As a set of power transmission and distribution electrical equipment, The Ring Main Unit(RMU) plays a crucial and significant role in the power system. It is mainly applied in the distribution substations of load centers such as urban residential communities, high-rise buildings, large public buildings, factories and enterprises, as well as in box-type substations.
In these scenarios, the ring main unit is used to achieve the control and protection of the circuit. For example, in an urban residential community, the ring main unit can rationally distribute the electrical energy from the superior substation to each residential building. Through its opening and closing functions, it ensures that during the normal operation of the power system, the current is stably transmitted to every household. At the same time, when faults such as overload and short circuit occur, it can quickly cut off the circuit, protect the safety of equipment and lines, prevent the expansion of the fault range, and ensure the reliability of residents' power supply. In factories and enterprises, the ring main unit can accurately control the power supply according to the power consumption requirements of different production equipment. Moreover, when there are abnormal power consumption situations of the equipment, it will act promptly to avoid serious impacts on production due to power problems.
Components of the Ring Main Unit
- Cabinet Body: The main structure of the ring main unit is generally made of metal materials, with the characteristics of dust prevention, water prevention, and corrosion prevention. It provides a safe and stable operating environment for other equipment inside the cabinet, resisting the interference of adverse external factors.
- Busbar Chamber: Usually arranged at the upper part of the cabinet body, the main busbars are connected to each other in this chamber and run through the entire row of switchgear cabinets. The busbars are generally arranged horizontally for easy subsequent expansion. The busbar chamber realizes the collection and distribution of electric power, integrating the electrical energy from different power sources or directions and then transmitting it to each branch circuit as required.
- Load Switch (or Circuit Breaker Chamber): The load switch chamber is equipped with a load switch. Its housing is commonly made of epoxy resin, and SF6 gas is filled inside as the arc extinguishing and insulating medium. The contact state can be observed through the transparent hot-pressed plastic end caps at the front end of the operating shaft. The circuit breaker chamber is located in the middle of the cabinet body, and a vacuum circuit breaker or an SF6 circuit breaker can be configured according to customer requirements to meet the requirements of normal opening and closing, branch network operation, and cutting off the short-circuit current under special circumstances. In particular, the vacuum circuit breaker is suitable for network systems with frequent operations. This part is the key component of the ring main unit to achieve the functions of circuit opening and closing.
- Cable Chamber: It is mainly used for cable connection and can connect single-core or three-core cables. It has a spacious space and can accommodate components such as arresters, current transformers, and lower grounding switches. The cabinet door is equipped with an observation window and a safety interlock device, and the floor of the chamber is equipped with a sealing cover and a cable clamp of appropriate size with a bracket. The front door frame of the floor can be removed to facilitate cable installation, realizing a reliable connection between the ring main unit and the external cable lines.
- Operating Mechanism: Such as the spring operating mechanism, it provides power for the action of the load switch or circuit breaker, realizing the opening and closing operations of the equipment. Moreover, some operating mechanisms have the function of reclosing, with reliable actions and a long service life.
- Interlocking Mechanism: Installed inside the ring main unit, it is used to ensure the correctness of the sequence and safety of each operation step, preventing misoperation. For example, the interlocking relationship among the grounding switch, load switch, and cabinet door guarantees the safety of operators and equipment.
- Low-voltage Control Room (Interlocking Low-voltage Chamber): It also functions as a control panel. Inside, there are a spring operating mechanism and a mechanical interlocking device (with a position indicator). It can also be equipped with auxiliary contacts, trip coils, emergency tripping mechanisms, capacitive live display devices, key locks, and electric operating devices. In addition, this space can also be used for the installation of control circuits, recording instruments, and protection relays, realizing the monitoring, control, and protection of the operating status of the ring main unit.
Prodcuct Description
X G N 15 - 12 / 630 - X
1 2 3 4 5 6 7
| 7. I:FLN36-12 Load switches II:FLN48-12 Load switches |
Main technical parameters
| Item |
Unit |
Argument |
| Rated Voltage |
kV |
12,24,33 |
| Rated Frequency |
Hz |
50 |
| Rated Current of main bus/Maximum rated current of fuse |
A |
630,125 |
| Rated short time withstand current of main circuit and ground circuit |
kA/S |
203 |
| Rated peak withstand current of main loop and ground loop |
kA |
50 |
| Rated short-circuit closing, current of main circuit and ground circuit |
kA |
50 |
| Number of full capacity breaks of load switch |
time |
100 |
| Fuse breaking current |
kA |
31.5,40 |
| Rated closed-oop breaking current |
A |
630 |
| Rated transfer current |
A |
1600 |
| Mechanical life |
time |
2000 |
| 1 min power frequency withstand voltage (peak) Relative, ground/isolated fracture |
kV |
42,48 |
| Lightning impulse withstand voltage (peak) phase to phase, ground/isolation fracture |
kV |
75,85 |
| Secondary circuit lmin power frequency voltage |
kV |
2 |
| Protection level |
|
IP3X,
Customized |
Normal Service Condition
Temperature range: -25°C to +40°C
Altitude: below 2000m (high-altitude products can be customized)
Humidity: not exceeding 90% (at 20°C), and not exceeding 50% at the highest temperature of +40°C.
Installation should be in a location free of severe vibrations, and the surrounding air should not be contaminated with corrosive gases, flammable gases, or significant amounts of water vapor.
Main Product
We were established on April 9, 2002, located in Yuanjiatai Industrial Park, Xin 'andu Street, Dongxihu District, Wuhan City. We are an electrical manufacturing enterprise integrating manufacturing, production and trade. The company specializes in the research and development, manufacturing and service of high and low voltage switchgear, capacitance compensation equipment, box-type substation, outdoor ring cage, dense busbar trough and other products. In 2003, we are certified to ISO9001, ISO45001 and SO14001. In 2021, we were approved as the Hubei Province High-tech Enterprise. Between 2002 and 2003 we obtained the Wuhan City "contract and credit" enterprise, with a total of 12 new patented technologies, the main products obtained the national compulsory product 3C certifcation and type test report. In recent years, the company's products have been widely used in power, real estate chemical and other industries, and have been unanimously recognized by users. The company always adhere to the "quality of truth", "striving to perfection" attitude to serve the user, with its core value "integrity, win-win" we gain deep insights into our customers' business requirements. We continuously develop high-quality products and create benchmark projects to consistently deliver greater power to the world!
Are you a factory or a trading company?
We are a professional factory engaged in the manufacture of complete sets of equipment for the power industry. We are also one of the high-quality suppliers of the State Grid Corporation of China.
Can you provide customized product services?
Our professional technical team will design products according to your drawing requirements and actual conditions. We can also provide OEM/ODM services.
How long is your production lead time?
It depends on the product requirements and quantity. Generally it takes 5-10 days.
How to confirm payment?
We accept wire transfer, Paypal and other payment methods. Our payment terms are 30% T/T advance payment and 70% final payment.
How is your after-sales service?
We will provide installation instructions and have a professional production and installation team to provide online installation guidance. If any problem occurs, please provide on-site photos and instrument information. We will respond as quickly as possible and provide a suitable solution within 1 day.
Audited Supplier 
){kind=link}