Power system MCQ

Q 1 . In Power station practice "spinning reverse" is 

(a) Reverse generating capacity that is in operation but not in service. 

(b) Reverse generating capacity that is connected to bus and ready to take a load✔️

(c) Reverse generating capacity that is available for service but not in operation .

(d) Capacity of the part of the plant that remain under maintanence .

Q 2. Which plant can never have 100%load factor?

(a) Nuclear Power plant .

(b) Hydroelectric plant

(c) Peak load plant ✔️

(d) Base load plant

Q 3. The function of steel wire in a ASCR conductor is 

(a) To take care of surge 

(b) To prevent corona 

(c) To reduce inductance and hence improve power factor 

(d) To provide additional mechanical strength.✔️

Q 4. Steepness of the traveling waves is attenuated by

(a) Resistance of the line ✔️

(b) Inductance of the lin 

(c) Capacitance of the line

(d) All of above 

Q 5. A 30km transmission line carrying power at 33kv is known as 

(a) Short transmission line ✔️

(b) Long transmission line 

(c) High power line

(d) Ultra High power line

Q 6. Ferranti effect on transmission line is a phenomenon which represents

(a) Rise in recieving end voltage on laging load

(b) Rise in recieving end voltage on loading load

(c) Load impedance equal to surge impedance 

(d) Rise in recieving end voltage on no load ✔️

MCQ- SwitchGears and Protection System👉

Q.1 The main function of a fuse is to 

(a) Protect the line .

(b) Open the circuit .

(c) Protect the appliance .

(d) Prevent excessive currents.✔️

Q.2 Arc in a circuit breaker is interrupted at 

(a) Zero current.✔️

(b) Maximum current .

(c) Minimum voltage 

(d) Maximum voltage 

Q. 3 Induction cup relay operates when there is changes in

(A) voltage.

(B) current.

(C) impedance.

(D) all of the above.✔️

 Q.4 The arcing contacts in a circuit breaker are generally made of

(A) lead tin alloy.

(B) copper tungsten alloy.✔️

(C) electrolytic copper.

(D) aluminium alloy.

Q.5  On which of the following routine tests are conducted ?

(a) Oil circuit breakers.

(b) Air blast circuit breakers.

(c) Minimum oil circuit breaker . 

(d) All of above ✔️

Q.6 SF6 Gas 

(a) Yellow in colour.

(b) Lighter then air.

(c) Nontoxic .✔️

(d) None of above.

Q.7  The operating time of fuse is nearly 

(a) 1 Second.

(b) .5 Second. 

(c) 0.002 Second.✔️

(d) 1.5 Second.

Q.8 Operating time of circuit breaker is 

(a) 0.02 Second.

(b) 0.2 Second.✔️

(c) 1 Second .

(d) 1.4 Second.

Q.9 The arcing contact in circuit breaker are made of 

(a) Copper tungsten alloy.✔️

(b) Electrolytic copper.

(c) Alluminium alloy.

(d)Porcelain 

Q. 10 Which of the  following medium is employed for extinction of arc in air circuit breaker?

(a) SF6

(b) Air✔️

(c) Oil

(d) water

Q.11 IDMT relays are used to protect the power transformer against 

(a) Overload .

(b) Internal short circuit .

(c) External short circuit .

(d) External  short circuit  and over load .✔️

Q.12 Which of  the folowing relay is used for the generator phase to phase winding protection 

(a) Mho relay .

(b) Distance realy.

(c) Voltage balance relay.

(d) Differential relay. ✔️

Q.13 Which of the following circuit breaker must be equiped for remote operation 

(a) Inverse time trip.

(b) Shunt trip.✔️

(c) Time delay trip.

(d) All of above .

Q.14 Fault diverter are basically 

(a) Relay.

(b) Fuse.

(c) Fast switch.✔️

(d) Circuit breaker .

Q.15 A thermal protection switch can protect against 

(a) Short circuit .

(b) Temperature .

(c) Over voltage .

(d) Over load.✔️

Q16 Art in a circuit breaker behaves as 

(a) An inductive reactance .

(b) A resistance increasein with voltage rise across the arc .

(c) A resistance decreasing  with voltage rise  across arc.✔️

(d) Inductive reactance .

  

Q.17 thermal circuit breaker has 

(a) Delay trip action.✔️

(b) Instantaneous trip action.

(c) Both of above .

(d) None of above .

Q.18 Realy can be designed to respond change in 

(a). Temperature 

(b) Voltage an current.

(c) Resistance  impedance reactance .

(c) All of above .

Q.19 Over load realy are  of 

(a) Induction  and electromagnetic type 

(b) Solid state type.

(c) Thermal type.

(d) all of above ✔️

Q.20 Which of following relay is used to detect and protect internal fault of a transformer.

