- The sudden rise in voltage for a very short duration on power system is known as voltage surge or transient voltage.
- The sudden rise in excessive voltage which damages the electrical equipment of an installation.
- The overvoltage in the lines may occur because of a rise in voltage between both phases or between phase and ground.
How does Surge occur?
There are many reasons that may create the surge voltage in the power system and we can classified these in two terms "Internal cause" and "External cause"
Causes of Surge
- Adding a load to the system
- Removing a load from the system
- Insulation failure
- Arcing ground
- Resonance
- Lightning
Insulation failure
If the insulation of any power cable get damaged then the potential at that fault point falls suddenly from maximum to zero as a result a negative voltage wave with very steep front in the form of surges generated to the both direction.
Lightning
"An electrical discharge between cloud and earth, between clouds or between the charge centres of the same cloud is known as lightning"
When the lightning strikes a line, it causes a surge. this surge rushes along the line. In most of the cases, such surges may cause the line insulators to flush over and may also damage the nearby transformers, generators or other equipment connected to the line if the equipment don't have proper protection.
