Outdoor AIS Substation Design:
MV & HV SS
1.0 Substation & Its Equipment
Introduction to Substation
A SUBSTATION
Substation : From where comes from
• According to CIGRE Green Book on Substations
• When substations were first installed, they were considered to be
associated with a single generating station; hence the name
“substations” was first used.
• In the modern network, substations play a key role in assuring
network stability and safety by providing sensing and switching
functions to detect line faults and rapidly isolate these faults to
maintain overall grid stability.
What is a substation
• According to IEEE std 605
• Substation bus systems provide the following functions:
• a) The means to allow more than one electric circuit to connect to the
substation
• b) The means for incoming and outgoing circuit termination
• c) The means for electrically interconnecting switching and other
equipment such as transformers, capacitors banks, reactors, and so
on
Functions of Substation
• According to CIGRE Green Book on Substations
• The transmission and distribution network performs three main functions:
a)
The transmission of electric power from generating stations (or other networks) to load
centers
b)
The interconnection function, which improves security of supply and allows a reduction in
generation costs
c)
The supply function, which consists of supplying the electric power to subtransmission or
distribution transformers and in some cases to customers directly, connected to the
transmission and distribution network

These Functions are achieved by different types of Substations
Functions :
• From Alstom Substation Design/Application Guide
• Substation provides interconnection of transmission circuits and
transformation between network of different voltages.
• The substation is connected to the network through overhead lines.
In some cases it may not be possible to make connection to the
substation directly by the overhead line and cable entry must be
considered.
Substation : Use
• A substation is part of a system and not an entity to itself. Normally, a
power system is designed so that the effects of an outage (caused by
the failure of a single component such as a transformer, transmission
line, or distribution line) will result in minimal interruption of service
and affect the fewest customers possible.
• Failure of one component in a system often forces a greater than
normal load to be carried by other components of the system.
• Such contingencies are normally planned for and incorporated into
design criteria.
USDA:
• There are four major types of substations.
• switchyard at a generating station
• customer substation
• system station
• distribution station
Substation type and use
• Generating substation
• The second type of substation, typically known as the customer
substation, functions as the main source of electric power supply for
one particular business customer.
• The technical requirements and the business case for this type of
facility depend highly on the customer’s requirements, more so than
on utility needs.
Parts of Substation
• Primary Equipment /system : Equipment those are is in service at
highest operating voltage of system/substation
• Secondary Equipment /system : Those are used for control (local &
remote) , protection, monitoring ,automation & measurement of
primary equipment
• Auxiliary system: Those are used for interconnection between
Primary Equipment /system and Secondary Equipment /system or
those are required to enable to operate Primary Equipment /system
and Secondary Equipment /system
Parts of Substation
• Substation generally comprises the following :
a) Switchgear
b) Power Transformers
c) Protection, Control and Monitoring of Equipment
d) Busbars and Bays
e) Reactive Power Compensation including Harmonic Filters
f) Substation Lightning Protection System
g) Substation Earthing System
Other non-major parts
• Internal & periphery roads
• Security barak
• Gates
• Control Rooms
• Fire-Fighting system
• Security Boundary Wall
• Fencing
• Gantries
• Equipment support structures
Other non-major parts
• Insulators
• Indoor & Outdoor Lighting
• Light post
• Security guard post
• Gardening , solar, diesel generators
Substation comprises three main components
• These are classified as Primary System, Secondary System and Auxiliary
Supply System.
i. Primary System
Primary system comprises all equipment which are in service at the
nominal voltage system.
i. Secondary System
• The secondary system comprises all equipments which are used for the
control, protection, measurement and monitoring of primary
equipment.
• iii) Auxiliary Supply System
AC supplies and DC supplies
• Auxiliary supply system comprises all equipment such as AC supplies and DC
supplies that enable protection, control, measurement and monitoring
equipment to operate.
• a) DC Supply and Distribution Systems – provided to ensure that a secure supply
is available at all times to power protection systems, control equipment and
initiate tripping of circuit breakers and comprise :
• Batteries – either lead acid or nickel-alkali types at ratings from tens of ampere
hours to hundreds of ampere hours at voltages of 30V, 50V, 125V and 250V
depending on the application.
• Battery Charger – usually constant voltage, current limited types with boost
charge
• facility to supply standing loads and maintain the battery fully charged whilst the
auxiliary AC supply is available.
• Distribution Board – as the name implies, provides a system of distribution,
isolation and protection for DC supplies to all equipment within the substation.
• b) LVAC Supplies – an auxiliary AC supply and distribution system
which supports the operation of the substation by providing power
for cooling fan motors, tap change motors, circuit breaker mechanism
charging systems and disconnector drives in addition to the normal
heating, lighting and domestic loads.
CIGRE Green Book on Substations
• The overall function of a substation within the network is to
transform voltages from one level to another and also to provide
switching functions to provide a connection between the sources of
energy and the ultimate consumer providing protection for the grid
and its components. In a power network, substations can be
considered to be “nodes,” enabling connection between transmission
and distribution lines and the safe connection and disconnection of
one line to another.
General functions of Components

