sysnchronous generator transient analysis2

8/8/2019 Sysnchronous Generator Transient Analysis2

1/12

SYSNCHRONOUS GENERATOR

TRANSIENT ANALYSIS

NAME: - M. S. NakandalaINDEX NO: - 080314MFIELD: - EEDATE OF PER: -25.10.2010DATE OF SUB: - 06.12.2010

OBSERVATION SHEET

NAME: - M. S. NakandalaINDEX NO: - 080314MFIELD: - EEDATE OF PER: - 25.10.2010INSTRUCTED BY: -


2/12

a) Obtaining of short circuit armature current oscillogram

Pre-short circuit line voltage = 35 VSteady short circuit current = 2.3 AGenerator speed = 1507 rpmNumber of generator pole pairs = 2

b) Obtaining of field current oscillogram

Steady state field current = 0.1A


3/12

d) Slip test

Minimum Phase current = 1.7AMaximum phase current = 1.85AMinimum line voltage = 20 VMaximum line voltage = 21 VGenerator speed = 1470 rpm


4/12

CALCULATION

a. Obtaining of short circuit armature current oscillogram

T(ms) Armature (A)

0 13.5

10 10.5

20 8.25

30 7.75

40 7

50 6.75


5/12

60 6.25

70 5.75

80 5.5

90 5.25

100 5110 4.75

120 4.5

130 4.25

140 4.25

150 4.25

160 4.25

170 4

180 4

190 4

200 4

210 4

220 4

230 3.75

240 3.5

250 3.75

260 3.75

270 3.75

280 3.63

290 3.63

300 3.5

310 3.5

320 3.5

330 3.5

340 3.5

350 3.5

From the Graph, From theory,

A = 12.69A

B =3.5A== 17.8/2 BVX

Sd


6/12

21.203/35 ==SV

== 252.2/2'' AVX Sd

T(ms) )(

0 9.13

5 8.178769

10 7.280297

15 6.427746

20 5.714704

25 4.995176

30 4.443571

35 3.83469340 3.423728

45 2.906233

50 2.618125

55 2.175670

60 1.995472

65 1.614460

70 1.529879

75 1.199277

80 1.200496

85 0.911657

90 0.991153

95 0.737635

100 0.89

105 0.667384


7/12

msT

msD

d 75.58'

75.58

=

=

=

=

263.2'

129.9

dX

C

Td''= 3.16 ms

The open circuit transient and sub transient time constants can also be obtained,

Tdo'= Td' XdXd'

Tdo'= 58.75 8.172.63 = 182.50 ms

Tdo''= Td'' Xd'Xd''

Tdo''= 3.16 2.2632.252 = 3.18 ms

T(ms) Armature (A)

0 27.510 21

20 16.5

30 15.5

40 14

50 13.5

60 13.5

T(ms) )( Y

0 6.711

5 5.825462

10 4.962770

15 4.136171

20 3.350680

25 2.605238

30 1.894530

35 1.210465

40 0.543320


8/12

70 11.5

80 11

90 10.5

100 10

110 9.5

120 9130 8.5

140 8.5

150 8.5

160 8.5

170 8

Ta = 7.1994 ms

Field current variation following a short circuit

+= te

T

Te

T

Te

X

XXIII Tat

d

kddTt

d

kddTt

d

ddfff cos

'')

''1(

'

)'( /''/'/00

Assume no dampers. ThereforeTkd = 0

If=0.1+ 0.1 8.17-2.2632.263[ e-t58.75 -1-0e-t3.16- 0]

If=0.1+ 0.261[ e-t58.75 -e-t3.16]

Time (ms) If0 0.110 0.30912720 0.28522830 0.25661040 0.23211450 0.21143760 0.193995


9/12

70 0.17928480 0.16687590 0.156408100 0.147580110 0.140132120 0.133851

130 0.128553140 0.124084150 0.120314160 0.117135170 0.114453180 0.112191190 0.110283200 0.110283

Armature voltage on sudden open circuit from a steady short circuit,

Va=2Vscost+0- 2VsXd-X'dX''de-tTdo cost+0-2VsXd-X''dXde-tT'do cost+0

Lets assume o = 0 and w = 314.16

Va=2Vscost- 2VsXd-X'dX''de-tTdo' cost-2VsX'd-X''dXde-tT''do cost

Va=28.58cos314.16t- 74.96 e-t182.5 cos314.16t+ 0.038 e-t3.18cos (314.16t)

Time (ms) Va (V)0 -46.34210 6.19121820 36.9518330 -14.90964240 -26.34220


10/12

50 19.01405160 16.17591170 -19.24569480 -7.66366190 16.657707100 1.542538

110 -12.435448120 1.922312130 7.732483140 -2.885151150 -3.536619160 1.829280170 0.575103180 0.546291190 0.736901200 -3.448195210 -0.305235

220 6.104372230 -1.672241240 -7.862695250 4.764766260 8.264291270 -8.388188280 -7.086703290 11.894220300 4.355570310 -14.659071320 -0.326669330 16.162164340 -4.557087350 -16.047549360 9.727125370 14.162948380 -14.561356390 -10.573992400 18.458777410 5.553778420 -20.908704430 0.449740440 21.547857450 -6.864051460 -20.200138470 13.054196480 16.895844490 -18.389985500 -11.869240


11/12

Slip test parameters

Xd= Va,pk-pkmaxIa,pk-pk min

Xd= 211.7*3 = 7.13

XQ= Va,pk-pkminIa,pk-pk max

XQ= 201.85*3 = 6.24


12/12

DISCUSSION

When comparing Xd value obtained from the slip test and the short circuit armaturecurrent oscillogram there is a huge difference between them.

When we compare the theoretical and practical graph of the variation of field current atshort circuit test, it seems both are having same shape. But the practical curve takes more time toacquire the steady state, compare with theoretical curve. This may occur due to the effect ofdamping effect in real situation. Also theoretical oscillograms are very smooth. But in practicalcase they are not like that, because they have been affected to noise introduced by the externaldevices.

In short circuit oscillogram there are 4 components in the transient behavior. Transient component Sub transient component DC offset component Steady state component

Transient and sub transient components rapidly vary with the time, but transient componenttakes much time to decay than sub transient component. Generally sub transient period lasts for3-4 cycles of current. However transient period is long and lasts for some hundreds of cycles.DC offset current is caused due to the armature reaction.

It is important to know whether the generator can withstand against transient behaviors and itis having correct damping. The parameters we calculated by using the observations of short

circuit study are important when designing protection schemes to the synchronous generator.Therefore short circuit study is very important.

sysnchronous generator transient analysis2

Documents