off your light switches and unplug electrical devices to protect them from power surge damage when the service is restored.