CC BY
35Lightning Risk Assessment Software Design for Photovoltaic Plants in Accordance with IEC 62305-2
Mohammad Parhamfar*
A freelance consultant in the power and energy field
Abstract — The lack of an effective protection scheme delays the integration of photovoltaic (PV) plants into distribution networks. Outdoor installation of these systems always exposes them to direct/indirect lightning strikes and consequent overvoltages. If lightning overvoltages are not limited, the PV plant equipment may be damaged. A lightning protection system (LPS) consisting of external and internal sections aims to protect the PV plant against overvoltages of the atmospheric origin. However, the lightning risk assessment for determining the need for the LPS installation and the overvoltage protection system design are complicated tasks. In the past, there was no special software for lightning risk assessment in solar power plants, and only some papers have mentioned the calculation method and software developed according to local standards. This paper develops a software application for lightning protection design of PV plants especially for risk assessment analyses according to IEC62305-2. The designed software has used a comprehensive standard compared to other software, and in addition to considering solar farms, it also covers off-grid and on-grid rooftop systems. The evaluation results show that the proposed software is a useful tool for electrical engineers and renewable energy experts who are active in the PV integration industry. Using this software, specialists will be able to easily perform complex calculations and select the suitable LPS for the projects.
Index Terms: photovoltaic, lightning protection software, risk assessment, surge protective device.
* Corresponding author. E-mail: Info@parhamfar.com
http://dx.doi.org/10.38028/esr.2022.02.0004 Received May 05, 2022. Revised July 11, 2022. Accepted July 30, 2022. Available online August 31, 2022.
This is an open access article under a Creative Commons Attribution-NonCommercial 4.0 International License.
© 2021 ESI SB RAS and authors. All rights reserved.
I. Introduction
One of the important topics of electrical engineering is the study of different aspects of renewable energies. Accessibility, free primary energy, PV modules advancement, and government incentives contribute to increased attention to the PV systems among other renewable energy sources [1]. According to the international energy agency (IEA) report, despite the COVID-19 crisis, the global PV will increase every year [2]. The safe and accurate performance of the PV systems improves their offered resilience. Therefore, the enhancement of control algorithms and protection systems ensures that the PV systems remain at the forefront of renewable energy technologies.
The design of an effective protection system has always been one of the main challenges of electrical networks. Protection system should be simple and economic and detect any abnormal condition quickly to decrease damage to the network equipment (reliability and speed). It should also isolate only the faulty section (selectivity). Due to outdoor installation, the PV systems are subjected to both overcurrent due to short-circuit faults and overvoltage of atmospheric origin. A short-circuit fault results in overcurrent on the DC/AC side of the PV power plant, which is usually detected and isolated by the miniature circuit breakers (MCBs) or molded case circuit breakers (MCCBs). A ground fault is detected by the ground fault protection device. On the other hand, lightning may result in overvoltages in the PV system equipment. In some research, computer programs for risk calculations in solar power plants have been developed based on local and old standards [3]. Software developed by the world's largest companies does not provide the evaluation of solar power plants separately [4, 5].
Little work has been done as yet to design software to assess the risk of lightning strikes on photovoltaic installations. In [6], a comprehensive review of the superior modeling methods of PV systems during lightning strikes is presented. The paper displays various platforms to simulate the transient effects of lightning strikes on PV systems. This paper also gives some recommendations
about the modeling methods and protection of PV systems during lightning strikes. A computer program for lightning strike risk assessment and design of lightning protection system for the photovoltaic system is also proposed in [7].
In this paper, a developed software for risk assessment calculation according to IEC62305-2 and LPS design for PV plants is introduced and investigated. By using this software, an engineer can evaluate various lightning protection system designs in a short time. This software helps to understand the concepts of lightning protection design and to view the result of their design without performing numerous calculations.
II. Fundamentals of Lightning Protection System Design for PV Systems
1.1. Basic Principles
Lightning overvoltage protection is one of the main modules of protection schemes of PV power plants, especially in countries with stormy and cloudy climates [8]. If an overvoltage condition is not detected and isolated, the PV system equipment may be damaged, which will lead to an increase in the return time of investment. PV systems are subjected to both direct and indirect overvoltages. In the former case, the lightning strikes the PV structure while in the latter case, lightning falls near the structure, or signaling/electrical lines entering the structure are affected by the lightning. When lightning strikes near the structure, the resultant variable magnetic field induces the overvoltages on the building circuit (inductive coupling) while when lightning strikes the entering lines, through the line characteristic impedance, the lightning current results in overvoltage (resistive coupling). If an overvoltage exceeds the impulse withstand voltage of equipment, it is damaged and even poses a risk of fire hazard.
