What is the available fault current at a transformer with 1,000 kVA and 1.3% impedance?

To determine the available fault current at a transformer, you can use the formula:

[ \text{Fault Current (I)} = \frac{MVAsc}{\sqrt{3} \times V_{line}} ]

Where:

• ( MVAsc ) is the apparent power of the transformer in kVA (1,000 kVA in this case).

• ( V_{line} ) is the line-to-line voltage of the transformer.

• The percentage impedance is also needed to adjust for the transformer’s impedance in determining the effective fault current.

First, you need to convert the transformer rating from kVA to an actual fault current. The formula incorporates impedance, and the fault current needs to be adjusted based on that.

Given that the transformer's impedance is 1.3%, you can calculate the fault current as follows:

1. Convert percentage impedance to a decimal: 1.3% = 0.013.

2. Calculate the transformer’s short-circuit current using the formula:

[ \text{Short-circuit current (Isc)} = \frac{\text{Rated kVA} \times 1000}{\text{Impedance} \times \sqrt{3} \times V_{