When replacing a transformer with a higher kVA or lower impedance, what happens to the available fault current on the secondary?

When replacing a transformer with one that has a higher kVA rating or lower impedance, the available fault current on the secondary side increases. This is primarily due to two factors: the kVA rating and the impedance of the transformer.

A transformer’s kVA rating indicates its capacity to handle power. A transformer with a higher kVA can provide more current to the load. When a fault occurs, this means that the larger transformer has the ability to deliver more fault current because it can support higher power levels.

Additionally, a lower impedance transformer allows more fault current to flow. Impedance in the transformer acts like a resistance to the flow of current; thus, a lower impedance results in less restriction on current flow. This means that during a fault condition, more current is available to flow through the circuit.

Hence, the combination of a higher power capacity and lower impedance in the replacement transformer results in an increase in the fault current available on the secondary side. Understanding this concept is crucial for ensuring appropriate protective devices and safety measures are in place when modifications to transformer systems are made.