Copper Cable Lugs For Special Applications

Published 03 Sep 2018

Copper Cable Lugs For Special Applications

Copper Cable Lugs For Special Applications

  • uploaded by Chris Dodds - Thorne & Derrick Sales & Marketing Manager

Thorne & Derrick International, based in the UK, are leading suppliers of cable crimp lugs and associated crimping tools for Low, Medium & High Voltage Cables and Power Systems – this series of articles by Klauke discusses the theory and practise of installing compression type cable lugs and connectors.

Klauke cable lugs and crimping tools are used by Jointers, Linesmen, Panel Builders and Electrical Engineers to install underground cables and overhead line conductors on power, transmission and distribution networks including LV MV & HV systems, 11kV-33kV.

➡ Download 2018 Klauke Cable Lugs catalogue and see the complete range of tools for cutting and crimping cables.

In this Article we cover the following:

  • Crimping cables according to Class 5 & Class 6 DIN 57295 using Klauke “F” cable lugs
  • Tube diameter is matched to the conductor size to guarantee a professional cable crimp
  • Cable lugs for switch cabinets with special narrow palm cable lugs
  • Crimping copper cables and conductors using stainless steel and nickel cable lugs

A well known problem for every electrician or cable jointer is trying to insert a stranded or fine stranded conductor into the cable lug or cable splice and some wires cannot be inserted. To avoid this problem renowned manufacturers offer specialist application connectors and cable lugs for the jointing and termination of LV MV HV cables.

Cable Lugs, Strandings & Conductors

With these specialist application cable lugs all types of cables can be used – the design and construction of the cable lug to be selected is determined by the cable stranding and conductor type. The cable conductor characteristics of cable types are as classified in the DIN Standard 57295.

Class 1 is a solid/round conductor providing both the smallest diameter and largest cross-sectional area (CSA in sqmm) – this is the simplest conductor but mechanically weak with solid conductors prone to breakage after several bending cycles. The cable conductors are categorised into Classes based on the total number of strands per conductor – the higher the Class, the more strands in the conductor:

  • Class 1 Round single / solid conductors
  • Class 2 Round multi-stranded conductors – typically 7 or 19 strands
  • Class 5 Fine stranded conductors (Multi-stranded general flexible use)
  • Class 6 Fine stranded conductors (Extra multi-stranded dynamic use)

DIN 57295: DIN VDE 0295:1980-09; VDE 0295:1980-09
Conductors of Cables & Flexible Cords For Power Installation (VDE Specification)

DIN VDE 57295

Conductor types acc. to DIN VDE 57295: round solid, round stranded, fine stranded, compacted

Cable Lugs For Fine & Very Fine Stranded Conductors

The above mentioned problem of spliced cables per Class 5 and Class 6 according to DIN 57295 is being avoided when using Klauke “F” type series cable lugs. These lugs are designed for processing larger cross section conductors in voltage applications up to the short circuit tested rating of the cable lug.

Compared with standard tubular cable lugs the “F type” lugs have a larger tube diameter – the cable lugs have a flared entry which eases cable location into the barrel of the lug.

Cable Lugs

Unprofessional and individually matched cable lugs can create serious safety defects in electrical installations.

The advantages are obvious – “F type” cable lugs ensure an easy and safe insertion of the conductor, the unravelling of the cable strands is avoided and the complete conductor fits into the cable lug prior to compression using appropriate crimping tools and die sets.

Cable Lugs F-Type

Cable lugs “F type” for fine stranded conductors for easy insertion with no splicing

This is also a safety-related issue – a reduction of the cross section area of the cable conductor caused by not inserting all the strands is being avoided and the complete cross section of the cable is maintained. Markings on the F-type cable lug barrel provide information of the product, e.g. manufacturer, dimension and design.

Marking “KL 12 150 F” indicates:

  • KL: Manufacturer Klauke
  • 12: Metric bolt size for connecting bolt: size M12
  • 150: Cross section of conductor in sqmm
  • F: Tubular cable lug design and construction

For professional crimping of F-type cable lugs the indent or quad point crimping method is recommended with the appropriate crimping tools and the correct indent profile.

F-type cable lug shows professional indent crimp

F-type cable lug shows professional indent crimp

To avoid over or under compression the correct tooling is a pre-requisite. An incorrect crimping connection can result in increased joint resistance leading to an increase in temperatures and in the worst case in fire.

Klauke recommends use of their own crimping tools to achieve and guarantee professional crimps according to VDE standards. In addition to “F-type” cable lugs some manufacturers offer appropriate butt-connectors for splicing, extension and repair of cable conductors.

They also feature a flared entry and larger tube dimensions. A central restriction insures uniform insertion of the cable ends, and insure the crimping recommendations for F-type lugs are adhered to.

“F-type” cable lugs and butt connectors conform to the normative requirements of the EN 13600 standard and are manufactured from electrolytic copper for excellent conductivity.

Klauke Indent Crimp

A cross sectional view of an indent crimp (with manufacturers recommended tool) shows the even arrangement of conductor in the lug

For corrosion protection the cable lugs are available tin plated from cross sections ranging between 10sqmm up to 300sqmm. In addition to the normal design “F-type” cable lugs are also available as 45° resp. 90° angled versions as well as inspection holes to check whether the conductor is fully inserted prior to crimping-up the lug using the cable tool.

