TC 5 Earthing and Surge Protection Devices
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Questions and Answers

What is the minimum recommended amount of bentonite clay to be used in an earth pit?

  • 30 kg
  • 10 kg
  • 20 kg (correct)
  • 40 kg

    • Which of the following is NOT a part of the BS EN/IEC 62305 series?

  • Lightning detection (correct)
  • Physical damage to structures and life hazard
  • Risk management
  • General principles

    • What is the primary purpose of the BS EN/IEC 62305 standard?

  • To enhance structural stability
  • To detail fire safety protocols
  • To ensure lightning protection (correct)
  • To provide guidelines for aesthetic building design

    • How does using less than the recommended amount of bentonite clay initially affect resistivity?

    <p>It may lower resistivity initially</p> Signup and view all the answers

    Which part of the BS EN/IEC 62305 deals with risks and potential losses due to lightning?

    <p>Part 2</p> Signup and view all the answers

    What is included in the ring earth system for equipment safety?

    <p>Joining of external and internal earth rings</p> Signup and view all the answers

    Which of the following risks is addressed in Part 3 of BS EN/IEC 62305?

    <p>Physical damage to structures and life hazard</p> Signup and view all the answers

    What is the relationship defined in Part 1 of BS EN/IEC 62305?

    <p>Between damage and loss for risk assessment</p> Signup and view all the answers

    What is the minimum depth that the earth electrode should be placed during installation?

    <p>2.8 meters</p> Signup and view all the answers

    Which material is used to fill the dug hole for the earth electrode?

    <p>Earth enhancement material</p> Signup and view all the answers

    What is the minimum diameter of the composite structure formed by the earth electrode and earth enhancement material?

    <p>100mm</p> Signup and view all the answers

    What is the maximum distance between two successive earth electrodes in a loop earth system?

    <p>6 meters</p> Signup and view all the answers

    What size should the copper strip be that is welded to the main earth electrode?

    <p>150mmX25mmX6mm</p> Signup and view all the answers

    What technique is used to interlink the earth pits in a loop earth system?

    <p>Exothermic welding</p> Signup and view all the answers

    How far should the main earth pit be located from the main equipotential earth busbar?

    <p>As near as possible</p> Signup and view all the answers

    What is the purpose of the earth enhancement material in the earth pit?

    <p>To improve conductivity</p> Signup and view all the answers

    What is the maximum mesh size for Class II LPS according to the standard?

    <p>10 X 10 m</p> Signup and view all the answers

    Which of the following conditions must be met for the mesh method to be suitable?

    <p>No metal installation can protrude above the air termination system.</p> Signup and view all the answers

    What is the purpose of installing perimeter conductors on flat roofs?

    <p>To prevent lightning damage.</p> Signup and view all the answers

    What is the recommended maximum spacing for vertical air rods according to the current standard?

    <p>10 m apart</p> Signup and view all the answers

    What does Class IV LPS define as the maximum mesh size?

    <p>20 X 20 m</p> Signup and view all the answers

    Why was there debate over non-conventional air termination systems in the standards?

    <p>Their efficacy was questioned.</p> Signup and view all the answers

    Where should air termination conductors be positioned?

    <p>At roof edges and ridges with a pitch above 5.7º.</p> Signup and view all the answers

    Which of the following statements reflects the modern understanding of lightning protection?

    <p>Lightning can damage flat roofs more than sloped roofs.</p> Signup and view all the answers

    What determines the zone of protection provided by an air termination system according to BS EN/IEC 62305?

    <p>The real physical dimension of the air termination system</p> Signup and view all the answers

    According to BS EN/IEC 62305, which material requires a minimum thickness of 5 mm in air termination systems to prevent puncture?

    <p>Copper</p> Signup and view all the answers

    In the context of down conductors, what is the recommended routing strategy as per BS EN/IEC 62305?

    <p>To take a direct route towards the earth termination system</p> Signup and view all the answers

    Which standard provides guidance on the minimum thickness of metal components for air termination arrangements before BS EN/IEC 62305?

    <p>BS 6651</p> Signup and view all the answers

    Which class of lightning protection system (LPS) corresponds to a minimum thickness requirement of 0.5 mm for stainless steel?

