over voltage due to internal causes

~  When something happens in the circuit condition of the power system,

~  oscillations are generated due to the inductance and capacitance of the circuit and consequently the voltage of the system increases.

~  This voltage is almost twice the voltage of the system.

~  Thus the overvoltage due to internal cause is much less than the overvoltage due to lightning.

~ If the insulation of the equipment of the system is designed properly, there is no need to provide extra protection for over-voltage due to internal reasons.


                                          internal causes of over voltage

1) switching serge 

2) Arcing grounds

3) resonance


1) switching serge : When a line that is not loaded on the line is switched on, 

~ a traveling wave is generated in the line.  

~ This travels on the wave line and reaches the second egg.

~ From there the supply ends without changing the sign.

~ This causes the voltage to double.

~ This happens for a very short time, as the voltage returns to normal in a short period of time due to the loss of the line.  

2) Arcing grounds : In a three-phase line when neutral is not interpreted, if a line-to-ground fault occurs, the arc becomes ground bean.  

~ This produces a voltage oscillation of three to four times the normal voltage.

3) resonance : When the inductive reaction of a line is equal to its capacitive reaction then the net impedance of the line is at least equal to its resistance.

~ This time the series resonates.  

~ Since the inductive reactions and capacitive reactions of the line at the power frequency are not the same, there is no possibility of resonance under normal circumstances,

~ but harmonics are produced if the waveform of the EMF of the generator is distorted.

~ Thus, because of the fifth or more multiple harmonics, the values ​​of X and X are the same and resonance can occur.  Resonance causes overvoltage.


                                        when switching on loaded line


~ The voltage of the line also increases when the line is switched on or off with the load.

~ Suppose the loaded line is switched on. 

~ This time the line produces a voltage of 27.

~ Where 2, is the natural impedance of the line. 

~ Natural impedance is Z, VE and its value depends not on the load but on the constant of the line. 

~ That is the instantaneous value of the current at the time the circuit opens.

~ Now suppose the natural impedance of the circuit is 800. 

~  And the line is turned off when the current is maximized.  

~ The current value at the time of switching off is 50 A (RMS).

 ~  So the super imposed voltage