BRIEF DESCRIPTION OF EARTHING
EARTHING
The process of transferring the immediate the electrical energy directly to the earth by the help of
the low resistance wire is known as the electrical earthing.
Purpose:
To protect human lives as well as provide safe electrical devices and appliances from
leakage current.
To keep voltage as constant in the healthy phase (fault occurs on any one phase).
To protect Electric system and buildings from lightning
To serve as a return conductor in electric traction system and communication.
To avoid the risk of fire in electrical installation systems.
Earth pin of 3-pin lighting plug sockets and 4-pin power plug should be efficiently and
permanently earthed.
All metal casing or metallic coverings containing or protecting any electric supply line or
apparatus such as GI pipes and conduits enclosing VIR or PVC cables, iron clad switches, iron
clad distribution fuse boards etc should be earthed (connected to earth).
The frame of every generator, stationary motors and metallic parts of all transformers used
for controlling energy should be earthed by two separate and yet distinct connections with
the earth.
In a dc 3-wire system, the middle conductors should be earthed at the generating station.
, Stay wires that are for overhead lines should be connected to earth by connecting at least
one strand to the earth wires.
Types of Earthing:
1. Rod earthing -
2. Strip or wire earthing.
3. Pipe earthing
4. Plate earthing
Pipe Earthing
Most common system of earthing
A galvanized steel and a perforated pipe of approved length and diameter is placed vertically
in a wet soil in this kind of system of earthing.
Plate earthing
Either copper with dimensions 60cm x 60cm x 3.18mm (i.e. 2ft x 2ft x 1/8 in) or galvanized
iron (GI) of dimensions 60cm x 60cm x 6.35 mm (2ft x 2ft x1/4 in) is buried vertical in the
earth (earth pit) which should not be less than 3m (10ft) from the ground level
DESIGN AND ESTIMATION OF SUBSTATIONS:
Electric power is produced at the power generating stations, which are generally located far away
from the load centres. High voltage transmission lines are used to transmit the electric power from
the generating station to the load centres
Substations are the convenient place for installing synchronous condensers for the purpose of
improving power factor and it provide facilities for making measurements to monitor the operation
of the various parts of the power system.
CLASSIFICATION OF SUB STATIONS
The substations may be classified in according to service requirements and constructional features.
A. According to service requirements it is classified
Transformer sub-station :
o Those sub-station which change the voltage level of electrical supply are called TIF
s/s.
Switching sub-station:
o These sub-station simply perform the switching operation of power line.
Power factor correction S/S :
o These sub-stati on which improve the p.f. of the system are called power
factor correcti on s/s. These are generally located at receiving end s/s
EARTHING
The process of transferring the immediate the electrical energy directly to the earth by the help of
the low resistance wire is known as the electrical earthing.
Purpose:
To protect human lives as well as provide safe electrical devices and appliances from
leakage current.
To keep voltage as constant in the healthy phase (fault occurs on any one phase).
To protect Electric system and buildings from lightning
To serve as a return conductor in electric traction system and communication.
To avoid the risk of fire in electrical installation systems.
Earth pin of 3-pin lighting plug sockets and 4-pin power plug should be efficiently and
permanently earthed.
All metal casing or metallic coverings containing or protecting any electric supply line or
apparatus such as GI pipes and conduits enclosing VIR or PVC cables, iron clad switches, iron
clad distribution fuse boards etc should be earthed (connected to earth).
The frame of every generator, stationary motors and metallic parts of all transformers used
for controlling energy should be earthed by two separate and yet distinct connections with
the earth.
In a dc 3-wire system, the middle conductors should be earthed at the generating station.
, Stay wires that are for overhead lines should be connected to earth by connecting at least
one strand to the earth wires.
Types of Earthing:
1. Rod earthing -
2. Strip or wire earthing.
3. Pipe earthing
4. Plate earthing
Pipe Earthing
Most common system of earthing
A galvanized steel and a perforated pipe of approved length and diameter is placed vertically
in a wet soil in this kind of system of earthing.
Plate earthing
Either copper with dimensions 60cm x 60cm x 3.18mm (i.e. 2ft x 2ft x 1/8 in) or galvanized
iron (GI) of dimensions 60cm x 60cm x 6.35 mm (2ft x 2ft x1/4 in) is buried vertical in the
earth (earth pit) which should not be less than 3m (10ft) from the ground level
DESIGN AND ESTIMATION OF SUBSTATIONS:
Electric power is produced at the power generating stations, which are generally located far away
from the load centres. High voltage transmission lines are used to transmit the electric power from
the generating station to the load centres
Substations are the convenient place for installing synchronous condensers for the purpose of
improving power factor and it provide facilities for making measurements to monitor the operation
of the various parts of the power system.
CLASSIFICATION OF SUB STATIONS
The substations may be classified in according to service requirements and constructional features.
A. According to service requirements it is classified
Transformer sub-station :
o Those sub-station which change the voltage level of electrical supply are called TIF
s/s.
Switching sub-station:
o These sub-station simply perform the switching operation of power line.
Power factor correction S/S :
o These sub-stati on which improve the p.f. of the system are called power
factor correcti on s/s. These are generally located at receiving end s/s
