33kV Switchgear for Renewable Energy Projects: Specification Guide for Solar, Wind and BESS

Australia's transition toward utility-scale solar, wind generation and battery energy storage is increasing the importance of reliable medium-voltage collector systems.

At many renewable energy sites, 33kV switchgear sits between individual generation or storage blocks and the main grid connection substation. It provides the switching, protection, isolation, metering and control required to collect power from multiple feeders before transferring it toward the grid connection transformer.

However, specifying 33kV switchgear involves much more than selecting a nominal voltage and panel quantity.

Fault levels, busbar current, internal arc classification, cable interfaces, protection relays, SCADA architecture, environmental conditions and grid connection requirements must all be established before equipment procurement.

For EPC contractors, renewable developers, utilities and consulting engineers, a well-developed 33kV switchgear specification can significantly reduce engineering changes, commissioning problems and project delays.

This guide outlines the main considerations when specifying switchgear for solar farms, wind farms, BESS and hybrid renewable energy projects in Australia.

Why 33kV Is Common in Renewable Energy Collector Systems

Large renewable energy facilities typically contain multiple generation blocks distributed across a substantial site.

A solar farm may have dozens of inverter-transformer stations. A wind farm may consist of multiple turbines connected through underground cable circuits. A BESS facility may use multiple power conversion system and transformer blocks.

Rather than connecting every block directly to the high-voltage substation, power is commonly collected through an MV network.

Typical collector voltages may include:

• 11kV

• 22kV

• 33kV

The appropriate voltage depends on project capacity, feeder length, equipment architecture, cable losses, grid connection arrangement and network requirements.

For larger projects, a 33kV collector system can provide an effective balance between power-transfer capability, cable requirements, equipment availability and substation design.

The 33kV switchgear therefore becomes a critical interface between renewable generation assets and the project's main grid connection infrastructure.

1. Define the Electrical Architecture Before Selecting Switchgear

The first stage of any 33kV switchgear procurement package should be a controlled single-line diagram.

Do not begin with panel quantities alone.

The single-line diagram should clearly identify:

• Solar inverter or BESS transformer feeders

• Wind turbine collector feeders

• Main transformer incomers

• Bus sections

• Bus couplers

• Station auxiliary transformers

• Reactive compensation equipment

• Earthing equipment

• Revenue or operational metering

• Future expansion feeders

For example, will the collector system use one continuous busbar, sectionalised buses, or multiple independent bus sections?

Will a bus coupler normally remain open or closed?

Can one transformer support another bus section during an outage?

These decisions influence switchgear ratings, protection zones, interlocking logic and SCADA functionality.

A supplier should therefore receive the project single-line diagram together with the technical specification rather than being asked to determine the electrical architecture independently.

2. Match the Rated Voltage and Insulation Level to the System

A nominal 33kV network does not mean that every equipment rating should simply be stated as "33kV".

The switchgear's rated voltage and insulation performance must be coordinated with the highest system voltage and the project's insulation coordination study.

Depending on the applicable equipment design and project standard, equipment classes above the nominal operating voltage may be required.

A comprehensive 33kV switchgear specification should therefore define:

• Nominal system voltage

• Highest system voltage

• Rated switchgear voltage

• Power-frequency withstand voltage

• Lightning impulse withstand level

• System frequency

• Earthing arrangement

• Required creepage distance where applicable

Site altitude should also be confirmed because installations above standard service conditions may require insulation derating or alternative equipment selection.

The objective is to coordinate the complete insulation system rather than choosing equipment from nominal voltage alone.

3. Calculate Continuous Current and Busbar Ratings

Continuous current requirements depend on the actual renewable energy architecture.

For example, the main busbar may carry the combined output of several solar blocks while an individual feeder only carries power from one inverter transformer.

For BESS, the equipment may also experience bidirectional current because the plant operates in both charging and discharging modes.

The specification should define separate ratings for:

Parameter	Requirement
Main busbar	Continuous rated current
Transformer incomer	Maximum operating current
Renewable feeder	Maximum generation current
BESS feeder	Charging and discharging current
Bus coupler	Maximum transfer current
Circuit breaker	Rated continuous current

Designers should also account for ambient temperature, enclosure ventilation and installation conditions.

