MINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION LE QUANG TRUNG STUDY AND PROPOSE SOLUTIONS FOR LIGHTNING PROTECTING FOR TYPICAL SITE IN VIET NAM SUMMARY OF THE THESIS ELECTRICAL ENGINEERING Code: 62520202 Ho Chi Minh city, 6/2019 MINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY AND EDUCATION LE QUANG TRUNG STUDY AND PROPOSE SOLUTIONS FOR LIGHTNING PROTECTING FOR TYPICAL SITE IN VIET NAM SUMMARY OF THE THESIS ELECTRICAL ENGINEERING - 62520202 Scientific guide: Assoc Prof Quyen Huy Anh Assoc Prof Vu Phan Tu Ho Chi Minh city, 6/2019 CHAPTER INTRODUCTION TO THE STUDY 1.1 Reason to choose the topic Vietnam located in a humid tropical region with monsoon climate and high lightning strike density Therefore, the damage caused by lightning to people, services and the annual economy is enormous In particular, now science and technology is increasingly developing, IOT (Internet Of Thing) is applied in many fields; devices used in the field of electricity, electronics and especially in the field of telecommunications, computer networks, are sensitive to high voltage so easily damaged when there is a sudden change of electricity and voltage due to lightning Especially, nowadays, science and technology is increasingly developing, IOT (Internet Of Thing) is applied in many fields; the devices are used in field such as electricity, electronics, computer networks, and especially in telecommunications, etc which are sensitive to high voltage thus they are easy to be damaged when there is a sudden change of current and voltage due to lightning Damage caused by lightning to electrical and electronic equipment often occurs in the two following cases: - Damage caused by direct lightning strikes: Lightning strike on a structure can cause damage to property, electronic and electrical systems inside the structure and especially people - Damage caused by surge on the power line: When lightning strike near the structure or when lightning strikes directly or near power lines or service lines (main electrical wiring systems, communication lines, ) connected to the structure, the equipment inside the structure may be damaged due to overvoltage In this case, damage caused by lightning is not just to replace the equipment but more serious damage is to stop the service or lose data Specifically in Vietnam, according to statistics in 2001, for the electricity industry, there are 400 incidents that 50% caused by lightning (Tien Phong Newspaper 14/08/02) As for Posts and Telecommunications, there are 53 lightning incidents (27.13% of telecommunications incidents) causing 4,119 billion damage and the total time of disconnect due to lightning is 716 hours (Lightning protection for Vietnam telecommunication network - Shortcomings Le Quoc Tuan - Telecommunications Department, Pham Hong Mai - TTTTBD) Since 1998, together with the study of lightning protection technology and the proposed to lightning protection solutions, many organizations have implemented, as well as the establishment of companies in this field has created conditions for us to access to modern lightning protection technologies and equipment, but most of the lightning protection solutions offered in Vietnam are not general including from the assessment of the risk of damage caused by lightning to determine the required lightning protection level From that basis, the proposal of protection solution (or protection level) of appropriate lightning protection Currently, there are many projects in the world [7 ÷ 16, 18 ÷ 20] and IEC 62305-2, AS / NZS 1768, IEEE 1410, etc They have been interested in this issue However, the method of determining the risk of damage caused by lightning according to the above projects and standards has not considered the level of detailed of some coefficients and often retrieves the value from the lookup table NCS: Lê Quang Trung This leads to a method of calculating the risk of damage due to lightning, which is not suitable to the real conditions when the values of these coefficients fluctuate in a relatively wide range Especially in calculating the risk determination when considering the type of construction materials, the effect of installing power lines and shielding objects around the power lines In addition, the use of a formula to determine the value of these coefficients will facilitate the calculation and programming for calculating the risk of damage caused by lightning Therefore, the first research objective of the thesis is to study and propose methods to calculate the risk of damage caused by lightning and build a software to calculate the risk of damage due to lightning to overcome the above limitations Lightning is a natural, mutant and unusual phenomenon To assess the effectiveness of surge protection solutions on the power line has faced many difficulties Currently, the evaluation of the protection capacity of lightning protection devices is mainly based on the value of the voltage across the load and the value of this voltage must be lower than the allowed value In Vietnam, the implementation of the protective effectiveness test of a lightning protection solution on the power line according to the actual measurement method is difficult owing to limitations on specialized equipment Therefore, the research and construction of standard surge generator model and surge protection device model on the power line have the same level compared to the prototype to test the protection