Abstract
This paper evaluates the effect of a lightning strike directly on the 24 kV distribution lines in Thailand, where such strikes are one of the main causes of power outages. The voltage across the insulator, and the arrester energy absorbed due to the lightning, need to be analyzed for different grounding distances of the overhead ground wire, ground resistance, lightning impact positions, and lightning current waveforms. Analysis and simulations are conducted using the Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to find the energy absorbed by the arrester and the voltages across the insulator. The results indicate that when surge arresters are not installed, the voltage across the insulator at the end of the line is approximately 1.4 times that in the middle of the line. In addition, the ground resistance and grounding distance of the overhead ground wire affect the voltage across the insulator if the overhead ground wire is struck. When surge arresters are installed, a shorter grounding distance of the overhead ground wire and a lower ground resistance are not always desirable; this is because they reduce the back-flashover rate and the voltage across the insulator if lightning strikes the overhead ground wire. However, lightning strikes to the phase conductor result in high arrester energy and the possibility that the arrester will fail. Furthermore, the tail time of the lightning waveform is a significant variable when considering the energy absorbed by the arrester, whereas the front time is important for the voltage across the insulator. In case lightning strikes directly on the connected point between the overhead lines and the underground cables, the distribution line system is protected only by the lightning arrester at the connection point. The overvoltage at the connection point is lower than the basic impulse level at 24 kV of 125 kV, but the overvoltage at the end of the cable is still more than 125 kV in case the cable is longer than 400 m. When the distribution line system is protected by the lightning arrester at both the connection point and the end of the cable, it results in overvoltage throughout the cable is lower than the critical flashover of insulation. This method is the best way to reduce the failure rate of underground cables and equipment that are connected to the distribution line system.
Highlights
Lightning is a significant cause of temporary and permanent power outages, due to the abnormal stresses it puts on the distribution lines
Lightning strikes to the phase conductor result in high arrester energy and the possibility that the arrester will fail; The tail time of the lightning waveform is a significant variable when considering the energy absorbed by the arrester, whereas the front time is important for the voltage across the insulator; In the case where lightning directly strikes the connecting point between the overhead lines and the underground cables, the distribution line system is protected only by the lightning arrester at the connection point
The results show that the system is not protected by the lightning arrester when the lightning strikes at the connection point, protected by the lightning arrester when the lightning strikes at the connection point, causing causing the excess overvoltage that occurs at the connected points A and B, the excess overvoltage that occurs at the connected points A and B, which is which is greater than 125 kV (24 kV system’s insulation durability), and causes the underground greater than 125 kV (24 kV system’s insulation durability), and causes the underground cables and cables and 24 kV equipment connected to them to be damaged
Summary
Lightning is a significant cause of temporary and permanent power outages, due to the abnormal stresses it puts on the distribution lines. In Thailand, statistics from the Metropolitan Electricity Authority (MEA) [4] report outages per year with an unknown cause that may be the result of lightning hitting the system. Lightning protection is an important consideration in the design of distribution lines. There are many techniques that are considered efficient ways of decreasing the frequency of outages, due to lightning strike; these include using overhead ground wires and surge arresters, which. Energies 2019, 12, 3193 are the most common form of lightning protection used to increase the reliability of the distribution system. Overhead ground wires are installed above the phase conductor to intercept lightning strikes and conduct the current to the ground; arresters are fixed between the phase conductor and the ground
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
