This document provides an overview of substations, including their classification, components, and grounding practices. It defines a substation as a place where voltage is transformed from high to low levels using transformers. Substations are classified by voltage level (e.g. EHV, HV, MV, LV), configuration (outdoor vs indoor), and type (conventional vs gas insulated). The document outlines the typical components of a substation and best practices for proper grounding to ensure reliability, safety, and trouble-free operation.

1. SUBSTATION OVER VIEW
Presented by
T . Sai Krishna
14G25A0217
Ascet-Gudur
Guide:
Mr.G.Venkateswarlu,M.Tech.

2.  A Station is a subsidiary station of an electricity
generation, transmission,& distribution system where
voltage is transformed to high to low or the reverse using
transformers.
 A substation generally have switching, protection, &
control equipment & one or more transformers

3. Classification based on voltage levels, e.g. : A.C.
Substation : EHV, HV, MV, LV; HVDC Substation.
Classification based on Outdoor or Indoor :
Outdoor substation is under open sky. Indoor
substation is inside a building.
Classification based on configuration, e.g. :
Conventional air insulated outdoor substation or
SF6 Gas Insulated Substation (GIS)
Composite substations having combination of the
above two

4. Primary Substations receive power from EHV
lines at 400KV, 220KV, 132KV and transform the
voltage to 66KV, 33KV or 22KV (22KV is
uncommon) to suit the local requirements in
respect of both load and distance of ultimate
consumers. These are also referred to ‘EHV’
Substations.
Secondary Substations receive power at 66/33KV
which is stepped down usually to 11KV.
Distribution Substations receive power at 11KV,
6.6 KV and step down to a volt suitable for LV
distribution purposes, normally at 415 volts

5. Outdoor Switchyard
Incoming Lines
Outgoing Lines
Bus bar
Transformers
Bus post insulator & string insulators
Substation Equipment such as Circuit-beakers,
Isolators, Earthing Switches, Surge Arresters,
CTs, VTs, Neutral Grounding equipment.

6. Station Earthing system comprising ground mat, risers,
auxiliary mat, earthing strips, earthing spikes & earth
electrodes.
Overhead earth wire shielding against lightening strokes.
Galvanised steel structures for towers, gantries, equipment
supports.
PLCC equipment including line trap, tuning unit, coupling
capacitor, etc.
Power cables
Control cables for protection and control
Roads, Railway track, cable trenches
Station illumination system

9. Vented / Flooded
Lead Acid batteries
Sealed
maintenance free
batteries/Valve
Regulated Lead
Acid
Nickel Cadmium
(Ni-cd) batteries

11. VOLTAGE LEVEL MINIMUM GROUND CLEARANCE
less than 66kV 6.1m
66kV - 110kV 6.4m
110kV - 165kV 6.7m
greater than 165kV 7.0m

12. Major power station= 0.5 Ohm.
Major Sub-stations= 1.0 Ohm
Minor Sub-station = 2 Ohm
Neutral Bushing. =2 Ohm
Service connection = 4 Ohm
Medium Voltage Network =2
Ohm
L.T.Lightening Arrestor= 4 Ohm
L.T.Pole= 5 Ohm
H.T.Pole =10 Ohm
Tower =20-30 Ohm

13. Type Voltage
EXTRA LOW
VOLTAGE
Up to 50V AC/DC
LOW VOLTAGE 50-1000V AC/DC
MEDIUM VOLTAGE ABOVE 1000V AC/DC UPTO 6.6KV
AC
HIGH VOLTAGE ABOVE 6.6KV AC TO 33 KV AC
EXTRA HIGH
VOLTAGE
ABOVE 33KV AC TO 400 KV AC
ULTRA HIGH
VOLTAGE
ABOVE 400 KV AC TO 765 KV AC

15. The following steps, when put into practice, will ensure a
reliable, safe and trouble-free substation grounding system:
Size conductors for anticipated faults
Use the right connections
Ground rod selection
Soil preparation
Grounding using building foundations
Grounding the substation fence
Special attention to operating points
Surge arrestors must be grounded properly
Grounding of cable trays
Temporary grounding of normally energized parts

16. Laying direct in ground
In pipes,
Closed or Open ducts,
Cable trays and
On surface of wall

17. Fire fighting system
D.G. Set
Oil purification system