ELECTRICAL GROUNDING ELECTRICAL GROUNDING AND EARTHING SYSTEMSAND EARTHING SYSTEMS

Presented By:Presented By:

T.Sidharth Sankar AcharyT.Sidharth Sankar Achary

Regd No-1021106019Regd No-1021106019

77thth sem. sem.

Electrical Engg.Electrical Engg.

CONTENTSCONTENTS INTRODUCTION.INTRODUCTION. DIFFERENCE BETWEEN GROUND AND DIFFERENCE BETWEEN GROUND AND

NEUTRAL.NEUTRAL. TYPES OF EARTHING SYSTEMS.TYPES OF EARTHING SYSTEMS. TYPES OF GROUNDING.TYPES OF GROUNDING. USES.USES. CONCEPT OF VIRTUAL GROUND.CONCEPT OF VIRTUAL GROUND. MULTIPOINT GROUND.MULTIPOINT GROUND. CONCLUSION.CONCLUSION. REFERENCES.REFERENCES.

INTRODUCTIONINTRODUCTION In electricity supply systems, an earthing system In electricity supply systems, an earthing system

defines the electrical potential of the conductors defines the electrical potential of the conductors relative to that of the Earth's conductive surface.relative to that of the Earth's conductive surface.

The choice of earthing system has implications for the The choice of earthing system has implications for the safety and electromagnetic compatibility of the power safety and electromagnetic compatibility of the power supply.supply.

A protective earth (PE) connection ensures that all A protective earth (PE) connection ensures that all exposed conductive surfaces are at the same electrical exposed conductive surfaces are at the same electrical potential as the surface of the Earth, to avoid the risk potential as the surface of the Earth, to avoid the risk of electrical shock if a person touches a device in which of electrical shock if a person touches a device in which an insulation fault has occurred. It also ensures that in an insulation fault has occurred. It also ensures that in the case of an insulation fault, a high fault current the case of an insulation fault, a high fault current flows, which will trigger an over current protection flows, which will trigger an over current protection device (fuse, MCB) that disconnects the power supply.device (fuse, MCB) that disconnects the power supply.

A functional earth connection serves a purpose other A functional earth connection serves a purpose other than providing protection against electrical shock.than providing protection against electrical shock.

DIFFERENCE BETWEEN DIFFERENCE BETWEEN GROUND AND NEUTRAL.GROUND AND NEUTRAL.

Ground or earth in a mains (AC power) electrical wiring system Ground or earth in a mains (AC power) electrical wiring system is a conductor that exists primarily to help protect against faults is a conductor that exists primarily to help protect against faults and which in normal operation does not carry current.and which in normal operation does not carry current.

Neutral is a circuit conductor that may carry current in normal Neutral is a circuit conductor that may carry current in normal operation, and which is usually connected to earth. In house operation, and which is usually connected to earth. In house wiring, it is the center tap connection of the secondary winding wiring, it is the center tap connection of the secondary winding of the power company's transformer.of the power company's transformer.

In a polyphase or three-wire AC system, the neutral conductor is In a polyphase or three-wire AC system, the neutral conductor is intended to have similar voltages to each of the other circuit intended to have similar voltages to each of the other circuit conductors, and similar phase spacing. By this definition, a conductors, and similar phase spacing. By this definition, a circuit must have at least three wires for one to serve as a circuit must have at least three wires for one to serve as a neutral. neutral.

In the electrical trade, the conductor of a 2-wire circuit that is In the electrical trade, the conductor of a 2-wire circuit that is connected to the supply neutral point and earth ground is also connected to the supply neutral point and earth ground is also referred to as the "neutral". This is formally described in the US referred to as the "neutral". This is formally described in the US and Canadian electrical codes as the "identified" circuit and Canadian electrical codes as the "identified" circuit conductor. conductor.

TYPES OF EARTHING TYPES OF EARTHING SYSTEMSSYSTEMS

International standard IEC 60364 distinguishes International standard IEC 60364 distinguishes three families of earthing arrangements, using the three families of earthing arrangements, using the two-letter codes TN, TT, and IT.two-letter codes TN, TT, and IT.

