Answer / gkg

For Active load,voltage will be 48vdc or 24vdc,
so total active load=48v x 28A =1344w =1.34kw

passive load calc ok.

Answer / chandrashekar

Generally in telecom shelter only Passive and Activie load
will be available.
Passive loads are battery bank, PIU and Power plant. and In
active loads Concern BTS and Transmission load.

Thumb rule to calculate DG rating is KW=KVA*PF(0.8) or
Efficiency

i.e KVA=KW/PF


Example to calculate the rating of DG.

If total Load is available 15Kw both active and Passive
then

we should apply above formula KW=KVA*0.8

15=KVA*0.8 KVA = 15/0.8=18.75KVA
we can consider nearest rating of DG i.e=20KVA








Active Load Calculation:

Say a shelter is having only 1nos of BTS,Each BTS will
consume 20A to 30A load current depends up on type and make
of the BTS. average if we take 25A.
Transmission load for each BTS is about 3A total
transmission load current is 3A.
Now the Total Active Load current is =25+3=28A

Total Active load is P=VI P=230*28=6.4KW

Passive Load Calculation
1) AC Unit 2tr 1No the load is =7KW
2) All Internal Lighting and other =1KW
total passive load is 8KW now the toatl active and passive
load is =6.4+7+1= 14.4 KW round off 15KW.
for 15KW load 20KVA Dg set is sufficient

NOTE: always we should consider 1.5% extra rating because
starting current will always 1.5 % higher than load current.

Answer / dhananjay vats

VXI(BTS LOAD)=W/1000=KW.....A
8% LOAD LOSSES IN KW.........B
10% B.B CHARGING LOAD (EX-600AH, 60AX54V/1000)....C
INCOMING LOAD IN KW....C
AC IN KW (EX-1TR, 1TR-1350W, 1.3KW)......D
TOTAL ADD IN KW=A+B+C+D.....CONNECTION EB IN KW
KW=KVA/P.F

Please sent me some previous year question papers of BSNL-JTO telecom and RRB in ELectrical Engineering to varshashahi@yahoo.com

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