This is particularly important where 33kV switchgear Australia projects are installed in prefabricated substations, e-houses or remote locations with high ambient temperatures.

A standard catalogue current rating should not automatically be assumed to represent the available continuous current under the actual site conditions.

4. Confirm the Short-Circuit Fault Level

Fault level is one of the most important technical parameters in renewable energy switchgear procurement.

The equipment must safely withstand and interrupt credible short-circuit currents at its installation point.

The specification should identify:

• Initial symmetrical short-circuit current

• Rated short-time withstand current

• Required duration, such as 1 or 3 seconds

• Peak withstand current

• Circuit breaker breaking current

• Circuit breaker making current

• Earth-fault current

• Future network fault level where applicable

Renewable energy systems require particular attention because fault contribution can originate from several sources.

These may include:

• The external transmission or distribution network

• Grid connection transformers

• Renewable inverter systems

• BESS power conversion systems

• Other connected generation

• Parallel transformers or bus sections

Inverter-based resources have different short-circuit characteristics from traditional synchronous generators. The final switchgear rating should therefore be based on the approved fault study rather than simple assumptions regarding generation capacity.

Future network strengthening should also be considered where the expected grid fault level may increase over the life of the asset.

5. Specify Internal Arc Classification Clearly

Personnel safety is a major consideration for any 33kV switchgear for solar farm, wind or BESS installation.

An internal electrical fault can generate extreme pressure, heat and arc products inside the switchgear enclosure.

Internal Arc Classification, or IAC, helps define how a metal-enclosed switchgear assembly performs under specified internal arc conditions.

A technical specification should identify requirements such as:

• IAC classification

• Accessibility from front, lateral and rear areas

• Internal arc current

• Arc duration

• Pressure relief system

• Arc gas exhaust path

• Switchroom clearance requirements

An example requirement may be expressed as an IAC AFL or AFLR classification together with the specified fault current and duration.

For switchgear installed inside an e-house or prefabricated substation, the equipment cannot be considered separately from the building.

Pressure relief ducts and exhaust paths must be coordinated with the switchroom structure so that arc products are directed toward a safe area.

Type-test evidence should also correspond as closely as practical to the proposed equipment configuration.

6. AIS or 33kV GIS Switchgear?

Renewable developers frequently need to choose between air-insulated and compact gas-insulated architectures.

Air-insulated switchgear can provide straightforward inspection and maintenance access where adequate switchroom space is available.

By comparison, 33kV GIS switchgear can significantly reduce the physical footprint required for the MV switchboard and may provide additional protection against external contamination because primary components are enclosed within sealed compartments.

GIS can therefore be attractive for:

• Compact substations

• Prefabricated e-houses

• BESS sites

• Coastal environments

• Dust-prone locations

• Sites with strict footprint constraints

However, equipment architecture should not be selected on footprint alone.

Projects should evaluate maintainability, environmental requirements, gas management, spare parts, service capability, extension requirements and lifecycle support.

SF₆-free alternatives should also be considered where the project has sustainability or future environmental requirements.

7. Coordinate the Collector System and Cable Terminations

Cable interfaces frequently create problems late in switchgear projects.

A 33kV renewable collector system may involve large single-core cables, multiple cables per phase or different cable sizes between feeder types.

Before switchgear manufacturing begins, confirm:

• Cable conductor material

• Conductor cross-section

• Cable insulation type

• Number of cables per phase

• Cable diameter

• Minimum bending radius

• Termination type

• Surge arrester requirements

• Cable entry direction

• Gland plate arrangement

• Cable compartment dimensions

• Earthing arrangement

The physical termination area must allow installers to bend, terminate, test and maintain cables safely.

This can be especially challenging when large 33kV cables enter compact switchgear inside an e-house.

The switchgear supplier, cable supplier and EPC electrical designer should therefore coordinate cable interfaces before detailed manufacturing drawings are approved.

8. Engineer the Protection System Around the Application

Protection requirements should not be treated as a generic relay package supplied by the switchgear manufacturer.

Each panel has a specific protection role.

