HVDC Transmission - Jos ArrillagaDescripción completa
hvdc
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some MULTIPLE CHOICE QUESTIONS
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great book for dc transmiision.
great book for dc transmiision.Descripción completa
hvdc
Descripción: Paper relacionado a las HVDC
1. The HVDC HVDC conve converte rterr Does not consume reactive power Consumes as much reactive power as real power p ower Consumes 50% of the real power+
2. A back to back back HVDC link can be advanta advantageous geous compar compared ed to AC primarily because It is cheaper Of stability considerations Of controlled power glow+
3. A 12pulse 12pulse bridge bridge is pre!erred pre!erred in HVDC because 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 termin terminal al DC link is removed removed by by !rea"ers on DC side !rea"ers on #C side Current control of converters+
% The capacitance and inductance per unit length o! a 3phase line& operating at 11' kV are .'1 micro!arad and 2.% mH. The surge impedance o! the line is 50 ohms 500 ohms+
$50 ohms
(. The )rst HVDC link in *ndia is bet$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. The magnitudes o! the sending end voltage Vs and o! the receiving end voltage Vr satis!y the !ollo$ing relationship )s *)r )s is greater than )r )s is less than )r+
- hunt compensation !or long /HV lines is primarily resorted to Improve voltage prole+ Improve stability educe fault currents 0 undled conductors are used in /HV lines primarily !or
educing cost of the line educing corona loss and radio interference+ Increasing stability limit
1'. /conomic studies have sho$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
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$er 4 communication lines can be minimi,ed by Increasing the spacing of power line conductors 'ransposing power line conductors 'ransposing communication line conductors
ither b or c+
1-. #ind the odd man out in vie$ o! HVDC transmission 9ood voltage regulation :ow e;ciency+ :esser corona loss
10. 5ulse number is given by the e6pression >*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 $rong in the assumption o! analysis o! converter circuit. 'he DC current is constant )alves are made as ideal switches
'he DC voltage is Buctuated one+ 'he #C voltages are sinusoidal and constant
22. The e6tinction angle is other$ise called as Delay angle argin angle+ Commutation angle iring angle
23. The harmonics contained in the current $ave!orm is given by Enp+.F Enp&.F EnpG.F+
2". hen the overlap angle is less than (' deg& it is called 'hree and four valve conduction mode 'wo and three valve conduction mode+ 'hree valve conduction mode
2%. hich o! the !ollo$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+
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$er !actor. ii< 9akes the distortion !actor =*1 >*
20. 9ain possibilities o! communication link o! the HVDC transmission Short wave radio lin" >ilot wires 'he use of carrier fre@uency on the power conductors #ll the above+
3'. The control o! po$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+
32. 7easons $hy the current control is desirable in the 7ecti)er station under normal operating conditions i<.The increase o! po$er in the link is achieved by reducing r $hich improves the po$er !actor at the recti)er. ii<. The current during line !ault are automatically limited $ith recti)er station in current control. I II
!oth I4II+
33. Ho$ po$er is reversed in HVDC link eversal of DC voltage+ Increase of DC voltage Decrease of DC voltage
3". Dra$ backs o! constant current control=CCC<. Increase in the converter valve voltage Increase in the magnitude of #C harmonics Decrease in the magnitude of #C harmonics !oth I4II+
3%. hat are the parameters to change current and po$er trans!er in DC link *< Control angle o! recti!ier **< Control angle o! inverter B ***< Tap changer on recti)er side I alone I3II4III+ II4III
3(. Converter valves should be operated strictly $ithin their Current rating+
)oltage rating !oth voltage and current rating
3+. The onload tap changer control at the inverter is used mainly to maintain Constant Dc voltage+ Constant #c voltage Constant current Constant voltage
3-. The tap changer control at the recti)er is designed to maintain Delay angle+ Current )oltage iring angle
30. hat is the use o! tap changing trans!ormer in HVDC systems Increase >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
"'. 9ention the per!ormance criteria !or selection o! harmonic )lter /armonic distortion 'elephone inBuence factor
"1. ill e?ects o! harmonics inected into the AC line 1tra power looses 4 conse@uent heating in machines+ /armonics Distortion
"2. 7adio inter!erence is mainly due to the >ositive conductor+
"3. hat are the sources o! harmonics #rcing devices and lectronic and medical test e@uipment+ >hase controllers and #C regulators #ll of the above
"". 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
"+. hat are the !actors depend on commutation !ailure i< The response o! the gamma controller at the inverter ii< The current control in the link iii< The magnitude o! AC voltage i alone i3 ii 4iii+ ii 4 iii
"-. 9ention the criteria !or selection o! DC )lter. a1imum voltage 'I on DC high voltage bus+ inimum voltage 'I on DC high voltage bus a1imum voltage 'I on #C high voltage bus inimum voltage 'I on #C high voltage bus
"0. A synthetic breadboard $hich electronically simulates the physical terminal characteristics o! each net$ork element rather than its mathematical input>output is >arity simulator+ >hysical simulator #nalog computer Digital computer
%'. 5ractical dielectrics used in HVDC cables. >aper Impregnated paper and polythene+ Castor oil >lastic