Keeping pace with a complex grid

With more renewables coming into the energy market, the complexity of grid integration requirements is increasing. This means that high-voltage (HV) switchboards, control panels and switchgear need to be carefully designed to meet safety and performance criteria for new and demanding applications.

“Switchboard and switchgear requirements differ from state to state, so it’s important that any supplier understands the technical requirements for the region they are working in,” said Steve Bell, Managing Director at Clean Tech Controls, a Sydney-based company specialising in the integration of renewable energy technologies across Australia.

High-voltage connected sites, which include anything above 1000 V, according to Australian standards, often have different requirements set out by each distributed network service provider (DNSP) in addition to each state’s Service Installation Rules.

“In well-designed high-voltage installations, you have to have more electronics, control, measurement and communication devices in the switchboard, all working together in a reliable way,” Bell said.

Switchboard and switchgear requirements differ from state to state, so it’s important that any supplier understands the technical requirements for the region they are working in. Image courtesy of Clean Tech Controls.

High-voltage switchgear considerations

According to Bell, switchgear for any application should be tailored to suit each project, but there are a number of features that may need to be included in the HV switchboard or control panels:

• Protection relays, which measure the power and disconnect the fault before it can cause injury or damage.
• Supervisory control and data acquisition (SCADA) panels, SCADA gateways, timeclocks, power supply inverters, programmable logic controllers (PLCs) and remote terminal units (RTUs) — allowing the asset owner to communicate with the asset and monitor its status.
• Integrated uninterruptable power supply (UPS) panels to provide power to the switchboard and control panels if the grid power is lost.
• Rapid earth fault current limiter (REFCL) compatibility, which is a special requirement in some states and regions.
• Factory testing, to ensure quality and reliability.
   

“At our Tempe facility in Sydney, we perform factory testing on switchgear, including primary injection testing of voltage transformers (VTs), current transformers (CTs), bus resistance and secondary injection testing of the protection relay,” Bell said.

Renewable energy assets

Renewable generation assets such as solar and wind farms often have complex grid integration and control requirements for high-voltage switchgear.

“Solar and wind farms tend to be more complicated than standard ring main units (RMUs) due to the grid integration and control requirements, so having an experienced switchgear provider is even more crucial, both for renewables and for other purposes,” Bell said.

Often the DNSP has specific control over the assets involved. “This is normally to monitor or remotely disconnect the site, but could also involve dynamic export limits or other more specific types of control,” Bell explained.

Renewable energy projects such as wind, solar or battery installations often trade on the Frequency Control Ancillary Services (FCAS) market, which has its own specific requirements. FCAS is a process used by the energy market operator to maintain the frequency of the system, by injecting or reducing energy to better manage supply and demand.

These renewable generation assets are being used to supply green power to sites including manufacturing, mining, infrastructure and construction, as Australia accelerates its transition to net zero.

Safety features

“For high-voltage applications, we can build indoor- or outdoor-rated enclosures to house the switchgear and control panels on one skid,” Bell said.

For further safety, Clean Tech Controls can construct the switchboard with either upward or downward arc venting. This is because, when there is a fault, a lot of energy needs to be dissipated through the switchgear — often as a fireball — and this must never be allowed to erupt close to where someone might be standing, so a release either above or below is required.

“For upward arc venting, we put a pressure release plenum on top of the enclosure, or for downward arc venting there needs to be adequate space in the pit below the switchboard to meet the requirements for dissipating the pressure,” Bell explained.

Clean Tech Controls said it supplies switchboards with arc front lateral rear (AFLR) ratings, meaning a person can safely be standing in front, at the side or behind the switchgear if there is a fault.

Top image caption: Clean Tech Controls Managing Director Steve Bell.