Introduction to the application of ring main unit

The ring main unit refers to the ring power distribution network, that is, the power supply mains form a closed ring, and the power supply supplies power to the ring mains, from the mains all the way to the outside through the high-voltage switch. The advantage of this is that each power distribution branch can take power from its left main line, and it can take power from its right main line. When the left main line fails, it continues to receive power from the right main line, and when the right main line fails, it continues to receive power from the left main line. In this way, even though the main power supply is single-circuit power supply, However, from each distribution branch, the benefits similar to dual power supply are obtained, thereby improving the reliability of power supply.

The so-called "ring main unit" is to set up a switchgear (outgoing switchgear) for each distribution branch, and the busbar of this switchgear is also a part of the ring main line. In other words, the ring trunk line is composed of the bus bars of each outlet cabinet. Each outlet cabinet is called a "ring network cabinet". In fact, if you take out a ring network cabinet alone, you can't see the meaning of "ring network".

The rated current of these ring main units is not large, so the high-voltage switch of the ring main unit generally does not use a circuit breaker with a complicated structure, but a high-voltage load switch with a high-voltage fuse with a simple structure. In other words, the high-voltage switch in the ring main unit is generally a load switch. The ring main unit uses a load switch to operate the normal current and a fuse to cut the short-circuit current. The combination of the two replaces the circuit breaker. Of course, this can only be limited to a certain capacity.

The ring main unit did not appear for a long time, but it has been widely used. This is mainly due to the newly developed buildings of industrial enterprises and institutions. From the perspective of power supply and distribution, medium and small capacity are the largest. Most of its distribution transformers generally do not exceed 1250KVA, long-term stable power supply, and high-voltage switches are not frequently operated. For such users, the performance of the ring main unit is not perfect, but it is adequate. With the large-scale urban construction, a large number of large-scale high-rise buildings have been erected, and the substations are often located downstairs. According to the fire protection requirements, the substation and distribution equipment must be "oil-free", and be used reasonably according to the construction area. , Transformer and distribution equipment should be "miniaturized", so ring main units or vacuum circuit breakers, dry-type transformers, and dry-type transformers have entered each building. The ring network cabinet has simple structure, reliable and safe operation, small maintenance, and low operating cost. Compared with switch cabinets equipped with circuit breakers, it has outstanding advantages. The ring main unit requires the load switch to have higher performance and smaller size. A new type of load switch came into being, which in turn led to the technological progress of the ring main unit. Today's ring main unit is not only excellent in performance but also serialized , Which expands the scope of use of the ring main unit.