TC 5 Earthing and Surge Protection Devices

Devices designed to protect electrical installations from surges, typically from lightning.

A system to ground electrical equipment, preventing dangerous voltage differences.

International standard for lightning protection, providing guidelines for surge protection.

The opposition to the flow of current to the earth.

Areas within a system that are prone to lightning strikes, requiring different protection levels.

A sudden increase in voltage or current, often caused by lightning.

The part of the earthing system that connects to the ground.

How much a soil resists the flow of electrical current.

A closed-loop earthing system using multiple earthing points.

A set of rules and guidelines from an organization, likely IEC (International Electrotechnical Commission), for creating systems that withstand and protect against lightning impacts.

Using bentonite clay to fill earth pits for improved electrical resistivity in earthing systems.

A system where external and internal earth electrodes are connected in a ring for equipotential bonding, ensuring uniform potential.

Connecting different earth electrodes to achieve a common ground potential, minimizing voltage differences.

International standard for lightning protection, focusing on comprehensive risk assessment for protecting structures and connected systems.

A crucial step in lightning protection, considering the structure, connected services, and potential damages to make informed protection decisions.

Four parts of the lightning protection standard: general principles, risk management, physical damage, and electrical systems.

Details about the characteristics of lightning currents which are important for designing effective lightning protection.

Essential component of electrical installations that provides a low-resistance path for fault currents to flow to earth, effectively minimizing risks.

Four levels of lightning protection, increasing in required protection as the likely lightning current increases.

Categories of Lightning Protection Systems (LPS) directly linked to the LPLs in BS EN/IEC 62305-1

System designed to protect buildings from lightning strikes on the outside of the structure

Type of external LPS used when combustible materials or explosion risks are present.

Type of external LPS used for structures without combustible materials or explosion risk.

The part of the external LPS designed to intercept, capture, and channel lightning.

Individual parts that together make up a lightning protection system like air termination, down conductors and earth termination.

Process that evaluates the likelihood of a lightning strike on a structure to determine the suitable LPS class.

A lightning protection system method using meshes of specified sizes, typically used on surfaces that require protection.

IEC 62305 defines mesh sizes (5x5m, 10x10m, 15x15m, 20x20m) related to four LPS classes, for optimized protection.

Air termination conductors are placed at roof edges, overhangs, and ridges with a pitch over 1 in 10 for maximized protection.

Important for flat roofs, these conductors should be placed near the roof's edge for effective lightning protection in modern research.

Vertical air rods (finials) or strike plates are roof-mounted components connected to beneath-roof conductors aiding lightning dissipation.

Air rods/strike plates should be spaced within a 10m/5m radius respectively to ensure complete protection coverage.

Debate around unconventional air termination systems validity has not resulted in their recognition under current standard BS EN/IEC 62305.

The rolling sphere method for calculating protection is limited to a height of the rolling sphere's radius to the appropriate reference plane.

The actual physical size of an air termination system (like an air rod) determines the protection zone, not claimed enhancements.

Contains the core principles of air termination protection in the body, rather than an annex.

BS 6651 and BS EN/IEC 62305-3 provide guidelines for minimum metal thickness on metallic roofs to prevent puncture.

Convey lightning current from air termination system to earth termination system, following the most direct practical route.

Categories of Lightning Protection Systems, directly related to protection levels.

Thickness for metal sheets in air termination systems; considers prevention of puncture, hot spots, and ignition issues.

Height of the air rod in an air termination system, determining the zone of protection. Only real dimensions are valid.

No other lightning protection standard exists alongside BS EN/IEC 62305.

Method for creating an earth pit using an augured/dug hole, earth electrode, enhancement material, and backfill.

Earthing method using multiple pits interconnected to reduce soil resistance, especially in high resistance areas.

3 meters to 6 meters, ensuring an effective low resistance earthing system, preventing high impedance paths.

Material added to the earth pit to lower soil resistance, improving the earthing's effectiveness.