    <p>Class IV</p> Signup and view all the answers

    What is the significance of the thickness defined as 't' in relation to metal sheets in air termination systems as indicated in BS EN/IEC 62305?

    <p>To prevent puncture, hot spot, or ignition</p> Signup and view all the answers

    What enhancement feature is NOT considered acceptable according to BS EN/IEC 62305 for determining the zone of protection of an air rod?

    <p>Non-conventional designs</p> Signup and view all the answers

    Which guideline is provided regarding metallic roofs in air termination systems as per BS EN/IEC 62305?

    <p>Their thickness and type of material are critical</p> Signup and view all the answers

    What is the relationship between Lightning Protection Levels (LPLs) and classes of Lightning Protection Systems (LPS)?

    <p>The greater the LPL, the higher class of LPS is required.</p> Signup and view all the answers

    When would an Isolated Lightning Protection System (LPS) be chosen?

    <p>When the structure is made of combustible materials or may explode.</p> Signup and view all the answers

    Which of the following elements is NOT part of an external Lightning Protection System?

    <p>Surge protection device</p> Signup and view all the answers

    What is a crucial function of the air termination system in an LPS?

    <p>To capture lightning discharge current and direct it to earth.</p> Signup and view all the answers

    What determines the class of LPS that must be installed in a structure?

    <p>The result of the risk assessment calculation.</p> Signup and view all the answers

    Which statement regarding non-isolated LPS is true?

    <p>It can be used where no explosive risk is present.</p> Signup and view all the answers

    What chapter discusses the physical effects of lightning?

    <p>Surges and their effects on S&amp;T Installations</p> Signup and view all the answers

    Which method is NOT listed for reducing earth resistance?

    <p>Thermal modification</p> Signup and view all the answers

    Which standard outlines the foundation of a Lightning Protection System's design?

    <p>BS EN/IEC 62305-1</p> Signup and view all the answers

    What does IEC stand for in relation to surge protection standards?

    <p>International Electrotechnical Commission</p> Signup and view all the answers

    What aspect must a lightning protection designer consider for the external LPS?

    <p>The thermal and explosive effects of a lightning strike.</p> Signup and view all the answers

    Which component is part of a good earthing system?

    <p>Multiple Earth Pits</p> Signup and view all the answers

    Which section provides guidelines for surge protection devices for telecom equipment?

    <p>Surge Protection Devices for Telecom Equipments</p> Signup and view all the answers

    What is a Lightning Protection Level (LPL)?

    <p>A categorization of protective measures against lightning</p> Signup and view all the answers

    Which is NOT a characteristic of a good earthing system?

    <p>Insufficient inspection protocols</p> Signup and view all the answers

    Which chapter focuses on risk management related to lightning protection?

    <p>Surge Protection Standard IEC 62305</p> Signup and view all the answers

    What is the objective of the earthing system?

    <p>To facilitate safe discharge of electrical faults</p> Signup and view all the answers

    Which of the following is part of the surge protection measures?

    <p>Coordinated surge protection devices</p> Signup and view all the answers

    What percentage of total loss due to damages is attributed to surges?

    <p>27.4%</p> Signup and view all the answers

    In tropical regions, what is the estimated altitude of the positive charge center in the atmosphere during heat storms?

    <p>10000 m</p> Signup and view all the answers

    What type of storm is identified as causing thunderstorms in temperate regions?

    <p>Frontal storms</p> Signup and view all the answers

    Which of the following statements correctly describes the charge distribution in thunderstorms?

    <p>The upper part of the atmosphere carries a positive charge.</p> Signup and view all the answers

    What is the most common cause of loss due to damages in S&T installations according to the statistics provided?

    <p>Negligence</p> Signup and view all the answers

    How does the accumulation of electric charges in cloud masses lead to lightning?

    <p>By causing a discharge between the ground and the cloud.</p> Signup and view all the answers

    What is the maximum height of the negative charge center in the atmosphere during frontal storms in temperate regions?

    <p>2500 m</p> Signup and view all the answers

    What effect does the lower negatively charged part of a cloud have on the ground below it?

    <p>It induces positive charge on the ground.</p> Signup and view all the answers

    What is the effect of increasing the length of an electrode on earth resistance?

