DSB Part B: Important Items for Realizing a High Quality Electrical Installation

Part B3: The four important choices related to the electrical installation Choice No. 2: The cables

Identification of ConductorsAlphanumeric Color Identification DSB’s advice

AC Conductor Terminal

Line 1 L1 Black

NoneLine 2 L2 BrownLine 3 L3 GrayNeutral N Blue*

DC Conductor TerminalPositive L+ None RedNegative L- None Black

Protective Conductor Terminal PE Green/Yellow

NonePEN Conductor Terminal PEN GN/YE/BU*

Protective BondingConductor Terminal

Unspecified PB Green/YellowEarthed PBE

Unearthed PBUFunctional Earthing Conductor Terminal**

FE None Green/Yellow

*Light blue **For System Earth Terminals Refer to IEC 60445 (2010-08)

Part B3: The four important choices related to the electrical installation Choice No. 3: The cable glands

Guidance table for selection of cable glands related to basic cable type:

Basic cable typeCircuit Type

Normal ”run through”type gland

Screen type glandExe “run through”

type gland*Exd gland

Copper braided (Realizingthe maintenance-free PE

system)

Power **Only for “real” Exd

cable entriesInstrument

Steel wire braidedPower

Only for “real” Exdcable entries

Instrument

Un-braided cablePower

Only for “real” Exdcable entries

Instrument

To be used Maybe used Not to be used*Some owners use this type as a standard also for non-Ex equipment

**Not accepted by DSB when copper braiding is used for earthing of equipment

Part B3: The four important choices related to the electrical installation Choice No. 3: The cable glands

Type of enclosure Type of glandPlastic enclosures (relevant for field cables) Plastic for size below M32

Plastic enclosures, reinforced with metal gland plate forsupply of large supply- and multi-core cables

Brass

Metal enclosures (except aluminium) Brass/stainless steelAluminium enclosures Stainless steel/nickel plated brassOnly sea water resistant aluminium shall be usedPlastic glands shall not be used for armoured cables

For cable glands for explosion protected equipment, see IEC 61892-7Shroud and similar should not be used on cable glands

Refer to IEC 61892-6 (2007):5.6 table 2

Photo left: Remove gland plates, - this will reduce the possibility for earth faults! When “run through” type metal glands are used in a non-metallic enclosure, they will not be looked upon as any exposed conductive part according to DSB’s decision.

This will make the installation (and maintenance) work easier!

Part B3: The four important choices related to the electrical installation Choice No. 3: The cable glands: Cable entry, gland type and cable type

Guidance table for selection of cable glands in non-ex enclosures:

Photo right: Misuseof EXd glands! Exd glands should not have been usedin this case…

Cable entry(enclosure):

Cable gland: Cable basicType:Plastic Metal

Materia

l

Size

Type

Normal Normal Braided

Un-

braided

Plastic

<M32

Norm

al

Metal

Allsizes

Norm

al

Part B3: The four important choices related to the electricalinstallation

Choice No. 3: The cable glands

Cable entry type: Guidance table for selection of cable glands in explosion protected enclosures:

Marking onSignboard:

CableEntry:

Exd ExdExe ExeExde ExeExdes Exe

Photo left: Correct: Stuffing (“run through”) type glands have been used in this thin-plate stainless steel enclosure

To be used Maybe used Not to be used

Cable entry(enclosure):

Cable gland: Cable basicTypePlastic Metal

Material:

Size:

Type:

Normal Exe Normal Exe Exd Exde*

Braided:

Un-

braided:

Plastic

<M32

ExiExe

Metal

All sizes

ExiExe

Exd

Above: A typical mistake:Exd glands

should notbe usedIn Exe entries!

*May only be used for limited volumes (< 2 litre) in Exd enclosures

Part B3: The four important choices related to the electrical installation Choice No. 4: The termination methods

To be used Maybe used Not to be used

Method 1 is the preferable termination method to use:

+ Direct termination of the full cross- section of the braiding to earth bus-bar (If the cross-section is insufficient, an earth conductor

in the cable should be considered.

