How does Surge-Trap® work?
A surge protective device (SPD) presents high impedance during normal operation. When a surge occurs, it limits the voltage and diverts surge current into the earthing path. Thermally protected varistor technology helps the component disconnect safely at the end of its service life.
STZ and STXT compared
| Product family | Typical location | Monitoring |
|---|---|---|
| STZ | Service entrance, automatic transfer switch and main distribution | Status LEDs, phase loss indication, surge counter, audible alarm and dry contact |
| STXT | Distribution and subpanels | Per-phase status LEDs and phase loss indication; alarm and dry contact depending on model |
Both series are listed as Type 1 SPDs in the manufacturer documents. For the 380/220 V configuration in the brochure, STZ offers 100–300 kA per phase and STXT offers 100 or 200 kA surge current options. These ratings alone do not determine the right device; the supply arrangement and protected equipment must be checked for each project.
Key features
- Thermally protected varistors help the device disconnect safely at the end of its service life.
- Per-phase status and phase loss indicators make device condition visible to maintenance teams.
- The STZ range includes a surge counter, audible alarm and dry contact. STXT alarm and dry contact options vary by model.
- Devices at the service entrance and downstream distribution points are selected together for the actual electrical arrangement.
A coordinated protection approach
Protection at the service entrance and distribution panels is considered together. Short, appropriately routed connecting conductors matter when limiting the residual voltage seen by equipment. The condition of the earthing system also needs review; earthing monitoring supports that maintenance work.
See the Surge-Trap® brochure for product ranges, options and electrical data.
Where is it used?
Data centres, manufacturing plants, energy distribution panels and commercial buildings where outages are costly may need protection from the service entrance through to critical loads. Exposure, supply arrangement, panel location and connections govern the selection.
Frequently asked questions
Will one SPD at the service entrance protect all equipment?
Not always. Protection needs at the service entrance and distribution panels are assessed separately; suitable stages and connections are defined for the project.
Is the highest kA rating always the best choice for a panel?
No. Supply voltage, panel location, connections and the needs of protected equipment matter alongside surge current capacity.
What are the status indicators and alarms for?
They make device condition visible to the maintenance team. An alert prompts an on-site check of the relevant phase and protection module; it does not replace routine maintenance.