ANALYSIS AND SIMULATION OF PARTIAL DISCHARGE FOR DIFFERENT INSULATION MATERIAL

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VOLUME :04 Issue 03 Paper id-IJIERM-IV- II-1294, June 2017

1 ANALYSIS AND SIMULATION OF PARTIAL DISCHARGE FOR DIFFERENT

INSULATION MATERIAL

JAYSHREE NAGDEV¹, ARTI BHANDAKKAR²

1Research Scholar, Shri Ram Institute of Technology College, Jabalpur, India

2 Associate Professor, Shri Ram institute of Technology College, Jabalpur, India

Abstract- In this paper analysis and simulation of partial discharge for different insulating material is done using matlab Simulink. It is well known that the most of the insulation failure is caused due to high voltage across the insulation .In this study, the dependency of partial discharge on the permittivity of the solid insulating material to be analyzed with the help of void model.

Keywords– solid insulation, void model, partial discharge, permittivity.

INTRODUCTION - Rapid growth in power sector of the nation has given the opportunity to the electrical engineers to protect the High Voltage equipment for reliable operation during their operating life.

It has been seen that the major problem in high voltage equipment is the degradation of insulation i.e., quality of the insulation material of the high voltage equipment [4]. The major cause of degradation of material is Partial Discharge. It generally begins within voids, cracks, at conductor-dielectric interfaces within a solid insulation system or in bubbles within liquid dielectrics. The insulations used in high voltage equipment are generally not in pure form, it contain some impurities in the form of voids.

These voids may be of any shape like spherical, cylindrical, cubical, irregular shape etc. These voids are formed during the manufacturing process. Generally, these voids are filled with a medium such as gas,

which has lower breakdown strength than the solid insulation.

The permittivity of the filling medium is frequently lower than that of the solid insulation, which causes the field intensity in the void to be more than in the dielectric.

Under normal working stress of the insulation system the voltage across the void may exceed the breakdown value and may initiate breakdown in the void. This breakdown is called Partial Discharge. Partial discharge reduces the strength of the insulation which further leads to the partial or total insulation failure [2].

Partial discharges are in general a consequence of local electrical stress concentrations in the insulation or on the surface of the insulation.

Generally it appear as pulses of duration of much less than 1μs [1].

Void model- Polyethylene and epoxy resin insulator with void inside is considered having dimensions (30mm ×30mm ×5mm) in this model. The void having (cylindrical

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2 void) of height of 4 mm and a radius

of 2 mm is used in a cube sample.

As the electrical circuit model consists of three capacitors the values of these capacitors are calculated.

Figure 1 void model

Fig 1 shows the void model of Polyethylene and epoxy resin insulator with void inside is considered having dimensions (30mm ×30mm ×5mm) and table 1 shows the permittivity of the different solid insulator

Table 1 cylindrical void

Insulation

Material Relative Permittivity Polyethylene 2.2

Epoxy Resin 3.4

Table 2 Different Components and their Value

S.No Components Rating 1 HV measuring

capacitor 1500 pF 2 HV coupling

capacitor 1000 Micro F 3 Detector circuit

resistance 50 ohm 4 Detector circuit

inductance 0.63 mH 5 Detector circuit

capacitance 0.47 Micro F

Table 2 shows the Different Components and Their Value used in simulation purpose. By using void model of different insulator calculated the capacitance value

shown in table3.And these value of capacitance is calculated from the formulas which is given below:

Ca= ɛ𝑜×ɛ𝑟(𝑎−2𝑏)×𝑏 𝑐

Cb = 𝜀𝑜 ×𝜀𝑟 ×𝜋×𝑟2 𝑐−ℎ

Cc = ^{𝜀𝑜 ×𝜋×𝑟2}_ℎ

Table 3 Capacitances Values Insulatio

n

Material

Capacitances

Ca Cb Cc

Polyethyl ene

3.17×

10-12

2.55×

10-13

2.78×

10-14 Epoxy

Resin 4.83×

10-12 3.89×

10-13 2.78×

10-14 Design and Result Analysis - MATLAB Simulink model is developed to study the partial discharge in an insulation material.

