Ring Main Unit: The Core Power Distribution Node for Urban Distribution Network and New Energy Projects

With the large-scale popularization of urban power grid renovation, distributed photovoltaics, energy storage and charging piles, the structure of distribution networks has become increasingly complex. The ring power supply mode features high power supply reliability and small fault impact range, thus becoming the mainstream networking scheme for urban & town power distribution, industrial parks and new energy stations. The ring main unit is the indispensable core switchgear in ring network structures.

A ring main unit is a metal-enclosed complete switchgear, mainly applied to 10kV medium-voltage power distribution networks. It undertakes functions of power distribution, line switching and fault isolation, enabling interconnection of multiple lines in a ring layout. When a fault occurs on a section of line, it can quickly cut off the faulty segment to guarantee continuous power supply in non-fault areas, effectively shortening power outage duration and improving grid resilience.

I. Core Functional Value of Ring Main Units

1. Build ring power supply structures: to realize interconnection of multiple distribution lines, breaking the traditional single radial power supply mode and providing backup power supply channels.

2. Rapid fault isolation: Cooperate with secondary intelligent devices to quickly break circuits in case of short-circuit and grounding faults, prevent accident spread and lay the foundation for self-healing distribution networks.

3. Rational power allocation: As branch power distribution nodes, distribute electric energy to commercial zones, residential communities, factories and photovoltaic step-up units.

4. Safe isolation for equipment maintenance: Form visible breaking points through disconnectors to create safe operating conditions for line maintenance and protect the personal safety of maintenance staff.

II. Main Technical Classification of Ring Main Units

1. Air-Insulated Ring Main Unit (AIS)

It adopts atmospheric air as insulation medium, with an intuitive structure and convenient maintenance, at a moderate procurement cost.

Advantages: Low maintenance threshold and highly versatile spare parts

Disadvantages: Large cabinet size, susceptible to external environments such as humidity and dust.

Applicable scenarios: Indoor power distribution rooms with favorable environmental conditions.

2. Gas-Insulated Ring Main Unit (GIS Gas Cabinet)

It adopts a sealed gas tank structure and uses insulating gas as the main insulation and arc-extinguishing medium, serving as the mainstream product in the current market.

Advantages: Compact size, small floor area, strong resistance to external dust and condensation, high protection grade

Applicable scenarios: Outdoor switching stations, underground pipe galleries, narrow power distribution spaces, photovoltaic projects and renovation of old urban power grids.

3. Solid-Insulated Ring Main Unit (SIS)

Its primary conductive components are integrally cast and encapsulated with epoxy resin without gas filling, featuring prominent environmental protection performance.

Advantages: No risk of gas leakage, strong environmental adaptability and excellent maintenance-free performance

Disadvantages: High processing technology requirements and difficult replacement of internal components.

Applicable scenarios: Parks and key projects with strict environmental protection and explosion-proof requirements.

III. Intelligent Upgrade: Primary-Secondary Integrated Complete Ring Main Unit Solutions

Traditional ring main units only realize primary switching functions and cannot adapt to new-type power systems. At present, the industry widely promotes primary-secondary integrated complete solutions: embed current & voltage sensors, partial discharge monitoring and temperature sensing units inside ring main units, matched with external intelligent power distribution terminals. The complete system can realize the following functions:

● Real-time remote upload of operating data
● Automatic fault location, reporting and segment isolation
● Remote closing and opening control
● Early warning of joint overheating and internal insulation defects

Note: Intelligent power distribution terminals are purchased auxiliary components. Deyan Electric is responsible for cabinet structural design, wiring, integrated assembly and overall commissioning for delivery. Primary-secondary integrated ring main units act as important carriers for the implementation of distribution automation, widely matched with new energy box substations and smart urban power distribution networks.

IV. Key Factors to Be Considered in Ring Main Unit Selection

1. Operating environment: Indoor/outdoor, humidity, corrosion risk, space size

2. Power supply scheme: Simple radial power supply or dual-power ring power supply

3. Insulation form: Selection among air insulation, gas insulation and solid insulation

4. Functional demands: Basic type or intelligent supporting with primary-secondary integration

5. Load scale, short-circuit breaking current, protection grade and other electrical parameters

Reasonable model selection can balance initial investment and long-term operation & maintenance costs, ensuring stable operation of equipment for more than ten years.

Brief Introduction to Zhejiang Deyan Electric

Zhejiang Deyan Electric Co., Ltd. focuses on medium and low voltage complete power distribution equipment and integrated power distribution solutions. The company independently produces primary switchgears including air-insulated ring main units, gas-insulated switchgears and complete outdoor switching stations. According to project demands, it can provide primary-secondary integrated complete solutions integrated with intelligent monitoring components, intelligent power distribution terminals, box-type substations, high and low voltage switch cabinets and prefabricated cabin complete systems.

Its products are widely applied to urban power grid upgrading, industrial & commercial park power distribution, distributed photovoltaic power stations, energy storage projects, rail transit, municipal infrastructure and other scenarios. The company supports customized primary schemes, integrated assembly and overall factory commissioning, with a professional technical team providing preliminary scheme design and parameter selection technical support.

If you have demands for procurement and scheme consultation of ring main units and complete power distribution equipment, please contact Deyan Electric. We keep providing safe, reliable and cost-effective complete power distribution solutions for various power engineering projects.