International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 3 - May 2014
Analysis on Dielectric and Mechanical
Properties of Power Cable with Nano
Composites
T.Thenthiruppathi1, R.K.Harish2, R.Ramkumar3
Teaching Fellow,Department of Electrical & Electronics Engineering
University College of Engineering Pattukkottai,
Rajamadam-614701
India
Abstract: Cables are an integral part of the power transmission
and distribution network. As the voltage level increases,
amount of insulation used in the cable increases. Therefore a
need arises for a material with better insulation characteristics
to be used in cables. The dielectric strength of cable insulation
depends on many factors such as the existence of filler material
in the insulation. In this work, laboratory studies on a new
filler material for cable insulation have been conducted. The
influence of Silicon dioxide (SiO2) filler on the dielectric and
mechanical properties of polyvinyl chloride (PVC) cable were
analyzed. Comparison is made between the result of
measurement and the actual value of the pure specimen. From
the results, it is shown that the filler material has improved the
dielectric and mechanical properties of the cable insulation.
Keywords –Polyvinyl chloride; Insulation resistance; AC
breakdown Strength; Tensile strength; Elongation; filler.
I.
INTRODUCTION
In the recent years natural rubber has been completely
replaced by synthetic rubbers and plastics as cable
insulation. The physical properties required for wire and
cable insulation depend on the type of application. It should
have good elongation and tensile and toughness with low
dielectric constant and power factor but high dielectric
strength and insulation resistance. Also, during operation,
because of overloading, the insulation may be exposed to
high temperatures for long periods. This necessitates the
insulation to have excellent resistance to ageing at high
temperatures [1].
In the last few years, a lot of attention has been drawn
towards the dielectrics used as electrical insulating materials
especially polymers. The application of nano fillers in
polymers has caused considerable interests in both academic
and industry owing to their excellent mechanical and
dielectric properties with only a small amount of these nano
particles. This is caused by large surface area to volume
ratio of nano particles when compared to micro and macro
particles. A nano particle is a small particle with at least one
dimension in the nanometic dimension. There is no
scientific field where the nano materials are not being
ISSN: 2231-5381
investigated and explored to find the advantages of these
materials in improving the desired characteristics.
The main types of insulation used in the cable industries
are plastics, rubber, paper, and compressed gas. Plastic
insulated cables are still used because of their reliability,
high dielectric strength, low dielectric loss, and long life [2].
The most commonly used insulating materials for low and
medium voltage cables are polyvinyl chloride (PVC). PVC
is not suitable for high voltage applications because of its
high dielectric constant and high loss. In the manufacture of
PVC cables jacketing, the additives, for the formation and
their compatibility may affect on the electrical properties of
the cable. Therefore, the response of dielectric properties of
PVC to imposed alternating electric field (AC) of various
strengths and frequencies become point of interest [3].
The additives used in PVC formulations are mainly
plasticizers, stabilizers, lubricants and fillers. Fillers have
polymers and they lower the cost of their composites [4].
In this study, vary concentrations of fillers such as
PVC/silicon dioxide compounds have been studied. The
effect of filler materials on dielectric strength of PVC cable
under alternating current stress has been investigated. Filler
is also a material added to a polymer in order to reduce
compound cost and improve processing behavior [5]
II.
SYNTHESIZATION OF NANO MATERIAL
The size of the SiO2 is analyzed by Scanning Electron
Microscopy (SEM). The size is found to be in nano level.
The SEM image of the SiO2 is shown in the Figure1
.
Figure 1 SEM image of synthesized SiO2
It is observed that the average size of the powder is
around 29.6 nm
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 3 - May 2014
SAMPLE PREPARATION
III.
In this work, the PVC has a density of 1.34 g·cm–3,
melting point of 160°C, a tensile strength of 35 MPa and
a melt flow index of 25 g/10 min (230°C, 2.16 kg). The
PVC (without filler) was studied in comparison with PVC
formation (containing different concentration of fillers i.e.,
2.5%, 5%, and 7.5%). PVC/Silicon dioxide filler content
and Magnesium sterate and Dioctate phthalate were melted
using a laboratory Haake PolyOS machine. Mixing of the
samples was done at a temperature of 160°C and mixing
speed of 30 rpm for 15 minutes. The Haake PolyOS
machine is shown in Figure 2.