    <p>Earth resistance decreases sharply and then slowly.</p> Signup and view all the answers

    Which material is most resistant to corrosion for earth-electrodes based on the findings?

    <p>Copper</p> Signup and view all the answers

    What is the maximum resistance factor when two strip electrodes are positioned 2.4m apart?

    <p>Less than 65 percent of the individual resistance.</p> Signup and view all the answers

    How does the size and depth of a conductor affect earth resistance under normal usage conditions?

    <p>It has little to no effect on resistance.</p> Signup and view all the answers

    What average loss in weight was observed for unprotected ferrous specimens after 12 years in soil?

    <p>2.2 percent per year.</p> Signup and view all the answers

    What minimum average loss in weight indicates satisfactory performance for galvanized mild steel used as earth-electrodes?

    <p>0.5 percent per year.</p> Signup and view all the answers

    What factor primarily affects the choice of electrode material in relation to earth resistance?

    <p>Corrosion resistance in soil type.</p> Signup and view all the answers

    Which types of ground conditions should be avoided when selecting a site for earthing systems?

    <p>Ground that is naturally well-drained</p> Signup and view all the answers

    Which statement best describes the performance of tinned copper electrodes over time?

    <p>They show minimal loss in weight similar to bare copper.</p> Signup and view all the answers

    Which type of damage is NOT caused by flashes to a service according to BS EN/IEC 62305?

    <p>Chemical release due to floodwater</p> Signup and view all the answers

    In the resistance formula for plate electrodes, which variable has the major influence on electrode to earth resistance?

    <p>Length of electrode (L)</p> Signup and view all the answers

    What is the primary reason for using strip or conductor electrodes in earthing systems?

    <p>To manage high resistivity soil beneath low resistivity layers</p> Signup and view all the answers

    What is a main source of loss caused by lightning, as identified in BS EN/IEC 62305?

    <p>Loss of economic value</p> Signup and view all the answers

    Which statement correctly reflects an ideal lightning protection measure for a structure according to the standards?

    <p>Enclosing the structure within an earthed metallic shield</p> Signup and view all the answers

    What happens to current density in the soil near electrified surfaces as the distance from the electrode increases?

    <p>Current density decreases with distance</p> Signup and view all the answers

    What is the primary factor that affects the overall resistance of an earth electrode system?

    <p>Shape and design of the electrode</p> Signup and view all the answers

    What is the primary focus of the damage sources S3 and S4 in the lightning protection framework?

    <p>Flashes affecting services and their proximity to the structure</p> Signup and view all the answers

    Which type of damage is associated with the direct impact of lightning to a structure?

    <p>Physical damage resulting from fire or explosion</p> Signup and view all the answers

    Which condition does NOT contribute positively to the effectiveness of earthing electrode systems?

    <p>High moisture content in sandy soils</p> Signup and view all the answers

    What does the acronym LPZ stand for in the context of lightning protection?

    <p>Lightning Protection Zone</p> Signup and view all the answers

    According to the content, what design feature is essential to achieve low overall resistance in earth electrodes?

    <p>Creating large length-to-thickness ratios</p> Signup and view all the answers

    In BS EN/IEC 62305, which specific type of loss is linked to the casualty of living beings due to lightning strikes?

    <p>Loss of human life</p> Signup and view all the answers

    Which common misconception about electrode surface area is addressed in the text?

    <p>Resistance is not inversely proportional to surface area</p> Signup and view all the answers

    What is the maximum allowable current density at the surface of an earth electrode during long-duration loading?

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

    Which of the following is NOT a consideration in determining the lightning protection scheme based on BS EN/IEC 62305?

    <p>The color of the structure's exterior</p> Signup and view all the answers

    How does soil moisture affect the resistance of the earth electrode over time?

    <p>Initially decreases then increases</p> Signup and view all the answers

    What is the formula used to determine the maximum permissible current density at an electrode surface?

    <p>i = 7.57 x 103 / √(ρt)</p> Signup and view all the answers

    What indicates a failure of an earth electrode primarily attributed to?

    <p>Excessive temperature rise</p> Signup and view all the answers

    In scenarios of short-time overload, how does the time to failure relate to current density?

