Choose and short circuit current calculation circuit breakers have two kinds of circuit breakers and fuses used to protect electrical low voltage power distribution systems. Currently we use the most is the circuit breaker, use it for distribution line short-circuit protection and overload protection. However, there are many problems in the selection of the low-pressure circuit breaker, which highlights the problem is not short-circuit current calculation. Short-circuit protection of electrical distribution lines breaking capacity should be greater than the expected short-circuit current at the installation. Select the circuit breaker should first calculate the outlet end of the short-circuit current of Nanyang electric power engineering and maintenance, but some designers did not short-circuit current calculation, selected short circuit limit short-circuit breaking capacity is not enough, you can not cut off the short circuit fault current. To determine the short-circuit current at the breaker installation, according to design manual calculations, but more complicated; you can also use a "short circuit current search curve" to determine calculate the current, relatively simple. Now designed by Shanghai Electrical Apparatus Research Institute, an Ruian Wansong Electronic Appliance Co. breakers information provided "short-circuit current search curve" appended. This curve by checking Nanyang electrical engineering, can more easily obtain short-circuit current approximation any installation position. The examples given a short-only hypothesis, the actual engineering design of the most commonly used short point is selected in the protection of electrical outlet end. Installation for surface grounding wire should meet the following requirements :( a) to facilitate inspection; (ii) laying position should not hamper removal and repair of equipment; the distance (c) between the support member in a horizontal straight portion is generally 1-1.5 m, the vertical portion is 1.5-2 meters, turn portions is 0.5 m. (Iv) ground wire should be laid horizontally or vertically, but also the structure of the building tilted parallel to the straight line segment should not have ups and downs and bends and so on. (E) building expansion joints across the ground, when settlement joint, should be added compensation, compensation is available grounding wire bent into an arc instead of itself. Nanyang electric power engineering, installation, Nanyang power engineering, electric power is provided by Nanyang Fulong Fulong Power Engineering Company Limited. Nanyang Fu Long Electric Power Engineering Co., Ltd. (www.nyfulong.com) strong, credible, Nanyang in Henan transmission equipment and materials industry has accumulated a large number of loyal customers. The company better work attitude and constantly improving innovative ideas will lead Teflon electricity into the brilliant and you work for a better future!