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How to calculate HT XLPE CABLE for 11 kv / 433 v , 1500 kva
oil type transformer system?
plz provide step by step calculation
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
# 1
3core-185 sq. mm


Current at HT = (1500 x 1.4)/ (33*1.732)
Is This Answer Correct ?    137 Yes 80 No
Divay Chadha
# 2
Generally HT cable sizing is not done based on the full
load current of the equipment but based on the prospective
fault level. For a 11kV network, generally it shall not be
less than 150sqmm XLPE.

Fault level at 11kV(furnished by respective EB)=100 MVA(say)

Details on EB's fault level can be obtained from EB.

Therefore fault current= 100*1000/(SQRT(3)*11000)
= 5.25 kA

Short circuit current rating (for 3-sec duration)of HT 11kV
XLPE cables with Alu conductor is as below:
95 sqmm: 5.16 kA
120 sqmm: 6.51 kA
150 sqmm: 8.14 kA
Is This Answer Correct ?    61 Yes 14 No
# 3
please slect your cable in 11kv py side how much current
check first after you slect your ht cable.
Is This Answer Correct ?    63 Yes 28 No
# 4
simple for 11kv
Amp in HT= kva*1000/ 1.732*11000

= size for 78 amp HT XLPE 3 core 95 mm2 higher side.
Is This Answer Correct ?    56 Yes 27 No
Neeraj Tyagi
# 5
11kv----13 amps on primary side

1500 kva 1.4 = 2100 amps on secondary
Is This Answer Correct ?    27 Yes 14 No
# 6
First calculate the current of primary side(HT) and derate the cable by atleast 0.7.
Current I after Derating =78.73/.7 =112A (0.7 if laid on the trays or value will vary if buried in the ground).
Cable equivalent to rating has to be selected.
Now Short circuit withstand capacity (sq. of I X t in sec) has to be checked from the cable catalogue.This value of cable should be higher then SC withstand capacity of the ground usually it is less go for next size and finalise.
Is This Answer Correct ?    18 Yes 12 No
Madhu Mohan
# 7
HT Cable select, its depend of incoming capacity of feeder
line. say feeder capacity 100 MVA SO Calculate current I=
100*100/11*1.73=5.25kA. So we can select of HT Cable for
minimum short ckt current carrying capacity of minimum 5.2kA.
Is This Answer Correct ?    1 Yes 0 No
# 8
1500kVA X 0.8 PF = 1200Kw = 1200000W

P=RT3 V I COS fi

I = -----------
RT3 x V x COSfi

I = -----------------

= 79 A

Now take cable table and select the suitable xlpe cable.

Is This Answer Correct ?    28 Yes 29 No
# 9
Assume PF of transformer is .8.
rating of transformer=1500kVA=1500X.8=1200kW
So that maximum current-
So cable size required if copper cable
1mm=4amp= 400sqmm(by consedering all factors)
For aluminium cable
Is This Answer Correct ?    56 Yes 88 No
Govind Bisht
# 10
for 11kv side current = kva*1000/1.732*11000

= 78.73 amps
for 78.73 amps 3 core 25 sqmm cable is sufficient
Is This Answer Correct ?    22 Yes 71 No

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