Euromold | 66kV Joints Connectors Terminations Surge Arresters
Thorne & Derrick are leading specialist distributors of MV HV Joints, Terminations & Connectors for use on 11kV/33kV/66kV cable networks – sadly cable failures are increasingly common on onshore and offshore medium/high voltage cable networks.
A toxic cocktail of unskilled labour which is untrained in both basic cable preparation and tool use is usually the cause – this lethal combination unleashes devastation on clients assets nevermind the incalculable cost of downtime associated with power outages.
This investigation and report explains the causes into why the below 66kV cable joints failed by dissecting the cable joints one by one and recording findings to what could have caused the cable failings.
Specialist cable jointing tools to effectively prepare and remove semicon screens on 11kV/33kV and 66kV power cables should always be used by jointers – cable jointers should be trained and competent to install manufacturers products.
The cable joint failure was caused by the poor removal of the semi-conductive and the very bad XLPE insulation preparation. Deep and dirty cuts and burrs can seen in the insulation causing the XLPE insulation to be over stressed and this was what ultimately caused the insulation failure.
All HV cable joints and accessories should only be installed by trained professionals with all the correct accreditation. Any other terminations that have been installed by the above ‘jointer’ should be checked and replaced immediately.
3M pioneered the development of Cold Shrink technology for use as a material for the jointing, termination and connection of medium/high voltage cables. Since then cold shrink has been adopted by global utilities as a user-friendly and reliable MV-HV cable accessory range with high performance, stable life cycle and minimal joint or termination failure rates.
Should you require any support with the specification or supply of MV HV joints, terminations or connectors for use on 11kV/33kV/66kV energy networks please do not hesitate to contact us.
Cold Shrink Reliability Low Failure Rates
0.067% Cold Shrink Cable Joints/Splices
0.022% Cold Shrink Cable Terminations
*Data based upon U.S. failure data of U.S. manufactured 3M Cold Shrink Medium & High Voltage Cable Accessories between 2009 and 2012.
THORNE & DERRICK are national distributors LV, MV & HV Cable Installation, Jointing, Substation Earthing & Electrical Equipment – we service UK and global businesses involved in cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV.
Since 1985, T&D have established an international reputation based on SERVICE | INTEGRITY | TRUST.
Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform , Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.
Thorne & Derrick invite you to join LinkedIn’s largest LV-HV Electrical Discussion Group : Low & High Voltage Power, Cabling, Jointing & Electricals. Discussion subjects include cable installations, cable jointing, substation, overhead line and electrical construction at LV, 11kV, 33kV and EHV. Network, engage and promote your profile, company or products with over 10,000 influencers.
by Chris Dodds T&D - estimated reading time 5 minutes
33kV heat shrink cable joints are high voltage cable jointing kits complete with mechanical connectors or compression crimp connectors for cable jointing of polymeric (XLPE) insulated cables.
Polymeric insulated cables distributing high voltage electricity at 33kV can be used to joint cables with XLPE or EPR type insulation, armoured/unarmoured and with copper wire screen (BS7870) or copper tape screened cables (BS6622).
Heat shrink cable joints feature integrated stress control sleeves and torque controlled mechanical shearbolt connectors can be used to connect conductors (copper or aluminium) without resort to use of crimping tools or associated die sets.
Mechanical cable connectors are ideal for confined space cable jointing where there is restricted working space in manholes, cable vaults and underground trenches, especially on large cross sectional area conductors where hydraulic crimping heads coupled with foot pumps are required for conductor jointing. Bolted cable connections, such as Pfisterer SICON connectors, are installed directly onto the 33kV conductor using standard Allen keys. The bolt shears off smoothly and cleanly when tightened by the cable jointer.
Pfisterer Sicon – cable lugs and connectors with stepless shearbolts for use with cable joints and terminations on high voltage power cable systems
Primarily, a heat shrink cable joint provides electrical insulation, mechanical protection and stress control for high voltage power cables – integral also to the cable joint design is the requirement to prevent water ingress into the cables. Although initial risk assessments would include consideration of electrical water damage, such as cable flood damage, the requirement to deliver medium/high voltage power can necessitate cable exposure to potential flooding, condensation and water immersion. A robust cable joint is designed to withstand the deteriorative effects of water in both indoor or outdoor environments.
The cable joint kits include thick-wall heat shrink adhesive lined tubes to provide high performance water sealing, protection and corrosion resistance in above ground exposed or direct buried underground cable trenches – the outer protection heat shrink tubing (colour black) provides a moisture barrier to water ingress through the activation of an inner lining of adhesive which melts and flows upon the application of a heat source provided by the cable jointers gas torch.
Prior to installing the outer shrink tube the jointer should clean, de-grease and abrade the outer cable sheath of the 33kV cable – to achieve an even wall thickness the cable jointer should keep the flame moving and avoid scorch or burn damage to the heat shrink or cable.
The jointer will apply heat evenly to the centre of the cable joint – once the heat shrink tube is fully recovered (“shrunk”) the joint should be smooth, wrinkle-free and the heat activated sealant should be visible at the tube ends in contact with the cable sheath.
The tough and durable heat shrink provides reinstatement of cable sheath or jacket insulation and withstands trench backfill prior to energisation of the HV joint.
The 33kV joints are installed using normal procedures for heat shrink cable joints with clear installation instructions confirming precise cable stripping dimensions and marking measurements for sheath, semicon and insulation removal – joints are installed using the standard cable jointing tools depending upon cable construction.
Although not designed to be permanently submerged in water, 33kV cable joints use heat shrink tubes to prevent water ingress into high voltage cables whether buried underground or located onto cable containment in MV-HV substations.
Should you require any assistance with the selection or specification of MV-HV joints or terminations please do not hesitate to contact us.
Further reading:
The following Training Video shows the installation process for installing heat shrink joints to single core 33kV cable – this Video is for familiarisation purposes and not intended as a substitute for attending recognised industry training courses and achieving manufacturers competency. The Video produced by SPS with narration provides comprehensive guidance from the initial stripping and removal of the 33kV cable sheath to the final completion of the heat shrink joint.
More 33kV Products For High Voltage Cables ♦ 33kV Surge Arresters ♦ 33kV Fuses ♦ 33kV Lugs ♦ 33kV Portable Earthing ♦ 33kV Cable Terminations
LV ♦ MV ♦ HV
T&D distribute the most extensive range of LV, MV & HV Cable Jointing, Terminating, Installation & Cable Pulling Equipment – we service UK and international clients working on underground cables, overhead lines, substation earthing and electrical construction at LV, 11kV, 33kV and EHV transmission and distribution voltages.
LV – Low Voltage Cable Joints, Glands, Cleats, Lugs & Accessories (1000 Volts)
MV HV – Medium & High Voltage Cable Joints, Terminations & Connectors (11kV 33kV EHV)
Cable Laying – Underground Cable Covers, Ducting, Seals & Cable Pulling Equipment
T&D’s Power Blog covers: LV MV HV & EHV Transmission & Distribution, Substations, Switchgear, Cable Jointing & Termination, Cable Fault & Repair, Underground Cables
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Published 28 Nov 2025
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