An LPS consists of external and internal protection systems. The external protection system protects the PV system against direct strikes by using the air-termination system (ATS), down-conductor system, and earth-termination system for intercepting the lightning, conducting the current to the ground, and distributing the current in the ground, respectively. The internal protection system protects the PV system against sparking inside the structure by implementing equipotential bonding or keeping a separation distance between the LPS components and other conductive elements of the structure.
In the case of direct lightning, there can be three conditions [9]:
1. Rooftop PV plant without LPS: If the PV installation does not change the building outline, the frequency of the threat does not change, and consequently, no measures are required. Otherwise, the risk assessment should be performed.
2. Rooftop PV plant with LPS: If the PV plant does not significantly change the building outline and the
minimum distance d between the available LPS
and PV system is greater than safety distance s, no
measures are required. However, if d is less than s , the LPS should be extended and connected to the PV metal structure. If the PV installation changes the building outline, a new risk assessment is required. 3. Ground PV plant: In this case, there is no fire threat due to direct strike.
In the case of indirect lightning strikes, the circuits are shielded to decrease the magnetic field. In addition, the module conductors are twisted and the live conductors are kept near to protective earth conductor to decrease the induced circuit turn area.
Even for limited overvoltages, surge protective devices (SPDs) are required to discharge them to the ground. An SPD presents a high impedance at the nominal voltage while its impedance significantly decreases in the case of an overvoltage, making a low-impedance path to the ground. Thus, the lightning current is discharged to the ground and the PV plant equipment is protected against overvoltage.
1.2. Risk Assessment Based on IEC 62305-2
According to IEC 62305-2 standard [7], risk assessment requires that source of damage, type of damage, and type of losses be determined. The primary source of damage is the lightning current. There are four damage sources: lightning strike to a structure (S1), lightning strike near a structure (S2), lightning strike to a line (S3), and lightning strike near a line (S4). Depending on the structure characteristic, there are three damage types: electric shock and the resultant injury to living beings (D1), physical damage (D2), and failure of electronic and electrical systems (D3). There are four types of loss in the structure resultant from various types of damage: human life loss, including permanent injury (L1); public service loss (L2); cultural heritage loss (L3), and economic value loss (L4).
The total potential risk in a structure is calculated as [8] R = Ri + R2 + R3 + R4, (1)
where Rj is the risk of Li as
Ri = Ra + RB + RC + RM + RU + RV + RW + RZ, (2) R2 is the risk of L2 as
R2 = RB + RC + RM + RV + RW + RZ, (3)
R3 is the risk of L3 as
R4 is the risk of L4 as
R3 = RB + ^
(4)
R4 = Ra + RB + RC + RM + RU + RV + RW + R* (5)
and
Ra is related to the injury to living beings resulting from step and touch voltages in the case of a direct strike, RB is related to the physical damage resulting from sparking inside the structure, which triggers explosion or fire in the case of a direct strike, RC is related to the internal system's failure resulting from lightning electromagnetic impulse (LEMP) in the case of a direct strike,
Flashes to the line Rv and Rw
Flashes near the structure Rm
Flashes to PV system Rg and Rc
Flashes near the line RÎ
Fig. 1. Risk components of a PV system.
• RM is related to the internal system's failure resulting from LEMP in the case of indirect strike,
• Ru is related to the injury to living beings resulting from step and touch voltages in the case of a strike to a line connected to the structure,
• RV is related to the physical damage resulting from sparking between metallic parts and external installation due to transmitted lightning current through incoming services in the case of a strike to a line connected to the structure,
• RW is related to the internal systems' failure resulting from induced overvoltage on incoming lines and transmitted to the structure in the case of a strike to a line connected to the structure, and
• RZ is related to the internal systems' failure resulting from induced overvoltage on incoming lines and transmitted to the structure in the case of a strike near a line connected to the structure.
All risk components of RA to RZ are calculated as
Rx = N x PX x Lx, (6)
where Nx is the number of dangerous events (Year 1), Px is the structure damage probability, and Lx is the consequent loss. Due to space limitation, the detailed procedure of determining Rx is not presented; this procedure is available in [9].
If R < RT where RT is the tolerable risk, there is no need for lightning protection. While, if R > RT, protection measures should be adopted in such a way that R < RT for all risks threatening the structure. The tolerable risk for human life or permanent injury loss, public service loss, cultural heritage loss, and economic loss are 10-5, 10-3, 10-3, and 10-3 (Year-1), respectively. 1.3. Risk Assessment for PV Plants
In the risk assessment of PV systems, there is no need to consider some risks [10]. Since the structure of PV
systems is nonflammable, the fire hazard can be neglected. In addition, most of the rooftop PV systems are installed on small buildings; thus, the probability of a direct strike is low. Moreover, there are no people in a large PV power plant. Consequently, human life loss risk (R1) is not considered. On the other hand, due to the small capacity of PV systems, even in the case of PV power plants, the public service is not affected by their failure. Thus, risk R2 can also be neglected. Moreover, the PV systems are not usually installed in historical places; thus, cultural heritage loss risk (R3) can be neglected.
