Investigation Break Down Voltages for High Density Polyethylene Cables Using Multiple Regression

DOI: http://dx.doi.org/10.24018/ejece.2021.5.2.311 Vol 5 | Issue 2 | March 2021 26 Abstract — This paper illustrated the electrical characteristic of High Density Polyethylene (HDPE) by adding an alumina trihydrate (ATH)filler At concentrations vary from 0% to 40%. Multiple Regression Analysis (MRA) was used to find the best suitable curve between the percentages of ATH filler and the Break down Voltages (kV/mm).


I. INTRODUCTION 1
HDPE cable sheathing is a type of macromolecular polymer. Observations and researches regarding its dynamic properties, especially under fatigue loading, are the key to understanding the durability of cables as well as that of entire cable-stayed bridges, and these should receive greater attention. In general, because of the effects of and competition between cracking and the shear zone within macromolecular materials, microscopic expansion mechanisms are highly complicated [5]- [7]. Under fatigue loading, the evolution of fatigue damage in HDPE materials is typically as follows. As micro cracks develop and propagate, their number and density reach a critical value, at which time one or more neighboring micro cracks begin to form fatigue cracks. Because of the concentration of stress, new micro cracks form at the peaks of the cracks and develop further under the effect of cyclical stress. Multiple Regression Analysis is a form of predictive modeling technique which investigates the relationship between a dependent and independent variable using the relationship between variables to find the best fit line or the regression equation

A. Specimens
Specimens were prepared from HDPE with different concentrations of ATH according to ASTM 149.
➢ Break Down Voltage test: The ability of the insulating material to withstand maximum electrical stress without break down. Sets of blend samples have been prepared under Four weather testing conditions are performed such as (Dry -Wet -Salty Wet -Acid). Fig. 1 illustrates the A.C high voltage obtained from a single phase high voltage auto transformer (Terco type HV 9105) 100 KV -5 KVA -50 Hz, has been used which is supplied by the main board from its primary Fig. 1. The main board is controlled by variac (0-220 V).

High Voltage auto transformer
A resistor of 2.8 MΩ was connected to the secondary winding of the high voltage testing transformer in order to protect the high voltage transformer from the high current during the test.

Test Electrodes
During this study two identical electrodes are used. Each of them has 5 mm diameter, made from copper brass. Fig. 2 shows the electrodes and the Specimen between them.

Specimen Measure
Each specimen has 50 mm diameter and 1 mm thickness.

III. EXPERIMENTAL RESULTING
The experimental results are discussed; the results which have been obtained are analyzed.
Many factors have been studied in the present work. These are: 1. Wet condition effect; 2. Dry condition effect; 3. Salty Wet condition effect; 4. Acid condition effect. Table I shows the results of the average break down voltage (kV/mm) for mix specimens (HDPE/ATH) under different condition. It can be cleared that, increasing weight percentage of ATH improves the break down voltage of the blends. The break down voltage decreased, at wet, salinity and acid conditions. Because of the water and salinity caused leakage current in addition to at acid conditions, causing chemicals to attack the break down voltage.
IV. CONCLUSION 1. The best percentage of filler to improve electric characteristic for HDPE under several weather conditions is 30%.
2. Exposure the samples to acid condition affected negatively on its break down voltage.
3. Salty Wet condition resulted in decreasing the break down voltage due to NaCl solution absorption.
4. The break down voltage decreased in wet condition as compared with those in dry condition because of hydrophobicity of polymeric material inhibits the formation of a continuous water film and therefore suppresses the leakage current thereby improving its contamination break down voltage performance.

The lowest values of break down voltage at acid
condition. This is because of the Chemical material attack most frequently leads to embrittlement or brittle failure.
6. Electrical characteristics have decreased at higher salinities and moisture.
7. The optimization methods are more accurate than the laboratory method, But its complementary methods not separate methods. Dr. Loai Nasrat is a professor at Aswan University, Faculty of Eng., Elect. P&M Department. He has been actively involved in both basic and applied research in the area of HV engineering. His research interests include HV insulators, polymeric materials, HV cables insulations and environmental studies. Author and co-author of more than 100 papers on HV polymeric insulating materials, published in technical journals and proceedings of national and international conferences.
Dr. Salah Kamel is an associate Professor, Dep. of Electrical Engineering, Faculty of Engineering, Aswan University. Author and co-author of more than 50 papers on HV polymeric insulating materials, Power system, Renewable energy, and Smart grid, published in technical journals and proceedings of national and international conferences.