The same and differences between Ring Main Unit and Metal Clad in application

The Ring Main Unit is used in the ring network power supply to connect two power sources or parts of a switch cabinet. The main function is to split the two sections, with single function and small size. The center cabinet is a type of switch cabinet used by end users, with full functions and large volume. There are many types of middle cabinets, which can be divided into incoming and outgoing switch cabinets, metering cabinets, transformer cabinets, and used transformer cabinets. The switches in the middle cabinets can be equipped with automatic protection devices. In the event of an accident, the protection device sends out a signal to make the switch The action trips and cuts off the power supply. Most of the VS1 vacuum circuit breakers are used in the cabinet. Due to different uses, the structure and component selection of the two are very different.

In the power supply and distribution system, priority should be given to high-supply metering rather than low-voltage metering; low-voltage metering can only be considered when there is no way to install metering on the high-voltage side; at this time, the low-voltage metering cabinet should be placed on the “front” side. , That is, the front of the low-voltage incoming line and the back of the transformer, but the metering cabinet cannot be under the protection of the low-voltage incoming line cabinet, so under normal circumstances, it should be under the protection of the high-voltage switch of the transformer. In this case, both the ring network cabinet and the center cabinet can be used.

At present, the Ring Main Unit can not only be equipped with load switch-fuse combination electrical appliances, but also circuit breakers, such as domestic XGN, Schneider’s SM6, Siemens 8DJH, ABB’s SAFE, etc., and the secondary protection can be equipped with a microcomputer protection device. However, the circuit breaker installed in the ring main unit has a load limit, and the limits of the ring main unit of each manufacturer are different. Such as Schneider RM6 Ring Main Unit, the protection of the transformer’s high-voltage switch is greater than or equal to 2000KVA, and circuit breaker + VIP300 microcomputer protection must be used. The load on the incoming and outgoing lines of the central cabinet is not restricted.

Of course, with the development of the current power supply technology, both types of cabinets have developed greatly. The center cabinets are becoming smaller and smaller; the Ring Main Unit are becoming more and more functional; but in general, the center cabinets are used in The end user is the control equipment, but its price is relatively high; the ring network cabinet was originally designed to solve the problem of power supply and introduction, and its function is relatively simple, but its structure is simple, the volume is small, and the price is relatively low. Recently, the functions have been continuously expanded, especially its small size is easy to be installed inside the “box change”, so it has a very good development; currently the Ring Main Unit is not only used as a contact switch cabinet, but also can be used as a loop in and loop out switch Cabinet, metering cabinet, PT cabinet.
Therefore, specifically speaking, whether the two can be interchanged, due to the inconsistency of the functions and performance of the products of various manufacturers, it is not easy to say. In terms of cost reduction, the ring network cabinet has certain advantages. With the development of ring main unit technology, the application of ring main unit and center cabinet can overlap in many occasions. But in the high-voltage power distribution system with large currents above 1250A, the ring main cabinet cannot replace the center cabinet.