1.MNS低压控制柜特点

　　1. Characteristics of MNS low-voltage control cabinet

　　抽屉式低压开关柜是发电厂、变电站内低压配电场所常用的配电装置。田湾核电站厂用电低压配电设备(0.4 kV 及其以下电压等级)均为抽屉式低压开关柜，选型以 ABB 生产的 MNS低压控制柜为主。MNS型低压开关柜主体框架结构基本上可免维护，安装相应规格的抽屉式组件，抽屉内部根据用户要求安装各种相应规格的电器标准元件。MNS低压控制柜具有如下特点：

　　Drawer type low-voltage switchgear is a commonly used distribution device in low-voltage distribution areas of power plants and substations. The low-voltage distribution equipment (0.4 kV and below) for the power plant of Tianwan Nuclear Power Plant are drawer type low-voltage switchgear, and the selection is mainly based on the MNS low-voltage control cabinet produced by ABB. The main frame structure of MNS type low-voltage switchgear is basically maintenance free, and drawer type components of corresponding specifications are installed. Various electrical standard components of corresponding specifications are installed inside the drawer according to user requirements. The MNS low-voltage control cabinet has the following characteristics:

　　(1)单个抽屉内故障电弧产生后不影响相邻的抽屉组件；

　　(1) The occurrence of a fault arc in a single drawer does not affect adjacent drawer components;

　　(2)内部元件布置紧凑，柜体空间利用率较高;

　　(2) Compact arrangement of internal components and high utilization of cabinet space;

　　(3)柜体地做到了免维护；

　　(3) The cabinet achieves maximum maintenance free operation;

　　(4)对操作人员人身具有可靠保障；

　　(4) Reliable guarantee for the personal safety of operators;

　　(5)具备防电弧能力；

　　(5) Capable of preventing electric arcs;

　　(6)电缆室控制电缆、动力电缆排列有序，便于检查维修。

　　(6) The control cables and power cables in the cable room are arranged in an orderly manner for easy inspection and maintenance.

　　2.MNS 型低压开关柜故障分析MNS低压控制柜主体框架结构已做到限度免维护，但随着抽屉运行时间的增加，部分开关零部件逐渐老化，开关柜的故障率也会有所增加。下面对 MNS 型抽屉式低压开关在使用中曾出现的一些故障现象进行介绍与分析。

　　2. Fault analysis of MNS low-voltage switchgear. The main frame structure of MNS low-voltage control cabinet has achieved maximum maintenance free, but with the increase of drawer operation time, some switch components gradually age, and the failure rate of the switchgear will also increase. Below is an introduction and analysis of some fault phenomena that have occurred in the use of MNS drawer type low-voltage switches.

　　2.1Emax 型断路器故障分析Emax型断路器即俗称的配电用自动空气开关，它起着母线配电盘柜与上游厂用变压器连接的重要作用。若自动空气开关动作跳闸，其所连接的整个母线配电盘及下游负荷均将失去电源，若母线段配有母联开关，则母联开关动作合闸，母线段将恢复供电。田湾核电站现场 400 V 低压配电盘柜的进线开关和母联开关均为Emax型塑壳式自动空气开关，主体框架结构相同，均为可抽出式，后接线方式。在现场实际的运行过程中，配电用自动开关曾出现如下故障。

　　2.1 Fault analysis of Emax type circuit breaker Emax type circuit breaker, commonly known as automatic air switch for distribution, plays an important role in connecting the busbar distribution panel cabinet with the upstream plant transformer. If the automatic air switch trips, the entire busbar distribution panel and downstream loads connected to it will lose power. If the busbar section is equipped with a busbar switch, the busbar switch will close and the busbar section will resume power supply. The incoming switch and bus tie switch of the 400V low-voltage distribution panel cabinet at Tianwan Nuclear Power Plant site are both Emax type plastic shell automatic air switches with the same main frame structure, both of which are withdrawable and have a rear wiring method. In the actual operation process on site, the automatic switch for power distribution has encountered the following faults.

