The so-called ring network refers to a ring-shaped distribution network, that is, a closed ring formed by the power supply trunk line. The power supply supplies power to the entire ring trunk line, and then distributes power to the outside through the high-voltage switch cabinet from the trunk line. The advantage of this is that each distribution branch can get power from both the left and right trunk lines. When one side of the trunk line fails, it continues to get power from the other right trunk line. In this way, although the total power supply is single-circuit power supply, each distribution branch line gets the benefits similar to dual-circuit power supply, thereby improving the reliability of power supply.
The so-called "ring network cabinet" means that each distribution branch line is equipped with a switch cabinet (outgoing switch cabinet), and the busbar of this switch cabinet is also part of the ring trunk line. That is to say, the ring trunk line is composed of the busbars of each outgoing cabinet connected together. Each outgoing cabinet is called a "ring network cabinet". In fact, the meaning of "ring network" cannot be seen by taking out a ring network cabinet alone.
The rated current of these ring network cabinets is not large, so the high-voltage switch of the ring network cabinet generally does not use a complex circuit breaker but a simple high-voltage load switch with a high-voltage fuse. In other words, the high-voltage switch in the ring network cabinet is generally a load switch. The ring network cabinet uses a load switch to operate the normal current and a fuse to cut off the short-circuit current. The combination of the two replaces the circuit breaker. Of course, this can only be limited to a certain capacity.
Such a switch cabinet can also be used in a non-ring network structure distribution system. With the widespread application of this switch cabinet, the "ring network cabinet" has jumped out of the scope of ring network distribution and generally refers to a high-voltage switch cabinet with a load switch as the main switch.
Main components of ring main unit
Switch device: usually load switch, isolating switch or circuit breaker is used to connect or disconnect the circuit.
Load switch: can operate with load, but cannot cut off short-circuit current.
Circuit breaker: has short-circuit protection function and can cut off fault current.
Fuse combination appliance: used for transformer protection, when short circuit occurs, the fuse blows quickly.
Bus: the conductive part connecting the incoming and outgoing lines.
Measurement and protection device: such as current transformer (CT), voltage transformer (PT), relay protection device, etc.
Casing: usually stainless steel or SF6 gas insulation is used to ensure safety and corrosion resistance.
Classification of ring main units
Ring network cabinets can be divided into indoor ring network and outdoor ring network. Indoor ring network is generally used for power distribution on the high-voltage side, and is composed of incoming line cabinet, metering cabinet, PT cabinet, and transformer outgoing line cabinet. For users with higher power requirements, the incoming line must use a dual power switching cabinet. Outdoor ring network is generally used in urban power grids, using a common box type SF6 ring network cabinet. The biggest feature of this cabinet type is its high protection level, which can reach IP67, is suitable for outdoor use, and can be immersed in water for a short time.
Characteristics of Ring Main Unit
Outdoor ring network cabinets generally use vacuum switches as disconnecting devices, SF6 gas common box insulation, compact structure, small footprint, beautiful appearance, and can coordinate with the surrounding environment. Due to the full sealing and full insulation concept, all switch parts in the RVAC ring network cabinet, including all high-voltage live parts and mechanism parts, are completely sealed in the main box, free from condensation and external dirty environment; the main box protection level can reach IP67, equipped with Cooper waterproof touchable cable head, which can effectively prevent occasional floods in rainy areas.
Common faults and solutions
| Fault phenomenon | Possible cause | Solution |
|---|---|---|
| Switch failure |
Mechanism stuck, control power failure |
Lubricate mechanical parts and check the power circuit |
| Partial overheating of cabinet |
Poor contact or overload |
Tighten the connecting bolts and check the load current |
| SF6 low pressure alarm |
Gas leakage |
Check for leaks and add air, replace the seals if serious |
| Insulation flashover | Insulator dirty or damp | Clean or replace the insulator |
contact us
If you are interested in ring main unit products, technical cooperation or procurement, and hope to communicate further, please let me know your specific needs (such as: technical parameters, purchase quantity, project address, etc.), I can help sort out key issues, email:pannie@hdswitchgear.com. whatsapp/wechat:+8618789455087.