In this work the simulation is done on two different solid insulation (polyethylene and epoxy resin) materials. For Simulation a cylindrical void is taken at the center of each sample of insulation material. The simulation is done on different applied voltage. Fig. 2 shows the simulation diagram of solid insulators.

Figure2 Simulink model of solid insulator

Now in first analysis the Partial discharge results for epoxy resin insulation material.

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3 Figure 3 input ac voltage 10 kv

Fig.3 shows the input voltage applied to the void capacitance model. The output of different parameters is shown below. The fig.4,5,6 and7 shows the partial discharge at different voltage level applied across the void. The generated partial discharge is different magnitude in all cases of voltage Patten.

Figure 4 Partial Discharges at 10 KV The Table 4 Variation of maximum PD amplitude with different applied voltage. The amplitude of partial discharge is obtained high at 30 kV.

The value of magnitude is 6x10-4 at 30 KV. The value of magnitude is increasing at higher kilo volt rating.

Table 4 Variation of maximum PD amplitude with different applied

voltage

S.No Applied voltage

(kV)

PD amplitude (V)

1 5 3.4 x10-4

2 6 1.5 x10-4

3 10 1.8 x10-4

4 20 1.7 x10-4

5 28 4.8 x10-4

6 30 6.0 x10-4

Figure 5 Partial Discharges at 5 KV

Figure 6 Partial Discharge at 20 KV

Figure 7 Partial Discharge at 30 K

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4 V

Figure 8 Variation of maximum PD amplitude with different applied voltage.

The figure 8 shows the Variation of maximum PD amplitude with different applied voltage. The value of magnitude is obtained higher 6x10^-4 at 30 KV. The Table 5 Partial discharge pulses at different phase angle with different applied voltage.

The values of partial discharges are not constant at different values.

Table 5 Partial discharge pulses at different phase angle with different applied voltage

S.No Phase Angle in degree

5

kv 10 kv 20 kv

1 0-45 17 12 26

2 46-90 30 25 31

3 91-135 33 22 29

4 136-180 33 29 32 5 181-225 34 22 34 6 226-270 31 27 32 7 271-315 29 26 32 8 316-380 30 23 29

The fig.9,10 and 11 shows the partial discharge pulse at different voltages 5,10 and 20 kv

Figure 9 PD pulses at different phase angle with applied voltage of 5

kv

Figure 10 PD pulses at different phase angle with applied voltage of

10kV

20kV

Fig. 12 shows the comparison of PD pulses at different phase angle with applied voltage. Here we compare the all values of phase angle between 0 to 360 degree at different

0 2 4 6 8

5 6 10 20 28 30

0 5 10 15 20 25 30 35 40

0 5 10 15 20 25 30 35

0-45 46-90 91-135 136-180 181-225 226-270 271-315 316-380

0 10 20 30 40

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5 voltage levels. The results are not

constant at all points.

Figure 12 comparison of PD pulses at different phase angle with applied voltage

Similarly another calculation is done by Polyethylene solid insulator. The results are shown below

Figure 13 Partial Discharge at 5 KV The fig.13,14,15 and 16 shows the partial discharge pulse at different voltages 5,10,20 and 30 kv

Figure 16 Partial Discharge at 30 KV Table 6 Variation of maximum PD amplitude with different applied voltage.

S.No Applied

voltage (kV) PD amplitude (V)

1 5 10.6 x10-4

2 6 1.8 x10-4

3 10 1.7 x10-4

4 20 2.2 x10-4

5 28 5.2 x10-4

6 30 3.9 x10-4

The Table 6 Partial discharge pulses at different phase angle with different applied voltage. The values of partial discharges are not constant at different values..

0 10 20 30 40

0-45 46-90 91-135 136-180 181-225 226-270 271-315 316-380

5 kv 10 kv 20 kv

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6 .

