Technical data

CHAP-04.10 ELECTRICAL POWER DISTRIBUTION, DRIVES, CONTROL &
ILLUMINATION ELECTRICAL
Page 2 of 50
scope of Contractor. Power to all the HT motors will be supplied from the
6.6kV HT Switchboards.
Adequate number of LT Substations (LTSS), (at suitable locations to be
decided by the Contractor) each comprising of LT switchboard along
with two transformers will be included by the Contractor in his scope of
work. The transformer rating will be worked out on the basis of
guidelines given in General Technical Specification. However, the rating
of transformers will be 2000/ 1000 kVA depending upon the load. The
interconnection between transformer secondary and LT switchboard will
be through bus ducts.
The Contractor will indicate the numbers of 11KV and 6.6 kV feeders
required by them from HTSS during Basic Engineering to provide HT
feeders by Employer. The Contractor will indicate the details of
connected load (KW) & Maximum Demand in 15 min. duration for each
feeder and also the overall expected maximum demand in 15 min
duration for the entire plant under normal operating conditions.
The following are to be considered in addition to the equipment
specification spelt out in GTS.
a) The vector group for all distribution transformers (LT S/S) will be
of Dyn11 only to take care of circulation of harmonic currents.
However, care should be taken not to envisage mixing of supply
with the existing LT power sources of 2.5 MT area as the existing
distribution transformers are of Yy0 vector group.
b) Separate analogue voltmeters for line voltage & bus voltage and
ammeter in each of the three phases will be provided.
c) All out going ACBs will be 800A, 1000A or 1600 A as per
requirement with protection settings selectable at site.
d) Check-synchronising relay will be provided wherever
sectionalizing is envisaged between two different sources of
power supplies.
e) Care should be taken to avoid location of LT Substations under
Conveyor galleries/ dust prone areas.
f) LT Bus-duct insulators will be of porcelain.
g) The CT mounting arrangement inside the cable chambers of all
feeders will be such that CTs and secondary connections will be