NFPA 79:2018 - Updated for SPDs on industrial machinery with interlock circuits

NFPA 79:2018 is the mandatory guideline that applies to electrical or electronic equipment and industrial machines supplied from nominal AC distribution voltage of 1000 volts or less.
 
The standard applies to the point of connection of the supply circuit conductors to the electrical equipment of the machine.
 
The 2018 released version clarifies to align with the National Electric Code and requires that surge protection devices (SPDs) shall be provided for industrial machinery with safety interlock circuits to protect against the effects of overvoltages due to lightning or switching surges.
 
Application of SPDs on the industrial machinery AC power input will assure the safe operation of high power systems and to prevent a fire that might be caused by lightning flashover and ground potential rise from nearby strikes.
 
Operator safety is further assured by the application of SPDs on all of the control interlock circuits, intrusion alarms, and safety switches.
 
This includes both AC power type emergency stop interlocks in addition to the low voltage data circuits and power over ethernet equipment used to monitor industrial machines.
 
Safety interlock and control circuits that prevent machine pinch points, hand intrusion, and assure worker safety must be resilient enough to withstand severe surge environments and lightning events.
 
Lightning is not the only source of surge events, especially around such high-intensity electrical motors, compressors, welders, and presses associated with industrial machinery.
 
These types of motors will produce switching transients and can even be a source of static electricity buildup. Contact DEHN to speak with our experts for guidance on protection applications.