Describe with reasons the failure of porcelain insulators.

Describe with reasons the failure of porcelain insulators.
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1 Answer

Answer :

The reasons the failure of porcelain insulators : - 

1. Manufacturing Defect:- Insulator may fail due to manufacturing defect. So, it must be tested before use. 

2. Uneven Expansion and Contraction:- Insulator is manufactured by using combination of material. For. eg: porcelain, glass, cements and also attachment steel is used. Co-efficient of expansion and contraction of each material is different. So, there is possibility of cracking of insulator, so it may fail. 

3. Mechanical Stress:- Due to mechanical stress of wind insulator may fail. 

4. Porous:- Porcelain is porous material. So, if insulator is not glazed properly then direct dust will accumulate on insulator and It will absorb moisture from air, so reduces resistance of insulation. Hence leakage current increase which increases temperature of insulator. It may cause failure of insulator. 

5. Flashover due to lightning stroke:- If lightning stroke directly attacks on insulator than there is flash over and causes failure of insulator.  

6. Flash over due to large birds or similar objects:- Large birds or similar objects causes short circuit resulting in flash over and causes of failure insulator.  

7. Flash over caused due to dust deposition:- Transmission line running over/near dusty area for eg: coal mine, large stone crusher, cement factory etc. Dust will deposit on insulator which reduces clearance between two conductors. So, there is possibility of flash over and causes failure of insulator. 

 8. Wrong Selection:- If 11 KV insulators are used for 22 KV, then it causes failure of insulator. 

9. Rough Handing:- Due to rough handling of insulator during transportation, construction of line work etc causes failure of insulator. 

 10. Ageing Effect:- Due to continuous use of insulator for a long period, its dielectric strength reduces. So, it may fail insulator. 
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