Substations serve as crucial links between power generation and distribution, stepping down voltage levels to meet customer needs. The document details various types of substation layouts, such as single and double busbar systems, highlighting their operational flexibility, reliability, and maintenance considerations. Additionally, it outlines standard clearance requirements and lists essential equipment used in substations, emphasizing the importance of careful layout and equipment selection for operational efficiency and system safety.

1. SUB STATIONS

2. Introduction
 Sub Stations are important link between
Generating stations and Distribution networks.
 They step down the EHV to HV as per the
requirement of the customers.
 Stability of the system, reliability of power
depends on the type of layout chosen and
components used in the sub stations.
 Hence great care has to be taken to select the
layout and critical equipment for the SS.

3. ~
Transmission line Yard in Receiving
StationOut door yard in Generating Station
Out door yard in
Generating station

4. Basic Requirements
 Total land area & Ease of extension
 Soil condition & Soil resistivity
 Right of way for incoming and outgoing lines
 Facility to move heavy Equipments
 Load Centre
 System Security
 Operational Flexibility
 Simplicity of protection arrangement
 Ability to limit short circuit levels
 Maintenance
 Cost

5. Types of layouts
 Single Busbar System
 Single Busbar System sectionalising arrangement
 Double Busbar system
 Single Busbar with ring Bus
 Double Busbar with Transfer Bus
 One and Half Breaker arrangement
 Mesh type arrangement

6. Standard clearances
VOLTAGE PHASE TO PHASE PHASE TO EARTH
400 KV 4.000 Mtrs 3.50 Mtrs
230 KV 3.350 Mtrs 1.650 Mtrs
110 KV 1.675 Mtrs 1.000 Mtrs
66 KV 1.220 Mtrs 0.750 Mtrs
33 KV 0.915 Mtrs 0.610 Mtrs

7. Standard clearances
VOLTAGE
CLEARANCE
GROUND
CLEARANCE
SECTIONAL
CLEARANCE
400 KV 8.000 Mtrs 10.000 Mtrs
230 KV 5.500 Mtrs 4.270 Mtrs
110 KV 4.600 Mtrs 3.350 Mtrs
66 KV 4.600 Mtrs 3.050 Mtrs
33 KV 3.650 Mtrs 2.750 Mtrs
22 KV 3.650 Mtrs 2.750 Mtrs
11 KV 3.650 Mtrs 2.600 Mtrs

8. Standard Bay Width
VOLTAGE BAY WIDTH
400 KV 27.000 Mtrs
230 KV 15.900 Mtrs
110 KV 9.500 Mtrs
66 KV 7.000 Mtrs
33 KV 4.600 Mtrs
22 KV 3.800 Mtrs
11 KV 3.500 Mtrs

9. Single Busbar System
 Single busbar with a sectionalizing arrangement
can be erected to give more flexibility for
operation and maintenance.
 Single busbar with ring shaped bus can be
Constructed for connecting many feeders from
the substations.

10. Single Bus Scheme
1

11. Single Busbar System
 This system consists of a single bus to which
various feeders are connected.
 In case of a fault in bus / maintenance entire
bus bar has to be shut down.
 Provides least flexibility.
 Simple and most economical.
 This type of layout is adopted for Small and
Medium size Substations and Power stations.

12. Double Bus Scheme
1

13. Double Busbar System
 Double Busbar system consists of two buses to which all the
feeders emanating from a substations, are connected by
suitable switching arrangement.
 Provides more flexibility, continuity of supply and periodical
maintenance on the bus is also possible without Total
shutdown.
 In this arrangement the busbars are called Main and Reserve
Busbars.
 A Breaker can be introduced between the buses to have
more operational flexibility.
 A double busbar system with a Transfer bus are constructed
to have more reliability and easy maintenance of Equipment.

