Incorrect grounding can cause:
Electrical hazards to personnel,
damage to live equipment,
electromagnetic interference,
and non-compliance with the Low Voltage Electrotechnical Regulation (REBT).
This article describes best practices for installers in Spain for the correct connection and grounding of shielded fiber optic cables.
2. Applicable regulations in Spain
The main references are:
REBT — RD 842/2002
ITC-BT-18: Earthing
ITC-BT-24: Overvoltage protection
UNE-EN 60794 — Fiber optic cables
UNE-EN 50310 — Earthing and equipotential bonding in ICT
TIA-607 (supplementary technical reference)
Regional regulations and local ordinances
⚠️ Spanish regulations should always take precedence over generic international recommendations.
3. When and Where to Ground
3.1 Installations Within the Same Building
The shield is normally grounded at one end only (building entrance or main rack).
It is connected to the telecommunications main grounding bar (TMGB) or the building's equipotential bonding network.
Objective: to prevent ground loops.
3.2 Installations between buildings.
The shielding must be connected at both ends.
Additional surge protection may be required.
Objective: to equalize potentials and protect against indirect lightning strikes.
3.3 Outdoor Installations and Public Conduits
Mandatory earthing.
Coordination with the site's electrical manager.
Use of watertight boxes with certified earth terminals.
4. Recommended Procedure
Step 1 — Preparation
Remove the cover, respecting bend radii.
Identify the metal armor, tape, or drain wire.
Maintain electrical continuity up to the connection point.
Step 2 — Shield Connection
Use manufacturer kits or UNE-certified clamps.
Clean metal surfaces (without paint or varnish).
Ensure constant mechanical pressure.
Step 3 — Grounding
Connect to the rack's equipotential bonding bar or main telecommunications busbar.
Use a green/yellow copper conductor, cross-section according to ITC-BT-18 (usually ≥ 6 mm²).
Keep the length as short and straight as possible.
Step 4 — Verification
Measure continuity between the shield and ground.
Record the connection in the installation documentation.
Perform periodic visual inspection.
5. Common Errors in Spain
Error
Non-compliance Failure to connect the shielding ITC-BT-18
Use of metallic structure as ground Not permitted
Failure to respect conductor cross-section Thermal risk
Failure to document grounding Lack of traceability
Connecting at non-equipotential points Potential differences
6. Best practices
Always consult the cable manufacturer's guide
Coordinate with a licensed electrical installer
Keep grounding diagrams up to date
Use clear connection labels
Check after storms or electrical upgrades
7. Conclusion
In Spain, grounding shielded fiber optic cables is not optional: it is a safety requirement regulated by the REBT (Low Voltage Electrotechnical Regulations) and UNE standards. Proper implementation protects people, equipment, and infrastructure, and avoids legal liability for the installer.
A good installer doesn't just connect fibers—they guarantee a safe, compliant, and long-lasting installation.
