PVC vs EPR vs Silicone Rubber for Portable Earthing Cables: What Buyers Should Compare

Portable earthing cable insulation should not be selected by price, color, or the word “rubber” alone.

IEC 61138:2007 specifically covers flexible cables insulated with EPR, PVC, or silicone rubber for portable earthing and short-circuiting equipment. These materials have different temperature limits and cable constructions, but material name alone does not prove flexibility, abrasion resistance, chemical compatibility, or complete assembly performance.

When we review a portable earthing cable inquiry, we first confirm the conductor, cross-section, site temperature, cable length, handling conditions, inspection requirements, environmental exposure, and required test evidence.

The key rule is:

Choose the insulation as part of the finished portable earthing cable design, not as a standalone material specification.

Follow local regulations and your site safety procedure.

Quick Answer: PVC, EPR, and Silicone Rubber Are All IEC 61138 Cable Options

IEC 61138:2007 covers flexible cables with insulation based on:

• Ethylene propylene rubber — EPR
• Polyvinyl chloride — PVC
• Silicone rubber — SiR

The standard also distinguishes between general-purpose and cold-resistant PVC compounds.

For buyers, the basic comparison is:

• PVC can be suitable where temperature conditions are moderate and a proven thermoplastic cable construction fits the project.
• Cold-resistant PVC extends the usable low-temperature range compared with general-purpose PVC.
• EPR is an elastomeric option with a wider low-temperature range under IEC 61138.
• Silicone rubber also covers a wide temperature range and may be useful where low-temperature flexibility or specific finished-cable characteristics are important.

However, no material should be approved from the material name alone.

Buyers should also verify:

• IEC 61138 cable type
• Conductor material
• Cross-section
• Finished cable diameter
• Insulation thickness
• Flexibility
• Environmental conditions
• Inspection visibility
• Cable test evidence
• Complete IEC 61230 assembly evidence

For the wider lead-selection process, see our guide to portable earthing lead cross-section, flexibility, and field handling.

IEC 61138 Is the Key Cable Standard

IEC 61230 is widely used when buyers specify complete portable earthing and short-circuiting equipment.

But when the question is specifically:

What flexible cable construction should be used?

IEC 61138 is the more direct cable standard.

IEC 61138:2007 is titled:

Cables for portable earthing and short-circuiting equipment

It covers flexible cables intended exclusively for this application and includes requirements for:

• Conductor construction
• Conductor resistance
• Insulation compounds
• Insulation thickness
• Finished cable diameter
• Cable testing
• Flexibility
• Marking
• Defined cable types

The standard also added silicone rubber to its scope and introduced a normative clashing-test annex in the 2007 edition.

This makes IEC 61138 more useful than a generic statement such as:

Flexible grounding cable with rubber jacket.

Portable Earthing Cable Does Not Have a Normal Rated Voltage

This is one of the most important technical points.

IEC 61138 states that no rated voltage is assigned to these cables because they are intended exclusively for portable earthing and short-circuiting equipment. (webstore.iec.ch)

Therefore, buyers should not compare these insulation materials by asking:

Which insulation gives the highest operating voltage?

Statements such as:

Silicone is better for high-voltage grounding because it has higher insulation performance.

are too simplistic.

The cable insulation supports the finished cable’s:

• Mechanical protection
• Environmental protection
• Flexibility
• Inspection
• Handling
• Defined cable construction

The portable earthing assembly itself still has to meet the required short-circuit duty and equipment requirements.

Our copper grounding wire product page also explains this practical distinction: the outer covering supports protection and inspection, but it should not be treated as the worker’s primary electrical insulating barrier.

PVC: General-Purpose and Cold-Resistant Are Different

A buyer should not specify only:

PVC portable grounding cable.

IEC 61138 includes two different PVC insulation paths:

• PVC/ST 5 — general-purpose PVC
• PVC/ST 11 — cold-resistant PVC

Their guide temperature limits are different.

This means “PVC” is not a complete IEC 61138 specification.

