trafo merkezi topraklama hesabı

TOPRAKLAMA HESABI :

600 X 600

Soil resistivity has been considered average of values of

attached document to letter No. dated December 6 , 2004 of EES

Primary data related to earthing design :

PLEASE REFER TO ATTACHED DRAWING.

SHORT CIRCUIT CURRENT : KA50

PHASE S.C CURRENT : 1

SOIL RESISTIVITY :

SURFACE LAYER RESISTIVITY (GRAVEL) : 3000

BURIAL DEPTH OF EARTHING GRID :

EARTHING CALCULATION FOR

RUDESHUR 400 KV POWER PLANT S/S

RATED SYMMETRICAL THREE PHASE

Ohm-Meter

m

m

SURFACE LAYER THICKNESS : 0.1

AREA OCCUPIED BY EARTHING GRID :

m

80

0.7

m2

TIME DURATION OF GROUND FAULT : Sec.0.5

MAXIMUM TEMPERATURE OF AMBIENT : oC50

K RATIO OF SINGLE PHASE TO THREE

DATEAPPR2APPR1CHECKPREPREV

SHEET / CONT

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REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:

RUDESHUR SIMPLE CYCLE POWER

PLANT

AND 400kV SUBSTATION

EARTHING SYSTEM CALCULATION

UNIT INTERNATIONAL S.A

ISLAMIC REPUBLIC OF IRAN

MAH-TAAB GOSTAR CO.

DWG NO: 7102-RSH-E-CN-4-01 1 002 REV: G

SIEMENSPOWER GENERATION

CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F

12.07.05A SF GHA GDM SHG

m

50

=

3Nrod = No. of required rod = 100 Lr = the length of each rod in m =

LR = Nrod X LrLT = LC + 1.15LR

Lc = NX*X + NY*Y = 13 X

600A = X*Y = 600 X

=

13

15600 m total length of burial mesh.

Spacing between parallel conductor.

N0. of Horizontal burial conductors.

N0. of Vertical burial conductors.1 =

13

The area occupied by burial grid.

600

360000 m2

+ 13 X

13.0

13.0

The estimated distance for

600

50

600

+

+

1 =

1- EARTH RESISTANCE CALCULATION : RGRID

The estimated distance between earth wires is 50 meter.

D = 50

600

50

m has been resulted by trial & error method.

=300 15945 m

[Eq.52 IEEE-Std 80-2000]0.064

300

h : Depth of earthing conductor burial

15600 +LT =

LR = total length of all rod in m =

1D

YN X

1D

XNY

)20/Ah1

1(1

20A

1

TL

1

gR


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REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


=

1.0

X 1.0 = kA

+

+

Cross section of Riser conductor is:

Cross section of Grid conductor is:

= 237.3

240

240

Sq.mm

Sq.mm

So :

1.72 X 104X 0.00393 X

50

Amm2

1

TCAP : Thermal capacity per unit volume from Table 1(IEEE-std 80), in J/(cm3. C)

= 503.422 X ln

234 450

234

Sq.mm

r : Thermal coefficient of resistivity at reference temperature Tr in 1/ C

r : Resistivity of the ground conductor at reference temperature Tr in µ -cm

Ko : 1/ or (1/ r)-Tr in 1/ C

tc : Duration of current in Sec.

Tm : Maximum allowable temperature in C

Ta : Ambient temperature in C

Tr : Reference temperature for material constant in C

o : Thermal coefficient of resistivity at 0 C in 1/ C

[Eq.40 IEEE-Std 80-2000]

Amm2: Conductor Cross Section in sqmm

I : r.m.s Current in kA = Iearth Fault

2- EARTHING CONDUCTORS CROSS SECTION CALCULATION :

Cross Section of earthing conductor is proportional with Earth fault current value.

It is estimated earth fault current from rated symmetrical 3phase S.C current with

these factors :

K1 For Power plant (P.P) S.S

0.75 For Intermediate or far from P.P or transmission S.S

0.6 For End termination or distribution & very far from P.P S.S

50

Therefore :

Iearth Fault = ISC(3ph) * K = 50

RUDESHUR 400 KV PP S/S.So K = for

)ln(

/)10(

0

0

4

2

a

m

rrc

mm

TK

TK

TCAPtIA


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REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


We suppose this current have 50 kA amplitude.

50So : kAILG=3I0=

return to neutral of other substation's transformers via penetrating to earth

so cause hazardous voltages.

Just transmission line impedance is considered for calculation. In Fig 1 equivalent S.C.

is sketched. It must be noted some approximation are applied which :

Fig.1

1- It is supposed behind supposed length of line is slack bus.

2- Fault resistance (RG) is neglected.

