EHV SUBSTATION EQUIPMENTS,
SWITCHING SCHMES &
LAYOUTS
BY: S.K.Harichnagan
Selection of Transmission Voltage
Selection Criterion of Economic Voltage –
Quantum of power to be evacuated
Distance from load centre
Voltage regulation
Power loss in Transmission
Initial and operating cost
Present and future voltages in neighborhood
Economic Voltage of Power
Transmission
L KVA
E 5.5
1.6 150 E = Transmission voltage (KV) (L-L).
L = Distance of transmission line in KM
KVA=Power to be transferred
3
Substation
Transmission network is the main
connecting link between the
generating plant and load. Substation
is the nodal control point of
transmission network, having a large
influence on the quality, security and
reliability of supply.
Substation Type
Based on Insulation
Environment
Conventional Air Insulated Type.
(Out door or Indoor)
Gas Insulated type.
Outdoor Gas Insulated type.
Hybrid Type.
Substation Type
Based on Function
Generating Substation
Transmission (Grid) Substation.
Distribution Substation.
Mobile Substation.
Activities in Substation
• Transformation
• Despatching
• Supervision
• Control
• Protection
• Telecommunication
• Metering
Equipment in Substation
Primary Equipment
Power Transformation of voltages for enabling
Transformer transfer of power between circuit/ network.
Circuit Breaker Switches circuit while in service enabling
interconnection of circuits for transfer of
power between circuits, protect in system
abnormalities
Isolators Provides switching and interconnection
between circuits for providing security, safety
clearance and reliability of power supply.
Instrument Measures voltage and current signals and
Transformer (CT & stimulates control, protective and
measurement devices to perform their duties.
PT /CVT)
Bus Bar & Provides electrical connection between
Conductors circuits and networks.
Supports conductors and insulates live parts
Primary Equipment
Surge or Provides protection to all the equipment from
Lightning the stresses of internal and external surges or
lightning voltages by diverting the excess energy
Arresters
responsible for it to the ground.
Earthing System Protects the equipment and operation and
and Earth maintenance staff. Limit voltage
switches
Block Power frequency, taps carrier frequency
Line Traps and
signals required for control, protection and
Coupling communication duties.
Capacitors for
PLCC System
Capacitors Changes system parameters and improves
system capacity, power factor, voltage etc.
Shunt/ Series Change system parameters, controls excess
Secondary Equipment
Control Panels & Senses signal from the protective panels,
Synch. Panel instrument transformers and or operators to
perform switching on or off of various circuits and
devices to control, protect network element or
management of a network function.
Annunciation The signals are sensed directly from the instrument
Protection Panels transformers and monitors preset conditions,
discriminates healthiness of the circuits, decides
security level of the networks and sends signal of
warning, restoration action, control signals,
records etc.
PLCC Panels Provides switching and interconnection between
circuits / stations, panels etc. for communication of
data, voice or control and protection signals.
Meters Records voltage, current, energy, frequency, load
etc. for accounting as well as statistical information
Secondary Equipment
SCADA Supervisory Control and Data Acquisition System
Cables (Power, Provides electrical connection between primary
Control & system equipment and secondary and auxiliary
system equipment and carries signals of control
communication)
commands and protection.
Station Auxiliry
Fire Protection Detects existence of fire and operates systems to
control damage of various equipment live etc.
Structure Supports the conductor, equipment, insulators etc.
LT Power Supply Provides electrical power for operating driving various
equipment, cooling, stimulating and making functional to
many other equipment and other systems.
Air conditioning Conditions the ambient Temperature for effective operation of
and ventilation sophisticated electronic devices of secondary system and
improving performance in pollution free environment.
Lighting Provides illumination etc.
DC Battery and The essential input for functioning of the secondary system
DC power supply equipment.
Station Auxiliry
Compressed To provide compressed air for pneumatic machines
Air System
Buildings Accommodates the switchyard, Control / Protection
equipment etc.
