The document provides an overview of substations, including their functions, types, and equipment. Key considerations such as load growth, reliability, and technical specifications are discussed, along with different substation types like transformer, switching, and industrial substations. It also covers important aspects of substation design and layout, earthing systems, and bus switching schemes for operational effectiveness.

1. Welcome to Aarambh
Todays Topic : Substation and its Equipment's
Hello!
1
Faculty : Chandan Kumar, Manager, ERLDC
Senior Member IEEE, M-IEI, M-CIGRE

2. Substation

3. 3
Power System

4. 4
◉ Substation is a part of an electrical generation,
transmission and distribution.
◉ Substation transform voltage from high to low, or the
reverse or perform any of several other important
functions like switching, converting etc.
Substation

5. 5
◉ Practical consideration
○ To satisfy load growth
○ To accommodate new generation
○ To maintain reliability requirement
○ To Optimize cost of electricity
◉ Technical consideration
○ To step up and step down ac voltage level
○ To break the power flow
○ Provide support to the power flow
○ Equipment Rating limit
Need of Substation

6. 6
◉ Transformer substation
◉ Switching substation
◉ Power factor correction
substation
◉ Frequency changer
substation
◉ Industrial substation
◉ Converting substation
Types of Substation
◉ Outdoor substation
◉ Indoor substation
◉ Underground substation
◉ Pole mounted substation
SERVICE
REQUIREMENT
SERVICE
REQUIREMENT
CONSTRUCTIONAL
FEATURES
CONSTRUCTIONAL
FEATURES

7. Transformer substation
◉ Change the voltage level.
◉ Transfer of Power at various
voltage level.
◉ It has varying voltage level.
◉ Ex: 765/400/220/132 kV
7

8. Switching Substation
◉ These type of substations simply
perform the switching operation
of power lines.
◉ Long transmission lines
switching.
◉ Ex: 400 kV Raigarh substation in
WR for switching 400 kV Raipur-
Rourkela ckts.
◉ No Transformers will
be available at this
substations.
8

9. Power Factor Correction
Substation
◉ Those sub-stations which
Improve the power factor of the
system are called Power factor
correction Substation.
◉ These are Generally located at
the Receiving end of
transmission lines.
◉ They generally use synchronous
condensers as power factor
improvement equipment
9

10. Frequency Changer Substation
◉ Substation which changes
supply frequency.
◉ Mainly used for industrial
loads which are designed for
different frequency.
10

11. Industrial Substation
◉ Substation which are made to
cater industrial load.
◉ Mainly at High voltage level.
◉ Cater areas like Special
economic zone, Heavy
industrial area.
11

12. Converting Substation
◉ Use to convert ac power into
dc power by using static
converting devices like SCRs.
◉ Used for traction,
electroplating and welding.
12

13. Outdoor Substation
◉ Air Insulated substation (AIS)
◉ Mainly for voltage level 66 kV
and above where clearance
between conductor and the
space required for switches,
C.B., and other equipment
becomes so great that it is not
economical to install the
equipment indoor.
13

14. Indoor Substation
◉ Indoor type of substation are
for voltages up to 11 kV but
this range can be increased up
to 66 kV if atmosphere is
contaminated with impurities.
◉ Another type is Gas Insulated
substation (GIS) which can be
up to 765 kV voltage level.
◉ Reduces space like in Urban
areas 14

15. Underground substation
◉ Mainly in this category are
distribution substation in
urban areas.
◉ Costly and limited space.
15

16. Pole Mounted Substation
◉ This is an outdoor sub-station
with equipment installed
overhead on H-pole or 4-pole
structure
◉ Used for voltages up to 11kv
(33kv in some cases).
16

17. 17
◉ Radial Substation
◉ Tapped-Substation
◉ LILO (Line In Line Out) Substation
◉ Interconnected Substation
Substation Type based on Connectivity

18. 18

19. 19
◉ Step up substation,
◉ Primary grid substation,
◉ Secondary substation,
◉ Distribution substation,
◉ Bulk supply and industrial substation,
◉ Mining substation
◉ Mobile substation.
Substation based on Location in the Power
System Networks