- Neutral of transformer return current

3-1 ZERO-SEQUENCE FAULT CURRENT CALCULATION :

It must be noted S.C. current in P.P. have two component.One component

return to neutral of transformer of P.P trough earthing mesh & second part

2) Secondly should be calculated S f or effects of :

- Shield wire effects a) induction

b) conduction

Sf : fault current division factor

Ig : rms symmetrical grid current in A

I0 : zero-sequence fault current in A

So : 1) Firstly should be calculated I0

3- FAULT CURRENT AND DIVISION FACTOR CALCULATION :

Penetrating current to earth result hazardous touch, step & transfer voltages.

Therefore penetrating fault current should be calculated.

[Eq.63 IEEE-Std 80-2000]

03I

IS

g

f

)( 00

0XXXJRRR

VI F


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REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


m

0

1

1

RG

For

single shield wire

For

double shield wire0.0740.189

+ j 0.73582

0.0068406

1.8936

rC = 1.8442

+ j

/km

GMR=

0.379 + j 0.147

1.17902263

0.8076469

ZSpan : Per span self-impedance of the overhead guard wire ( )

Ztowe : Tower/pole footing impedance ( )

Ztower = 10

b) Conduction effect factor : ref.[3]

Electrical parameters of Guard wire :

The impedance of a ladder for sufficiently long line is :

ZeqS : Impedance of ladder networks ( )

1.8936 + j 0.7358 )

/km

1000

For Guard wire 7No.8 =single shield wire m= 0.09

double shield wire m= 0.17

kV Transmission line have shield wire so m = 0.16

3-2-1 SHIELD WIRE EFFECTS CALCULATION : ref.[3]

3-2 DIVISION FACTOR CALCULATION :

a) Induction effect factor :

Diversion factor of current due to guard wire induction according ref.[3]:

Sf(Shield-induct.) = ( 1 - m )

0.778

Number of incoming or outgoing line which have one guard wire : N1Shield =

Number of incoming or outgoing line which have two guard wire : N2Shield =

+N2Shield

Zeq(2Shield)

=

Sf = Sf(shield-cond.) x (1-m) =

Sf(shield-cond.)=

1

RG

N1Shield

Zeq(1Shield)

0.926

+

832.8

200=

For single shield wire

For double shield wire

TowerSpan

SpanSpan

eqS ZZZZ

Z42

2

(1000

)(mSpanZZ gSpan

TowerSpan

SpanSpan

eqS ZZZZ

Z42

2

)(

10log0028938.0000988.0GW

e

CgGMR

DfjfrZ

fDe 4.658


SHEET / CONT

6 / 7

REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


Vb : Base voltage

Zb : Base impedance

X0N : Zero-sequence reactance of networkx1N : Positive-sequence reactance of network in per-unitx2N : Negative sequence reactance of network in per-unitSb : Base power

XS1 : Secondary winding voltage impedance of transformer

x0S1 : Secondary winding zero-sequence reactance of transformer in per-unit

X1N : Positive sequence reactance of network

Ib : Base current

ilg : I lg in per-unit

i0lg : Zero-sequence of ilg

XP1 : Primary winding voltage impedance of transformer

x0P1 : Primary winding zero-sequence reactance of transformer in per-unit

It : Current supplied by local transformer (A)

it : It in per-unit

i0t : Zero-sequence of it

Ilg : Iine to ground fault current according to above fig.

sequence impedances of network and power transformer.

3-2-2 NEUTRAL OF TRANSFORMER RETURN CURRENT CALCULATION :

Following figure has sketched equivalent circuit for positive, negative and zero -

Definition of Required parameters:

X 0 N

X 2 N

X 1 N

I P.U

i 0g

i 0 ti 0 N

X 0 t

X - t

X + t


SHEET / CONT

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REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


1

IG = (Ilg - It )*Sf = 32.15 kA

It = it * Ib = kA8.67

ilg

3= 36.6572109.97 It is known that : iolg =

6.358096 ==> it = 3*i0t =

ilg =Ilg

Ib=

0.13

There are parrallel transformer . Hence equivalent x0t shall be :

0.13x0t total=x0t

Ntrans.=

It is considerd k= 0.6

19.1

Also :

=> x0N= 0.0273

According to the transformer data :

x0t =

0.0091

400 kV 0.45466

For calculating zero sequence impedance of network :

Sb = 315 MVA Vb = kA

507.9

4.619

b

b

bV

SI

3

b

b

bS

VZ

2

ph

bN

I

VX

3

13 b

NN

Z

Xx 1

1

N

N

x

xK

1

02

3

tn

nt

xx

xii

00

0lg00


SHEET / CONT

8 / 9

REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


3 X 100 = 849

d = h= D = 50

[Eq.89 IEEE-Std 80-2000]

Dm =

LC =

[Eq.91 IEEE-Std 80-2000]16411.294

15945 0.0202 0.7

1.00

600 LR = Lr x Nrod = 300

2.6106

D : spacing between parallel conductors in m Ly : maximum length of the grid in the y direction in m

Lx : maximum length of the grid in the x direction in m

Lp = 2400 A = 360000

V

LR : total length of all ground rods in mA : area of the grid in m2

LC : total length of conductor in the horizontal grid in m

Lr : length of each ground rod in m

1.2054

h0=1m (grid reference depth)

LP : peripheral length of the grid in m on the grid in m

Dm : maximum distance between any two points

1

13.288

1

Lx = Ly =

Em = 493.1

600

4- HAZARDOUS VOLTAGES ( TOUCH & STEP ) CALCULATION :4-1 MESH OR TOUCH VOLTAGE :

Em : Mesh voltage

[Eq.84 IEEE-Std 80-2000]

1.3038

13.288

[Eq.80 IEEE-Std 80-2000]

[Eq.81 IEEE-Std 80-2000]

[Eq.83 IEEE-Std 80-2000]

Grid have grounding rod in the corners.

