What is difference between transient and Subtransient?

The reactance during these first two or three cycle is least and the short circuit current is high. This reactance is called subtransient reactance and is denoted by X”. This state is called the Transient State and the reactance in this state is called transient reactance X’.

What is the main difference between the inrush current and fault current?

If output between 1 to 2 that means there is Inrush current. If output between 2 to 3 that means there is LG Fault current. If output between 3 to 4 that means there is LL Fault current.

What is the difference between transient and Subtransient reactance?

During first few cycles reactance of system/synchronous machine is least and short circuit current is highest. This stage is called subtransient reactance. This state is called transient reactance and is denoted by X’. Finally transient dies out and current reaches the steady sinusoidal state.

What is transient and Subtransient current?

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. • It is possible to determine the time constants for the sub-transient.

What is sub transient?

First, “subtransient” refers to the fact that this quantity operates extremely fast—faster than even “transient.” In technical terms, the subtransient time period lasts from about one to three cycles, which is from 16.7 milliseconds to 50 milliseconds (assuming a power frequency of 60 Hz).

What is sub transient state?

The first few cycles come under sub-transient state. After a first few cycles, the decrement in the r.m.s. value of short circuit current is less rapid than. the decrements during the first few cycles. This state is called the Transient State and the. reactance in this state is called transient reactance X’.

How can you distinguish between magnetizing inrush current and fault?

Figure 1. Typical inrush current waveform [7] . the false differential currents caused by magnetizing inrush and transformer over excitation. Figure 2 shows a typical differential relay connection for power transformer protection.

How long does motor inrush current last?

These currents can be as high as 20 times the steady state currents. Even though it only lasts for about 10ms it takes between 30 and 40 cycles for the current to stabilize to the normal operating value.

What do you mean by sub transient reactance?

The subtransient reactance, X”d, is the generator internal impedance element that is effective in the first cycles of a transient load event and determines the magnitude of the instantaneous fault current from the generator.

What is a sub transient fault?

The term “subtransient reactance” is denoted by the symbol X”d and is used to calculate available short-circuit generator fault currents. The subtransient reactance is a transient effect that’s directly related to the electromagnetic relationships between the various physical components of the generator.

What is a transient fault?

Transient faults include the momentary loss of network connectivity to components and services, the temporary unavailability of a service, or timeouts that arise when a service is busy. These faults are often self-correcting, and if the action is repeated after a suitable delay it is likely to succeed.

Which fault has highest current level among the following types of faults?

Among the given faults, LLLG or 3 phase faults are most severe. LG or line to ground fault is least severe. Line to line fault is more severe than line to ground fault while double line to ground fault is one level severe than LL.

What is subtransient fault current?

Subtransient fault current is that fault current level during a specific time period of fault current. It is a part of the fault current, not a separate type really.

What is the difference between steady state and sub transient current?

Steady-state period: current reaches its steady value. The AC current flowing in the generator during the sub-transient period is called the sub-transient current, this current can be as much as 10 times the steady-state fault current.

What is the sub-transient current in a generator?

Fault current transients in machines The AC current flowing in the generator during the sub-transient period is called the sub-transient current and is denoted by I”. The time constant of the sub-transient current is denoted by T” and it can be determined from the slope. This current can be as much as 10 times the steady-state fault current.

What is the difference between transient AC and sub-transient DC?

The current can be represented as a transient DC component added on top of a symmetrical AC component.Before the fault, only AC voltages and currents are present, but immediately after the fault, both AC and DC currents are present. Sub-transient period: first cycle or so after the fault – A…