Buyers should ask:

• Which PVC grade is proposed?
• What IEC 61138 cable designation applies?
• What is the declared temperature range?
• What is the finished cable diameter?
• What flexibility evidence is available?
• Is the construction transparent or opaque?
• What environmental limitations apply?

General-purpose PVC can be a practical option where the specified temperature and handling conditions fit the product.

Cold-resistant PVC should be identified separately rather than described only as “better PVC.”

EPR: Where Elastomeric Cable Construction Matters

IEC 61138 defines an elastomeric insulation compound based on cross-linked EPR or similar EPM/EPDM materials.

EPR is worth evaluating where buyers need:

• Wide low-temperature capability
• Flexible elastomeric cable construction
• Repeated portable handling
• Indoor and outdoor use within the cable’s declared limits

But avoid statements such as:

EPR is always the most abrasion-resistant.

or:

EPR is always best for oil.

These characteristics depend on the actual compound and finished cable construction.

A better RFQ asks the supplier to declare:

• EPR cable designation
• Insulation compound
• Insulation thickness
• Overall diameter
• Temperature range
• Flexibility-test evidence
• Environmental limitations

Silicone Rubber: Added to IEC 61138 for Portable Earthing Cable

The 2007 edition of IEC 61138 expanded the standard to include cross-linked silicone rubber insulation.

Silicone rubber may be worth evaluating where the project values characteristics such as:

• Wide temperature range
• Low-temperature cable handling
• Flexible portable construction
• Transparent insulation where offered
• Frequent cable movement

However:

Silicone does not automatically mean mechanically stronger.

Abrasion, tearing, cutting, repeated dragging, and other mechanical conditions should be checked from the actual finished-cable data.

Do not approve a silicone cable simply because the material has a strong temperature reputation.

Ask for the IEC 61138 cable construction and the actual test evidence.

IEC 61138 Temperature Comparison

IEC 61138 gives the following guide temperature limits for indoor and outdoor use:

This table immediately shows why several common assumptions are wrong.

For example:

Silicone is the only option for −40°C.

is not correct under this guide, because EPR is also listed down to −40°C.

Likewise:

All PVC is suitable down to −25°C.

is not correct, because PVC/ST 5 and cold-resistant PVC/ST 11 have different limits.

These IEC values should also not be copied onto every generic commercial PVC, EPR, or silicone cable. The supplier should prove that the offered cable matches the relevant IEC 61138 construction.

PVC vs EPR vs Silicone Rubber: Buyer Comparison

The most important conclusion is:

Material family is a selection starting point, not proof of finished-cable performance.

Transparent vs Opaque Insulation: Why Inspection Matters

Portable earthing cables are repeatedly:

• Carried
• Uncoiled
• Positioned
• Moved
• Recoiled
• Transported
• Stored

This makes inspection important.

Transparent cable constructions can help users observe some internal conditions more easily, depending on the design.

Buyers may value visibility of:

• Conductor strands
• Discoloration
• Contamination
• Local damage
• Signs of overheating
• Changes near terminations

However, transparency should not be confused with IEC compliance.

A cable is not automatically IEC 61138 compliant because it has a clear jacket.

Likewise, an opaque cable is not automatically unsuitable.

Specify transparency where it supports your inspection program, then separately verify the cable standard and performance.

Flexibility Should Be Verified on the Finished Cable

Marketing descriptions often say:

Super flexible grounding cable.

That is not enough.

IEC 61138 addresses the completed cable construction and includes cable testing related to flexibility.

Finished flexibility depends on more than insulation material.

It also depends on:

• Conductor strand construction
• Wire diameter
• Cross-section
• Insulation thickness
• Finished outside diameter
• Cable temperature
• Cable age

Buyers should therefore compare finished cable designs rather than statements such as:

EPR is flexible.

or:

Silicone is softer.

For longer leads, flexibility also interacts with weight, slack, and storage. Our portable earthing cable length guide explains why unnecessary length can increase impedance, weight, movement, and handling difficulty.

Clashing and Short-Circuit Conditions Matter

Portable earthing cable should not be evaluated only under normal manual handling.

