3M Terminations | Surface Tracking on Medium Voltage Cable Terminations

Published 04 Oct 2024

Surface Tracking – 3M Medium Voltage Cable Terminations

Surface Tracking on Cable Terminations

Surface tracking causes permanent damage to medium and high voltage cable accessories. This damage can affect insulating materials used in products such as cable terminations. During this process, conductive carbon paths form across the insulation.

Electrical discharges produce heat and gradually break down the insulating surface. As a result, carbon deposits build up on the material. Over time, these deposits can form a continuous conductive path. Consequently, the insulation may lose its effectiveness and the cable accessory could suffer serious failure.

Cold Shrink, Condensation and Medium Voltage Cable Terminations

Medium voltage equipment, including switchgear and cable terminations, can experience temperature changes during normal operation. When cables carry a load, thermal cycling causes repeated heating and cooling. As a result, condensation may form around the cable termination. This moisture can increase the risk of premature partial discharge.

Hydrophobic silicone Cold Shrink terminations offer excellent performance in medium voltage applications. In particular, 3M Cold Shrink technology helps repel moisture and limit its build-up on the insulation surface. This helps protect the termination from moisture-related problems.

Furthermore, by limiting moisture accumulation, this technology can help reduce the risk of discharge-related erosion and surface tracking on medium and high voltage cable terminations.

N2XS(F)2Y Cable Terminations – 12/20 (24)kV

Energising Data Centres

The QTIII range of medium voltage terminations is approved and widely used in the data centre sector. These products connect 12/20 (24)kV N2XS(F)2Y medium voltage cables to electrical switchgear. They are designed for cables with XLPE insulation, a copper wire screen and a stranded copper conductor to BS EN 60228.

For data centre projects, these terminations provide a connection solution for the specified medium voltage cable construction.

What Causes Surface Tracking?

Surface tracking can start when electrical insulation breaks down or contaminants collect on its surface. For example, dirt, salt and chemicals can affect the insulating material. These conditions can allow electrical discharges to travel across the surface and create carbonised paths.

In general, three main factors contribute to surface tracking on medium and high voltage cable terminations:

Hydrophobicity: How 3M Terminations Help Protect Against Tracking

Surface tracking describes the gradual and permanent deterioration of an insulator’s surface. As the material breaks down, a conductive path can form across it. Eventually, this process can affect the insulator’s ability to prevent electrical current from passing through.

Silicone offers strong resistance to surface tracking. In addition, it has hydrophobic properties, which means it repels water. This helps keep the insulation surface dry and clean. Consequently, the material can help reduce leakage currents.

3M outdoor cable terminations incorporate 3M rain sheds to help manage moisture. These features interrupt wet leakage paths that may develop in industrial environments. Furthermore, they allow the cable termination to achieve a shorter creepage distance.

Insulator Skirts

Insulator skirts increase the creepage distance. This is the leakage distance between the voltage source and the ground plane.

In addition, their undercut design helps disrupt wet leakage paths. This feature supports insulation performance in outdoor environments where rain and moisture can collect on the termination surface.

Advanced Materials

Insulators and skirted assemblies use specially formulated silicone rubber. This material offers excellent resistance to tracking and helps repel water.

Furthermore, specially formulated High K materials help control electrical stress within the termination. As a result, the design helps manage electrical stress around the cable connection.

Effective Stress Control

Effective stress control distributes electric field stresses along the full length of the termination. This helps prevent high voltage stress from building up in one area of the insulation.

At rated voltage, the voltage stress concentrations on the insulator surface are kept below 15 V/mil. Therefore, effective stress control plays an important role in medium voltage cable termination design.

Further Reading

Looking for more information about 3M cable accessories? The following articles explore cold shrink terminations, electrical stress control and cable repair in more detail.

• 66kV Terminations | New Stock Introduction for 3M Cold Shrink Cable Terminations
• Stress Control | MV Cable Terminations by 3M Electrical
• Cable Jacket Repair | 3M Electrical Webinar

3M Distributors, Stockists & Suppliers

Thorne & Derrick supply the 3M Scotchcast and Cold Shrink product ranges. We offer competitive prices and fast delivery from stock across a wide range of cable jointing and termination products.

Our 3M product range includes:

• Scotchcast cable joints
• Cold Shrink cable joints and terminations
• Scotchcast resins
• Scotch electrical tapes
• High voltage cable joints and terminations

In addition, we stock 3M Cold Shrink cable joints and terminations for 11kV and 33kV applications.

LV, MV & HV Jointing, Earthing, Substation & Electrical Equipment

Thorne & Derrick International are specialist distributors of low, medium and high voltage cable installation, jointing and duct sealing products. We also supply substation and electrical equipment to customers across the UK and worldwide.

Our customers include businesses involved in cable installation, cable jointing, substations, overhead lines and electrical construction. We support projects across LV, 11kV, 33kV and EHV applications. Furthermore, our product range helps customers source equipment for a wide range of electrical infrastructure projects.