ability of the device for lightning surge propagation on low voltage power lines, it is necessary This is also the second research objective of the thesis Currently, in our country, the proposed solutions to install surge protection devices on the power line are mainly based on experience, preliminary calculations and not fully consider the influencing factors (lightning strike density, installation position, type of surges, current surges amplitude, ambient temperature, electrical distribution system diagram, load characteristics, ) This makes the lightning protection solutions for surge on power line are unsuitable for practical conditions in some cases Therefore, it is necessary to propose the option of installing surge protection devices on the power line and fully considering the influencing factors mentioned above This is the third research objective of the thesis For the above reasons, the thesis "Research to propose lightning protection solutions for typical construction in Vietnam" is necessary 1.2 Research purposes - Propose an improvement method to assess the risk of damage caused by lightning on the basis of applying the calculation method of damage assessment by lightning according to standard IEC 62305-2 with the calculation of some coefficients have a more detailed level of reference proposed by other standards; - Build a standard surge generator model for different types of surge currents and models of surge protection devices on low-voltage power lines for the evaluation of the protection effectiveness of lightning surge protection on low voltage power line; - Propose a reasonable lightning surge protection solution on a power line for illustration 1.3 Scope and limitations of the study - The thesis only focuses on researching and proposing methods to improve and assess the risk of damage caused by lightning and lightning surge solution on power lines for structures - When proposing lightning surge protection for the typical illustrative structure, assuming that: NCS: Lê Quang Trung + The project has been equipped with a direct lightning protection system based on the technology of early streamer emission lightning + Using high voltage shielded cable, limiting the phenomenon of electromagnetic induction caused by lightning in the structure + The structure has been equipped with standard grounding system + The signal transmission line has been equipped with a lightning protection system according to standards 1.5 Research methods - Collect and research domestic and foreign documents; - Method of modeling lightning surge generators, surge protection device in Matlab; - Methods of analysis and synthesis 1.6 Outstanding points of the thesis - Proposing improved methods to assess the risk of damage caused by lightning with a detailed level of calculation in some coefficients compared to the risk assessment method proposed by IEC 62305-2; - Proposing an improved lightning surge generator model with many different types of surge currents, surge protection devices model on low voltage power lines with high similarity compared to prototypes which apply for simulation to select and equip surge protection devices on the power lines properly; - Proposing the procedure of assessing the effectiveness of surge protection devices on low voltage power lines for a typical structure which illustrated the steps of determining the risk of lightning damage by analytical method to the application step method of simulation modeling to select parameters and location to install surge protection device on the power line to meet technical requirements 1.7 The scientific significance of the thesis - Results of assessment of risks due to lightning for illustrated structure by the improved method and method according to IEC 62305-2 standard have a significant difference in the value of risk of loss of human life ( 13%), and the risk of loss of economic value (11%) indicates the necessity of considering the level of detailed calculation in some coefficients and of which the shielding coefficient due to objects nearby structures; - Evaluate the protection effect of lightning surge protection on low voltage power line by simulation modeling method, in conditions that it is impossible to measure overvoltage due to lightning in practice 1.8 The practical significance of the thesis - Research results can be used as reference for lightning risk assessment method with more detailed calculation in some coefficients compared with IEC 62305-2, and surge protection solution on low voltage power lines for organizations, consulting companies of design lightning protection, graduate students in electrical engineering when studying the problem of overvoltage protection due to lightning on low voltage power lines NCS: Lê Quang Trung Chapter IMPROVED METHOD FOR RISK ASSESSMENT OF DAMAGES DUE TO LIGHTNING 2.1 Overview of methods for risk assessment of damages due to lightning 2.1.1 Risk assessment of damages due to lightning according to IEC 62305-2 / BS EN 62305-2 standard 2.1.1.1 Scope of application Standard IEC 62305-2 [1] / BS EN 62305-2 [4] on risk assessment is applied to structure or related services The purpose of the standard is to provide a procedure for assessment the hazards caused by lightning for a structure Once the calculated risk value is higher than the tolerable risk value, the procedure will allow the selection and application of appropriate protection measures to reduce the risk