20. Substation
Equipments

21. 21
Substation Layouts
1 Primary Transmission line 7 Current Transformer
2 Ground Wire 8 Lightening arrester
3 Overhead line 9 Power Transformer
4 Transformer for Voltage of
Primary side
10 Control Room
5 Disconnect switch/isolator 11 Security fence
6 Circuit Breaker 12 Secondary Transmission line

22. 22
◉ Can be Train/Flexible/rigid
type.
◉ Overhead conductor can be
strain/flexible type. For 220 kV
and above bundled conductors
are used (ACSR/AAC).
◉ In rigid type, Aluminum pipes
are used (D Type layout)
Bus Bar

23. 23
◉ Vital & Costliest
equipment, 3 phase or 1
phase based on transport
limitations
◉ Two winding or Auto
transformer– based on
voltage ratio
◉ On load type/ off load type
tap changer
Power Transformers

24. 24

25. 25
◉ Reactive Compensation-
line or bus connected
◉ Control of dynamic over
voltages
◉ Neutral grounding reactor
for single phase auto
reclosing
◉ 3 phase or 1 phase based
on transport limitations
Shunt Reactors

26. 26
◉ On-load mechanical switches
used for making, carrying and
breaking currents under normal
conditions and breaking under
abnormal conditions.
◉ Air Break CB, Oil CB, Minimum oil
CB, Air Blast CB, SF6 CB, Vacuum
CB
◉ Operating Mechanism: Hydraulic,
Pneumatic & Spring – Spring.
◉ Breaking time in ms range.
Circuit Breaker

27. 27

28. 28

29. 29
◉ Isolator provides a visible air gap isolation of
equipment and feeder sections for safe
examination, maintenance and repair. It is
capable of carrying normal current and short
circuit current for a specified time.
◉ Horizontal centre break
◉ Double Break
◉ Pantograph
◉ Vertical single break
◉ The earth switch of isolator is a mechanical
switching device for providing safety earthing
during maintenance. It is capable of
withstanding short circuit current for a specified
time.
Isolators

30. 30
◉ These are the devices used
to get the replica of
primary current which
shall be suitable for
measuring instruments and
protective relays.
◉ No. of cores as per
requirement.
◉ Dead Tank or live Tank
Instrument Transformers (Current Transformer)

31. 31

32. 32
◉ Devices used to get the replica
of primary voltage which shall
be suitable for measuring
instruments and protective
relays.
◉ No. of cores as per requirement
◉ CVTs used generally above
220kV for economic reasons -
also obviates need for separate
coupling capacitor for PLCC
Instrument Transformers (Potential Transformer
/ Capacitor Voltage transformer)

33. 33
◉ Surge arresters made of ZnO
disc provide the primary
protection against over
voltage caused by external
sources e.g. lightning and by
system disturbances
(switching)
◉ Designed w.r.t MCOV,
Energy, capability, Pressure
relief capability
Surge Arrester

34. 34Line Termination in substation

35. 35
Line side to Bus side bay entry

36. Substation Grounding

37. 37
◉ In HV/MV Air Insulated Substations (AIS) the electromagnetic field, which
causes are the static charges of bare cable and conductors and by the
atmospheric conditions (surges), induce voltages at no-live parts of the
installation that create potential differences between metallic parts and
ground and also between different points of the ground.
◉ Similar situations can occur when there are faults between live parts of
the installation and no-live parts, for example in phase-to-earth short
circuit.
◉ These potential differences give origin to step potential and touch
potential, or a combination of both, that can lead to circulation of an
electric current through the human body, that can cause hazardous to
people.
Why Earthing is Important?

38. Purpose of Earthing
◉ Safety of the living beings around the vicinity of the substation
by limiting the touch and step potential within tolerable limits
◉ Proper functioning of the protection system under fault condition
◉ Discharge the over voltages from overhead ground wires or the
lightning masts to earth and providing ground path for surge
arresters.
◉ Provide a path for discharging the charge between phase and
ground by means of earthing switches.
◉ To provide earth connections to structures and other non-
current carrying metallic objects in the sub-station (equipment
earthing). 38

39. Basic Shock Situation
39https://electrical-engineering-portal.com/res/res4/Best-practice-in-power-substation-grounding.pdf