As with all other connections these products are subject to test standard IEC 1238 Part 1, which guarantees a safe electrical and mechanical connection has been achieved. Cable lugs manufactured by Klauke are subject to a special annealing process to help relieve material stresses and hardness.

This reduces the chance of material fracture and is an additional safety feature. The quality of cable lugs can often be recognised by visual characteristics. A burr free lug, a flat palm and a cleanly machined end are indicative of a high quality product.

Note: IEC 61238-1:1993 Is Now Withdrawn. Compression & Mechanical Connectors For Power Cables With Ccpper Or Aluminium Conductors – Part 1. Contact T&D.

Cable Lugs For Solid Conductors

For processing and crimping solid conductors (Class 1 DIN VDE 57295) the use of tubular cable lugs “E” type is recommended which are also manufactured from electrolytic tin plated copper. Their tube diameter is matched to the conductor size to guarantee a professional cable crimp.

Professional Crimp

Professional crimp on a solid conductor with matched tube dimension

Application is in all areas where solid conductors are being mostly used, e.g. manufacture of switchgear, transformers and engines.

A hexagonal indent crimping is being recommended – again it has to be observed that both cable lugs and crimping tools come from the same manufacturer.

Cable lugs for solid conductors can be recognized by their smaller tube diameter and the marking “E”. For example: KL 10 50 E.

Cross sections usually range from 6sqmm up to 50sqmm. The range is being completed by butt-, T- and cross connectors having the appropriate internal tube diameters.

Cable Lugs For Switch Cabinets

In many cases working area in switch cabinets is very tight and connecting conductors to high-power switchgears can be a problem In case of larger cross sections standard cable lugs do not fit into the compact connecting terminal.

Special Cable Lugs

Special cable lugs for switch cabinets (type SG) for safe connection also of conductors

For such applications many manufacturers have designed special narrow palm cable lugs (Klauke SG cable lugs) which fit comfortably.

Standard Cable Lugs

Direct comparison of standard cable lugs (left) and cable lugs with narrow palm for switch cabinets

The narrow palm lug is also thicker than standard cable lugs ensuring the same amount of electrolytic copper has been used.

Despite a narrower palm no performance is lost. Thus these cable lugs therefore comply with a professional connection for stranded conductors according to DIN- VDE Class 2 as typically used in switch cabinets.

A hexagonal or indent crimp is recommended – conductor cross sections range from 35sqmm up to 300sqmm. The hole dimensions comply with industry sizes of connecting terminals, e.g. 6, 8, 10, 12 and 16mm.

Stainless Steel Cable Lug

Professional crimp on stainless steel cable lug for application in ambient temperatures of up to 400°C

Versions with inspection holes are also available – it is dangerous and incorrect to file the palm of a normal cable lug to the size of the connecting terminal. Such manipulation can result in increased temperatures and fire in the worst case.

SG Cable Lugs

Shows the thicker palm of SG cable lugs for switch cabinets, using the same amount of
 copper as used in a standard cable lug.

Stainless steel cable lugs

for aggressive environments

Especially for adverse environments and for crimping copper conductors stainless steel and nickel tubular cable lugs have been designed. Stainless steel cable lugs are particularly acid and corrosion resistant and are typically used in chemical industries in areas exposed to sea water i.e. the earthing of masts on sailing yachts.

An additional benefit of these cable lugs is the temperature resistance. Consequently these lugs can be used in ambient temperatures up to 400°C.

At higher temperatures of up to 650°C – common in the construction of furnaces – nickel cable lugs represent the best solution. Both stainless steel and nickel cable lugs can be used for all common cable types.

A correctly crimped stainless steel cable lug used for applications where the environment can reach 400º C

Cross section ranges from 0.5sqmm up to 95sqmm. Generally an indent crimp is recommended. The same applies for stainless steel and nickel butt connectors with barrier.

Further Reading

Review other Blogs in this series of articles about Cable Lugs, Crimping Cables & Tools:

Cable Lugs – Crimping Applications & Standards

Indent Crimping Of Cables – Benefits & Limitations

Cable Lugs & Crimps – Hexagonal v Indent Methods of Crimping

Cable Lugs & Crimping Using The Hexagonal Crimp Method

DIN Standard – Crimping & Compressing Aluminium Cable Lugs & Connectors

Copper & Aluminium – Crimping CU-AL Cables

Electrically Driven Crimping Tools For High Volume Applications


LV MV HV Cable Accessories & Substation Electrical Equipment

Thorne & Derrick are Specialist Distributors of leading manufacturers of Cable Accessories, Jointing & Installation Equipment.

LV MV HV cable accessories used to joint, terminate, connect, cleat and gland power cables to air and gas insulated substations, transformers, switchgear and overhead line networks.

Hover over our Interactive Electricity Grid to learn more about our product ranges.

LV 600/1000V ◊ MV 11kV 33kV ◊ HV 66kV 132kV 

3M Pfisterer CONNEX Prysmian Nexans Euromold Elastimold Ellis Patents Furse CMP Cable Glands Cembre


Substation & Overhead Line Electrical Safety Equipment

Manufactured by CATU Electrical to enable the safe construction, maintenance and repair of underground cables and overhead lines network up to EHV (400kV).


Further Reading