Surge Protection
Surge protection uses Surge Protective Devices (SPDs) to clamp transient overvoltages to safe levels and divert excess surge energy to ground, preventing damage to sensitive electronic equipment from lightning strikes, utility switching, or internal load switching.
In manufacturing and asset reliability, SPDs are installed in multiple layers (service entrance, load centers, MCCs, and panelboards) to mitigate both externally and internally induced surges, as 80% of surges originate internally. They are mandatory in hazardous areas with explosive materials and for IEC61158-2 communication systems like Foundation Fieldbus H1 and Profibus PA to ensure continued process control after lightning events. Maintenance protocols require yearly testing and inspection after every lightning strike per IEC 60079-14 and IEC 62305-3.
- Inadequate grounding: SPDs fail to divert energy if not connected to a low-inductance ground path, causing chassis ground coupling and component latch-up.
- Single-layer protection: Installing only at the service entrance without downstream protection allows surge let-through to damage downstream controls and MCCs.
- Ignoring cumulative damage: Failing to replace SPDs after a strike or ignoring degraded MOVs/GDTs leads to reduced suppression capability and eventual equipment failure.
What is the minimum surge current rating for a service entrance SPD?
80,000 amperes per phase.
Which standard defines surge testing waveforms for industrial equipment?
IEC 61000-4-5 (1.2/50μs voltage, 8/20μs current).
How do you prevent common-mode surge coupling into chassis?
Use bonding straps and low-inductance grounding paths; avoid floating metal structures.