    <p>Inversely proportional to specific loading</p> Signup and view all the answers

    Which soil characteristic is generally expected to have a negative temperature coefficient of resistance?

    <p>Clay soils</p> Signup and view all the answers

    What type of loading conditions necessitate specific design considerations for earth electrodes?

    <p>Long-duration and short-time overload conditions</p> Signup and view all the answers

    Which of the following best describes the relationship between temperature rise and soil moisture at an earth electrode?

    <p>Moisture depletion results from high temperature rise</p> Signup and view all the answers

    What is the primary purpose of equipotential bonding in lightning protection systems?

    <p>To ensure that all metallic parts have the same electrical potential</p> Signup and view all the answers

    When is it appropriate to use surge protective devices (SPDs) in equipotential bonding?

    <p>When direct connections via bonding conductors are unsuitable</p> Signup and view all the answers

    Which factor is NOT considered when sizing bonding conductors according to BS EN/IEC 62305-3?

    <p>The expected lightning strike frequency in the area</p> Signup and view all the answers

    What is the preferred location for an equipotential bonding bar in relation to the main distribution board?

    <p>Close to the main distribution board for effective bonding</p> Signup and view all the answers

    Which of the following is true regarding the interconnection of multiple bonding bars in large structures?

    <p>They must be interconnected to maintain equal voltage potential</p> Signup and view all the answers

    In the context of lightning equipotential bonding, what role do surge protective devices (SPDs) serve?

    <p>They protect sensitive equipment from voltage surges</p> Signup and view all the answers

    Which of the following describes the effect of equipotential bonding on the risk of sparking?

    <p>It eliminates the voltage potential difference, reducing the risk</p> Signup and view all the answers

    What is an essential design consideration when choosing bonding conductors for lightning protection?

    <p>The sizing according to specific standards and anticipated currents</p> Signup and view all the answers

    What percentage of total loss due to various reasons is attributed to surges?

    <p>27.4%</p> Signup and view all the answers

    In tropical regions, what are thunderstorms more commonly referred to as?

    <p>Heat storms</p> Signup and view all the answers

    What is the primary cause of the positive charge center in tropical thunderstorms?

    <p>Rising warm air</p> Signup and view all the answers

    Which factors contribute to the accumulation of electric charges in the cloud mass during thunderstorms?

    <p>Violent up-draughts of air</p> Signup and view all the answers

    Where does the negative charge center reside in the case of heat storms in tropical regions?

    <p>About 5000 m above ground</p> Signup and view all the answers

    What is the consequence of lightning on equipment in S&T installations?

    <p>Interruption of service</p> Signup and view all the answers

    What is the effect of thunderstorms on the formation of cloud cells in temperate regions?

    <p>They facilitate the formation of fewer but larger cloud cells</p> Signup and view all the answers

    Which atmospheric condition primarily leads to the formation of ice crystals with a positive charge during a storm?

    <p>Warm air rising rapidly</p> Signup and view all the answers

    What is the maximum current parameter for Lightning Protection Level I (LPL I)?

    <p>200 kA</p> Signup and view all the answers

    Which Lightning Protection Level has the highest minimum current value?

    <p>IV</p> Signup and view all the answers

    How many Lightning Protection Levels (LPL) are established according to the standard?

    <p>4</p> Signup and view all the answers

    Which Lightning Protection Zone (LPZ) corresponds to the risk of a direct lightning stroke?

    <p>LPZ 0A</p> Signup and view all the answers

    What purpose do Lightning Protection Zones (LPZ) serve?

    <p>To determine required protective measures against LEMP</p> Signup and view all the answers

    What parameter is considered to derive the rolling sphere radius for each Lightning Protection Level?

    <p>Minimum lightning current</p> Signup and view all the answers

    Which Lightning Protection Level has the lowest maximum current value?

    <p>I</p> Signup and view all the answers

    What is the main reason for implementing protection measures according to the Lightning Protection Levels?

    <p>To reduce damage and consequential loss from lightning</p> Signup and view all the answers

    What does the term 'Mutual Resistance of Grounding Electrodes' refer to?

    <p>The voltage change in one electrode due to a current in another</p> Signup and view all the answers

    Which factors influence the resistivity of soil?

