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DESIGN ASPECTS OF TRACTION SUBSTATION
4.O SPACING AND LOCATION
4.01 The sub-station spacings largely depends upon the permissible voltage drop
at the farthest end, which in turn depends upon various factors such as the traffic
to be moved, anticipated traffic in the future and gradients of the section to be
electrified. The voltage drop at the farthest end is calculated both for normal and
extended feed condtions on the basis of given combination of trains on UP &
DOWN tracks, loads and specified speeds, track parameters of the section on the
assumed length of the feed zone. The calculations are repeated for different
assumed lengths of feed zone and it is ensured that the voltage at the farthest end
is within the permissible limits.
4.02 Alternatively, the power requirement is calculated on the basis of average
specific energy consumption of goods and passenger trains Following figures of
specific energy consumption are taken for level or lightly graded sections.
(a) Goods train - 11 kwh. 1000 GTKM
(b) Pass train - 19 kwh. 1000 GTKM
For Medium or heavily graded sectins, the specific enery consumption
figures have to be based on trials. The power requirement is calculated by the
formula as given below :-
Where,
Q x (2Lo) x W 60 1
P = X X KVA
1000 H cosø
2 X Lo = Sub-Stn. covering area for double track line(km)
W = Weight of a train in tones
Q = Energy consumption rate (kwh/1000 GTKM)
H = Headway in minutes during peak time (assumed)
COSø = P.F. (lagging)
Conversely, using the above formula ‘Lo’ can be calculated for a given
rating of traction transformer. Typical calculation based on this formula is shown
below -
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