Switchgear for BESS: Types, Design & Selection Guide

Battery energy storage systems (BESS) are becoming an important part of modern power systems. They can store electrical energy and later discharge it to support renewable generation, peak demand management, grid services, and other applications.

Switchgear for BESS provides switching, protection, isolation, and control within the electrical system connecting batteries, power conversion systems, transformers, collection networks, and the grid.

Depending on the BESS architecture, switchgear may include medium-voltage switchgear, vacuum circuit breakers, disconnectors, earthing switches, ring main units (RMUs), protection relays, and monitoring or automation equipment.

The correct configuration depends on the BESS voltage levels, power rating, fault levels, system architecture, grid requirements, installation environment, and applicable standards.

What Is Switchgear for BESS?

Switchgear for BESS is electrical equipment used to switch, protect, isolate, and control circuits associated with a battery energy storage system.

A BESS contains several electrical stages. A simplified system can be represented as:

Battery → DC system → Power Conversion System → Transformer → MV Switchgear → Grid

The actual architecture varies between projects. Some systems combine battery containers, PCS equipment, transformers, and MV switchgear into modular power blocks, while larger installations may use multiple feeders connected to a central substation.

BESS switchgear can perform several functions:

• Disconnect electrical equipment
• Interrupt fault currents
• Protect transformers and feeders
• Isolate equipment for maintenance
• Control MV collection circuits
• Connect or disconnect the BESS from the grid
• Provide status and measurement information
• Support protection and automation systems

Switchgear should therefore be designed as part of the complete BESS electrical system.

Why BESS Projects Need Switchgear

Battery storage systems introduce electrical operating conditions that require coordinated protection and switching.

Unlike a conventional one-way generation source, a BESS can generally operate in both charging and discharging modes.

During charging, electrical energy flows toward the battery system. During discharge, energy flows from the battery system toward the grid or connected load.

A simplified operating sequence is:

1. The battery stores electrical energy.
2. The PCS converts electrical power between the battery’s DC system and the AC network.
3. A transformer may increase the AC voltage.
4. MV switchgear controls the connection to the collection system or grid.
5. Protection equipment monitors electrical conditions.
6. Circuit breakers or other switching devices operate when required.

The switchgear must therefore be coordinated with the PCS, transformer, protection system, and grid connection equipment.

How Switchgear Fits Into a BESS

The position of switchgear depends on the BESS design.

A typical utility-scale arrangement may include multiple battery and PCS units connected to step-up transformers. Several MV feeders can then connect these units to a collector bus or substation.

A simplified architecture is:

Battery Containers
↓
DC Protection and Isolation
↓
PCS / Inverter
↓
Step-Up Transformer
↓
MV Switchgear
↓
MV Collection Network
↓
Substation / Grid Connection

This arrangement is only a simplified example. Actual projects can use different voltage levels, transformer configurations, feeder arrangements, and protection schemes.

For this reason, switchgear specifications should be developed from the project’s single-line diagram rather than from the BESS nameplate alone.

Main Types of Switchgear for BESS

Different BESS installations can require different switchgear technologies.

The appropriate option depends on the electrical design, voltage level, fault current, installation conditions, and project requirements.

MV Switchgear for BESS

Medium-voltage switchgear is commonly relevant to utility-scale BESS projects.

After the PCS converts battery power into AC power, a transformer may increase the voltage for connection to an MV collection network.

MV switchgear can then control and protect the transformer and feeder.

Important specifications may include:

• Rated voltage
• Rated current
• Short-circuit breaking capacity
• Short-time withstand current
• Peak withstand current
• Insulation level
• Switching duty
• Protection functions
• Busbar configuration
• Cable connection arrangement
• Environmental conditions

The required ratings should be determined from the project’s electrical studies and grid requirements.

Vacuum Circuit Breakers for BESS

Vacuum circuit breakers (VCBs) are an important option for medium-voltage BESS applications.

A VCB uses a vacuum interrupter to interrupt the electrical arc during circuit interruption. It can be integrated with protection relays and control systems for MV feeders and transformer circuits.

Potential benefits include:

• Vacuum interruption technology
• Compatibility with modern MV protection systems
• Suitable switching capability for many MV applications
• Integration with remote control and automation
• No SF6 required inside the vacuum interrupter for arc interruption

VCBs are not automatically appropriate for every BESS application. Their voltage, current, short-circuit, operating-duty, mechanical, and environmental specifications need to match the project.

For more information about VCB designation and configuration, see:

https://chinadegatech.com/vcb-model-letters-understand-vacuum-circuit-breaker-designations/

RMU and Compact Switchgear for BESS

Ring main units can be considered for BESS installations where a compact MV switching arrangement is appropriate.

An RMU can combine several MV functions into a relatively compact assembly. This can be useful for distributed BESS installations or projects where space is constrained.

However, an RMU should not be selected simply because it is compact.

