A failed PLC input card after a nearby lightning event is rarely just a replacement-parts problem. It can stop a conveyor, interrupt a water treatment process or leave a site with unexplained faults for days. The best industrial surge protection devices are selected as part of a coordinated protection system, not simply chosen by the highest kA figure on a datasheet.
For Australian industrial sites, selection needs to account for the incoming electrical service, exposure to lightning, switchboard arrangement, earthing system, sensitive automation assets and connected copper communications. Mining, water, processing, rail and energy facilities can all face high consequences from a relatively short transient event. A properly specified surge protection device (SPD) helps limit that risk while supporting planned maintenance and equipment availability.
What makes an industrial SPD fit for purpose?
An industrial SPD must do more than survive a surge. It needs to protect equipment at a voltage level that downstream components can tolerate, work correctly with the site earthing arrangement, coordinate with other protective devices, and provide a practical way to identify end of life.
This is why a compact commercial power board protector is not a substitute for panel-mounted industrial protection. Industrial installations require devices designed for switchboards and control panels, with clear surge ratings, short-circuit performance, thermal disconnection and status indication. In critical applications, a volt-free remote indication contact can be equally valuable, allowing a failed or degraded module to be reported to a PLC, BMS or maintenance system.
The right device also depends on where it sits in the installation. Protection at the main switchboard manages high-energy events entering through the supply. Protection at distribution boards reduces residual transients closer to loads. Fine protection at a machine panel or equipment connection limits what remains for sensitive electronics. These layers must be coordinated rather than treated as unrelated purchases.
Best industrial surge protection devices by application
There is no single best SPD for every industrial facility. The appropriate product family is determined by the source and severity of the transient, the point of installation and the asset being protected.
Main switchboard lightning protection
At the incoming supply, a Type 1 or combined Type 1+2 SPD is generally considered where lightning current can enter the electrical installation. This is particularly relevant for sites with overhead supply exposure, external lightning protection systems, isolated infrastructure or a high lightning-risk location.
The key capability is impulse-current handling, commonly expressed as Iimp. A Type 1 device is intended to manage part of a direct lightning current waveform rather than only switching transients. It is not automatically required at every site, and an unnecessarily high-duty unit may add cost without improving the practical outcome. A lightning risk assessment and the installation arrangement should drive the decision.
At this level, check the SPD's connection method, pole configuration, neutral arrangement, short-circuit withstand capability and upstream protective-device requirements. In an Australian MEN installation, the correct configuration for the supply system is critical. An SPD should never be selected in isolation from the switchboard fault level or earthing design.
Distribution board protection
Type 2 SPDs are the core protection layer for many industrial distribution boards. They are designed to manage induced lightning effects and switching surges that travel through the installation. Typical applications include submains feeding MCCs, process areas, workshops, plant rooms and remote buildings.
Important values include nominal discharge current (In), maximum discharge current (Imax), maximum continuous operating voltage (Uc) and voltage protection level (Up). High discharge ratings are useful, but the lowest practical Up can matter more when protecting sensitive automation equipment. The device must still have an appropriate Uc for the actual supply and its expected voltage conditions. Selecting too close to nominal voltage can lead to premature operation or failure.
For 400/230 V systems, engineers should verify whether a 3+1, 4+0 or another arrangement suits the earthing system and installation requirements. This is a design choice, not a catalogue shortcut.
Control panels, PLCs and VSDs
Machine control panels often contain the equipment most vulnerable to transient damage: PLCs, remote I/O, industrial PCs, safety controllers, operator terminals, servo drives and variable speed drives. A coordinated Type 2 or Type 2+3 device at the panel supply can provide a lower residual voltage than upstream protection alone.
The layout is as important as the SPD rating. Keep conductors between the active conductors, SPD and earth bar as short and direct as practical. Long, looping leads add inductance and raise the voltage seen at the protected load during a fast surge. A high-performing unit can deliver disappointing protection if installed with poor lead routing.
Drives require particular attention. Their supply-side protection must be compatible with the drive manufacturer's installation guidance and the panel's fault rating. Surges can damage rectifier sections and control electronics, but nuisance tripping, harmonic conditions and earthing arrangements also need consideration. Protection on the incoming supply is not a replacement for correct drive commissioning, cable practices or output-side measures where required.
Signal, data and communications protection
Power protection alone leaves a major exposure path open. Field instruments, RS-485 networks, Ethernet links, analogue loops, telemetry circuits and building-to-building communications can carry damaging transients into a control system.
Choose signal protection by the actual circuit, not by connector shape. The SPD needs to suit the operating voltage, signal type, bandwidth, current requirement, impedance and earthing method. A device intended for a 4-20 mA loop may not suit a fast data circuit, while an unsuitable Ethernet protector can affect network performance or PoE delivery.
For external instruments and long cable runs, protect both the incoming circuit and the associated control interface where the risk assessment supports it. Shield termination, separation from power cables and a low-impedance earth reference remain part of the overall outcome.
How to compare industrial SPD specifications
Datasheets can appear comparable while describing very different performance. Start by confirming the device classification under the relevant IEC 61643 series and its intended location in the protection system. Then assess the ratings in the context of the installation.
A practical comparison should cover:
- impulse-current rating (Iimp) for Type 1 applications and discharge-current ratings (In and Imax) for Type 2 applications;
- voltage protection level (Up), considering the withstand capability of the load being protected;
- maximum continuous operating voltage (Uc) and suitability for the system voltage and earthing arrangement;
- short-circuit current rating, required backup fuse or circuit breaker, and coordination with existing protection;
- visual status indication, replaceable modules and remote signalling requirements; and
- enclosure, mounting and environmental suitability for the switchboard or field enclosure.
Installation details that determine performance
SPDs should be installed in accordance with the manufacturer's instructions and the applicable requirements of AS/NZS 3000, AS/NZS 1768 and project standards. Final design and installation must be undertaken by suitably qualified personnel.
Earthing quality is central to surge protection. An SPD diverts transient energy to earth, so a poor earth path limits its ability to control voltage. Bonding between switchboards, cable trays, structural steel and external services also affects how transient energy moves through a site.
Physical placement matters. Install the SPD close to the protected busbar or load connection point, avoid excessive conductor length, and use conductor sizes and protective devices specified by the manufacturer. Do not assume an existing breaker is acceptable as backup protection. Its rating, breaking capacity and coordination characteristics need to be checked.
Maintenance teams should include SPD inspection in routine switchboard checks. Status windows and remote contacts help, but they do not remove the need to investigate a device that has operated or reached end of life. Following major storm activity or electrical faults, inspection is sensible even where no immediate equipment failure is apparent.
Specify protection as a system, not a part number
The most effective industrial surge protection strategy starts with a site review: incoming supply configuration, lightning exposure, existing protection layers, critical loads, external cable routes and required alarm visibility. That review often identifies signal and communications circuits that have been overlooked, or shows that an upstream device is not adequately coordinated with machine-level protection.
Novaris industrial surge protection products are well suited to this type of application-led selection, but the product should follow the electrical design rather than lead it. Tech Source can assist engineers, integrators and maintenance teams with matching protection requirements to switchboard, control-panel and field-instrument applications.
A well-specified SPD will not prevent every electrical incident, but it can turn an uncontrolled transient into a manageable maintenance event. For facilities where availability matters, that is a practical engineering decision worth making before the next storm, switching event or unexplained PLC fault.