Lightning Arresters and Lightning Rods: What Each Protects and How to Specify

"Lightning arrester" and "lightning rod" are used interchangeably in conversation, but they are different devices doing different jobs — and a protection scheme that confuses them leaves a gap exactly where the money is. A rod intercepts the strike; an arrester diverts the surge. Most real installations need both, coordinated with surge protective devices at the boards.

Two devices, two jobs

• Lightning rod / air terminal: a metal point mounted above the structure, connected by down conductors to earth. It offers the strike a preferred, controlled path so the current flows through metal you chose, not through masonry, wiring or people.
• Lightning arrester / surge arrester: connected across live conductors and earth, normally invisible to the system. When a surge arrives — from a nearby strike or switching — it conducts, diverting the surge current to earth and clamping the voltage the equipment sees, then recovers.

A rod without arresters still lets induced surges enter through overhead lines. Arresters without a rod leave the structure itself exposed to direct strike damage. The complete scheme is rod + down conductor + earth + arresters at service entrance + SPDs at sensitive boards.

Types by application

• Station type: heavy-duty arresters for substations and line entrances, typically polymer-housed with ribbed sheds for creepage distance, mounted on brackets or cross-arms.
• Distribution / line type: for pole-mounted transformers and line protection on medium-voltage networks.
• Building type: rods and compact arresters for structures — roofs, masts, service entrances.

What to check when specifying

• System voltage: the arrester's rated voltage must suit the network it protects, including temporary overvoltage conditions.
• Discharge current capability: the surge current the device can divert repeatedly without damage — match it to the exposure of the site (open rural overhead lines demand more than a dense urban cable network).
• Housing and creepage: ribbed polymer housings give long creepage paths and resist pollution and tracking; verify the housing suits the site pollution level.
• Earth: every device in the scheme is only as good as the earth electrode it terminates on. Rods, arresters and SPDs share a bonded earth system.
• Coordination: service-entrance arresters and board-level SPDs must coordinate so the surge energy is shared, not dumped entirely on one device.

Maintenance reality

Polymer-housed arresters are largely maintenance-free, but the scheme is not: inspect down-conductor connections after any known strike event, check earth resistance on a schedule, and replace arresters that show housing damage or have operated on a severe surge — a diverted surge is energy the device absorbed on your behalf.

From our range

We supply the hardware for both jobs: polymer-housed surge arresters for building and distribution duty (10kA class), porcelain-housed station-type arresters for substation and line entrances, stainless steel lightning rods rated to 200kA, and copper rods for building protection systems. Tell us the structure or network, the exposure and the system voltage; we return a coordinated set rather than a single part number.