Engineers should check:

• Number of incoming and outgoing circuits
• Transformer protection requirements
• Fault rating
• Cable configuration
• Earthing arrangement
• Expansion requirements
• Protection functions
• Automation requirements
• Maintenance access

For larger BESS substations, conventional MV switchgear may provide a more flexible configuration when multiple feeders, bus sections, or advanced protection functions are required.

Protection and Control for BESS Switchgear

Protection is one of the most important aspects of BESS switchgear design.

The protection system must be coordinated across the electrical equipment. Depending on the architecture, this can include protection for:

• MV feeders
• Transformers
• Busbars
• PCS equipment
• Cables
• Grid connection circuits

Protection relays may monitor electrical parameters such as current and voltage and initiate circuit-breaker operation when defined fault conditions occur.

Potential protection functions vary by system and may include overcurrent, earth-fault, under/overvoltage, frequency-related functions, and transformer-specific protection.

The exact protection philosophy must be established through an engineering study and coordinated with the utility or grid operator.

BESS Switchgear and PCS Integration

The power conversion system (PCS) is a central component of an AC-connected BESS.

The PCS controls the conversion between battery-side DC power and AC power. Switchgear operates on the electrical network side and provides switching and protection functions.

Successful integration requires attention to:

• AC voltage
• Rated current
• Fault contribution
• Breaker operating time
• Protection settings
• Control signals
• Interlocking
• Emergency shutdown arrangements
• Communication
• Transformer characteristics

Protection engineers should evaluate the complete system because inverter-based equipment can behave differently from traditional synchronous generation during electrical disturbances.

Switchgear for BESS Grid Connection

Grid-connected BESS projects require careful consideration of the point of interconnection.

At the grid interface, switchgear may be used for:

• Transformer protection
• Feeder protection
• Grid isolation
• Measurement
• Earthing
• Circuit interruption
• Remote operation

The utility may specify particular requirements for voltage class, protection functions, metering, communication, switching sequences, and interlocking.

Therefore, the BESS developer or EPC contractor should obtain the applicable grid-connection requirements before finalizing switchgear specifications.

SF6-Free Switchgear for BESS

Environmental considerations can influence BESS switchgear selection.

SF6 is a potent greenhouse gas, and regulations concerning its use in electrical equipment are developing in different markets.

As a result, some BESS developers may consider SF6-free switchgear.

Potential approaches include equipment using vacuum interruption combined with air insulation or other insulation technologies, depending on the product.

An important point is that vacuum interruption does not by itself describe the entire insulation system. Engineers should evaluate the complete switchgear design and its environmental characteristics.

When comparing SF6-free equipment, consider:

• Electrical ratings
• Insulation technology
• Switching technology
• Applicable standards
• Environmental conditions
• Maintenance requirements
• Lifecycle considerations
• Local regulatory requirements

For renewable and energy-storage projects with sustainability objectives, this evaluation can be included in the overall equipment-selection process.

Key BESS Switchgear Selection Factors

Selecting switchgear for BESS requires more than matching the nominal voltage.

1. System Voltage

Determine the AC voltage at the switchgear installation point.

Common MV classes can include 12 kV, 24 kV, and 36 kV, but the appropriate rating depends on the project’s electrical system.

2. Continuous Current

The switchgear must carry the expected continuous current under the relevant operating conditions.

The design should account for charging and discharging operation where applicable.

3. Fault Current

The prospective short-circuit current must be established through an appropriate electrical study.

The selected circuit breaker and switchgear assembly need suitable interruption and withstand ratings.

4. BESS Operating Modes

Because a BESS can charge and discharge, engineers should evaluate protection behavior in both directions of power flow where relevant.

5. Transformer Characteristics

Transformer impedance, rated power, connection arrangement, and protection requirements can influence switchgear selection and fault calculations.

6. PCS Characteristics

The PCS can affect fault behavior and protection coordination.

Engineers should use the manufacturer’s technical information when performing protection and system studies.

7. Installation Conditions

Consider:

• Indoor or outdoor installation
• Ambient temperature
• Humidity
• Dust
• Altitude
• Corrosive environments
• Available installation space
• Accessibility

8. Automation

Determine whether the project requires:

• Remote breaker control
• SCADA
• Condition monitoring
• Digital protection
• Communication interfaces
• Automated switching

9. Maintenance Strategy

Review access requirements, inspection procedures, spare parts, service support, and expected maintenance activities.

Low-maintenance equipment can reduce certain service requirements, but it should not be interpreted as requiring no inspection or testing.

10. Standards and Grid Requirements

The applicable equipment standards should be determined according to the equipment type and jurisdiction.

Relevant parts of the IEC 62271 series may apply to medium-voltage switchgear and controlgear, while additional requirements can come from national standards, grid codes, and project specifications.

IEC provides standards information at:

https://chinadegatech.com/switchgear-products/https://www.iec.ch/

Common BESS Switchgear Design Considerations

Fault Coordination

BESS protection needs to be coordinated with the PCS, transformer, feeders, and grid.

