1. MODERN TRENDS IN POWER
TRANSMISSION SYSTEMS(6-PHASE)
SWARNANDHRA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
B.V.S.S.LAKSHMI, R.PAVANI
¾ B-TECH, ¾ B-TECH,
EEE-A EEE-A
E-MAIL: E-MAIL:
bvsslakshmi@yahoo.in hanuman.hami07@gmail.com

2. ABSTRACT: This increase in power may be
coupled with a decrease in electric
At present the usage of
and magnetic field strengths for
electricity is increasing day by
certain configurations and reduction
day.so,to fullfill the customer
in radio and audible noise levels. For
need we are going for this 3-phase
the HPO Demonstration Project, a 6-
to 6-phase conversion
technique.In this paper we are phase system was selected since it
going to explain the merits of 6- represents an optimum between the
phase transmission line over 3- proportional increase in loading and
phase transmission line. the proportional increase in surge
impedance obtained by increasing
INTRODUCTION:
the number of phases with the
The concept of six phase increase in power transfer capability.
transmission lines was introduced by
METHOD OF OBTAINING 6-Ø
Barns & Barthold during 1972. Six
SUPPLY FROM 3-Ø SUPPLY:
phase power system is a part of
multiphase power system. Due to
harmonics effect and various other
reasons Six phase systems and six
phase machines are not popular but
six phase transmission lines are
more popular due to its increased
power transfer capability by
3 [( or ) 1 . 732 ] times, maintaining the
same conductor configuration, rights
of way, better efficiency, better Phase and line voltage relations
voltage regulation, greater stability
and greater reliability.
Consider V line between Va and Vc V line Va Vc Va V1 V ph
then from fig 1.2.1
From equilateral triangle M N K

3. Since MN = KN = Vph and the line Consider 3 practical cases as
voltage follows:
Vline = VL = Vph 1) : 138 KV, 3 phase double circuit
N
Va line configuration
Vc o
60
o 60 2) :230 KV, 3ph transmission line
Vc o Va
60
o
K 60 configuration
o
60
o 60
V line = V a Vc
3) :138 KV, 6 phase transmission
M
F ig 1.2.1
line configuration
FEASIBILITY OF AN INTER
To convert the existing
CONNECTED 3-Ø OR 6-Ø 3phase double circuit line to 6phase
TRANSMISSION SYSTEM: transmission line with little
Basic feasibility of modification of the terminal
interconnected 3 phase / 6 phase equipment in the substations to
transmission system has been provide 3phase / 6phase transformer
reported for normal steady state etc., without changing the
operation, over voltages, insulation transmission towers, without
requirements, power flow etc., in additional rights of way etc,. Then
several studies. power transferred is given by
The studies reveal several
interesting features of six phase
transmission system and found to
posses better characteristics than
those of its 3-phase counter parts.
The important findings of these
studies are consolidated here for Thus from the above
ready reference. equations (2) & (3) it is clear that 6
(i) Power transfer capability : phase option not only includes less
expenditure but also improves the

4. power transfer capability to 1.732 From eq. (4) since Zs is less for 6
times i.e., 73.2 % more power can phase the surge impedance loading
be transferred. On the other hand is more for 6 phase which is an
230KV, upgraded option not only advantage.
involves more expenditure due to the
change in tower design and
increased conductor spacings, but (ii) Thermal loading :
also improves the power transfer Thermal loading follows a
capability by 1.67 times only from eq. straight line relationship with phase
(2). Thus 6 phase line will have more order. Thus if thermal loading is the
power transfer capability at reduced criterion for circuit rating, the
cost. capacity increase is proportional to
number of phases. Thus 6 phase
(i) Surge impedance loading (SIL) : systems will have more thermal
It is the power delivered by a loading which is an advantage.
transmission line to a purely
resistance load equal in value to the
surge impedance (Zs) of the line. (iii) Current unbalance :
Six phase circuits & currents
L are better balanced (due to less
Zs
C
angle i.e., 60o between any two
Since the inductance of 6 phases) compared with the 3 phase
phase line is about 90% of that of the circuits with the same conductor
3 phase double circuit line Zs is configuration. Sometimes
reduced for 6 phase line. transposition may be unnecessary
[Transposition is normally done to
reduce the unbalance between the
voltages and currents
independently].
where VR = Receiving
end line voltage

5. (iv) Electric fields :
The electric field which is electric field between the two
maximum at the conductor surface conductors will be less.
decreases with phase order whereas
the ground electric field will be more
since line voltage is equal to the
phase voltage for enhanced power.
For the same power transfer since
the line voltage can be reduced the

6. RADIO AND AUDIBLE NOISE consideration for compact
It is proved that 6 phase designs.
transmission system will have less  Effect of increased capacity on
radio & audible noise compared to the terminal equipment.
3 phase double circuit line.
CONCLUSION:
ADVANTAGES:
Six phase transmission technology
Operating in this manner offers the
provides a technique for reducing
following advantages:
physical space requirements for
 For the same power flow transmission lines while providing a
capability, the phase to phase means for increasing power transfer
voltage is reduced by √3 capacity of a new or existing
times, allowing the towers to be transmission corridor. The cost for
built smaller and more compact. constructing a new six-phase line
 For the same phase to phase versus a three phase line of the same
voltage the power flow voltage level, is not excessive,
capability could be increased by particularly if physical constraints exist.
73%. In India, the 6-phase transmission
 Magnetic fields can be reduced. system is not existing because there is
CONSIDERATIONS FOR FUTURE no technical knowledge over the
DESIGN: operation of the 6-phase systems.
Modification to accommodate
REFERENCE:
phase reconfiguration transformers
www.thousandsproject.com
and the associated switching
www.seminarproject.com
equipment will in all probability have to www.slideshare.com
be accommodate with in the confines
of an existing facility. This requires a
specialized design approach involving
substation compaction in addressing
the following:
 Space for transformers and
switching equipment including