SUBSTATION LAYOUT AND ACCESSORIES
Mr. S P JAISWAL
AMIT KUMAR SINGH
HEMENDRA KUMAR RAJPUT
Part A : “SUBSTATION LAYOUT”
• Single line diagram
Substation Switchyard Accessories
Reactors and capacitors
Other Switchyard Equipments
PART B: “BUSBAR ARRANGEMENT”
Single bus system
Single bus system with bus sectionalizer
Double bus system
Double breaker bus system
One and a half breaker bus system
Main and transfer bus system
Double bus system with bypass isolator
Ring main bus system
CLASSIFICATION OF SUBSTATIONS
• Based on working
Generating substation (step up s/s)
-- a) sub transmission voltage
b) primary distribution
c) distribution substation
• Based on structure
Outdoor conventional air insulated substation (AIS)
Compressed air insulated
A lightning arrester is a device used on electrical power systems to protect
the insulation on the system from the damaging effect of lightning.
Metal oxide varistors (MOVs) have been used for power system protection since the
The typical lightning arrester also known as surge arrester has a high voltage
terminal and a ground terminal.
Current from the surge is diverted around the protected insulation in most cases
PICTURES OF SURGE DIVERTER (LIGHTNING ARRESTOR)
Capacitor Voltage Transformer (CVT), Capacitance
Coupled Voltage Transformer(CCVT)
o To step down extra high voltage signals and provide
a low voltage .
o For measurement or to operate a protective relay.
•Earth Switch is used to discharge the
voltage on the circuit to the earth for
•Earth switch is mounted on the frame
of the isolators.
•It is located for each incomer
transmission line and each side of the
LINE TRAP (WAVE TRAP)
Connected in series with the power (transmission) line.
It blocks the high frequency carrier waves (24 KHz to 500 KHz) and let
power waves (50 Hz - 60 Hz) to pass through.
It is basically an inductor of rating in Milli henry (approx 1 milli Henry
for 220 KV 1250 Amp.).
It has three main components:1. Main coil.
2. Tuning Device.
3. Lightning Arrestor.
• Disconnector or Isolator switch is
used to make sure that an electrical
circuit can be completely de-energised
for service or maintenance.
• Isolator is an off-load device.
• Types of Isolators are
1. Central rotating, horizontal swing
3. Vertical swing
4. Pantograph type
Current transformers are used for
Stepping down current for
measurement, protection and control.
Current transformers are of two types
1. Protective CT
2. Measuring CT
A Circuit breaker is an automatically operated electrical switch designed to
protect an electrical circuit from damage caused by overload or short
circuit. Its basic function is to detect a fault condition and, by interrupting
continuity, to immediately discontinue electrical flow.
All circuit breakers have common features in their operation, although
details vary substantially depending on the voltage class, current rating and
type of the circuit breaker.
Once a fault is detected, contacts within the circuit breaker must open to
interrupt the circuit.
Small circuit breakers may be manually operated; larger units
have solenoids to trip the mechanism, and electric motors to restore energy
to the springs.
Different techniques are used to extinguish the arc
: Lengthening / deflection of the arc
: Intensive cooling (in jet chambers)
: Division into partial arcs
: Zero point quenching
: Connecting capacitors in parallel with contacts in DC circuits
High-voltage breakers are broadly classified by
the medium used to extinguish the arc
Busbars receive power
from incoming circuits and
deliver power to outgoing
Power Transformers are used to step up or step down a.c.
voltages and to transfer electrical power from one voltage
level to another.
• Shunt Reactors are used for long EHV transmission lines to control voltage
during low – load period.
• Shunt reactors is also used to compensate shunt capacitance of
transmission line during low load periods.
• Usually Shunt reactors are unswitched.
Series reactors are used to
limit short – circuit current
and to limit current surges
associated with fluctuating
• Series reactors are located
at the strategic locations such
that the fault levels are
• Shunt capacitors are used for compensating reactive power of LPF.
• They are used for improving the power factor. It is also used for voltage
control during heavy lagging power factor loads.
• They are located at the receiving stations and distribution substations.
• They are switched on during heavy loads and switched off during low loads.
• Series Capacitors are used for some long EHV a.c. lines to improve power
• They located at the sending end / receiving end of the lines.
• They are provided with by pass circuit breaker and protective spark –gaps.