Typical functions for a renewable collector network can include:

Phase overcurrent

Earth-fault protection

Directional overcurrent

Directional earth fault

Transformer differential

Restricted earth fault

Under-voltage

Over-voltage

Under-frequency

Over-frequency

Breaker failure

Arc-flash protection

Trip circuit supervision

Synch-check where applicable

Current transformers and voltage transformers must also be selected according to protection, metering and accuracy requirements.

Protection grading should coordinate the renewable feeders with upstream grid connection protection so that faults are isolated selectively.

A fault on one collector feeder should not unnecessarily disconnect the complete renewable facility where the protection architecture allows selective isolation.

9. Define SCADA and Remote-Control Requirements

Modern renewable facilities are highly automated.

Operators may control the switchgear from a local control room, remote operations centre or network control environment.

The renewable energy switchgear package should therefore define SCADA requirements during specification rather than leaving them until commissioning.

Typical signals include:

• Circuit breaker open/closed status

• Disconnector position

• Earth switch position

• Local/remote status

• Protection trip

• Protection alarm

• Spring charged status

• DC supply failure

• Trip circuit supervision

• Current and voltage measurements

• Active and reactive power

• Energy metering

• Equipment condition alarms

Communication architecture may incorporate protocols such as IEC 61850, Modbus or DNP3 depending on project requirements.

Time synchronisation, disturbance recording, sequence-of-events recording and cybersecurity requirements should also be identified.

The SCADA point list should ideally be developed and reviewed before protection and control drawings are finalised.

10. Coordinate the Switchgear With Grid Connection Requirements

The collector switchgear is part of a much larger electrical system.

Its protection, instrumentation and controls may interact with:

• Power Plant Controller

• BESS Energy Management System

• Grid connection transformer

• Main substation protection

• Revenue metering

• Reactive power equipment

• Network control systems

• Generator performance standards

• Plant SCADA

Grid connection studies should therefore be sufficiently mature before switchgear design is frozen.

Changes to transformer impedance, earthing arrangements, protection settings or grid connection architecture can affect CT requirements, relay functionality, fault levels and switchgear configuration.

For Australian renewable energy projects, early coordination between the EPC contractor, network connection team, protection engineers and equipment suppliers can reduce redesign during the later stages of the project.

Procurement Should Begin Before the Design Is Completely Frozen

Long-lead electrical equipment can directly affect renewable project schedules.

However, ordering too early with incomplete information can be equally risky.

A better approach is to identify critical technical parameters early, including rated voltage, fault level, busbar architecture, feeder quantity, IAC requirement, cable arrangement and protection philosophy.

Remaining details can then progress through a controlled engineering and vendor-document process.

Supplier evaluation should consider more than equipment price.

Important commercial and technical factors include:

• Compliance with the technical specification

• Type-test evidence

• Manufacturing capacity

• Engineering support

• Factory acceptance testing

• Documentation quality

• Delivery schedule

• Spare parts availability

• Commissioning support

• Long-term service capability

For a renewable plant expected to operate for decades, the lowest initial equipment price does not necessarily represent the lowest project risk or lifecycle cost.

Conclusion

33kV switchgear is a critical element of the electrical infrastructure behind utility-scale solar farms, wind farms, BESS and hybrid renewable energy facilities.

A successful specification must consider the complete collector system rather than simply voltage and panel quantity.

Rated voltage, insulation coordination, continuous current, short-circuit duty, Internal Arc Classification, protection, cable interfaces, SCADA and grid connection requirements all need to work together.

For EPC contractors and renewable developers, resolving these interfaces before purchase can significantly reduce technical variations, installation problems and commissioning delays.

The objective should be clear: specify switchgear that is safe, grid-ready, maintainable and capable of supporting the renewable facility throughout its operating life.

Planning a 33kV Solar, Wind or BESS Project?

Leistung Energie supports EPC contractors, utilities and renewable energy developers with medium-voltage switchgear solutions for demanding power and grid infrastructure applications.

If you are preparing a 33kV switchgear specification, send us your single-line diagram, system ratings, fault level and project requirements.

Contact Leistung Energie Australia to discuss the right 33kV switchgear solution for your solar, wind, BESS or grid connection project.