Thermoplastic and Thermosetting Insulation 

By on

While there are a vast array of cable insulation materials, these are often divided into two general  types;  Thermoplastic or  Thermosetting.   For example the current capacity determination of a cable in accordance with  the UK Wiring Regulations is categorized into thermoplastic and thermosetting cables.

Thermoplastic materials are composed of chains of  molecules (polyethylene for example).  When heat is applied the energy will allow the bonds to separate and the material can flow (melt) and be reformed.

Thermosetting materials are formed when materials such as polyethylene undergo specific heating or chemical processes. During this process the individual chains become cross linked by smaller molecules making a rigid structure.    Thermosetting materials cannot reheated, melted and remolded.

While thermoplastic materials have the advantage of being able to be reformed, thermosetting materials are generally more heat resistance and have greater strength.

The operating temperature of any cable is an important parameter in determining the maximum allowable current.   While the actual temperature varies depending on the material used, the UK Wiring Regulations limits the choice in calculating the current rating to two temperatures only:

  • Thermplastic 70 0C
  • Thermosetting 90 oC

Note: more specific calculations based on actual material properties are allowed.  However, for ease of use most practical application will use 70 oC or 90 oC and the methods outlined in the regulations.

See Also



Steven McFadyen's avatar Steven McFadyen

Steven has over twenty five years experience working on some of the largest construction projects. He has a deep technical understanding of electrical engineering and is keen to share this knowledge. About the author

myElectrical Engineering

comments powered by Disqus



Useful Motor Technical Information

Sometimes it’s useful to be able to quickly lookup a piece of technical information.  This note is a collection of information related to motors, and in...

Software Usage Guidelines

Using software in our  work is essential for most of us and we are becoming even more dependant on it's use.  While software is a great asset, many times...

Generation of a Sine Wave

A fundamental concept behind the operation of alternating current systems is that voltage and current waveforms will be sinusoidal – a Sine Wave. This...

Introduction to Traction Substations

Following on from my post on railway electrification voltages, I thought an introduction to traction substations would be a good idea. Traction substations...

Fault Calculation - Symmetrical Components

For unbalance conditions the calculation of fault currents is more complex. One method of dealing with this is symmetrical components. Using symmetrical...

Introduction to Cathodic Protection

If two dissimilar metals are touching and an external conducting path exists, corrosion of one the metals can take place.  Moisture or other materials...

Maxwell's Equations - Introduction

Maxwell's Equations are a set of fundamental relationships, which govern how electric and magnetic fields interact. The equations explain how these fields...

Fault Calculations - Introduction

Fault calculations are one of the most common types of calculation carried out during the design and analysis of electrical systems. These calculations...

Power Transformers - An Introduction

One of the fundamental requirements of an alternating current distribution systems it to have the ability to change the magnitude of voltages.  It is more...

1,000 kV UHV First for China

At the beginning of the year China put the world's first 1,000 kV UHV transmission system into operation. Transmitting power at over a million volts is...

Have some knowledge to share

If you have some expert knowledge or experience, why not consider sharing this with our community.  

By writing an electrical note, you will be educating our users and at the same time promoting your expertise within the engineering community.

To get started and understand our policy, you can read our How to Write an Electrical Note