Underground Cable Joints

Underground cable joints are a critical reliability factor in medium voltage (MV) distribution networks. While cables themselves are designed for decades of service, failures most often occur at joints or splices. This is especially in underground environments with wet soil, soil movement and high thermal cycling.

However, real‑world experience across utilities and contractors shows that product quality alone is not enough. The quality of the installation is equally decisive for long‑term underground performance.

Lovink develops and supplies underground cable joint solutions (also referred to as underground cable splices or cable jointing systems) that are engineered as complete systems. These joints, combined with dedicated training and education through the Lovink Academy to support consistent, high‑quality installations in the field.

This page explains when underground cable joints are required and what defines underground performance. You can also read how Lovink supports utilities, contractors and EPCs with proven joint technologies and installer training.

An underground cable joint (also known as an underground cable splice) connects two underground power cables or creates a transition between different cable types within a buried installation. Unlike above‑ground joints, underground joints must perform reliably while being:

Permanently buried
Exposed to moisture or groundwater
Subject to soil pressure and thermal cycling
Inaccessible after installation

Because underground joints cannot be visually inspected or easily repaired, installation quality is critical. Even the best joint design can fail prematurely if installation procedures are not followed correctly.

Underground cable jointing introduces specific risks that directly affect joint and splice performance:

• Moisture and contamination during installation
• Interface degradation at cable sheath and screen transitions
• Mechanical stress from soil movement or settlement

Dedicated underground cable joints or splicing systems are required when installations involve:

Medium voltage underground distribution networks
Urban cable routes with confined joint pits
Renewable energy grid connections (wind & solar parks)
Long underground routes where repair access is difficult
Networks where long service life and low failure rates are critical

In these cases, joint selection should be based on system performance, installation method and installer competence, not just on product specifications.

Use this 30‑second selection guide to determine the right underground cable joint solution.

Same cable type (XLPE/EPR), straight connection, limited joint pit space?
→ LoviX® R straight-through underground cable joints
Compact, flame‑free cold‑shrink installation, waterproof and designed for consistent quality in the field. → View LoviX® R straight-through joints

Transition between cable types, branch connection or complex underground route?
→ LoviSil® M-series underground cable joints
Liquid silicone insulation providing excellent long-term electrical stability when installed correctly.
→ View LoviSil® M-series cable joints

Not sure which underground cable joint or splice fits your project?

• Request a selection check from one of our specialists
  (Submit basic cable and environment details – no obligation)
• Prepare your request and check the information needed for selection

A reliable underground cable joint or splice is the result of two equally important factors:

1. Product and system design
   Stable electrical insulation under underground conditions
   Long-term sealing at sheath and interface transitions
   Mechanical robustness against soil and external loads
   Proven ageing behaviour over the network lifetime
2. Installation quality and workmanship
   Correct cable preparation
   Controlled installation steps
   Use of trained and certified jointers
   Adherence to documented installation procedures

Lovink underground cable joints are type-tested as complete systems, but their performance in the field depends on correct installation by trained professionals.

To avoid confusion and overlap:

Underground describes the installation environment
Waterproof describes a performance requirement under water exposure
Resin describes a sealing or protection technology

If your primary focus is water exposure or flooding, see:
→ /applications/waterproof-cable-joints/

If you are researching resin joint or resin splicing technology, see:
→ /en/resin-cable-joint-kits/

This page focuses on underground performance as a system requirement, including installation quality.

Lovink offers two proven joint families designed for underground MV installations. Selection depends on cable type, benefits needed, technology, installation method and challenges that you see with this installation in the field.

LoviX® R joints are designed for underground polymeric cable connections where compact design, repeatable installation and reduced installation risk are required.

Key characteristics
Designed for underground installation
Cold‑shrink technology (flame‑free)
Compact geometry for confined joint pits
Supports consistent installation quality

Typical use cases
Urban underground MV networks
Confined joint pits
Projects where installation speed and consistency are critical

→ View LoviX® R straight-through joints
→ Learn more about LoviX® technology

Quickest way to select the right Joint, contact now!

The LoviSil® M-series is engineered for underground applications requiring maximum long-term reliability, especially in complex or mixed cable systems.

Key characteristics
Liquid silicone insulation system
Excellent long-term electrical stability
Suitable for straight, transition and branch joints
Highly dependent on correct installation procedures

Typical use cases
Complex underground situations
Branching cables, looping cables, terminating cables
Waterlogged areas
Area’s with high temperature cycling
Renewable energy grid connections
Large difference in cable diameter
Other Transition joints and mixed cable systems

→ View LoviSil® Technology

→ Select the right LoviSil® Technology Joint

Across the industry, improper installation remains one of the main root causes of underground cable joint failures. To address this, Lovink invests not only in product development, but also in education and training.

The Lovink Academy provides dedicated training programmes for:

Jointers working in underground MV networks
Trainers and supervisors responsible for installation quality
Utilities and contractors aiming to reduce joint-related failures

Training focuses on practical installation skills, correct procedures, understanding joint behaviour and recognising common installation risks.

→ Learn more about the Lovink Academy

Lovink underground cable joints are proven in real underground installations, where joints are installed once and expected to perform reliably for decades. In practice, long‑term performance depends not only on joint design, but equally on installation quality and installer competence.

The following projects and technical blogs demonstrate how proven joint systems, correct installation procedures and training come together in real underground networks:

Practical installation of LoviX® R at SAB Training Centre (Netherlands)
A hands‑on installation of the LoviX® R straight‑through joint in a professional training environment. Jointers and trainers evaluated the installation process, repeatability and error reduction under realistic underground conditions.
→ View practical installation of LoviX® R at SAB Training Centre [lovink-enertech.com]

LoviSil® cable joints: the solution in limited installation space
An underground project with extremely limited joint pit space, where correct installation and product choice were critical. The case highlights how compact joint design supports safe and reliable installation in confined underground environments.
→ View project – limited installation space [lovink-enertech.com]

Easy installation of LoviSil® cable joints for PILC cables
A practical field demonstration for PILC cable jointing, focusing on ease of installation, reduced risk of installation errors and the importance of training and demonstration before large‑scale deployment.
→ View project – easy installation for PILC cables [lovink-enertech.com]

Jointing industrial underground cables
A technical deep dive into the challenges of underground jointing in industrial networks, where cable dimensions, earthing complexity and limited access demand experienced jointers and correct installation procedures.
→ Read blog – jointing industrial cables [lovink-enertech.com]

Together, these examples show that reliable underground performance is achieved when proven cable joint systems are combined with trained installers — a principle that underpins both Lovink product development and the Lovink Academy training programmes.

Lovink underground cable joints are commonly applied in:

Medium voltage distribution networks
Onshore wind and solar parks
Urban infrastructure projects
Industrial underground cable routes

Discuss your underground application with a specialist

Our specialists support you with:

Joint selection for your underground network
Advice on installation methods and risks
Access to training through the Lovink Academy
Long-term reliability and lifecycle optimisation

→ Request a selection check or a 15‑minute technical call
→ Register interest in Lovink Academy training