INTRODUCTION
General Guidelines for
765/400/220/132kV substations and
switchyard of Thermal/ Hydro Power Projects
i) This document is an effort to consolidate maximum possible technical information/ data pertaining to switchyard for thermal/ hydro power projects and also sub-stations as per general prevailing practices for the use/ guidance. However, the site specific requirements need to be looked into by the owner/ developer of the systems.
ii) The sub~stations/ switchyards constitute of transmissiOn system, which interconnects power transmission · circuits and transformation between networks of different voltages. It is required to pay careful attention in planning, designing and constructing the sub-stations/ switchyards, since its reliability directly affects the power supply availability. Sub-stations generally comprise of switchgear, power transformer, control, protection, monitoring and· automation equipment. The highest transmission system voltage in operation in the country is 800kV. Further, 1200kV level is also under consideration in near future.
iii) The sub-stations are of three types based on its use, viz Substations attached to
thermal/ hydro power stations (which is generally called as Switchyard), interconnecting sub-stations, step-down (EHVIHV, EHVIMV, HVIMV) substation. However, the sub-stations shall be of Air insulated sub-station (AIS), Gas insulated sub-stations (GIS) or Hybrid sub-stations.
AIS is most commonly used so far; however, GIS/ hybrid substation may be
adopted considering techno-economic viability. GIS is generally preferred, where availability of space and safety are major constraints, seismic prone areas, coastal areas and very heavily polluted areas etc.
Hybrid sub-station (combination of AIS and GIS) are available upto 220kV
level which requires comparatively less space than AIS. For renovation/
augmentation of existing AIS, hybrid option may be adopted considering
space constraints and techno-economic viability.
iv) This document describes salient parameters and technical features of
equipment required for sub-stations and switchyard associated with thermal/
hydro generating stations. Specific details in respect of GIS and hybrid sub-
station have been covered in Annexure-A and B.
SYSTEMPARAMETERS
The system parameters for 765kV, 400kV, 220kV, 132kV and 33kV are given
in Schedule - 1
3.0 SWITCHING SCHEMES
The selection of switching schemes depends on operational flexibility, system
safety, reliability & availability, ability to facilitate the system control and cost.
However, other types of switching schemes can be considered, if system
demands.
Following switching schemes shall generally be adopted at various voltage levels
of switchyards/ sub-stations. The various types of switching schemes are shown
in the Annexure -C."
General Guidelines for
765/400/220/132kV substations and
switchyard of Thermal/ Hydro Power Projects
The actual layout shall depend upon the type of sub-station! switchyard (viz Air
insulated sub-station (AIS), Gas insulated sub-station (GIS) or Hybrid sub-station). The area required would depend on voltage level, switching schemes,number of feeders of different voltage levels, no. of transformers, compensating equipments and possibility of future expansion.
In case of thermal power stations, the location of the switchyard shall be decided
depending upon the wind profile to avoid additional pollution on account of
water droplets from cooling towers.
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