"Dec. 22, 19742.
H. K. SCHRAGE'
'
2,306,226
HIGH VOLTAGE POWER TRANSMISSION '
Filed' Feb. 7, 1941
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Dec. 22, 1942'.
2,306,226
H. K. SCHRAGE
HIGH VOL'IH‘RGIEIw POWER TRANSMISSION
Filed Feb. 7, 1941
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Patented Dec. 22, 1942
entree stares rarest eerie
Hidde Klaas Schrage, Ennetbaden, Switzerland,
assignor to Aktiengesellschaft Brown, Boveri &
Cie., Baden, Switzerland
Application February 7, 1941, Serial No. 377,937
In Switzerland February 10, 1940
11 Claims.
This invention relates to high voltage trans
mission lines, and particularly to transmission
lines wherein disturbances arising from short
circuits are minimized.
Most interruptions in high voltage lines are
due to single phase arcing earths (insulator ?ash
overs) caused by excess voltages occurring during
lightning disturbances. If the neutral point is
earthed a single phase short circuit will occur in
(Cl. 171-87)
high voltage transmission system embodying the
principles of the invention in which the six line
conductors are fed by two three-phase systems
not interlinked together;
Figs. 7 and 8 are diagrammatic representations
of high voltage transmission systems embodying
the principles of the invention, in which the six
line conductors are fed by three non-interlinked
single-phase systems;
the system, resulting in the circuit breaker open 10
Fig. 9 is a diagrammatic representation of a
:ing and the supply being interrupted. In most
system showing how in the case of three non
.Europeanhigh voltage transmission systems the
interlinked single phase feeding systems the
neutral point is generally not directly earthed
mutual capacities of the line phases and the
but connected over an earth leakage coil to
capacities of these line phases with respect to
earth; in most cases single phase arcing earths 15 earth can be compensated by choking coils. Fig.
do not cause the circuit breaker to open because
9 corresponds to the transmission system shown
they are extinguished by the aforesaid coils. On
in Fig. 8.
the other hand if a short circuit occurs between
In the Figures 1-9 the six line conductors of
two or all three phases of the system, an inter
the transmission line are designated by
ruption in transmission cannot be prevented even 20 UVWXYZ.
if the system is provided with earth leakage coils.
It will be obvious to those skilled in the art
The object of the present invention is to pro- _ that in the voltage vector diagrams shown in
vide an improved high voltage power transmis
Figs. 2, 3, 4 and 5 the voltages between the line
sion system in which short circuits between
conductors UVWXYZ are represented by the
phases or simultaneous earths in more than one 25 distances between the corresponding points
phase line do not generally produce any short
UVWXYZ of the vector diagrams. So for in
circuit currents and therefore no tripping of the
stance in Fig. 2 showing the voltage vector dia
circuit breakers. According to the invention this
gram of the line in normal conditions the dis
is achieved by passing a six-phase current over
tance Z-—U represents the voltage between the
six line conductors which are spatially arranged 30 line conductors Z and U, the distance Z-—~W
as in a three-phase double line, this current
represents the voltage between the line con
?owing either over two three-phase systems
ductors Z and W, etc. Comparing vector diagram
Fig. 2 with Fig. 1 showing the local arrangement
which are not interlinked or over three single
phase systems which are also not interlinked.
of the phases UVWXYZ on the masts, it is seen
This arrangement can be still further improved
that in these figures the relative position of the
if the capacitive charging currents which occur
phases is essentially the same, so that vector dia
with the aforementioned short-circuits or earths
gram Fig. 2 also could represent the local ar
rangement of the line conductors. This corre
and ?ow over the points where the faults occur,
are compensated by choking coils when these
spondence between vector diagram
2 and the
40 local arrangement of the conductors has the ad
currents attain dangerous values.
The invention is explained in greater detail by
vantage that in normal working conditions the
voltage between adjacent phases is a minimum.
means of the constructional examples illustrated
diagrammatically in the accompanying drawings,
Comparing a three phase double line with a six
phase line according to the invention, the line
in which;
Fig. 1 is a diagrammatic representation of a 45 voltage to earth being the same in both cases, it
typical six conductor transmission line spatially
‘will be seen that for the three phase double line
arranged as a three-phase double line;
the voltage between adjacent phase is \/3 times
Fig. 2 is a vector diagram of the voltages of the
as high as for the six phase line.
