Portable Earthing Kit Fault-Current Rating: How Buyers Should Read kA, Rated Time, Peak Factor, and Test Evidence

We often receive requests for a “25 kA portable earthing kit.”

Before we confirm a configuration, we need more information.

A kA value alone does not state the required time duty, peak-current basis, lead arrangement, cable lengths, clamp models, terminations, or tested configuration. A cable result also does not automatically prove the rating of the complete portable earthing assembly.

The project engineer should provide the approved short-circuit current, protection clearing time, connection interfaces, and required configuration. The supplier should then show how the proposed equipment matches those inputs and what test evidence supports the declared rating.

Follow local regulations and your site safety procedure.

Quick Answer: Read Current, Time, and Assembly Scope Together

A portable earthing kit fault-current rating should not be read from the kA number alone.

Buyers should confirm:

• Rated current
• Rated time
• Peak-current or peak-factor basis
• Complete lead arrangement
• Cable material and cross-section
• Cable lengths
• Phase and earth clamps
• Ferrules and end fittings
• Common connection point
• Tested configuration
• Standard and report reference
• Product marking and traceability

IEC 61230 expresses the short-circuit withstand capability of portable earthing and short-circuiting equipment through rated current, rated time, and peak factor. The standard does not assign a simple rated voltage to the complete equipment, although installation voltage remains relevant to equipment geometry and insulating components.

For this reason, “33 kV kit” and “25 kA kit” are both incomplete descriptions when used alone.

Why “25 kA Earthing Kit” Is an Incomplete Description

Consider this supplier statement:

Portable earthing kit rated at 25 kA.

It does not explain:

• Whether the rating is for 0.5 seconds, 1 second, 3 seconds, or another duration
• Whether 25 kA is the declared r.m.s. short-time current
• What peak requirement was applied
• Whether the evidence covers one cable or the complete assembly
• Which cable cross-section was tested
• Which cable length was used
• Which phase clamps were tested
• Which earth clamp was tested
• Which ferrules and terminations were used
• Whether the arrangement used separate leads or a cluster point
• Which standard and edition were applied
• Whether the offered product matches the tested product
• Whether the delivered equipment can be traced to the documents

Two products can show the same kA number but have different rated times, cable arrangements, clamp models, test evidence, and technical limitations.

Buyers should therefore compare complete rating statements, not isolated current figures.

What kA Means in a Portable Earthing Rating

kA means kiloampere. In this context, it forms part of the declared short-circuit current rating.

It does not describe:

• The system voltage
• The normal operating current
• The cable cross-section by itself
• The required test duration
• The complete assembly configuration
• Suitability for every installation

The required short-circuit current should come from an approved engineering source, such as:

• System study
• Protection study
• Utility data
• Project design
• Tender specification
• Engineer-approved technical schedule

We do not calculate or guess the project fault current from voltage level alone.

When a buyer provides only “11 kV,” “33 kV,” or “66 kV,” we still need the approved fault-current duty and clearing time before reviewing a portable earthing configuration.

Why Rated Time Must Be Shown with kA

Rated current and rated time should always be read together.

For example:

• 25 kA for 1 second
• 25 kA for 3 seconds

These are not the same rating statement.

The same short-circuit current applied for a longer duration creates a different electrothermal burden on the cable, terminations, clamps, and complete current path.

Buyers should not assume that one current-and-time rating can be converted into another without:

• Engineering approval
• Applicable standard rules
• Supporting calculations where permitted
• Suitable test evidence
• Confirmation that the complete configuration remains covered

The project clearing time should normally come from the approved protection design or another accepted project document.

We recommend writing both values clearly in the RFQ:

Required short-circuit current: ___ kA
Required clearing time: ___ seconds

Do not request only the largest kA number shown in a supplier catalog.

Rated Current, Rated Time, and Peak Factor

IEC 61230 bases equipment performance on the electrodynamic and electrothermal effects that act during a short circuit. This is why current, time, and peak factor form one rating framework rather than three unrelated catalog values.

What Peak Factor Means for Buyers

Short-circuit current creates more than thermal stress.

