Professional Engineers: INSULATORS

INSULATORS

As we know their is no insulation on over head lines and before placing them on towers first their is proper insulation installed on tower so to prevent direct contact between and conductor

The insulators should have the following properties

Insulator should have high mechanical strength to bear air pressure and greater deviation of line
Insulator material should not be porous
Insulator should have high resistance , so to prevent line from leakage current
Material from which insulator is made should be pure
less deterioration

Mostly the material which is used for insulator making are porcelain ,glass and stealth

Porcelain Insulators

The porcelain insulators are made of ceramic material they are free from

holes
pores
cracks

The porcelain insulators are hard and have shiny surface and due to glee zing rain drops not stay on surface of insulator their dielectric strength is 60KV/cm

Glass Insulators

For making glass insulators first the glass heats until it melts when it melts completely then it is used for manufacturing of glass insulator

the dielectric strength of glass insulator is 140KV/cm , the advantage of glass insulator is they can be easily identified if flash over occurs

Stealth Insulators

They are made of magnesium oxide and silica , they are widely use in hilly areas due to its strength these insulators are also used where high degree of deviation is required in line direction

TYPES OF INSULATORS

PIN TYPE INSULATORS

A pin type insulator is a type of insulator where this insulator is installed on tower cross arm through pin , Their is grove on upper side of insulator where conductor will be placed , The material on which conductor should be the same as conductor material

The highest voltage for which pin type insulators are used is 33 kv beyond this voltage by further increasing its cost,shape and its efficiency also increase so beyond 33 kv these insulators are not favorable These insulator design in a way that before puncturing the spark over occurs so line can be saved from permanent damage

The safety factor of pin type insulator is 10 ,safety factor is the ratio of working voltage to the spark over voltage

As shown in graph numbers of Sheds are made to prevent leakage current path,shells are made to decrease width of a insulators these shells are cemented with each other

Mostly now in pin type insulator the resistance and capacitance of a insulator kept constant to decrease corona effect

the advantage of pin type insulator is

Ground clearance is no issue for these insulators

Mostly used in 11kv

the main disadvantage is once puncture so insulator will be changed completely as they are used mostly in 11 kv so this is also one disadvantage because it cant be increased

Disc type insulators

As from its name it is clear these type of insulators are in disc shape

There are two types of disc insulator

1.Suspension type insulator

This type of insulator is mainly used in HV systen, one disc is used for 11 kv so by connecting number of disc this voltage can be increased ,by connecting number of insulators in a string form knows as string insulator shown in figure

The suspension upper side will be connect with the tower while its lower end will be connect with the line conductor video shows suspension type insulator

The advantage of these insulators is if one disc puncture so no need for a full change just change that specific insulator

In this type insulator ground clearance is required

2.Strain insulator

Mostly used in

where high angle of deviation required in line conductor direction
where dead end comes

In strain insulators the strings used are in vertical position . the main reason for their use is their mechanical strength which is 50% more than suspension type insulator

Selection of Insulator