Consequently, economic value loss is the only risk that should be considered in the risk assessment for PV systems. The risk components of R4, RA and RU are related to the cases where animals may be lost. Due to installing PV systems on rooftop or enclosing the PV power plants, these risk components are neglected and only RB, RC, RM, RV, RW, and RZ are considered. According to [8], among these components, RM, RW, and RZ are more relevant than others in the case of rooftop PV systems. Figure 1 shows the risk components of a PV system.
Since there is only one risk in the risk assessment of PV plants, R = R4. The following measures can be implemented to decrease the total risk of a PV system to a tolerable level:
• reduction in RW and RZ by installing a coordinated SPD in the low voltage (LV) line entering the building;
• reduction in RM by installing a coordinated SPD in the DC line of the PV system.
In the case of a PV power plant, in addition to the above-mentioned protections, an external lightning protection system can be installed to reduce R. Figure 2 shows the flowchart of the risk assessment for PV systems.
The above section was aimed at calculating Risk assessment for solar farms. In addition, the developed software can be used to make calculations for off-grid and
Fig. 2. Flowchart of risk assessment for solar farms.
# Lightning Protection System Designer for Utility Scale On Grid PV Plants
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment Externa! Lightning Protection System Surge Protective Device About Us
Adjacent Structure Power Data
Structure Data Width (W)M Length (L> [m] Height (H) 5m]
SOOm
45
25
15
(*) With Agacent Structure O Without Adjacent Staicture
Width <WJ) [m] Length (U) [mj Height (HJ) [m]
Accent Structure Tel Data Width (WJ) H Length (LJ) (n] Height (HJ) M
A;>
w
100
Une and Environmental Data Soil resistance(Ohm/m) Thunderstorm Days (TD) [per year] | Lengh of Td Une (LL1) [m] Lengh of Pow Dne (LL2) H
1000
1000
LV power, telecommunication or data line (CT=1) HV power (With HVA.V transform er)(CT=0.2)
Type Of Line power
Are both lines the same path''
Structure Location (CD)
HV
Yes
Structure surrounded by higher objects
Adjacent Stmctue Location (CDj) ajrroinded by higher objects
Tel Line Installation (CM )
.Aerial
Pow Une Installation (CÍ2 ) Une Environmental (CE)
Aerial
Rural
Calculate
7
e:
40 m Ai, - 4000 m
L
U
Results N3 AD ADJ1 ADJ2 ND NDJ1 NDJ2 NM NL1 NU NL2 N12
10
13786 725124
996 858347
1031.858347
0.0344668
0.0005159
0.0024921
8.55
0.4
40
OOS
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us
Tel Line Input Data
Power Line Input Data
Characteristics of Structured B) Structure protected by LPS (III) Probability PSPD
Better protection characteristics (0.004)
External Line Type (CLDCLI) Does special shield exist' Type of Internal Wiring (KS3) Value of Probability PEB Routing. Shielding (PLD) Withstand Voltage UW |kVJ Une Type
Values d Pipbability (PTA) Values of Prpbability (PTU) Mesh Width (wm1) [m] Mesh Width (wm2) hi
Results PA
PB
PCpow
0.2
0.2
0.004
PMPow 0.00059
Aenal line unshielded (Undefined) Yes
Unshielded cable - no routing precaution in order to avoid I
No equipotential SPD v>
Aerial or buried line, unshielded or shielded whose shield is i v
2.5
Power lines
Electrical Insulation of exposed parts
Electrical Insulation
Characteristics of Structured B) Probability PSPD External Line Type (CLD) Does special shield exist7
Type of Internal Wiring (KS3) Value Of Probability PEB Routing. Shielding (PLD) Withstand Voltage UW |kV] Line Type
Values of Pipbability (PTA) Values of Prpbability (PTU) Mesh Width (wml) [m] Mesh Width (wm2) [m]
Structure protected by LPS (IV|
No coordinated SPD system
Aerial line unshielded (Undefined)
Yes
Unshielded cable - no routing precaution in order to a voie v
No equipotential SPD
Aerial or buried line, unshielded or shielded whose shield i: v
Telecommunication lines
