Surge Arresters

Surge Arresters

Surge arresters (overvoltage protectors) are protective components designed to safeguard instrumentation and communication electronics from transient voltage events. Even brief disturbances can disrupt measurement, control, and data availability, so surge protection is often treated as an availability measure rather than only as hardware protection. The primary threats include lightning effects (direct or induced) and switching operations that inject overvoltage into wiring.

The operating principle is controlled energy diversion. When a transient appears on a signal or power conductor, the arrester provides a low‑impedance path to earth so the surge is safely routed away from sensitive electronics. This is applied across typical process automation circuits including 4–20 mA signal cables, power lines, and communication wiring for fieldbus systems such as HART, PROFIBUS PA, and FOUNDATION Fieldbus. Properly selected protection stays passive during normal operation, minimizing impact on signal integrity while providing a controlled discharge path during surges.

Form factors support both cabinet and field deployment. DIN‑rail units protect loops in control cabinets and marshalling panels, while field‑mount variants protect at the device or junction point to intercept surges before they propagate. Selection depends on circuit type (power vs signal vs bus), grounding topology, and the location of vulnerable electronics. Coordinated protection across zones (field, junction, cabinet) can reduce cumulative stress on instrument I/O.

Benefits include improved plant availability, fewer device failures, and reduced maintenance disruptions after electrical events. Options with intrinsic safety and functional safety approvals enable use in hazardous areas and safety‑relevant loops, while device designs matched to process automation electronics help maintain measurement functionality without introducing unwanted voltage drops or signal disturbances under normal operation.

Typical applications include outdoor and exposed installations, long cable runs, tank farms, remote pump stations, and any facility with frequent switching transients from large motors or variable frequency drives. Surge arresters are also applied on fieldbus trunks and spur lines to protect multiple devices on a segment and to minimize cascade failures after a transient event. They are widely used in process automation and measurement/communication systems in sectors such as chemical, pharmaceutical, water and wastewater, and food production.

Forberg Smith, an exclusive authorized representative of sales and service for Endress+Hauser.