Power System Analysis - Power Flow Analysis - Important Short Questions and Answers: Power Flow Analysis

1. What
is power flow study?

The study
of various methods of solution to power system network is reffered to as power
flow or load flow study.

2. What
are the informations that are obtained from a load flow study?

The
information obtained from a load flow study are magnitude and phase of bus
voltages, real and reactive power flowing in each line and the line losses. The
load flow solution also gives the initial conditions of the system when the
transient behaviour of the system is to be studied.

3. What
is the need for load flow study?

The load
flow study of a power system is essential to decide the best operation of
existing system and for planning the future expansion of the system. Also
essential for designing a new system.

Ø
What are the works involved in a load flow study?
(i)Representation of the system by single line diagram.

(ii)Determining
the impedance diagram using the information in single line diagram.
(iii)Formulation of network equations.

(iv)Solution
of network equations.

Ø
What are the quantities that are associated with
each bus in a system?

Each bus
in a system are associated with four quantities and they are real
power,reactive power, magnitude of voltage and phase angle of voltage.

Ø
What are the different types of buses? (i)Load bus
or PQ bus

(ii)Generator
bus or voltage controlled bus or PV bus (iii)Slack bus or Swing bus or
Reference bus.

ØDefine
voltage controlled bus.

A bus is
called voltage controlled bus if the magnitude of voltage and real power are
specified. The magnitude of voltage is not allowed to change.

8. What
is PQ bus?

A bus is
called PQ are load bus when real and reactive components of power are specified
for the bus. In a load bus the voltage is allowed to vary within the
permissible value.

9. What
is swing bus?

A bus is
called Swing bus when the magnitude and phase of the voltage are specified for
it. Swing bus is the reference bus for load flow solution and it is required
for accounting line losses.

10. What
is the need for slack bus?

The slack
bus is needed to account for transmission losses.

Ø What are
the iterative methods used for solution of load flow problems? Guass-Seidal
(GS) method and Newton Raphson(NR) method.

Ø Why do we
go for iterative methods to solve load problems?

The load
flow equations are nonlinear algebraic equations and so explicit solution is
not possible. The solution of nonlinear equations can be obtained only by
iterative numerical techniques.

13. When
the generator bus is treated as load bus?

If the
reactive power of a generator bus violates the specified limits then the
generator bus is treated as load bus.

14. What
are the advantages of GS method?

(i)Calculations are simple and so the programmimg task is lesser.

(ii)The memory requirement is
less.

(iii)Useful
for small systems.

15.
What are the disadvantages of GS method?

(i)Requires
large number of iterations to reach convergence.

(ii)
Not suitable for large systems.

(iii)
Convergence time increases with size of the system.

16.
What are the advantages of NR method?

(i)Faster,
more reliable and the results are accurate.

(ii)
Requires less number of iterations to reach convergence.

(iii)The
numbers of iterations are independent of the size of the system.

(iv)
Suitable for large systems.

17. What
are the disadvantages of NR method?

(i)The
programming is more complex.

(ii)Memory
requirement is more.

(iii)Computation
time per iteration is higher due to large number of calculations per
iterations.

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Power System Analysis : Power Flow Analysis : Important Short Questions and Answers: Power Flow Analysis |

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