40. Human Safety
Current Range Effects on Humans
➢ 1 mA Threshold of perception
➢ 1-6 mA Let go currents
➢ 9-25 mA Pain full, hard to let go
➢ 25-60 mA Muscular contractions
➢ 60-100 mA Ventricular fibrillation
40

41. 41
Provide under and around the substation a surface that shall be at a
uniform potential and near zero or absolute earth potential as
possible
◉ It stabilizes circuit potentials with respect to ground and limits the
overall potential rise.
◉ It protects life and property from over voltage.
◉ It provides low impedance path to fault currents to ensure
prompt and consistent operation of protective devices during
ground faults.
◉ It keeps the maximum voltage gradient along the surface inside
and around the substation within safe limits during ground fault.
Requirements of a Good Substation Earthing

42. 42
◉ Earthing grid/Mat,
◉ Earthing electrodes,
◉ Earthing conductors and
◉ Earth connections.
Earthing System In a Substation

43. Earthing Mat
◉ A solid metallic plate or a system of closely spaced bare
conductors that are connected to and often placed in
shallow depths above a ground grid or elsewhere at the
earth surface, in order to obtain an extra protective
measures minimizing the danger of the exposure to high
step or touch voltages in a critical operating area or
places that are frequently used by people.
◉ Interconnection of Horizontal and Vertical electrode.
◉ The vertical Electrodes are for the dissipation of fault
current into the ground.
◉ The Horizontal electrodes are laid for suppressing the
dangerous Touch and Step voltages which are generated
due to heavy fault current.
43

44. Earthing Mat
◉ After the construction of Earth Mat, Crushed
Gravels (of resistivity around 5000 ohms) are
laid above the whole mat area.
◉ It provide high resistive path for the dangerous
voltages generated(Touch, Step Voltage), which
in turn prevents a person from electric shock
standing above the Earth mat area.
◉ It is buried horizontally at a depth of about half
a meter below the surface of the ground and
ground rods at suitable points
44

45. Earthing Mat
◉ Earth Mat is connected to the following in a Substation:
○ The neutral point of such system through its own
independent earth.
○ Equipment frame work and other non-current
carrying parts of the electrical equipment's in the
sub-station.
○ All extraneous metallic frame work not associated
with equipment.
○ Handle of the operating pipe.
○ Fence if it is within 2 m from earth mat.
45

46. Earth Electrode
◉ Basically Pipe electrode
◉ Provide additional earthing to support structure as well
as meshed earthing mat .
◉ Several such earth electrode is driven vertically into the
soil and are welded to the earthing rods of the
underground Mesh.
◉ Larger number of earth electrodes gives lower earth
resistance.
46

47. Earthing Conductors
◉ A flexible earth conductor is provided between
the handle and earthing conductor attached to
the devices/panel to be earthed at substation.
47

48. Earthing Connection
◉ A connection between the Earthing conductors
and Earth mat/earthing electrodes.
◉ Equipment connection with Earth electrode or
earth mat.
48

49. Design Consideration

50. 50
◉ With increasing constraints of
transmission line corridors,
difficulty in availability of land due
to urbanization and economic
development, emergence of
stringent social & environmental
regulations and public awareness,
the task of site selection for a
substation has become more and
more complex.
Social & Environmental factor
◉ Habitation, Govt. or Private land ,
Forest encroachment,
Landscaping
Commercial factor : Cost
Site Selection
Technical factors
◉ Area Requirement : Voltage levels, Number
of feeders, No. of Transformers/ Reactors,
Other facilities like housing, Present and
Future requirement
◉ Corridors for line, aeronautics and forest
◉ Pollution
Physical factor
◉ Topography : Site Levelling, adoption of
standard design
◉ Geological : Soil Properties, water table
◉ Geography : Aeronautical corridor, mines,
landslide, flood prone
Infrastructural factor
◉ Easy Access
◉ Amenities Availability
◉ Reliable power & water supply

51. 51
PLANNING ASPECT:
◉ Switching scheme to be adopted.
◉ Details of feeders requirements.
◉ Future/anticipated expansion of
the substation .
◉ Available size of plot .
Layout Consideration
Standard factors
◉ Electrical clearances
◉ Heights of different levels & electric
field
Variable factors
◉ Shape of land & feeder orientation
◉ Bus bar arrangement
◉ Type of isolator used
◉ Type of structures used
◉ Arrangement of lightning protection
◉ Location of control room building,
FFPH
◉ Roads and rail tracks

