Answer / divay chadha

3core-185 sq. mm

Calculation:-

Current at HT = (1500 x 1.4)/ (33*1.732)

Answer / s.srinivasan

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

Answer / j.kesavan

please slect your cable in 11kv py side how much current
check first after you slect your ht cable.

Answer / neeraj tyagi

simple for 11kv
Amp in HT= kva*1000/ 1.732*11000

= size for 78 amp HT XLPE 3 core 95 mm2 higher side.

Answer / gb

11kv----13 amps on primary side

1500 kva 1.4 = 2100 amps on secondary

Answer / madhu mohan

First calculate the current of primary side(HT) and derate the cable by atleast 0.7.
Eg:1500*1000/(1.732*11000)=78.73A
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 50KA.it less go for next size and finalise.

Answer / sairaj

90 Sq.mm Al Ar XLPE cable is sufficient. But as per statutory norms for 11kV, 185 Sq.mm Cable is considered.

Answer / murugan

How to select different types of Transformer KVA rating,
with matching cable size in Primary and secondary..?

100kva TR = cable size with full load amps rating
150 kva TR = ???
250 kva TR = ???
500 kva TR = ???
750 kva TR = ???
1000 kva TR = ???

The cable size
95 sqrmm
120 sqmm
150sqrmm
185 sqrmm
240 sqrmm
300 sqrmm
400 sqrmm
500 sqrmm

Answer / engr. md n h shabuj

S=(Ish *√t)/K
=(10.49*√1)/0.143
=73.35
=75Rm cable

Ish =P/ (√3*V* % of Z)
= (1500*10^3 )/( √3*11*10^3*7.5%)
=1049A
Ish =1049*10=10490A=10.49KA

Answer / saad yar khan

Where can I get the chart for selecting HT cable based on 1500KVA i.e 78Amp

Transformer diagram mention each parts ?

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