Fig. 6 represents a high voltage transmission
six line conductors in normal conditions, when no
short circuits or earths exist;
Figs. 3, 4 and 5 are voltage vector diagrams
of the six line conductors in diiierent cases of
short-circuits between line conductors or in the
case of earths of these conductors;
Fig. 6 is a diagrammatic representation of a
50 system for which the six line conductors are fed
by two three phase systems not interlinked to
gether. The three phase power bus bars 13 feed
the low tension three phase winding t of the
power transformer which is provided with two
non-interlinked three phase high voltage wind
2,306,226
ings T1 and T2. These high voltage transformer
windings T1 and T2 constitute the two non-inter
linked three phase feeding systems mentioned be
fore. The high voltage terminals UoVoWo of the
winding T1 are connected to the line conductors
UVW through the circuit breakers ucw; in the
same way the high voltage terminals XoYoZo, of
the winding T2 are connected to the line con
ductors XYZ through the circuit breaker rye.
high voltage windings cf the transformer and
UoVoWo and XoYcZo being the ten inals of the
high voltage side of the transformer supplying
the high voltage line. The windings T1 and T2
can be located in one and the same tr nsformer.
The individual conductors of the high voltage
line are designated by UVWX'ZZ.
mal six-phase operation
are closed.
During nor
switches iwwxyz
If a fault occurs on one of the high
The purpose of the circuit breakers 11/03’ and of 10 voltage conductors which does not disappear
again of its own accord, that is if for instance
an insulator on the phase conductor U is dam
aged, then in order to be able to repair or re—
A very important advantage which exists when
place this insulator, just as in the case of a three
the neutral points of the transformer windings
phase double line, the left half of the high volt
T1 and T2 are either not connected with each
age line, that is to say the phase conductors UY Z
other at all, or when these neutral points are
must be put out of operation and the power is
only connected ?exibly over choke coils will now
then transmitted temporarily as three~phase
be explained. If in this case a conductive con
current over the phase conductors Vi X. This
nection between neighboring phases of the trans
mission line is formed, for instance a flash over 20 change over is made by opening the switches
ways and closing the switch it’. The trans
between phase V and X occurs, this does not re
former windings T1 then supply the conductors
sult in a short circuit in one of the three phase
VWX and the service is maintained temporarily
systems UVW and XYZ but only in a displace
in this manner. The change over can be made
ment of the voltages of both three phase systems
relative to each other; each of the three phase 25 without interrupting the service if ?rst the
switches says are opened, then the switch a’
systems is more or less unaffected and the trans
closed, and finally the switch
opened. With
mission of power can be continued ‘without inter
the arrangement shown in Fig.
contrary to
ruption. A short circuit between the phase con
standard three-phase double systems, a short
ductors V and X results in a voltage displacement
as shown in vector diagram Fig. 3. Between ad 30 circuit between two adjacent phases of the high
voltage line does not result in an interruption of
jacent conductors, for instance between phase
the service. If the short-circuit extinguishing
Z and V, there will be a voltage equal to
or are suppression coil or is correctly dimensioned
\/3><phase voltage, that is to say a voltage equal
a short-circuit are occurring between both
to that existing with three phase double lines in
normal service. When there is an arc between 35 phases will extinguish of its own accord. If on
the other hand a short-circuit arc occurs be
the phase conductors V and X a current flows
tween thr e adjacent phases of the high voltage
over this are which is determined on the one
line, for instance between the
VXW, then
hand by the mutual capacity of the systems
with this system of connections an interr .;:tion
UVW and XYZ and on the other hand by the
mutual voltage displacement EE’ of the neutral 40 will no longer be avoided.
It is, however, also possible to avoid an in
points of these systems. If the neutral points E
terruption in the power transmission when a
and E’ of both systems are for instance con
short-circuit occurs between three adjacent
nected with each other over a choking coil 0:
phases of the high voltage line, if the six-phase
(Figs. 3 and 6) the current in the choking coil
high voltage line is not supplied by two three
will also flow over the arc and the choking coil
phase windings but by a single three-phase wind
can be dimensioned in such a manner that the
ing with open phases which are either not inter
capacity current and the choking coil current
linked or are merely connected together by means
compensate each other so that the arc extin
of choking coils. Fig. '1 shows the diagram of
guishes of its own accord, as is the case with the
connections to be used in such a case. UoliaVtYo
earth arc in high voltage lines having earth
and W020 represent the high voltage terminals
leakage coils. A common earth leakage coil 1)
of the transformer windings T1, T2 and T3 sup~
can be provided for both systems UVW and
plying the high voltage transmission line, the
XYZ independently of the “short-circuit extin
low voltage winding not being shown. The
guishing coil” 11 by connecting the coil 2) to the
three phases of the high voltage winding ‘are not
middle of the coil a as shown in Fig. 6. The coil
interlinked. The mid-points of the
high
a then serves at the time as a potential divider
voltage transformer windings
for instance
for the connection of the earth leakage coil 2).