Water supply Essential as an amenity as well as operation of fire fighting
system etc.
Civil Works Land for installation of sub-station, roads, drains, cable
trenches, buildings foundations, site surfacing etc.
Selection of Bus Switching
Scheme
PRE-REQUISITES
1) System security
2) Operational flexibility
3) Simplicity of protection
arrangements
4) Ability to limit short circuit levels
(ease of sectionalizing)
5) Maintenance – Its effect on system
security
6) Ease of extension
7) Total land area
8) cost
DESIGN GUIDELINES
OPTIONS/ALTERNATIVES
1)Single sectionalised bus
2)Main and transfer bus
3)Double(Two) Main bus
4)Double main and transfer bus
6) One & half breaker
7) Ring bus
8)Double bus, double breaker
SWITCHING ARRANGEMENT
Bus section
Bus bar
SINGLE BUS BAR ARRANGEMENT WITH SECTON BREAKER.
SWITCHING ARRANGEMENT
MAIN BUS
TRANSFER BUS
MAIN AND TRANSFER BUS ARRANGEMENT
SWITCHING ARRANGEMENT
BUS-I
BUS-II
TWO BUS ARRANGEMENT
SWITCHING ARRANGEMENT
MAIN BUS-I
MAIN BUS-II
TRANSFER BUS
TWO MAIN AND TRANSFER BUS ARRANGEMENT
SWITCHING ARRANGEMENT
BUS-I
BUS-II
ONE AND HALF BREAKER ARRANGEMENT
SWITCHING ARRANGEMENT
RING ARRANGEMENT
General Parameters
Power Frequency Voltage.
Lightning Impulse Voltage.
Switching Impulse Voltage.
Creepage Distance
Rated Continuous Current
Short Time Current
Switchyard layout
Objective:
Substation layout consists essentially in arranging
a number of switchgear components in an orderly
pattern governed by their function and rules of
spatial separation.
Pre-requisites:
1) single line diagram
2) Voltage & current rating
3) general layout plan of land
4) orientation of line evacuation
5) Type of Insulation
LAYOUT CONTD…
2) Equipment spacing
a) Ease of maintenance/removal of
equipment.
b) Equipment foundation & their
cable trenches.
c) Distance between LA and equipment
based on the protection reach of LA.
d) The spacings are generally kept in
order to achieve various clearances
LAYOUT CONTD…
3) Bus bars:
The bus bars of 400 kV switchyard are generally made up 4“ IPS
aluminum tube or Quad Moose rated for 3000 A”.
The bus bars of 220/132kV switchyard are generally made up of
3“IPS aluminum tube single / twin moose conductor”. Bus bars are
placed at right angles to the feeders for tapping the power.
4) Switchyard area.
5) Connection Level
6) Equipment Interconnection & Isolators
7) Road Layout
8) Switchyard location & approach
LAYOUT CONTD…
9) Control Room Layout
10) Lighting System
11) Cabling Philosophy
12) Metal/ Gravel Filling
13) Earthing System
14) Lightning Protection System
COMPARASON BETWEEN AIS AND GIS
SUBSTATION FOOTPRINT FOR HECTOR
192
400kV AIS
400kV GIS
Trfr 1 Trfr 2 Trfr 3 Trfr 4 SVC Trfrs
69 ~10%
275kV GIS
275kV AIS
INDOOR GIS
OUTDDOR GIS – SEISMIC AREAS
OVERHEAD STRUNG BUSBARS
LOW PROFILE SUPPORTED TUBULAR
BUSBAR SUBSTATIONS
TYPICAL TUBULAR BB BUS SECTION
BAY
THANK YOU!
DISCUSSIONS OF SCHEMES
Main and Transfer Bus Scheme
SCHEMES CONTD…
SCHEME 2
Sectionalised Double Main and Transfer Bus Scheme
DISCUSSIONS OF SCHEMES
SCHEME 3
One and Half Breaker Bus Scheme
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