The initial peak also creates electrodynamic forces on:

• Cables
• Clamps
• Ferrules
• Common connection points
• Branch arrangements
• Mechanical interfaces

Buyers do not need to calculate the peak factor themselves when reviewing a quotation. However, they should confirm whether:

• The project specifies a peak requirement
• The supplier’s test evidence includes a peak-current basis
• The tested assembly matches the offered assembly
• Clamp and termination details are included
• The report clearly states the current and time conditions
• Any alternative rating basis has been declared

A statement such as “tested at 25 kA” is incomplete when the report does not identify the time duty and peak-current conditions.

System Voltage Is Not the Fault-Current Rating

System voltage and short-circuit rating answer different questions.

System voltage helps define:

• Installation environment
• Equipment spacing
• Access arrangement
• Insulating operating components
• Connection position
• Work method
• Site procedure

Fault-current rating helps define the required short-circuit withstand capability of the earthing equipment.

A “33 kV portable earthing kit” may be intended for a 33 kV installation, but the phrase does not tell the buyer the approved short-circuit current or clearing time.

IEC 61230 can apply to portable temporary earthing equipment used on isolated or de-energized AC and DC installations, including low- and high-voltage, overhead, and underground networks. Its rating logic remains based on current, time, and peak factor rather than a single equipment voltage rating.

For a detailed overview, buyers can review our guide to IEC 61230 rating and compliance.

Component Rating vs Complete Assembly Rating

A portable earthing and short-circuiting set may include:

• Flexible copper cables
• Phase clamps
• Earth clamp
• Ferrules
• Cable lugs
• Common cluster point
• Branch connectors
• Adapters
• Insulating operating components

Each component matters.

However, a rating shown for one component should not automatically be presented as the rating of the complete set.

Buyers should ask:

Does this rating apply to the bare cable, the cable with terminations, one clamp, or the complete tested assembly?

Cable evidence

A cable report may confirm conductor construction or cable performance under defined conditions.

It may not prove:

• Clamp performance
• Ferrule integrity
• Common-point strength
• Complete lead arrangement
• Earth-end connection performance

Clamp evidence

A clamp test may support mechanical or electrical performance for a specific model.

It may not prove:

• Cable suitability
• Termination quality
• Complete assembly behavior
• Suitability for another connection geometry

Assembly evidence

Complete assembly evidence should identify the tested arrangement clearly enough for the buyer to compare it with the proposed product.

A high-rated cable does not compensate for an unsuitable clamp, weak ferrule, or unverified connection point.

Our guide to grounding clamp and interface selection explains why clamp geometry and assembly compatibility should be reviewed together.

What Configuration Was Actually Tested?

The title of a test report is not enough.

Buyers should inspect the tested configuration.

A report for a 50 mm² cable with one clamp model does not automatically support a quotation using:

• A different cross-section
• A different clamp
• A longer cable
• A different ferrule
• A different branch arrangement
• A different common connection point

The supplier should explain whether the difference is covered, approved, or submitted as a technical deviation.

Compare the Test Drawing with the Offered Drawing

An assembly drawing is one of the most useful documents in rating verification.

It can show:

• Cable quantity
• Cable cross-section
• Cable lengths
• Phase-to-phase arrangement
• Phase-to-earth arrangement
• Branch lengths
• Cluster point
• Phase clamp models
• Earth clamp model
• Ferrule design
• Adapters
• Identification points

The buyer should compare:

1. Tested drawing
2. Supplier’s quotation drawing
3. Approved production drawing
4. Delivered equipment

These should be technically consistent.

Where the proposed product differs from the tested design, the supplier should identify the change rather than issuing a general statement such as “equivalent configuration.”

Read the Test Report Beyond the Final “PASS”

A useful report should allow the buyer to identify:

• Report number
• Issuing laboratory
• Applicant
• Manufacturer where stated
• Product model
• Assembly description
• Drawing number
• Cable data
• Clamp data
• Test standard
• Test current
• Test duration
• Peak-current basis
• Test date
• Test result
• Observations
• Limitations
• Authorized approval

A final “PASS” statement is useful only when the report clearly explains what passed.

The following statement is weak:

Portable earthing equipment: Pass.

It does not identify the current, duration, configuration, or test scope.

A stronger report connects the conclusion to a defined assembly and controlled test conditions.

Type-Test Evidence vs Delivery Evidence

Different documents answer different questions.

Your design evidence and delivery evidence should support each other.