52. 52
Minimum Clearances for Layout (at altitude <1000m above
mean sea level)

53. Bus Switching Scheme

54. 54
◉ A substation bus switching scheme is the arrangement
of its overhead bus bar and all
associated switching equipment at that same voltage
level (circuit breakers and isolators) in a substation.
◉ The operational flexibility and reliability of the
substation greatly depends upon the bus scheme.
◉ The selection of switching schemes shall be based
upon requirements for operational flexibility, system
safety, reliability, availability and cost.
Introduction

55. 55
◉ Single Main Bus Scheme ‘
○ with sectionaliser & without sectionaliser
◉ Double Main Bus Scheme
◉ Single Main & Transfer Bus Scheme
◉ Double Main & Transfer Bus Scheme
◉ One & Half Breaker Bus Scheme
◉ Double bus two breaker Scheme
◉ Ring Bus Scheme
Types of Bus Switching Scheme

56. Single Bus Scheme
◉ Simplest and cheapest bus bar scheme
◉ Operation & maintenance of bus bar is
easy.
◉ Maintenance and extensions of busbars
are not possible without shutdown of the
substation.
◉ Failure of bus results in shut down of
entire sub station.
56
Bus Fault ???

57. Single Bus With Sectionaliser
◉ Improves slightly the reliability if the
incoming and out going circuits are
distributed evenly on both the sections
◉ Similar to the single bus scheme except
the sectionalizing breaker or isolator.
◉ By keeping the sectionaliser open one
section can be in service and the other
can be taken for maintenance or
extension.
◉ If a bus section breaker is provided
busbar protection can detect fault on any
section and trip the breakers connected
to that section and isolate it. 57
Bus Fault ???

58. Double Main Bus Scheme
◉ Load will be distributed on both the
buses and the bus coupler shall be
normally closed.
◉ For maintenance & extension of any one
of the buses the entire load will be
transferred to the other bus.
◉ On load transfer of a circuit from one bus
to the other bus is possible through bus
isolators provided the bus coupler is
closed and thereby two buses are at the
same potential.
◉ On load bypassing of any circuit for
breaker maintenance is not possible. 58
Bus Fault ???

59. Single Main & Transfer Scheme
◉ Individual CB can be taken out for
maintenance on-load at a time (Not
Bus)
◉ The transfer bus coupler acts as the
breaker for the circuit under by pass.
◉ Individual circuits have a bypass
isolator to connect to the transfer bus
and this isolator will be closed during
bypass operation of that particular
circuit.
◉ Failure of bus or any circuit breaker
results in shut down of entire sub
station
59
Bus Fault ???

60. Double Main & Transfer Bus
Scheme
◉ In this bus scheme, in addition to the two
main buses there will be a separate
transfer bus also.
◉ Since separate transfer bus is available
there will be no need of transferring the
load from one bus to the other bus unlike
in a double main cum transfer bus
arrangement.
◉ For Maintenance or any fault occurrence
on a Bus, Particular Bus only becomes
dead, while the other Bus continues to be
in service.
60
Bus Fault ???

61. One & Half Breaker Bus Scheme
◉ It has 3 Circuit Breakers for Two Circuits.( One is Line another is
Transformer or Bus Reactor or both are Lines)
◉ No changeover of Line from one Bus to the other is required.
◉ For Circuit Breaker Maintenance of any Line, the load gets transferred
Automatically to the other bus.
◉ For Maintenance or an occurrence of a Bus fault, all the interconnections
will be on healthy bus and no disturbance to the Circuits.
◉ Even if both Buses become dead, Circuits can still be in service through
the Tie Circuit Breaker.
◉ This has got many such advantages to maintain the system stability.
61

62. 62
I Type
D Type
Bus Fault ???

