Direct Lightning Protection Research Articles

Study of Temperature Rise Characteristics and Voltammetry Characteristics of ZnO Varistor under 10/350μs Pulse Current

To study the effect of 10/350μs pulse current on the electrical performance of ZnO varistor, a high-current impulse experimental study was conducted in this paper. Firstly, the varistor was subjected to different amplitude impulse discharge experiments, and the temperature change of the varistor after the impulse was recorded. Then, the temperature of the varistor at the moment of 1 second after the pulse impulse was suffered by the Asymptotic function, and the Levenberg-Marquardt optimization algorithm was calculated to compare the temperature rise of the varistor under different current amplitudes. Finally, the upward shift of voltammetry characteristics in the high-current region after the impulse was explained according to the double Schottky barrier model and the linear chain aging theory. The results show that the higher the pulse current amplitude is, the higher the temperature rise of the varistor is at the 1s moment. The highest voltammetry characteristic upshift is caused by the 6.4kA pulse current. The temperature rise and the voltammetry characteristic drift in the high-current region are positively correlated. The results of the study can provide a reference for manufacturers to produce ZnO varistors for direct lightning protection of buildings.

The test method of the thunder and lightning direct effect protection equipment

In order to avoid the harm caused by the direct effect of lightning, modern new ships are equipped with lightning direct effect protection devices. However, due to the harsh environment such as high temperature, high humidity and high salt, it is easy to change its performance indicators and affect the lightning protection effect. Taking the direct lightning protection device with gaps installed at the rear end of the ship antenna as an example, through the study of its working principle and main technical indicators, the items that need to be tested regularly are determined, and the corresponding test methods are formulated. Through a large number of experiments and test data verification, the conclusion that the method can effectively reflect the main technical indicators of lightning protection facilities and then effectively evaluate the protection effect of lightning protection facilities is drawn. The research results of this paper are of great significance to regularly test the lightning direct effect protection equipment, accurately grasp the changes of its technical performance indicators, and ensure the protection effect of lightning direct effect.

Validation of the Lightning Fractal Model Based on the Attachment Probability Experiments Using Rod-Rod Air Gaps

Direct lightning poses a serious threat to the safety of power systems. In recent years, the lightning fractal model, which can reflect the fractal characteristics and randomness of lightning leaders, has been gradually applied to direct lightning protection for substations, transmission lines, etc. However, since few studies have linked simulations with experiments, the reliability of the lightning fractal model in terms of attachment probability prediction lacks experimental verification. In this paper, a series of attachment tests are carried out under a rod-rod gap. The equivalence between simulation tests and natural lightning is discussed, and the influencing factors of the attachment results are investigated. The attachment probability is simulated and compared to the test value under each test configuration. The test results show that the fractal dimension of discharge channel is consistent with the observation results of natural lightning. Under different configurations, the test value of attachment probability basically conforms to the simulation value. In general, the dispersion of the test results is slightly greater than the simulation results, but the average probability differences are all within 10%. The test results strongly indicate that the lightning fractal model is of good reliability in the prediction of strike probability.

Lightning electromagnetic transient characteristics of the space launch site

The direct lightning protection system of the space launch site can achieve effective protection against direct lightning. However, the lightning electromagnetic pulse cannot be ignored while the rocket waiting on the platform. The three-dimensional lightning transient electromagnetic model is established by method of moments, when the launch site is struck by direct lightning. In order to quantitatively evaluate lightning environment of the launch site, electromagnetic fields of launch area are calculated in this paper with a size of 40×40 m2 on the ground and at 40 m above ground. When the lightning current is 200 kA in the case of severe lightning, the simulation results of basic parameters show that magnetic field on the ground is much larger than 40 m above ground, and the maximum and minimum values of magnetic field on the ground are respectively 608 A/m (7.6Gs) and 95 A/m (1.2Gs). The electric field at 40 m above ground is much larger than the ground, and the maximum and minimum values of electric field at 40 m above ground are respectively 111 kV/m and 26 kV/m. Under six different factors, the three factors of number of shielded wires, distance between lightning towers and lightning current wave-front parameters have obvious effects on the electromagnetic field in the launch area. The highest and lowest reduction rates of electromagnetic fields are about 88% and 33% respectively. However, other factors reduce electromagnetic fields by no more than 13%. The critical magnetic field for permanent damage of electronic equipment is 2.4Gs, which is between the minimum and maximum magnetic fields of the launch area. It is recommended that electronic equipment is placed in area with smaller magnetic field, which is close to the center of the launch area. This paper provides a reference for the lightning protection indicators and suggestions for the space launch site.

Enhancing the lightning performance of overhead transmission lines with optimal EGLA and downstream shield wire placement in mountainous areas: a complete study

Service unavailability of transmission lines, particularly in mountain areas due to the direct and indirect lightning strikes, is considered as a challenging issue within electric companies. Therefore, the efforts to mitigate the power outages caused by this phenomenon have been introduced. In this study, an attempt has been made to study the different types of externally gapped line arresters (EGLAs) considering the Pinceti model and discharge voltage curve. Based on the best selected EGLA, the installation effect of EGLA on the possibility of instance back-flashover in different phases of the transmission line is investigated in the presence of downstream shield wire. For assessment, a double-circuit 400 kV transmission line in a mountainous area is modelled in EMTP-RV software. Then, an extensive analysis is carried out to verify the effectiveness of this method. The obtained results show the acceptable transmission line direct lightning protection can be achieved by four EGLAs in upper and middle phases with downstream shield wire. Although employing the downstream shield wires in the transmission line imposes more costs, but by using them, the scale and capability of EGLAs can be reduced.

Analysis about Influence on Surrounding Lightning Environment of Communication Base Station Based on One Lightning Disaster

With the lightning position data in recent years of Jiangsu, satellite and live data on 3rd,July,2012, the reasons for the damage to office room equipment beside a communication base station in Wujin District, Changzhou were analyzed, and reasonable suggestions were given. Based on the lightning accident, this paper analyzed the reasons of lightning strike to buildings near communication base station from weather, lightning strike probability, the validity of lightning protection device and potential. It is mainly because of lightning electromagnetic pulse. Base station can protect the buildings inside the protective area from direct strike, but which increased the possibility of damage to equipment from lightning impulse, at the same time, direct lightning strike probability in the scattered strike zone may increase. Therefore communication base station should be sufficiently far away from the building, when it cant meet a safe distance, not only the direct lightning protection measures should be taken to protect the station and buildings, but also protection measures against lightning electromagnetic pulse for equipment in buildings around are needed.

Analysis and experimental investigation of direct lightning protection for floating roof oil tanks

To improve the lightning protection of large floating roof oil tanks, the process of floating roof tanks stroked by lightning is analyzed, and relevant tests have been developed according to standards. Test results indicate that the major role of conductive film is to release lightning current rapidly, but the presence of conductive films has counter-effects. As long as conductive film is present, it will generate electric sparks when the floating roof tanks stroked by lightning. This paper proposes to eliminate the conductive film on the second seal floating roof top edge and instead use a scalable grounding device (SGD) as the lightning protection measure. An empirical formula has been used to calculate the transient voltage drop when the 100,000m3 tank is stroked by lightning. The results show that the floating tank is safe when there are 20 SGDs uniformly connecting the floating roof and tank wall.