No Protection measures
No Protection measures
Calculate
PUpow PVPow PWpow
0.01
0.004
PC Tel PMTel PUTel
0.9216
PWTel PZTd
PZpow 0.0012
PVTd 1
Industrial. Commercial
Hospital, industrial, museum, agricultural
Number of Dangerous Events Probability of Damage Amount of Loss Buk Assesment External Lightning Protection System Surge Protective Device About Us Input Data
Physical damage (LF1) Physical damage (LF4) Failure qf internal System (Lol) Failure of internal System (Lo4) Kind of Special Haiardfa) Provisions (jp) Amount of risk (pf)
Risk of explosion
Risk of explosion
No special hazard
No provisions/ Risk of explosion
Explosion, Zones 0,20 aid solid explosive
Type of surface ft)
The value of animals in the zone (Ca)
Agricultural, Concrete
Due to simplification is not taken into account h the calcdations
The value of building relevant to the zone (Cb) Due to simplification is not taken into account in the calculations
The value of content in the zone (Cc) The value of internal systems (Cs) Number of persons in the îone (Nî) Total nunber of persons in the structure(Nt)
Due to simpSfication is not taken into account in the calculations
Due to simplification is not taken into account m the calculations
Time in hours per yearforthe persons are present in the Zone(ti)
8760
Calculate
Results LAI LB1
LC1 LM1
0.0001
002
0.1
01
LU1 LV1 LW1 LZ1
0-0001 Ö'02
0.1
0.1
LA4 LB4
LC4 LM4
00001
0.5
0.1
ÖT
LU4 LV4
LWJ
LZ4
00001
0.5
01
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About
Is there animal protection '
Type of Project
R1 R 2 R4
Yes
Off Grid Roof top
4 339655740926 PV plant requires protection and R1 is not appropriate
0.523887553 PV plant requires protection and R2 is not appropriate
5.035211640926 PV plant requires protection and R4 is not appropriate
Calculate
Flashes № PV system R. and Rc
Fljitioi to the line Rv and R„
flash» near the line
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us Air-Termination System Input Data
Height Ih) [mj Protection Diameter (D) [m] 30 (Class II) Length (L) 1m] Width (W)
Overlap Percentage [7.]
50
25
Calculate
Results
Rp M
Coverage Area [rrr ]
NW
NL
N total
14.96663
703716797
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us SPD Protection
NG [HashAm2/yesr3 Type of installation
LM
Kj_
Individual residential premises 25
Calculate
Results Lent [m]
Answer
SPD protection is inquired
11 5
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us
Adjacent Structure Power Data
100
Structure Data/Solar Farm Width (W)[m] Length (L) [m] Height (H) Jri]
500 m
200
Width (WJ) [m] Length (U) [mj Height (HJ) [m]
Acjjdcent Structure Tel Data
(§) With Agacent Structure O Without Adjacent Structure Width (WJ) fr]
Length (LJ) fcn]
An
w
U
tzt
do m Al - 4000 m
r
c1
Height (HJ) M
Line and Environmental Data Soil resistance (Ohm/m) Thunderstorm Days (TD) [per year] Lengh of Tel Line (LL1) [m] Lengh of Pow Lhe (LL2) [m]
Type Of Line power
Are both lines the same path7
Structure Location (CD)
100
10
1000
900
LV power, telecommunication or data line (CT=1) HV power (With HV/LVtransformer)(CT-0.2)
HV
No
Isolated structure: no other objects in the vicnty Adjacent Structure Location (C Dj) i^ated structure no other objects in the vicinity Tel Line Installation (CM ) ^^
Pow Une Installation (CI2) Line Environmental (CE)
Aerial
Rural
Calculate
Results N3 AD ADJ1 ADJ2 ND NDJ1 NDJ2 NM NL1 NU NL2 N12
25654.4&9005
996.858347
1031.858347
0.0256545
0.0009969
0.0002064
1.09
0.04
0.0072
0.72
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us Power Line Input Data Tel Line Input Data
Characteristics of Struct ure(PB) Structure not protected by LPS
Probability PSPD
No coordinated SPD system
Characteristics cf Stiucture(PB) Structure not protected by LPS Probability PSPD No coordinated SPD system
External Line Type (CLD-CLI) Aenal Ine unshielded (Undefined) Does spatial shield exist'
NO
External Line Type (CLD) Does special shield exist?
