MV Switchgear for Battery Energy Storage Systems: Key Design Considerations for BESS Projects in Australia

Battery Energy Storage Systems are becoming an increasingly important part of Australia’s electrical infrastructure. Utility-scale batteries, renewable energy projects, mining microgrids, industrial facilities, and network-support projects all rely on BESS to store energy, manage power flows, and support more flexible electrical operation.

Behind every large BESS is a medium voltage electrical system that must connect battery inverters, transformers, auxiliary systems, and the wider grid safely and reliably.

This makes MV switchgear for BESS a critical engineering and procurement decision.

Selecting BESS switchgear is not simply a matter of matching the system voltage.

Project teams must consider bidirectional power flow, short-circuit levels, inverter behaviour, protection coordination, switching duty, harmonic performance, transformer integration, auxiliary power, environmental conditions, SCADA requirements, and long-term maintainability.

For Australian EPC contractors, renewable developers, utilities, mining operators, consultants, and asset owners, getting these requirements right during specification can reduce commissioning risk and improve the reliability of the complete BESS installation.

Where Does MV Switchgear Fit Into a BESS?

A utility or commercial-scale BESS typically includes several major electrical components:

• Battery racks or battery containers

• Battery Management System (BMS)

• Power Conversion System (PCS)

• LV switchboards

• Inverter or step-up transformers

• MV switchgear

• Protection and control systems

• SCADA and Energy Management System (EMS)

• Auxiliary power systems

• Grid connection transformer or substation equipment

The exact architecture varies by project.

In many systems, the PCS converts DC battery power to AC at low voltage. A step-up transformer then increases the voltage to the project’s medium voltage collector level. MV switchgear connects individual BESS blocks or transformer feeders to the collector bus and, ultimately, to the grid connection point.

Leistung Energie’s MV switchgear portfolio includes primary and secondary equipment up to 40 kV, which is relevant to typical medium-voltage renewable and BESS collector applications.

Because BESS can both import and export power, the switchgear and associated protection system must be designed as part of a bidirectional electrical network rather than as a conventional one-way load feeder.

1. Start With the Electrical Architecture

Before specifying the switchgear, define the complete BESS single-line diagram.

The project team should establish:

• BESS MW and MWh capacity

• Number of battery blocks

• PCS rating per block

• Transformer rating per block

• Nominal MV system voltage

• Number of transformer feeders

• Main busbar configuration

• Grid connection arrangement

• Auxiliary transformer configuration

• Earthing arrangement

• Future expansion requirements

Australian renewable projects commonly use MV collector voltage levels such as 11 kV, 22 kV, or 33 kV, depending on network connection requirements and project architecture.

The switchgear supplier should therefore receive more than a voltage level and panel quantity. A controlled single-line diagram, transformer data, cable information, protection philosophy, fault study data, and operating sequence provide a much better basis for equipment selection.

2. Select the Correct Voltage and Insulation Rating

The rated voltage of the switchgear must be coordinated with the nominal system voltage and the highest voltage expected under operating conditions.

The specification should define:

• Nominal system voltage

• Rated switchgear voltage

• Insulation withstand level

• Power frequency withstand voltage

• Lightning impulse withstand level

• System frequency

• Earthing method

• Indoor or outdoor installation

MV metal-enclosed switchgear falls within the scope of IEC 62271-200 for AC equipment above 1 kV and up to and including 52 kV, including indoor and outdoor installations.

The correct insulation rating should be confirmed against the project's insulation coordination study, network requirements, transformer data, surge protection philosophy, and site conditions.

3. Consider Bidirectional Power Flow

One characteristic that distinguishes BESS from a conventional load is bidirectional power flow.

During charging, power flows from the grid or renewable generation toward the battery. During discharge, power flows from the battery through the PCS and transformers back toward the MV network.

The switchgear busbar and primary conductors do not normally need different current ratings simply because power reverses direction. However, the overall system design must account for the maximum continuous current under both charging and discharging conditions.

The design should consider:

• Maximum BESS import power

• Maximum BESS export power

• Reactive power operating range

• Transformer rating

• PCS overload capability

• Simultaneous operation of multiple battery blocks

• Ambient-temperature derating

• Future expansion

Protection and metering require particular attention because directional behaviour may change depending on whether the plant is importing or exporting.

