Lightning Protection Systems and Earthing Quizzes

It consists of horizontal or vertical earth electrodes connected to each down conductor fixed on the outside of the structure.

Type B arrangement features a fully connected ring earth electrode around the structure's periphery, in contact with soil for at least 80% of its length.

Foundation earth electrodes, installed in the concrete foundation, augment the Type B arrangement and may use steel reinforcing foundation mesh.

<p>A separation distance minimizes the risk of partial lightning current entering the structure through conductive parts.</p> Signup and view all the answers

<p>It recommends a single integrated earth termination system combining lightning protection, power, and telecommunication systems.</p> Signup and view all the answers

<p>The primary role is to prevent dangerous sparking within the structure due to lightning discharge currents.</p> Signup and view all the answers

<p>It can bridge the gap, introducing partial lightning current into the structure and causing potential hazards.</p> Signup and view all the answers

<p>Type B uses a ring electrode around the structure, while Type A connects individual electrodes to each down conductor.</p> Signup and view all the answers

<p>To maintain a zero potential or zero voltage of all non-current carrying parts to prevent lethal shocks.</p> Signup and view all the answers

<p>It acknowledges the need for integrating structural lightning protection with transient overvoltage and surge protection for equipment.</p> Signup and view all the answers

<p>SPDs provide a practical cost-effective means of protecting systems during lightning electromagnetic pulse (LEMP) activity.</p> Signup and view all the answers

<ol> <li>To afford safety to personnel against shock. 2. To protect equipment against high voltages.</li> </ol> Signup and view all the answers

<p>If electrified, a person touching those parts could receive a lethal shock.</p> Signup and view all the answers

<p>To ensure the safe and reliable operation of equipment.</p> Signup and view all the answers

<p>By earthing protective devices like surge arrestors and lightning dischargers.</p> Signup and view all the answers

<p>It provides a path for heavy fault currents to ensure effective and quick operations.</p> Signup and view all the answers

<p>The hemisphere of radius L represents the exclusive soil portion required for each electrode, influencing the calculation of electrode to earth resistance.</p> Signup and view all the answers

<p>The electrode to earth resistance can be halved if the electrodes are separated by a distance of 2L.</p> Signup and view all the answers

<p>The length L has a major influence, while thickness T has a minor influence on the electrode to earth resistance.</p> Signup and view all the answers

<p>Engineers began using electrode-grids for substations to effectively reduce high 'electrode to earth' resistance.</p> Signup and view all the answers

<p>Graphite and Portland cement.</p> Signup and view all the answers

<p>Adding salt, charcoal, and sand mixture, and burying the ground electrode as deep as possible are two methods to reduce earth resistance.</p> Signup and view all the answers

<p>The resistivity of surface soil, loam, etc. ranges from 1 to 50 Ohm-m.</p> Signup and view all the answers

<p>Less than 0.2 ohm-meters.</p> Signup and view all the answers

<p>A maintenance-free earth system is recommended to simplify tracking and treatment across a large number of systems.</p> Signup and view all the answers

<p>To maintain its conductivity and to avoid polluting the soil or local water table.</p> Signup and view all the answers

<p>The resistivity of clay soil ranges from 2 to 100 Ohm-m.</p> Signup and view all the answers

<p>It shall not depend on the continuous presence of water.</p> Signup and view all the answers

<p>It must be thermally stable between -100 C to +600 C.</p> Signup and view all the answers

<p>It requires no periodic charging treatment nor replacement and maintenance.</p> Signup and view all the answers

<p>It should be sieved to remove any large stones and well compacted.</p> Signup and view all the answers

<p>Sand, salt, and cinders.</p> Signup and view all the answers

<p>Below 20 percent moisture, soil resistivity increases very abruptly with a decrease in moisture content.</p> Signup and view all the answers

<p>Normal moisture content ranges from 10 percent in dry seasons to 35 percent in wet seasons, averaging about 16 to 18 percent.</p> Signup and view all the answers