connected to a choking coil (1 the neutral point
By using a short circuit extinguishing coil and
N of which is earthed over the choking coil D.
an earth leakage coil it is thus possible to make
During normal operation the switches utwrye
certain that the arc is extinguished both in the
the choke coils a and b will be explained further
on.
case of an arcing earth and a short circuit be
are closed and the switches 3 open.
tween the neighboring phases of a high voltage
line.
To construct a six-phase high voltage power
transmission line according to the invention the
actual high voltage line itself does not require
any alteration and the same high voltage line
age diagram of the high voltage line in normal
The volt
design. Fig.
stored.
operation is shown in Fig. 2. If a short-circuit
occurs on the high voltage line, for instance be
tween two adjacent phases W and X a voltage
displacement such as is shown in Fig. Li will re
sult. The service can thus continue without in
terruption for a time. If the short-circuit are
as for a three-phase double line can be used.
between W and X disappears then the symmetri
The transformers, high-voltage switchgear, etc.
can be of standard three-phase or single-phase 70 cal voltage diagram shown in Fig. 2 will be re
6
shows
diagrammatically
the
fundamental system of connections for such a
six-phase power transmission arrangement, t
being the low voltage windings, of a transformer
fed by power bus bars B, T1 and T2 being the
If a short-circuit occurs between the
three phases VXW then the voltage will be dis
placed as shown in Fig. 5. Also in this case the
service can be maintained. The six-phase high
‘voltage system arranged as shown in Fi . 7 is
2,306,226
therefore to a high degree unaffected by short
circuits. Only when the short-circuit is not re
3
stricted to three neighbouring phases is an in
terruption of the service unavoidable; such a
disturbance is, however, extremely improbable.
If with the arrangement shown in Fig. 7 one
half of the high voltage line, for instance the
phases ZUY, has to be made free of voltage to
enable a rep-air to be undertaken, the service
can be maintained with three phases over the
conductors VXW. The switches u’vw and both 1O
suppress1on coil 03 is connected in delta
switches s are then closed, whilst the remaining
switches must be kept open’. This change-over
the mid-points of the three phases which are not
can also be accomplished without interrupting
interlinked; three single-phase earth leakage
the service. The switches s
are closed ?rst,
switches rye opened, switch a’ closed
and ?nally
switch it opened.
coils D are also connected to the same mid
-
points, each of the three phases being provided
During normal undisturbed operation with the
arrangement shown in Fig. 7 the three-phase
choking coil a’, and the single-phase choking coil
D are free from voltage. If two or three-phase
short-circuits of the kind shown in Figs. 4. and 5
respectively occur in the high voltage line an un
symmetrical three-phase voltage forms at the ter
minals of the three-phase choking coil 11 so that
the neutral point N of the choking coil acquires
parallel with the aforesaid charging currents, it
a voltage equal to the average voltage of the high- .
is possible to obtain practically complete com
voltage line.
pensation of the currents at the ‘fault points when
as there are only short
voltage line to earth is zero and the choking coil
D is in this case free from voltage. In most
cases, however, it will not be just a question of
claim:
1. A high voltage transmission system compris
ing six high voltage line conductors spatially ar
pure short-circuits between phases but rather a
combined arcing earth and short-circuit; that is .
ranged as a three-phase double line, at least one
to say the arc will occur simultaneously between
two or three phases and also between these phases
step-up transformer at one end of said line,
and at least one step-down transformer at the
on the one hand and the earth on the other hand.
If in the case
40"
not exceeding three.
2. A high voltage transmission system corn
prising six high voltage line conductors spatially
corresponding to the centre
of gravity of the siX points UVWXYZ, these be
45
arranged as a three-phase double line, at least
ing assumed to be of equal mass. On the other
hand if the short-circuit point V'VVX has at the
same time a short to earth the earth voltage
will be displaced to VXW. rl‘he neutral point N
(Fig. '7) has then no longer earth potential and
the choking coil D is under voltage. The three
phase are suppression coil 12 must be dimensioned
according to the mutual capacity of the six high
voltage conductors.