4. Calculate the Fault Level Before Selecting Switchgear

Short-circuit rating is one of the most important parameters in any MV switchgear for BESS specification.

The project fault study should determine the prospective fault current at every relevant MV bus.

Sources can include:

• Utility or transmission network contribution

• Upstream transformers

• Parallel transformers

• Synchronous generation, if present

• Other connected renewable generation

• BESS inverter contribution

• Motors and industrial loads where applicable

BESS introduces an additional engineering consideration because inverter-based resources do not necessarily produce fault current with the same characteristics as synchronous machines. AEMO has highlighted the changing protection challenges associated with inverter-based resources and the importance of fault-current characteristics for reliable protection operation.

The switchgear specification should define:

• Rated short-time withstand current

• Short-circuit duration

• Peak withstand current

• Circuit breaker breaking capacity

• Circuit breaker making capacity

• Earth-fault level

• Maximum future fault level where applicable

Do not select the switchgear fault rating solely from today's network conditions if planned network reinforcement or additional generation could increase fault levels during the asset life.

5. Protection Must Reflect BESS Operating Modes

Protection for BESS switchgear can be more complex than protection for a conventional radial feeder.

The protection philosophy may need to accommodate charging, discharging, standby operation, transformer energisation, grid disturbances, islanding scenarios, or grid-support functions depending on the project.

Typical protection functions may include:

• Phase overcurrent

• Earth fault

• Directional overcurrent

• Directional earth fault

• Transformer differential

• Restricted earth fault

• Under-voltage

• Over-voltage

• Under-frequency

• Over-frequency

• Breaker failure

• Trip circuit supervision

• Synch-check where required

• Arc protection

• Interlocking

• Anti-islanding functions where applicable

The final relay functions should come from the project protection study rather than from a generic switchgear schedule.

Coordination is required between the MV relay, PCS protection, transformer protection, BMS, EMS, upstream network protection, and grid connection requirements.

This is particularly important because existing power-system protection philosophies have historically been developed around fault characteristics produced by synchronous equipment, while inverter-based resources can respond differently during faults.

6. Understand the Actual Switching Duty

The term “battery charging and discharging cycles” can create confusion when switchgear is specified.

The MV circuit breaker does not necessarily open and close every time the battery changes between charging and discharging. Normal reversal of active power is typically controlled electronically by the PCS.

However, MV breakers may still perform important operational duties involving:

• BESS block energisation

• Transformer energisation

• Fault interruption

• Planned isolation

• Maintenance switching

• Emergency shutdown

• Grid connection or disconnection

• Testing and commissioning sequences

The breaker therefore needs to be evaluated for the actual number and type of switching operations expected throughout the asset life.

Transformer magnetising inrush, cable charging current, capacitive circuits, and any project-specific switching sequence should also be reviewed before final breaker selection.

7. Coordinate the Switchgear With the BESS Transformer

The transformer is one of the most important interfaces in a BESS electrical system.

Depending on the architecture, each PCS may connect to its own inverter transformer, several PCS units may share a transformer, or the collector system may feed a larger grid connection transformer.

The switchgear specification should coordinate with transformer parameters such as:

• Rated MVA

• Primary and secondary voltage

• Vector group

• Percentage impedance

• Tap range

• Inrush current

• Cooling method

• Transformer protection

• CT requirements

• Neutral arrangement

• Earthing method

Transformer impedance is especially important because it influences fault levels and voltage performance.

Leistung Energie’s power transformer range is designed for applications including power generation, electric utilities, mining, oil and gas, water and wastewater, with designs available up to 500 kV insulation rating and 500 MVA depending on application.

For a BESS project, transformer and switchgear procurement should therefore be coordinated rather than treated as two unrelated equipment packages.

8. Account for Harmonics and Power Quality

BESS power conversion systems use power electronics. As with other inverter-based equipment, harmonic performance must therefore be considered as part of the complete system design.

The switchgear itself is not a harmonic filter, but harmonic current can influence the surrounding electrical system.

