Cable dimensional measuring

Dimensional measuring on cables
IEC 60811-201/-202/-203, UNE-EN 60811-201/-202/-203, UNE-EN 50396.

Metal conductors inside cables transport electric energy. The insulation provides protection for users and equipment against electric shock and protects the conductor from damage and corrosion.

In the case of cables with more than one conductor under the same sheath, this, in addition to supplement the electrical insulation, protects and groups the insulated conductors. Besides that, there might be, depending on the cable type, other intermediate layers with similar purposes.

Constructive standards in which the manufacturing of the cables is based require for these polymer layers, depending on the cable type, minimum values for the average thickness, minimum values for the lowest thickness at any point and overall dimensions within a certain range (diameter).

Dimensional checks allow us to ensure that requirements are met and that cables have, as far as it depends on polymer coatings, the appropriate electric and safety features.

A cross section sample of the layer to check is prepared and then measured on a profile projector according to the construction standard requirements (which points check to obtain the average thickness, how many points and how many degrees apart from each other, among other details).

The equipment projects a light beam through and around the sample so the edges are clearly defined, enlarges the image and allows to measure with precision (using artificial vision systems with cameras or through manual measuring with micrometers).

The coating of electric conductors uses plastic materials because of its flexibility, mechanical- and insulating properties.

The position of a layer in the cable construction will determine which properties are the most important.

The insulation (applied directly over the conductor) mainly protects the surroundings from the electricity flow.

Sheaths are designed aiming for the protection of the elements inside the cables and, in some cases, provide special features such as improved safety in the case of a fire.

In all these circumstances the amount of plastic applied determines the cable behavior.

Plastic materials in general are very good for insulation purposes since their electrical charges are not able to move under the influence of an electric field.

Glass, for example, is also a good insulation but it is very rigid and fragile.

The lack of insulating or sheathing materials can lead to a worsening of the cables characteristics and contribute to damages during its handling, but an excess of them will reduce its flexibility and increase the weight and diameter of the cable, making it hard to handle.