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de Special 17/2008

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ELECTROINSTALLATION :

Best Practise for Installation of Aluminium Connectors

Hüthig & Pflaum Verlag GmbH & Co.Fachliteratur KGLazarettstraße 4, 80636 München

Electroinstallation

2 de Special

The advantages of aluminium are

increasingly coming to the fore

in power distribution applica-

tions, due to the lower material weight

and the relatively simple handling.

Power utilities tend to install more and

more aluminium cables, for instance

ring mains for urban power supplies.

In principle it is recommended to use

solely high quality aluminium com-

pression cable lugs with tube di-

mensions acc. to DIN 46329 and alumi-

nium connectors with tube dimensions

acc. to DIN 46267 part 2. Products of re-

nowned manufacturers such as Klauke

are made from premium electrolytic

aluminium alloy. These products fea-

ture a constant material thickness,

exact diameter and a correct fit which

ensures simple installation and ab-

solute safety. Standard cross sections

range from 10 mm2 up to 500 mm2.

Special sized cross sections are available

up to 1000 mm2, for instance for sub-

sea cables with high transmission capa-

cities.

Aluminium compression cable lugs

feature a barrier design. (acc. to DIN

46239) which allows installation on oil

impregnated, paper insulated cables

and consequently provides a firm

water/oil block.

Aluminium conductors at a glance :

Aluminium conductors are available in

four different types (picture 2) which in

some cases require special installation

procedures. These are

• re = solid round conductors

• se = solid sector conductors

• rm = round stranded conductors

• sm = sector stranded conductors

These abbreviations can be found on

aluminium compression cable lugs to

make sure the correct cable lug is used

with the appropriate aluminium

conductor. (Picture 3).

All markings on aluminium com-

pression cable lugs are in conformity

with those on copper cable lugs and

indicate the manufacturer, dimensions

and type of product. For example

marking “KL 18 10-70 /rm/sm 95 re/se”

denotes:

• KL: manufacturer (in this case

Klauke)

• 18: die code

Installation

of com-

pression cable

lugs and connectors

for aluminium conductors is

very different from installation of

copper conductors. Failure of vital

installation procedures can lead to a severe

lack of safety.

Material properties of aluminium cable are very different from those

of copper. For safe electrical connections, solely compression cable

lugs or connectors manufactured from aluminium are to be used. In

addition due to certain specific material properties, the installation

procedure has to be carefully observed.

Best Practise for Installation of Aluminium ConnectorsAluminium compression cable lugs and connectors according to DIN.

AT A GLANCE

In the worst case an incorrectly in-stalled aluminium cable lug can resultin a serious fire. In this article we giverecommendations for a professionalinstallation.

Source: Klauke

Picture 2: Different types of

aluminium conductorsSourc

e: K

lauke

Picture 3: Markings on the

cable lugs indicate manu-

facturer, bolt size, cross

section and cable assignment.

Sourc

e: K

lauke

re = solid round conductors

se = solid sector conductors

rm = round stranded conductors

sm = sector stranded conductors

Picture 1:

The barrier design

with oil stop prevents leakage

of oil of the paper insulated

conductor.

Sourc

e: K

lauke

Electroinstallation

de Special 3

• 10: metric bolt size (bolt M 10)

• 70: nominal cross section of

conductor in mm2

• rm/sm: for round stranded and

sector stranded conductors

• 95: nominal cross section of

conductor in mm2

• re/se: for solid round conductors and

solid sector conductors

Important: The nominal cross sections

of se and re conductors are always

one cross section size above the cross

sections of sm and rm conductors. This

is due to solid conductors having a

smaller diameter than their stranded

equivalent.

Special attention should be given to

the die code: For a professional in-

stallation the crimping dies of the

appropriate tool must be matched with

the code of the cable lugs. (Pictures 3

and 4). Die codes on crimping dies are

mirror-inverted – after the crimping

operation the die code is clearly visible

for quality control and documentation.

For a professional installation hexa-

gonal crimping dies (acc. to DIN 48083

part 4) are recommended. The visible

signs of a correctly crimped lug are the

same for copper connectors as they are

for Aluminium: In order to achieve

a professional installation – with no

over or under crimping – the use of

the appropriate tool is essential. An

incorrect installation can result in in-

creased joint resistance and even in

fire. (Picture 5). To avoid such con-

sequences Klauke recommends to use

the same manufacturers tool as the lug

or connector. This ensures a matched

system. For instance the specific dies for

aluminium have a crimping ‘bite’ width

of 7 mm, which is 2 mm wider than for

copper lugs and connectors (Picture 6).