A type test usually addresses design validation. Routine, batch, production, and delivery records help show whether current production remains connected to the controlled design.

For more detail, see our guide to type-test and routine-test evidence.

Can an Older Type-Test Report Support Current Production?

An older report is not automatically unacceptable.

The more important question is:

Does the current product still match the tested design?

Buyers should ask whether any of the following have changed:

• Cable material
• Cable construction
• Cable cross-section
• Cable supplier
• Clamp model
• Clamp material
• Ferrule design
• Termination method
• Common connecting point
• Fasteners
• Assembly drawing
• Production process
• Standard or project requirement

If the design has changed, the supplier should explain:

• What changed
• Why it changed
• Whether the change is covered by existing evidence
• What additional verification is available
• Whether the buyer must approve the deviation

The date of the report is only one review point. Design continuity and traceability are equally important.

Cable Length and Test-Evidence Scope

Cable length should not be ignored when comparing a tested configuration with an offered configuration.

Buyers should check:

• Length used in the test
• Length offered in the quotation
• Number of leads
• Branch lengths
• Earth-lead length
• Routing arrangement
• Whether the evidence scope addresses the proposed configuration

A buyer should not assume that any cable length is covered because the cable cross-section is the same.

Longer leads can change:

• Assembly impedance
• Handling
• Weight
• Mechanical movement
• Storage
• Routing
• Complete kit layout

The technical proposal should state actual supplied lengths clearly.

Our guide to portable earthing lead selection factors explains why cable cross-section, length, flexibility, terminations, and fault duty should be reviewed together.

Terminations Are Part of the Current Path

Ferrules and end fittings connect the cable to the clamp and common connection point.

Buyers should confirm:

• Ferrule material
• Ferrule size
• Cable preparation method
• Compression or connection method
• Fastener arrangement
• Lug or terminal type
• Connection direction
• Strain control
• Corrosion protection
• Drawing reference
• Test-evidence scope

A report for the conductor alone does not prove the termination.

A report for one ferrule design does not automatically support another.

Our article on ferrule, lug, and clamp connection checks explains why terminations should be reviewed as part of the complete electrical and mechanical path.

Marking and Traceability

The rating stated in the documents should be connected to the physical equipment.

Depending on the project and applicable requirements, useful marking may include:

• Manufacturer
• Model or type
• Rated current
• Rated time
• Conductor cross-section
• Cable length
• Kit ID
• Serial number
• Batch number
• Drawing reference
• Standard reference
• Customer asset number

Portable earthing supplier-evaluation guidance on your site also emphasizes matching model/type, current-and-time rating, conductor cross-section, and traceability information with the supporting certificate and acceptance records.

If the product label shows one rating while the datasheet or test report shows another, the evidence chain is incomplete.

What Buyers Should Request Before Technical Approval

These documents should be reviewed together.

A certificate without a drawing may not explain the tested configuration. A drawing without test evidence may not support the rating. A test report without traceability may not connect clearly to the delivered equipment.

Fault-Current Rating Evidence Red Flags

kA Value Without Rated Time

A current value without a duration is incomplete.

Rated Time Without Clear Current

The buyer cannot identify the complete rating.

“Suitable for 33 kV” Used as Fault-Current Evidence

System voltage does not prove short-circuit withstand capability.

Cable-Only Report Submitted for a Complete Kit

The report may not cover clamps, ferrules, common points, or the complete arrangement.

Tested Clamp Model Differs from the Offered Clamp

The supplier should declare and justify the change.

Test Configuration Is Missing

The buyer cannot tell what was actually tested.

Cable Cross-Section Differs from the Offer

The report may support another product design.

Cable Length Differs Without Explanation

The scope of evidence may be unclear.

Report Shows “PASS” Without Current and Duration

The conclusion cannot be evaluated properly.

Peak Basis Is Missing

The electrodynamic test basis may be unclear.

Product Marking Does Not Match the Report

The delivered equipment cannot be reliably linked to the evidence.

Supplier Cannot Explain the Evidence Type

The buyer should know whether the document is a type test, routine record, batch report, or general declaration.

One Report Is Used for Every Product Model

Different cables, clamps, ferrules, and configurations may not be covered.

Weak Rating Statement vs Better Rating Statement

Weak Rating Statement

Portable earthing kit, 33 kV, 25 kA, IEC standard.

