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1. The HVDC converter
Does not consume reactive power
Consumes as much reactive power as real power
Consumes 50% of the real power+
2. A back to back HVDC link can be advantageous compared to
AC primarily because
It is cheaper
Of stability considerations
Of controlled power glow+
3. A 12pulse bridge is pre!erred in HVDC because
It eliminates certain harmonics+
It results in better power factor
Series connection of converters on DC side is better
". #ault on a t$o terminal DC link is removed by
!rea"ers on DC side
!rea"ers on #C side
Current control of converters+
% The capacitance and inductance per unit length o! a 3phaseline& operating at 11' kV are .'1 micro!arad and 2.% mH. The
surge impedance o! the line is
50 ohms
500 ohms+
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$50 ohms
(. The )rst HVDC link in *ndia is bet$een
ihand&Delhi+
!allia & !hiwadi
'alcher & (olar
!iswanath & #gra
+. A long transmission line is energi,ed at then sending end
and is kept open circuited at the receiving end. Themagnitudes o! the sending end voltage Vs and o! the receiving
end voltage Vr satis!y the !ollo$ing relationship
)s *)r
)s is greater than )r
)s is less than )r+
- hunt compensation !or long /HV lines is primarily resortedto
Improve voltage prole+
Improve stability
educe fault currents
0 undled conductors are used in /HV lines primarily !or
educing cost of the line
educing corona loss and radio interference+
Increasing stability limit
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1'. /conomic studies have sho$n that D.C. transmission is
cheaper than a. c transmission !or lengths
below ,00 "m
beyond -00 "m+
beyond .$00 "m
11. Transmission voltages in the range 23' kV+(% kV are
kno$n as
/igh voltage
1tra /igh )oltage+
2ltra /igh )oltage
12. hich one o! the !ollo$ing statements is !alse
As the transmission voltage increases&
Corona loss decreases
Conductor copper loss decreases
Cost of insulators3 transformers3 switches 4 circuit brea"ers
increases+
13. The !actors to be considered !or planning HVDC
transmission
Cost
'echnical performance
eliability
#ll of the above+
1". The surge impedance o! a doublecircuit po$er
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transmission line is
0 ohms
$00 ohms+
00 ohms
600 ohms
1%. The surge impedance o! a telephone line is
50 ohms
75 ohms+
$00 ohms
00 ohms
1(. undle conductors are pre!erred in /HV transmission lines
because
It is easy to fabricate thin conductors and combine them to ma"e a
bundle
Inductance of the line is reduced3 and the corona loss3 and radio 4 ')
interference is minimi8ed+
'ower height is reduced and hence transmission cost is low
1+. *nductive inter!erence bet$een po$er 4 communication
lines can be minimi,ed by
Increasing the spacing of power line conductors
'ransposing power line conductors
'ransposing communication line conductors
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ither b or c+
1-. #ind the odd man out in vie$ o! HVDC transmission
9ood voltage regulation
:ow e;ciency+
:esser corona loss
*r?@s
>*s?@r
>*@rs+
>*@r?s
2'. A 12 pulse converter is obtained by series connection o!
t$o bridges $ith
-0 deg phase displacement between two source voltages
,0 deg phase displacement between two source voltages+
.$0 deg phase displacement between two source voltages
A0 deg phase displacement between two source voltages
21. hich o! the !ollo$ing is $rong in the assumption o!analysis o! converter circuit.
'he DC current is constant
)alves are made as ideal switches
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'he DC voltage is Buctuated one+
'he #C voltages are sinusoidal and constant
22. The e6tinction angle is other$ise called as
Delay angle
argin angle+
Commutation angle
iring angle
23. The harmonics contained in the current $ave!orm is givenby
Enp+.F
Enp&.F
EnpG.F+
2". hen the overlap angle is less than (' deg& it is called
'hree and four valve conduction mode
'wo and three valve conduction mode+
'hree valve conduction mode
2%. hich o! the !ollo$ing is not the !eatures o! converter
control
Current order setting can be @uic"ly and reliably changed depending
on the re@uirement
>ower reversal can be done easily and @uic"ly
'he Stability margin is moderate+
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ault current levels are limited to rated values
2(. eries and parallel operation o! thyristor in HVDC
T7A89**:8 results in
or higher voltage and power rating
or higher voltage and current rating+
or higher current and power rating
2+. *n HVDC transmission system& recti)er )ring angle a is kept
near
0H
.5H
,00+
A00
2-. Consider the !ollo$ing statements;
A !ree $heeling diode across the load circuit o! a t$opulse
converter
i< *mproves the operating po$er !actor.
ii< 9akes the distortion !actor =*1 >*
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20. 9ain possibilities o! communication link o! the HVDC
transmission
Short wave radio lin"
>ilot wires
'he use of carrier fre@uency on the power conductors
#ll the above+
3'. The control o! po$er in a DC link can be achieved through
Control of voltage of current
Control of current
Control of current of voltage+
Control of voltage
31. The e6citation angle controller can be controlled by
>redictive type
eedbac" type
!oth i 4 ii+
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!oth I4II+
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)oltage rating
!oth voltage and current rating
ower factor obtained in ac side+
Decrease >ower factor obtained in dc side
increase >ower factor obtained in dc side
decrease power factor obtained in ac side
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"'. 9ention the per!ormance criteria !or selection o! harmonic
)lter
/armonic distortion
'elephone inBuence factor
ositive conductor+
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"". hat are the e?ects o! trouble caused by harmonics
/armonics
)oltage collapse
Over heating+
Decrease magnetic loss
"%. The inde6 THD can be calculated !or
Current
)oltage
Current and voltage
Current or voltage+
"(. hat are the means to reduce harmonics
2sing lter and increasing the pulse number+
Decreasing pulse number
2sing lter only
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output is
>arity simulator+
>hysical simulator
#nalog computer
Digital computer
%'. 5ractical dielectrics used in HVDC cables.
>aper
Impregnated paper and polythene+
Castor oil
>lastic