Electrical grounding and earthing systems

ELECTRICAL GROUNDING AND
EARTHING SYSTEMS

Presented By:
T.Sidharth Sankar Achary
Regd No-1021106019
7th sem.
Electrical Engg.

CONTENTS
 INTRODUCTION.
 DIFFERENCE BETWEEN GROUND AND NEUTRAL.
 TYPES OF EARTHING SYSTEMS.
 TYPES OF GROUNDING.
 USES.
 CONCEPT OF VIRTUAL GROUND.
 MULTIPOINT GROUND.
 CONCLUSION.
 REFERENCES.

INTRODUCTION
 In electricity supply systems, an earthing system defines the
electrical potential of the conductors relative to that of the
Earth's conductive surface.
 The choice of earthing system has implications for the safety and
electromagnetic compatibility of the power supply.
 A protective earth (PE) connection ensures that all exposed
conductive surfaces are at the same electrical potential as the
surface of the Earth, to avoid the risk of electrical shock if a
person touches a device in which an insulation fault has
occurred. It also ensures that in the case of an insulation fault, a
high fault current flows, which will trigger an over current
protection device (fuse, MCB) that disconnects the power
supply.
 A functional earth connection serves a purpose other than
providing protection against electrical shock.

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

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

 In a polyphase or three-wire AC system, the neutral conductor is
intended to have similar voltages to each of the other circuit
conductors, and similar phase spacing. By this definition, a
circuit must have at least three wires for one to serve as a neutral.
 In the electrical trade, the conductor of a 2-wire circuit that is
connected to the supply neutral point and earth ground is also
referred to as the "neutral". This is formally described in the US
and Canadian electrical codes as the "identified" circuit
conductor.

TYPES OF EARTHING SYSTEMS
 International standard IEC 60364 distinguishes three families of
earthing arrangements, using the two-letter codes TN, TT, and
IT.
 The first letter indicates the connection between earth and the
power-supply equipment (generator or transformer):
T : direct connection of a point with earth (French: terre);
I : no point is connected with earth (isolation), except perhaps
via a high impedance.
The second letter indicates the connection between earth and the
electrical device being supplied:
T : direct connection with earth, independent of any other earth
connection in the supply system;
N : connection to earth via the supply network.

TYPES OF GROUNDING
 In radio frequency communications
 In AC power wiring installations
 Circuit ground versus earth.
 In lightning protection

In radio frequency communications
 An electrical connection to earth for as a reference potential for
radio frequency antenna signals.
 High frequency signals can flow to earth through capacitance,
capacitance to ground is an important factor in effectiveness of
signal grounds.
 An ideal signal ground maintains zero voltage regardless of how
much electrical current flows into ground or out of ground.
 The resistance at the signal frequency of the electrode-to-earth
connection determines its quality, and that quality is improved by
increasing the surface area of the electrode in contact with the
earth, increasing the depth to which it is driven, using several
connected ground rods, increasing the moisture of the soil,
improving the conductive mineral content of the soil, and
increasing the land area covered by the ground system.

In AC power wiring installations
 In a mains (AC power) wiring installation, the ground is a wire
with an electrical connection to earth, that provides an alternative
path to the ground for heavy currents that might otherwise flow
through a victim of electric shock.
 These may be located locally, be far away in the suppliers
network or in many cases both.
 This grounding wire is usually but not always connected to the
neutral wire at some point.
 The ground wire is also usually bonded to pipe work to keep it
at the same potential as the electrical ground during a fault.
 Water supply pipes often used to be used as ground electrodes
but this was banned in some countries when plastic pipe such as
PVC became popular.
 This type of ground applies to radio antennas and to lightning
protection systems.

Circuit ground versus earth
 In an electrical circuit operating at signal voltages (usually less
than 50 V or so), a common return path that is the zero voltage
reference level for the equipment or system.
 Voltage is a differential quantity, which appears between two
points having some electrical potentials. In order to deal only
with a voltage (an electrical potential) of a single point, the
second point has to be connected to a reference point (ground)
having usually zero voltage.
 This signal ground may or may not actually be connected to a
power ground.
 A system where the system ground is not actually connected to
earth is often referred to as a floating ground.

In lightning protection
 A ground conductor on a lightning protection system is used to
dissipate the strike into the earth.

USES
 A power ground serves to provide a return path for fault
currents and therefore allow the fuse or breaker to disconnect
the circuit.
 Filters also connect to the power ground, but this is mainly to
stop the power ground carrying noise into the systems which the
filters protect, rather than as a direct use of the power ground.
 In Single Wire Earth Return (SWER) electrical distribution
systems, costs are saved by using just a single high voltage
conductor for the power grid. This system is mostly used in
rural areas where large earth currents will not otherwise cause
hazards.

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

VIRTUAL GROUND CONCEPT
 If two opposite power sources are connected each other by a
conductive medium so that their opposite output quantities are
superposed (summed), zero or reference level result referred to
as virtual ground appears somewhere along the medium.
 In this "conflict" point, the efforts of the "fighting" sources are
"neutralized". The process is associated with continuous energy
wasting from both the sources as a result of a continuous energy
flow through the medium.
 Shortly, virtual ground phenomenon is summing of opposite
equal quantities associated with continuous energy wasting;
virtual ground represents the result of summing two opposite
equal quantities.

MULTI POINT GROUND
 A Multipoint Ground is an alternate type of electrical installation
that attempts to solve the Ground Loop and Mains hum
problem by creating many alternate paths for electrical energy to
find its way back to ground.
 The distinguishing characteristic of a multipoint ground is the
use of many interconnected grounding conductors into a loose
grid configuration.
 There will be many paths between any two points in a
multipoint grounding system, rather than the single path found
in a star topology ground.

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

Electrical grounding and earthing systems

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