Lightning Protection and Earthing Systems

The earth is used as an equipotential surface because it requires a very large charge to raise its potential everywhere, which allows fault currents to return to the source locally without affecting the whole system.

The two components are electrode resistance and electrode to earth resistance.

Soil resistivity affects electrode to earth resistance in that higher resistivity values lead to increased resistance, making it more difficult for the current to spread into the earth.

<p>The formula is $R = \frac{\rho}{2\pi L} \ln\left(\frac{8L}{D} - 1\right)$ where $L$ is the length, $D$ is the diameter, and $\rho$ is the soil resistivity.</p> Signup and view all the answers

<p>Electrodes must be made from metallic materials to ensure that the electrode resistance is kept very low, ideally less than 1 Ohm.</p> Signup and view all the answers

<p>If the length of the electrode is increased, the electrode to earth resistance decreases.</p> Signup and view all the answers

<p>No, two parallel electrodes do not necessarily reduce the electrode to earth resistance to half.</p> Signup and view all the answers

<p>Keeping the total earth resistance below 1 Ohm is significant because it ensures that the earthing system can effectively dissipate fault currents without raising the potential dangerously.</p> Signup and view all the answers

<p>LPL aims to define a set of lightning current parameters that establish protection measures reducing damage and consequential loss from lightning strikes.</p> Signup and view all the answers

<p>LPL I has a maximum of 200 kA, LPL II has 150 kA, while LPL III and IV both have 100 kA.</p> Signup and view all the answers

<p>The minimum current values in LPL help to derive the rolling sphere radius for each protection level.</p> Signup and view all the answers

<p>LPZ are designated areas within a structure that have specific electromagnetic characteristics for protecting equipment against lightning electromagnetic impulses (LEMP).</p> Signup and view all the answers

<p>LPZ 0A is associated with a risk of direct lightning stroke.</p> Signup and view all the answers

<p>The minimum current for LPL II is 5 kA and for LPL IV is 16 kA.</p> Signup and view all the answers

<p>It is impractical to prevent lightning current penetration due to cost-effectiveness and technical limitations.</p> Signup and view all the answers

<p>The IEC 62305 standard provides guidelines for lightning protection systems, including the establishment of LPL and LPZ.</p> Signup and view all the answers

<p>Surges are sudden increases in electrical voltage or current, often caused by lightning or switching operations. They are significant in S&amp;T installations as they can lead to equipment damage and operational failures.</p> Signup and view all the answers

<p>Lightning Protection Zones are designated areas that define the level of protection against lightning strikes. They help in determining the required measures to safeguard structures and equipment within those zones.</p> Signup and view all the answers

<p>Earthing is essential in electrical systems as it ensures safety by providing a path for fault currents to flow into the ground. It helps prevent electric shocks and protects equipment from surges.</p> Signup and view all the answers

<p>IEC 62305 standard provides guidelines for lightning protection systems and risk management to protect structures from lightning strikes. It outlines the principles for designing and implementing effective surge protection systems.</p> Signup and view all the answers

<p>Methods to reduce earth resistance include using multiple grounding electrodes, improving soil conductivity by adding conductive materials, and ensuring proper moisture content in the soil.</p> Signup and view all the answers

<p>Measuring earth resistance is crucial for verifying the effectiveness of an earthing system. It ensures that the resistance is within acceptable limits to provide adequate protection against electrical faults.</p> Signup and view all the answers

<p>Essential components include earth electrodes, conductors, bonding connections, and earth pits. Each part plays a pivotal role in ensuring effective electrical grounding.</p> Signup and view all the answers

<p>Surge protection devices function by diverting excess voltage away from sensitive equipment during a surge event, preventing damage. They act as a protective barrier, absorbing and redirecting surge energy.</p> Signup and view all the answers

<p>The typical acceptable earth resistance value for signal and telecom installations is usually less than 1 ohm. This ensures effective grounding performance.</p> Signup and view all the answers

<p>Soil resistivity refers to the ability of soil to conduct electricity, which affects the performance of earthing systems. Lower resistivity values indicate better conductivity and more effective earthing.</p> Signup and view all the answers

<p>The purpose of equipotential bonding is to interconnect all metallic installations so that they are at the same voltage potential, reducing the risk of sparking or flashover during lightning events.</p> Signup and view all the answers

