Description : The voltage of a particular bus can be controlled by controlling the a) Active power of the bus b) Reactive power of the bus c) Phase angle d) All of the above
Last Answer : b) Reactive power of the bus
Description : In load flow studies of a power system, a voltage control bus is specified by a) Real power and reactive power b) Reactive power and voltage magnitude c) Voltage and voltage phase angle d) Real power and voltage magnitude
Last Answer : d) Real power and voltage magnitude
Description : A 10-bus power system consists of four generator buses indexed as G1, G2, G3, G4 and six load buses indexed as L2, L2, L3, L4, L5, L6. The generator-bus G1 is connected ... of non linear equations required for solving the load flow problem using Newton-Raphson method in popular form is________.
Last Answer : 14
Description : In a load flow analysis of a power system, the load connected at a bus is represented as a) Constant current drawn from the bus b) Constant impedance connected at the bus c) Voltage and frequency dependent sources at the boss d) Constant real and reactive power drawn from the bus
Last Answer : d) Constant real and reactive power drawn from the bus
Description : Define voltage-controlled bus and load bus.
Last Answer : LOAD BUS A bus is called PQ bus or 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 permissible limits ... constant using automatic voltage regulator, we can specify constant PGi and | Vi | for these buses.
Description : When will the generator bus is treated as load bus.
Last Answer : If the reactive power of a generator bus violates the specified limits then the generator bus is treated as load bus.
Description : If a voltage-controlled bus is treated as load bus, then which one of the following limits would be violated? (a) Active power (b) Reactive power (c) Voltage (d) Phase angle
Last Answer : If a voltage-controlled bus is treated as load bus, then which one of the following limits would be violated? (a) Active power (b) Reactive power (c) Voltage (d) Phase angle
Description : In a load flow problem solved by newton-Raphson method with polar coordinates, the size of the Jactobian is 100 × 100. If there are 20 PV buses in addition to PQ buses and a slack bus, the total number of buses in the system is_____
Last Answer : 61
Description : A 4 bus power system consists of 4 transmission lines, then find the sparsity of Y bus matrix? a) 0.75 b) 0.25 c) 0.4 d) 0.5
Last Answer : b) 0.25
Description : What technique is used to solve load flow problems using Z-bus (Bus impedance matrix)?
Last Answer : The formulation of load flow problem using Zbus employs Diakoptics techniques which is actually the piecewise solution of the power system problem by using tearing off technique.
Description : Specified quantities of load bus are a) P and Q b) V and δ c) P and δ d) Q and V
Last Answer : a) P and Q
Description : Which of the following matrix is used for load flow studies? a) null matrix b) Unit matrix c) Z bus matrix d) Y bus matrix
Last Answer : d) Y bus matrix
Description : For load flow studies, what are the quantities specified at load bus are. a) P and V b) P and Q c) V and δ d) δ and Q
Last Answer : b) P and Q
Description : Mention the various types of buses in power system with specified quantities for each bus.
Last Answer : • Load bus or PQ-bus (P and Q are specified- Voltage magnitude and angle are to be obtained) • Generator bus or voltage controlled bus or PV bus (P and V are specified- Voltage angle and Q are to be obtained)
Description : A 1000 × 1000 bus admittance matrix for an electric power system has 8000 non-zero elements. The minimum number of branches (transmission lines and transformers) in this system are _____ (up to 2 decimal places)
Last Answer : Ans: 3500.00
Description : For n bus power system size of Y bus matrix is a) n*n b) (n-1)*(n-1) c) (n-1)*(n-2) d) (n-2)*(n-2)
Last Answer : a) n*n
Description : What is the need for slack bus in power flow analysis.
Last Answer : The slack/swing bus is needed to account for transmission line losses. In a power system the total power generated will be equal to sum of power consumed by loads and losses. In a power ... power are not specified for slack bus. They are estimated through the solution of load flow equations.
Description : The voltage control in electric supply networks in required on account of which of the following reasons ? (a) Adjustment of voltage at consumers premises within statutory limits (b) Control of ... daily and seasonal voltage variations in accordance with variations of load (d) All of the above
Last Answer : (d) All of the above
Description : What are the four quantities that are associated with each bus in a system?
Last Answer : • Real Power • Reactive Power • Voltage magnitude • Phase angle of voltage
Description : What will be the reactive power and bus voltage whan the generator bus is treated as load bus.
Last Answer : When the generator bus is treated as load bus, the reactive power of the bus is equated to the limit it has violated, and the previous iteration value of bus voltage is used for calculating current iteration value.
Description : A power system has 100 buses including 10 generator buses. For the load flow analysis using Newton-Raphson method in polar coordinates, the size of the Jacobian is a) 189x189 b) 100x100 c) 90x90 d) 180x180
Last Answer : a) 189x189
Description : In power system, the maximum number of buses are a) Generator buses b) Load buses c) Slack buses d) P-V buses
Last Answer : b) Load buses
Description : In a 4 bus,4×4 Y bus matrix the number of non zero elements are 12. Find the number of transmission lines? a) 8 b) 4 c) 2 d) 5
Last Answer : b) 4
Description : Which of the following quantities are to be calculated for generator bus a) P and V b) V and δ c) δ and Q d) Q and P
Last Answer : c) δ and Q
Description : The value of off diagonal elements is a) sum of admittances connected at bus j b) which is connected between bus i and bus j with positive sign c) which is connected between bus i and bus j with negative sign d) sum of admittances connected at bus i
Last Answer : c) which is connected between bus i and bus j with negative sign
Description : If sparsity of a 5 bus transmission line is 0.4. Find the number of transmission lines? a) 6 b) 5 c) 4 d) 3
Last Answer : b) 5
Description : um of the elements of row i equal to shunt admittances connected to bus i. If this summation is zero, indicates there is no a) shunt admittance b) mutual coupling c) both 1 and 2 d) none of the above
Last Answer : c) both 1 and 2
Description : Normally Z bus matrix is a a) null matrix b) sparse matrix c) full matrix d) unit matrix
Last Answer : full matrix
Description : Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]. Assertion: Fast decoupled load flow method gives approximate load flow solution because it uses several assumptions. Reason: Accuracy ... the correct reason for [a]. c) [a] is false and [r] is true.
