Electrical System Protection is a very important field of study. Most of the design engineers find it difficult to protect their equipments from voltage surges, power breakers, fluctuations etc. There are several standard projections used for electrical power systems. The basic protection systems are Overload Protection, Under voltage Protection, Overvoltage Protection, Phase Failure Protection, Phase Sequence Reversal Protection. The first one that is Overload or over current protection is sufficient for majority or equipments. A simple schematic is given in the figure. This is a basic circuit that trigger an opening solenoid and protect the system from overloads. Now you take any circuit around you and make a schematic of the same. Your schematic will look very same as this figure!