NEUTRAL GROUNDING EQUIPMENT
•Neutral Grounding Equipment are
Resistors and reactors.
• They are used to limit the short
circuit current during ground fault.
•They are connected between
neutral point and ground.
OTHER SWITCHYARD EQUIPMENTS
. MARSHALLING KIOSKS
. STATION EARTHING SYSTEM
. POWER CABLES
. CONTROL CABLES
. METERING, RELAY AND CONTROL PANEL
. SUPPLY SYSTEM
POWER LINE CARRIER COMMUNICATION
PLCC is mainly used for telecommunication, tele-protection and tele-monitoring
between electrical substations through power lines at high voltages, such as 110
kv, 220 kv, 400 kv.
The voice signal is converted/compressed into the 300 Hz to 4000 Hz range.
It is known as :-
Power line Digital Subscriber Line (PDSL)
power line telecom (PLT)
power line networking (PLN)
Broadband over Power Lines (BPL)
WHAT IS SCADA ?
SCADA stands for Supervisory Control And Data
It is not a full control system, but rather focuses on the
It is a purely software package that is positioned on top
of hardware to which it is interfaced. ( via Programmable
Logic Controllers(PLCs)) .
The SCADA systems are arranged to perform the following tasks.
Data Collection (Data Acquisition)
Data transmission (telemetry)
Scanning, Indication, Monitoring, Logging.
Control and indication.
Ensure sequential events.
Data presentation, display, reporting
Execution of operating, commands: on/off,raise/lower.
Network supervision, alarms and report any uncommon
change of state.
CONDUCTOR USED FOR BUSES
• All Aluminum conductor (AAC)
• All Aluminum alloy conductor (AAAC)
• Aluminum conductor with aluminum alloy reinforced
• Aluminum conductor with steel reinforced (ACSR)
SINGLE BUS SYATEM
1.Simple in Design
1.In case of bus fault or bus bar isolator fault or maintenance total
Substation is out of service.
2.In case of maintenance of transformer circuit breaker the associated
transformer has also to be shut-down. Similarly for Line also.
SINGLE BUS WITH BUS SECTIONALISER
1. One complete section can be taken out for
Maintenance without disturbing the
continuity of other section.
2. If a fault occurs on one section of the Bus,
that faulty section alone will be isolated.
It will be a little more costly with the addition of one isolator and some cases with
Circuit breaker, C.Ts and C&R panel.
DOUBLE BUS SYSTEM
: Double Bus Bar Arrangement increases the
flexibility of system.
:The arrangement does not permit breaker
maintenance with out interruption.
DOUBLE BREAKER BUS SYSTEM
There is no need of bus coupler as because
the operation is done by breakers instead of
Most expensive as it involves additional breaker,
CT Isolators etc for each circuit.
ONE AND A HALF BREAKER BUS SYSTEM
During any fault on any one of the buses, that faulty bus will be cleared
instantly without interrupting any feeders in the system since all feeders will
continue to feed from other healthy bus.
This scheme is much expensive due to investment for
MAIN AND TRANSFER BUS SYSTEM
1.First close the isolators at both side of the bus
2. Then close the bypass isolator of the feeder
which is to be transferred to transfer bus.
3. Now energized the transfer bus by closing the
bus coupler circuit breaker from remote.
4.After bus coupler breaker is closed, now the power from main bus flows to the
feeder line through its main breaker as well as bus coupler breaker viatransfer bus.
5. Now if main breaker of the feeder is switched off, total power flow will
instantaneously shift to the bus coupler breaker and hence this breaker will serve
the purpose of protection for the feeder.
6. At last the operating personnel open the isolators at both sides of the main circuit
breaker to make it isolated from rest of the live system.
DOUBLE BUS SYSTEM WITH BYPASS ISOLATOR
It permits breaker maintenance without interruption
of power which is not possible in double bus system
but it provides all the advantages of double bus
It however requires one additional isolator (bypass isolator) for each feeder
circuit and introduces slight complication in system layout.
RING BUS SYSTEM
It provides a double feed to each feeder circuit,
opening one breaker under maintenance or
otherwise does not affect supply to any feeder.
But this system has two major disadvantages.
Flexibility for breaker maintenance
Each breaker removable without disconnecting load
Only one breaker needed per branch,
Each branch connected to network by two breakers
All change-over switching done with circuit-breakers
& hence flexible.