Ninth lecture about power system protecion

to continue the lecture about current transformer :

Accuracy Of Current transformer :

• 500 / 1 : called C.T Ratio ( At normal operation ).
• 5000 / 10 : At short circuit ( At fault ) .
• Ratio error = Normal Operating / Fault Operating .
• Saturation Factor = Limit of Primary current / Rated primary current .

Whenever the safety factor  increase , whenever the protection is better , so if the 

rated current increase , the primary not saturated .

C.T Burden (V.A) :

It's total load for the current transformer , have impedance for its winding and the 

out cables from it to complete the protection system and each of them have 

impedance. 

Z = VA / I^2 .

Class of Current transformer :

class X      :  Differential Relay .

Class 5P   : instantaneous over current Relay .

Class 10P :  IDMT Over Current Relay .

( Whenever decrease the number of the C.T , it be more accuracy ) .

 The protection have two type :

Apparatus protection :

It's  damage in particular equipment .

• Transmission line protection .
• Feeder protection .
• Bus Bar protection .

System Protection :

Damage produced in all of the system .

• Under frequency .
• Over frequency .
• loss of synchronism .
• Over excitation .
• Under excitation . 
 

 

To continue our course of Power Protection System :

[ The Tenth lecture of Power System Protection ]

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