The single-phase earth leak- .
age coil D must be dimensioned according to the
ence of 180°.
3. A high voltage transmission system com
prising six high voltage line conductors spatially
arranged as a three-phase double line, at least
one step-up transformer at one end of said line,
and at least one step-down transformer at the
other end of said line, the high voltage windings
of said transformers being connected to said con~
ductors to provide three non-interlinked single
phase circuits having an electrical phase differ
earths as well as against short-circuits in all
cases when one, two or three adjacent phases of
ence of 120°.
the high voltage line have earths or short-circuits
or both together.
4. A high voltage transmission system com
prising six high voltage line conductors spatially
arranged as a three-phase double line, two elec
trically separated three-phase high voltage
transformer windings at each end of said line
connected to said conductors to provide two
non-interlinked three-phase circuits, and a choke
three-phase operation has been described. It is
therefore clear that at the end of the line the
order in which the switch operations have to oc
cur is the same as at the beginning of the line.
It is therefore expedient to provide means Where
75
‘2,306,226
4.
5. A high voltage transmission system- com
prising six high voltage line conductors spatially
arranged as a three-phase double line, two elec
trically
separated three-phase high voltage
transformer windings at each end of said line
connected to said conductors to provide two non
interlinked three-phase circuits, a'choke coil at
least at one end of the line connecting the neu
prising six high voltage line conductors spa
tially arranged as a three-phase doubleline,
at least one'step-up transformer at one end of
said line, at least one step-down transformer
at the other end of said line, the high voltage
windings of said transformers being connected to
said conductors to provide a plurality of non
interlinked circuits each comprising an odd num
ber of phases not exceeding three, and switch
tral points of both of said separated three-phase
means for converting said line to three-phase
ll)
transformer windings dimensioned to compen
transmission on three of said conductors.
sate the capacitive charging current at the fault
9. A high voltage transmission system com
point when a short circuit occurs between any
prising six high ~voltage line conductors spa
tially arranged as a three-phase double line,
two non-interlinked conductors of the transmis
sion line, and an earth leakage coil connected to
three electrically separated high voltage trans
the mid-point of said choke coil.
former windings at each end of said line con
6. A high voltage transmission system corn
nected to said conductors to provide three non
prising six high voltage line conductors spatially
interlinked single-phase circuits, and earth leak
arranged as a three-phase double line, three elec
age coils connected to the mid-point of each of
trically separated high voltage transformer wind
the single-phase transformer windings at least
ings at each end of said line connected to said
at one end of the line.
conductors to provide three non-interlinked sin
10. A high voltage transmission system com
gle-phase circuits, and a three-phase choke coil
prising six high voltage line conductors spa
at least at one end of the line connecting the
tially arranged as a three-phase double line,
mid-points of the three separated single-phase
three electrically separated high voltage trans
transformer windings dimensioned to compen
sate the capacitive charging currents at the fault
points when a short circuit occurs between any
nected to said conductors to provide three non
former windings at each end of said line con
interlinked single-phase circuits, and single
phase choke oils connecting the mid-points of
non-interlinked conductors of the transmission
line.
7. A high voltage transmission system com
30
prising six high voltage line conductors spatially
the three single-phase transformer‘ windings at
least at one end of the line.
electrically separated high voltage transformer
11. A high voltage transmission system com
prising six high voltage line conductors spa
tially arranged as a three-phase double line,
windings at each end of said line connected to
three electrically separated high voltage trans
said conductors to provide three non-interlinked
single-phase circuits, a three-phase choke coil
former windings at each end of said line con
nected to said conductors to provide three non
at least at one end of the line connecting the
interlinked single-phase circuits, single-phase
arranged as a threaphase double line, three
mid~points of the three separated single-phase
transformer windings dimensioned to compen~
sate the capacitive charging currents at the fault
40
choke coils connecting the mid-points of the
three single-phase transformer windings at least
at one end of the line, and earth leakage coils
points when a short circuit occurs between any
connected to the mid-point of said single-phase
non-interlinked conductors or" the transmission
transformer windings.
line, and an earth leakage coil connected to the
neutral point of said choke coil.
8. A high voltage transmission system com
HIDDE KLAAS SCHRAGE.