Tuesday, December 23, 2014

Job interview and viva Topics for Electrical and electronics Engineers



Electrical engineering interview topic:Job interview and viva Topics for Electrical and electronics Engineers (Part-4).

In this topic we know about Power
System Stability,Steady State Stability,Static Stability,Dynamic
Stability and Steady State Stability Criterion

13. Power System Stability: 

 In the large
power system there might be some disturbance always. The system has the
tendency for the system to develop forces for bringing the system in a normal
or stable condition. The ability of the system to obtain the normal or stable
condition after getting disturbed is called Power System Stability.

The
stability has mainly two types: 
1. Steady State Stability.
2. Transient Stability.



14. Steady State Stability:  

The ability of
being stable after a small disturbance in the system is called Steady State
Stability.

The
Steady State Stability is concerned with the very small power changes .which
are changed gradually.

The
Steady State Stability has two types:
1. Static Stability
2. Dynamic Stability.



·       
Static
Stability:
 

In the Static Stability
there is a large duration phenomenon with small disturbance. This
is the inherent stability that can achieve with out the help of automatic
control devices.



·       
Dynamic Stability: 

In the Dynamic Stability there is a small
duration phenomenon with large disturbance. This Dynamic Stability
refers to artificial stability. This artificial stability is given to an
inherently unstable system by the help of automatic control devices.



15. Steady State Stability
Criterion:

The rate (dP/dδ) of the
differential power increased is obtained per differential load angle increased.
This are called as electrical stiffness or the synchronizing power
coefficient
of a synchronous machine. This is considered as the measure of
the stability of the system.
The Steady State Stability
has basically three Criterion or state.
When,
·       
(dP/dδ) > 0 ;
Direct State Synchronous Stability.
·       
(dP/dδ) = 0 ;
Steady State Stability.
·       
(dP/dδ) < 0 ;
The System is unstable.


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