　　2.1.1自动空气开关跳闸2006-09-25，1 号机组 1BFE 段母线进线开关突然跳闸，当时 1BFF 段母线正通过母联开关由 1BFE 母线供电，终导致 1BFE，1BFF 两段母线同时失去电源。现场检查，初步判定为 1BFE 母线进线断路器动作跳闸。调出进线开关脱扣器内的参数发现，长延时选择的额定电流为IN=250 A，整定值为I1=0.4IN=100 A，延时时间 t1=4 s。显然该设定值太小不符合要求。由于 1BFE 母线负荷电流增加，电子脱扣器内长延时保护动作，造成进线开关跳闸。根据调试大纲，要求所有低厂变侧(6 kV/0.4 kV)低压侧电源进线开关电子脱扣器保护设定值为：L 过载值；S 短路延时置 OFF；I 瞬时置 OFF，其余相关保护均要求闭锁。经核对，1BFE进线断路器额定容量为2 000 A。于是将长延时额定电流选择为IN=2 000 A，整定值调整为I1=1IN=2 000 A，延时时间 t1=114 s。随即又对 1BFF 母线段进线开关柜内的其它保护参数设定情况进行了检查，确认符合调试大纲要求，同时对 1 号机组其它低压开关柜进线开关电子脱扣器内的参数进行检查。当然还有其它因素可能会导致自动空气开关跳闸，具体如下：

　　2.1.1 Automatic air switch tripped on September 25, 2006. The incoming switch of the 1BFE section busbar of Unit 1 suddenly tripped. At that time, the 1BFF section busbar was being powered by the 1BFE busbar through the bus tie switch, ultimately causing both 1BFE and 1BFF sections of the busbar to lose power simultaneously. On site inspection has preliminarily determined that the 1BFE busbar incoming circuit breaker has tripped due to action. Upon retrieving the parameters from the incoming switch release, it was found that the rated current selected for long delay is IN=250 A, the set value is I1=0.4 IN=100 A, and the delay time t1=4 s. Obviously, the set value is too small and does not meet the requirements. Due to the increase in load current on the 1BFE busbar, the electronic release triggered a long delay protection, causing the incoming switch to trip. According to the debugging outline, it is required that the protection setting value of the electronic release of the power supply incoming switch on the low voltage side (6 kV/0.4 kV) of all low voltage plant transformers is: L overload value maximum; Short circuit delay set to OFF; Instantly set to OFF, all other related protections require locking. After verification, the rated capacity of the 1BFE incoming circuit breaker is 2000 A. Therefore, the long-term delay rated current is selected as IN=2000 A, the setting value is adjusted to I1=1 IN=2000 A, and the delay time t1=114 s. Subsequently, the settings of other protection parameters in the 1BFF bus section incoming switch cabinet were checked and confirmed to meet the requirements of the commissioning outline. At the same time, the parameters in the electronic release of the incoming switch in other low-voltage switch cabinets of Unit 1 were checked. Of course, there are other factors that may cause the automatic air switch to trip, as follows:

　　(1) 母线过负荷或相间短路，进线断路器过载保护或短路保护动作。若发生上述故障，母联开关备自投动作不成功，母线段彻底失去主回路电源。此时需检查母线段母排有无明显接地点或母线相间是否有短路现象。造成此类故障的主要原因有：①小动物进入配电柜内导致相间或相对地短路；②配电室内进水或母线被水淋湿造成母线绝缘降低。母线相间及各相对地线间绝缘值应大于 0.5 M Ω。

　　(1) Bus overload or phase to phase short circuit, incoming circuit breaker overload protection or short circuit protection action. If the above faults occur, the backup automatic switching action of the busbar switch will not be successful, and the busbar section will completely lose the main circuit power supply. At this point, it is necessary to check whether there is a clear grounding point on the busbar section or whether there is a short circuit between the busbars. The main reasons for such faults are: ① Small animals entering the distribution cabinet causing phase to phase or relative to ground short circuits; ② The insulation of the busbar is reduced due to water entering the distribution room or the busbar being soaked by water. The insulation value between busbars and between ground wires should be greater than 0.5 M Ω.

　　(2)就地人为误动分闸按钮或跳闸(trip)开关。在对低压开关进行定期巡检时，需经常性扳动进线开关控制柜面板上的电流表和电压表转换开关，以便记录当值母线运行电压和电流。由于跳闸开关旋钮与电压表或电流表的转换开关类似，且也在进线控制柜面板上，因而在巡检时很容易将其误认为是转换开关。2005 年 11 月，某员工在巡检 1BNA 母线时就错误地扳动了跳闸(trip)开关，导致1BNA母线段进线开关动作，母线失电。显然这也是MNS型低压开关柜在设计上存在的缺陷。为防止以后再次发生类似事故，在就地分合闸按钮或跳闸开关上加装了透明保护盖。

