# Impacts of Lightning-Induced Overvoltage on a Hybrid Solar PV-Battery Energy Storage System
## 3 Overview of Lightning Phenomenon  
Lightning is well-known as a catastrophic phenomenon that occurs during thunderstorms and produces electric discharge in the form of a spark or flash that originates in a charge cloud [22]. Lightning discharges can be divided into two main categories, i.e., ground flashes and cloud flashes. Ground flashes are lightning discharges that strike the ground and can be classified into four types based on the charge polarity from the cloud to the ground, i.e., upward positive, upward negative, downward positive, and downward negative. Meanwhile, cloud flashes can be categorized into three main types, i.e., intracloud, air, and intercloud discharges [23]. Thus, lightning has always been one of the major threats to such systems, which can cause overvoltage due to direct lightning strikes and indirect lightning strikes. In this study, indirect lightning strikes are the prime interest, since they can cause significant problems to power systems, even though they have less impact than direct lightning strikes. Indirect lightning strikes usually strike the ground surface or a nearby object, while the lightning-induced overvoltage occurs due to electromagnetic coupling between the system and the lightning strike channel [24]. The lightning-induced overvoltage also can be evaluated by using simulation based on the following practice [22; 25]. 1. The lightning return stroke current model should be used to calculate the electromagnetic field generated by the lightning return stroke current, as discussed in Section 4.2;
2. Then, the lightning-induced overvoltage should be obtained by modeling the coupling model, as described in Section 4.3. The Risk of Lightning-Induced Overvoltage in Hybrid Solar PV-Battery Energy Storage Systems and the Previous ResearchAt present, solar PV energy is recognized as a competitive and mature renewable energy (RE) technology due to its huge benefits nationwide. Although solar PV energy only provides 2.6% of the global power output, it had greater capacity than any other technology in 2019 [26; 27; 28; 29], which proves that solar PV energy still has great potential in generating electricity, as shown in Figure 3. In order to sustain solar PV growth and to cater to energy demands, grid-connected hybrid solar PV-battery energy storage has become a very attractive option [26; 30; 31]. The function of battery energy storage is to store and deliver energy, which may assist national electricity suppliers in ensuring the consistency of electricity supply to the grid. Figure 4 presents battery energy storage markets in European countries; Germany is the leading country, with 66% of the total in battery energy storage  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of BESS** & \multicolumn{2}{c}{**Description**} & \multicolumn{2}{c}{**Advantages**} & \multicolumn{2}{c}{**Disadvantages**} \\ \hline Primary BES &  
markets in 2019, however the growth of battery energy storage slowed down in 2020 due to COVID-19 pandemic [32]. Despite the massive installation growth of solar PV and battery energy storage in all countries, there is one natural phenomenon that cannot be avoided, which is lightning. Since such systems are usually located in outdoor areas, the possibility of lightning striking such systems is very high, especially when such systems are located in areas with a high likelihood of lightning, such as Malaysia. This paper focuses on indirect lightning strikes, whereby the lightning does not directly strike the electrical equipment, however lightning-induced overvoltage can be generated and can travel over any equipment from the strike point. Essentially, indirect lightning strikes can cause many power outages, which directly reduce the system's efficiency, and to some extent might cause equipment to malfunction [11, 22, 33, 34, 35, 36, 37, 38]. Figure 5 presents the statistical data for the destruction of solar PV systems in Germany. About 31.2% of the damages were due to lightning strikes.