Dielectric Loss Calculation for XLPE Insulated Single Core Copper Cable

Dielectric loss calculation means the calculation of electromagnetic energy loss as inherent dissipation of dielectric material. 

Dielectric loss is represents as tan δ widely known as loss angle or loss tangent.

An example to calculate Dielectric Loss for 132 kV XLPE single core copper conductor cable:

Above formula shows the calculated dielectric loss for mentioned cable is 0.38 watt per meter. Where the parameters used to calculate this value are shown.

Rated voltage 132 kV, so, phase to earth voltage is 76.2 kV or 76,200 volt (132/sq. root 3);

Insulation thickness 18 mm (outer diameter – inner diameter)/2 or (74.5-38.5)/2;

Value of loss angle tan δ depends on type of material.

What Is XLPE?

XLPE is the shorten of Crossed Link Polyethylene,  Cross-Linked Polyethylene (XLPE) is modified three-dimensional molecular Polyethylene structure  that is manufactured from polyethylene plastic to improve some specific properties like- heat deformation, smokeless during fire, abrasion, continuous work at 90 deg. and highest 250 deg. centigrade temperature and so on.  

Basic molecular difference between LDPE, HDPE and XLPE are shown in the figure. In modern cable engineering technology, the XLPE provide may advantage to use as insulation.

Why Happen Dielectric Loss in XLPE?

If you look carefully at the XLPE molecular structure in the figure, you will find some open ended brunches. The main brunches are strongly bonded to each other and formed a three dimensional strong structure, but one end opened brunch comparatively weak bonded. When this material is placed in a high electromagnetic field, these weak brunches vibrate continuously and loss energy which is known as Dielectric Loss.

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What Is Dielectric Loss?

A definition for Dielectric Loss is very difficult to find an easy and understandable to all. Most of the definitions are for specialized, not recognizable for a non-technical or general person. That is why we are here today with this article to make easier the Dielectric Loss definition.

First of all let us see some definitions of Dielectric Loss what today are using:

1> Dielectric Loss is define as the inherent dissipation of electromagnetic energy as heat in dielectric materials which is represents as Loss-angle or Loss-tangent tan δ.

2> Dielectric Loss is an energy loss in a dielectric materials as heat dissipation due to cycle of current alternate in a period of time. In alternating current system dielectric materials charged in first by one direction and then discharge and re-charged by opposite direction of current flow, this repetition system causes of unproductive heat generation which define as Dielectric Loss.

 

What Is Dielectric Materials?

Dielectric material is such a kind of insulator material that can be polarized when applied an electric field to it. So, dielectric material having a polarization property. That means when dielectric material placed in an electric field it’s electric charge get aliened and attempt to flow but not flows. Dielectric materials are mainly use in capacitor for their dielectric property.

Dielectric material is a poor electrical conductive material used as an insulator for electrical system. Porcelain, Plastics, Glass, Mica, and the oxides of various metals are used as Insulator. In electrical cable PVC, HDPE, MDPE, LDPE, LLDPE, XLPE, EPR etc. are used as insulation.

What is the Dielectric Strength?

Simply we can explain the dielectric strength of an insulating material that the material can withstand in their insulating property in which maximum electric field. Other way, how much strength can take a dielectric material without any breakdown.

Dielectric strength not same for all materials, to understand the comparison of dielectric strength in various materials find the table.

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What is Difference Between Insulator and Dielectric?

The material used as insulator for their electrical insulating or obstructing property; on the other hand dielectric used for electric charge holding or storing property. A common example of insulator is outer jacket of electrical cable and dielectric is the insulating material in capacitor.

Comparison of Dielectric Strength
Material	Dielectric strength (kV/inch)
Vacuum	20
Air	20 to 75
Porcelain	40 to 200
Paraffin Wax	200 to 300
Transformer Oil	400
Bakelite	300 to 550
Rubber	450 to 700
Shellac	900
Paper	1250
Teflon	1500
Glass	2000 to 3000
Mica	5000