to the same or lower the tolerable risk value 2.1.1.2 Types of damage and loss due to lightning The lightning current is the primary source of damage The following sources are distinguished by the point of strike: S1is flashes to a structure; S2 is flashes near a structure; S3 is flashes to a line; and S4 is flashes near a line A lightning flash may cause damage depending on the characteristics of the structure to be protected They are as follows: D1 is injury to living beings by electric shock; D2 is physical damage; D3 is failure of electrical and electronic systems Each type of damage, alone or in combination with others, may produce a different consequential loss in the structure to be protected The following types of loss shall be taken into account: L1 is loss of human life; L2 is loss of service to the public; L3 is loss of cultural heritage; L4 is loss of economic value Damage sources, types of damage and loss according to the location of lightning strikes are shown in Table 21, Annex 2.1.1.3 Risk and risk components a Risk: The risks to be evaluated in a structure may be as follows: R is risk of loss of a human life; R2 is risk of loss of service to the public; R3 is risk of loss of cultural heritage; R4 is risk of loss of economic value b Risk components for a structure due to flashes to the structure: RA is a component related to injury to living beings caused by electric shock due to touch and step voltages inside the structure and outside in the zones up to m around down-conductors; RB is a component related to physical damage caused by dangerous sparking inside the structure; RC is a component related to failure of internal systems caused by lightning electromagnetic impulse causing problems for electrical and electronic systems c Risk component for a structure due to flashes near the structure: RM is a component related to failure of internal systems caused by lightning electromagnetic impulse causing problems for systems inside the structure; d Risk components for a structure due to flashes to a line connected to the structure: RU is a component related to injury to living beings caused by electric shock due to touch voltage inside the structure causing loss of human life; RV is a component related to physical damage fire or explosion triggered by dangerous sparking between external installation and metallic parts generally at the entrance point of the line into the structure due to lightning current transmitted through or along incoming lines; RW is a component NCS: Lê Quang Trung related to failure of internal systems caused by overvoltages induced on incoming lines and transmitted to the structure causing problems for systems inside the structure e Risk component for a structure due to flashes near a line connected to the structure: RZ is a component related to failure of internal systems caused by overvoltages induced on incoming lines and transmitted to the structure causing problems for systems inside the structure 2.1.1.4 Composition of risk components R1: Risk of loss of human life R1 = RA1+RB1+RC11)+RM11)+RU1+RV1+RW11)+RZ11) (2.1) R2: Risk of loss of service to the public R2 = RB2 + RC2 + RM2 + RV2 + RW2 + RZ2 (2.2) R3: Risk of loss of cultural heritage R3 = RB3+ RV3 (2.3) R4: Risk of loss of economic value R4 = RA42) + RB4 + RC4 + RM4 + RU42) + RV4 + RW4 + RZ4 (2.4) 2.1.1.5 Risk management a Procedure: The basic procedure for risk management is including: identification of the structure to be protected and its characteristics; identification of all the types of loss in the structure and the relevant corresponding risk R (R1 to R4); evaluation of risk R for each type of loss R1 to R4; evaluation of need of protection, by comparison of risk R with the tolerable risk RT; b Structure to be considered for risk assessment: The structure to be considered includes: the structure itself, installations in the structure, contents of the structure, persons in the structure or in the zones up to m from the outside of the structure, environment affected by damage to the structure c Tolerable risk RT: It is the responsibility of the authority having jurisdiction to identify the value of tolerable risk Representative values of tolerable risk RT, where lightning flashes involve loss of human life or loss of social or cultural values, are given in Table 23 – Annex In principle, for loss of economic value (L4), the route to be followed is the cost/benefit comparison to have a values of tolerable risk d Specific procedure to evaluate the need of protection For each risk to be considered the following steps shall be taken: identification of the components RX which make up the risk; calculation of the identified risk components R X; calculation of the total risk R; comparison of the risk R with the tolerable value R T If R ≤ RT, lightning protection is not necessary If R > RT, protection measures shall be adopted in order to reduce R ≤ RT for all risks to which the structure is subjected 2.1.1.6 Assessment of risk components a Basic equation for assessment of risk components: Each risk component RA, RB, RC, RM, RU, RV, RW and RZ may be expressed by the following general equation: RX = NX x PX x LX (2.5) Where: NX is the number of dangerous events per annum; PX is the probability of damage to a structure; LX is the consequent loss b Assessment of risk components due to flashes to the structure (S1): Component related to injury to living beings by electric shock (D1): RA = ND x PA x LA (2.6) NCS: Lê Quang Trung Number of dangerous events ND for the structure may be evaluated as the product: ND = NG x AD x CD x 10-6 (times/km2/year) (2.7) Trong đó: N G is the lightning ground flash density (times/km2/year); AD is the collection area of the structure (m2); CD is the location factor of the structure, Table 1Annex - For an isolated rectangular structure with length L, width W, and height H on flat ground, the collection area is then equal to: AD = L x W+2 x (3H) x (L+W)+π x (3H)2 (m2) (2.8) - The values of probability PA of shock to living beings due to touch and step voltage by a lightning flash to the structure, depend on the adopted LPS and on additional protection measures provided: PA = PTA x PB (2.9) Where: P TA depends on additional protection measures against touch and step voltages, Table - Annex 1; PB depends on the lightning protection level, Table - Annex Component related to physical damage (D2): RB = ND x PB x LB (2.10) Component related to failure of internal systems (D3): RC = ND x PC x LC (3.11) The probability PC that a flash to a structure will cause a failure of internal systems is given by: PC = PSPD x CLD (2.12) Where: P SPD depends on the coordinated SPD and the lightning protection level (LPL) for which its SPDs are designed, Table - Annex 1; CLD is a factor depending on shielding, grounding and isolation conditions of the line to which the internal system is connected, Table - Annex c Assessment of the risk component due to flashes near the structure (S2): Component related to failure of internal systems (D3): RM = NM x PM x LM (2.13) NM may be evaluated as the product: NM = NG x AM x10-6 (times/km2/year) (2.14) Where: NG is the lightning ground flash density (times/km2/year); AM is the collection area of flashes striking near the structure (m2), The collection area AM extends to a line located at a distance of 500 m from the perimeter of the structure: AM = x 500 x (L+W) x π x 5002 (m2) (2.15) The value of PM is given by: PM = PSPD x PMS (2.16) For internal systems with equipment not conforming to the resistibility or withstand voltage level given in the relevant product standards, PM = should be assumed The values of PMS are obtained from the product: PMS = (KS1 x KS2 x KS3 x KS4)2 (2.17) Where: KS1 takes into account the screening effectiveness of the structure, LPS or other shields at boundary LPZ 0/1; KS2 takes into account the screening effectiveness of shields internal to the structure at boundary LPZ X/Y X/Y (X>0, Y>1); KS3 takes into account the characteristics of internal wiring; KS4 takes into account the impulse withstand voltage of the system to be protected d Assessment of risk components due to flashes to a line connected to the structure (S3): 1- component related to injury to living beings by electric shock (D1): RU = NL x PU x LU (3.18) NCS: Lê Quang Trung For each section of line, the value of NI may be evaluated by: NL = NG x AL x Cl x CE x CT x 10-6 (times/km2/year) (2.19) Where: NG is the lightning ground flash density (times/km2/year); AL is the collection area of flashes striking the line (m2); Cl is the installation factor of the line, Table - Annex 1; CT is the line type factor, Table - Annex 1; CE is the environmental factor, Table Annex With the collection area AL for flashes to a line: AL = 40 x LL (m2) (2.20) Where: LL is the length of the line section (m) - The values of probability P U of injury to living beings inside the structure due to touch voltage by a flash to a line entering the structure depends on the characteristics of the line shield, the impulse withstand voltage of internal systems connected to the line, the protection measures like physical restrictions or warning notices and the isolating interfaces or SPD(s) provided for equipotential bonding at the entrance of the line The value PU is given by: PU = PTU x PEB x PLD x CLD (2.21) Where: PTU depends on protection measures against touch voltages, such as physical restrictions or warning notices, Table - Annex 1; PEB depends on lightning equipotential bonding (EB) conforming to EN 62305-3 and on the lightning protection level (LPL) for which its SPDs are designed, Table 10 - Annex 1; PLD is the probability of failure of internal systems due to a flash to the connected line depending on the line characteristics, Table 11 - Annex 1; CLD is a factor depending on shielding, grounding and isolation conditions of the line, Table - Annex 2- Component related to physical damage (D2): RV = NL x PV x LV (2.22) The values of probability P V of physical damage by a flash to a line entering the structure depend on the characteristics of the line shield, the impulse withstand voltage of internal systems connected to the line and the isolating interfaces or the SPDs provided for equipotential bonding at the entrance of the line The value of P V is given by: PV = PEB x PLD x CLD (2.23) With the value of PEB in Table 10 - Annex 1, PLD Table 11 - Annex 1; CLD Table - Annex 3- Component related to failure of internal systems (D3): RW = NL x PW x LW (2.24) The values of probability PW that a flash to a line entering the structure will cause a failure of internal systems depend on the characteristics of line shielding, the impulse withstand voltage of internal systems connected to the line and the isolating interfaces or the coordinated SPD system installed The value of PW is given by: PW = PSPD x PLD x CLD (2.25) With the value