14. Main & Transfer Bus Scheme
1

15. Double Bus & Transfer Bus Scheme
1

16. One and a Half Breaker System
1

17. Double Busbar System
 In this arrangement three circuit breakers are used to
control two feeders
 Any circuit breaker can be switched off without difficulty for
maintenance works.
 This system has high security against loss of supply.
 Suitable for switch yards of large Generating stations
handling large quantity of Power in individual
circuits/feeders.
 High cost but system security is very high.

18. Ring (Mesh) Bus Scheme
1

19. Ring (Mesh) Bus Scheme
 In this arrangement three circuit breakers are used to
control two feeders
 This type of layout is used to minimize the no of Breakers
used in a Substation.
 The breakers are connected in the mesh formed by the
buses. The circuits are tapped from the node points of the
Mesh.
 Four breakers are utilized to control eight circuits.
 This arrangement is widely used in United Kingdom.

20. 33/11 KV Substation (Regular) - SLD
1

21. 33/11 KV Substation (Regular) - Plan
1

22. 110/22 KV or 110/11 KV Substation - SLD
1

23. 110/22 KV or 110/11 KV Substation - Plan
1

24. 230/ 110 KV Substation – SLD (Single Bus)
1

25. 230/ 110 KV Substation – Plan (Single Bus)
1

26. 230/ 110 KV Substation – Plan (Double Bus)
1

27. 230/ 110 KV SS – SLD (Main & Transfer Bus Scheme)
1

28. 230/ 110 KV SS – Plan (Main & Transfer Bus Scheme)
1

29. 230/ 110 KV SS – SLD (Double Bus Scheme)
1

30. 230/ 110 KV SS – Elevation (Double Bus Scheme)
1

31. 400/230 KV SS – SLD (One and a Half Breaker System)
1

32. 400/230 KV SS – Plan (One and a Half Breaker System)
1

33. Standard clearances in outdoor sub-stations
1

34. Main Equipment in Substation
 Power/Auto Transformers,
 Circuit Breakers,
 Instrument Transformers,
 Surge Arresters,
 Control and Relay Panels,
 Station Batteries and Battery Chargers,
 DC and AC Panels,
 Control Cable,
 Isolators with and without Earthing Device,
 Capacitors, Reactors, Busbar materials,
 Insulators, Connecters etc.

35. Types of SS
 Transformer Substation: Transformer are installed to transform
power from one level to another as per needs.
 Switching Substations: This substation are erected for switching
operation of power lines with out transforming the voltage.
 Power factor correction Substation: This substation installed to
increase the power factor to minimize losses.
 Frequency Changer Substation: This substation installed where
speed controlled of motor required.
 Converting Substation: This substation convert A.C to D.C or vice
versa.
 Industrial Substation: This substation installed for supply power
only to industry.

36. Types of SS
 Paralleling sub station. The SS where power from
different source of generation are paralleled. Two system
has to get connected (parallel), synchronizing facility
needed .
 Must have reliable Communication with Load dispatcher
and generating stations.
 Double bus with a transfer bus arrangement will be most
ideal type of layout
 Major receiving station : The power handled by the
station is high.
 One and a half breaker layout will be suitable.
 Reliable communication, duplicated protection system,
Spare capacity of Auto transformer , good security in
system are needed.

37. Generating station layout
 Depends on the Nos of generator in the station.
 Should have a layout which should not affect generation even one unit
is shut down
 Double bus with transfer bus is most suitable. However a single bus
scheme with two feeders can be considered for a station with single
generating unit
 Should have reliable communication with Load dispatcher and
receiving station.
 Located adjacent to the power house.
 Indoor / outdoor AISS or GISS are generally considered suitable
for major generating stations.
 In under ground power generating stations transformer yard is
located near the generators and the EHV is taken thru EHV cables to
the outdoor yard.

38. Main Equipment in Substation
Selection of right type of Layout, Equipments
of adequate ratings and correct Protection
system will make the Power system Safe,
Secure and also give operational Flexibility.