In short: Glass-fiber FRP is an electrical insulator. A typical pultruded profile has a lengthwise dielectric strength of about 35 kV/in (about 1.4 kV/mm, ASTM D149). That is why FRP is used for cable tray, ladders and platforms near live equipment. Surface dirt and moisture can lower surface resistance, and carbon-fiber composites conduct. So FRP is not a replacement for electrical safety rules.
Why is glass FRP non-conductive?
Glass fibers and cured polyester, vinyl ester or epoxy resins are all electrical insulators. Steel and aluminum conduct. That is why FRP is chosen for cable tray, ladders, electrical safety barriers and substation platforms.
What do the numbers look like?
| Property | Typical value | Test method |
|---|---|---|
| Dielectric strength, lengthwise | About 35 kV/in (about 1.4 kV/mm) | ASTM D149 |
| Steel, for comparison | Conductor (no dielectric strength) | - |
These figures come from one manufacturer's published data for standard pultruded shapes. Values differ by product, so always ask for the data of the actual product.
What can make FRP conduct?
- Surface contamination: salt, dust, conductive dust or water films can create a surface leakage path.
- Carbon fiber or conductive fillers: carbon-fiber composites and carbon-veil liners conduct.
- Metal parts: fasteners, inserts and handrail fittings conduct even when the profile does not.
- Damage: cracks that take up water reduce insulation.
Is FRP a safe insulator for live work?
Not on its own. Non-conductive structures reduce shock and arcing risk, but work near live parts still has to follow your site electrical safety rules. Tools for live work, such as insulated ladders, must be tested and rated to their own standards.
Does FRP build up static?
It can. Insulating surfaces can build static charge, which matters in flammable atmospheres and where powder is handled. In those cases, specify a conductive (for example carbon-veil) inner surface or a grounding grid.
Insulating vs antistatic: two different needs
Most FRP is chosen because it does not conduct. But in a few places the need is the opposite: the surface must let static charge drain away. That is common on walkways in areas with flammable gases, vapors or dusts.
Insulating vs antistatic FRP
| Need | Typical FRP choice | Published example |
|---|---|---|
| Electrical insulation near live parts | Standard glass FRP, kept clean and dry | Dielectric data from the product maker for the actual part |
| Static dissipation in hazardous areas | Conductive or dissipative grating made with carbon or graphite additives | A European grating manufacturer lists a leakage resistance of 10⁶–10⁸ Ω for its conductive grating |
IEC TS 60079-32-1 is the international guidance on electrostatic hazards. It focuses on bonding and grounding conductive items. It does not give a single resistance value that every grating must meet, so the site’s hazardous area study sets the requirement.
Grounding still matters
A non-conductive tray or grating does not need grounding as a structure, but metal parts in it can. In the US, NEC 392.60 sets grounding and bonding rules for metal cable tray, and an FRP tray cannot act as a grounding path. Run a separate grounding conductor where the design needs one. Metal fasteners, handrail fittings and embedded plates in an FRP structure may also need bonding under the site’s rules.
Keeping FRP insulating in service
- Keep the surface clean. Dirt, salt and carbon dust on a wet surface can create a leakage path.
- Watch for UV damage. Exposed glass fibers hold water. Re-seal weathered surfaces; see UV degradation.
- Do not rely on the material alone for live work. Rated tools and barriers follow their own standards; see FRP telescopic barriers.
If your project needs a specific dielectric strength or surface resistance, state the test method and value in the inquiry. We confirm what can be tested for that order.
For walkways in hazardous areas, the site’s hazardous area classification sets whether antistatic grating is needed. Tell us the zone and the requirement with the inquiry.
How FIBROVX can help
Tell us the voltage environment and the product you need (grating, cable tray, ladder, platform), and we will send the electrical data for that product. Request a quote. CIF by default, FOB on request.
Common mistakes
- Treating FRP as a PPE replacement: follow electrical safety rules.
- Using metal fasteners carelessly: they can bridge an insulation gap.
- Ignoring static in ATEX zones: specify conductive grades where needed.
- Assuming every composite is non-conductive: carbon fiber conducts.
Key terms
- Dielectric strength: the voltage per thickness a material can stand before breakdown.
- Surface resistivity: resistance to current along a surface.
- ASTM D149: test method for dielectric breakdown voltage.
- ATEX zone: an area classified for explosive atmospheres.
FAQ
Is fiberglass grating non-conductive? Yes. Glass FRP grating is an electrical insulator, but keep it clean and use non-conductive fasteners where the design depends on insulation.
Is carbon fiber non-conductive? No. Carbon fiber conducts electricity.
Can FRP become conductive when wet? Water and contamination on the surface can create a leakage path, though the laminate itself stays an insulator.
Why is FRP cable tray used in substations? Because it is non-conductive, non-magnetic and corrosion resistant.
Related guides
Sources
- A US pultruder, design specifications (dielectric strength, ASTM D149)
- ASTM D149, Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials: https://www.astm.org/d0149-20.html
- IEC TS 60079-32-1, Explosive atmospheres — Part 32-1: Electrostatic hazards, guidance, https://webstore.iec.ch
- A European grating manufacturer, GRP gratings: conductive and antistatic versions (product information)
- NFPA 70, National Electrical Code, Article 392 Cable Trays, https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70