<p>Equipotential bonding can be achieved through natural bonding, specific bonding conductors sized per BS EN/IEC 62305-3, or using surge protective devices (SPDs).</p> Signup and view all the answers

<p>SPDs play a role in equipotential bonding by providing a connection to the bonding bar when direct bonding conductors are unsuitable, thereby protecting the system from surges.</p> Signup and view all the answers

<p>It is important for the bonding bar to be close to the main distribution board to minimize the length of the conductors connected, which reduces potential resistance and improves safety.</p> Signup and view all the answers

<p>If metallic parts are at different voltage potentials during a lightning strike, it can result in dangerous sparking or flashover, posing a fire hazard or electrical shock risk.</p> Signup and view all the answers

<p>BS EN/IEC 62305-3 provides guidance on the sizing of bonding conductors and requirements for equipotential bonding in protection against lightning.</p> Signup and view all the answers

<p>Multiple bonding bars may be necessary in larger structures to ensure all parts are interconnected and maintain equal potential throughout the entire system.</p> Signup and view all the answers

<p>Modern electronic systems increase society's reliance on electrical safety measures by necessitating continuous and efficient operation, making effective equipotential bonding essential.</p> Signup and view all the answers

<p>2.5 mm2</p> Signup and view all the answers

<p>Fall of Potential method</p> Signup and view all the answers

<p>C1 is the current reference electrode and C2 is the secondary current reference electrode.</p> Signup and view all the answers

<p>Earth tester</p> Signup and view all the answers

<p>Because it has minimal impact compared to soil and electrode resistance.</p> Signup and view all the answers

<p>Fall of potential method and Dead earth method</p> Signup and view all the answers

<p>62 feet</p> Signup and view all the answers

<p>Spikes or rods and connecting wires</p> Signup and view all the answers

<p>Stray currents can produce serious errors in the measured value of earth resistance.</p> Signup and view all the answers

<p>By adjusting the speed of the generator handle, the wandering of the instrument pointer caused by stray currents can be minimized.</p> Signup and view all the answers

<p>The double wound transformer isolates the source of current from the supply during testing.</p> Signup and view all the answers

<p>Auxiliary electrodes should consist of 12.5mm diameter mild steel rods driven up to 1m into the ground.</p> Signup and view all the answers

<p>It is time-consuming and labor-intensive due to the need for disconnection of individual ground electrodes.</p> Signup and view all the answers

<p>The Clamp-on method does not require disconnection of the earth conductor and uses induced voltage to measure resistance.</p> Signup and view all the answers

<p>To prevent measurement errors caused by interference from nearby electrodes and resistance areas.</p> Signup and view all the answers

<p>It is placed midway between the test electrode and the auxiliary current electrode to facilitate accurate measurements.</p> Signup and view all the answers

<p>The ionization of air molecules by high-speed electrons from the step leader creates the conducting path for lightning.</p> Signup and view all the answers

<p>The step leader is not very bright, while the returning stroke, or streamer, is much brighter.</p> Signup and view all the answers

<p>The buildup of negative electrical charges within the clouds initiates the formation of the stepped leader.</p> Signup and view all the answers

<p>Electric field intensification causes positive charges on the ground to gather, facilitating the discharge process.</p> Signup and view all the answers

<p>Lightning causes heating of air up to 30,000 K, creates pressure shock waves, and a current flow of 10 kA to 200 kA.</p> Signup and view all the answers

<p>A conducting path forms, completing the circuit necessary for the lightning discharge.</p> Signup and view all the answers

<p>The returning stroke creates the intense light, heat, and sound associated with lightning.</p> Signup and view all the answers

<p>Lightning within clouds is typically not directed, whereas cloud-to-ground lightning involves a discharge that can cause significant damage.</p> Signup and view all the answers

<p>LEMP stands for Lightning Electromagnetic Impulse, which is significant because it addresses the electromagnetic effects of lightning that can damage contemporary electronic systems.</p> Signup and view all the answers

<p>Transient overvoltages occur when current is interrupted, releasing energy stored in the magnetic field, with higher currents and longer conductor lengths contributing to their magnitude.</p> Signup and view all the answers

<p>The shift involves moving from advisory annexes in earlier standards to mandatory protections against specific surge types, emphasizing proactive measures rather than reactive repairs.</p> Signup and view all the answers

