1.MNS低壓控制柜特點

　　1. Characteristics of MNS low-voltage control cabinet

　　抽屜式低壓開關柜是發電廠、變電站內低壓配電場所常用的配電裝置。田灣核電站廠用電低壓配電設備(0.4 kV 及其以下電壓等級)均為抽屜式低壓開關柜，選型以 ABB 生產的 MNS低壓控制柜為主。MNS型低壓開關柜主體框架結構基本上可免維護，安裝相應規格的抽屜式組件，抽屜內部根據用戶要求安裝各種相應規格的電器標準元件。MNS低壓控制柜具有如下特點：

　　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)單個抽屜內故障電弧產生后不影響相鄰的抽屜組件；

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

　　(2)內部元件布置緊湊，柜體空間利用率較高;

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

　　(3)柜體非常大程度地做到了免維護；

　　(3) The cabinet achieves maximum maintenance free operation;

　　(4)對操作人員人身安全具有可靠保障；

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

　　(5)具備防電弧能力；

　　(5) Capable of preventing electric arcs;

　　(6)電纜室控制電纜、動力電纜排列有序，便于檢查維修。

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

　　2.MNS 型低壓開關柜故障分析MNS低壓控制柜主體框架結構已做到非常大限度免維護，但隨著抽屜運行時間的增加，部分開關零部件逐漸老化，開關柜的故障率也會有所增加。下面對 MNS 型抽屜式低壓開關在使用中曾出現的一些故障現象進行介紹與分析。

　　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 型斷路器故障分析Emax型斷路器即俗稱的配電用自動空氣開關，它起著母線配電盤柜與上游廠用變壓器連接的重要作用。若自動空氣開關動作跳閘，其所連接的整個母線配電盤及下游負荷均將失去電源，若母線段配有母聯開關，則母聯開關動作合閘，母線段將恢復供電。田灣核電站現場 400 V 低壓配電盤柜的進線開關和母聯開關均為Emax型塑殼式自動空氣開關，主體框架結構相同，均為可抽出式，后接線方式。在現場實際的運行過程中，配電用自動開關曾出現如下故障。

　　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自動空氣開關跳閘2006-09-25，1 號機組 1BFE 段母線進線開關突然跳閘，當時 1BFF 段母線正通過母聯開關由 1BFE 母線供電，非常終導致 1BFE，1BFF 兩段母線同時失去電源。現場檢查，初步判定為 1BFE 母線進線斷路器動作跳閘。調出進線開關脫扣器內的參數發現，長延時選擇的額定電流為IN=250 A，整定值為I1=0.4IN=100 A，延時時間 t1=4 s。顯然該設定值太小不符合要求。由于 1BFE 母線負荷電流增加，電子脫扣器內長延時保護動作，造成進線開關跳閘。根據調試大綱，要求所有低廠變側(6 kV/0.4 kV)低壓側電源進線開關電子脫扣器保護設定值為：L 過載值非常大；S 短路延時置 OFF；I 瞬時置 OFF，其余相關保護均要求閉鎖。經核對，1BFE進線斷路器額定容量為2 000 A。于是將長延時額定電流選擇為IN=2 000 A，整定值調整為I1=1IN=2 000 A，延時時間 t1=114 s。隨即又對 1BFF 母線段進線開關柜內的其它保護參數設定情況進行了檢查，確認符合調試大綱要求，同時對 1 號機組其它低壓開關柜進線開關電子脫扣器內的參數進行檢查。當然還有其它因素可能會導致自動空氣開關跳閘，具體如下：

　　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) 母線過負荷或相間短路，進線斷路器過載保護或短路保護動作。若發生上述故障，母聯開關備自投動作不成功，母線段有效失去主回路電源。此時需檢查母線段母排有無明顯接地點或母線相間是否有短路現象。造成此類故障的主要原因有：①小動物進入配電柜內導致相間或相對地短路；②配電室內進水或母線被水淋濕造成母線絕緣降低。母線相間及各相對地線間絕緣值應大于 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)就地人為誤動分閘按鈕或跳閘(trip)開關。在對低壓開關進行定期巡檢時，需經常性扳動進線開關控制柜面板上的電流表和電壓表轉換開關，以便記錄當值母線運行電壓和電流。由于跳閘開關旋鈕與電壓表或電流表的轉換開關類似，且也在進線控制柜面板上，因而在巡檢時很容易將其誤認為是轉換開關。2005 年 11 月，某員工在巡檢 1BNA 母線時就錯誤地扳動了跳閘(trip)開關，導致1BNA母線段進線開關動作，母線失電。顯然這也是MNS型低壓開關柜在設計上存在的缺陷。為防止以后再次發生類似事故，在就地分合閘按鈕或跳閘開關上加裝了透明保護蓋。

