Low voltage distribution panel, also known as low-voltage switch panel or distribution cabinet, is a kind of combined electrical equipment that is installed in a metal cabinet according to a certain wiring scheme to control, protect, measure, distribute and monitor the switchgear, measuring instruments, protection devices and auxiliary equipment required by low-voltage circuits.
Suitable for power, distribution, and lighting distribution in low-voltage distribution systems with a rated working voltage not exceeding 4000V. The low-voltage distribution panel is the most widely used low-voltage complete device in power plants. Below is an introduction to the structural principle of ABB's MNS series low-voltage distribution panel. Tree Bird Education Electrical Designer Online Teaching Course
1、 Distribution cabinet frame
The switchgear is composed of independent single cabinets connected together by bolts, and the frame is shown in Figure 3. The bottom of the cabinet body is composed of 3mm aluminum zinc coated steel sheet firmly welded plates at the front and back. Each power distribution cabinet is precisely spliced with bolts by Vertical and horizontal C-shaped skeleton, and a firm structure is formed by using bolt connection and pressing plate design.
The C-shaped skeleton is punched at 25mm intervals according to German industrial standard 43660 and made of 2mm thick high-strength, stainless aluminum zinc coated steel plate. All frame parts are locked with thread forming Self-tapping screw. The distribution cabinet frame is of modular design. Functional units can be arranged at will only by changing the position of the compartment partition board. The top frame is equipped with lifting lugs.
The copper busbar is manufactured according to German industrial standards. The independent busbar compartment at the rear of the switchgear can install 3-phase or 4-phase horizontal busbar. MNS can use two busbar systems installed on the upper and lower floors of this busbar compartment. The distribution panel busbar is shown in Figure 4.
The MNS bus system has a unique design that uses bolts coated with ESLOK (a Loctite type compound), conical spring washers, and threaded plates, and is tightened using a torque wrench. This design has been certified maintenance free and is also suitable for on-site interconnections. All bus connections are operated from the front of the switchgear.
母线分为主母线和配电母线，主母线布置在开关柜的背部（母线小室内），可分为上下两层。双层主母线系统分别布置在上、下两层；单层主母线系统布置在上层或下层；主母线单联、串联、并联均可；母线材质为铜（Cu），截面积为30*10mm， 40*10mm， 60*10mm三种规格。配电母线用于功能单元组件与母线之间的连接，配电母线（垂直母线）分布在母线小室内，母线材质为铜（Cu），单根直角型铜牌，其截面为L型50*30*5mm。
The busbar is divided into main busbar and distribution busbar. The main busbar is arranged at the back of the switchgear (busbar compartment) and can be divided into upper and lower layers. The double-layer main busbar system is arranged on the upper and lower layers respectively; The single-layer main busbar system is arranged in the upper or lower layers; The main busbar can be connected in single, series, or parallel; The busbar material is copper (Cu), with a cross-sectional area of 30 * 10mm, 40 * 10mm, and 60 * 10mm. The distribution busbar is used for the connection between functional unit components and the busbar. The distribution busbar (vertical busbar) is distributed in the busbar compartment, and the busbar material is copper (Cu). A single right angle copper plate has an L-shaped section of 50 * 30 * 5mm.
3、 Multifunctional partition board
The distribution busbar (rectangular copper bar) is installed in an insulated multifunctional partition board, which, together with the entire busbar, can meet the requirements of electric shock protection level (IP20) without the need for additional partitions. The multifunctional partition board is shown in Figure 5.
Figure 5 Distribution Panel Partition Board
The multifunctional partition board has anti fault arc performance and also serves as an isolation between the device compartment and the busbar compartment. It can effectively isolate faulty arcs and prevent finger insertion (IP20), and has the functions of insulation, isolation, self extinguishing, flame retardant, arc extinguishing, and arc extinguishing.
The adapter unit facilitates the horizontal distribution of vertical distribution buses, allowing 4 or 2 outgoing functional units to be closely arranged in the same horizontal position of the switchgear, thereby optimizing the available space within the switchgear. The rated current of the four circuit adapter is 45A per circuit, and 63A per circuit for the two circuits. The adapter unit has reserved outgoing cables that can be connected to external outlets in the cable compartment. The adapter unit has two specifications: 3-pole and 4-pole, and each functional unit has 20 auxiliary terminals.
5、 Primary connector
A one-time connector is a precisely designed component, where each contact undergoes functional and pressure testing during the manufacturing process. The manufacturing date and contact pressure are then engraved on the contact assembly along with the serial number. The primary plug-in is tin plated with a rated current of 250A. The cable nose will vary depending on the size of the on-site cable. Each plug-in has a protective cover to ensure complete contact isolation before contact with the distribution bus.
6、 Cable wiring
The wiring positions of the incoming and outgoing cables and control lines are located on the right cable installation guide rail of the cable compartment, with the main circuit terminal located at the rear and the control line terminal located at a 45 ° direction in front of it. The wiring of control wire terminals can be connected with screws or plug-in wire noses, or with terminals. For withdrawable components with main circuit terminals less than 63A, the adapter is equipped with PE terminals.
The modular design of MNS switchgear is based on 25mm modular holes (according to German industrial standard 436600); The modulus is represented by the letter E, which means E=25mm. The height of the 8E drawer is 8x25mm=200mm. The component specifications are 8E/4, 8E/2, 8E, 16E, 24E, etc., as shown in Figure 7.
8、 Differences in various types of switchgear
Differences in lGCS, GCK, MNS, GGD switchgear
GGD is a fixed cabinet, while GCK, GCS, and MNS are drawer cabinets.
The drawer pushing mechanism of GCK cabinet is different from that of GCS and MNS cabinets;
The GCS cabinet can only be used as a single side operation cabinet, with a depth of 800mm,
MNS cabinet can be used as a double-sided operation cabinet with a depth of 1000mm.