Maximising surge protection safety

September 2nd, 2014, Published in Articles: Vector


Servicing surge protection devices (SPDs) safely without impacting critical operations has traditionally been difficult but a new generation SPDs is solving this problem.

Servicing traditional SPDs poses serious risks to maintenance personnel and mission-critical workloads. If the SPD has an internal disconnect, power on the line side of the disconnect continues to flow even when the disconnect is open, exposing technicians to potentially hazardous voltages and arc flash events.

Where the SPD lacks an internal disconnect, maintenance personnel must shut off upstream power completely before allowing service personnel to open the device. Often, the source of that power is a panel board supporting critical loads. As such panels sometimes offer no way to interrupt power solely to the SPD, technicians must shut off electricity to all downstream devices during SPD maintenance procedures. This results in increased downtime for affected workloads, and even facilities with parallel power architectures suffer heightened risk of downtime.

Mitigating safety hazards

The latest SPDs include functionality designed to prevent injury without affecting downstream loads. Organisations seeking maximum safety and surge protection should use SPDs with critical attributes:

Robust safety features

Next-generation SPDs employ a variety of innovative techniques to safeguard personnel during maintenance procedures. These include separate wireways for incoming power cables and surge module wiring, enabling technicians to perform surge module administration without risking electrical shock or exposing themselves to arc flashes.

The latest SPDs include hinged safely barriers for both incoming cable access and internal maintenance access which prevent administrators from touching energised surfaces accidentally when the device is open for servicing.

Fig. 1: Next-generation SPDs have safety barriers and lockout/tagout provisions that protect technicians from injury during maintenance procedures.

Next-generation SPDs with internal disconnects have built-in lockout and tagout provisions to ensure power is shut off before maintenance work commences, and that it remains off until servicing is complete (see Fig. 1).

Next-generation SPDs employ thermally-protected metal-oxide varistors (MOVs) as their core surge suppression component. Should a temporary overvoltage, high fault current or other abnormal electrical condition occur, the SPD removes these MOVs from the circuit rapidly and safely before an arc flash can develop, shielding technicians from harm.

Dual-colored LED status indicators

Status lights on traditional SPDs have only two readings: on and off. Advanced SPDs have dual-color LED lights that also show administrators the protection status for the unit as a whole or any of its phases on 3-phase devices.

Models requiring a neutral wire have an additional dual-coloured light indicating the power and protection status of the neutral-ground (N-G) connection. Older SPDs often have N-G mode protection but no means of verifying its present status.

Reduced need for periodic aintenance

Next-generation SPDs make limited-to-no use of components that require periodic administration. This protects personnel from maintenance-related injury by reducing the number of service procedures they must perform.

Other important features

Though safety and surge protection are the most critical priorities to consider when evaluating next-generation SPDs, companies should also look for models with a number of important features.

Maximum current ratings

Look for devices offering a 20 kA nominal discharge current rating and a 200 kA short-circuit current rating, both of which are the highest ratings available at present.

Support for critical standards

At a minimum, any next-generation SPD you choose should meet the UL1449 third edition and 1283 fifth edition standards.

Compact form factor

Fig. 2: Next-generation SPDs feature compact, flexible form factors.

In addition to conserving space in your data center, SPDs with a compact case can be mounted in close proximity to critical loads, ensuring better protection by reducing let-through voltage (see Fig. 2).

Application flexibility

Every organisation has different and evolving needs. The next-generation SPDs they use should therefore offer the following:

  • Support for wire sizes from #10 to 1/0.
  • Both terminal blocks and optional internal circuit breaker disconnects.
  • Top, bottom and side wire entry.
  • A rotating front panel display that accommodates both left and right mounting.
  • Painted steel NEMA 4 and stainless steel NEMA 4X enclosures for mounting in indoor, outdoor and harsh environments.


Thanks to the recent introduction of more advanced SPDs with innovative safety functionality, system operators can now enjoy the best of both worlds: protection for sensitive equipment from dangerous surges during normal operation and protection for technicians from safety risks during maintenance procedures.
Organisations that place a high value on both uptime and workplace safety should investigate these next-generation products.

Contact Marlene Coetzee, Eaton,  Tel (011)824-7400,

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