<p>In cold climates, earth electrodes should be installed at least 2 meters below the frost line.</p> Signup and view all the answers

<p>The temperature coefficient of resistivity is negligible above freezing, having minimal impact on resistivity changes.</p> Signup and view all the answers

<p>Below 0°C, water in the soil begins to freeze, causing a tremendous increase in soil resistivity.</p> Signup and view all the answers

<p>Preferred soil types include wet marshy ground, clay loam, damp sand, and peat in that order of preference.</p> Signup and view all the answers

<p>A difference of a few percent moisture below 20 percent can cause a marked increase in soil resistivity.</p> Signup and view all the answers

<p>At 20°C, the resistivity changes by about 9 percent per degree Celsius.</p> Signup and view all the answers

<p>Dry sand, gravel, chalk, limestone, granite, very stony ground, and areas with virgin rock close to the surface should be avoided.</p> Signup and view all the answers

<p>Because above 15 to 20 percent moisture content, additional moisture does not significantly improve the earthing effectiveness.</p> Signup and view all the answers

<p>The resistance is lower for shapes like pipes, rods, or strips compared to plates due to the current density decreasing rapidly with distance from the electrode.</p> Signup and view all the answers

<p>The formula is $R = \frac{\rho}{2\pi L} \left[\ln(8L/T) + \ln(L/h) - 2 + (2h/L) - (h/L)^{2}\right]$.</p> Signup and view all the answers

<p>The length (L) has a major influence on reducing the electrode to earth resistance.</p> Signup and view all the answers

<p>The thickness (T) of the electrode has a minor influence compared to the length.</p> Signup and view all the answers

<p>They are beneficial where high resistivity soil lies beneath shallow layers of low resistivity.</p> Signup and view all the answers

<p>They realized that large area plates did not effectively solve the problem of high 'electrode to earth' resistance.</p> Signup and view all the answers

<p>5X5 meters.</p> Signup and view all the answers

<p>Air termination conductors must be at roof edges and no metal installations can protrude above the system.</p> Signup and view all the answers

<p>Not more than 10 meters apart.</p> Signup and view all the answers

<p>Not more than 5 meters apart.</p> Signup and view all the answers

<p>They are most susceptible to strikes, necessitating additional protection measures.</p> Signup and view all the answers

<p>They can be utilized as part of the air termination system.</p> Signup and view all the answers

<p>Non-conventional air termination systems.</p> Signup and view all the answers

<p>It requires conductors to be positioned along the roof edges and ridges for optimal protection.</p> Signup and view all the answers

<p>Lightning can cause physical damage, electrical surges, and malfunctions in S&amp;T installations.</p> Signup and view all the answers

<p>LPZs are designated areas that define the levels of lightning protection and the corresponding risks within those areas.</p> Signup and view all the answers

<p>The IEC 62305 standard provides comprehensive guidelines for lightning protection systems and risk management.</p> Signup and view all the answers

<p>A good earthing system should have low resistance, effective current dissipation, and proper grounding techniques.</p> Signup and view all the answers

<p>The earth termination system safely conducts lightning currents into the ground, minimizing damage to structures.</p> Signup and view all the answers

<p>Low soil resistivity allows for better current flow, which is critical for the effectiveness of earthing systems.</p> Signup and view all the answers

<p>High earth resistance can lead to inadequate dissipation of fault currents, increasing the risk of electric shock or equipment damage.</p> Signup and view all the answers

<p>Considerations include protection level, voltage ratings, and environmental conditions where the SPDs will be installed.</p> Signup and view all the answers

<p>Equivalent earth resistance measures the effectiveness of the grounding system in dissipating fault currents safely.</p> Signup and view all the answers

<p>Increased moisture content typically lowers soil resistivity; an optimal range is generally between 10-20%.</p> Signup and view all the answers

