What is transient Subtransient 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 are the transient conditions in an alternator?

In abnormal operation, the alternator may be subjected to transient conditions which cannot be explained from steady-state theory. These transients may occur from- (i) Switching (ii) Sudden changes of load, (iii) Sudden short circuit (either line-to-line or line-to-neutral or from a symmetrical short circuit).

What is transient and transient period?

Transient Period: Transient Period refers to the duration of process under which variables are changing in respect of particular time period. The word transient is used for short run duration along with gradual changes over time.

What is a transient system?

A system is said to be transient or in a transient state when a process variable or variables have been changed and the system has not yet reached a steady state. The time taken for the circuit to change from one steady state to another steady state is called the transient time.

What is XD in generator?

Xd’ is the transient reactance and is used to calculate the next several cycles of short circuit current (still has some DC offset, although not as much as the first few cycles). Xd is used in the calculation of steady state current.

Why do circuit breakers operate in 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’. The circuit breaker contacts separate in the transient state.

What are transient conditions?

Transient Condition means an operating period, excluding normal start-up, normal shut-down, and emergency shut-down, during which the operating parameters of the Facility fall outside the values specified by the Owner for normal steady state operating conditions. Sample 2. Sample 3.

What is meant by transient condition?

Related Definitions Transient Condition means an operating period, excluding normal start-up, normal shut-down, and emergency shut-down, during which the operating parameters of the Facility fall outside the values specified by the Owner for normal steady state operating conditions.

What is direct axis transient reactance?

Direct-axis transient reactance (Xd’): The quotient of the initial value of a sudden change in that fundamental AC component of armature voltage , which is produced by the total direct-axis primary flux, and the value of the simultaneous change in fundamental AC component of direct-axis armature current, the machine running at rated speed and the high decrement components during the first cycles being excluded.

What is subtransient reactance?

A transient is a short-lived burst of energy in a system caused by a sudden change of state. Transient and sub-transient reactance are generally the terms which appear in the calculation of fault current.

What is the steady state mean in circuit?

In electronics, steady state is an equilibrium condition of a circuit or network that occurs as the effects of transients are no longer important. Steady state is reached (attained) after transient (initial, oscillating or turbulent) state has subsided. During steady state, a system is in relative stability.

What is synchronous reactance?

The Synchronous Reactance (XS) is the imaginary reactance employed to account for the voltage effects in the armature circuit produced by the actual armature leakage reactance and by the change in the air gap flux caused by the armature reaction.