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Design of 400/220kV
Sub-station
S.M. MUJUMDAR
General Manager
(sub-station Engineering)
27th April 2005 Jyoti Structures Ltd.,
Mumbai
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Agenda
Overview of 400kV sub-station
Design Process
Design considerations
Question / Answer
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Imp. considerations in substation design
Safety of personnel and equipment
Reliability and Security
Adherence to
Statutory obligations
I.E. rules, Environmental aspects
Electrical design considerations
Structural design considerations
Ease of maintenance Possibility to Expand
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System parameters
1000 mV
(156kV)
1000 mV
(320kV)
Radio interference voltage at 1MHZ
(for phase to earth voltage)
10.
40kA40kARated short ckt. Current for 1 sec.8.
25mm/kV25mm/kVMin. creepage distance7.
156kV320kVCorona Extinction voltage6.
Effectively earthedSystem neutral earthing5.
33Number of phases4.
50Hz50HzRated frequency3.
245kV420kVMax. operating voltage2.
220kV400kVNominal system voltage1.
220kV400kVDescriptionSr.
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System parameters Contd..
Remarks220kV400kVDescriptionSr.
(Line-ground)
(open terminals)
460kV
460kV
530kV
460kV
680kV
520kV
610kV
630kV
iii) One min. power freq.
withstand voltage (dry/wet)-- for lines
-- for CB / Isolator
-- for other equipments
1050kVpii) Switching impulse
withstand voltage (dry/wet)
1050kVp
950kVp1050kVp
1550kVp
1300kVp1425kVp
Rated insulation levels
i) Full wave impulse
withstand voltage
-- for lines
-- for reactor/ Xmer-- for other equipments
11.
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Substation Birds view
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400kV Circuit Breaker
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400kV Isolator
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400kV Current Transformer
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400kV CVT
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400kV Surge Arrester
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Shunt Reactor & NGR
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400/220 kV Auto Transformer
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400kV Bus Post Insulator
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Wave Trap
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Functions of substation equipments
To discharge lightning over voltages and
switching over voltages to earth
7. Lightning Arrester
To step-down voltages for measurement, control
& protection
6. Voltage Transformer
To step-down currents for measurement, control
& protection
5. Current Transformer
To discharge the voltage on dead lines to earth4. Earthing switch
Disconnection under no-load condition for
safety, isolation and maintenance.
3. Isolators
Automatic switching during normal or abnormal
conditions
2. Circuit Breaker
Incoming & outgoing ckts. Connected to bus-bar1. Bus-Bar
FunctionEquipment
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Functions of substation equipments Contd
Compensation of long lines.14. Series Capacitor
To step-up or step-down the voltage and
transfer power from one a.c. voltage another
a.c. voltage at the same frequency.
13. Power Transformer
To provide compensations to reactive loads of
lagging power factors
12. Shunt capacitors
To prevent high frequency signals from entering
other zones.
11. Line Trap
To provide connection between high voltage
line & PLCC equipment
10. Coupling capacitor
To limit earth fault current9. Neutral-Grounding
resistor
To control over voltages by providing reactive
power compensation
8. Shunt reactor
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Functions of Associated system in substation
3. Illumination system (lighting)
-- for switchyard
-- buildings
-- roads etc.
To protect the outdoor substation
equipment from lightning strokes.
2. Overhead earth wire
shielding or Lightning masts.
To provide an earthmat for connecting
neural points, equipment body, support
structures to earth. For safety of
personnel and for enabling earth fault
protection. To provide the path for
discharging the earth currents fromneutrals, faults, Surge Arresters,
overheads shielding wires etc. with safe
step-potential and touch potential.
1. Substation Earthing system
-- Earthmat
-- Earthing spikes
-- Earthing risers
FunctionSystem
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Contd..
To provide alarm or automatic tripping offaulty part from healthy part and also to
minimize damage to faulty equipment and
associated system.
4. Protection system-- protection relay panels
-- control cables
-- circuit breakers
-- CTs, VTs etc.
For Protective circuits, control circuits,metering circuits, communication circuits
5. Control cable
For communication, telemetry, tele-
control, power line carrier protection etc.
7. PLCC system power line
carries communication system
-- line trap
-- coupling capacitor
-- PLCC panels
To provide supply path to various
auxiliary equipment and machines.
6. Power cable
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Contd
To sense the occurrence of fire by
sensors and to initiate water spray,
to disconnect power supply to
affected region to pin-point location
of fire by indication in control room.
8. Fire Fighting system
-- Sensors, detection system
-- water spray system
-- fire prot. panels, alarm system
-- watertank and spray system
For internal and external
communication
10. Telephone, telex, microwave,
OPF
For supplying starting power,
standby power for auxiliaries
9. Auxiliary standby power system
-- diesel generator sets
-- switchgear
-- distribution system
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Basic drawings for design/construction
Single Line Diagram
General Arrangement Drawing
Electrical Plan and Section
Control Room Architectural layout
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Supporting drawings
Structural layout
Earthmat layout
Civil layout
Erection Key Diagram
Lighting Layout
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Single Line Diagram 220kV
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General arrangement layout
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Electrical layout
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Electrical Section
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Control room layout
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Control room layout
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Structural layout
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Earthmat Layout
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Civil layout
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Lighting Design
Adequate lighting is necessary for safety of working personnel and O&M
activities
Recommended value of Illumination level
Control & Relay panel area - 350 Lux (at floor level)
Test laboratory - 300 Lux
Battery room - 100 Lux
Other indoor area - 150 Lux
Switchyard - 50 Lux (main equipment)
- 20 Lux (balance Area / road @
ground level)
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Single Bus arrangement
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Single Bus System
4. Can be used only where
loads can be interrupted or
have other supply
arrangements.