Project teams should review:

• PCS harmonic spectrum

• Total harmonic current distortion

• Voltage distortion at relevant buses

• Transformer harmonic heating

• Cable loading

• Capacitor bank interaction

• Resonance conditions

• Protection and metering accuracy

• Grid connection harmonic limits

The analysis becomes particularly important where the site combines BESS with solar PV, VSDs, EV chargers, UPS systems, rectifiers, or other non-linear equipment.

Where harmonic mitigation is required, the solution should be selected from the actual harmonic study. Depending on voltage level and system architecture, this may involve inverter controls, transformer configuration, passive filtering, or active filtering at an appropriate point in the electrical system.

Leistung Energie also provides modular active harmonic filter solutions for LV applications, with filtering capability up to the 51st harmonic and support for automatic load balancing and compensation.

9. Do Not Overlook Auxiliary Power

A BESS cannot operate safely with only the main battery power conversion equipment.

A wide range of auxiliary loads may remain necessary whether the plant is charging, discharging, or in standby.

These can include:

• Battery container HVAC

• BMS equipment

• EMS controls

• PCS control power

• Fire detection systems

• Fire suppression systems

• Communications

• Network switches

• Protection relays

• Switchgear control circuits

• Battery chargers

• Lighting

• Security systems

• Monitoring equipment

The design should therefore determine how auxiliary power will be supplied during normal operation, shutdown, maintenance, and loss-of-grid conditions.

Depending on project criticality, this may require separate auxiliary transformers, DC systems, UPS supplies, redundant sources, or emergency backup.

MV switchgear specifications should identify auxiliary supply voltages and control power requirements early so that breaker mechanisms, protection relays, indication circuits, heaters, and communications are correctly configured.

10. Internal Arc Safety Remains Critical

BESS substations frequently use compact e-houses, prefabricated buildings, kiosks, or containerised electrical rooms.

Space efficiency is valuable, but compact layouts can make internal arc management more important.

The switchgear specification should consider:

• Internal Arc Classification

• Arc current

• Arc duration

• Front accessibility

• Lateral accessibility

• Rear accessibility

• Pressure-relief design

• Arc exhaust ducting

• Switchroom ceiling height

• Personnel access

• Cable compartment arrangement

IEC 62271-200 provides the framework for metal-enclosed MV switchgear, including internal arc classification provisions.

For BESS e-houses in particular, the switchgear and building should be considered as an integrated safety arrangement. Pressure relief cannot be evaluated only at panel level without considering where hot gases would be directed.

11. Design for Australian Environmental Conditions

Many Australian BESS projects are located in environments that can be demanding for electrical equipment.

Conditions may include:

• High ambient temperature

• Solar heat load

• Dust

• Humidity

• Salt contamination

• Coastal corrosion

• Remote locations

• Condensation

• Limited maintenance access

• High daily temperature variation

These conditions should be documented in the equipment specification.

Depending on the site, project teams may need to define:

• Enclosure protection level

• Corrosion protection

• Anti-condensation heaters

• HVAC requirements

• Maximum ambient temperature

• Minimum ambient temperature

• Altitude

• Ventilation

• Filtration

• Outdoor enclosure requirements

Leistung’s existing renewable MV switchgear guidance also emphasises the importance of defining temperature, dust, humidity, corrosion exposure, ventilation, and enclosure conditions rather than specifying electrical ratings alone.

12. Earthing and Neutral Management Need Early Attention

The BESS earthing arrangement affects protection behaviour, earth-fault current, transformer selection, and switchgear specification.

The design should clearly define whether the MV system is:

• Solidly earthed

• Resistance earthed

• Reactance earthed

• Transformer-neutral earthed

• Using a dedicated earthing transformer

• Operated under another project-specific arrangement

Protection CT selection and earth-fault relay settings must be coordinated with the chosen grounding philosophy.

This should not be left until switchgear manufacturing has started. Changes to earthing arrangements can affect transformer connections, protection functions, CT ratios, cable design, and panel construction.

13. SCADA and BESS Control Integration

Modern BESS projects are highly automated.

The MV switchgear is therefore part of a larger control ecosystem connecting:

• SCADA

• EMS

• BMS

• PCS

• Protection relays

• Revenue meters

• Power quality meters

• Plant controller

• Network operator interfaces

The specification should define required signals, including:

• Breaker open/closed status

• Breaker available status

• Local/remote status

• Protection trip

• Relay alarms

• Trip circuit healthy

• Spring charged

• Feeder voltage

• Current

• Active power

• Reactive power

• Power factor

• Energy measurement

• Fault records

Communication requirements may include IEC 61850, Modbus, DNP3, or another project-specific protocol.