<p>Inadequate LEMP protection can lead to significant damage to electronic systems, including complete failure, fire hazards, and potential safety risks to users.</p> Signup and view all the answers

<p>Inductive loads like motors and transformers store energy in magnetic fields, and when the current is interrupted, they release this energy as transient overvoltages.</p> Signup and view all the answers

<p>The reduction in size of modern electronics makes them more susceptible to LEMP damage due to the smaller tolerances and less energy required to damage their circuits.</p> Signup and view all the answers

<p>Recognizing that LEMP damage can occur from multiple strike points emphasizes the need for comprehensive protection strategies across all connected services and structures.</p> Signup and view all the answers

<p>The IEC 62305 standard facilitates better risk management by providing structured guidelines to assess and mitigate risks associated with surge and lightning impacts on electronic systems.</p> Signup and view all the answers

<p>An equipotential bonding system and surge arresters.</p> Signup and view all the answers

<p>Earthing is performed to provide a safe path for fault currents and to stabilize voltage levels in electrical systems.</p> Signup and view all the answers

<p>LPZ 0A is subjected to direct strikes with full lightning current, while LPZ 1 experiences no direct strikes but may encounter damped magnetic fields.</p> Signup and view all the answers

<p>The resistivity of dry soil is $1000 ext{ Ohm.Meter}$.</p> Signup and view all the answers

<p>Surge arresters filter and clamp transients at the power entry point to protect equipment.</p> Signup and view all the answers

<p>Without equipotential bonding, there may be dangerous voltage potentials between metallic parts during faults.</p> Signup and view all the answers

<p>Moist soil has a resistivity of $100 ext{ Ohm.Meter}$, which is higher than wet soil's resistivity of $10 ext{ Ohm.Meter}$.</p> Signup and view all the answers

<p>It provides guidelines for the design and implementation of lightning protection systems to safeguard structures.</p> Signup and view all the answers

<p>A person touching them could receive a lethal shock, posing significant safety risks.</p> Signup and view all the answers

<p>SPDs provide a practical means of protecting equipment against transient overvoltages, ensuring continuous operation during lightning events.</p> Signup and view all the answers

<p>Earthing helps eliminate or limit voltages and currents due to electromagnetic interference (EMI) and radio frequency interference (RFI).</p> Signup and view all the answers

<p>Both are interconnected; neglecting surge protection could compromise the effectiveness of structural lightning protection.</p> Signup and view all the answers

<p>At least 20 kg of bentonite clay is recommended.</p> Signup and view all the answers

<p>Earthing provides a pathway for heavy fault currents, ensuring effective and quick operation of protective devices.</p> Signup and view all the answers

<p>Equipotential bonding of external earth electrodes and provision of an equipotential busbar inside the equipment room.</p> Signup and view all the answers

<p>Enhanced SPDs allow for uninterrupted operation of critical systems by managing lightning-induced surges efficiently.</p> Signup and view all the answers

<p>A comprehensive and complex risk assessment.</p> Signup and view all the answers

<p>Inadequate earthing can lead to lethal shocks to personnel and damage to critical communication systems.</p> Signup and view all the answers

<p>The series consists of four parts, which collectively provide a holistic approach to lightning protection.</p> Signup and view all the answers

<p>It sets guidelines that integrate lightning protection with surge protective measures for comprehensive safety.</p> Signup and view all the answers

<p>It classifies sources and types of damage from lightning and defines relationships between damage and loss.</p> Signup and view all the answers

<p>Protection against transient overvoltages or electrical surges.</p> Signup and view all the answers

<p>It includes factors related to structural integrity and potential life hazards.</p> Signup and view all the answers

<p>It defines the relationship between lightning current parameters and the resulting potential damages.</p> Signup and view all the answers

<p>500mm below ground level.</p> Signup and view all the answers

<p>Auxiliary electrodes help determine the potential difference needed to calculate the resistance of the test electrode.</p> Signup and view all the answers

<p>The readings of the voltmeter (V) in volts and the ammeter (I) in amperes.</p> Signup and view all the answers

<p>A high voltmeter resistance ensures accurate potential measurements without affecting the current flow.</p> Signup and view all the answers

<p>It is expressed as $R = \frac{V}{I}$, where R is resistance, V is voltage, and I is current.</p> Signup and view all the answers