What is the definition of extra low voltage?

What is the definition of extra low voltage?
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1 Answer

Answer :

Extra-low voltage (ELV) is an electricity supply voltage in a range which carries a low risk of dangerous electrical shock.

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Last Answer : Step-down transformer converts high voltage and low current into: Low voltage and high current

Which of the following is the least expensive protection for over current in low voltage system?

Description : Which of the following is the least expensive protection for over current in low voltage system?  (A) Rewireable fuse (B) Isolator (C) Oil Circuit breaker (D) Air break circuit breaker

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What is meant by extra high voltage transmission?

Description : What is meant by extra high voltage transmission?

Last Answer : HT & LT  two types transmission in industrial line 

Why does surge impedance loading (SIL) increase with increase in voltage level?

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Last Answer : Answer: SIL varies as the square of the operating voltage, so SIL increases with increase in voltage level

Electro-mechanical voltage regulators are generally used in (a) reactors (b) generators (c) transformers (d) all of the above

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When an alternator connected to the bus-bar is shut down the bus-bar voltage will (a) fall (b) rise (c) remain unchanged (d) none of the above

Description : When an alternator connected to the bus-bar is shut down the bus-bar voltage will (a) fall (b) rise (c) remain unchanged (d) none of the above

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The frequency of voltage generated, in case of generators, can be increased by (a) using reactors (b) increasing the load (c) adjusting the governor (d) reducing the terminal voltage (e) none of the above

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When the interconnector between two stations has large reactance (a) the transfer of power will take place with voltage fluctuation and noise (b) the transfer of power will take place with least loss (c) the stations will fall out of step be¬cause of large angular displacement between the stations (d) none of the above

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Last Answer : (c) the stations will fall out of step be¬cause of large angular displacement between the stations

For transmission of power over a distance of 500 km, the transmission voltage should be in the range (a) 150 to 220 kV (b) 100 to 120 kV (c) 60 to 100 kV (d) 20 to 50 kV

Description : For transmission of power over a distance of 500 km, the transmission voltage should be in the range (a) 150 to 220 kV (b) 100 to 120 kV (c) 60 to 100 kV (d) 20 to 50 kV

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Constant voltage transmission entails the following disadvantage (a) large conductor area is required for same power transmission (b) short-circuit current of the system is increased (c) either of the above (d) none of the above

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In a tap changing transformer, the tappings are provided on (a) primary winding (b) secondary winding (c) high voltage winding (d) any of the above

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Which of the following equipment, for regulating the voltage in distribution feeder, will be most economical ? (a) Static condenser (b) Synchronous condenser (c) Tap changing transformer (d) Booster transformer

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For transmission of power over a distance of 200 km, the transmission voltage should be (a) 132 kV (b) 66 kV (c) 33 kV (d) 11 kV

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The voltage drop, for constant voltage transmission is compensated by installing (a) inductors (b) capacitors (c) synchronous motors (d) all of above (e) none of the above

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Transmission voltage of ll kV is normally used for distances upto (a) 20—25 km (b) 40—50 km (c) 60—70 km (d) 80—100 km

Description : Transmission voltage of ll kV is normally used for distances upto (a) 20—25 km (b) 40—50 km (c) 60—70 km (d) 80—100 km

Last Answer : (a) 20—25 km

The power transmitted will be maximum when (a) corona losses are minimum (b) reactance is high (c) sending end voltage is more (d) receiving end voltage is more

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Which of the following is usually not the generating voltage ? (a) 6.6 kV (b) 8.8 kV (c) 11 kV (d) 13.2 kV

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As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to earth uses only (a) 31.25 percent of copper (b) 33.3 percent of copper (c) 66.7 percent of copper (d) 125 percent of copper

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Last Answer : (a) 31.25 percent of copper

Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is (a) 25 percent (b) 50 percent (c) 75 percent (d) 100 percent

Description : Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is (a) 25 percent (b) 50 percent (c) 75 percent (d) 100 percent

Last Answer : (b) 50 percent

The material generally used for armour of high voltage cables is (a) aluminium (b) steel (c) brass (d) copper

Description : The material generally used for armour of high voltage cables is (a) aluminium (b) steel (c) brass (d) copper

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The material commonly used for insulation in high voltage cables is (a) lead (b) paper (c) rubber (d) none of the above