    <p>Moisture content and chemical composition</p> Signup and view all the answers

    What is 'Step Voltage' in relation to electrical safety?

    <p>The difference in potential between two points on the surface</p> Signup and view all the answers

    What is the significance of Resistance Area for an Earth Electrode?

    <p>It determines the area needed for effective grounding</p> Signup and view all the answers

    What does 'Touch Voltage' measure?

    <p>The potential difference between a grounded structure and the earth</p> Signup and view all the answers

    How does the geological formation affect soil resistivity?

    <p>By influencing the layering and composition of the soil</p> Signup and view all the answers

    What is meant by 'Potential Gradient' at a point?

    <p>The potential difference per unit length in a specified direction</p> Signup and view all the answers

    Which of the following describes a Protective Conductor?

    <p>A conductor used to protect against electric shock in specific parts</p> Signup and view all the answers

    What is the primary focus of Chapter 3 of the content?

    <p>Surge Protection Standard IEC 62305</p> Signup and view all the answers

    Which aspect is NOT covered under the section about earthing systems?

    <p>Measurement of Earth Voltage</p> Signup and view all the answers

    What does 'LPL' stand for in the context of surge protection?

    <p>Lightning Protection Level</p> Signup and view all the answers

    Which method is included in reducing earth resistance?

    <p>Using multiple earth pits</p> Signup and view all the answers

    Which topic is NOT part of the fundamentals covered in Chapter 2?

    <p>Enhanced Surge Protection Devices</p> Signup and view all the answers

    Which standard provides guidelines specifically related to risk management in surge protection?

    <p>BS EN/IEC 62305-2</p> Signup and view all the answers

    Which of the following is a purpose of the earth enhancement material?

    <p>To improve electrical conductivity</p> Signup and view all the answers

    What distinguishes non-conventional air termination systems?

    <p>Incorporation of advanced technology</p> Signup and view all the answers

    What is typically NOT included in surge protection measures?

    <p>Geographical Risk Assessment</p> Signup and view all the answers

    In the context of lightning protection systems, what does 'terminal' refer to?

    <p>The termination of conductors</p> Signup and view all the answers

    What is the primary material composition of earth enhancement material?

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

    What characteristic ensures that the earth enhancement material does not require periodic maintenance?

    <p>It is permanent and maintenance free.</p> Signup and view all the answers

    What is the maximum resistivity allowed for earth enhancement material?

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

    Which of the following attributes ensures that earth enhancement material is environmentally friendly?

    <p>Non-corrosive nature</p> Signup and view all the answers

    Why is high hygroscopic ability an important characteristic of earth enhancement material?

    <p>It ensures moisture retention for conductivity.</p> Signup and view all the answers

    What should not be used as backfill material around the electrode?

    <p>Coke breeze and cinders</p> Signup and view all the answers

    What ambient temperature range can earth enhancement material withstand?

    <p>-100 C to +600 C</p> Signup and view all the answers

    Which characteristic of earth enhancement material allows it to be used in various soil types?

    <p>Suitability for different resistivity soils</p> Signup and view all the answers

    What is a major drawback of the fall of potential method for earth resistance measurement?

    <p>It is time consuming and requires disconnection of ground electrodes.</p> Signup and view all the answers

    Which method directly addresses the issue of stray currents affecting measurements in earth resistance testing?

    <p>Using a hand-driven generator with alternating current</p> Signup and view all the answers

    Which statement accurately describes the placement of test electrodes during measurement?

    <p>Auxiliary current electrodes should be placed at least 30m away from the test electrode.</p> Signup and view all the answers

    What feature should an earth tester have to indicate the presence of stray currents during testing?

    <p>A hand-driven generator with a synchronous rectifier</p> Signup and view all the answers

    What is a characteristic of the Clamp-on method of measuring earth resistance?

    <p>It can be performed without the need for individual ground electrode disconnections.</p> Signup and view all the answers

    Why is it recommended to separate the test electrode from the earthing system when conducting measurements?

    <p>To eliminate the potential influence of system resistance on readings.</p> Signup and view all the answers

    Which aspect of an earth resistance measuring device contributes to the measurement of current flow?