Transmission/Distribution Line: Delivers Load towards other end
or Carries to this end

Gantry Arrangement :
a) To physically hold Circuits : Incoming or outgoing line /transformer
b) To hold Busbar circuits


Switchgear: Enable switching functions
Transformer : Enables Transformation of Voltage for suitable
purpose
General functions of Components


a)
b)
c)


Surge Arrester : Provides protection from Lighting & Switching
surge when suitably selected
Instrument Transformer: Provides Instrumentation &
Enables Monitoring functions
Enables Measuring & Metering functions
Enables Control & Protection functions
Relay : Provides Protection functions in combination of IT & CB.
Aux Transformer : Provides substation auxiliary & service power
General functions of Components
• LV Control Cable: enable instrumentation, control & protection
functions
• SAS: Provides automation of SS; works as back-bone of SCADA &
remote communication
• SCADA & Telecom device: enables remote communication for control
& monitoring
• Control Room : For operator for monitoring & operation
• Roads: for operation & maintenance access & transportation of
maintenance equipment
SLD & Layout :
• Single Line Diagram : Also called One line Diagram in the US/Canada
• It describes the switchgear , other associated components symbolic
representation and their interconnections
• It shows rating of the components also
• Layout
• It shows the location of different equipment within the substation
• It is the basis of electrical connections , all civil works and installation
& erection works
Substation Component
Grounding system
• Consists of grid mesh conductor, downward rod conductor, earth test
terminals, equipment earthing terminals
Lightning protection system
• Switchyard & Building
• For Switchyard best option is shield wire; if not possible Lightning
mast is good option
• For Building lighting rod is used
Substation Protection system
• Consists of main relays & auxiliary relay, panels
• Functions is to sense faulty condition of system and send trip
command to circuit breaker
• Takes low power current & voltage from sensing equipment CT & PT
Control & automation system & SCADA
system
• Control Mimic
• Bay control unit
• Automation PC
• Ethernet switches
• GPS clock
• Gateway PC
• Firewall : Hardware & software to block possible malware
• Ethernet & Fiber optic cable
Communication system
• Two functions
• Telecommunication & tele-protection
• Two versions/technology
• PLCCS & FOCS
• PLCCS consists of Line Trap (HV side), CVT or CCV, Line matching unit ,
PLC terminal device for processing, analyzing, rx-tx of data
• FOCS consists of Fiber optic multiplexer , fiber optic patch cables,
Optical distribution boards
DC system
• Consists of DC battery, Charger DC Distribution Board
• Typically 110V or 220V is used for power of Control , Protection &
automation system and 48V is used for power of Communication &
SCADA system
• 110V or 220V DC is non-earthed system
• 48V DC system is earthed : +ve is grounded to system earth
• Ni-Cd battery is generally used
Substation auxiliary or LV AC system
• Consists of
• 33/0.415kv or 11/0.415kV transformer
• 415V XLPE power cable
• AC distribution board
• Lighting : Indoor & outdoor
• Air condition system
AIS , GIS and MTS
• AIS : Air Insulated Switchgear ,
 Around 70% of Substations in the world are AIS
• GIS : Gas insulated switchgear ,
 SF6 is pre-dominantly used as insulating gas;
 It takes less space, have longer life span, less construction time
• MTS: Mixed Technology Switchgear
 Some switchgear are AIS and some are GIS