of PSPD in Table - Annex 1, PLD Table 11 - Annex 1; CLD Table Annex e Assessment of risk component due to flashes near a line connected to the structure (S4): Component related to failure of internal systems (D3): RZ = Nl x PZ x LZ (2.26) The value of Nl may be evaluated by: Nl = NG x Al x Cl x CT x CE x 10-6 (times/km2/year) (2.27) NCS: Lê Quang Trung Where: NG is the lightning ground flash density (times/km2/year); Al is the collection area of flashes to ground near the line (m2); Cl is the installation factor of the line, Table - Annex 1; CT is the line type factor, Table - Annex 1; CE is the environmental factor, Table - Annex With the collection area for flashes near a line: Al = 4.000 x LL (m2) (2.28) Where: LL is the length of the line section The values of probability PZ that a lightning flash near a line entering the structure will cause a failure of internal systems depend on the characteristics of the line shield, the impulse withstand voltage of the system connected to the line and the isolating interfaces or the coordinated SPD system provided The value of PZ is given by: PZ = PSPD x PLI x CLI (2.29) Where: PSPD Table - Annex 1; CLI Table - Annex 1; PLI is the probability of failure of internal systems due to a flash near the connected line depending on the line and equipment characteristics, Table 12 - Annex f Summary of risk components: Risk components for structures are summarized in Table 24 - Annex according to different types of damage and different sources of damage 2.1.2 Risk assessment of damages due to lightning according to AS/NZS 1768 standard 2.1.2.1 Scope This Section is applicable to the management of risk caused by lightning discharges to ground The object of this section is to give a procedure for evaluation of the risk to a structure, people and installations or equipment in, on or connected to the structure This evaluation considers mechanical damage of the structure and contents, damage and failure of equipment, potential differences causing step and touch injuries to people and fire damage that may result from the lightning discharge The procedure involves the comparison of the evaluated risk to the tolerable or acceptable limit of the risk and allows for the selection of appropriate protective measures to reduce the risk to below the tolerable limit 2.1.2.2 Types of risk due to lightning The types of risk due to lightning for a particular structure or facility may include one or more of the following: R1 is the risk of loss of human life; R2 is the risk of loss of service to the public; R3 is risk of loss of cultural heritage; R4 is risk of loss of economic value 2.1.2.3 Tolerable values of risk For each type of loss due to lightning, a value of the tolerable risk Ra needs to be specified Typical values of the tolerable or acceptable risk Ra are given in Table 29 Annex For a loss of economic value, the tolerable risk, Ra may be fixed by the facility owner or user, often in consultation with the designer of the protection measures, based on economic or cost considerations 2.1.2.4 Damage due to lightning a Causes of damage: The following causes of damage, relating to the proximity of the lightning strike, are taken into account: C1 direct strike to the structure; C2 strike to the ground near the NCS: Lê Quang Trung In order to simulate the case when the MOV is subjected to a discharge current, in case the MOV residual voltage has a maximum value (this is also the V value of MOV in the V-I characteristic given in the catalogue), the positive error will be used for modelling through expressions (3.20) V  (1  TOL / 100).10 b1b log I b 3e  log  I   b e log  I   (I  0) (3.20) Figure 3.7: Diagram of nonlinear resistor model V = f (I) of MOV 3.2.2.2 Effect of temperature on V-I characteristics T temperature affects MOV's direct service life and IMAX conductivity:  -550C ≤ T ≤ 850C: IMAXT = IMAX (3.21) 0  85 C ≤ T ≤ 125 C: IMAXT = (-2,5*T+312,5)*IMAX/100 (3.22)  T > 125 C: IMAXT = (3.23) The temperature value T is declared and calculated according to the expressions (3.21), (3.22), (3.23) in Initialization Commands in the Mask Editor function of the complete low voltage MOV model 3.2.2.3 Improved low-voltage MOV lightning protective device model on Matlab Low voltage MOV model on Matlab as shown in Figure 3.8 Figure 3.8: Improved low voltage MOV model With resistors Rs =100n, Rp =100M, inductance Ls≈ 1nH/mm, and capacitor Cp have different values for different MOV types MOV model built in Matlab as in Figure 3.9 Figure 3.9: Low voltage MOV NCS: Lê Quang Trung 28 Using Mask Editor to declare variables in Parameters: Figure 3.10: The variable declaration dialog and the Initialization dialog box of the low voltage MOV model Where: Vc is the MOV maximum voltage (RMS value), which is standardized by the manufacturer and is the base value for selecting the MOV value corresponding to other voltage networks: 230V, 275V, 440V and 750V; Imax is the amplitude value of the 8/20 µs surge current that MOV can tolerate, the amplitude value is normalized by the manufacturer and is the base value for selecting the MOV type corresponding to the current surge tolerance different as: 2.5kA, 4.5kA, 6.5kA, 8kA, 25kA, 40kA, 70kA and 100kA The two parameters Vc and Imax above to classify MOV, corresponding to different MOVs will have different values of L, C and b1, b2, b3 and b4; TOL is the error (%) of the threshold voltage of MOV and usually has a standard value