During a short-circuit event, the complete assembly can experience severe thermal and electrodynamic forces.

IEC 61138:2007 introduced a normative clashing test for this cable category.

At the complete equipment level, IEC 61230 bases portable earthing and short-circuiting equipment performance on the electrothermal and electrodynamic effects of short-circuit current. Its withstand capability is expressed through rated current, rated time, and peak factor.

Therefore buyers should review two evidence levels:

Cable evidence under IEC 61138

and

Complete assembly evidence under IEC 61230

Do not stop at:

Cable material: silicone.

Abrasion, Oil, Chemicals, UV, and Moisture

Material names can help initial screening, but broad resistance claims should be treated carefully.

Do not assume:

• All EPR is oil resistant
• All PVC has the same UV resistance
• All silicone has poor abrasion resistance
• Any “rubber” cable is chemical resistant

If the site includes:

• Oil
• Hydraulic fluid
• Cleaning agents
• Industrial chemicals
• Coastal exposure
• Strong sunlight
• Gravel
• Steel grating
• Sharp edges
• Repeated dragging

put those conditions in the RFQ.

Then ask the supplier to declare the actual product limits.

A broad statement such as:

Weather-resistant rubber insulation.

is much weaker than product-specific evidence.

Insulation Thickness and Finished Cable Diameter Matter

Changing insulation material can change the complete cable geometry.

IEC 61138 specifies insulation thickness and finished diameter requirements for defined cable constructions and conductor sizes.

This matters because cable OD affects:

• Flexibility
• Weight
• Storage
• Reel size
• Ferrule transition
• Strain relief
• Clamp-side cable entry
• Complete kit packing

For example, IEC 61138 specifies different nominal insulation thicknesses for some SiR constructions compared with EPR/PVC constructions.

Therefore, changing:

PVC → Silicone

is not always a simple material substitution.

Ask for the complete cable datasheet.

IEC 61138 vs IEC 61230: Which Standard Proves What?

These standards should work together rather than compete.

IEC 61230 covers complete portable equipment and bases short-circuit withstand on rated current, rated time, and peak factor.

A good purchasing evidence chain is therefore:

IEC 61138 cable → termination → clamp/cluster → IEC 61230 assembly

The cable may be compliant with its construction standard while the complete kit still needs separate assembly-level evidence.

This is especially important around terminations. See our guide to grounding cable ferrules, lugs, and clamp connections.

What Buyers Should Put in the RFQ

For complete system sourcing, buyers can also review our portable earthing and short-circuit kit range.

What Suppliers Should Return

A useful supplier technical response should identify:

• Conductor material
• Conductor cross-section
• Strand construction
• IEC 61138 cable type
• Insulation material
• PVC grade where applicable
• Nominal insulation thickness
• Finished cable OD
• Cable weight per metre
• Declared temperature range
• Transparency
• Color
• Flexibility-test evidence
• Applicable electrical cable tests
• Clashing-test evidence or applicability
• Cable marking
• Test report reference
• Complete assembly reference
• Technical deviations

This allows buyers to compare finished cable systems rather than material names.

Common Buyer Mistakes

Choosing Insulation Only by Price

Lower material cost does not prove that the cable fits the site’s temperature, handling, and inspection requirements.

Writing Only “PVC Insulation”

IEC 61138 distinguishes general-purpose and cold-resistant PVC.

Assuming Silicone Is Always Best for Cold Weather

EPR also has a −40°C guide lower limit under IEC 61138.

Treating the Insulation Like a Normal Rated-Voltage Power Cable

IEC 61138 does not assign these portable earthing cables a rated voltage.

Assuming All “Rubber Cable” Is EPR

Generic rubber terminology does not prove IEC 61138 EPR construction.

Comparing Materials but Ignoring Finished Cable Flexibility

Strand construction, cross-section, thickness, and OD also matter.

Ignoring Cable Outside Diameter

OD affects handling, terminations, storage, and packing.

Assuming Transparent Insulation Is Mandatory

Transparency can support inspection but does not replace compliance evidence.