The lumps are obtained from Haake PolyOS machine
after the mixing process. The lumps are kept in compression
moulding machine and composite plates with dimensions of
270 * 130* 3mm3 were moulded at a temperature of 160°C
and pressure of 135 MPa for 2 hours and followed by
cooling for 5 hours. Figure 3 shows the compression
moulding machine. These plates were cut into circular plate
with dimensions of 100mm diameter and 3mm thickness.
The studied samples are listed in Table 1.
TABLE 1:
FORMULATIONS STUDIED IN THIS PROJECT
Formulation
Sample 1
Sample 2
PVC
(Gram)
100
95
Silicon dioxide
(Gram)
0
5
Figure 2 Haake Polylab OS machine
LABORATORY STUDIES
This project consists of four parts of experiments, which
are Breakdown Voltage test, Insulation Resistance test,
Tensile strength test, Elongation test. All the experiments
were performed using relevant Standards.
A. AC breakdown test
This method describes a technique for evaluating the
ability of an insulating material to resist electrical
breakdown perpendicular to the plane of the material when
subjected to short term, high voltages at standard AC power
frequency. AC breakdown test is carried to find out the
dielectric strength of the sample in the insulating prepared
sample. Breakdown test is performed according to the
standard (IS-10810-part 45, 1984). At room temperature and
pressure voltage applied at the rate voltage. The electrode
used for the measurement is (stainless steel) plane-plane
configuration. The electrode is 25mm diameter and 75mm
diameter used an according to IS 2854. The test set up is
immersed in transformer oil to prevent surface flash over.
The atmospheric correction factor is considered.
B. Insulation Resistance test
The Insulation Resistance was measured at room
temperature by applying 500 V dc voltages to a sample
sheet with a circular shape of 100mm diameter and 3mm
thickness. The sample is then inserted between plane-plane
electrodes. Insulation Resistance test is performed according
to the standard (IS-10810-part 43, 1984). The electrode used
for the measurement is (stainless steel) plane-plane
configuration. The electrode is 25mm diameter and 75mm
diameter used an according to IS 2854.
C. Tensile Strength and Elongation test
All uniaxial tensile and static fatigue measurements were
carried out on a MTS Elastomer Testing System 810
equipped with a 25 kN force cell. The engineering stresses
are calculated using the average of the cross sectional
surface areas as measured at three locations in the gauge
length. Tensile experiments were carried out at a constant
crosshead speed, thus at engineering strain rate. The static
fatigue tests were conducted with a constant load, thus at
constant engineering stress. All stresses and strains in this
paper are engineering values.
Figure 4 Tensile Testing machine and dumb bell sample
Figure 3 Compression molding machine
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 3 - May 2014
The samples are prepared according to IS 10810 (part 7)
– 1984 and are dumb bell in shape with 75mm length.
IV.
RESULTS AND DISCUSSION
This study was carried out to investigate the effects
of fillers on PVC cable dielectric Strength and mechanical
properties. Experimental samples are basically composed of
PVC compound with fillers. The experiments were
performed with the setup described above.
A. AC breakdown test
The dielectric breakdown strength was measured at
room temperature by applying alternating current stress to a
sample sheet with a circular shape of 100 * 3 mm2.The
sample is then inserted between plane-plane electrodes.
Four different specimens sampled from each composite and
have been tested. The five test results were averaged and
taken as the breakdown voltage. Table 2 shows the
breakdown voltage of PVC, PVC/Silicon dioxide. The test
samples are identified as S1 and S2 by their filler contents.
PVC cable without fillers was used as a reference, and is
called S1. All the samples are of a sheet shape with equal
thickness (3mm).
TABLE 2
RESULT OF BREAKDOWN VOLTAGE TEST
Samples
Standard
S1
S2
IS 10810 (part 45)- 1984
BDV
(kV/mm)
% increment
10.89
13.25
-
21.67
Samples
Standard
S1
S2
IS 10810 (part 43)- 1984
Equipment
Meggermeter MIT52012
Resistance
(GΩ)
Volume resistivity (GΩ.cm)
13.6
26.5
222.53
433.54
% increment
-
94.82
The PVC/silicon dioxide improvement in insulation
resistance test compare to unmodified PVC. When 5.0 wt%
silicon dioxide particles are added to PVC, insulation
resistance increases from 13.65GΩ to 26.5GΩ. However,
further increase in silicon dioxide particles loading causes
the insulation resistance of the compound to decrease.
