What is Subtransient reactance?

Subtransient reactance is the reactance of the motor during the first cycle of the short-circuit. Transient reactance is the reactance of the motor during the remainder of the short-circuit. The computer program supplies typical values of subtransient and transient reactance for motors.

What is the significance of transient and Subtransient reactance?

Transient and sub-transient reactance are generally the terms which appear in the calculation of fault current. Subtransient Reactance, usually denoted as X”d, is the reactance used to determine the current during the first cycle after the occurance of the fault.

How do you calculate synchronous reactance of a generator?

Saturated Synchronous Reactance Hence, the value of the synchronous reactance to be used in a given problem should be one calculated at the approximate load on the alternator. If the alternator is connected to the infinite bus, then its terminal voltage remains the same at the bus value. ??(sat.) =??????=??+???(sat.)

What is Subtransient reactance of synchronous machine?

The subtransient reactance of a synchronous generator is that reactance which, coupled vectorially with the relatively negligible resistance, determines the initial symmetrical value of current that will flow in the stator winding upon sudden application of a short circuit at its terminals when the machine is running …

What is direct axis Subtransient reactance?

Sub transient reactance Xd” is the apparent reactance of the stator winding at the instant short circuit occurs, and it determines the current flow during the first few cycles of a short circuit.

How do you find the XR ratio of a generator?

The X/R ratio is the amount of reactance X divided by the amount of resistance R, which also happens to be the Tangent of an angle created by reactance and resistance in a circuit.

What is Subtransient transient and steady state?

There are three periods of time: – Sub-transient period: first cycle or so after the fault – AC current is very large and falls rapidly; – Transient period: current falls at a slower rate; – Steady-state period: current reaches its steady value.

What is synchronous reactance?

As described in the armature winding notes, synchronous reactance is a combination of armature winding leakage reactance and a reactance used to represent armature reaction. The synchronous machine tests give the induced voltage and the current when armature reaction is greatest, for a range of field current values.

What is Subtransient transient and steady-state?

What is XR ratio used for?

First, X/R ratio is simply the ratio of the system reactance to the system resistance, looking back to the power source from any point in a power circuit, assuming that a short circuit is applied to the system at that point. It is another way of stating the power factor of the source system.