A short-circuit fault in a power system is one or more phases of current-carrying conductors grounded or not in contact with each other through the load, which is extremely detrimental to the operation of the power system due to the multiple occurrence of this fault.

　　In three-phase systems, short-circuit faults can be divided into three-phase short circuits, two-phase short circuits, single-phase short circuits, single-phase grounded short circuits, two-phase grounded short circuits and many others. When a short circuit occurs in a circuit, it can cause the conductor temperature to rise rapidly and even make the conductor red and melt, resulting in equipment damage. Short circuit faults in high voltage grids can cause the grid to disintegrate. The arcs and sparks generated by a short circuit can lead to fires, explosions, electrical injuries and other malicious accidents.

　　The main measures to prevent short-circuit faults are to limit the short-circuit current, shorten the duration of the short-circuit current and reduce the chances of a short-circuit occurring. First of all, the short-circuit current should be calculated, the correct choice and calibration of electrical equipment, so that the rated voltage of electrical equipment and the rated voltage of the line match. At the same time, the rated current of the relay protection device should be correctly selected, and a quick-break protection device should be used to ensure that the short-circuit current can be quickly cut off when a short-circuit occurs, to reduce the duration of the short-circuit current and to reduce the losses caused by the short-circuit. Lightning rods should be installed in substations and lightning arresters should be installed near transformers and on lines to effectively reduce lightning damage. Reactors are to be used to increase the system impedance and limit the short-circuit current.

　　In the event of a short-circuit fault, remove the faulty line or equipment from the power system so that the rest can continue to operate. It is forbidden to pull the switch with load or to close the earthing switch with electricity. Line construction should be completed immediately after the removal of the grounding wire. Lines and equipment should be inspected frequently, defects found in time and quickly overhauled. To ensure the quality of overhead line construction, line maintenance should be strengthened. In power operation, relevant relay protection testing equipment is also important, microcomputer relay protection tester, handheld optical digital tester, handheld optical digital analyser, heterodyne dielectric loss tester, etc. should also be regularly overhauled to ensure the normal, fast and efficient operation of the power grid.

　　When installing and overhauling electrical equipment with electricity, it is important to prevent miswiring and misoperation, and to take measures to prevent short-circuiting when working in close proximity to live parts. In normal times, strengthen management to prevent small animals from entering the distribution room and climbing onto electrical equipment, and remove conductive dust in time to prevent conductive dust from entering electrical equipment.