Dec 31, 2023

What is a Medium Voltage Cable?

An overview of medium voltage cables, their application, the main standards, testing procedures, faults and the importance of third-party cable assessments.


Medium voltage cables range between 6 kV and 33kV. They are mostly produced to be a part of generation and distribution networks for many applications like utilities, petrochemical, transportation, wastewater treatment, food processing, commercial and industrial markets.

In general, they are largely employed in systems with voltage ranges up to 36kV and play an indispensable role in generation and distribution networks.


As the global need for medium voltage cables grows, the consistency with industry standards is becoming increasingly important.

The most important standards for medium voltage cables are:

Structure and materials

Medium voltage cable designs can have different sizes and types. The structure is much more complex than the structure of a low voltage cable.

The differences between medium voltage and low voltage cables are not only in the way the cables are constructed but also in the manufacturing processes and the raw material employed.

In medium voltage cables, the insulation processes differ substantially from those for low voltage cables, in fact:


As per all the recognised standards for cable products, medium voltage cable products require in-depth type testing in order to assess the individual components and the complete cable. Medium voltage cables are tested against their electrical, mechanical, material, chemical and fire functionalities.





To read the full list of laboratory tests access your free medium voltage cable testing guide here:

Common Faults

Low-quality cables increase the fault rate, putting power supplying to the end-users at risk.

The causes are mainly due to prematurely ageing cable infrastructures and poor base quality of jointing or cable termination systems, that lead to reduced reliability or operational efficiency.

The release of partial discharge energy, for example, is a precursor to breakdown, as it provides evidence that the cable is starting to deteriorate, which will lead to faults and failures later down the line.

Cable ageing usually begins by affecting the cable insulation by decreasing the resistance, which is a key indicator of defects, including moisture or air pockets, water trees, electrical trees and other issues. Additionally, the separation sheath can be affected by ageing, increasing the risk of reaction or corrosion, which could cause problems later in service.

Choosing high-quality, thoroughly tested cables extends their life expectancy and enables to predict maintenance or replacement cycles, and avoid unnecessary outages.

Type testing and product approval

Type testing can be useful as it confirms the conformity of specific cable samples to specific standards at a moment in time.

The BASEC Product Approval consists of a more in-dept surveillance through regular auditing of production processes, management systems, and rigorous sample testing of cables.

In the product approval scheme multiple samples are tested in line with the cable or range being assessed for approval.

The very rigorous BASEC certification process assures to the end-user the peace of mind that the cable has been manufactured to perform and last as per the highest levels of quality in line with recognised industry standards, reducing the risks of failure significantly.

Read about type testing and product approval here:

Click here to access the full medium voltage cable testing guide:


Medium voltage cables are vital parts of generation and distribution networks. As the worldwide need for medium voltage cables grows, compliance to the industry cable standards becomes increasingly important. Low-quality cables increase the fault rate, which can endanger the success of power application projects. In order to protect your projects, you should always look for cables that are BASEC approved. The BASEC Product Approval, through regular auditing of production processes, management systems, and rigorous sample testing of cables, ensures that the cables are compliant with the highest industry standards and fit for their purpose.

Choose quality – request BASEC Product Approval for your cables


BASEC, the British Approvals Service for Cables, is a leading provider of cable product certification, which is amongst the most rigorous in the industry. A certified product approval includes comprehensive testing for electrical, mechanical, material, chemical, fire and smoke performance characteristics. Completing cable testing to ensure products are compliant with the relevant local, international, British or European standards. As an independent body, BASEC has over 45 years of experience and is recognised in industry as a mark of reassurance to those specifying cable.

To support product certification, BASEC also provides integrated management systems assessments, to the BASEC product certification requirements (PCR), quality management systems to ISO 9001, environmental management systems to ISO 14001, and health & safety management systems to IS0 45001. BASEC has launched schemes for Registered Stockists to obtain quality management approvals for their processes and procedures involved with sourcing products. As well as a scheme for Control Cables recognised in industry as YY, SY, CY products designed to achieve consistent levels of quality and standardisation in industry. BASEC continues to drive the supply chain to improve quality and safety of cables.

Be part of the journey.

IntroductionStandardsStructure and materialsTestingCommon FaultsType testing and product approvalConclusionChoose quality – request BASEC Product Approval for your cablesAbout BASEC