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.
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
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.
4. What are the works involved in a load flow study?
(i)Representation of the system by single line diagram.
the impedance diagram using the information in single line diagram.
(iii)Formulation of network equations.
of network equations.
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.
are the different types of buses?
bus or PQ bus
bus or voltage controlled bus or PV bus
bus or Swing bus or Reference bus.
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.
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.
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.
is the need for slack bus?
bus is needed to account for transmission losses.
i. What are
the iterative methods used for solution of load flow problems? Guass-Seidal
(GS) method and Newton Raphson(NR) method.
ii. 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.
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.
are the advantages of GS method?
are simple and so the programmimg task is lesser. (ii)The memory requirement is
for small systems.
15. What are
the disadvantages of GS method?
large number of iterations to reach convergence.
2. Not suitable
for large systems.
time increases with size of the system.
16. What are
the advantages of NR method?
more reliable and the results are accurate.
Requires less number of iterations to reach convergence.
numbers of iterations are independent of the size of the system.
Suitable for large systems.
What are the disadvantages of NR method?
(i)The programming is more complex.
(ii)Memory requirement is more.
time per iteration is higher due to large number of calculations per