of 10%, 15%, 20%; T is the MOV temperature measured in ºC and has a value between -55 and 125ºC; N is the number of MOV elements in the lightning protective device In Initialization, enter the value of the model's input parameters Write a program to access the values L, C, parameters b1, b2, b3, b4 and calculate the value of the V_array_input voltage array according to the I_array_output current array through the expression (3.19) according to MOV's V-I characteristic Two arrays V_array_input and I_array_output declare for the Look-up Table block of the nonlinear resistor element model, which shows the V-I relationship according to the expression (3.20) of MOV, calculated in advance by the program by the command: I_array_output=[0.0000001 0.000001 0.00001 0.0001 0.001 0.01 0.1 10 100 300 1000 2000 5000 10000 20000 40000 100000 1000000]; V_array_input=(1+TOL/100)*10.^(b1+b2*log10(I_array_output/N)+b3*exp(log10(I_array_output/N))+b4*exp(log10(I_array_output/N))); Complete the model building steps in Mask Editor, finally get the complete model of the low voltage MOV lightning protection device Input parameters of Model 3.11: NCS: Lê Quang Trung 29 Figure 3.11: Input parameter box of low voltage MOV model 3.2.2.4 Evaluation of lightning protective device model with 8/20µs surge current Test circuit to meet the low voltage lightning protective device model under the influence of 8/20µs surge current shown in Figure 3.12 Figure 3.12: Simulation diagram of low voltage lightning protective device a Simulate with low voltage lightning protective devices of SIEMENS: There are technical parameters presented in Table 3.4 with 8/20 μs surge currents 3kA at temperatures of 28 °C and 100°C respectively Table 3.4: Technical parameters of low voltage lightning protective device of SIEMENS Types AC max voltage S14K320 S20K320 320 320 Surge current of / 20μs max (A) 4500 8000 Errors of MOV voltage (%) 10 10 Maximum discharge voltage with surge of 8/20μs 3kA 1250 1200 Table 3.5: Simulation results of lightning protective devices of SIEMENS at 28 oC and 100oC Residual voltage value on MOV According to catalouge (V) According to model (V)_Vrmod Errors (%)_∆V NCS: Lê Quang Trung S14K320 28oC 100oC S20K320 28oC 100oC 1250 1384 1200 1208 1257 1389 1186 1209 0.6 0.3 1.2 0.08 V  Vrcrat V%  r mod 100% Vr mod 30 b Simulate with low voltage lightning protective devices B32K320 and B60K320 of EPCOS: The specifications presented in Table 3.6 with 8/20μs surge have a amplitude of 5kA at 28°C and 100°C respectively Table 3.6: Specifications of EPCOS low-voltage lightning protective device Types AC max voltage B32K320 B60K320 320 320 Surge current of 8/20μs max (A) 25 70 Errors of MOV voltage (%) 10 10 Maximum discharge voltage with surge of 8/20μs 5kA 1200 1050 Table 3.7: Results of comparing and simulating EPCOS lightning protective devices at 280C and 1000C Residual voltage value on MOV According to catalouge (V) According to model (V)_Vrmod Errors (%)_∆V B32K320 100oC 1200 1248 28oC 1198 1252 1052 1131 0,2 0,3 0,2 0,71 28oC B60K320 100oC 1050 1123 Comment: Through the simulation results of the model of low voltage lightning protective device for MOV types of manufacturers as shown in Table 3.5 and Table 3.7, the model results of improved low voltage lightning protective device there are the error values within the permitted range of MOV specified (residual voltage error on the model compared to manufacturer's data with a maximum value of 1,2%, lowest value is 0,08%) The input parameters of the model are relatively simple, completely provided by the manufacturer 3.2.2.5 Test residual voltage of lightning protective device from AXOS8 surge generator at laboratory C102 of Ho Chi Minh City University of Technology and Education and model Table 3.8: Technical parameters of MFV 20D511K lightning protective devices on low voltage power line AC max voltage (V) Surge current of / 20μs max (A) (kA crest) Errors of MOV voltage (%) Temperature (°C) 320 6,5 10 28 Perform simulation on Matlab using 8/20µs surge current with amplitude of 3kA for the results of response of MFV 20D511K low voltage lightning protection devices, residual voltage of MFV low voltage lightning arresters 20D511K when simulating at 280C and 1000C Table 3.9: Comparison of residual voltage between actual experiment and model Residual voltage value on MOV According to the actual device (V) According to model (V)_Vrmod Errors (%)_∆V 28oC 1190 1103 100oC 1240 1181 Comment: From the experimental results, the residual voltage difference between the improved low-voltage lightning protective device model on Matlab and the lightning surge NCS: Lê Quang Trung 31 generator is actually tested for the MFV 20D511K low-voltage lightning protective device at 280C is 7%; at 1000C is 5% 3.3 Conclusion Building a lightning surge generator model for types of lightning surge current with errors meeting the error of the standard lightning impulse (10%) The simulation results for lightning surges, the maximum error value of peak current value is 0,03%, the front time is 0%, the tail time is 3,71%; Building a model of lightning protective equipment on the low voltage in Matlab with high similarity with the prototype, specifically: About the structure of the device in the model, maximum voltage, surge current maximum, threshold voltage errors, temperature Results of residual voltage test between simulation modelling and residual voltage from manufacturer's