　　(2) Manually operate the trip button or trip switch on site. When conducting regular inspections of low-voltage switches, it is necessary to frequently turn the ammeter and voltmeter switch on the incoming switch control cabinet panel to record the operating voltage and current of the duty bus. Due to the fact that the trip switch knob is similar to the conversion switch of a voltmeter or ammeter and is also located on the incoming control cabinet panel, it is easy to mistake it for a conversion switch during inspection. In November 2005, an employee mistakenly turned the trip switch while inspecting the 1BNA busbar, causing the incoming switch of the 1BNA busbar section to operate and the busbar to lose power. Obviously, this is also a design flaw in the MNS type low-voltage switchgear. To prevent similar accidents from happening again in the future, transparent protective covers have been installed on the on-site opening and closing buttons or trip switches.

　　(3)控制系统误触发跳闸信号。若进线开关跳闸后经仔细检查未发现开关本身有故障，则需对控制系统进行检查，确认有无跳闸信号触发，潜在的隐患。

　　(3) The control system mistakenly triggered a trip signal. If the incoming switch trips and no fault is found in the switch itself after careful inspection, the control system needs to be checked to confirm whether there is a tripping signal triggering and eliminate potential hazards.

　　2.1.2自动空气开关无法合闸原因分析：

　　2.1.2 Analysis of the reasons why the automatic air switch cannot be closed:

　　(1)储能弹簧未储能或未储能完全。这种情况主要是发生在手动合闸时，可能是由于操作人员不熟悉手动合闸操作步骤造成的。此时需对空气开关再次手动储能，当听到“当”的响声时，表示储能完全，即可手动合闸。

　　(1) The energy storage spring has not stored energy or has not stored energy completely. This situation mainly occurs during manual closing, which may be due to the operator's unfamiliarity with the manual closing operation steps. At this point, the air switch needs to be manually charged again. When a "when" sound is heard, it indicates that the charging is complete and the switch can be manually closed.

　　(2)空气开关上兰色按钮(跳闸机械指示)弹出。产生这种现象的原因主要是空气开关上次是由于故障跳闸断开，跳闸机械指示弹出。将其复位后，再对其进行合闸操作即可。

　　(2) The blue button (trip mechanical indicator) on the air switch pops up. The main reason for this phenomenon is that the air switch was tripped and disconnected due to a fault last time, and the mechanical indication of the trip popped up. After resetting it, perform a closing operation on it.

　　(3)储能电机损坏。主要原因可能是由于控制系统电压不稳导致电机损坏或储能电机使用年久老化造成。此时需检查储能电机的绝缘及直阻是否满足要求，若确认电机损坏则应更换。

　　(3) The energy storage motor is damaged. The main reason may be due to unstable voltage in the control system causing motor damage or aging of the energy storage motor over time. At this point, it is necessary to check whether the insulation and direct resistance of the energy storage motor meet the requirements. If it is confirmed that the motor is damaged, it should be replaced.

　　(4)控制电源异常，储能电机无法电动储能。主要原因可能是进线开关二次回路接线端子接触不良或控制回路电源失去。需确认控制回路电源是否正常，然后再检查接线端子接触是否良好。故障，将开关置于合闸位，储能电机即自动储能。

　　(4) The control power supply is abnormal, and the energy storage motor cannot store energy electrically. The main reason may be poor contact of the secondary circuit terminal of the incoming switch or loss of power supply to the control circuit. Firstly, it is necessary to confirm whether the control circuit power supply is normal, and then check whether the wiring terminals are in good contact. Eliminate the fault, place the switch in the closed position, and the energy storage motor will automatically store energy.

　　2.2抽屉式负荷开关常见故障分析抽屉开关经常要根据系统负荷的需求而改变运行方式，也就是要进行断电或送电等操作，因而经过一段时间的运行之后，抽屉开关内部电气回路或机械部分难免会出现一些故障。

　　2.2 Common Fault Analysis of Drawer Load Switches Drawer switches often need to change their operating mode according to the demand of the system load, that is, to perform power-off or power on operations. Therefore, after a period of operation, the internal electrical circuit or mechanical parts of the drawer switch are inevitably prone to some faults.

