Presentation on Bus Duct

1. METAL ENCLOSED BUSDUCT

2. Metal enclosed busduct is an assembly of busbars with
associated connections, joints and insulator supports within
an earthed metal enclosure.
• Non-Segregated
• Phase Segregated
• Isolated Phase
Definition
Classification

3. • Connection between Generator and Generator
Transformer;
• Connection between Transformer and Switchgear;
• Connection between one Switchgear to another
Switchgear.
• Economical point of view: When the current rating
required is high and length is short.
Application

4. • Air is the only insulating medium between three
phases.
• Recommended up-to 660V systems with current
ratings up-to 4000A.
• Specifically use for connection between secondary side
of distribution transformer and LV switchgear.
Non-Segregated Phase Busduct

6. 6.6kV, 2000A , 40KA for 3 Sec
6.6/0.433kV
2500 KVA
6.6/0.433kV
2500 KVA
415V, 4000A, 50KA for 1 Sec
NSPB

7. • Insulated phase barriers are provided;
• On high voltage systems up-to 6.6kV with current
ratings up-to 4000A.
• Specifically use for connection between secondary side
of Power / distribution transformer and MV
switchgear, tie between MV switchgear.
Phase-Segregated Busduct

9. • Separate enclosure for each;
• On systems 11kV and higher with current ratings over
4000A.
• Specially for generator leads (current>400A), IPBDs are
recommended.
Isolated Phase Busduct

10. IPBD
Continuous Non-Continuous
• Up-to 8000A rating may be left to the manufacturers of
busduct & the selection based on availability,
optimisation of capital cost & loss evaluation.
• Current rating over 8000A, only continuous type is
recommended to minimise the inductive heating of
supporting structures etc. & associated losses.

11. Typical arrangement of continuous type of Isolated Phase Bus Duct

12. Typical discontinuous type of Isolated Phase Bus Duct

13. 6.6kV SWGR
ST-3
40/25/25 MVA
220/6.9/6.9kV
220kV Switchyard
R
SB-3A SB-3BUB-3A
220kV Switchyard
UB-3B
R
RR
UT-3
40/25/25 MVA
16.5/6.9/6.9kV
R
Generator
250 MW
16.5kV
GT-3
315 MVA
235/16.5kV
IPBD
SPBD
TO EXCT
TRAFO

14. Voltage class of the Busduct may be selected from one of the following
standard ratings and shall be at least equal to the maximum voltage
rating of the associated equipment:
0.66, 3.6, 7.2, 12, 24 and 36kV
Voltage Rating of the Busduct
Rated r.m.s. continuous current carrying capacity shall be at least equal
to the maximum current capability of the associated equipment (Which
may be higher than nominal rated current) rounded off to the nearest
higher standard current rating of the busduct.
Preferred standard current ratings are 100, 250, 400, 630, 800, 1250,
1600, 2000, 3150, 4000, 5000, 6300, 8000, 10000, 12500 and 15000A.
Continuous Current Rating

15. Rated r.m.s. short time current ratings of the busbar shall correspond to
the fault level of the system. The time shall take into consideration the
operating time of backup protective devices on the incoming side but
the duration shall not be less than 1 sec.
Momentary peak current rating shall be 2.55 times the short time r.m.s.
current rating of the busduct.
Short time Current Rating
Voltage The temperature rise of the conductor shall be as per IS-8084.
Also the temperature of the busduct shall not exceed 2500C while
carrying the specified short circuit current for 1 sec when fault occurs, at
the operating temperature.
Temperature rise

16. Busbar support insulators are enclosed, the creepage distances & height
of insulators shall be the highest feasible and shall not be less than those
for heavily polluted atmosphere as per IS:2544 & IS:5350 (Part-I)
respectively to allow for dust accumulation and moisture condensation
which can occur. Station/Post type insulator shall be used for supporting
buses in metal enclosed busduct.
Bus support Insulator
Flexible connections such as braided or laminated flexible joints for
conductors and rubber bellows for enclosures shall be used for
termination of busuct at the terminal of generator, transformer,
switchgear etc. and similar flexible connections for conductors and
metallic or rubber bellows with metallic shorting for enclosures shall be
used in the run of the busuct such that they allow for vibrations &
thermal expansion and do not impose any stress on terminal and
bushings.
Terminations

17. Busduct shall be normally natural cooled (AN). Forced cooling may be
considered beyond 10000A rating as per IS:8084.
Cooling
.
Material for Bus and Enclosure
• Bus bar shall be either of copper or aluminium
conductor.
• Copper conductor shall be of hard drawn (HD), high
conductivity conforming to IS:613.
• Aluminium conductors shall be of aluminium alloy
grade 63401WP conforming to IS:5082.

18. • Material of enclosure for segregated & non-segregated
type busduct shall be mild steel or aluminium.
• If the location where the busduct (Where mild steel
are used for enclosure ) is to be installed is having
corrosive atmosphere, it shall be galvanised after
fabrication or it shall be painted preferably with epoxy
based paint.
• For isolated phase type of busduct, the enclosure
material shall be of aluminium alloy grade 63401WP
conforming to IS:5082.

19. • Aluminium is cheaper to use than copper.
• Aluminium has les than one-third the density of
copper. Weight of aluminium bus bar only half as much
as copper bar of equal current capacity. The light
weight of aluminium is of advantage in other ways too:
for instance, it allows easier handling, transportation &
erection.
• Outstanding resistance to corrosion, thus permitting its
widespread use in electro-chemical & electroplating
process where the atmosphere is highly corrosive.
Popularity of Aluminium Busduct over copper busduct:

20. • “Self-stifling” property.
• Nevertheless, Aluminium is the cheapest Non-
magnetic metal. Hence suitable material for enclosure
also.

21. Busduct- Electrical Parameter

23. TABLE-III
BUSDUCTSUPPORTING INSULATOR & SEAL OFF BUSHING
(BASED ON IS:2544 & IS: 5350 PART I)
* Note: Not available for Seal off bushing

24. 24
Reference
• TCE Design Guide
• INDAL Aluminium Bas bar
• IS: 8084-1976 (Specification for interconnecting
busbars for AC voltage above 1kV up to and including
36kV)
• ANSI-C37-20