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What is Ring Main Unit 

 

Ring Main Units (RMUs) are compact medium-voltage switchgear assemblies designed for controlling, protecting and isolating electrical circuits in distribution networks. They are widely used in industrial plants, commercial buildings, residential areas, substations, infrastructure projects and renewable energy systems.

 

Kechang Electric provides RMUs with different configurations according to project requirements. Depending on the application, the unit can be equipped with load break switches, vacuum circuit breakers, fuses, earthing switches, protection relays and other components to provide reliable control and protection for medium-voltage distribution systems.

Core Advantages of Our Ring Main Unit

Compact & Space-Saving

RMUs combine switching, protection and isolation functions in a compact enclosure, making them suitable for substations and distribution systems where installation space is limited.

 

Reliable Power Distribution

RMUs support reliable control, isolation and protection of medium-voltage distribution circuits, helping improve power supply continuity in industrial, commercial and infrastructure applications.

 

Factory Tested Before Delivery

Each RMU undergoes routine inspection and electrical testing before shipment to verify key functions and performance according to applicable project and technical requirements.

 

 

 
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Ring Main Unit

 

A Ring Main Unit (RMU) is considered an important component in electrical power distribution networks, primarily used in medium voltage applications. This specialized type of switchgear is named for its typical integration into a ring-shaped network of connections, enhancing both redundancy and reliability. RMUs are particularly instrumental in ensuring that power distribution is not interrupted, even in the event of a component failure.

 

One of the outstanding features of RMUs is their compact and extensible design. They are often insulated by which significantly reduces the effects of dust, moisture and other environmental factors to improve safety standards. The unit comprises switches, fuses, and circuit breakers, each serving a crucial role in monitoring and controlling the flow of electricity, ensuring that energy is efficiently and safely distributed to various endpoints.

 

Product Specifications

 

Project

Unit

Circuit Breaker

Load Switch

Load Switch - Fuse Combinations

Rated Voltage

KV

12

12

12

Rated Frequency

A

630/1250

630

125

Rated Current

Hz

50

50

50

Rated Insulation Level

1 min Power Frequency Withstand Voltage (Interphase and Phase to Ground)

KV

12

42

42

1 min Power Frequency Withstand Voltage (Isolating Distance)

48

48

48

Rated Power-frequency Withstand Voltage (Control and Auxiliary Circuit)

2

2

2

Rated Lightning Impulse (between Phases, to Earth)

75

75

75

Rated Lightning Impulse (Across the Isolating Diatance)

85

85

85

Rated Filling Pressure (Gauge Pressure When Temperature is 20℃)

Mpa

0.02

Minimum Functional Pressure (Gauge Pressure When Temperature is 20℃)

Mpa

0

Pressure Relief Device Release Pressure (Gauge Pressure When Temperature is 20℃)

Mpa

0.16

Yearly Gas Leakage Rate

-

≤0.01%

Mechanical Life

Times

10000

Main Loop Resistance

μΩ

≤150

 

The Many Advantages of Ring Main Unit

Ring network cabinets (RMUs) are popular because of the many advantages they bring to the industrial and utility sectors.This article will explore some of the significant advantages：

 

Cost savings: The ring network cabinet is known for its efficient and fast operation.They are easy to install, thereby reducing labor and installation costs. The efficient design and operation of the equipment can also reduce downtime and ensure the continuous operation of the system, thereby saving time and money.

 

Compact and fully functional: The compact design of the ring network cabinet does not affect its function.They are equipped with many performance-enhancing features.This space-saving design makes it ideal for urban areas and industrial applications where space is precious.

 

Strong adaptability: The ring network cabinet can be customized according to the specific needs of different applications to ensure that each unique requirement is effectively and efficiently met.

 

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Enhanced Safety & Protection

Safety is essential in any electrical installation.  The ring network cabinet is equipped with safety functions to ensure the safety of equipment and personnel. The reliable performance of the ring network cabinet under various working conditions fully proves its rugged design and structure.

Low maintenance cost

With its durable and reliable design, the ring network cabinet has extremely low maintenance requirements. This not only reduces operating costs, but also minimizes the risk of unexpected failures and ensures long-term stable performance.