3. Sectionalizing
increases flexibility
3. Bus cannot be extended
without completely de-
energizing substations
3. Simple Protection
2. Not used for large
substations.
2. Difficult to do any
maintenance
2. Simple to Operate
1. Used for
distribution
substations upto 33kV
1. Fault of bus or any
circuit breaker results in
shut-down of entire
substation
1. Low cost
RemarksDemeritsMerits
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Main & Transfer Bus
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Main & transfer busbar system
3. Fault of bus or any
circuit breaker results in
shutdown of entire
substation.
3. Potential devices may
be used on the main bus
.2. Switching is
somewhat complex
when maintaining a
breaker
2. Any breaker can be
taken out of service for
maintenance.
1. Used for 110kV
substations where cost
of duplicate bus barsystem is not justified
1. Requires one extra
breaker coupler
1. Low initial & ultimate
cost
RemarksDemeritsMerits
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Double Busbar arrangement
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Double Bus Bar Single Breaker system
5. Bus couplers failure takes
entire substation out of
service.
4. Line breaker failure takes
all circuits connected to the
bus out of service.
3. High exposure to bus fault.
2. Bus protection scheme
may cause loss of substationwhen it operates.
2. Half of the feeders
connected to each bus
1. Most widely
used for 66kV,
132kv, 220kV and
important 11kv,
6.6kV, 3.3kV
substations.
1. Extra bus-coupler circuit
breaker necessary.
1. High flexibility
RemarksDemeritsMerits
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Double Busbar with Double breaker
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Double Bus Bar Double Breaker system
4. High reliability
3. Any breaker can be
taken out of service for
maintenance.
2. Used only for veryimportant, high power,
EHV substations.
2. Would lose half ofthe circuits for breaker
fault if circuits are not
connected to both the
buses.
2. Has flexibility inpermitting feeder
circuits to be connected
to any bus
1. Not used for usual
EHV substations due to
high cost.
1. Most expensive1. Each has two
associated breakers
RemarksDemeritsMerits
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Double main & transfer
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Double main bus & transfer bus system
7. Bus fault does not remove any
feeder from the service
6. Either main bus can be taken outof service at any time for
maintenance.
5. Simple operation, no isolator
switching required
4. All switching done with breakers
3. Breaker failure on bus side
breaker removes only one ckt.From service
2. Highly reliable
1. Preferred by
some utilities for
400kV and
220kV
important
substations.
1. High cost due to
three buses
1. Most flexible in operationRemarksDemeritsMerits
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One & half breaker scheme
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One & half breaker scheme
6. Selective tripping
5. All switching by breaker.
4. Each circuit fed by twobreakers.
3. Requires 1 1/2 breaker per
feeder.
2. Preferred.2. Protection and
auto-reclosing morecomplex since
middle breaker must
be responsive to
both associated
circuits.
2. Any breaker can be removed
from maintenance withoutinterruption of load.
1. Used for 400kV
& 220kV
substations.
1. One and half
breakers per circuit,
hence higher cost
1. Flexible operation for breaker
maintenance
RemarksDemeritsMerits
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Ring Bus
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Mesh (Ring) busbar system
4. Breaker failure during fault on one
circuit causes loss of additional
circuit because of breaker failure.
3. Requires VTs on all circuits
because there is no definite voltage
reference point.
These VTs may be required in all
cases for synchronizing live line orvoltage indication
2.Auto-reclosing and protection
complex.
1. Most widely
used for very
large power
stations having
large no. ofincoming and
outgoing lines
and high power
transfer.
1. If fault occurs during bus
maintenance, ring gets separated
into two sections.
1. Busbars gave
some operational
flexibility
RemarksDemeritsMerits
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Minimum Clearances
4300 mm6400 mm3. Sectional clearance
2100 mm4200 mm
(Rod-conductor configuration)
4000 mm
(Conductor-conductor configuration)
2. Phase to phase
2100 mm3500 mm1. Phase to Earth
220kV400kV
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Clearance Diagram
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Bus Bar Design
Continuous current rating. Ampacity caculation as per IEEE:738
Short time current rating (40kA for 1 Sec.) IEC-865
Stresses in Tubular Busbar
Natural frequency of Tubular Busbar
Deflection of Tube
Cantilever strength of Post Insulator
Aeolian Vibrations
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Gantry Structure Design
ClearancesNo windMax.
(ACSR 750C/ AAAC 850C)
5.
T
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Contd..
Short Circuit Forces calculation
As per IEC : 865
Short circuit forces during short circuit
Short circuit forces after short circuit
Short circuit forces due to Pinch effect for Bundled conductor
Spacer span calculation
Factor of safety of 2.0 under normal condition and 1.5 under short
circuit condition
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spacers
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Spacer span Vs Short Ckt. forces
GRAPH OF SPACER SPAN Vs CONDUCTOR TENSION FOR
400 KV TWIN MOOSE ACSR CONDUCTOR
0.00
2000.00
4000.00
6000.00
8000.00
10000.00
12000.00
0 2 4 6 8 10 12 14
SPACER SPAN IN MTRS.
CONDUC
TOR
TENSION
PER
PHASE
INK
G.
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Earthing Design
Guiding standards IEEE 80, IS:3043, CBIP-223.
400kV & 220kV system are designed for 40kA.
Basic Objectives:
Step potential within tolerable
Touch Potential limit
Ground Resistance
Adequacy of Ground conductor for fault current
(considering corrosion)
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Touch and step potential
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Lightning Protection Ground Wire
FIG-4bFIG-4a
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Lightning Protection Lightning Mast
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