Short circuit fault of power system refers to that one or more current carrying conductors are grounded or do not contact each other through load. Due to the frequent occurrence of this fault, it is extremely unfavorable to the safe operation of power system.
In three-phase system, short circuit fault can be divided into three-phase short circuit, two-phase short circuit, single-phase short circuit, single-phase grounding short circuit, two-phase grounding short circuit, etc. When the circuit is short circuited, the conductor temperature can rise rapidly, even make the conductor red and melt, resulting in equipment damage. Short circuit fault of high voltage power grid can cause power grid collapse. Arc and spark generated by short circuit can cause fire, explosion, electric injury and other malignant accidents.
The main measures to prevent short circuit fault are to limit short circuit current, shorten the duration of short circuit current and reduce the chance of short circuit. First of all, the short-circuit current shall be calculated, and the electrical equipment shall be correctly selected and calibrated to ensure that the rated voltage of the electrical equipment is consistent with the rated voltage of the line. At the same time, the rated current of the relay protection device should be correctly selected, and the quick break protection device should be used to ensure that the short circuit current can be quickly cut off in case of short circuit, reduce the duration of short circuit current, and reduce the loss caused by short circuit. Installing lightning rods in substations and lightning arresters near transformers and lines can effectively reduce lightning damage. Reactors shall be used to increase system impedance and limit short circuit current.
Once a short circuit fault occurs, the fault line or equipment shall be removed from the power system so that the rest can continue to operate. It is prohibited to pull the knife switch with load and close the grounding knife switch with electricity. The grounding wire shall be removed immediately after the line construction. Routes and equipment shall be inspected frequently, defects shall be found in time, and maintenance shall be carried out quickly. In order to ensure the construction quality of overhead lines, line maintenance shall be strengthened.
During live installation and maintenance of electrical equipment, miswiring and misoperation shall be prevented, and measures to prevent short circuit shall be taken when working close to live parts. At ordinary times, the management shall be strengthened to prevent small animals from entering the power distribution room and climbing on the electrical equipment, and the conductive dust shall be removed in time to prevent the conductive dust from entering the electrical equipment.
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