Figure 17 Variation of maximum PD amplitude with different applied

voltage.

An increasing voltage of 0-30 kV is applied across the solid insulation to observe the maximum amplitude PD pulses. The corresponding data found is depicted in Table and graph has been plotted as shown in figure.

From the graph it is observed that maximum amplitude of 10.6×10^-4 is obtained at 5 kV of applied voltage.

Table 7 Partial discharge pulses at different phase angle with different

applied voltage

S.No Phase Angle in

degree

5

kv 10 kv 20

kv

1 0-45 25 17 31

2 46-90 30 26 33 3 91-135 32 22 33 4 136-180 35 27 31 5 181-225 33 30 32 6 226-270 29 32 27 7 271-315 29 31 26 8 316-380 31 32 24

The fig. 18,19 and 20 shown the bar chart of different values of number of partial discharge at different rating of voltage whose values are depicted in table 7.

Figure 18 PD pulses at different phase angle with applied voltage of 5

kV

10kV

Figure20 PD pulses at different phase angle with applied voltage of

20 kV

0 5 10 15

5 6 10 20 28 30

0 5 10 15 20 25 30 35 40

0 5 10 15 20 25 30 35

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7 Figure 21 comparison of PD pulses

at different phase angle with applied voltage

The partial discharge pulses are analyzed by dividing single applied sinusoidal cycle of 50 Hz into eight equal parts. Each part has 45 degree phase angle interval. The number of PD pulses for each interval is plotted for different applied voltages. Figures shows graph for number of PD pulses v/s different phase angle for different applied voltages (i.e, 5kV, 10kV and 20kV). The partial discharge phenomenon is random in nature so the number of PD pulses is not constant for every cycle Partial discharge is the main problem in high voltage power equipment system. Therefore, detection and measurement of partial discharge is necessary to keep the equipments in healthy condition during their operation. In this work an epoxy resin is taken as a solid insulation material and MATLAB Simulink based model has been adopted to observe the partial discharge activity inside the solid insulation. It is found that with increase in applied

voltage across the void, partial discharge increases. This study is employed to find out the maximum partial discharge, Charge transfer with respect to applied voltage, Number of PD pulses with respect to phase angle, Number of PD pulses for different applied voltage. Based on the SIMULINK model partial discharge characteristics are plotted.

Table 8 Variation of maximum PD amplitude with different applied voltage

S.No Applied voltage (kV)

PD

amplitude (V) Epoxy Resin

PD

amplitude (V) Polyethylene 1 5 3.4 x10-4 10.6 x10-4 2 6 1.5 x10-4 1.8 x10-4 3 10 1.8 x10-4 1.7 x10-4 4 20 1.7 x10-4 2.2 x10-4 5 28 4.8 x10-4 5.2 x10-4 6 30 6.0 x10-4 3.9 x10-4

Figure 22 Variation of maximum PD amplitude with different applied voltage

CONCLUSION-To observe the partial discharge characteristics it is necessary to see the maximum partial discharge values at different applied voltages. It helps for the

0 5 10 15 20 25 30 35 40

0-45 46-90 91-135 136-180 181-225 226-270 271-315 316-380

5 kv 10 kv 20 kv

0 2 4 6 8 10 12

5 6 10 20 28 30

Epoxy Resin Polyethle ne

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8 partial discharge detection and

measurement in high voltage power equipment system. All sample (epoxy resin, polyethylene) considered for the simulation are cubical and the void in each sample is cylindrical. Each insulation material has different permittivity or dielectric strength and hence their void model capacitances are also different, due to which different partial discharge pattern has been obtained for different material at different voltage. The observation shows that the permittivity of the insulation material is also an important parameter of partial discharge. It shows that partial discharge is the function of permittivity of the insulation material. All the simulation work is done on MATLAB software.The present work can also be extended for different high voltage power equipment model for detecting the PD activity. Further we could find out the partial discharge activity in different types of insulation.

REFERENCES

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