## electrical

### Switchgear and Protection MCQ Objective Questions and Answers Page - 9

1.
 The use of high speed circuit breakers A Reduces the short circuit current B Improves the system stability C Decreases the system stability D Increase short circuit current Answer : B Explanation :
2.
 Transient state stability is generally improved by A Using high speed governors on machines B Using low inertia machines C Dispensing with neutral grounding D Any of the above Answer : A Explanation :
3.
 Load flow study is carried out for A Load-frequency control B Planning of power system C Fault calculations D Study of stability of the system Answer : B Explanation :
4.
 Load flow studies must be made on a power system before A Making short-circuit studies but not for transient stability studies on the power system. B Making transient stability studies but not for short-circuit studies on the power system. C Making both short-circuit  and  transient stability studies on the power system. D For neither Making short-circuit studies nor transient stability studies on the power system. Answer : C Explanation :
5.
 Load flow studies involve solving simultaneous A Linear algebraic equations B Non-Linear algebraic equations C Linear differential equations D Non-Linear differential equations Answer : B Explanation :
6.
 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 Answer : D Explanation :
7.
 For a load-flow solution the quantities normally specified at a voltage controlled bus are A P  and  Q B P  and  |V| C Q  and  |V| D P  and  $\delta$ Answer : B Explanation :
8.
 At slacks bus, which one of the following combinations of variables is specified  ? A |V|, $\delta$ B P, Q C P, |V| D Q, |V| Answer : A Explanation :
9.
 In a power system, the maximum number of buses are A Generator buses B Load buses C Slack buses D P-V buses Answer : B Explanation :
10.
 If a voltage controlled bus  is treated as a load bus, then which one of the following limits would be violated  ? A Voltage B Active power C Reactive power D Phase angle Answer : A Explanation :
11.
 In load-flow analysis, 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 source at the bus. D Constant real and reactive power drawn from the bus. Answer : D Explanation :
12.
 The voltage of a particular bus can be controlled by controlling A Phase angle B Reactive power of the bus C Active power of the bus D Phase angle and reactive power Answer : B Explanation :
13.
 Gauss-Seidel interactive method can be used for solving a set of A Linear differential equations only B Linear algebraic equations only C Both Linear and nonlinear algebraic equations D Both Linear and nonlinear differential equations Answer : B Explanation :
14.
 Fault calculation using computer program are usually done by A $Y_{BUS}$  method B $Z_{BUS}$   method C Both of the above D None of the above Answer : A Explanation :
15.
 The Gauss Siedel load flow method has following disadvantages. Tick the incorrect statement A Unreliable convergence B Slow convergence C Choice of slack bus affects convergence D A good initial guess for voltages is essential for convergence Answer : A Explanation :
16.
 In Gauss-Seidal load flow method, the number of iterations may be reduced if the correction in voltage at each bus is multiplied by A Gauss constant B Acceleration factor C Blocking factor D Lagrange multiplier Answer : B Explanation :
17.
 Compared to Gauss Siedel method, Newton-Raphson method takes A Less number of iterations  and  more time per iterations . B Less number of iterations  and  less time per iterations . C More number of iterations  and  more time per iterations . D More number of iterations  and  less time per iterations . Answer : A Explanation :
18.
 Regulating transformers are used in power system for control of A Voltage B Power factor C Power flow D All of the above Answer : C Explanation :
19.
 In a load-flow study a PV bus is treated as a  PQ  bus when A Voltage limit is violated B Active power limit is violated C Phase angle is high D Reactive power limit is violated Answer : D Explanation :
20.
 If the reference bus is changed in two load flow buses with same system data and power obtained for reference bus taken as specified  P  and  Q  in the latter run A The system losses will be unchanged but complex bus voltages will change. B The system losses will change but complex bus voltages remain unchanged. C The system losses as well as complex bus voltages will change. D The system losses as well as complex bus voltages will be unchanged Answer : A Explanation :