ht cable sizing cal.for ht swbd, dist. trafo. & ht motor 27.07.10.doc

8/9/2019 HT Cable Sizing Cal.for HT SWBD, Dist. Trafo. & HT Motor 27.07.10.doc

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HT CABLE SIZING CALCULATION

PROJECT100TPH CLINKER GRINDING PLANT,

DAR Es - SALAAM.DOC NO.

17/0035-EL-04-

80

CLIENT M/s. WALCHANDNAGAR INDUSTRIES LTD., PUNE. DATE 4.0!.010

CUSTOMER M/s. MAWENI LIMEST"NE LTD. REV NO. 0

ELECTRICALCONTRACTO

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AR#EE ELECTRICALS $ ENGINEERS P#T. LTD.,

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1.0 GENERAL

1.1 The intent of this document is to cover the basis and calculat ions for sizing of

6.6kV (UE), !"E cables re#uired for6.6kV Main Switchboard, Distribution

Transor!"rs, # $T Motors in th" insta%%ations.

&.0 'AS(S # ASS)M*T(+NS

$ollo%ing are the basis and assum&tions made %hile sizing the 'T cables.

.1 6.6kV(UE) grade cables shall be o&&er conductor %ith inner semi conducting la*er

over conductor, !"E insulated %ith semi conducting la*er + co&&er ta&e over insulation

inner sheath, "V etruded outer sheath, armoured cables.

. The cables %ill be laid on cable tra*s and in single la*er %hich %ill be sho%n in cable

la*out dra%ing.

.- esign /mbient has been considered as 0.

.0 6.6kV (UE) able from 1.23V/ "o%er Transformer to 6.6kV 3ain 4%itchboard shall be

sized for carr*ing 6.-k/ short circuit current for 1 second duration since numerical t*&e

&rotective rela*s are &rovided in the s*stem to isolate the fault* e#ui&ment %ithin less

than .0 sec.

.0 6.6kV (UE) able from 6.6kV 3ain 4%itchboard to istribution Transformers shall be

sized for carr*ing 6.-k/ short circuit current for 1 second duration since numerical t*&e

&rotective rela*s are &rovided in the s*stem to isolate the fault* e#ui&ment %ithin less

than .6 sec

.2 6.6kV (UE) able from 6.6kV 5solator "anel to 'T 3otor feeder shall be sized for

carr*ing short circuit current of 6.-k/ for . second duration.

.6 4tarting current for k 47 8 9! motor is - times greater than rated current.

.: $ollo%ing formula %ill be used for calculating receiving end terminal voltage during full

load conditions;

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)1000())(3( tflsr NLSinXCosRIVV +=

here,

rV < Voltage available at receiving end terminals during full load

onditions.

sV < =ominal voltage of the s*stem.

flI < $ull !oad current.

Cos < "o%er factor during stead* state conditions (onsidered as .>2 in

calculations).

7 < 7esistance of &o%er cable ? km in @.

< 7eactance of &o%er cable ? km in @.

! < 7oute length of cable in meter. ( 7oute !ength of cables

considered are the estimated lengths %ith 1A margin)

tN < =umber of 7uns

.> able &arameters such as resistance, reactance values etc. are taken from

atalogues of "ol*cab make cables -o/ attach"d. These values for the cables

to be su&&lied actuall* %ill meet the values assumed in the calculations subBect

to manufacturing tolerances as allo%ed in res&ective standards.

.C alculation for erating $actor 8 6.6kV (UE), !"E, o&&er conductor ables for

7oute of "o%er Trafo. to 6.6kV 'T 4%itchboardD

.!.

1erating factor for 0

/mbient /ir tem&eratures.

1 R". Ann"ur" 2 A3 *o%/cab -ab%"

-ata%o4u" 5 Tab%" No. A or Air #

Ground T"!"ratur" on *a4" No. 7

o 8..!.

ables laid inside concrete

trench, on cable tra*s. The

cables s&aced b* one cable

.>1 R". Ann"ur" 2 A9 Tab%" No. A

on *a4" No. : o 8.

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diameter and tra*s are in tiers

s&aced b* -mm.

=o. of cable < - + =o. of cable

tra*s in tier < -

.!.3

9verall erating $actor for 6.6

kV (UE) able installed

inside concrete trench on cable

tra*s.

