Types of Insulator
Pin type insulator
2.
Suspension type insulator
3.
Strain type insulator
4.
Shackle Type insulator
Theory of Insulator
The over head line conductor should be Supports on poles in such a way that current from conductor do not flow to earth through the supports this is achieved by searing line conductor to supports with the help of insulator. The insulator provided necessary insulator between line conductors.
The insulator should have the following property.
Insulator property
A.
High mechanical strength in order to with stand
conductor load wind load etc.
B.
High electrical resistance of insulator material
as in order to avoid leakage current to earth.
C.
High relative permittivity of insulator material
in order that dielectric strength is high.
D.
The insulator material should be non porous free
from impurities and Greeks otherwise the pa mites will be lower. The most
commonly used material for insulator of over head line is porcelain but and special
composition material are also used to a limited range. Porcelain is produced by
fixing air high temperature a mixture of kaolin fields and generate. It is
stronger mechanical then glass givers less trouble from leakage and is less affected
by changes of temperature.
Types of Insulator
1. Pin type Insulator
The pin type insulator fixed to the cross arm on the poles. There is
grove on the upper end of the insulator for housing the conductor passes
through this groove and is wound by annealed wire of the same material as
conductor pin type insulator are for transmission and distribution of electric
power voltage up to 33Kv become operating voltage of 33KV The Pin type
insulator because too bulky and hence in economy.
2. Suspension type Insulator
The cost of pin type insulator increase rapidly as the working voltage is
increased for high voltages.
It is usual practices to use Suspension type insulator.
A consist of no. of porcelain disc in connected in series by metal link
by in the form of spring. The conductor is suspended at the bottom end of this
string by the other end of the spring connected to the cross arm of the tower. Each
this design for a low voltage.
3. Strain type Insulator
When there is a dead end of the line or there is corner or sharp curve
the line realizes a greater tension. In order to relive the line excessive tension,
strain insulator are used . For low
voltage lines shackle insulators are used as strain insulator.
4. Shackle Insulator
In
early days the shackle type insulator were used as strain insulator but in the
present time distribution lines. Such insulators can be used either in
horizontal position or in vertical position
The main advantages of suspension type insulator
·
Suspension type of insulators are cheaper then
pin or other type insulator they on 33Kv
·
Each unit of suspension type insulator is design
for a low voltage .internally 11kv.
·
If one disk is damaged, the whole string does
not become use less because the damaged disk can be replace by another one.
·
The Suspension arrangement provided greater
flexibility to the time.
·
The suspension type insulators are generally
used with still tower.