Switchgear & Protection | Name internal and external causes of system over-voltages.

 Internal Causes of System Over-voltages :  

1) Switching surges 

2) Arcing ground 

3) Insulation failures 

4) Resonance  

External Causes of System Over-voltages: 

1) Direct Lightning strokes 

2) Lightning discharge near the line 

3) Voltage induced  due to change in atmospheric condition 

4) Voltage induced due to frictional effects of small particles such as dirt, dust, snow etc.