< 1 .>1 ; 0.


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7.0 -A'LE S(>(NG -AL-)LAT(+N

3.1 T*&ical calculation of able sizing for 6.6kV )E -o"r ?L*E cab%" ro! 1&.8MVA

*ow"r Transor!"r to 6.6kV Main Switchboard.

7.1.1 -ab%" si@" conir!ation or short circuit withstands caacit/.

a) 3aimum &ossible short circuit current on 6.6kV side 3 5 6.-k/ for 1 sec.

b) 4hort circuit rating of selected cable (7- ? &:0 s. !!) 3 5-0.-k/ for 1 sec.

c) uration for carr*ing short circuit current 3 51 sec.

4hort circuit rating of selected cable is -0.- k/ for 1 sec. %hich is more than of &ossible

short circuit current of 6.- k/ for 1 sec.

$"nc" s"%"ct"d cab%" o si@" 7- ? &:0 s. !!. is suitab%" or Short

-ircuit Bithstand -aacit/.

7.1.& -ab%" si@in4 bas"d on -ontinuous -urr"nt -arr/in4 -aacit/.

a) $ull load current on 6.6kV side;51C-.2/.

b) able size considered 3 5-7 - 0 4#. mm. !"E insulated o&&er

conductor.

c) urrent rating of the cable under standard conditions of installation in trench

i.e. in /ir 3 52/ R". Ann"ur" 2 A9 *o%/cab -ab%" -ata%o4u", Tab%" No.

&: o *a4" No. 8 o 8

d) /s the ables laid on cable tra*s e&osed to air, the erating factor

considered 3 5.>1 R" &.=.7 aboC"

e) erated ca&acit* of cable 3 5112/ as against re#uirement of 1C-.2/.

$"nc" s"%"ct"d cab%" si@" o 7R 7- &:0 S. !!. ?L*E is suitab%"

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or -ontinuous -urr"nt -arr/in4 -aacit/.

7.1.7 -ab%" si@in4 bas"d on Co%ta4" dro durin4 u%% %oad condition.

a) $ull load current on 11kV side;51C-.2/.

b) 7oute length of cable 3 5 1C meter

c) able size considered 3 5 -7 - 0 4#. mm. !"E insulated o&&er

conductor.

d) Voltage at receiving end terminals is given b* follo%ing formula 3 5


e) 7esistance of cable at C 3 5.C62 @ ? km R"3 Ann"ur" 5 A *o%/cab

-ab%" -ata%o4u", Tab%" 1 o *a4" No. 1 o 8

f) 7eactance of cable at 2 'z. 3 5.>2 @ ? km R"3 Ann"ur" 5 A *o%/cab-ab%" -ata%o4u", Tab%" 6 o *a4" No. & o 8

g) "o%er $actor of s*stem (i.e. os);5.>2 lagging. (4in < . 26)

=o% %e have, )1000())(3( tflsr NLSinXCosRIVV +=

)31000()190)526.0085.085.00965.0(5.10933(6600 +=rV

)20.15(6600 =r

V

8.6584=rV V

=o% "ercentage Voltage ro&, A 100)( = srsD VVVV

A 1006600)8.65846600( =DV

A 0.23=DV %hich is ver* negligible.

$"nc" 6.6kV )E, 7R 7- ? &:0 s. !!. ?L*E -o"r conductor -ab%" is ad"uat" or

Vo%ta4" Dro consid"ration.

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7.& T*&ical calculation of able sizing for 6.6kV (UE) o&&er !"E cable from 6.6kV Main

Switchboard to &000kVA Transor!"r.

7.&.1 -ab%" si@" conir!ation or short circuit withstands caacit/.


b) 4hort circuit rating of selected cable (7- ? 1


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7.&.7 -ab%" si@in4 bas"d on Co%ta4" dro durin4 u%% %oad condition.

a) $ull load current on 6.6kV side;51:0.C2/.

b) 7oute length of cable 3 5 - meter

c) able size considered 3 5 - 1>2 4#. mm. !"E insulated o&&er

conductor.

d) Voltage at receiving end terminals is given b* follo%ing formula 3 5


e) 7esistance of cable at C 3 5.1: @ ? km R"3 Ann"ur" 5 A *o%/cab

-ab%" -ata%o4u", Tab%" 1 on *a4" No. 1 o 8f) 7eactance of cable at 2 'z. 3 5.>: @ ? km R"3 Ann"ur" 5 A *o%/cab

-ab%" -ata%o4u", Tab%" 6 on *a4" No. & o 8

g) "o%er $actor of s*stem (i.e. os);5.>2 lagging. (4in < . 26)


)11000()30)526.0087.085.0127.0(95.1743(6600 +=rV

)4.1(6600 =r

V

6.6598=rV V


A 1006600)6.65986600( =D

V

A 0.021=DV %hich is ver* negligible.