: Spatial soil resistivity

Km : Geometrical factor

Ki : Corrective factor

IG/LM : Average current per unit of effective buried length of the grounding conductor

[Eq.85 IEEE-Std 80-2000]

[Eq.86 IEEE-Std 80-2000]

[Eq.87 IEEE-Std 80-2000]

[Eq.88 IEEE-Std 80-2000]

M

Gimm

L

IKKE

)12(

8ln.

.4..8

).2(

..16ln

2

1 22

nK

K

d

h

dD

hD

dh

DK

h

iim

1iiK

0

1h

hK h

dcba nnnnn ...

P

Ca

L

Ln

.2

A

Ln Pb

.4

yxLL

A

yx

cA

LLn

.7.0

.

22

yx

md

LL

Dn

nKi .148.0644.0

R

yx

rCM L

LL

LLL

2222.155.1


SHEET / CONT

9 / 10

REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


X X X

12213.8=

[Eq.93 IEEE-Std 80-2000]

KS : Geometrical factor

Ki : Corrective factor

V132.0ES=80 0.24 2.61 32.15

KS = 0.24013

LS = 12214

IG/LS : Average current per unit of effective buried length of the grounding conductor

[Eq.93 IEEE-Std 80-2000]

4-2 STEP VOLTAGE :

ES : Mesh voltage

: Soil resistivity

[Eq.92 IEEE-Std 80-2000]

S

GiS

SL

IKKE

RCS LLL 85.075.0

)5.01(11

.2

11 2n

SDhDh

K


SHEET / CONT

10 / 11

REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


803000

2X 0 +

5- STEP & TOUCH VOLTAGE CRITERIA : (maximum allowable voltages limits)

[Eq.30 IEEE-Std 80-2000]

[Eq.33 IEEE-Std 80-2000]

[Eq.27 IEEE-Std 80-2000]

hS : thickness of the surface material in m

For 50 kg body weight

For 50 kg body weight

Estep : step voltage in V

Etouch : touch voltage in V

CS : surface layer derating factor

S : resistivity of the surface material in .m

tS : duration of shock current in seconds

= 0.70

Estep = (1000 + 6 X 0.70

1 - )0.09(

0.09CS= 1-

)X0.116

=

X 3000 )X0.116

0.5

Etouch = (1000 + 1.5 X 0.70 X 3000 679 V0.5

= 2225 V

S

SSStept

CE116.0

)61000(70

S

SSToucht

CE116.0

)5.11000(70

09.02

)1(09.0

1S

S

Sh

C


SHEET / CONT

11 / 12

REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


mm2

mm2

V

V

6- FINAL RESULTS :

GRID

240

240

EARTHING CONDUCTORS CROSS SECTION

RISER

EARTHING RESISTANCE Rg : 0.064

E step (TOLERABLE) :

E touch (TOLERABLE) :

2225

GROUND POTENTIAL RISE GPR : 2.07 Kv

FAULT STEP VOLTAGE ES :

V

679.3 V

Estep(TOLERABLE)<132

7- REFERENCES :

Power Systems. "

IEEE guide for safety in AC substation grounding.

1. ANSI/ IEEE-std 80-2000

2. DIN 57141 - VDE 0141/19

VDE- standard for earthing system in A.C installations.

5. Design of high-voltage open-terminal station BS 7354:1990

6. IEEE-Std 142-1991

" IEEE Recommended Practice for Grounding of Industrial and Commercial

< Etouch(TOLERABLE)

3. B.Thapar and Sunil K.Madan; " CURRENT FOR DESIGN OF GROUNDING

SYSTEMS ", IEEE trans. on power apparatus and systems .

4. Practical applications of ANSI/IEEE standard 80-1986, IEEE guide for safety.

1986 .

vol. PAS-103,NO. 9,September 1984.

FAULT MESH VOLTAGE EM : 493.1


SHEET / CONT

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REV CMT - R - U - C - 06 - ET - 801DWG.

No.

TITLE:


PLANT





MAH-TAAB GOSTAR CO.



CUSTOMER:OWNER:

19.05.05

28.05.05

06.06.05

26.06.05

A S

A S

A S

A S

F GH

F GH

F GH

F GH

A GD

A GD

A GD

A GD

M SH

M SH

M SH

M SH

C

D

E

F


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