Shielded aerial line (Shield not bonded to the same bondr v
Yes
Type of Internal Wiring (KS3) Value of Probability PEB Routing, Shielding (PLD) Withstand Voltage UW [kV] Line Type
Values of Probability (PTA) Values of Probability (PTU) Mesh Width (wm1) fm] Mesh Width (wm2) (m]
Results PA
PB
PCpow PMPow
Unshielded cable - routing precaution in orderto avoid larg<
No equipotential SPD
Type of Internal Wiring (KS3) Shielded cables and cables ruining in metal conduits v Value rf Probability PEB
No equipotential SPD
Aerial or buried line, unshielded or shielded whose shield is i v
1.5
0.017778
Power lines
No Protection measures
No Protection measures
PUpow
PVPow
PWpow PZpow
06
Routing. Shielding (PLD) Withstand Voltage UW JkV] Line Type
Values of Pipbability (PTA) Values of Pipbability (PTU) Mesh With (wm1) [m] Mesh Width <wm2) [m]
Calculate
PCTel PMTel PUTel PVTel
Aerial or buried line, unshielded or shielded whose shield i:
1
Telecommunication lines No Protection measures
No Protection measures
PWTel PZTel
01
to o to to
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us Input Data
Physical damage (LF1) Physical damage (LF4) Failure of ntemal System (Lo 1} Failure of internal System (Lo4) Wnd of Special HazanJjhi) Provisions (ip) Amount of risk (rf)
Type of surface it)
The value of animals in the zone (Ca) Due to simplification is not taken into account in the calculations
The value of faulting relevant to the zone (Cb) Due to simplification is not taken into account in the calculations The value of content in the zone (Cc) Due to simplification is not taken into account in the calculations
Industrial, Commercial
Hospital, industrial, museum, agricultural
Other
Hospital, industrial, off i ce. hotel, commercial
No special hazard
No provisions ''Risk of explosion
Fire, Low
5cm Asphalt, 15 cm Gravel
Calculate
Results LAI LB1
LCI LM1
2E-05
0
LUI
LV1
LW1 LZ1
2E-Q5 0
LA4 LB4
LC4 LM4
0 0005
0.01
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us
Is there animal protection ? Type of Project
R1 R2 R4
No
Solar Faim
R1 is appropriate
R2is appropriate
00095479321
PV plant requires protection and R4 is not appropriate
Calculate
Flaslt« to the line R„ and Ry,,
Number of Dangerous Events Probability <rf Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About Us Power Line Input Data Tel Line Input Data
Characteristics of StructurelPB)
Probability PSPD
Structure protected by LPS (If)
Charactenstics of Structure(PB) Structure protected by LPS I Probability PSPD II
External Une Type (CLD-CLI) Aenal line unshielded (Undefned) Does spatial shield exist7
NO
External Line Type (CLD) Does 3peaal shield exist?
Shielded aerial line (Shield not bonded to the same bondir v
Yes
Type of Internal Wiring (KS3) Value of Probability PEB Routing. Shielding (PLD) Withstand Voltage UW [kV] Une Type
Values of Prpbability (PTA) Values of Prpbability (PTU) Mesh Width (wml) [m] Mesh Width (wm2) [m]
Results PA
PB
PCpow PMPow
Unshielded cable - routing precaution in order to avoid larg<
No equipotential SPD v |
Aenal or buried line, unshielded or shielded whose shield is i v
Type of Internal Wiring (KS3) Shielded cables and cables mnrnng in metal conduis Value Of Probability PES
No equipotential SPD
1.5
0.05
0.05
0.02
000035G
Power lines
No Protection measures
No Protection measures
Routing. Shielding (PLD) Withstand Voltage UW [kV] Line Type
Values of Prpbability (PTA) Values of Prpbability (PTU) Mesh Width (wml) [m] Mesh Width (wm2) |m]
Calculate
PUpow
PVPow
PWpow PZpow
002
0012
PCTel PMTel PUTel PVTel
0.02
Aerial or buried line, unshielded or shielded whose shield ir v
Telecommunication lines
No Protection measures
No Protection measures
PWTel PZTel
0.02
0.002
Number of Dangerous Events Probability of Damage Amount of Loss Risk Assesment External Lightning Protection System Surge Protective Device About
Is there animal protection'
Type of Project
RI R2 R4
Nq
Solar Farm
RI is appropriate
R2 is appropriate
0.0002150658725
R4 is appropriate
Calculate
Fig. 14. The Risk Assessment Menu with new calculation.
D^ File Edit View Git Project Build Debug Test Analyze Tools Extensions Window Help Search (Ctrl+Q)
o - 0'^Ui
Release »
Any CPU
► SRM "
\E -4 1r I- + ■=! |I -H- il 1*1 I ïî li ii :=:
1/1 ft) .'I. m Toolbox * -a <
Search Toolbox P »
J< -O O ^ All Windows Forms
íí •t Pointer
i r BackgroundWorker
CT Û 3" BindingNavigator
X B' BindingSource
(¡g Button
0 CheckBox
□ <— D — a — Checked Li stBox
ColorDialog
E CornboBox
m ContextMenuStrip
g': Data Grid View
DataSet
n DateTimePicker
53 Directory Entry
p Directory Searcher
□ DomainUpDown
0 ErrorProvider
B EventLog
S3 FileSystemWatcher
ÎS-Î FlowLayoutPanel
El FolderBrowserDialog
m FontDialog
a GroupBox
'Scale Or Grid PV Plants Amountof Loss Risk Assesment External Lightning Protection System Surge Protective Device AboutUs
\S¡ II S3
ture Power Data
.500 m
:ure Tel Data
Ad 3H
W
J
Al = 40 m A, M 4000 I
J- H,
e
w,
LV power, telecommunication or data line (CT=1) HV power (With HV/LV transformer)(CT=0.2)
Results NG
AD
ADJ1
ADJ2
ND
NDJ1
NDJ2
Fig. 15. Designed Software Window by Usual Studio.
m I " ?
