Here are two DC power supply protection circuits. The 3-pin regulator 7800 series gets popular. I also like it. Because it is convenient and affordable.
This is overload protection for transformers and load, is simple circuit cut off-on by relay. And so fast switch witch SCR driver. can set sensitive by VR1
This is Blown Fuse indicator circuit by LED Display. A Fuse be the equipment protects that use often most. Because of cheapness can use protect electronics
It can be used to replace conventional fuses. Because it's comfortable not need to replace the fuse every time the power too over. This circuit use transistors so simple and low cost.