INTRODUCTION In electricity supply systems, an earthling system defines the
electrical potential of the conductors relative to that of the Earths conductive
surface 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
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 companys 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
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
 13. 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.
 14. 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.
 15. 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.
 16. In lightning protection A ground conductor on a lightning protection
system is used to dissipate the strike into the earth.
 17. 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.
 20. 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.
 22. CONCLUSION Grounding and Earthing systems form the first lineof
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.