File Edit View Git Project Build Debug Test Analyze Tools Extensions Window Help Search (Ctrl+Q)
-o ft
& y
Release
Any CPU
► SRM
Iff 1
Forml.cs ^ X
Ef] SRM
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
Form1.cs [Design]
1550
1 nn n/
IjSRM.Forml
t ®Bbuttor4_CI i ck(o bj ect se n d e
//Cb = double.Parse(textBoxl8.Text);
//Cc - double.Parse(textBoxl9.Text);
//Cs = double.Parse(textBox20.Text);
//Ct = Ca + Cb + Cc + Cs;
double rz= double.Parse(textBox21.Text);
double nt= double.Parse(textBox56.Text);
//////////////////////////////////////////////////////////
III
double sum = Ca + Cb + Cc + Cs; Lf2= Math.Pow(10j -1); Lo2 - Math.Pow(10j -2);
LV2 = LB2 = rp * rf * Lf2 * (nz / nt) ; Lc2=LM2=Lw2=Lz2= Lo2* (nz / nt) ; LB4 = LV4 = Math.Round(rp * rf * lf4 * 1), 6); Lc4 = LM4 = Lw4 = Lz4 = Math.Round(lo4 * 1, 6); double LT = Math.Pow(10,-2); tz = double,Parse(textBox65.Text); LA4 = rt * LT * (nz / nt) * (tz / 8760); Lu4 = LA4; //////////////////// ///parti
LB1 =LV1 = Math.Rouind(rp * rf * Lfl * Hz
Lcl = LM1 = Lwl = Lzl = Math.Round(Lol *
// double LT = Math.PowilOj -2); -
Fig. 16. Part of the Sofhvare Codes.
(1) * (nz / nt) * (tz / 8760)j 6); * (nz / nt) * (tz / 8760), 6);
on-grid rooftop projects. In off-grid solar systems, risk R3 can be excluded because they are rarely used in heritage buildings. In systems connected to the solar network, we can eliminate the risk of public services and heritage buildings (R2, R3). Briefly, the following parameters have been considered for various solar power plants:
1. Solar Farms: R4.
2. Off-grid projects: R1+R2+R4.
3. On-grid rooftop projects: R1+R4.
1.4. External Lightning Protection System
As mentioned in the previous subsection, an external LPS may be required to reduce the total risk of a PV power plant. One of the most important parts of the external LPS is the air-termination system (ATS), which can consist of catenary wires (horizontal conductors), rods, and meshed conductors (Faraday cage) [11]. The ATS prevents direct flashes on the PV structure. The proper design of ATS reduces damage to the area to be protected. There are three methods to determine an ATS protection area [12]:
• Rolling sphere method: It is a universal technique, especially for complicated applications.
• Protective angle method: It is proper for simple-shaped buildings, but it has a limitation of the ATS height.
• Mesh method: It is suitable to protect the plane surfaces (for buildings).
The rolling sphere technique is an acceptable method for designing ATS. In this method, given the lightning rod height and highest piece of rooftop power plant project, the protective radius rp of each rod is calculated as follows [13]:
r, +V2hers - hl> hr ^ rS
rp =•
J2rK -h -J2hr -h, hr <r,
(7)
where rs is the rolling sphere radius, and he and hr are the maximum height of the equipment and rod height, respectively.
1.5. Surge Protective Device on DC Side Based on IEC 60364-7-712
IEC 60364-7-712 standard [14] determines whether the DC side of a PV plant requires SPD or not. According to this standard, the critical length Lcrit is calculated as
115
L^ —
-, for rooftop PV system,
Ng 120
-, for PV power plant,
Nn
(8)
where NG is the density of lightning ground flash (flash/ km2/year) which depends on the location of the structures and power lines. Lcrit is compared with maximum route length between the connection points of PV modules of the different strings and the plant inverter L. If L < Lcrit, there is no need for installing SPDs on the DC side; otherwise, the overvoltage protection system should be equipped with SPDs on the DC side.
III. Developed PV Lightning Protection System Design Software
In the studies, the standard IEC62305-2 was thoroughly analyzed, the effect of various parameters in solar power plants was studied, and software was designed based on solar power plants' features. In addition, other standards [15, 16] were examined and compared to other sources. The major purpose of developers has been the simplicity of calculations for fast and accurate design. Sometimes, the complexity of the calculations forces the experts to overlook the design of the lightning protection, which can cause irreparable damage in the event of a lightning strike and delay the return on investment of projects that have been supported by the off-taker.