Method to join copper strips or tapes to earth electrodes for a robust, low resistance connection.

Providing a low-resistance connection from the pit to equipotential bonding bus.

Measure of soil's opposition to current flow when used as a part of the earthing.

Method for improving low resistance earthing using a network of interconnected earth pits, useful for areas of high soil resistivity.

Surges cause significant financial losses from equipment damage and service disruptions.

Heat storms create rising warm air and descending cold air, producing cloud cells in tropical thunderstorms.

Frontal storms feature frontal waves pushing warm air upward, creating numerous cloud cells in temperate thunderstorms.

Thunderclouds accumulate positive charges at higher altitudes and negative charges nearer the ground.

The negative cloud charge causes induced positive charges to gather on ground objects beneath the cloud.

Surges are among the leading causes of significant financial loss in damaged Electrical Installations.

Warm air is forced upward by frontal systems resulting in the development of multiple cloud cells.

Rising warm air and descending cold air create the conditions for various interconnected cloud cells in thunderstorms.

Areas around a structure that are vulnerable to lightning strikes, requiring different levels of protection.

BS EN/IEC 62305 classifies lightning damage based on the location of the strike (structure, near structure, service, near service).

Lightning strikes can cause injury, physical damage to equipment or the building, and damage to internal systems.

Damage from lightning can lead to loss of life, service disruptions, cultural damage, and financial losses.

Enclosing a structure within a conductive shield, with proper bonding of connected services, to maximize protection against lightning.

Standard containing guidelines and principles for creating protective lightning protection schemes which assess dangers and details adequate protective features.

Direct lightning strike to the structure, potentially causing injury or physical damage via various mechanisms.

Lightning strikes on services connected to the structure, such as cables.

Connecting metallic parts to a common ground potential, preventing voltage differences during lightning strikes, minimizing sparking risk.

Conductive materials used to connect different metallic parts to create equipotential bonding, following standards like BS EN/IEC 62305-3.

A central point for connecting various metallic installations (e.g., gas, water, power) to ensure a common ground during lightning.

A device used in equipotential bonding to protect electrical systems from surges by diverting excess current to ground.

The flow of electricity during a lightning strike, which can cause damage if not properly diverted to the earth.

Any metal component within an electrical system, such as pipes, conduits, or equipment enclosures.

The space between different metallic components to avoid electrical discharge.

An international standard for lightning protection. It provides guidelines on equipotential bonding for electrical installations, helping to protect them from damage from lightning.

Measure of soil's opposition to current flow, crucial for earthing systems.

Earthing electrode with flat surface, resistance depends on length and depth of laying.

Earthing electrode with thin, elongated shape; good for layered soil

Electrode shape affects how current flows in the soil, influencing resistance to ground.

The opposition to current flow from the electrode to the earth; depends on soil type and electrode geometry.

Sites with high moisture content, not ideal for good earthing if soil is dry, sand or gravel.

Choosing earthing locations that aren't naturally well-drained, crucial for effective earthing.

The design of the electrode significantly influences its resistance to ground; elongated shapes have lower resistance.

The opposition to current flow to the earth.

A soil's resistance to the flow of electrical current.

Earth resistance decreases first quickly, then slowly with longer electrodes.

Changes in conductor size and depth have a small impact on earth resistance.

Connecting multiple strips in parallel reduces resistance.

Material selection for electrodes must consider resistance to corrosion in the specific soil.

Copper, tinned or not, is a good choice for earth electrodes (low corrosion).

Resistance (R) is calculated using the formula given where ρ, l, w, and t are input parameters.

The rate at which current flows per unit area at the surface of an earth electrode.

The highest safe current density at an electrode surface to prevent failure due to excessive heat. For long-duration loading: 40A/m2.

Transient high current flow for a short time (e.g., during a fault).

Inversely proportional to the square of the current density during short-time overload.

i = 7.57 x 10^3 / √(ρt), where i is current density, ρ is soil resistivity, and t is duration.

