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Cable screen earthing selector

Find where to earth a screen, drain wire or armour.

AS/NZS 3000Data under review

Reads AS/NZS 3000:2018 and HELUKABEL and LAPP catalogues 2024. Tables checked 27 Sept 2026.

Try a job 5

Each job fills in example values. Replace them with your values.

Inputs

Worked example with the default inputs. The live calculator replaces it when the page loads.

What the screen does
Screen against interference
Screen construction
Foil and braid
This cable needs earthing under Cl 5.4.1
Yes
The screen has double insulation between it and the live conductors, and an overall covering
No
What you are checking
Hum loop or circulating current
The sheath touches a pipe carrying a flammable agent
No

Earthing arrangement

One end, at the origin

Clause
AS/NZS 3000:2018 Cl 5.5.3.2(b)
Reason
Earth the screen at the end where the cable leaves its switchboard or accessory. One earthing point leaves no closed path through the screen. No current then circulates in it, and no hum loop forms.
Continuity required
Yes
Screen construction
Foil and braid
Construction note
Overall foil with a tinned copper braid over it. The catalogue puts this construction against both low-frequency and high-frequency interference. Manufacturer data, not a standard. Source: HELUKABEL Industrial Ethernet Cables, SF/UTP ranges.
Construction source
manufacturer-data

This result is a design aid. Verify it against the current standard.

Calculation steps

  1. Screen roleemc-screen

    AS/NZS 3000:2018 Cl 5.5.3.2(b)

  2. Clause case matcheda screen, armour or sheath on a cable or cord that needs earthing

    AS/NZS 3000:2018 Cl 5.5.3.2(b)

  3. Earthing arrangementResultOne end, at the origin

    AS/NZS 3000:2018 Cl 5.5.3.2(b)

  4. Continuity requiredYes

    AS/NZS 3000:2018 Cl 5.5.4.3

  5. What you are checkinghum-loop
  6. Screen constructionFoil and braid

    HELUKABEL and LAPP catalogues 2024

  7. Acts against, per the catalogueboth

    HELUKABEL and LAPP catalogues 2024

About this calculator

How this is calculated

The tool reads AS/NZS 3000:2018 Clause 5.5.3.2 for where a cable screen, drain wire or armour is earthed. It then states what that choice does to hum loops and touch voltage.

  1. Role. You pick what the metal does, such as an EMC screen.
  2. Clause case. The tool matches your role, your earthing need and your double-insulation answer to a case in Cl 5.5.3.2.
  3. Arrangement. It gives the earthing arrangement for that case. For an EMC screen against hum, this is one end, at the origin.
  4. Continuity. It reads Cl 5.5.4.3 for the continuity the screen needs. The screen and its fittings stay continuous.
  5. Concern. It states the effect on your concern. One earthing point leaves no closed path through the screen, so no hum loop forms.
  6. Construction. It adds the catalogue note for the screen type. This is maker data, not a Standard.
StepTable or clauseWhat it decides
ArrangementAS/NZS 3000 Cl 5.5.3.2Where the screen is earthed
ContinuityCl 5.5.4.3The screen and fittings stay continuous
Construction noteHELUKABEL and LAPP catalogues 2024What the screen type acts against

Worked example

A foil and braid EMC screen with a hum loop concern. The tool gives one end, at the origin, from Cl 5.5.3.2(b). Continuity is required.

Limits

  • The tool gives the safety arrangement of AS/NZS 3000. It does not give an EMC design.
  • No document the tool holds backs earthing both ends for EMC. Check the device maker guide or IEC 61918.
  • The gland advice is an AmpSize recommendation, not a requirement.
  • The tool does not check the current rating of the screen.

See also: Segregation checker, Control panels and PLC wiring and The MEN system.

Questions

Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.

Where is a cable screen earthed?

AS/NZS 3000:2018 Clause 5.5.3.2(b) names the originating end and sets no count of earthing points. Earth a screen, armour or sheath that needs earthing where the cable leaves its switchboard or accessory. The standard names no both-ends arrangement, so the tool gives none.

Does earthing at one end stop a hum loop?

Yes. With one earthing point there is no closed path through the screen, so no current circulates in it and no hum loop forms. Earthing a screen at two points creates that path.

When does a screen not need earthing?

Clause 5.5.3.2(b) gives two exceptions. The first needs double insulation between the screen or braid and the live conductors. It also needs a non-conductive covering over the cable. Every joint and termination must stay clear of live and exposed conductive parts. The second covers any case Clause 5.4.1 leaves out.

Can the screen be the earthing conductor?

Yes, under Clause 5.3.2.2(ii), with one condition from Clause 5.3.2.3(b). Every live conductor that feeds the equipment must run in that same cable. Clause 5.5.4.3 also asks for continuity, and for an impedance that matches a copper earthing conductor.

Where does the screen construction advice come from?

From HELUKABEL and LAPP catalogues. That is manufacturer data, not a standard, and the tool labels it as such. A braid acts mainly against low-frequency interference and a foil against high-frequency interference. The catalogues cover termination hardware. Neither they nor AS/NZS 3000 back a both-ends arrangement.

Clauses and tables this tool reads

Every clause and table, with how each was verified

Tables last checked on 27 Sept 2026.

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