This does not state:

• Rated time
• Peak-current basis
• Cable cross-section
• Cable lengths
• Lead arrangement
• Clamp models
• Terminations
• Tested configuration
• Standard edition
• Report number
• Technical deviations
• Traceability

Better Rating Statement

A stronger technical offer should identify:

• Application
• Required system context
• Rated current
• Rated time
• Peak requirement or test basis
• Cable material
• Cable cross-section
• Actual cable lengths
• Lead arrangement
• Phase clamps
• Earth clamp
• Ferrules and end fittings
• Common connection point
• Assembly drawing
• Applicable standard
• Type-test report reference
• Deviations from the tested design
• Marking and traceability

This is a procurement-content example. It does not replace the project engineer’s specification.

How We Review a Fault-Current Rating Inquiry

When we receive a fault-current rating inquiry, we follow a fixed review process.

We Ask for the Approved Fault Current

We do not determine the required current from voltage level alone.

We Confirm the Required Time Duty

We ask for the project clearing time or approved rated-time requirement.

We Review the Peak Requirement

We check whether the project or tender states a peak-current or peak-factor requirement.

We Identify the Complete Lead Arrangement

We review the number of leads, branch design, phase-to-phase arrangement, earth lead, and common point.

We Match the Cable and Clamps

We check the cable cross-section, lengths, phase clamps, earth clamp, and connection interfaces.

We Review Ferrules and Terminations

We confirm the cable-to-clamp and cable-to-common-point connections.

We Compare the Proposal with Test Evidence

We compare the offered assembly with the tested configuration and drawing.

We Identify Technical Deviations

Any difference in cable, clamp, ferrule, length, or arrangement should be declared.

We Confirm Marking and Traceability

We check how the rating will be shown on the equipment and linked to production records.

We Submit the Evidence Package for Approval

The buyer should receive a clear technical schedule before production.

For tender preparation, see our guide to engineering inputs for portable earthing kit tenders.

FAQ

Is a 25 kA rating complete without a time value?

No. The rated current should be read together with the rated time and relevant peak-current basis.

Is 25 kA for 1 second the same as 25 kA for 3 seconds?

No. These are different rating statements. Buyers should compare the exact engineer-approved current and time requirement.

Does system voltage determine the kit’s fault-current rating?

No. System voltage describes the installation context. The required fault duty should come from an approved system study, protection design, utility requirement, or project specification.

Does a cable test prove the complete kit rating?

Not automatically. The complete kit also includes clamps, ferrules, end fittings, branch connections, and other components. Buyers should check the scope of the test evidence.

What should a type-test report identify?

It should identify the tested product or assembly, drawing, cable, clamps, terminations, current, time, peak basis, applicable standard, result, and report approval.

Can an old test report support a current product?

It may, provided the current product still matches the tested design and the supplier can show design control, production consistency, and traceability.

Is a larger cable cross-section always enough to increase the rating?

No. The complete assembly includes more than the cable. Clamps, ferrules, connections, lengths, and the tested configuration must also be reviewed.

Can one type-test report support several clamp models?

Only when the report scope, standard rules, or supporting technical justification clearly covers those models and the buyer accepts the evidence.

Should the rating be marked on the physical kit?

The required marking depends on the applicable standard and project specification. Buyers should define current, time, model, cross-section, and traceability requirements before production.

Practical Buyer Summary

Do not approve a portable earthing kit from the kA number alone.

Start with the engineer-approved:

• Fault current
• Clearing time
• Peak requirement
• Application
• Connection interfaces
• Lead arrangement

Then verify the supplier’s:

• Rated current
• Rated time
• Peak-current basis
• Cable cross-section
• Cable lengths
• Clamp models
• Ferrules
• End fittings
• Common connection point
• Assembly drawing
• Type-test evidence
• Technical deviations
• Product marking
• Batch or serial traceability

The most important question is not:

How large is the kA number?

The better question is:

Does the declared current-and-time rating apply to the complete configuration we are buying, and can the supplier prove it?

A clear evidence chain should connect:

Engineering duty → tested configuration → offered assembly → production drawing → product marking → delivered equipment

For product sourcing after the required duty has been approved, buyers can review our portable earthing and short-circuiting kits.

Follow local regulations and your site safety procedure.