Incorrect coordination can result in unnecessary trips or inadequate fault isolation.

Bidirectional Power Flow

A BESS can operate in both charging and discharging modes. Protection and measurement arrangements should account for the actual operating philosophy.

Thermal Performance

Switchgear must be suitable for the expected continuous current and environmental conditions.

Enclosure temperature and ventilation requirements should also be considered where applicable.

Emergency Isolation

The complete BESS safety architecture should define how electrical equipment is isolated during abnormal or emergency conditions.

Switchgear is only one component of the overall safety system.

Communication and Cybersecurity

Digitally connected switchgear may exchange information with SCADA and other control systems.

Communication architecture and cybersecurity should therefore be considered during system design.

Future Expansion

If the BESS may be expanded, engineers can evaluate whether spare feeders, busbar capacity, physical space, or other provisions should be included from the beginning.

How to Choose a BESS Switchgear Supplier

For a BESS project, the supplier should be evaluated against the project’s technical requirements rather than price alone.

Consider asking suppliers for information covering:

• Rated voltage and current
• Short-circuit ratings
• Switchgear configuration
• Circuit-breaker technology
• Protection relay compatibility
• Dimensions and installation requirements
• Control and communication interfaces
• Applicable standards
• Testing and documentation
• Environmental limitations
• Maintenance requirements
• Spare parts
• Delivery schedule
• Engineering support
• Customization options

For EPC projects, it is also useful to confirm that the supplier can work from the project’s single-line diagram and technical specification.

A technically compliant switchgear solution should be evaluated together with the BESS integrator, transformer supplier, protection engineer, and grid-connection team where appropriate.

FAQs About Switchgear for BESS

What is switchgear for BESS?

Switchgear for BESS is electrical equipment used to switch, protect, isolate, and control circuits connecting battery energy storage systems with PCS equipment, transformers, MV collection systems, and the grid.

What type of switchgear is used in BESS?

BESS projects can use MV switchgear, vacuum circuit breaker switchgear, RMUs, compact switchgear, outdoor switchgear, and smart switchgear. The choice depends on the system architecture and electrical ratings.

Does a BESS need MV switchgear?

A utility-scale BESS connected through a medium-voltage network will generally require suitable MV switching and protection equipment. The exact arrangement depends on the project’s electrical architecture and point of interconnection.

Why are vacuum circuit breakers used in BESS?

Vacuum circuit breakers can provide medium-voltage switching and fault interruption. They can also be integrated with modern protection, control, and automation systems.

What is the difference between BESS switchgear and solar switchgear?

Both can use similar MV technologies, but BESS introduces specific considerations related to bidirectional power flow, PCS behavior, charging and discharging modes, and the characteristics of the storage system.

Where is switchgear installed in a BESS?

Switchgear can be installed between the PCS and transformer, on MV collection feeders, within a BESS substation, or at the grid interconnection point, depending on the system design.

Can RMUs be used for BESS?

Yes, an RMU can be suitable for certain BESS applications where its voltage, current, fault, protection, and configuration requirements match the project.

Is SF6-free switchgear suitable for BESS?

SF6-free switchgear can be considered for BESS where the selected technology meets the project’s electrical, environmental, regulatory, and operational requirements.

How do I size switchgear for a BESS?

Start with the system voltage, continuous current, maximum fault current, PCS and transformer characteristics, protection requirements, operating modes, installation environment, and grid requirements. The final ratings should be confirmed through appropriate engineering studies.

Does BESS switchgear need protection relays?

Many MV BESS applications use protection relays, but the required functions depend on the electrical architecture and protection philosophy.

Can BESS switchgear be automated?

Yes. BESS switchgear can be integrated with monitoring, SCADA, remote control, digital protection, and other automation systems when required by the project.

What standards apply to BESS switchgear?

The applicable standards depend on the equipment and jurisdiction. Relevant parts of the IEC 62271 series may apply to MV switchgear and controlgear, alongside applicable national standards, grid codes, and project specifications.

What should I ask a BESS switchgear manufacturer?

Ask about electrical ratings, fault capability, circuit-breaker technology, protection integration, communication, environmental limits, dimensions, testing and documentation, standards compliance, maintenance, customization, delivery, and technical support.

Conclusion

Switchgear for BESS is a key part of the electrical infrastructure that connects battery storage systems to transformers, MV collection networks, substations, and the grid.

The correct solution depends on much more than the BESS’s energy-storage capacity. Voltage, current, fault level, PCS characteristics, transformer configuration, bidirectional operation, protection philosophy, environmental conditions, automation, and grid requirements all influence the selection.

MV switchgear, vacuum circuit breakers, RMUs, compact designs, smart switchgear, and SF6-free technologies can each serve particular BESS applications.

For developers, EPC contractors, utilities, and BESS integrators, the most reliable approach is to begin with the complete single-line diagram and electrical studies, then select switchgear that satisfies the project’s technical specifications and applicable standards.