　　(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)控制系統誤觸發跳閘信號。若進線開關跳閘后經仔細檢查未發現開關本身有故障，則需對控制系統進行檢查，確認有無跳閘信號觸發，消除潛在的隱患。

　　(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自動空氣開關無法合閘原因分析：

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

　　(1)儲能彈簧未儲能或未儲能完全。這種情況主要是發生在手動合閘時，可能是由于操作人員不熟悉手動合閘操作步驟造成的。此時需對空氣開關再次手動儲能，當聽到“當”的響聲時，表示儲能完全，即可手動合閘。

　　(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)空氣開關上蘭色按鈕(跳閘機械指示)彈出。產生這種現象的原因主要是空氣開關上次是由于故障跳閘斷開，跳閘機械指示彈出。將其復位后，再對其進行合閘操作即可。

　　(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)儲能電機損壞。主要原因可能是由于控制系統電壓不穩導致電機損壞或儲能電機使用年久老化造成。此時需檢查儲能電機的絕緣及直阻是否滿足要求，若確認電機損壞則應更換。

　　(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)控制電源異常，儲能電機無法電動儲能。主要原因可能是進線開關二次回路接線端子接觸不良或控制回路電源失去。首先需確認控制回路電源是否正常，然后再檢查接線端子接觸是否良好。消除故障，將開關置于合閘位，儲能電機即自動儲能。

　　(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抽屜式負荷開關常見故障分析抽屜開關經常要根據系統負荷的需求而改變運行方式，也就是要進行斷電或送電等操作，因而經過一段時間的運行之后，抽屜開關內部電氣回路或機械部分難免會出現一些故障。

　　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常見電氣故障分析2.2.1.1 抽屜內負荷跳閘或故障報警這是由于負荷過載造成的。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)抽屜開關下游電氣設備有接地或短路現象。此時需檢查負荷電纜是否破損，絕緣是否偏低等；

　　(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)下游轉動設備，像電動閥門、水泵、風機等有堵轉現象；

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

　　(3)熱偶 SK-10 或熱繼電器本身機械故障。在以往的維修經歷中發現，開關熱偶或熱繼動作的缺陷占的比例較大，尤其是電動閥門開關抽屜，電動閥門就地一過力矩，抽屜開關熱偶就可能動作。若是由于負荷故障導致熱偶動作，消除負荷故障后，將抽屜開關旋鈕擰到分閘位，重新合閘，即可對熱偶進行復位。對于熱繼電器，則可通過抽屜面板上的復位按鈕復位。

　　(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抽屜合閘送電后主控或就地無送電顯示主要原因如下：抽屜間隔內二次回路端子脫落。二次端子兩側固定卡片磨損，在抽屜開關推入的過程中，抽屜間隔二次端子脫離固定位置。此時需更換端子排。這種故障現象在現場曾多次發生，多數情況下都是由于在送電的過程中對開關操作不當。送電前需對抽屜間隔進行仔細檢查，若二次端子已經松動或脫落，應及時進行維修。

　　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 交流電源失去或 24 V 直流信號電源失去。可能的原因有：① 二次回路端子排上接線松動或脫落；② 開關內部二次回路保險管熔斷。此時應檢查開關內二次接線回路絕緣是否異常；③ 開關內部二次回路空開 Q1 未合閘，這一點在送電前對開關進行仔細檢查就可以避免。

　　(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)抽屜內部主開關輔助觸點故障導致合閘信號未發出。此時應采取如下措施：① 檢查主開關Q0輔助觸點各常開、常閉接點是否正常。若異常則更換備件；② 檢查輔助觸點與主開關的機械配合是否緊湊。若輔助觸點脫落或松動也將導致合閘后無送電顯示，此時需重新對輔助觸點進行安裝

　　(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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