The lightning protection design for a PV system, including risk assessment, is a challenging task due to numerous variables. There are also many tables in the IEC-62305-2 for the calculation of Rxs. To address this problem, a software application is developed using C# environment. It provides a user-friendly graphical interface to simplify LPS calculations. Figure 3 shows the main page of the "Lightning Overvoltage Protection Designer for PV Plants" software. It consists of the following six sections:
1. The number of dangerous events calculations;
2. The probability of damage calculations;
3. The amount of loss calculations;
4. The risk assessment;
5. The external lightning protection system calculations; and
6. The surge protective device calculations.
Upon opening the software, the "Number of Dangerous Events" section appears. The user enters the dimensions of the structure and solar farm to be protected. In addition, if available, the dimensions of the adjacent structure are specified. Finally, the user enters the line and environmental data. By clicking on the "calculate" button, the numbers of various dangerous events due to flashes are calculated according to IEC 62305-2. The second section is dedicated to calculating the probability of damage resulting from the lightning strike, as shown in Fig. 4. In this section, after entering the required data such as structure characteristic, line type, and whether a coordinated SPD is provided, the results are shown.
Figure 5 shows the "Amount of Loss" section of the software. In this section, the user specifies the input data such as the amount of risk and various values to calculate the consequent losses. The fourth section of the developed software is dedicated to assessing the risk of the PV plant, as shown in Figure 6. Using the data entered in the previous tabs, the total risk R is calculated. Then, based on Fig. 2, it is determined whether the PV plant requires protection or not.
As mentioned in subsection 2.3, it may be required to equip a PV power plant with the external LPS. The "External Lightning Protection System" section of the software calculates the number and coverage area of ATS
rods based on the rolling sphere method. In this section, the user enters the dimension of plant and protection overlap percentage. Figure 7 shows the fifth section of the developed software. Finally, the sixth section is dedicated to determining whether SPD is required on the DC side or not, as shown in Fig. 8. In this section, the density of lightning ground flash is transferred from the first tab or the user enters it; also, the installation type and L are entered. By clicking on the "calculate" button, the critical length is calculated and the answer is shown according to Subsection 2.5.
IV. Performance Evaluation This section is dedicated to investigating the performance of the developed software in both 1 MW power plant systems. The main data of 1 MW PV power plant project implemented in the north-west of Iran are presented as follows:
• Length = 200 m, Width = 100 m, Height = 3 m;
• Adjacent structure power data information: Length = 5 m, Width = 5 m, H = 5 m;
• Adjacent structure telecom data information: Length = 4 m, Width = 5 m, H = 5 m;
• Thunderstorm Days (TD) = 10;
• Complete length of power line = 1000 m;
• Complete length of data line = 900 m;
Other input information is shown in Fig. 8, 9, 10, and 11
Figure 10 indicates the risk parameters with little consideration at first.
• According to the input information in the previous menus, the results can be viewed. Figure 12 shows the Risk Assessment menu with the selection of solar farm option first and then calculation. As it turned out, the risk of R4 was identified with red color, which is not acceptable. For this reason, according to Fig. 13, we have used class 2 LPS and SPD. After the new calculation, the results have been shown in green color (Fig. 14), which indicates that the solar farm is protected with this design. In the same way, one can see the effect of different parameters using the software and do the best design.
When selecting lightning protection measures, one must examine whether the risk R determined for the relevant types of loss exceeds a tolerable value (RT). According to the IEC 62305-2, the acceptable values are programmed in the software and compared to the desired values.
According to the simulation results (Fig. 12), 0.0095479321 is obtained for the first time, which indicates that this solar farm is not protected. The designer may need to reconsider the calculations to check various parameters to find the appropriate protection according to Fig. 13 and 14, which may take a lot of time but this software has increased the accuracy and speed of calculations and reached the desired result of 0.00021506.
V Overview of the methods
The developed software is programmed in the C# language. In order to develop such software, at first comprehensive studies must be done to prepare computational and optimization algorithms. After the algorithms are developed, according to the Visual Studio product, we can design the software and reach the desired results by using C# codes. As mentioned in the paper, there are applications in this field that do not have the features of the designed software.
About 4000 lines of code were written for the development of this software in 9 months. Figures 15 and 16 show a designed software window with some codes.
VI. Conclusion
This paper was motivated by the complicated procedure of risk assessment and lightning protection of PV plants for engineers. The developed software provides risk assessment for PV plants to determine the necessity of the LPS. The number of ATS rods and the necessity to install SPD on the DC side are also determined. By adopting various combinations of inputs, the users can evaluate various LPS designs. The developed software can be used as a helpful tool to increase the LPS design understanding. In addition, compared to previous research, this study presents software designed based on a comprehensive standard and considers three different categories of solar farms, off-grid systems and on-grid rooftop systems. In addition, compared to other software designed, this software determines the number of air terminals and provides risk calculations for SPD, especially for solar power plants. By using this software, simplifying calculations and designing protection against lightning, the power plant will be safe in the event of a lightning accident. If the owner sells the electricity to the network and off-taker, the return period of its investment will be reduced.
This software can be used in countries with many lightning strikes such as East Asian countries and some European countries.
