What is short circuit current of transformer?
Transformer impedance is determined as follows: The transformer secondary is short circuited. Voltage is increased on the primary until full load current flows in the secondary. This applied voltage divided by the rated primary voltage (times 100) is the impedance of the transformer.
How do you calculate fault current in a transformer?
Step 1: Determine Full Load Amps (FLA) You can determine the Full Load Amps of a transformer with the following formula: FLA = VA / L-L Voltage x 1.732, so using the example above we get FLA = 1000000 / 480 x 1.732 or 1000000 / 831.36 = 1202.84 (note the conversion from kVA to VA, 1000 x 1000 = 1000000).
Why do we need short circuit calculation?
Short circuit study is used to determine the available fault current or short circuit current at each point in the system. A Short Circuit Analysis will help to ensure that personnel and equipment are protected by establishing proper interrupting ratings of protective devices (circuit breaker and fuses).
How do you perform a short circuit test on a transformer?
The test is conducted on the high-voltage (HV) side of the transformer where the low-voltage (LV) side or the secondary is short circuited. A wattmeter is connected to the primary. An ammeter is connected in series with the primary winding.
How do you calculate short circuit current of a transformer?
The transformer short circuit current is calculated as follows:
- Ifault−actual=Sbase×100√3×Vbase×Z%
- where Ifault−actual is in kA, Sbase is in kVA, Vbase is in V, and Z% is in percentage.
What is 3phase short-circuit?
The most common type of short circuit in a three phase system is a single conductor to earth fault (Fig 1. Phase-to-earth). This is when one of the conductors in a circuit comes into contact with an earth. The next most common type of short circuit is a phase to phase or conductor to conductor fault (Fig 2.
What is short-circuit power factor?
Power factor (PF) is sometimes specified instead of X/R. This must be the short circuit power factor. Power factor is defined as the cosine of the angle between voltage and current. X/R is the tangent of this same angle. X/R can be found from power factor by taking the tangent of the inverse cosine of the power factor.