22kV Vacuum Circuit Breaker with Load Break Switch

Ring main units (RMUs) are a widely used solution for power distribution networks, particularly in urban areas where space is limited. These units provide a compact, robust, and reliable switchgear solution. The 22kV Vacuum Circuit Breaker with Load Break Switch is an essential component of eco-friendly ring main units and medium-voltage switchgear. It is specifically designed for safely energizing and de-energizing circuits under normal load conditions.

Technological Advancements in RMU Design

The development of ring main unit technology is closely synchronized with advancements in load circuit breaker design. Modern RMUs are typically equipped with vacuum load break switches or sulfur hexafluoride gas-insulated switches housed in sealed stainless steel tanks. This configuration ensures that the equipment operates normally without the need for maintenance throughout its service life.

Reliability and Fault Isolation

One of the key advantages of RMUs is the ability for network operators to partition the distribution system, isolate fault areas, and perform equipment maintenance without disrupting the power supply to unaffected customers. This functionality is critical in meeting the high reliability standards expected by contemporary power networks.

Enhanced Safety and Compact Design

Load break switches used in RMUs offer distinct advantages over other switching devices. They can interrupt normal load currents while providing visible isolation and integral earthing through an innovative three-position switch configuration. This combination of functions within a single device contributes significantly to the RMU's compact footprint, making them ideal for space-constrained installations. Applications include prefabricated substations, wind tower installations, and urban distribution centers..

Model and meanings

Working Principle of the Load Break Switch

The main function of a 22kV Vacuum Circuit Breaker with Load Break Switch is managing the electric arc that forms when contacts separate while current flows. When the load break switch opens under load, the current continues momentarily through ionized air between the separating contacts, and it will create an arc with temperatures reaching several thousand degrees . It is very important for the effective arc extinction within milliseconds to prevent contact erosion, insulation damage, and potential equipment failure.

Modern load break switches for the RMU achieve arc extinction through two primary technologies: SF6 gas and vacuum interruption.

In SF6-insulated ring main unit or switchgear, These contact components operate in sealed containers containing sulfur hexafluoride gas and pressure controlled. This gas arc-quenching properties is exceptional, due to the SF6 gas has electronegative nature which readily captures free electrons, rapidly de-ionizing the arc path and restoring dielectric strength. When the contacts of the load break switch separate, the arc forms within the SF6 atmosphere, and the gas's thermal conductivity and chemical properties combine to cool and extinguish the arc within milliseconds .

The three-position mechanism represents a significant innovation in switch design. A single moving contact assembly travels vertically or rotationally to achieve the three required positions . In the closed position, the moving contact bridges the busbar and cable connections. Moving to the open position withdraws the contact to a neutral position where both circuits are isolated. Further movement engages the earthing contact, connecting the cable to ground while maintaining isolation from the busbar .

Mechanical interlocks prevent incorrect operation, such as attempting to close the earthing switch while the main switch remains closed or operating the switch into a fault condition . These interlocks are typically mechanical and cannot be overridden without destroying the interlock mechanism, ensuring absolute safety in normal operation.

The Main Purpose of loadbreak switch

A very important function of load break switches within ring main units is ensure safe and controlled management of power distribution networks under normal operating conditions. Several specific objectives guide this application:

Network Sectionalization – Load break switches allow operators to divide distribution networks into manageable sections, isolating specific portions for maintenance or fault location without de-energizing the entire system . This capability underpins the high availability expected of modern ring-main configured networks.

Load Current Interruption – The switch must reliably interrupt all currents within its design rating, from minimal transformer magnetizing currents up to full rated load current . This operational capability can ensures safely and systematically for planned downtime for maintenance or network reconfiguration.

Visible Isolation – When the load break switch opened, it will provide a visible break between live conductors and the isolated section . This visual confirmation of isolation is very important for safety when we maintenance and is often provided mechanical position indicators and observation windows .

Integrated Earthing – The three-position design ensures that outgoing circuits can be positively earthed before personnel access cables or connected equipment . This function can replace the need for external grounding devices and ensure that grounding operations are only carried out after appropriate isolation is completed.