The communication architecture should be confirmed before equipment manufacture so the relay, network interface, I/O count, control wiring, and cybersecurity requirements are properly coordinated.

14. Plan Cable Termination and Footprint Early

BESS projects can involve substantial cable quantities because multiple battery blocks may connect into the same MV collector system.

Project teams should define:

• Cable size

• Cable type

• Number of cables per phase

• Cable entry direction

• Minimum bending radius

• Cable termination height

• Cable trench arrangement

• Screen earthing

• Surge arrester location

• CT arrangement

A panel that is electrically rated correctly can still create major site problems if the cable compartment cannot physically accommodate the required terminations.

The overall switchroom footprint should also include:

• Operating clearance

• Maintenance access

• Rear access where required

• Arc duct clearance

• Cable bending space

• Lifting access

• Panel extension space

This is especially important where the equipment is integrated into a prefabricated e-house.

15. Consider Future Expansion

Battery energy storage projects are often expanded in stages.

A project may initially install only part of the ultimate MW or MWh capacity and add additional battery blocks later.

If future expansion is possible, consider:

• Spare switchgear panels

• Extendable busbars

• Busbar current capacity

• Future transformer feeders

• Protection relay capacity

• SCADA I/O

• Auxiliary supply capacity

• Switchroom space

• Cable routes

• Increased future fault level

Providing appropriate expansion capacity during the initial design may be easier than modifying an energised MV switchboard later.

16. Testing and Documentation Are Part of the Equipment

For EPC, utility, and renewable projects, documentation quality can directly affect commissioning.

The MV switchgear package should specify requirements for:

• Type test reports

• Routine test reports

• Factory Acceptance Test

• General arrangement drawings

• Single-line diagrams

• Schematic diagrams

• Wiring drawings

• Interlocking diagrams

• CT and VT schedules

• Protection relay settings

• Relay configuration files

• Cable termination drawings

• Communications architecture

• Operation and maintenance manuals

• Spare parts lists

• Recommended maintenance schedules

• Commissioning procedures

Leistung’s existing renewable switchgear guidance similarly identifies type tests, routine tests, FAT records, relay information, CT/VT details, drawings, manuals, and commissioning documentation as important procurement deliverables.

17. Lifecycle Support Matters for BESS Projects

BESS equipment is expected to operate as part of a long-term energy asset.

MV switchgear should therefore be evaluated based on more than purchase price and delivery time.

Ask suppliers about:

• Local Australian technical support

• Spare parts

• Circuit breaker replacement options

• Relay support

• Training

• Commissioning assistance

• Maintenance intervals

• Retrofit capability

• Future extensions

• Warranty

• End-of-life support

This is particularly important for remote renewable and mining projects where an equipment failure can require significant travel, specialised personnel, and extended downtime.

Conclusion

Selecting MV switchgear for BESS projects requires more than choosing a voltage rating and circuit breaker.

Battery energy storage introduces bidirectional power flow, inverter-based fault behaviour, dynamic operating modes, transformer coordination, harmonic considerations, auxiliary loads, automation requirements, and potentially demanding environmental conditions.

For Australian BESS developers, EPC contractors, utilities, mining companies, and infrastructure owners, switchgear should therefore be engineered as part of the complete battery energy storage electrical system.

The best specification connects the PCS, transformer, MV network, protection system, SCADA architecture, auxiliary supply, and grid connection requirements into one coordinated design.

Getting those decisions right before procurement can help improve safety, simplify commissioning, reduce modification risk, and support reliable BESS operation over the full asset lifecycle.

Talk to Leistung Energie About MV Switchgear for Your BESS Project

Planning a battery energy storage project in Australia?

Leistung Energie Australia provides MV switchgear, power transformers, distribution transformers, and supporting power quality equipment for renewable energy, BESS, utility, mining, and infrastructure applications.

Contact the Leistung Energie team to discuss your BESS single-line diagram, voltage level, fault duty, protection requirements, transformer interface, environmental conditions, and lifecycle support needs before finalising your switchgear specification.