The difference between central cabinet and ring main unit

2024-11-06 10:47:43

The center cabinet is a type of switch cabinet used by end users. It has full functions and is the power receiving unit of the 10KV system distribution room. The circuit breaker and metering unit can be removed. It is a trolley-type structure. The protection of incoming lines and feeders is relatively complete. The rated current is generally 630~3150A; it is large in size, and the ring network cabinet is used in the ring network to connect two power sources or parts. Most of them are vacuum or SF6 gas insulated load switches, and there are also gas-generating load switches. The protection amount is small or no protection is required during use, but the rated current is generally 630~1250A. Most of the protection is achieved by fuses, and some products also have circuit breaker solutions. It is mainly used in systems below 1000KVA transformers. The main function is to divide the two sections, with a single function and a small size;

Because of their different uses, the structures and component selection of the two are very different; there are many types of central cabinets, which can be divided into inlet and outlet switch cabinets, metering cabinets, transformer cabinets, transformer cabinets, etc. The switches in the central cabinet can be equipped with automatic protection devices. In case of an accident, the protection device sends a signal to trip the switch and cut off the power supply. The cabinet mostly uses VS1 type vacuum circuit breakers; while the ring network cabinet is mainly a connecting switch cabinet. There is generally no protection device in the ring network cabinet. In case of an accident, the internally installed fuse overheats and melts, cutting off the circuit. The switch is mostly a user-internal exchange high-voltage load switch-fuse combination electrical appliance, or sulfur hexafluoride load switch; the function of the ring network cabinet is single, that is, it is used to connect different power supply parts, and it is generally not used to realize the control, protection and metering of specific power equipment; if these functions are really needed, the central cabinet should be selected;
In the power supply and distribution system, high-voltage metering should be given priority, and low-voltage metering should not be considered; low-voltage metering can only be considered when there is really no way to install metering on the high-voltage side; at this time, the low-voltage metering cabinet should be placed at the "front", that is, in front of the low-voltage incoming line and behind the transformer. However, the metering cabinet cannot be under the protection of the low-voltage incoming line cabinet. Therefore, under normal circumstances, it should be under the protection of the high-voltage switch of the transformer, so a central cabinet should be used. With the development of current power supply technology, both types of cabinets have developed greatly. The center cabinet is becoming more and more compact; the ring network cabinet is becoming more and more functional; but generally speaking, the center cabinet is used by end users and is a control device, but its price is relatively high; the ring network cabinet was originally designed to solve the problem of power supply extraction and introduction. The function is relatively simple, but its structure is simple, the volume is small, and the price is relatively low. Recently, the function has been continuously expanded, especially its small volume is easy to be installed inside the "box transformer", so it has developed very well;

At present, the ring network cabinet is not only used as a connection switch cabinet, but also as a ring input and output switch cabinet, metering cabinet, and PT cabinet. At present, the ring network cabinet can not only be equipped with load switch-fuse combination electrical appliances, but also circuit breakers, such as domestic HXGN, Schneider's SF6, Siemens 8DH, etc., and the secondary protection can be equipped with a microcomputer protection device. However, there is a load limit for installing a circuit breaker in the ring network cabinet, and the limits of each manufacturer's ring network cabinet are different. For example, for Schneider RM6 ring main unit, if the protection of the high voltage switch of the transformer is greater than or equal to 2000KVA, it is necessary to adopt circuit breaker + VIP300 microcomputer protection. However, the inlet and outlet loads of the central cabinet are not restricted. Therefore, it is difficult to say whether the two can be interchanged, because the product functions and performances of each manufacturer are inconsistent. When designing, the difference in rated current must be considered. Generally, a ring main unit is used when the total capacity exceeds 1250kVA.