Long service life

One of the most prominent features of the ring network cabinet is its long service life. These equipment are manufactured with high-quality materials and advanced technology, and have a design service life of more than 20 years, providing a long-term solution for power distribution needs.

 

Structure and Insulation Classification of the Ring Main Unit

 

Internal Components

Input and output cable compartments: Connect to the transformer.
Switchgear: Some are installed in SF6 gas tanks with good environmental tolerance.
Customizable compartments: Can be configured with different numbers of compartments according to needs.

Insulation Classification

Air-insulated cabinet: Suitable for environments with low humidity and dust.
Vacuum-insulated cabinet: It has good insulation performance in a vacuum environment.
SF6 gas-insulated cabinet: It has strong resistance to environmental factors, but SF6 is a greenhouse gas, and its use requires strict handling and recycling.
Environmentally friendly gas-insulated cabinet: It meets environmental requirements and is filled with environmentally friendly gas.

Indoor Ring Main Unit

 

Common Voltage Levels of the Ring Main Unit

 

10kV

Commonly used in distribution stations of urban residential communities and general factory enterprises.

01

12kV

Widely used in medium voltage distribution systems, such as distribution rooms of small factories and commercial buildings.

02

24kV

Used in industrial areas and large commercial complexes with high requirements for power supply capacity and reliability.

03

35kV

Suitable for high-voltage distribution scenarios such as large industrial and mining enterprises and substations.

04

40.5kV

Used in industrial production or large power transmission hubs with high voltage requirements.

05

 

Core Technical Parameters and Selection Criteria
 

Rated Voltage: The maximum voltage at which the RMU can operate safely, such as 12kV, 24kV, or 36kV. This must match the grid’s voltage.

 

Rated Current: Typically 630A, this is the maximum current the unit can carry continuously under normal operating conditions.

 

Rated Short-time Withstand Current: This is a key measure of the RMU’s stability during a fault. For example, a rating of 20kA/3s means the unit can handle a short-circuit current of up to 20,000 amps for three seconds without being damaged.

 

IP Rating (Ingress Protection): This rating indicates how well the enclosure protects against solids and liquids. An IP4X rating for the enclosure means it can block solids larger than 1mm, while an IP67 rating for the gas compartment means it's fully dust-tight and can be temporarily submerged in water.

 

Internal Arc Classification (IAC): This is a critical safety rating that measures how well the unit protects operators from the effects of an internal arc flash fault. An IAC-rated design effectively contains the heat and pressure of an arc, preventing explosive gases or flames from escaping the enclosure.

 

Selection Comparison Chart

 

Feature

Air-Insulated RMU

SF6 Gas-Insulated RMU

Solid-Insulated RMU

Size

Larger

Compact

Very Compact

Environmental Impact

Excellent (no greenhouse gas)

Poor (SF6 is a greenhouse gas)

Excellent (no gas emissions)

Maintenance

Requires regular inspection

Nearly maintenance-free

Maintenance-free

Cost

Lower

Moderate

Higher

Technology Maturity

Very mature

Very mature

Maturing

 

Certificates

 

productcate-1-1
productcate-1-1
productcate-595-836
productcate-595-836

 

FAQ

 

Q: What are your payment terms?

A: We accept multiple payment methods. The standard term is 30% T/T as a deposit, and 70% balance before shipment. Western Union and Letter of Credit (L/C) are also acceptable for your convenience.

Q: How does your factory perform in terms of quality control?

A: All products undergo a 100% inspection before shipment to ensure they meet strict quality standards.

Q: When can I get the quotation?

A: Usually,we will provide the quotation within 24 hours after receiving your inquiry.

Q: How could I get a sample?

A: We can ship samples to you.You will be responsible for the samples price plus all related shipping costs, where the express delivery charge varies depending on the quantity of the samples.

Q: What is the price of shipping?

A: Depending upon the port of delivery, prices vary

As one of the leading ring main unit manufacturers and suppliers in China, we warmly welcome you to wholesale cheap ring main unit from our factory. All customized products are with high quality and competitive price.

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