catalogue: Maximum value is 1,2%, lowest value is 0,08% Electrical test results residual voltages between MFV 20D511K and MFV 20D511K models is tested at laboratory C102 of Ho Chi Minh City University of Technology and Education at the temperature of 280C, the errors is 7%, at 1000C the error is 5% NCS: Lê Quang Trung 32 Chapter SOLUTION FOR SELECTION OF SURGE PROTECTIVE DEVICE ON LOW VOLTAGE POWER LINE FOR TYPICAL STRUCTURE 4.1 Overview 4.2 Procedure of calculation and selection of surge protective devices on the power line 4.2.1 Risk assessment procedure for typical structure The procedure of risk assessment for typical structure consists of 11 steps and shown in Figure 4.1 Step Identify the structure to be protected Step Identify the types of loss relevant to the structure Step Identify and calculate the risk components R > RT Step No Structure is protected Yes Step The structure needs to install lightning protection system Step Yes Is LPS installed? No Step Select an adequate types of LPS Yes Step IS SPM installed? Step 10 Select other protection measures Calculate new values of risk components No Step Select an adequate types of SPM Step 11 Note: RT : tolerable risk; LPS: Lightning Protection System; SPM: Surge Protection Measures Figure 4.1: Risk assessment procedure for telecommunication site Risk assessment process for telecommunication stations consists of 11 steps as follows:  Step 1: Identify the characteristics and parameters of telecommunication site to be protected against lightning: structure dimensions; height of adjacent antenna tower; level of shielding by other structure nearby; lightning density; fire protection measures; the number, installation method and length of the service line connected to the structure; existing lightning protection measures, etc  Step 2: Calculate the risk components for a structure due to direct and indirect lightning strike From there, calculate the risk of loss of human life R1 and the risk of loss of service R2 for the structure  Step 3: Identify and calculate risk components for each type of loss  Step 4: Calculate the total component risk value for each type of loss and compared to the tolerable risk value according to IEC 62305-2 [1] If the risk calculation value for each NCS: Lê Quang Trung 33 type of loss is less than the tolerable risk, the structure is protected, and vice versa, lightning protection system is required to be installed  Step 5: The structure needs to install lightning protection system  Step 6: Consider whether the structure is equipped with LPS or not? Move to Step if the structure is equipped with LPS Move to Step if the structure is not equipped with SPM  Step 8: Consider whether the structure is equipped with SPM on the power line or not? Move to Step if the structure is not equipped with SPM Move to Step 10 if the structure is equipped with SPM  Step 9: Select and equip suitable SPM on the power line  Step 10: Select other protection measure  Step 11: After installing LPS, the appropriate level of protection or additional installation of LPS has the appropriate level of protection; If the SPM installation has the appropriate level of protection or additional installation of SPM with the appropriate level of protection, return to Step to calculate the risk assessment to check whether the building has been protected 4.2.2 The selection and testing procedure for SPD After assessing the risk due to lightning, the procedure of selection and testing the protection of SPDs consists of steps and as shown in Figure 4.2 Step 1: Build the model of electricity distribution network Step 2: Select SPD on power line Step 3: Select the location of SPD on power line Step 4: Simulate the response of SPD on the power line Step 5: No Check the protection voltage: UP≤(1200+Un), for electrical equipment; UP≤1.5Un , for electronic devices Step 6: Yes Structure protected from the risks of surge on the power line Note: with UP is protection voltage of the device; Un is the nominal voltage of the system Figure 4.2 Procedure for selection and testing the protection of SPD on the power line NCS: Lê Quang Trung 34 ▪ Step 1: Based on the single line diagram of power line for the structure, the model of electricity distribution network will be built on the Matlab ▪ Step 2: Select the SPD on the power line ▪ Step 3: Select the location of the SPD on the power line: Main distribution panel; subdistribution panel, at feed of load ▪ Step 4: Simulate the response of the SPD on the power line with the surge generator model by generating surge propagation at different positions on the power line with the lightning current depends on the location of the structure corresponding in Figure 4.3 and examine the protection voltage at the terminal of the device in each case Figure 4.3: Standard lightning surges ▪ Step 5: Check the protection voltage UP : - According to IEC 61643-1 for electrical equipment, protection voltage: UP  (1200  Un ) (4.1) - According to AS 1768 for electronic devices, protection voltage (Figure 4.4): UP  1,5Un (4.2) - If the protection voltage is not satisfied (1) and (2), go back to Step Figure 4.4 Typical voltage/time tolerance of electronic devices, computers ▪ Step 6: Conclusion of the structure has been protected from the risks of surge on the power line NCS: Lê Quang Trung 35 4.3 Calculation for typical structure 4.3.1 Characteristics of the structure The actual structure investigated in this article is a