ReviewQuestion
UNIT_ I
PartA (2 Marks)
Whatis the needfor systemanalysisin planningandoperation
of powersystem?
Whatis one linediagram?
Defineperunitquantity.
procedures
Whatare the step-by-step
to be followedto findthe pu impedance
diagramof a power
system?
partsin the powersystemnetwork.
Drawthe singlelinediagramshowingthe essential
Whatarethe advantages
of pu representation?
A transmission
linehasan impedance
of 0.02+ j 0.08p-u.to a baseof 1 MVA,11 kV.Whatwillbe
the corresponding
Valuesto a baseof 2MVA,22kV?
Whatconditionon baseandratedvoltagesshouldbe satisfied
to giveequalpu impedances
viewed
?
fromeithersideof a two-windino
transformer
PartB (16Marks)
is 0.25pu on its ratings.lt is connected
9. (i). The subtransient
reactance
of a 500 MVA,18 kV generator
Find
out
the subtransient
reactanceof the
to a networkthrougha 20 I 400 kV transformer.
generator
on a baseof 1OOMVAand20 kV. (4)
(ii). A transformer
interconnects
a strong400 kV and a weaker200 kV systemand is providedwitha
tap changeron the 400 kV side.What is the effectof settingthe tapsuchthat the voltageratiois
410I 200kV on the400and220 kV sides? (4)
(iii). Draw the pu reactancediagramof a three-winding
transformer
whosethree-phase
ratingsare.
primary(P), wye-grounded,
15 MVA, 66 kV; secondary(S), wye-grounded,
10 MVA, 13.2 kV;
valuesof the impedances.
The
tertiary(t), deltaconnected,
5 MVA,2.3 kV. Markthe appropriate
measureddatafor impeances
ate Zps= 7 o/oon 15 MVAand66 kV; Zpr = 9 % on 15 MVAand 66
Zst = 8 o/oon 10 MVAon 13.2kV. (8)
(iv).Sketchand explainelectricpowersystemand marf(hevoltagelevelat variouspointsfromgenerator
to load.(8)
10.
is shownin Fig.13 is as follows.
Thedatafor the systemwhosesingleJine-diagram
G1: 30 MVA,10.5kV,X" = 1.6 a; G2: 15 MVA,6.6kV,X" = 1.2cl
G3:25 MVA,6.6 kV,X" = 0.56O
T1: 15 MVA,33/11kV,X=15.2o on h t side
T2: 15 MVA,33/6.2kV,X=16.0O on h.tside
Transmission
Line:X=20.5frphase
Loads:A: 40 MW,0.9 p.flag,11 kV; B: 40 MW,0.85p.flag,6.6kV
basevoltagesfor differentparts.Draw the
Choosethe basepoweras 30MVAand approximate
( 16 )
reactancediagram.lndicatep.u.reactanceson the diagram.
G1
G2
G3
11
Fig.14 showsa single-line
diagramof a powersystem.The ratingsof generators
andtransformers
are:
j0.2
pu
Generator
G1:25 MVA,6.6 kV,
j0.15
pu
Generator
G2:15MVA,6.6kV,
Generator
Gg:30 MVA,13.2kV,j0.15pu
Transformer
T1:30 MVA,6.6A - 115Y kV,j0.'1pu
Transformer
T2:15 MVA,6.6A - 115 Y kV,j0.1 pu
Transformer
T3:Singlephaseunitseachrated1OMVA,
69/6.9kV,j0.1 pu.
Drawimpedance
diagramwithall valuesin pu on a baseof 30 MVA,6.6 kV in the circuitof generator
G1.
a
a a
a
Fig.l4
(16)
12 Fig.15 showsa generatorfeedingtwo motorsthroughtransformers
and line.The ratingsand reactances
areas under.
G: 100MVA,11kV,3 phase,x= 20%
T1: 100MVA.111132kV.
x=So/o
T2. Bankof 3 single-phase
eachratedat 35 MVA,66111kV,
transformers,
x=4%.
M1:40
MVA,3phase,
10kV,
x=20%
.M2:60 MVA,3phase,'l 1 kV,x=15%
The linereactance
is 80 ohms.
Selectsuitablebasevalues.Drawthe reactance
diagram.Indicatep.u.reactances
on the diagram.
M1
b_
M2
b_
13.
Fig.15
Thedatafor the systemwhosesinglejine-diagram
is shownin Fig.16is as follows:
T1:5 MVA,13.2N132Y kV,X=10%
T1: 10 MVA,138Y/69A kV,X=8%
Transmission
Line:Zr='10+ j100Cyphase
=
:
21o"6
Load,
300 Oiphase
Choosethe base power as 10 MVA and approximatebase voltagesfor differentparts. Draw the
impedancediagramwith valuesof per unit impedances
of variouscomponents
clearlymarked.Also
findthe generator
current,thetransmission-line
current,the loadcurrentandthe loadvolr2ria/14\
2
i
MA-Li#-l-,
7p
\_-/l
1 3 . 2k v
'
Tr
7p
Tz
lz,ouo
14
Discussin detailthe variousstudiescarriedout in the powersystemplanning(16)
15.
Discussaboutthe modernpowersystemin detail.
16
The parametersof a 4-bussystemare as under:
L i n e Linestarting L i n ee n d i n g
n o . bus
bus
1
1
2
2
3
4
5
1.
2
?
v ,
2
2
3
4
4
1
3
3
(pu) Charging
Lineimpedance
admittance(pu)
0 . 2+ j 0 8
i0 02
j0 03
0.3+j09
+
j0 04
0.25 j1.0
+
j
j0 02
0.2 0 8
+
01 J0.4
J0.01