The slack bus is also known as the swing bus or reference bus.
The voltage magnitude |V| and phase angle |δ| are specified here.
This bus is selected to provide additional real and reactive power to supply the transmission losses.
Ques 82. The range of accelerating factor is
10 to 20
20 -30
15.5 -20.2
1.6 -1.8
Answer.4. 1.6 to 1.8
Explanation:
For Gauss-seidel load flow method, an acceleration factor normally used to lead fast convergence as it reduces the number of iterations.
After doing repeated load flow it has been observed that normally it work well for the acceleration factor of 1.6 to 1.8.
Ques 83. The advantage of the Newton Raphson method is
Less number of iteration
Less computation Time
Applicable for large power system network
All of the above
Answer.4. All of the above
Explanation:
Newton Raphson’s method is perhaps the best-known method for finding successively better approximations to the zeroes (or roots) of a real-valued function.
The advantages of the Newton-Raphson method are
Newton Raphson method needs less number of iterations to reach convergence, hence take less computation time.
The accuracy of the N-R method is more and convergence is not affected by the choice of slack bus.
The accelerating factor is not required in the Newton Raphson method.
The N-R method is best suited for a large power network.
Ques 84. The disadvantages of the Newton-Raphson method is
Large computer memory required
Computer programming is difficult
Per iteration time is large
All of the above
Answer.4.All of the above
Explanation:
The disadvantages of the Newton-Raphson method are
It requires more memory space.
It requires more number of calculation, therefore, programming is complex.
The time requires per iteration is more in the Newton-Raphson method.
Ques 85. The advantages of the Gauss-Seidel method is
The less computational time required
Simplicity in technique
Less computer memory required
All of the above
Answer.4. All of the above
Explanation:
The advantages of the Gauss-Seidel method are:-
A simple algebraic equation is used hence it requires less number of arithmetic operation to complete iteration and therefore the time required for each iteration is less
The need for computer memory is less.
This method is most suitable for small size networks.
Ques 86. The disadvantages of the Gauss-seidel method are
A large number of iteration required
Slow convergence rate
Inefficient for large system network
All of the above
Answer.4. All of the above
Explanation:
The disadvantages of the Gauss-Seidel method are:-
This method is not applicable to large power system.
The convergence is affected by the choice of slack bus.
It requires more number of iteration to obtain the solution.
The rate of convergence is slow.
It required an accelerating factor for convergence.
Increase in the number of iteration with an increase in the number of buses.
Z Matrix can be formed by either inverting the Ybus matrix or by using Z bus building algorithm.
Z matrix is a full matrix i.e zero elements in Ybus become non-zero elements in the corresponding Zbus.
Ques 88. Which of the following matrix is used for load flow studies?
Unit matrix
Null matrix
Y bus matrix
Z bus matrix
Answer.3. Y bus matrix
Explanation:
Y bus is a bus admittance matrix that is used (generally) in Load flow analysis.
This matrix helps in finding values of P, Q, |V| & δ.
With any type of changes in the network, the elements can be changed without actually changing the whole matrix in Y bus matrix.
We know that I= V/Z and Z= 1/Y.
Hence I=Y*V.
All these are matrices and hence the division by matrices is very hard we use multiplication using Y instead of dividing with Z.
Y is additive is parallel and we know that in power systems mostly loads are connected in parallel, that’s why power system calculation is done in admittance matrix form Y rather than Z because it helps to simplify calculations.
Ques 89. For n number of buses the power system size of Y, bus matrix is
(n-1)2
(n-2)2
n×n
None of the above
Answer.3. (n x n)
Explanation:
In power engineering, the nodal admittance matrix (or just admittance matrix) or Y Matrix or Ybus is the square matrix of an order of N x N matrix describing a power system with N buses.
Y matrix is symmetrical and there are many zeros in it. Hence it requires less memory as load flow analysis is done in computers.
Ques 90. Find the number of strands of ACSR conductor for 3 layer transmission line?
10
19
29
27
Answer.2. 19
Explanation:
The total number of strands in ACSR conductor is given as
N = 3x² – 3x + 1 where
x = number of layer
So the total number of strands
N = 3×3² – 3×3 + 1 = 19