Description : The material commonly used for insulation in high voltage cables is (a) lead (b) paper (c) rubber (d) none of the above

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High voltage transmission lines use (a) suspension insulators (b) pin insulators (c) both (a) and (b) (d) none of the above

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Most of the high voltage transmission lines in India are (a) underground (b) overhead (c) either of the above (d) none of the above

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The voltage of the single phase supply to residential consumers is (a) 110 V (b) 210 V (c) 230 V (d) 400 V

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Which of the following is the demerit of a 'constant voltage transmission system' ? (a) Increase of short-circuit current of the system (b) Availability of steady voltage at all loads at the line terminals (c) Possibility of better protection for the line due to possible use of higher terminal reactants (d) Improvement of power factor at times of moderate and heavy loads (e) Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission

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The phenomenon qf rise in voltage at the receiving end of the open-circuited or lightly loaded line is called the (a) Seeback effect (b) Ferranti effect (c) Raman effect (d) none of the above

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Which of the following characteristics should the line supports for transmission lines possess ? (a) Low cost (b) High mechanical strength (c) Longer life (d) All of the above

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Explain some of the methods to improve the strength of transmission system?

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What are the factors that limit the maximum power transfer capability in a transmission line?

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What are the problems associated with EHV transmission?

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What is the material used for overhead transmission lines?

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What for series and shunt compensation provided in EHV transmission lines?

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Series capacitors on transmission lines are of little use when the load VAR requirement is (a) large (b) small (b) fluctuating (d) any of the above

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The angular displacement between two interconnected stations is mainly due to (a) armature reactance of both alternators (b) reactance of the interconnector (c) synchronous reactance of both the alternators (d) all of the above

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In the analysis of which of the following lines shunt capacitance is neglected ? (a) Short transmission lines (b) Medium transmission lines (c) Long transmission lines (d) Medium as well as long transmission lines

Description : In the analysis of which of the following lines shunt capacitance is neglected ? (a) Short transmission lines (b) Medium transmission lines (c) Long transmission lines (d) Medium as well as long transmission lines

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The effect of corona can be detected by (a) presence of ozone detected by odour (b) hissing sound (c) faint luminous glow of bluish colour (d) all of the above

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For aluminium, as compared to copper, all the following factors have higher values except (a) specific volume (6) electrical conductivity (c) co-efficient of linear expansion (d) resistance per unit length for same cross-section

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Aluminium has a specific gravity of (a) 1.5 (b) 2.7 (c) 4.2 (d) 7.8

Description : Aluminium has a specific gravity of (a) 1.5 (b) 2.7 (c) 4.2 (d) 7.8

Last Answer : (b) 2.7

Pin type insulators are generally not used for voltages beyond (a) 1 kV (b) 11 kV (c) 22 kV (d) 33 kV

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The current drawn by the line due to corona losses is (a) non-sinusoidal (b) sinusoidal (c) triangular (d) square

Description : The current drawn by the line due to corona losses is (a) non-sinusoidal (b) sinusoidal (c) triangular (d) square

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The use of strain type insulators is made where the conductors are (a) dead ended (b) at intermediate anchor towers (c) any of the above (d) none of the above

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In a substation the following equipment is not installed (a) exciters (b) series capacitors (c) shunt reactors (d) voltatre transformers

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In aluminium conductors, steel core is provided to (a) compensate for skin effect (b) neutralise proximity effect (c) reduce line inductance (d) increase the tensile strength

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By which of the following methods string efficiency can be improved ? (a) Using a guard ring (b) Grading the insulator (c) Using long cross arm (d) Any of the above (e) None of the above

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Owing to skin effect (a) current flows through the half cross-section of the conductor (b) portion of the conductor near the surface carries more current and core of the conductor carries less current (c) portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent (d) any of the above (e) none of the above

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Last Answer : (b) portion of the conductor near the surface carries more current and core of the conductor carries less current

Which of the following bus-bar schemes has the lowest cost ? (a) Ring bus-bar scheme (b) Single bus-bar scheme (c) Breaker and a half scheme (d) Main and transfer scheme

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In AC.S.R. conductors, the insulation between aluminium and steel conductors is (a) insulin (b) bitumen (c) varnish (d) no insulation is required

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A conductor, due to sag between two supports, takes the form of (a) semi-circle (b) triangle (c) ellipse (d) catenary

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