　　2.2.1常见电气故障分析2.2.1.1 抽屉内负荷跳闸或故障报警这是由于负荷过载造成的。主要原因：

　　2.2.1 Common Electrical Fault Analysis 2.2.1.1 Load Trip or Fault Alarm in Drawer This is caused by load overload. main cause:

　　(1)抽屉开关下游电气设备有接地或短路现象。此时需检查负荷电缆是否破损，绝缘是否偏低等；

　　(1) The electrical equipment downstream of the drawer switch is grounded or short circuited. At this point, it is necessary to check whether the load cable is damaged, whether the insulation is too low, etc;

　　(2)下游转动设备，像电动阀门、水泵、风机等有堵转现象；

　　(2) Downstream rotating equipment, such as electric valves, water pumps, fans, etc., have blockage phenomena;

　　(3)热偶 SK-10 或热继电器本身机械故障。在以往的维修经历中发现，开关热偶或热继动作的缺陷占的比例较大，尤其是电动阀门开关抽屉，电动阀门就地一过力矩，抽屉开关热偶就可能动作。若是由于负荷故障导致热偶动作，负荷故障后，将抽屉开关旋钮拧到分闸位，重新合闸，即可对热偶进行复位。对于热继电器，则可通过抽屉面板上的复位按钮复位。

　　(3) Mechanical failure of thermocouple SK-10 or thermal relay itself. In previous maintenance experiences, it has been found that a large proportion of defects are caused by the action of switch thermocouples or relays, especially when opening or closing drawers with electric valves. Once the electric valve passes the torque on site, the drawer switch thermocouples may move. If the thermocouple operates due to a load fault, after eliminating the load fault, turn the drawer switch knob to the open position and close it again to reset the thermocouple. For thermal relays, they can be reset through the reset button on the drawer panel.

　　2.2.1.2抽屉合闸送电后主控或就地无送电显示主要原因如下：抽屉间隔内二次回路端子脱落。二次端子两侧固定卡片磨损，在抽屉开关推入的过程中，抽屉间隔二次端子脱离固定位置。此时需更换端子排。这种故障现象在现场曾多次发生，多数情况下都是由于在送电的过程中对开关操作不当。送电前需对抽屉间隔进行仔细检查，若二次端子已经松动或脱落，应及时进行维修。

　　The main reason for the lack of power transmission display in the main control or on-site after the drawer is closed and powered on is as follows: the secondary circuit terminal in the drawer compartment has fallen off. The fixed cards on both sides of the secondary terminal are worn, and during the process of pushing in the drawer switch, the secondary terminal of the drawer is separated from the fixed position. At this point, it is necessary to replace the terminal block. This fault phenomenon has occurred multiple times on site, mostly due to improper operation of the switch during power transmission. Before power transmission, it is necessary to carefully inspect the drawer spacing. If the secondary terminal has become loose or detached, it should be repaired in a timely manner.

　　(2)控制回路 220 V 交流电源失去或 24 V 直流信号电源失去。可能的原因有：① 二次回路端子排上接线松动或脱落；② 开关内部二次回路保险管熔断。此时应检查开关内二次接线回路绝缘是否异常；③ 开关内部二次回路空开 Q1 未合闸，这一点在送电前对开关进行仔细检查就可以避免。

　　(2) The control circuit loses 220 V AC power supply or 24 V DC signal power supply. Possible reasons include: ① Loose or detached wiring on the secondary circuit terminal block; ② The fuse of the secondary circuit inside the switch is blown. At this point, it is necessary to check whether the insulation of the secondary wiring circuit inside the switch is abnormal; ③ The secondary circuit air switch Q1 inside the switch is not closed, which can be avoided by carefully checking the switch before power transmission.

　　(3)抽屉内部主开关辅助触点故障导致合闸信号未发出。此时应采取如下措施：① 检查主开关Q0辅助触点各常开、常闭接点是否正常。若异常则更换备件；② 检查辅助触点与主开关的机械配合是否紧凑。若辅助触点脱落或松动也将导致合闸后无送电显示，此时需重新对辅助触点进行安装

　　(3) The auxiliary contact of the main switch inside the drawer malfunctioned, causing the closing signal to not be sent out. At this point, the following measures should be taken: ① Check whether the normally open and normally closed contacts of the auxiliary contacts of the main switch Q0 are normal. If there is an abnormality, replace the spare parts; ② Check if the mechanical fit between the auxiliary contacts and the main switch is tight. If the auxiliary contact falls off or becomes loose, it will also cause no power transmission display after closing, and the auxiliary contact needs to be reinstalled at this time

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