Instrument lightning protection grounding is mainly to guard against induced lightning. When lightning strikes nearby, long cables act like antennas and induce instantaneous high voltage, which can break through the instrument's chips.
On-site damage commonly appears in three forms: data jumps, communication interruptions, and module burnout. The electronic components in industrial instruments typically have low voltage tolerance—a few thousand volts of surge is enough to cause a fault.
It mainly relies on three coordinated measures:
●SPD Current Diversion — Installed on power lines and signal lines, it quickly conducts when a surge arrives, directing the current to the grounding busbar.
●Equipotential Bonding — Bond the instrument housing, cable trays, pipes, and cabinets together. When lightning strikes, all components rise in potential together, reducing the risk of mutual breakdown.
●Shielding and Grounding — Metal cable trays, conduit pipes, and cable shielding layers must be continuously conductive and connected to a unified grounding system.
Where failures most often occur:
●Ground wires that are too long — SPD grounding wires should generally be kept within 0.5 meters. Excessive length generates additional voltage, and the residual voltage may exceed the instrument's tolerance.
●Focusing only on grounding resistance — A qualified resistance only indicates a good DC path. The connection path during a lightning strike is equally critical.
●Complete isolation of different grounds — During a lightning strike, a high potential difference can appear between different grounds, making equipment breakdown more likely.
●Cable trays broken midway — Loose connections, paint, or corrosion can break electrical contact, weakening the shielding effect.
So, effective lightning protection grounding means giving surges a short and reliable path while keeping all related metal parts at roughly the same potential.
