Friday, August 22, 2014

Suspension Type Insulators; Suspension Insulators Advantages and Disadvantages

Suspension Insulator

As discussed earlier Pin type insulators are useful for using at 33KV and above 33 KV it becomes uneconomical to use Pin type insulators. This is mainly due to increased size, Weight of pin type insulator. Thus it become very difficult for handling and replacement of Such insulators. Due to above stated problem Suspension type insulators are developed.

It is quite interesting to know about suspension insulators, Suspension type insulators consists of  numbers of insulators are connected in series to form a string and the line conductor is carried by the bottom most insulator.

Each insulator of a suspension string is called disc insulator because of their disc like shape. Suspension type insulators are very economical to use and advantages and disadvantages for the suspension type insulators are as below:-

Suspension Insulator Advantages:-

1. In suspension type insulators each disc is designed for normal voltage rating 11KV and 15KV on the higher voltage side. So by using different numbers of discs, a suspension string can be made suitable for any voltage level. E.g. if there is transmission voltage of 66KV then there will be 6 discs in suspension type insulator.

2. It becomes easy to replace any disc insulator of suspension type insulator as every disc is of small size.

3. Suspension type insulators provide more flexibility to the line. The connections at the cross arm is such that insulator string is free to swing in any direction and will take position where mechanical stress is minimum.

4. As the 
electric current carrying conductors are suspended from supporting structure by suspension string, the height of the conductor position is always less than the total height of the supporting structure. Therefore, the conductors may be safe from lightening.
5. It become easier with suspension type insulators to meet demand as additional disc can be added with rising voltage.
6. The suspension type insulators are generally used with steel towers. As the conductors run below the earthed cross-arm of the tower, therefore, this arrangement provides partial protection from lightning.

Disadvantages of Suspension Insulator

1. One of the main disadvantage of Suspension insulator string is  the every disc of suspension type insulator is costlier than pin and post type insulator

2. Suspension string requires more height of supporting structure than that for pin or post insulator to maintain same ground clearance of electric current conductor.

3. The amplitude of free swing of conductors is larger in suspension insulator system, hence, more spacing between conductors should be provided.