Surge Arresters

Surge Arresters

Surge arresters (overvoltage protectors) are protective interface components designed to prevent transient voltage events from damaging sensitive electronics in measurement and communication systems. They are installed on signal, communication, and power conductors to divert short-duration surge energy away from instruments and automation inputs, preserving measurement continuity and reducing the likelihood of cascading failures.

Even brief, non-destructive transients can destabilize loops, corrupt communications, or create nuisance alarms; larger events can destroy I/O cards, transmitters, or fieldbus couplers. Direct and indirect lightning strikes, as well as switching operations within a process, can inject voltage overloads into supply lines and communication circuits. In modern plants with dense electronics and long cable runs, surge protection becomes a practical availability measure, not just a “nice to have.”

A well-applied surge arrester provides a low-impedance path to earth during an overvoltage event while remaining effectively transparent during normal operation. Protection is available for 4–20 mA signal cables, for fieldbus communication lines such as HART, PROFIBUS PA, and FOUNDATION Fieldbus, and for power circuits feeding field devices or cabinets. By matching protection behavior to the connected electronics, surge arresters can limit stress on components without introducing measurable signal distortion or interference drops.

Typical applications include instrument loops routed outdoors or between buildings, field devices installed on tall structures or exposed pipe racks, and fieldbus trunks/spurs that traverse electrically noisy areas. They are widely used in process automation and measuring/communication technology in industries such as chemicals, pharmaceuticals, water and wastewater, and food processing. Both DIN-rail models for cabinets and field-mount versions for near-device installation support protection at the most effective location.

Selection should consider the protected circuit type (power vs. signal vs. fieldbus), mounting approach (cabinet rail vs. field), and required approvals such as ATEX or SIL where applicable. Effective installation also requires attention to grounding: the diversion path must be short, robust, and bonded to an appropriate earth reference, otherwise protection performance degrades. Coordinated protection - layering cabinet-level and field-level devices - often yields the best resilience for critical loops.

Instrumentation and Controls., an exclusive authorized representative of sales and service for Endress+Hauser.