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- When not installing SPD, the simulation value of residual voltage at loads is shown in Table 4.3

- When not installing SPD, the simulation value of residual voltage at loads is shown in Table 4.3

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Figure 4.5. Power distribution network simulation diagram in Matlab.



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Simulation results test residual voltage through AC and DC loads when the voltage

transients appear because lightning is greater than the protection voltage (UP) according to

the standards. Therefore, it is necessary to select SPD and installation location on the power

line for electrical and electronic equipment.

- When selecting SPD:

+ In the main distribution board, select level I SPD (Cat B): Based on the location

of the installation of source transmission lightning protective devices, the lightning density

of the structure and the surge amplitude of lightning current is 40kA, waveform 8/20µs.

Select surge protective device with 275V, surge current (Imax impulse current) 40 kA or 70

kA or 100 kA (3 devices with different Imax).

+ At the AC distribution board, select level II SPD (Cat C): Based on the location

of lightning protective device installation, the lightning density and surge amplitude appear

40kA, waveform 8/20µs. Select SPD with 275V, surge current is 25 kA or 40 kA or 70kA

(3 devices with different Imax pulse current). The simulation results of the voltage test for

AC and DC loads are shown in the Table in Table 4.4, Table 4.5 when installing SPD

installed at the essential main switch board and the main switch board.

Table 6. The protection voltage simulation values for AC load when SPDs are installed

in the essential main switch board and main switch board.

SPD class I

Rated

current

Voltage

amplitude tolerance

8/20µs

of MOV

(kA)

(%)



SPD class II



Rated

voltage

of MOV

(V)



Rated

current

of

MOV

(kA)



The peak

of

protection

voltage

across the

load

(V)



Rated

voltage

of MOV

(V)



40



10



275



40



1779



275



40



10



275



70



1661



275



40



10



275



100



1407



275



Rated

current

of

MOV

(kA)

25

40

25

40

70

25

40

70



The peak

of

protection

voltage

across the

loads

(V)

1117

1071

1089

1046

1011

1008

976

950



Table 4.5: The protection voltage simulation values across the DC loads when SPD are

installed in the essential main switch board.

Rated voltage of

MOV (V)

(SPD class I)

275

275

275



Rated current

of MOV (kA)



Voltage

tolerance of

MOV

(%)



Rated current

amplitude

8/20µs

(kA)



40

70

100



10

10

10



40

40

40



The peak of

protection

voltage across

the load

(V)

63.7

63.7

63.9



Step 5: Check protection voltage:

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- From the simulation results after installing lightning protective device with a standard

lightning surge 8/20µs, the surge amplitude of 40kA for devices with different tolerant

current pulse at different protection levels:

+ Class I: SPD-275V-40kA; SPD-275-70kA; SPD-275-100kA

+ Class II: SPD-275V-25kA; SPD-275-40kA; SPD-275-70kA

- Results of simulation of residual voltage UP (protection voltage) caused by

lightning after installing surge protective device, selecting surge protective device on low

voltage power line as follows:

+ Installation of surge protective device at essential main switch board: For class I

SPD, lightning surge 8/20µs, 275V 40kA;

+ Installation of surge protective device at main switch board: For class I SPD,

lightning surge 8/20µs, 275V 25kA;

Step 6: Through the selection of surge protective device and the selection of the

location of surge protective device on power lines for telecommunication site, test the

protection voltage when the voltage transients appear due to lightning induced output for

AC and DC electrical equipment. From the Step 4 simulation results and test in Step 5, the

construction has been protected to avoid the risk of damage caused by lightning on the low

voltage voltage power line.

4.4. Conclusion

The content of chapter 5 has proposed the solution of surge lightning protection the

low voltage power lines in general according to the following steps: Determining the risk

of damage caused by lightning by analyzing and applying tissue modeling methods

simulated to select device and location to install surge protective devices on low voltage

power lines to meet technical requirements.

The effectiveness of the proposed solution applies to telecommunication site in

Long Thanh district, Dong Nai province and has the following comments:

- When surge protection measures have not been applied on the power line, the risk

of struture of service damage is R2 = 0,0309 which is greater than the tolerable risk value

in [1] is10-3. When a level II SPD is installed, the risk value of loss of service reduced at

R2 = 5,04.10-4 which meets the tolerable risk in [1].

When selecting surge protective device, installation location and conducting

simulation to test the protection ability of surge protective devices on low voltage power

lines. From the simulation results, it is proposed to select and install surge protective device

to meet the technical requirements and economic efficiency.

+ Surge protective device is selected and installed at essential main switch board

with level I: surge 8/20µs 40kA, 275V;

+ Installation at level II in main switch board: surge 8/20µs 25kA, 275V (according

to IEC 60614- 1 and AS / NZS 1768).



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Chapter 5



CONCLUSION

5.1 Research results

The thesis has focused on researching to complete the main contents as follows:

1. Propose improved method of risk assessment of damage due to lightning based on

the use of risk assessment method according to IEC 62305-2, with some factors being

calculated in detail by the proposed standards such as AS/NZS 1768 and IEEE 1410. The

factors considered include: probability of a dangerous discharge based on structure type;

the number of service lines connected to the structure, shielding factor along the power

line.

For illustrative structure, the results of calculating the risk assessment of damage due to

lightning according to the proposed method differ significantly when calculating the risk

assessment of damage due to lightning according to method of IEC 62305-2. Specifically,

the risk of loss of human life R1 is lower than about 13%, and the risk of loss of economy

R4 is lower than about 11%.

2. Propose lightning surge generator model applied to 4 different types of lightning

surge currents in Matlab with the errors within the allowed range. Specifically, the

maximum error value of peak current is 0.03% (<10%), the front time is 0% (<10%), the

tail time is 3.71% (<10%).

3. Propose the detailed model of surge protective device on the low voltage power line

in Matlab considering the following parameters: maximum voltage operation, maximum

gurge current, threshold voltage errors, and temperature. The lightning surge protection

device model has errors within the manufacturer's specified range from the catalogue

(10%):

- The residual voltage between the model and catalogue has the largest error of 1.2%,

and the smallest is 0.08%.

- Residual voltage between model and test results on AXOS8 system at laboratory C102

of Ho Chi Minh City University of Technology and Education with a temperature at 280C

is 7%, and at 1000C is 5%.

- According to the limitation of the scope of the research, the thesis proposes solution

to protect lightning surge on the power line according to the following steps: Calculate and

determine the risk components of damage caused by lightning, choose surge protective

device to on low voltage power line and select the location to install surge protective device

for typical struture illustrating, assessing the protection effectiveness of surge protective

devices for the solution proposed according to simulation modeling method. To illustrate,

the surge protective device solution on the power line is applied to telecommunication site

in Long Thanh district, Dong Nai province.

- The outstanding points of the thesis are published in specialized journals both

domestically and internationally: 2 articles published international conferences; 1 article

published in Spinger Publicsher; 1 article published at the IEEE conference; 3 articles

published in international journals; 3 articles published in domestic magazines are counted

in the list of professor titles.



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5.2. Development direction of the thesis

In order for the research to be systematic and comprehensive, the thesis can continue to

research and develop according to the following contents:

1. Research and propose comprehensive lightning protection solutions including: Direct

lightning protection, lightning protection on signal line.

2. Study the effect of grounding system on lightning protection efficiency.

3. Study the unbalanced current distribution in parallel MOVs, in case the threshold voltage

errors is relatively large in theory.

4. Research on economic efficiency assessment after selecting solutions to install lightning

protection measures.



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- When not installing SPD, the simulation value of residual voltage at loads is shown in Table 4.3

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