The most obvious reason for a surge protector is to protect electronics from lightning strikes, which can deliver many millions of volts of electricity through your electrical lines. Lightning does not need to strike your house to cause a power surge; strikes many miles away can cause electrical problems. A surge protector may not offer complete protection from a lightning strike, so unplug electronic devices during lightning storms to avoid possible problems.
Line noise is the electronic interference that occurs when appliances or other electrical devices are connected to the same circuit. Your surge protector may be clicking due to mini surges, known as spikes, from the operation of other electronics. Running a blender or vacuum cleaner may cause a temporary surge in the electricity to the outlet your surge protector is plugged in to, causing it to click to divert the excess power. Take note if any other appliances are in operation when the clicking occurs, and move the surge protector to a different circuit to see if it stops.
The circuit breaker inside your home's electrical box acts as a built-in surge protector that shuts off the circuit it's connected to if it detects the presence of too much electricity. Loose wiring and damaged or defective fuses can prevent a breaker from tripping properly, which may allow higher amounts of electricity through to your outlets. This can cause your surge protector to click. You can test the flow of electricity in your breakers with a multimeter, or consult an electrician for a thorough inspection and evaluation.
If the breaker seems operational, you may have a faulty section of wiring along the circuit connected to your outlet. Frayed wires or loose connections can cause unstable amounts of electricity, which can trigger your surge protector into action. Unfortunately, finding faulty wiring can be a tall task for even the most die-hard do-it-yourselfer, so you may need to speak to an electrician for help.