Why the impedance of the transformer is expressed in percentage?

The percentage impedance of a transformer is the volt drop on full load due to the winding resistance and leakage reactance expressed as a percentage of the rated voltage. It is also the percentage of the normal terminal voltage required to circulate full-load current under short circuit conditions.

Why is impedance a percentage?

Why is impedance given in a percentage? The percentage impedance of a transformer (Z\%) is the voltage drop on full load due to the winding resistance and leakage reactance expressed as a percentage of the rated voltage.

What should be the percentage impedance of transformer?

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Why we consider the percentage reactance of all the elements on a common kVA rating?

(ii) above that percentage reactance of an equipment depends upon its kVA rating. Generally, the various equipments used in the power system have different kVA ratings. Therefore, it is necessary to find the Percentage Reactance in Power System of all the elements on a common kVA rating.

How can the impedance of a transformer be increased?

As impedance is predominated by inductive reactance, the most effective way to change the impedance is often to change the number of turns. This will generally have an effect on the core dimensions and the winding resistance.

What is transformer percentage reactance?

Transformer reactance is often specified as a percentage, say 10\%. This is a per unit value expressed as a percentage on the power base of the transformer. Example: A 350 MVA, 230/20 kV transformer has leakage reactance of 10\%.

What is the percentage reactance?

Percentage Reactance of Power System: Percentage reactance can be defined in the same way as percentage resistance. It is the voltage drop across the given reactance expressed as percentage of normal voltage when carrying full-load current pertaining to normal rating, i.e., \%X = (IX/V) × 100 … (1.2)

Is high impedance good for transformer?

It is concluded that the high-impedance transformer has a great influence on the short-circuit current, bus voltage and power angle of the system, revealing the law of short-circuit current, bus voltage and power angle with short-circuit impedance.

Is lower impedance better for transformer?

The lower the impedance, the lower the voltage required to produce full load current. Lower imped- ance transformers allow higher fault currents to flow at a particular voltage. A voltage is applied to the primary with the secondary winding shorted (faulted).

Does transformer impedance change with temperature?

And since the temperature coefficients of resistance and reactance are usually positive, there is even a greater change in impedance Z = R + jX.