Last Answer : c) [a] is false and [r] is true
Description : or accurate load flow calculations on large power systems, the best method is a) N-R method b) G-S method c) Decoupled method d) all of the above
Last Answer : a) N-R method
Description : Discuss the effect of acceleration factor in the load flow solution algorithm.
Last Answer : An acceleration factor is a value that can be used to speed up the convergence and reduce the number of required alteration in a Gauss Seidel method of power flow analysis .Very high or very ... trial and error load flow analysis. A generally recommended value of the acceleration factor is 1.6.
Description : What is the need for load flow analysis.
Last Answer : 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. It is also essential for designing a new power system.
Description : What is the information that are obtained from a load flow study.
Last Answer : • The 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 behavior of the system is to be studied.
Description : Explain Flat Voltage start.
Last Answer : In iterative methods of load flow solution, the initial voltages of all buses except slack bus are assumed as 1+j0 p.u. This is referred to as flat voltage start.
Description : A network containing 50 buses in which 10 are the voltage control buses, 6 are the generator buses. Find the size of the Jacobian matrix. a) 84*84 b) 83*83 c) 34*34 d) 33*33
Last Answer : b) 83*83
Description : Advantage of Gauss-Seidel method is a) applicable for large power system network b) calculation time for each iteration is less c) number of iterations are less d) all of the above
Last Answer : b) calculation time for each iteration is less
Description : What are the advantages of FDLF method.
Last Answer : FDLF method is faster, simple to program, more reliable and requires less memory than NR load flow method. FDLF method requires more iteration than N-R method, but requires less time per iteration.
Description : What is jacobian matrix?
Last Answer : The Jacobian matrix gives the linearized relationship between small changes in voltage angle or voltage magnitude with a small changes in real and reactive power.
Description : What are the disadvantages of NR method.
Last Answer : • The programming is more complex. • The memory requirement is more. • Computational time per iteration is higher due to large number of calculations per iteration.
Description : Mention any three advantages of N-R method over G-S method.
Last Answer : • The N-R method has quadratic convergence characteristic and so convergence faster than G-S method. • The number of iterations for convergence is independent of the size of the system in N-R method. • In N-R method the convergence is not affected by the choice of slack bus.
Description : Draw the circuit diagram for:- i) Measurement of active power in 3-phase load circuit using two wattmeter. ii) Measurement of reactive power in 3-phase load circuit using one wattmeter.
Last Answer : (i) Measurement of active power in 3- phase load circuit using two- wattmeter: (ii) Measurement of reactive power in 3- phase load circuit using one wattmeter
Description : The division of the reactive KVA load between paralleled AC generators is initiated by the ______________. A. prime mover governors B. voltage regulators C. phase balance relay D. proportioner
Last Answer : Answer: B
Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay
Description : For a 15-bus power system with 3 voltage controlled buses, the size of Jacobian matrix is
Last Answer : For a 15-bus power system with 3 voltage controlled buses, the size of Jacobian matrix is 25 x 25
Description : In wound rotor alternator, reactive power is maximum at a load angle of
Last Answer : In wound rotor alternator, reactive power is maximum at a load angle of 0o
Description : A single phase, half-wave, controlled rectifier has 400 sin (314 t) as the input voltage and R as the load. For a firing angle of 60° for the SCR, the average output voltage is (a) 240/π (b) 400/π (c) 300/π (d) 200/π
Last Answer : C
Description : In voltage source converter based HVDC transmission system the active power is controlled by changing (A) phase angle of the converter ac input voltage (B) supply frequency of the converter ac input voltage (C) magnitude of the converter ac input voltage (D) DC voltage at the inverter terminals
Last Answer : In voltage source converter based HVDC transmission system the active power is controlled by changing phase angle of the converter ac input voltage
Description : The voltage phasor of a circuit is 10 ∠15° V and the current phasor is 2∠–45° A. The active and reactive powers in the circuit are (a) 20 2 W and 10 2 VAR (b) 10 W and 10 3 VAR (c) 5 W and 5 3 VAR (d) 10 3 W and – 10 VAR
Last Answer : Angle between voltage and current ¢=15-(-45)=60° Cos60°=1/2 Active power =vicos¢=10×2×1/2=10watt Reactive power=visin¢=10×2×sin60°=20×√3/2=10√3
Description : When the generator buses are treated as load bus.
Last Answer : If the reactive power constraints of a generator bus violates the specified limits then the generator is treated as load bus.
Description : In load flow Study, a PV bus is treated as a PQ bus when
Last Answer : Voltage at the bus becomes high