The 10kV ring main unit is a crucial equipment in the power distribution system. It is mainly responsible for steadily delivering high voltage electricity of 10 kV or 35 kV to users, so that everyone can have access to electricity. Not only that, it can also constantly monitor the transformers in the power system and control them to ensure their normal operation. Because it undertakes these important tasks, the 10kV ring main unit has the characteristics of high voltage level and large capacity. However, its size and weight are not large, making it very convenient to use. Next, let's take everyone to get to know the 10kV distribution ring main unit and understand its various aspects.
A ring main unit is an electrical equipment consisting of a set of high-voltage switchgear installed inside a steel plate metal cabinet or assembled into an interval type ring main power supply unit. Its core part uses load switches and fuses, and has the advantages of simple structure, small size, low price, improved power supply parameters and performance, and power supply safety.
In fact, if the cabinet type is classified according to switchgear, there are load switchgear, circuit breaker cabinets, GIS, etc., but no ring main unit. Ring main unit is a commonly used term, originally referring to load switchgear used for ring network power supply. Nowadays, it is often used as a synonym for load switchgear, regardless of whether it is used for ring network power supply. For example, some lines need to be operated in a closed loop (commonly known as hand-in-hand), or distribution cabinets that may perform load cutover (switching loads from one line to another) to achieve these functions are called ring main units. Therefore, the ring main unit is a type of switchgear that can achieve ring power supply and is commonly used in ring power supply systems. Therefore, it is commonly known as the ring main unit, also known as the "outdoor box type ring main unit" or "switchgear".
Load switch cabinets can be used for ring network power supply, medium voltage boundary room dispatching, and medium voltage terminal substation power supply. The specifications of transformers allowed to use load switches with fuse protection vary among power supply departments in different regions. For example, in Beijing, the transformer capacity is generally required to be no more than 1000KVA, while in Shenzhen, it may be 1600KVA. The load switch cabinet has a simple structure, low cost, and small size. Most of them can be installed against the wall and generally only have fuse protection without relay protection.
The current carrying capacity of the main busbar of the load switch cabinet is generally less than or equal to 630A, and the rated breaking current of the load switch is generally less than or equal to 630A (with a few reaching 1700A). The rated current (fuse) of the transformer cabinet (outgoing cabinet) is generally not greater than 125A, and the transfer current of the high-end load switch can reach 2800A. Some load switch cabinets can be equipped with dedicated vacuum circuit breakers, SF6 circuit breakers or use arc extinguishing methods such as compressed air, and the short-circuit breaking capacity is close to or reaches the level of the switch cabinet. Ring main unit is used for dividing and combining load current, breaking short-circuit current and transformer no-load current, charging current of overhead lines and cable lines at a certain distance, playing a control and protection role, and is an important switch equipment for ring network power supply and terminal power supply.