(a) Differential  realy.

(b) Bucholoz  realy.✔️

(c) IDMT .

(c) Directional relay.

Q.21 Which of following relay is used for anti- motoring protection scheme 

(a) Reactance relay.

(b) Reverse relay.✔️

(c) Differential relay.

(d) Moh relay.

Q.22 Resistance switching is normally employed in 

(a) Bulk oil breakers.

(b) Minimum oil breaker.

(c) Air blast circuit breaker .✔️

(d) SF6 circuit breaker.

Q.23 In overload system the relay used for feeder protection is 

(a) Under voltage relay.

(b) IDMT realy.

(c)Thermal relay.

(d) Translay relay.✔️

Q.24. Magnetic circuit breaker has trip action is 

(a) Delayed.

(b) Instantaneous.✔️

(c) None of above.

(d) All of above.

Q.25 DC shunt relays are made of 

(a) Few turns of thin wire .

(b) Few turns of thick wire.

(c) Many turns of thin wire .✔️

(d) Many turns of thick wire .

Q.26  The relay Operating speed depends on

(a) The spring tension.

(b) The rate of flux built up.

(c) Armature core air gap

(d) All of above ✔️

Q.27 The arc voltage in a circuit breaker is

(a) in the phase with arc current..✔️

(b) lagging the arc current by 90°.

(c) leading the arc current by 90°.

(d) lagging the arc current by 180°. 

Q.28 What is the reactive power in AC operation?

(a) Real power × sinφ.

(b) Apparent power × sinφ.✔️

(c) Real power × cosφ.

(d) Apparent power × cosφ. 

Q.29 The purpose of using series capacitor in a transmission lines is to

(a) reduce inductance.

(b) reduce line losses.

(c) compensate voltage drop.✔️

(d) improve power factor. 

Q.30 Which of the following circuit breaker is design for the least operating voltage?

(a) Vacuum circuit breaker.

(b) Air circuit breaker.✔️

(c) SF6 circuit breaker.

(d) Oil circuit breaker. 

Q.31 The rating of a circuit breaker is usually determine on the basis of

(a) symmetrical fault.✔️

(b) unsymmetrical fault.

(c) line to line fault.

(d) internal fault.   

Q. 32 Circuit breakers are usualy operate under  

(a) Transient state of short circuit current.✔️

(b) Sub transient state of short circuit current .

(c) Steady state of short circuit current .

(d) All of above

Q.33  Circuit breaker are essentially 

(a) Current carring contact called electrod.✔️

(b) Arc extinguishers.

(c) circuit to break the system .

(c)All of above.

 

Q. 34 Air blast circuit breaker is used for 

(a) Over current .

(b) Short duty .

(c) Intermediate duty.

(d) Repeated duty.✔️

Q.35  Directional relay are based on folow of 

(a) Current.✔️

(b) Power.

(c) Voltage .

(d) All of above.

Q.36. A differential relay measures the vector difference between 

(a) Two current.

(b) Two Voltage .

(c) Two or more similar electrical quantities.✔️

(d) None of above 

Q. 37 A transmission line is protected by

(a) Inrush protection.

(b) Distance protection

(c)  Both a and b✔️

(d) None of above .

Q.38 Large internal fault are protected by

(a) Merz price percentage differential protection.✔️

(b) Mho relay

(c) Ohms relay

(d) none of above 

Q.39 Chimney effect occurs in 

(a) Sf6 circuit breaker .

(b) Vacuum circuit breaker .

(c) Oil circuit breaker. 

(d) Air blast circuit breaker .✔️

Q.40 The arc voltage in a ac circuit breaker is 

(a) in phase opposition with the arc current .

(b) In phase with arc current ✔️

(c) Lag arc current by 90°

(d) Lead arc current by 90°

Q.41 Electrical Switchgear is consider as low voltage Switchgear if it is rated upto

(a) 400 V.

(b) 1 kV.✔️

(c) 11 kV.

(d) 33kV. 

Q.42 Under normal condition, the voltage across a lighting arrestor is

(a) zero.

(b) very small.

(c) equal to phase voltage.

(d) equal to line voltage✔️

Q.43. Generally, the circuit breakers are rated  term of

(a) volt-ampere.

(b) current.

(c) voltage.✔️

(d) VAR. 

Q.44 Which device is used to protect the power system against traveling waves?

(a) capacitor.

(b) earth wire.

(c) surge diverter.✔️

(d) earthing screen.

Q.45 In the electric system, Resonance may result in

(a) zero voltage.

(b) high voltage.✔️

(c) low voltage.

(d) high current.   

Q.46 A device which is used to protect an electric circuit from damage caused by over load or short circuit is

(a) Wave trapper.

(b) CVT.

(c) circuit breaker.✔️

(d) lighting arrester.  