63. 63
Sub-station Bays in
I Type Scheme

64. Double bus two breaker Scheme
◉ This configuration utilizes two buses and two
breakers per circuit, both buses are normally
energized and any circuit can be removed for
maintenance without an outage on the
corresponding circuit.
◉ Failure of one of the two buses will not interrupt a
circuit because all of the circuits can be fed from
the remaining bus and isolating the failed bus.
◉ Substations with the double bus double breaker
arrangement require twice the equipment as the
single bus scheme but are highly reliable.
◉ Load balancing between buses can be achieved
by shifting circuits from one bus to the other.
64

65. Mesh/Ring Bus Scheme
◉ In this scheme the breakers are arranged in a ring with circuits connected
between breakers.
◉ In normal operation, all breakers are closed. For a circuit fault, two breakers are
tripped, and in the event one of the breaker fails to operate to clear the fault, an
additional circuit will be tripped by operation of breaker- failure back up relays.
◉ During breaker maintenance, the ring is broken, but all lines remain in service.
◉ The circuits connected to the ring are arranged so that sources are alternated
with loads.
◉ Economical in cost, good reliability, safe for operation, flexible, and is normally
considered suitable for important sub stations up to a limit of five circuits.
◉ It is common practice to build major sub stations initially as a ring bus; for more
than five outgoing circuits, the ring bus is usually developed to the breaker-and-
a-half scheme. 65

66. 66

67. 67
What Indian Standard Says …
Central Electricity Authority
(Technical Standards for Construction
of Electrical Plants and Electric Lines)
Regulations, 2010
CEA : General Guidelines for 765/ 400/
220/ 132kV Sub-stations and
Switchyard for Thermal/ Hydro Power
Stations

68. 68
◉ Voltage
○ Steady State
○ Basic Impulse Level (BIL) (Lightening/switching
surge) : Breakdown
◉ Current
○ Nominal
○ Short Circuit : Heating and Melting
Voltage and Current Impact and Analysis

69. Basic Insulation Level
and Importance

70. What is BIL?
◉ The basic insulation level (BIL) is the maximum impulse voltage
that electrical equipment can withstand without damage.
◉ Insulation levels are designed to withstand surge voltages and
since the insulation lines and equipment is protected by surge
arresters draining the surges rapidly before the insulation is
damaged, the arrester must operate below the minimum
insulation level that must withstand the surges.
◉ Insulation values above this level for the lines and equipment in
the system must be so coordinated that specific protective
devices operate satisfactorily below that minimum level.
70

71. How it affects ?
◉ So breakdown of surge arrestor to
bypass the high voltage to ground
should occur at lower level and in
lower time compared to insulation
level of other equipment.
71

72. 72
Substation and Switchyards Design Parameters
Transformer and Reactor bushing and winding
Design Parameters

73. Fault Level and
Importance

74. What is Fault Level ?
◉ Fault level at any given point of the Electric Power Supply
Network is the maximum current that would flow in case of a
short circuit fault at that point.
◉ The circuit breaker should be capable of Breaking & Making
current as per their ratings & should also have Rated short time
capacity.
◉ For proper selection of circuit breaker & other switchgear
components, Knowledge of Maximum Short circuit current
during normal & abnormal conditions is necessary.
74

75. Effect of Fault Level
◉ The design of machines, bus bars, isolators, circuit breaker etc. is
based on the consideration of Normal & Short Circuit Currents.
◉ The Protective Relaying Schemes can be selected only after
ascertaining the fault levels and normal currents at various
locations.
◉ Fault calculations are also necessary for System Design, stability
considerations, selection of Layout etc.
75
Purpose of Fault level Calculation is all the above

76. 76

77. 77
PIR to be provided for CB in lines above 200 km to control switching over voltages

78. 78
Circuit Breaker

79. Other Equipment's

80. HV Equipment's
80

81. 81
Insulators

82. Other Equipment's
◉ LTAC Switchgear Panel
◉ AC Distribution Board
◉ Battery & Battery Charger
◉ DC Distribution Board
◉ Auxiliary LT Transformer
◉ Lighting Transformer
◉ Main Lighting Distribution Board
◉ Emergency Lighting Distribution Board
◉ Diesel Generator
◉ UPS
82