telecommunication site (TS) in Long Thanh district, Dong Nai province, Vietnam, built in reinforced concrete, lightning density of the area is 13,7 times/km2/year and no other higher structure nearby The antenna tower is built in steel, 4m from the station and has a height of 50m - The length of the power line and telecom lines connected to the station are 500m and 1000m, respectively - The lightning protection system has been installed and the telecom lines have been installed with SPM - The power line is not installed with SPM - The TS should be assessed for the risk of loss of human life and the risk of loss of service due to lightning to select SPD on the power line 4.3.2 Assess the risk of damage due to lightning for telecommunication site Risk assessment procedure for telecommunication site is implemented as shown in Figure 4.1  Step 1: Identify the characteristics and parameters of structure to be protected: Table of characteristics of surrounding buildings and environment, characteristics of power lines, and characteristics of telecommunication lines are presented in Appendix 11  Step 2: For telecommunication site, there are two types of damage caused by lightning: human loss (R1) and service loss (R2):  Step 3: Calculate the risk components related to R1 and R2 due to lightning caused to the telecommunication site  Step 4: Compare the values R1 and R2 with RT1 and RT2 Table 4.1: Comparing the value of risk values with risks according to the standard [1] Risk value according to Comparison results The calculated risk value standard [1] R1= 3,88.10-6 RT1= 10-5 R1RT2 ⇒ Risk value R2 is higher than the standard risk value  Step 5: The building should be installed with lightning protection system  Step 6: Consider whether the building is equipped with LPS? It is considered that the building has been installed LPS with SPD with LPL level I protection level, and moved to Step  Step 8: Consider whether the construction is equipped with SPM or not? The struture has not been equipped with SPM on the power line, move to Step  Step 9: Select and install SPM for power line: SPD has LPL has protection level II (PSPD/P=0,05.0,02=0,001)  Step 10: Recalculate new component risk values After recalculating the component risk values, go back to Step to calculate the risk for R and R2: NCS: Lê Quang Trung 36 Table 4.2: Comparison of the risk value of components when installing SPD with risk value in standard [1] Risk value according to standard [1] -6 R1= 3,87.10 RT1= 10-5 -4 R2 = 2,137.10 RT2= 10-3 ⇒ Risk value R1 and R2 are all lower than the tolerable risk value The calculated risk value Comparison results R1 < RT1 R2 < RT2 Comment: Risk values R1 and R2 are less than tolerable risk values RT1 and RT2in IEC standard 62305-2 [1] The structure has been protected from the risk of damage due to lightning, continue to test the protection performance of SPD on the power line Comment: Risk values R1 and R2 after installing LPS lightning protection devices with SPDs have LPL level I and SPM protection levels with SPD level II LPL protection levels, RT1 risk values and The R T2 is lower than R T1 and RT2 according to standard [1], which limits the risk of damage caused by lightning On that basis, select the lightning protection measures: Select lightning protective device, select the location of lightning protective device, test the protection ability of lightning protective device on the power line after installation 4.3.3 Lightning surge protection solution on the power  Step 1: Build the power distribution network model on Matlab Based on the main power supply scheme for the telecommunication site and the summary of equipment in the station, building a power distribution diagram model on Matlab as shown in Figure 4.5  Step 2: Select surge protective device on the power line - Select level I SPD: (Cat B) - Select level II SPD: (Cat C)  Step 3: Select the location to install surge protective device Surge protective device is installed at main distribution board and sub-distribution board  Step 4: Conducting simulations to test the response ability of the surge protective device on the power line and survey the residual voltage across the load: Load AC 230V/400V, load 48V DC The lightning density at the area is 12 times/km2/year, according to ANSI/IEEE C62.41, IEC 61643 standards in Figure 4.3, simulation with lightning current surge of 8/20μs 40kA: - When not installing SPD, the simulation value of residual voltage at loads is shown in Table 4.3 Table 4.3: The protection voltage simulation values at loads, without SPD The peak of protection The peak of Rated current voltage across AC load protection voltage amplitude (V) across DC load (V) 8/20µs (kA) 40 NCS: Lê Quang Trung 38600 460 37 Figure 4.5 Power distribution network simulation diagram in Matlab NCS: Lê Quang Trung 38 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 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: NCS: Lê Quang Trung 39 - 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 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 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- and AS / NZS 1768) NCS: Lê Quang Trung 40 Chapter CONCLUSION 5.1 Research results The thesis has focused on researching to complete the main contents as follows: 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% Propose lightning surge generator model applied to 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% (