文献翻译封面

南昌工程学院

11级毕业（设计）论文文献翻译机械与电气工程系（院）电气工程及其自动化专业

题目Small current grounding system

学生姓名赵宜

班级电气工程及其自动化1班

学号 2011100491 指导教师许惠君

日期2015 年 1 月7 日

南昌工程学院教务处订制

评语：

指导教师：

年月日

Small current grounding system

Small current grounding system -- the small current grounding system: neutral point ungrounded or through the arc suppression coil and high impedance grounded three-phase system, also known as the neutral point indirectly grounded system. When one phase ground fault occurs, because it can not form a short circuit loop, the grounding fault current is often much smaller than theload current, so the system is known as "the small current grounding system".

1The division standard

In the division of standards in China: X0/X1>4 - 5 system belongs to the small current neutral grounding system (system American and Western EuropeX0/X1>3 belongs to the small current neutral grounding system)

Of which: X0 as the system zero sequence reactance, X1 as the system positive sequence reactance.

2 small current neutral voltage unbalance of system analysis

In actual operation, often to monitor bus voltage unbalance phenomenon caused by many reasons, the bus voltage imbalance, the methods of handling failures due to vary.

(1) a phase two fuse in the busbar voltage mutual inductor. The phenomenon ofcentral signal alarm, voltage transformer, a phase voltage is zero, the other two phase voltage is normal. Such as three-phase voltage 10kV for 0kV, 6.1kV,6.1kV. Treatment strategies such as low voltage protection: exit associated with the transformer, the replacement of two fuse. (2) a phase of a fuse in the busbar voltage mutual inductor. The voltage from thetable reflects a phase voltage is greatly reduced, the other two phase voltage isdecreased in different degree. I board the Qinghai Lake bus. I board the Qinghai Lake bus voltage is 6.7kV, 5.2kV, 2.5kV, voltage transformer C exit inspection found a fuse, after replacement, put into operation, the voltage normal.

(3) outgoing circuit grounding grid, which is common in normal operation condition. Grounding, fault phase voltage is reduced, the grounding metalcompletely reduced to 0kV, the non fault phase voltage increases, metal fullygrounding for line voltage rise. Some Substation & "selection for small current grounding detection device &", according to produce zero sequence current grounding, can judge the grounding line. If the substation without this device,through the operations of staff elected grounding line, to deal with through the timely dispatch notification line maintenance personnel. Because the arc grounding often cause an explosion, bus arrester voltage transformer oiltemperature heating, easy to damage the equipment, causing line another point grounding, resulting in two phase short circuit, especially the ground can causeintermittent network voltage should not be increased.

Firstly, according to the operation experience and choice principle, first pull no power, maximum branches, the longest line, load the lightest and no importantuser line, after the pull less branches, the shortest line, heavy load and important user line.