83. AC Distribution Box
◉ Substation AC auxiliary systems are
typically used to supply loads such as
transformer cooling, oil pumps, and
load tap changers, circuit breaker air
compressors and charging motors,
outdoor device heaters, outdoor
lighting and receptacles, motor-
operated disconnecting switches and
control house.
◉ Incoming Feeders (33/11 kV),
Transformer, Distribution Panel and
Switchover Scheme, Diesel Generator
83

84. 84
As per CEA connectivity Standard
For AC supply
◉ 220 kV and Above : Two High Tension
Supplies shall be arranged from
independent sources. One of the two
HTs shall be standby to other, In addition
an emergency supply from Diesel
generator (DG) source of suitable
capacity shall also be provided.
◉ 66 kV and below 220 kV : there shall be
one HT supply and one DG source

85. DC Supply
For DC supply :
◉ Substation of transmission for
132 kV and above and all
generating station : Two sets
of batteries each equipped
with own sets of charger
◉ Below 132 kV : One set of
battery with its own charger
85
Battery Capacity
◉ At 220 kV and above : 2 set of 220 V
(Relays and other DC requirement)
◉ At 48 V : Communication (PLCC)

86. Fire Detection, Alarm and
Protection System
◉ A comprehensive Fire detection , alarm and protection system is provided in
substation in line with relevant standards.
◉ The Transformer and reactors above 100 MVA or oil filled transformer with more
than 2000 l of oils are provided with
◉ Automatic high velocity water spray system
◉ The Transformer and reactors above 220 kV
◉ Nitrogen injection based fire protection system (NIFPS)
◉ Automatic high velocity water spray system
◉ Control room is provided with Fire Alarm system
◉ Water Hydrant system (DG, Aux Power Supply, Stores, Fire fighting pump house and
ICT/Reactors)
◉ Portable extinguishers as per Requirement. 86

87. 87
NIFPS

88. Substation Automation System
IEC-61850

89. 89
What We need ?
◉ More Automation
◉ Faster Control
◉ Coordinated Monitoring
◉ Remote Operation
◉ Reducing Error and Human Threats
◉ Reducing Restoration Time
Conventional and SAS Substation

90. 90
• Imagine : Hundreds of manufacturing plants scattered across the country, all with their own
brands of devices communicating in a wide spectrum of protocols.
• Slightly increase your imagination : Plants to function efficiently and effectively you need them
to communicate .
• However, the protocols are not interoperable
• The devices are not meant to communicate with each other natively.
• Now Think of this : Replace these manufacturing plants with substations.
• Now you have got the idea what is happening throughout the world with regards to
power transmission and distribution.
• In order to maintain power quality and reliability : Substation need to communicate with
each other.
• However, with the many protocols, much engineering work is required.
• So, there is a need of Common protocol for devices to communicate and passing of
information to device.
• This need manifested itself into IEC 61850, a common protocol that facilitates interoperability
and communications among “Intelligent Electronic Devices (IED)” in substations, which will be
essential for developments of smart grid or Virtual Heat and Power plants (VHP).
Challenge

91. One global standard instead of proprietary ones
Source : Internet
91

92. How IEC 61850 was Developed ?
Source : IEC 61850 - Communication Networks and Systems in Substations: An Overview of Computer Science presentation by ISL 92

93. What is IEC 61850 ?
◉ IEC61850 is a framework for substation automation that addresses more of what is
required for interoperability of intelligent electronic devices (IEDs) beyond just the
protocol:
○ • Standardized object models and naming conventions
○ • Standardized meaning of data
○ • Standardized services and device behavior models
○ • Self-describing devices
○ • Common configuration language
○ • Profiles for:
■ – Control/SCADA
■ – Protection messaging
■ – Transducers and I/O
93

94. Source : Alstom
94

95. 95
◉ Bays : Main Bay and Tie Bay
◉ Diameter : Constitute of Main bays and Tie bay
◉ Basically for better identification and coordination
Some Finer Aspects

96. 96
◉ Central Electricity Authority (Technical Standards for Construction of Electrical Plants and
Electric Lines) Regulations, 2010
◉ CEA : General Guidelines for 765/ 400/ 220/ 132kV Sub-stations and Switchyard for Thermal/
Hydro Power Stations
Bibliography

97. Any questions ?
You can find me at
◉ chandan@posoco.in
Thanks!
97

98. Q & A
May I have your attention ?
98