Transformer Protection Coordination – In the combinaition of load break switch and fuse, the load break switch works in coordination with medium-voltage fuses to provide transformer protection . When a fuse operates, a striker pin releases and trips the switch mechanism, opening all three phases and preventing single-phasing .

Application Range of Load Break Switch

The 22kV Vacuum Circuit Breaker with Load Break Switch in rural power grids are suitable for a wide range of voltage levels from 6 kV to 40.5 kV.

Utility Distribution Networks – RMUs are usually used in power distribution systems of urban areas. These medium-voltage switchgears or RMUs connect primary power substations to power distribution transformers, which servers residential, commercial, and mixed-use developments .

Industrial Facilities – The RMUs are usually mounted in manufacturing plants, processing facilities, and industrial complexes for medium voltage power distribution. The features of the load break switch has compact size is very important for at a premium, and the maintenance-free operation minimizes production interruptions .

Commercial Buildings – The RMUs are also used in the large commercial developments, shopping centers, and office complexes. which can be easy to distribute power reliably throughout the facility . The ability to isolate sections for maintenance without affecting tenanted areas provides operational flexibility.

Renewable Energy Applications – The ring main units are emplyed in the solar photovoltaic installations, wind farms, and battery energy storage systems for grid connection and internal distribution increasingly . These medium-voltage swtiches have these features including coastal corrosion resistance, dust protection, and compact dimensions for wind tower installation .

Prefabricated Substations – Compact substations for urban and industrial applications integrate RMUs as the high-voltage switching and protection section, typically mounted alongside distribution transformers within a common enclosure . This arrangement minimizes on-site installation work and provides a weatherproof, secure power supply point.

Technical Parameters of Load Break Switch

Appearance and Dimension

FAQ

What is the difference between a load break switch and a circuit breaker in an RMU?

A load break switch is designed to interrupt normal load currents during routine switching operations, while a circuit breaker can interrupt much higher fault currents during short-circuit conditions . In RMU configurations, load break switches handle everyday switching, and separate fuses or circuit breakers provide fault protection .

How does the three-position switch work?

The three-position switch uses a single moving contact that travels between three positions: closed (connecting busbar to cable), open (isolating both), and earthed (connecting cable to ground while maintaining busbar isolation) . This integrated design ensures proper sequencing and visible isolation.

Can a load break switch interrupt fault current?

No, load break switches are not designed for fault current interruption . In switch-fuse combinations, the fuses interrupt fault current, and the switch opens only after the fuse operates. For higher fault levels, circuit breakers with protective relays are required .

What maintenance do load break switches require?

Modern SF6-insulated load break switches in sealed RMU tanks are designed maintenance-free for life .All the internal components are sealed in a tank to be protected from contamination, and SF6 gas is no need to replenishment throughout normal service life.All the internal components are sealed in a tank to be protected from contamination, and SF6 gas is no need to replenishment throughout normal service life. External mechanisms may need regularly inspection and lubrication based on manufacturer operation manual.

How can I get the states that the switch is open or closed?

Load break switches provide multiple indications of position: mechanical indicators on the operating mechanism show the current state, mimic diagrams represent the actual circuit configuration, and many RMUs include observation windows for direct visual confirmation of contact position . Some equipments incorporate auxiliary switches for remote indication.

What voltage ranges are available?

The rated voltage range of the load break switches usually is from 6 kV to 40.5 kV, generall the ratings of 11kV, 17.5 kV, 24 kV, and 33kV . Each voltage rating is for specific insulation levels and testing requirements.

Are the load break switches suitable for outdoor installation?

Yes, but need to configure with enclosures and power suppliers. Many RMUs for outdoor application incorporate weatherproof cabinets, corrosion-resistant materials, and sealed tanks that protect internal components from environmental exposure . which often are mounted in the prefabricated substation together with the transformers. Outdoor units must meet additional ingress protection and UV resistance requirements.

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