Transformer Short Circuit Calculation

Welcome to our transformer short circuit calculation! This page will allow you to undertake a transformer short circuit current calculation using the transformer rating in kVa, the voltage rating of the secondary winding and the per unit impedance of the transformer in percentage. Let's begin! 
CalculationInputs﻿﻿S, kVA
:10kVA​
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﻿﻿V (LL) 
:415volts​
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﻿﻿Z % 
:10​
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Output﻿﻿I (3P) 
:0.139124628ampere​
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﻿﻿I (PP) 
:0.120481928ampere​
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﻿﻿I (PN) 
:0.0488142269ampere​
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﻿﻿I (PE) 
:0.0488142269ampere​
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Z% to find Zn﻿﻿Z0 
:0.085ohms​
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﻿﻿Z1
:0.1ohms​
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﻿﻿Z2 
:0.1ohms​
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ExplanationIn a transformer, fault current refers to the amount of current that flows through the transformer when there is a fault or short circuit in the system. This current can be much higher than the normal operating current of the transformer. It can cause damage to the transformer and other electrical equipment if it is not properly protected.
Several types of fault conditions can occur in a transformer, such as a short circuit between the primary and secondary windings, a short circuit between the windings and the transformer's core, or an external short circuit on the secondary side of the transformer. Each of these fault conditions can result in a different fault current magnitude and waveform.
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💡Understanding and analysing these fault currents is important to properly design and protect the transformer and the electrical system.
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3 Phase fault (A)=I3P=S3 ⋅ VLL ⋅Z13 \: Phase \: fault \: (A)=I_{3P} = \frac {S} {\sqrt{3} \: \cdot \: V_{LL} \: \cdot Z_{1}  }3Phasefault(A)=I3P​=3​⋅VLL​⋅Z1​S​
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Phase to phase fault (A)=Ipp=SVLL⋅(Z1 + Z2)Phase \: to \: phase \:fault \: (A)=I_{pp} = \frac {S} {V_{LL} \cdot (Z_{1} \: + \: Z_{2} )} Phasetophasefault(A)=Ipp​=VLL​⋅(Z1​+Z2​)S​
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Phase to neutral fault (A)=Ipn=3⋅S3⋅VLL⋅(Z0+Z1+Z2)Phase \:to \:neutral \: fault \: (A)=I_{pn} = \frac {3 \cdot S } { \sqrt {3} \cdot V_{LL} \cdot (Z_{0} + Z_{1} + Z_{2} ) } Phasetoneutralfault(A)=Ipn​=3​⋅VLL​⋅(Z0​+Z1​+Z2​)3⋅S​
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Phase to earth fault (A)=Ipe=3⋅S3⋅VLL⋅(Z0+Z1+Z2)Phase \: to \: earth \: fault \: (A)=I_{pe} = \frac {3 \cdot S} { \sqrt{3} \cdot V_{LL} \cdot (Z_{0} + {Z_{1} + Z_{2} )  } } Phasetoearthfault(A)=Ipe​=3​⋅VLL​⋅(Z0​+Z1​+Z2​)3⋅S​
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Where: 
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S=Transformer Rating (kVA)VLL=Voltage Rating(V)Z%=Per unit impedance of TransformerZ0=Zero Sequence Impedance (Ω)Z1=Positive Sequence Impedance (Ω)Z2=Negative Sequence Impedance (Ω) \\S = Transformer \: Rating \: (kVA) \\ V_{LL} = Voltage \: Rating (V) \\ Z \%  = Per \: unit \: impedance \: of \: Transformer \\ Z_{0} = Zero \: Sequence \: Impedance  \: (Ω) \\ Z_{1} = Positive \: Sequence \: Impedance  \: (Ω) \\ Z_{2} = Negative \: Sequence \: Impedance \: (Ω)S=TransformerRating(kVA)VLL​=VoltageRating(V)Z%=PerunitimpedanceofTransformerZ0​=ZeroSequenceImpedance(Ω)Z1​=PositiveSequenceImpedance(Ω)Z2​=NegativeSequenceImpedance(Ω)
Zero, Positive and Negative Sequences (Zn)
👉 Important note!
Related ResourcesCheck out our full library of CalcTree templates here!
Capacitive Reactance
Ohm's Law 
Power (DC circuits)
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