PVC/silicon dioxide composite at 5.0 wt% concentration of
silicon dioxide on compound is the best among all due to its
high insulation resistance.
C. Tensile Strength test
Results from breakdown tests clearly reveal that fillers
have an important effect on the breakdown voltage of PVC
cable. Compared to the unmodified PVC cable, samples
with fillers enhance the dielectric strength. When 5.0 wt%
silicon dioxide particles are added to PVC, breakdown
voltage increases from 10.89 kV/mm to 13.25 kV/mm.
However, further increase in silicon dioxide particles
loading causes the dielectric strength of the compound to
decrease. PVC/silicon dioxide at 5.0 wt% concentration of
silicon dioxide on compound is the best among all due to its
high breakdown voltage.
B. Insulation Resistance test
The Insulation Resistance will be measured by Megger
meter. Four different specimens sampled from each
composite and have been tested. The five test results were
averaged and taken as the breakdown voltage. Table 3
shows the breakdown voltage of PVC, PVC/Silicon dioxide.
The test samples are identified as S1 and S2 by their filler
contents. PVC cable without fillers was used as a reference,
and is called S1. All the samples are of a sheet shape with
equal thickness (3mm).
ISSN: 2231-5381
TABLE 3:
RESULT OF INSULATION RESISTANCE TEST
The Tensile Strength will be measured by Tensile testing
machine. Four different specimens sampled from each
composite and have been tested. The five test results were
averaged and taken as the tensile strength. Table 4 shows
the tensile strength of PVC, PVC/Silicon dioxide. The test
samples are identified as S1 and S2 by their filler contents.
PVC cable without fillers was used as a reference, and is
called S1. All the samples are of a dumb bell shape with
equal thickness (3mm).
TABLE 4:
RESULT OF TENSILE STRENGTH TEST
Samples
Standard
S1
S2
IS 10810 (part 7)- 1984
Equipment
Tensile testing machine (UTMG-120B)
Load (N)
Tensile Strength
(N/mm2)
50.16
4.18
81.96
6.83
% increment
-
63.39
When 5.0 wt% silicon dioxide particles are added to
PVC, tensile strength increases from 4.18 N/mm2 to 6.83
N/mm2. However, further increase in silicon dioxide
particles loading causes the tensile strength of the
compound to decrease.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 11 Number 3 - May 2014
D. Elongation test
The Elongation is measured by Tensile testing machine.
Four different specimens sampled from each composite and
have been tested. The five test results were averaged and
taken as the elongation. Table 5 shows the elongation of
PVC, PVC/Silicon dioxide. The test samples are identified
as S1 and S2 by their filler contents. PVC cable without
fillers was used as a reference, and is called S1. All the
samples are of a dumb bell shape with equal thickness
(3mm).
TABLE 5:
RESULT OF ELONGATION TEST
Insulation resistance is 94.82 higher than the normal
unmodified PVC for 5.0 %wt of silicon dioxide. Tensile
strength is 63.39% higher than the normal unmodified PVC
for 5.0 %wt of silicon dioxide. Elongation is 66.31% higher
than the normal unmodified PVC for 5.0 %wt of silicon
dioxide It can be concluded that 5.0% wt silicon dioxide
mixed with PVC is best among all in regards due to increase
the dielectric and mechanical properties
ACKNOWLEDGMENT
I wish to express my heartfelt thanks to Dr. Somu,
Scientific Officer, Department of Electrical, National Test
House, Chennai and Dr. Bhuvana, Associate Professor,
Department of Plastic Engineering, Central Institute of
Plastic Engineering and Technology, Chennai for providing
the lab facilities to complete the work.
Samples
Standard
S1
S2
IS 10810 (part 7) - 1984
Equipment
Tensile Testing machine (UTM-G120B)
Elongation
(mm)
% Elongation
43.15
58.5
115.75
192.5
[1]
% increment
-
66.31
[2]
REFEENCES
When 5.0 wt% silicon dioxide particles are added to
PVC, elongation increases from 4.18 N/mm2 to 6.83
N/mm2. However, further increase in silicon dioxide
particles loading causes the elongation of the compound to
decrease.
V.
[4]
[5]
CONCLUSION
The test results show that the addition of silicon dioxide has
an impact on the dielectric and mechanical properties. It is
concluded that AC breakdown voltage is 21.87 higher than
the normal unmodified PVC for 5.0 %wt of silicon dioxide.
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