文献翻译封面

南 昌 工 程 学 院

级毕业（设计）论文文献翻译

题 目

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

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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 to

0kV, the

circuit grounding grid, which non

fault

phase voltage

is common

in normal

operation

condition. Grounding, fault phase voltage is reduced, the grounding metalcompletely reduced

increases, metal fullygrounding for line for

to produce

small zero deal

current

sequence current this device,through with through

the the arc

voltage rise. Some Substation & "selection grounding detection device &", according grounding, can judge the operations

of

the grounding line. If

the substation without

staff elected grounding line, to

maintenance an

in two

phase

timely dispatch notification line grounding often cause grounding, resulting Firstly, according

to

personnel. Because

explosion, bus short

circuit, especially

arrester voltage the ground can

pull no

transformer oiltemperature heating, easy to damage the equipment, causing line another point causeintermittent network voltage should not be increased.

the operation

experience and choice principle, first

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.

The skilled operation mode. If a substation, the normal mode two main transformers in parallel operation, grounding, usually disconnected sectional breaker to narrow the search for ground range. Once, a main

maloperation of sectional transformer,grounding, the operating section of personnel of busbar voltage breakermisoperation, caused a

loss. Before the operationshould fully consider the power balance, protection coordination, arc suppression coil voltage adjustment, whether qualified problem.

After the transformer outlet circuit breaker in one by one to pull close, ground notselected. Probably because the bus and bus of substation owned equipment grounding or two back to the outlet with a grounding.

The choice has the power line, the first small hydropower solution column, so as to avoid the "crash" accident.

The one loop tripping, appear at the same time the bus bar grounding. Try to send the loop is usually not successful. The reason is: if a circuit is connected with the occurrence of A, B, C two relative to the increase of the voltage, often caused by another circuit insulation weak occurs at the B phase or C phasebreakdown, the formation of two-phase earth short circuit. Because of current transformer connection method for incomplete star, have a 2/3 chance of only the removal of a line. At this time, to compare the two circuit transmission lineload size and properties, send a return line. If the line instantaneous grounding,try to send success, does not exist the problem of selecting circuit.

The selected ground line, should inform the distribution personnel to handle as soon as possible, substation attendant to want to strengthen the equipmentinspection work.

(4) wire loop phase deficient operation, the electric effects of bus voltagesignificantly in grid. 35kV substation load is small, long branch distribution line, aloop of a phase drop fuse, if the branch load is bigger, the fault phase voltageincrease of load rejection, the non fault phase voltage is reduced. If the branchload is small, the line is capacitive, or for small power Internet line, fault phaselose capacitor or power, thus the voltage is reduced, the non fault phase voltageof fault phase voltage is high, the influence of bus voltage balance in a certain extent. Select the loop after notification distribution personnel processing.

(5) most of the 35kV rural substation in and out line and transformer high-voltage side using a drop fuse instead of circuit breaker, happen to fall off a single phase fusing or line break, the Rural Power Grid Substation busbar voltage unbalance.The transformer phase deficient operation of the abnormal noise, current faultphase 0. The operating personnel should

(6) line be timely replacement three-phase of fuse element,if affect the thebus line broken, the substation all blackout, notify the relevant personnel patrol line, processing. asymmetry parameter, the load imbalance may

voltage balance. My bureau of substation

maintenance, will 35kV three-phase voltage are be co - Tang - 199km respectively 21kV, 18kV, 21kV, spring long Xing - Song

- match line exit after the operation, the three-phase voltage is 21kV, the main line is not perfect, the transposition of the line parameters caused by the unbalanced.

小接地电流系统

小电流接地系统--小电流接地系统：中性点不接地或经过消弧线圈和高阻抗接地的三相系统，又称中性点间接接地系统。当某一相发生接地故障时，由于不能构成短路回路，接地故障电流往往比负荷电流小得多，所以这种系统被称为"小电流接地系统"。

1划分标准

在我国划分标准:X0/X1>4～5的系统属于小接地电流系统 （美国和西欧X0/X1>3的系统属于小接地电流系统）其中:X0为系统零序电抗,X1为系统正序电抗。 2小电流接地系统电压不平衡的原因分析

在实际运行中，常会监视到母线电压不平衡的现象，引起母线电压不平衡的原因很多，处理的办法因故障而异。 (1)母线电压互感器一相二次熔丝熔断。现象为中央信号警铃响，电压互感器一相电压为零，另外两相电压正常。如10kV母线三相电压为0kV，6.1kV，6.1kV。处理对策：退出低压等与该互感器有关的保护，更换二次熔丝。

(2)母线电压互感器一相一次熔丝熔断。从电压表反应出一相电压大幅度降低，其他两相电压有不同程度的降低。我局青海湖变母线电压为6.7kV，5.2kV，2.5kV，退出电压互感器检查发现C相一次熔丝熔断，更换之后，投入运行，电压恢复正常。

(3)出线回路发生接地，这是电网常见的不正常运行状态。发生接地时，故障相对地电压降低，金属性的完全接地时降为0kV，非故障相对地电压升高，金属性的完全接地时升为线电压。有的变电所有&"小电流接地选检装置&"，根据接地时产生零序电流，能判断出接地的线路。若变电所内无此装置，则通过运行人员的操作选出接地线路之后，通过及时调度通知线路维护人员去处理。因为接地时常引起母线避雷器爆炸、电压互感器发热喷油、高温的电弧容易损坏设备，引起线路另一点接地，造成两相短路，尤其是间歇性的接地还能引起网络电压不应有的升高。

①要根据运行经验及选检原则，先拉无电源、分支最多、线路最长、负荷最轻和无重要用户的线路，后拉分支较少、线路最短、负荷较重和重要用户的线路。 ②熟练掌握运行方式。如某一变电所，正常方式下两台主变并列运行，接地时，通常断开分段断路器来缩小查找接地的范围。有一次，一台主变，发生接地，运行人