The reason for this is that wider com-

pression areas result in better conduc-

tivity and therefore compensate for the

poorer electrical properties of Alu-

minium. In order to determine the

different dies required Klauke manu-

facture the Aluminium dies in silver and

the Copper dies in a yellow gold colour.

Compound for Aluminium Connectors

Cable lugs and connectors for alu-

minium are supplied with a special

compound within the barrel (picture

7a). During crimping, this compound

destroys the non-conductive oxide

layer on the aluminium in the crimping

area, increases the contact properties

and ensures the correct electrical

connection. In addition the compound

prevents admission of oxygen and

consequently avoids any further oxi-

dation (Picture 7b). To maintain the

functional properties, brand-name

cable lugs are sealed with a plastic plug

to prevent the compound from drying-

out and leaking. (Picture 8).

Compounds for aluminium con-

nectors contain additives such as

corundum, a material similar to sand,

which exhibits high resistance and

hardness, temperature stabilising pro-

perties and extreme wear and cor-

rosion resistance. A grinding effect is

generated during crimping which

cracks the hard oxide layer on the

cable. In addition the compound aids

Picture 4: Imprint of die code “18” on the cable lug (left) indicates the

crimping die used. Completed crimp (right) with marking “18” on the

cable lug refers to the correct crimping die.

Sourc

e: K

lauke

Picture 5: Over compression (left) is the result of a crimping die which is too small, whilst under compression

(middle) is caused by the use of a crimping die which is too large. The picture on the right shows a correct crimp

using an appropriate crimping die.

Sourc

e: K

lauke

MORE INFORMATION

Book on this issueSchmolke, Herbert: Selection and designof cables and conductors 2007.2, revisedand extended edition. 120 pages, paper-back, with CD Rom, 18€, ISBN 978-3-8101-0263-8, www.de-online.info/ shop/fachbuecher/schmolke_kabel.html

Contribution on this issuehttp://www.de-online.info/archiv/2008/01-02/index.php?Page=elektroinstallation04.html• Which cable lug for which appli-

cation?, “de” 1-2/2008, S.33 http://www.de-online.info/archiv/2008/08/index.php?Page=elektroinstallation02.html• Cable lugs for special applications,

“de” 8/2008, S.27

Electroinstallation

the dynamic friction between the

conductor and sleeve, which prevents

jamming of materials and helps to

provide a clean contact surface. When

used on stranded conductors, the

compound is distributed between the

individual wires during the crimping

process and seals them against oxygen

and moisture ingress.

It is also important to know that

aluminium crimp connections installed

using compound perform much better

when subjected to high current loads

than those without compound. To

guarantee a safe connection, at high or

low loads, Klauke recommends com-

pression cable lugs and connectors with

compound.

Installation of aluminium compression cable lugs and connectors

In order to accommodate the special

characteristics of Aluminium material,

the following five installation steps are

essential:

• Remove insulaltion of aluminium

conductor

• Clean the blank conductor ends with

a wire brush to remove an oxid film

and to provide a clean surface

• Insert the conductor into the cable

lug or connector to the recom-

mended length. Some compound

will emerge from the mouth of

the cable lug or connector which is

now hermetically sealed to prevent

further oxidation of the conductor.

• Start the hexagonal crimping ope-

ration with a suitable crimping tool.

Important: Sector shaped conductors

need to be pre-rounded with appro-

priate crimping dies.

• Remove any excess compound

emerging from the lug or connector.

Please note: All DIN compression cable

lugs show markings on the outside of

the barrel for the correct crimp

position, and consequently number of

crimps required. This is dependant on if

you are using narrow or wide crimping

dies (picture 9). ‘Narrow’ crimps

(approx 7 mm) are performed by tools

of at least. Also the correct crimping

direction has to be observed – always

crimp in the direction of the conductor

(picture 10).

Outlook: Al/Cu Compression cable lugs

A further important technical issue is

the correct method of connecting

aluminium and copper conductors. In

one of our next issues we will report on

aluminium/ copper cable lugs and

connectors.

Lutz Remmel, Anwendungstechnik &

Application Engineering,

Gustav Klauke GmbH

www.klauke.com

Picture 6: The contact surface (bite width) of crimping dies for aluminium cable

lugs (left) are 2 mm wider than their copper equivalent (right).

Sourc

e: K

lauke

7b

Picture 8: Plastic plugs prevent

compound from drying-out and

leaking during storage.

Picture 10: Start the first crimp

at the lug end and progress

towards the conductor to ensure

that compacted material ex-

pands in this direction.all

pic

ture

s – S

ourc

e: K

lauke

Picture 9: Markings on the

cable lugs indicate number

and position of crimps as per

manufacturers recommendation.

Picture 7a: Compounds with

additives like corundum

generate a “grinding effect”.

Picture 7b: The compound seals

the joint and prevents oxidation.

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