    <p>The design of the current loop circuitry.</p> Signup and view all the answers

    What is the effect of an increase or decrease in the generator handle speed during testing?

    <p>It causes the instrument pointer to wander and indicates stray currents.</p> Signup and view all the answers

    Study Notes

    TC 5 EARTHING AND SURGE PROTECTION DEVICES

    • Material presented in this IRISET note is for guidance only, it does not overwrite Railway Board directives or manuals.
    • Earthing and surge protection devices are crucial for safety and smooth operation of signal and telecommunication systems on Indian Railways.
    • Lightning protection zones (LPZs) are concepts used in these systems to prevent damage from lightning.
    • Typical lightning strikes can cause high-magnitude transient voltages and currents, damaging system components.
    • Potential differences within circuits, high-speed electrons, and positive and negative charge centers are part of the process of a lightning strike.
    • Different types of lightning discharges exist, each associated with various possible consequences, including injuries to people and infrastructure damage due to fires.
    • Equipment failure and costly repairs are potential consequences of lightning damage.
    • IEC 62305 is a standard for lightning protection that considers risk assessment and interconnected devices.
    • Four primary risk considerations include human life, public service, cultural heritage, and economic value.
    • Lightning protection levels (LPLs) are important for designing and installing appropriate protection systems.
    • Protection zones are important to understand how to safeguard equipment from various types of lightning strikes, such as cloud-to-ground or within a cloud strike.
    • Grounding systems or earth termination systems are essential for harmless dissipation of lightning current.
    • Grounding systems should be designed in a way to lower overall resistance and protect against corrosion.

    Fundamentals of Earthing

    • Earth is not a good conductor but an equipotential surface
    • Earth resistance is a composite of electrode resistance and electrode-to-earth resistance.
    • Electrode materials (galvanized iron (GI) or copper) are selected for minimum resistance for electrical conductivity and corrosion resistance.
    • Soil resistivity, geometry, and electrode size affect electrode-to-earth resistance
    • Methods for reducing soil resistance include adding soil mixtures (e.g., bentonite clay, salt, charcoal, sand) and burying/spacing of electrodes.
    • Pipe and plate electrodes are common earthing options.
    • Formulas are available for calculating resistance of these common electrode types.

    Surge Protection Standard IEC 62305

    • International Electrotechnical Commission (IEC) developed the BS EN/IEC 62305 standard for lightning protection, which considers the entire structure and its associated services.
    • BS EN/IEC 62305 standards contain four parts, all of which are crucial and require consideration during design,
    • Structural and transient overvoltage protection are integral elements of this standard,
    • Damage and loss are identified as flashes to the structure, flashes near to the structure, flashes to a service, and flashes near to a service.
    • Classification of lightning protection zones (LPZs) is essential for effective protection.
    • Four protection levels (LPLs) are defined by maximum and minimum lightning current parameters, used in the design of surge protection devices.
    • Protection provided by earth termination systems is discussed, including types of systems such as type A, and type B; and foundation electrodes.

    RDSO Specification for Earthing System for Signal and Telecom Installations

    • RDSO specifications for signalling and telecommunication (S&T) earthing systems follow Indian Standard Code of practice, IS 3043-1987.
    • Earthing is used to maintain zero potential for non-current carrying parts of a system.
    • Earthing systems are critical for personnel safety and system reliability regarding equipment operation, signals, and telecommunication.
    • Earth resistance testing has multiple methods, including fall of potential and clamp-on.
    • Earthing electrodes and the soil must be considered when deciding whether a system has sufficient earthing to distribute current safely.
    • Guidance is available regarding earth electrodes and the sphere of influence of a given earth electrode.
    • Systems like ring earth systems and multiple pit constructions require careful consideration to avoid excessive current flows that might damage equipment.
    • Appropriate bonding to ensure continuity of the grounding systems or equipotential bonding is critical.

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    TC 5 Earthing and Surge Protection Devices PDF

    Description

    This quiz focuses on the importance of earthing and surge protection devices in ensuring safety within the signal and telecommunication systems of Indian Railways. It discusses lightning protection zones and the effects of lightning strikes, as well as standards like IEC 62305. Test your knowledge on how these devices function to prevent damage and maintain operational integrity.

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