Declarations
Ethical Approval and Consent to participate
I morally accept the rules of the journal and Ethical conditions.
Consent for Publication
I express my consent to the publication of the full paper by the journal and state that I will not submit this paper to any other journal.
Availability of Supporting Data
Paper information is available and can be provided if needed.
Competing Interests
I have done this project as free research and this problem existed in the past. The only solution for fast computing has been provided. The owner and developer of this software is Mohammad Parhamfar. Thus, there are no Competing interests.
Funding
There was no special funding for this project. I have requested that the cost of publishing the paper be waived due to the Iran conditions.
Authors' Contributions
Mohammad Parhamfar has proposed the idea and developed the software using C# language. The paper has been written by him.
Acknowledgements
I appreciate Mr. Ezatolah Partovi Shal, Dr. Mohsen Niasati and Mohammad Reza Farahani for sincere cooperation.
References
[1] A. Khoshnami and I. Sadeghkhani, "Sample entropy-based fault detection for photovoltaic arrays," IEt Renewable Power Generation, vol. 12, no. 16, pp. 1966-1976, 2018. DOI: 10.1049/iet-rpg.2018.5220.
[2] International Energy Agency (IEA), "Renewables 2020 - solar PV," Available at: https://www.iea.org/ reports/renewables-2020/solar-pv.
[3] S. Ittarat, S. Hiranvarodom, B. Plangklang, "A computer program for evaluating the risk of lightning impact and for designing the installation of lightning rod protection for photovoltaic system," Energy Procedia, vol. 34, pp. 318-325, 2013. DOI: 10.1016/j. egypro.2013.06.760.
[4] M. M. Mounir, A. E. Mahmoud, "Development of lightning risk assessment software in accordance with IEC 62305-2," in 2013 International Conference on Computing, Electrical and Electronic Engineering (ICCEEE), Khartoum, Sudan, Aug 26-28, 2013, pp. 178-182. DOI: 10.1109/ICCEEE.2013.6633928.
[5] C. H. Liu, Y. B. Muna, Y. T. Chen, C. C. Kuo, H. Y. Chang, "Risk analysis of lightning and surge protection devices for power energy structures," Energies, vol. 11(8), pp. 1999-2014, 2018. DOI: 10.3390/EN11081999.
[6] I. Hetita, A. S. Zalhaf, D.-E. A. Mansour, Y. Han, P. Yang, C. Wang. "Modeling and protection of photovoltaic systems during lightning strikes: A review," Renewable Energy, vol. 184, pp. 134-148, 2022. DOI: 10.1016/j.renene.2021.11.083.
[7] S. Ittarat, S. Hiranvarodom, B. Plangklang, "A computer program for evaluating the risk of lightning impact and for designing the installation of lightning rod protection for photovoltaic system," Energy Procedia, vol. 34, pp. 318-325, 2013. DOI: 10.1016/j. egypro.2013.06.760.
[8] Technical application papers no. 10 photovoltaic plants, ABB, Tech. Rep., 2010.
[9] Lightning protection guide, DEHN + SO" HNE, Tech. Rep., 2014.
[10] IEC 62305-2: Protection against lightning - Part 2: Risk management, 2nd ed., 2010.
[11] E. Pons, R. Tommasini, "Lightning protection of PV
systems," in 2013 4th International Youth Conference on Energy (IYCE), Siofok, Hungary, Jun 6-8, 2013, pp. 1-5. DOI: 10.1109/IYCE.2013.6604209.
[12] P. Velmurugan, K. Dhayalasundaram, K. Ilangovan, "Application of IEC 62305 to a large power and desalination plant-lightning protection system," in 1st International Conference on Electrical Energy Systems, Chennai, India, 2011, pp. 308-313. DOI: 10.1109/ICEES.2011.5725348.
[13] P. H. Tan and C. K. Gan, "Methods of lightning protection for the PV power plant," in IEEE Student Conference on Research and Development, Putrajaya, Malaysia, 2013, pp. 221-226. DOI: 10.1109/ SCORED.2013.7002575.
[14] IEC 60364-7-712: Low voltage electrical installations - Part 7-712: Requirements for special installations or locations - Solar photovoltaic (PV) power supply systems, 2nd ed., 2017.
[15] UNE 21186:2011-12-21 Protection against lighting: Surge arresters using early streamer emission air terminals.
[16] NFC 17-102 "Protection against lightning early streamer emission lightning protection systems."
M. Parhamfar received his B.Sc. degree in Electrical Engineering and M.Sc. degree in Renewable Energy from the Islamic Azad University, Najaf Abad, Isfahan, Iran, in 2007 and 2019, respectively. He also held a DBA certificate in 2021. He is currently working as a freelance consultant in the power and energy field. His research interests are renewable energy, solar power plants, software development, artificial intelligence, lightning protection, and earthing.
