How is transformer differential protection calculated?
Calculations for OLTC tap setting +10% Full load Current for 220 kV %( HV Side) Winding at +15% = MVA / (√3*1.10*kV) =100*10^6/ (√3*220*1.10*10^3) = 238.57A Current on CT Secondary (HV) = Rated Current (HV Side)/CT Ratio = 228.20 /300 = 0.795 A Current on ICT Secondary (HV) = √3*(Current on CT Secondary (HV)/ …
How do you calculate protection relay?
Calculation of Over Current Relay Setting:
- Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480 Amp.
- Required Over Load Relay Plug Setting= Over Load Current (In) / CT Primary Current.
- Required Over Load Relay Plug Setting = 480 / 600 = 0.8.
What happens if CT saturates?
If a CT has reached saturation and a switch is opened to remove the primary current, we would expect the magnetic field (H) to disappear and the flux density (B) to reduce to zero. However, flux density does not go to zero when the primary current stops flowing.
What is high impedance differential protection?
High impedance protection system is a simple technique which requires that all CTs, used in the protection scheme, have relatively high knee point voltage, similar magnetizing characteristic and the same ratio. … Thus, the high impedance differential protection responds to a current flowing through the measuring brunch.
On which principle differential protection is based?
2.4 Principle of Differential Protection
Differential protection is based on the fact that any fault within an electrical equipment would cause the current entering it, to be different, from the current leaving it.
What is the percentage of winding protected by differential protection?
The percentage differential protection does not respond to the external faults and overlords. It provides complete protection against phace to phace faults it provides protection against ground fault to about 80 to 85% the generator windings.