Short-Circuit Current Calculation for Transformers This section explains the calculation of short-circuit currents for two transformers with different voltage levels and power ratings. We will analyze both the high voltage (HV) and low voltage (LV) sides for each transformer.
Short-Circuit Current Calculation for Transformers
1. Calculation for 220/33 kV, 100 MVA Transformer
1.1. Short-Circuit Current on the 220 kV Side
1.1.1. Short-Circuit MVA Calculation
Short-Circuit MVA (Ssc) = Transformer
Rating (MVA) / Impedance (Zpu)
= 100 MVA / 0.1
= 1000 MVA
1.1.2. Short-Circuit Current Calculation
Short-Circuit Current (Isc) = Ssc / (√3 x
Vline)
= 1000 MVA / (√3 x 220 kV)
= 1000 / 380.5
≈ 2.63 Ka
1.2. Short-Circuit Current on the 33 kV Side
1.2.1. Short-Circuit MVA Calculation
Short-Circuit MVA (Ssc) = 1000 MVA
1.2.2. Short-Circuit Current Calculation
Short-Circuit Current (Isc) = Ssc / (√3 x V
line)
= 1000 MVA / (√3 x 33 kV)
= 1000 / 57.4
≈ 17.4 kA
2. Calculation for 110/33 kV, 16 MVA Transformer
2.1. Short-Circuit Current on the 110 kV Side
2.1.1. Short-Circuit MVA Calculation
Short-Circuit MVA (Ssc) = Transformer
Rating (MVA) / Impedance (Zpu)
= 16 MVA / 0.08
= 200 MVA
2.1.2. Short-Circuit Current Calculation
Short-Circuit Current (Isc) = Ssc / (√3 x
Vline)
= 200 MVA / (√3 x 110 kV)
= 200 / 190.2≈ 1.05 kA
2.2. Short-Circuit Current on the 33 kV Side
2.2.1. Short-Circuit MVA Calculation
Short-Circuit MVA (Ssc) = 200 MVA
(remains the same)
2.2.2. Short-Circuit Current Calculation
Short-Circuit Current (Isc) = Ssc / (√3 x
Vline)
= 200 MVA / (√3 x 33 kV)
= 200 / 57.4
≈ 3.48 kA
3. Summary of Short-Circuit Currents
For the 220/33 kV, 100 MVA Transformer:
At 220 kV: Short-circuit current is approximately
2.63 kA.
At 33 kV: Short-circuit current is approximately
17.4 kA.
For the 110/33 kV, 16 MVA Transformer:
At 110 kV: Short-circuit current is approximately
1.05 kA.
At 33 kV: Short-circuit current is approximately
3.48 kA.