The first letter indicates the connection between The first letter indicates the connection between earth and the power-supply equipment (generator or earth and the power-supply equipment (generator or transformer):transformer):

T : direct connection of a point with earth (French: T : direct connection of a point with earth (French: terre); terre);

I : no point is connected with earth (isolation), I : no point is connected with earth (isolation), except perhaps via a high impedance.except perhaps via a high impedance.

The second letter indicates the connection between The second letter indicates the connection between earth and the electrical device being supplied:earth and the electrical device being supplied:

T : direct connection with earth, independent of T : direct connection with earth, independent of any other earth connection in the supply system; any other earth connection in the supply system;

N : connection to earth via the supply network. N : connection to earth via the supply network.

TN NETWORKTN NETWORK

TN-S NETWORKTN-S NETWORK

TN-C NETWORKTN-C NETWORK

TN-C-S NETWORKTN-C-S NETWORK

TT NETWORKTT NETWORK

IT NETWORKIT NETWORK

TYPES OF GROUNDINGTYPES OF GROUNDING

In radio frequency communications In radio frequency communications In AC power wiring installations In AC power wiring installations Circuit ground versus earth.Circuit ground versus earth. In lightning protection In lightning protection

In radio frequency In radio frequency communications communications

An electrical connection to earth for as a reference An electrical connection to earth for as a reference potential for radio frequency antenna signals.potential for radio frequency antenna signals.

High frequency signals can flow to earth through High frequency signals can flow to earth through capacitance, capacitance to ground is an important capacitance, capacitance to ground is an important factor in effectiveness of signal grounds.factor in effectiveness of signal grounds.

An ideal signal ground maintains zero voltage An ideal signal ground maintains zero voltage regardless of how much electrical current flows into regardless of how much electrical current flows into ground or out of ground.ground or out of ground.

The resistance at the signal frequency of the electrode-The resistance at the signal frequency of the electrode-to-earth connection determines its quality, and that to-earth connection determines its quality, and that quality is improved by increasing the surface area of quality is improved by increasing the surface area of the electrode in contact with the earth, increasing the the electrode in contact with the earth, increasing the depth to which it is driven, using several connected depth to which it is driven, using several connected ground rods, increasing the moisture of the soil, ground rods, increasing the moisture of the soil, improving the conductive mineral content of the soil, improving the conductive mineral content of the soil, and increasing the land area covered by the ground and increasing the land area covered by the ground system.system.

In AC power wiring In AC power wiring installations installations

In a mains (AC power) wiring installation, the ground is a In a mains (AC power) wiring installation, the ground is a wire with an electrical connection to earth, that provides wire with an electrical connection to earth, that provides an alternative path to the ground for heavy currents that an alternative path to the ground for heavy currents that might otherwise flow through a victim of electric shock.might otherwise flow through a victim of electric shock.

These may be located locally, be far away in the suppliers These may be located locally, be far away in the suppliers network or in many cases both. network or in many cases both.

This grounding wire is usually but not always connected This grounding wire is usually but not always connected to the neutral wire at some point.to the neutral wire at some point.

The ground wire is also usually bonded to pipe work to The ground wire is also usually bonded to pipe work to keep it at the same potential as the electrical ground keep it at the same potential as the electrical ground during a fault.during a fault.

Water supply pipes often used to be used as ground Water supply pipes often used to be used as ground electrodes but this was banned in some countries when electrodes but this was banned in some countries when plastic pipe such as PVC became popular.plastic pipe such as PVC became popular.

This type of ground applies to radio antennas and to This type of ground applies to radio antennas and to lightning protection systems.lightning protection systems.

Circuit ground versus Circuit ground versus earth earth

In an electrical circuit operating at signal voltages In an electrical circuit operating at signal voltages (usually less than 50 V or so), a common return path (usually less than 50 V or so), a common return path that is the zero voltage reference level for the that is the zero voltage reference level for the equipment or system. equipment or system.

Voltage is a differential quantity, which appears Voltage is a differential quantity, which appears between two points having some electrical potentials. between two points having some electrical potentials. In order to deal only with a voltage (an electrical In order to deal only with a voltage (an electrical potential) of a single point, the second point has to be potential) of a single point, the second point has to be connected to a reference point (ground) having usually connected to a reference point (ground) having usually zero voltage.zero voltage.