A measure of how easily electrical current flows through the soil.

Sustained current flow, like during normal system operation.

A type of earth electrode with a flat surface.

Surges cause significant financial losses due to equipment damage and service interruptions.

Devices that safeguard electrical systems from surges, often caused by lightning.

Heat storms, characterized by rising warm air and descending cold air, create cloud cells in tropical thunderstorms.

A low-resistance pathway for fault currents to safely ground electrical equipment.

International standard for lightning protection, a crucial guideline for surge protection.

Frontal storms feature frontal waves pushing warm air upward, creating numerous cloud cells in temperate thunderstorms.

Opposition to current flow to the earth, crucial for earthing system effectiveness.

Thunderclouds accumulate positive charges at higher altitudes and negative charges near the ground.

The negative cloud charge induces positive charges to gather on ground objects directly below the cloud.

Areas with varying risk of lightning strikes, needing different levels of protection.

A sudden increase in voltage or current, often from lightning.

A sudden increase in voltage or current, often caused by lightning.

Surges account for 27.4% of total loss (damage costs) in electrical installations.

The part of an earthing system that directly connects to the earth.

Soil's resistance to current flow, critically influencing earthing system design.

Negligence accounts for 36.1% of total damage while surges cause 27.4% in electrical installations.

A closed loop earthing system using multiple connections to ground. It creates a uniform potential for protection.

A set of rules and guidelines for creating lightning protection systems and ensuring safety.

Four predefined levels of lightning protection, each with specific maximum and minimum lightning current parameters.

Maximum current and minimum current during a lightning strike. Used in designing lightning protection systems.

Zones categorized based on lightning strike risk, used to tailor protection measures for equipment within the zones.

International Standard for lightning protection, outlining guidelines to minimize lightning strike damage.

Highest permitted lightning current value for a specific protection level.

Lowest permitted lightning current value for a specific protection level.

External zone, highest strike risk; requires highest protection systems

External zone, probability of partial lightning; relatively high protection needed.

The opposition to current flow to the earth, measured using a hand-driven generator and a moving-coil ohm meter to eliminate stray currents.

Unwanted currents flowing in the soil that can affect earth resistance measurements.

Additional electrodes used with test electrodes for earth resistance measurements, typically 12.5mm mild steel rods driven 1 meter into the ground.

A non-invasive method of measuring earth resistance where no probes are used, a voltage is induced, and current flow is measured.

A reliable and accurate earth testing method that's time-consuming and can be labor intensive.

Test electrodes and current electrodes must be positioned independently from each other's resistance area, with auxiliary electrodes placed at specified distances.

Auxiliary current electrode should be placed at least 30 meters away from the test electrode in order to prevent the current flowing to the test electrode.

The source of the testing current must be completely isolated from the supply using a double-wound transformer to prevent influence from other sources of current.

The terminal used to connect protective and functional earthing conductors to the grounding system.

The voltage change in one electrode caused by a 1-ampere current change in another, measured in ohms.

The potential difference per unit length in the direction of maximum change.

A conductor used to protect against electric shock, connecting exposed, extraneous, main earthing, and earthed source parts.

The area of the ground around an earth electrode where a significant voltage gradient exists.

The potential difference between two points on the ground separated by one meter, in the direction of maximum potential gradient.

The potential difference between a grounded structure and a point on the ground separated by a typical reach of about one meter.

The resistance of a 1-meter cube of soil, measured between opposite faces; expressed in ohm-meters.

A conductive material that improves earthing effectiveness, especially in areas of poor conductivity.

The material's ability to easily conduct electricity.

A measure of how much the material resists current flow (less than 0.2 ohm-meters).

Main components of the earth enhancement material.

The material won't deteriorate over time, maintaining its conductivity.

Measuring resistance in a 20cm cube of the material to assure conductivity.

The material used to fill the area around the electrode after excavation.

Materials like sand, salt, coke breeze, cinders, and ash should not be used due to their corrosive nature.