$"nc" 6.6kV )E, 7- ? 1


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7.7 T*&ical calculation of able sizing for 6.6kV (UE) co&&er !"E cable from 6.6kV

(so%ator *an"% to 6.6kV &&00kB -"!"nt Mi%% Motor.

7.7.1 -ab%" si@" conir!ation or Short -ircuit Bithstands -aacit/.


b) 4hort circuit rating of selected cable (7- ? 1


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-urr"nt -arr/in4 caacit/.

7.7.7 -ab%" si@in4 bas"d on st"ad/ stat" Vo%ta4" Dro durin4 u%% %oad condition.

a) $ull load current on 6.6kV side;5-0.:/.

b) 7oute length of cable;5 18meter.

c) able size considered; 5 - 1>2 4#. mm. !"E insulated o&&er

conductor.

d) Voltage at receiving end terminals is given b* follo%ing formula 35


e) 7esistance of cable at C 3 5.1: @ ? km R"3 Ann"ur" 2 A, *o%/cab

-ab%" -ata%o4u", Tab%" No. 1 on *a4" No. 1 o 8

f) 7eactance of cable at 2 'z. 3 5.>: @ ? km R"3 Ann"ur" 2 A, *o%/cab


g) "o%er $actor of motor (i.e. os);5.>6 lagging. (4in < . 21)


)11000()15)510.0087.086.0127.0(7.2343(6600 +=rV

)939.0(6600 =rV 061.6599=

rV V


A 1006600)061.65996600( =DV

014.0=DV %hich is ver* negligible.

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$"nc" 6.6kV )E, 7- ? 12 4#. mm. !"E insulated o&&er

conductor.

e) Voltage at receiving end terminals is given b* follo%ing formula 35


f) 7esistance of cable at C 3 5.1: @ ? km R"3 Ann"ur" 2 A, *o%/cab

-ab%" -ata%o4u", Tab%" No. 1 on *a4" No. 1 o 8

g) 7eactance of cable at 2 'z. 3 5.>: @ ? km R"3 Ann"ur" 2 A, *o%/cab


h) "o%er $actor of s*stem at starting (i.e. os);5 .- lagging.

(4in < . C2)


)11000()15)95.0087.03.0127.0(1.7043(6600 +=rV

)22.2(6600 =r

V

78.6597=rV V


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A 1006600)78.65976600( =D

V

034.0=DV %hich is ver* negligible.

$"nc" 6.6kV )E, 7- ? 12 s#. mm.

!"E cable( 6.0 k/ for 1 sec) is more than the &ossible short circuit current (i.e.

6.-k/ at . sec.) in the s*stem for 'T 3otor feeder.

0.0 The current carr*ing ca&acit* of selected cables after deration is more than the

re#uired current of the s*stem.

0.2 4ince the stead* state voltage dro& is much less than s&ecified value of 2A, the cable

selection is correct from voltage dro& &oint of vie%. The attainable stead* state

voltage dro& in cable is much less than the &ermissible voltage dro&.

0.6 4ince the starting voltage dro& is much less than s&ecified value of 12A, the cable

selection is correct from voltage dro& &oint of vie%. The attainable starting

voltage dro& in cable is much less than the &ermissible voltage dro&.

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Th" s"%"ct"d cab%"s co!%i"s with a%% th" r"uir"!"nts and h"nc" th" s"%"ction o

6.6kV )E, 7- ? &:0 s. !!. ?L*E insu%at"d -o"r -ab%" or 6.6kV Main Switchboard #

6.6kV )E, 7- ? 1

ht cable sizing cal.for ht swbd, dist. trafo. & ht motor 27.07.10.doc

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