This signal ground may or may not actually be This signal ground may or may not actually be connected to a power ground.connected to a power ground.

A system where the system ground is not actually A system where the system ground is not actually connected to earth is often referred to as a floating connected to earth is often referred to as a floating ground.ground.

In lightning protection In lightning protection A ground conductor on a lightning protection A ground conductor on a lightning protection

system is used to dissipate the strike into the system is used to dissipate the strike into the earth.earth.

USESUSES A power ground serves to provide a return path for fault A power ground serves to provide a return path for fault

currents and therefore allow the fuse or breaker to currents and therefore allow the fuse or breaker to disconnect the circuit.disconnect the circuit.

Filters also connect to the power ground, but this is Filters also connect to the power ground, but this is mainly to stop the power ground carrying noise into the mainly to stop the power ground carrying noise into the systems which the filters protect, rather than as a direct systems which the filters protect, rather than as a direct use of the power ground. use of the power ground.

In Single Wire Earth Return (SWER) electrical In Single Wire Earth Return (SWER) electrical distribution systems, costs are saved by using just a distribution systems, costs are saved by using just a single high voltage conductor for the power grid. This single high voltage conductor for the power grid. This system is mostly used in rural areas where large earth system is mostly used in rural areas where large earth currents will not otherwise cause hazards.currents will not otherwise cause hazards.

Signal grounds serve as return paths for signals and Signal grounds serve as return paths for signals and power at low voltages (less than about 50 V) within power at low voltages (less than about 50 V) within equipment, and on the signal interconnections between equipment, and on the signal interconnections between equipment.equipment.

GENERAL GROUNDINGGENERAL GROUNDING

GENERATOR EARTHINGGENERATOR EARTHING

VIRTUAL GROUND VIRTUAL GROUND CONCEPTCONCEPT

If two opposite power sources are connected each If two opposite power sources are connected each other by a conductive medium so that their opposite other by a conductive medium so that their opposite output quantities are superposed (summed), zero or output quantities are superposed (summed), zero or reference level result referred to as virtual ground reference level result referred to as virtual ground appears somewhere along the medium.appears somewhere along the medium.

In this "conflict" point, the efforts of the "fighting" In this "conflict" point, the efforts of the "fighting" sources are "neutralized". The process is associated sources are "neutralized". The process is associated with continuous energy wasting from both the with continuous energy wasting from both the sources as a result of a continuous energy flow sources as a result of a continuous energy flow through the medium.through the medium.

Shortly, virtual ground phenomenon is summing of Shortly, virtual ground phenomenon is summing of opposite equal quantities associated with continuous opposite equal quantities associated with continuous energy wasting; virtual ground represents the result energy wasting; virtual ground represents the result of summing two opposite equal quantities.of summing two opposite equal quantities.

MULTI POINT GROUNDMULTI POINT GROUND A Multipoint Ground is an alternate type of A Multipoint Ground is an alternate type of

electrical installation that attempts to solve the electrical installation that attempts to solve the Ground Loop and Mains hum problem by Ground Loop and Mains hum problem by creating many alternate paths for electrical creating many alternate paths for electrical energy to find its way back to ground.energy to find its way back to ground.

The distinguishing characteristic of a multipoint The distinguishing characteristic of a multipoint ground is the use of many interconnected ground is the use of many interconnected grounding conductors into a loose grid grounding conductors into a loose grid configuration.configuration.

There will be many paths between any two There will be many paths between any two points in a multipoint grounding system, rather points in a multipoint grounding system, rather than the single path found in a star topology than the single path found in a star topology ground.ground.

CONCLUSIONCONCLUSION

Grounding and Earthing systems form the Grounding and Earthing systems form the first line of defense in every type of first line of defense in every type of electrical systems. The system may be a electrical systems. The system may be a generator/transformer/housing generator/transformer/housing installation/generating station/etc. So it is installation/generating station/etc. So it is strictly advised to know the basic concepts strictly advised to know the basic concepts of grounding as far as electrical engg. is of grounding as far as electrical engg. is concerned.concerned.

THANK YOUTHANK YOU