+ Simple- and low cost cable penetration

+ Accepted by DSB for realizing the “maintenance-free PE system”

+ The possible copper braiding is used for PE- you save an earth conductor in the cable!

+ Very easy to install

IMPORTANT: Method 1 is the basicterminationmethod recommended for general use!

Part B3: The four important choices related to the electrical installation Choice No. 4: The termination methods

Method 1: Stuffing type (”Runthrough” type)

Method 2: “Screen termination”type

Method 3: Exd type (Explosionproof)

+ Available as Exe + Intended for Exd cable entries (should not be used in other cases)+ Available as nylon type

+ Gives direct and electrically the best termination of the cable’s braiding

+ May be used for ending PE braiding in fieldinstrument equipment (“final sub-circuit”)

+ Accepted by DSB for realizing the ‘maintenance-free PE system’+ The possible copper braiding is used for PE – you save an earth conductor!+ Very easy to install+ Low cost

– Gives 4 joints with different metal surfaces when terminating the braiding– Gives ‘serial earth’ according to IEC

– More a mechanical assembly than a good, electrical connection– Possibility for corrosion problems between different metal surfaces

– Not easy to install– Medium cost– The glands shall be firmly attached

– Complicated to install– High cost (certified)– The glands shall be firmly attached

Part B4: Protective earth The maintenance-free protective earth system

Part B6: Arrangement of earth bus-bar (DB)

A very unpractical location of the earth bar... Not according to IEC requirements

Part B6:Arrangement ofearth bus-bar(MCC)

Install the complete cable right up to the level of the actual starter, and then terminate the braiding and/or earth conductor to the vertical sub earth bar at this level!

At the photos below all the copper braidings have been terminated atthe lower part of the vertical bar. (And, the upper part has not been used at all…) This will make trouble shooting and modification work more difficult!

Part B6: Arrangement of earth bus-bars

PE-busbar is located behind the in- and outgoing cables. The access PE- and IE-bus-bar and earthto the earth bar and its terminals is blocked! Connections nicely arranged

inside the enclosure!

Part B7: Colour-coding in different earthing systems

Protective earth (PE) bus-bars are to be colour-coded green/yellow and/or with the letters PE. Instrument earth (IE) bus-bars should be colour-coded green/yellow with additional red marking and/or with the letters IE. Intrinsically safe earth (IS) bus-bars should be colour-coded green/yellow with additional light blue marking and/or with the letters IS.

Refer to NORSOK standard Rev. 3 item 12.5.3.

PE: IE: IS:

Yellow / Green Yellow / Green/ Red Yellow / Green/ Light blue

Part B8: Separation of circuits Practical advices

Avoid terminating wires and cables with diferent voltage to the same terminal block – or at least not to the same section of a terminal block

Keep components with different voltage in separate sections on a mounting plate in a cabinet

Take EMC- requirements into consideration

Intrinsically safe circuits need special attention! Refer to IEC 61832-7 (2007):7.9

Part B8: Separation of circuits

Practical advices

Left: Exi barrier and circuit(s) must be sufficiently separated from other circuits.In this case they must be moved to a separate enclosure.

IEC 61892-2 (2012):6.1.2

Left: This minus-bar may not be used as a PE-bar! Only one yellow / green Functional Earth-connection (FE) may be terminated to it!

IEC 61892-2 (2012):6.1.2

Left: Earth conductors to be terminated one by one to PE-bar!

IEC 61892-2 (2012):6.1.2

Part C9: Termination Problems…This may partly be a sub-contractor- and a yard problem. The sub-contractor arranges the cabinet with a too small termination space. The yard specifies the control cables with many spare conductors – to increase the problem. Both of them must proceed to reach a better result than shown at these photos!

Part B7: Instrument- and intrinsically safe earth