Checking IEC 61138 but Ignoring IEC 61230

Cable evidence does not automatically prove the complete portable earthing assembly.

Accepting “IEC Grounding Cable” Without a Standard Number

Ask whether the supplier means IEC 61138 cable evidence, IEC 61230 assembly evidence, or both.

How We Review Portable Earthing Cable Insulation

When we review a cable specification, we do not begin with PVC, EPR, or silicone.

We Confirm the Required Assembly

We first review the application, fault duty, and complete portable earthing configuration.

We Confirm the Conductor

We check conductor material, cross-section, strand construction, and cable length.

We Review the Site Temperature

The minimum and maximum temperature help screen the available IEC 61138 cable types.

We Compare Insulation Options

We review PVC, EPR, or SiR according to the actual operating environment.

We Check the Exact Cable Construction

Insulation thickness, overall diameter, transparency, and cable designation are confirmed.

We Review Handling Requirements

We consider repeated coiling, transport, lead length, and field use.

We Review Environmental Exposure

Oil, chemicals, UV, moisture, abrasion, and contamination are identified before approval.

We Review Cable Test Evidence

We compare the finished cable with the applicable IEC 61138 requirements.

We Connect the Cable to the Complete Assembly

Ferrules, clamps, clusters, and assembly ratings are reviewed separately under the complete equipment specification.

We Declare Deviations Before Production

A different insulation compound, cable OD, or cable construction should not be introduced as an unreported substitution.

FAQ

Does IEC 61138 allow PVC, EPR, and silicone rubber?

Yes. IEC 61138:2007 specifically covers EPR, PVC, and silicone rubber insulated flexible cables for portable earthing and short-circuiting equipment.

Does a portable earthing cable have a rated voltage?

No rated voltage is assigned under IEC 61138 because the cables are exclusively intended for portable earthing and short-circuiting equipment.

What is the IEC 61138 temperature range for EPR?

The guide gives EPR a range of −40°C to +70°C.

What is the difference between PVC/ST 5 and PVC/ST 11?

PVC/ST 5 is the general-purpose PVC path, while PVC/ST 11 is the cold-resistant PVC path. Their IEC guide temperature ranges differ.

Is silicone always better than PVC?

No. Compare temperature, finished-cable flexibility, diameter, inspection needs, site exposure, test evidence, and cost before deciding.

Is transparent insulation required by IEC 61138?

Do not assume that it is. Transparency can support visual inspection, but the buyer should treat it as a product or project requirement and separately confirm standard compliance.

Does IEC 61138 replace IEC 61230?

No. IEC 61138 focuses on the flexible cable. IEC 61230 addresses portable earthing and short-circuiting equipment at the device and assembly level.

What documents should buyers request?

Depending on the project, request the cable datasheet, IEC 61138 cable identification and test evidence, conductor data, insulation details, temperature limits, dimensional data, and IEC 61230 complete assembly evidence.

Practical Buyer Summary

Do not choose portable earthing cable insulation from:

PVC is cheaper.
Rubber is stronger.
Silicone is better.

Those statements are too broad.

Instead, confirm:

• IEC 61138 requirement
• Conductor material
• Cross-section
• Cable length
• Minimum temperature
• Maximum temperature
• PVC grade where applicable
• EPR or SiR construction
• Flexibility
• Insulation thickness
• Finished cable diameter
• Transparency
• Environmental exposure
• Chemical exposure
• Cable test evidence
• Complete assembly evidence

The most useful distinction is:

IEC 61138 proves the portable earthing cable construction; IEC 61230 addresses the complete portable earthing or short-circuiting equipment.

A strong purchasing process should connect:

Site conditions → IEC 61138 cable type → insulation compound → finished cable construction → cable test evidence → terminations and clamps → IEC 61230 complete assembly

Once those requirements are clear, buyers can compare PVC, EPR, and silicone rubber based on the actual project instead of relying on generic material claims.

For standard and custom portable grounding lead configurations, see our copper grounding wire product page and specify the required conductor, cross-section, length, insulation, temperature range, termination, and documentation package.

Follow local regulations and your site safety procedure.