<p>The Type A arrangement connects horizontal or vertical earth electrodes directly to each down conductor, providing localized dissipation, while Type B uses a periphery ring for a broader, integrated grounding strategy.</p> Signup and view all the answers

<p>The limitation is that it reduces the overall effectiveness of the grounding system, as not being in soil contact can lead to higher resistance and less efficient current dissipation.</p> Signup and view all the answers

<p>An integrated system minimizes the risk of dangerous sparking and ensures effective protection for lightning, power, and telecommunication systems by maintaining a common grounding point.</p> Signup and view all the answers

<p>They augment the earthing capability by incorporating electrodes directly into the concrete foundation, thus ensuring stability and continuity in grounding.</p> Signup and view all the answers

<p>Measures include strategically placing lightning conductors away from structural metal parts to avoid any bridging of electrical currents during a discharge.</p> Signup and view all the answers

<p>Internal LPS design is critical for preventing dangerous sparking by mitigating the flow of lightning current through conductive internal components.</p> Signup and view all the answers

<p>The material must maintain stability and not leach, which ensures that its resistivity levels remain consistent over time without requiring regular maintenance.</p> Signup and view all the answers

<p>If the moisture content drops below 20%, soil resistivity increases, reducing the efficiency of grounding, while normal moisture levels promote adequate electrical conductivity.</p> Signup and view all the answers

<p>Soil resistivity increases very abruptly with decreases in moisture content below 20 percent.</p> Signup and view all the answers

<p>At low temperatures, particularly below 0°C, soil resistivity increases significantly due to the freezing of water in the soil.</p> Signup and view all the answers

<p>Wet marshy ground is the most preferred, followed by clay or loamy soil.</p> Signup and view all the answers

<p>This range allows for optimal conductivity, ensuring that soil resistivity remains stable enough for effective earth connections.</p> Signup and view all the answers

<p>The resistivity changes by approximately 9 percent per degree Celsius at this temperature.</p> Signup and view all the answers

<p>This prevents significant variations in resistance caused by freezing temperatures and ensures consistent grounding.</p> Signup and view all the answers

<p>There will be a substantial variation in resistance throughout different seasons, affecting grounding effectiveness.</p> Signup and view all the answers

<p>Frozen upper soil increases resistivity and effectively shortens the active length of the electrode.</p> Signup and view all the answers

<p>Increasing the distance reduces the total earth resistance due to decreased mutual influence.</p> Signup and view all the answers

<p>It must be metallic to ensure low resistance and extensive to minimize resistance impact on measurement.</p> Signup and view all the answers

<p>The sphere of influence is the volume around the earth electrode where electrical charges spread, impacting resistance measurements.</p> Signup and view all the answers

<p>Earth pits should not be placed within the sphere of influence of each other.</p> Signup and view all the answers

<p>Using non-metallic pipes would increase resistance, leading to inaccurate measurement.</p> Signup and view all the answers

<p>The separation distance should be at least twice the length of the electrode.</p> Signup and view all the answers

<p>The earth electrode must be far enough away to avoid being influenced by the water pipe's resistance.</p> Signup and view all the answers

<p>The closest shell to the electrode has the highest resistance and affects the measurements significantly.</p> Signup and view all the answers

<p>40 A/m²</p> Signup and view all the answers

<p>The maximum permissible current density is inversely proportional to the duration of the earth fault.</p> Signup and view all the answers

<p>The resistance increases, potentially becoming infinite with enough temperature rise.</p> Signup and view all the answers

<p>Time to failure is inversely proportional to the square of the current density (i²).</p> Signup and view all the answers

<p>i = 7.57 x 10³ / √(ρ t) A/m²</p> Signup and view all the answers

<p>It generally leads to an initial decrease in electrode resistance.</p> Signup and view all the answers

<p>Long-time overloading conditions are significantly affected by soil moisture.</p> Signup and view all the answers

<p>The initial decrease in electrode resistance due to soil properties.</p> Signup and view all the answers