Need of Arcing Horns and Guard Ring

1.  Need of Arcing Horns and Guard Ring

In transmission line, In the event of flash-Over the insulators may get damaged (or) cracked due to the heat of the arc. Inorder to protect the insulators from the flash-over a guard ring in conjunction with arcing horn is employed.

Arcing horn is fixed at the top end of string serves as a shield from flash-over. The guard ring is connected electrically to the line conductor. The combination of the arcing horn and guard ring provides a path through the air medium and discharges the energy contained in the abnormal voltage and hence it saves the insulator string.

The Fig. shows the arrangement of the arcing horn on a 7-unit string of suspension insulators.

Causes of Failure of Insulator

The following are the main causes of failure of insulators used in transmission and distribution lines, namely

1.      Cracking of insulators.

2.      Use of defective insulator material in a string of insulator may leads to occurrence of puncture.

3.      Use of low porosity material to the insulator material will cause to absorb the moisture and hence, it will cause to decrease the insulation resistance of the material therefore the insulators may cause to failure in operation.

4.      Due to falling of large size birds causes formation of arc between conductor and insulator and hence it may result in failure of the insulator.

5.      Flash over caused by unequal expansion of the porcelain material.

6.      Due to improper glaze i.e., the insulator material is not properly glazed, the water will stick over which will result into deposition of dust etc., hence it reduces the flash over voltage.

7.      Due high mechanical stresses the defective insulating disc may get damaged hence total arrangement may get failired.

Purpose of Arcing Horns  and Guard Ring :

To protect the insulators from the flash over.