Electrical Engineering subject, very commonly required by all practicing engineers to understand

1. BUSDUCT & BUSBAR

2. BUSDUCTS

3. INTRODUCTION
Almost all coal , nuclear , geothermal , solar thermal
electric , as well as many natural gas power plants are
thermal.
Commercial electric utility power stations are usually
constructed on a large scale and designed for
continuous operation.
Electrical power typically uses three-phase electrical
generators to produce alternating current(AC) electric
power at a frequency of 50Hz.
High power generation requires special equipment's
to transfer from source to the load.

4. INTRODUCTION(cont.)
To transfer the power through grid intovarious sub
stations , the power needs toreach thegenerator
transformer(GT) which stepsdown the high voltage
and current.
This transit occurs with the help of bus duct / bus bar
which is capable of carrying current up to 21000A and
can be subjected to various weather conditions without
substantial losses incurred.

5. Bus ducts or bus bars are used to carry very
high current between the generator and
associated transformers, in the power
stations.
In the power stations the generator voltages vary
from 12 KV to 24 KV whereas auxiliary supply
voltages are 3.3 KV, 6.6 KV, or 12 KV.
Bus duct forms an electrical link between generator ,
transformers and associated equipment's. It is an
assembly of bus bars with associated joints
,connections and supporting insulators within a
grounded metal enclosure.

6. Bus bars are thick metal connectors, usually of
aluminium , which carry largecurrent up to 10
KA. The conductors are metal enclosed, usually
aluminium to provide safety and reliable
operation.

7. BUS DUC(cont.)
Aluminium has been used for theenclosure, as
well as it reduces the magnetic losses.
Aluminium is being used increasingly as bus bar
material, in power stations, distribution boards,
switchgear, etc. one of the main reasons for this is
that it is cheaper to use than copper and plentily
available.

8. TYPES OF BUSDUCTS
There are three types of bus ducts
Isolated phase
bus duct.
(21kv)
segregated
phase bus duct.
(12kv)
Non segregated
phase bus duct.
(6.6kv)

9. INTRODUCTION:
An IPBD most commonly used for large power generating unit and
popularly knownas generatorbusduct , servesas an interconnection
between generator and it’s associated auxiliary equipment .
Conductors are air insulated and supported in the centre of an
enclosure by strategically arranging the insulators . phase to phase
circuits are eliminated and no current is induced in the steel work,
cable pipes or other metal structures in close to proximity bus duct.
In Isolated Phase Bus duct each phase conductor is enclosed by an
individual metal housing and separated from adjacent phase
conductor housing by an air space.
Each phase conductor is mounted in an individual enclosure and is
carrying a much higher current for a given permissible temperature
hence it has a large heat dissipation as compared to segregated and
non-segregated phase bus duct.

10. ISOLATED PHASE BUS DUCT
(IPBD)

11. SEGREGATED PHASE BUS DUCT
(SPBD)
Metal enclosed bus duct in which all the phase
conductors housed in common metal enclosure and
segregated by metallic or insulated barrier between
phases.
Segregated phase bus duct is generally employed in
medium voltage systems and serves as interconnection
between the switchgear and transformer.
The segregated phase bus duct comprises of three
phase conductors running along with barrier made of
aluminium alloy.
The non-magnetic barrier provided between phase
conductor reduces forces during phase to phase faults
and also helps in reducing temperature rise.

12. SEGREGATED PHASE BUS DUCT
(SPBD)

13. NON SEGREGATED PHASE BUS DUCT
(NSPBD)
Metal enclosed bus duct in which all phase conductors
are in common metal enclosure with only air barrier
and physical separation between the phases.
NSPBD serves as an interconnection between 1.1KV
switchgear/indoor powercontrol centre (PCC)/motor
control centre(MCC) and its auxiliary transformer. It is
also used for trunking connection between two
separate switchgear/PCC/MCC, whereverapplicable.

14. NON SEGREGATED PHASE BUS DUCT
(NSPBD)

15. DIAGRAM SHOWING DIFFERENT
TYPES OF BUS DUCT
Non-Segregated Phase
Bus-Duct
Isolated Phase Bus-Duct Segregated Phase Bus-
Duct

16. DESIGN AND SELECTION CRITERIA
The bus duct provide a means for carrying high current. It
provides high system reliability. The type and rating of bus
duct shall be as per system requirement.
The design of bus duct is based on following factors.
The continuous current rating.
Maximum system voltage.
Maximum dynamic and transient forces it may be
subjected to during its life span.
The dielectric requirement of the system.
Climatic conditions.

17. SELECTION CRITERIA
The shape and size of bus duct of bus bar/enclosure is
selected considering the following aspects.
1) The currentcarrying capability.
2) The resistivity required for permissible thermal
limits.
3) Force between the different conductor in short
circuitcondition.
4) Skin effect.
5) Proximityeffect.
6) Effect of solar radiation on temperature rise.

18. BUS BAR

19.  An electrical bus bar is defined as a
conductor or a group of conductor used for
collecting electric power from the incoming
feeders and distributes them to the outgoing
feeders. In other words, it is a type of
electrical junction in which all the incoming
and outgoing electrical current meets. Thus,
the electrical bus bar collects the electric
power at one location.

20.  The bus bar system in switchyard & sub
station consists the isolator and the circuit
breaker. On the occurrence of a fault, the
circuit breaker is tripped off and the faulty
section of the bus bar is easily disconnected
from the circuit.
 The electrical bus bar is available in
rectangular, cross-sectional, round and many
other shapes. The rectangular bus bar is
mostly used in the power system. The copper
and aluminium are used for the
manufacturing of the electrical bus bar.

23.  Various types of bus bar arrangements are used in the
power system. The selection of the bus bar is depended
on the different factor likes reliability, flexibility, cost
etc. The following are the electrical considerations
governing the selection of any one particular
arrangement.
 The bus bar arrangement is simple and easy in
maintenance.
 The maintenance of the system should not affect
continuity in power flow.
 The installation of the bus bar is cheap.
 The small substation where continuity of the supply is
not essential uses the single bus bar. But in a large
substation, the additional bus bar is used in the system
so that the interruption does not occur in their supply.

24. INDOOR
Voltage in KV Phase to earth in
mm
Phase to phase in
mm
0.415 15.8 19.05
3.3 50.8 50.8
6.6 63.5 88.9
11 76.2 127.0
22 139.7 241.3
33 222.25 355.6

25. OUTDOOR
Voltage in KV Phase to earth in mm Phase to phase in mm
6.6 139.7 177.8
11 177.8 228.6
22 279.4 330.2
33 381 431.8
66 685.8 787.4
110 863.6 990.6
132 1066.8 1219.2
220 1778 2057.4

26. OUTDOOR
SWITCHYARD
Voltage in KV To ground in mm Between
section(mm)
11 2750 2500
33 3700 2800
66 4000 3000
132 4600 3500
220 5500 4500

27. OUTDOOR SWITCHYARD
Voltage in KV To ground in m
132 6.10
220 7.00
400 8.84
800 12.40

28. THANK YOU