Q 47 Ionization in circuit breaker is facilitated by 

(a) High temperature .

(b) Increase of mean free path.

(c) Increasing field strength.

(d) all of above ✔️

Q.48  shunt capacitance is neglected while considering 

(a) Short transmission line .✔️

(b) Medium transmission line 

(c) Long transmission line 

(d) Long and midium transmission line .

Q.49  Insulation resistance of high voltage circuit breaker is more then 

(a) 10 mega ohms.

(b) 1 mega Ohms.

(c) 100 mega ohms .✔️

(d) 500 mega ohms.

Q.50 HRC fuse provide best protection against 

(a) Over load .

(b) Reverse current .

(c)  Open circuit. 

(d) Short circuit. ✔️

Metal halide (MH) lamps consist of an arc tube (also called a discharge tube or "burner") within an outer envelope, or bulb. The arc tube may be made of either quartz or ceramic and contains a starting gas (usually argon), mercury, and MH salts. Traditional quartz MH arc tubes are similar in shape to mercury vapor (MV) arc tubes, but they operate at higher temperatures and pressures.
MH lamps start when their ballast supplies a high starting voltage higher than those normally supplied to the lamp electrodes through a gas mixture in the arc tube. The gas in the MH arc tube must be ionized before current can flow and start the lamp. In addition to supplying the correct starting voltage, the ballast also regulates the lamp starting current and lamp operating current. (See "What types of ballasts are available to use with metal halide lamps?")
As pressure and temperature increase, the materials within the arc tube vaporize and emit light and ultraviolet (UV) radiation. A bulb (also called "outer jacket" or "outer envelope"), usually made of borosilicate glass, provides a stable thermal environment for the arc tube, contains an inert atmosphere that keeps the components of the arc tube from oxidizing at high temperatures, and reduces the amount of UV radiation that the lamp emits. Some MH lamps have a coated finish on the inside of the bulb that diffuses the light. Often a phosphor coat is used to both diffuse the light and change the lamp's color properties.

MOSFET working

The MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistor is a semiconductor device which is widely used for switching and amplifying electronic signals in the electronic devices.  The MOSFET is a core of integrated circuit and it can be designed and fabricated in a single chip because of these very small sizes.  The MOSFET is a four terminal device with source(S), gate (G), drain (D) and body (B) terminals. The body of the MOSFET is frequently connected to the source terminal so making it a three terminal device like field effect transistor. The MOSFET is very far the most common transistor and can be used in both analog and digital circuits.

The MOSFET works by electronically varying the width of a channel along which charge carriers flow (electrons or holes).  The charge carriers enter the channel at source and exit via the drain. The width of the channel is controlled by the voltage on an electrode is called gate which is located between source and drain. It is insulated from the channel near an extremely thin layer of metal oxide. The MOS capacity present in the device is the main part

Depletion Mode__

Enhancement Mode_

Depletion  Mode:

When there is no voltage on the gate, the channel shows its maximum conductance. As the voltage on the gate is either positive or negative,  the channel conductivity decreases.

Enhancement mode:-
When there is no voltage on the gate the device does not conduct. More is the voltage on the gate, the better the device can conduct.

MOSFET Operation

The working of a MOSFET depends upon the MOS capacitor. The MOS capacitor is the main part of MOSFET. The semiconductor surface at the below oxide layer which is located between source and drain terminals. It can be inverted from p-type to n-type by applying positive or negative gate voltages.

When we apply positive gate voltage the holes present under the oxide layer with a repulsive force and holes are pushed downward with the substrate. The depletion region populated by the bound negative charges which are associated with the acceptor atoms. The electrons reach channel is formed. The positive voltage also attracts electrons from the n+ source and drain regions into the channel. Now, if a voltage is applied between the drain and source, the current flows freely between the source and drain and the gate voltage controls the electrons in the channel. If we apply negative voltage, a hole channel will be formed under the oxide layer.

P-channel MMoSFET

The drain and source are heavily doped p+ region and the substrate is in n-type. The current flows due to the flow of positively charged holes also known as p-channel MOSFET. When we apply negative gate voltage, the electrons present beneath the oxide layer experience repulsive force and they are pushed downward in to the substrate, the depletion region is populated by the bound positive charges which are associated with the donor atoms. The negative gate voltage also attracts holes from p+ source and drain region into the channel region.

N-Channel MMosFET

The drain and source are heavily doped n+ region and the substrate is p-type. The current flows due to the flow of negatively charged electrons, also known as n-channel MOSFET. When we apply the positive gate voltage the holes present beneath the oxide layer experience repulsive force and the holes are pushed downwards in to the bound negative charges which are associated with the acceptor atoms. The positive gate voltage also attracts electrons from n+ source and drain region in to the channel thus an electron reach channel is formed.