Note: Descriptions are shown in the official language in which they were submitted.
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The present application relates to an electrical
connector and to a method of connection. In particular
it relates to an electrical connector for connecting
high frequency telecommunications signals on to an
electricity transmission or distribution network.
Such connectors may be required for use with mains
electricity distribution and/or transmission networks
(generally referred to herein as power networks). In
particular, such connectors are useful in order to
safely connect high frequency signals from a
telecommunications network on to a power network for
powerline telecommunications applications. Such
powerline telecommunications systems are described in
the applicant's co-pending published International
patent applications, numbers PCT/GB95/02023,
PCT/GB95/00894, PCT/GB95/00893, PCT/GB95/02163 and
PCT/GB97/02937. The teaching and disclosures of these
five patent applications should be referred to in
relation to the present invention and are incorporated
herein by reference.
As it is now becoming more desirable to connect
telecommunications networks to power networks so that
telecommunication signals can be transmitted along
those power networks, it becomes important to find
suitable methods for making such connections and
suitable apparatus for doing so. The power network
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environment is a particularly hostile environment for
telecommunications signals and for work generally, due
to the high voltages and currents typically involved.
The equipment which may be used on such power networks
is therefore usually highly regulated and strictly
controlled; these considerations should be taken into
account when determining how to connect to the power
network.
Particular problems arise when attempting to connect
telecommunications signals to a power network at or
near a distribution transformer point on the power
network. At a distribution transformer point,
typically, a number of polyphase electrical
distribution feeder cables are interconnected via fuse
links and bus-bar sections to a transformer secondary
and/or primary winding. However, given that such
distribution transformer points are usually (a) above
ground and (b) therefore accessible, these can
typically be some of the more convenient points at
which to access the power network for
telecommunications purposes.
The present invention aims to provide a method of
connecting a telecommunications network on to a power
network at or near such a bus-bar section, and also
aims to provide apparatus suitable for making a
connection.
Accordingly, in a first aspect, the present invention
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provides a method of coupling a telecommunications
signal to a plurality of power cables, each cable being
connected in a line to a bus-bar, the method including
the steps of selecting one of the cables located
substantially in the centre of the line and either
coupling the telecommunications signal to the selected
cable or coupling the signal to the bus-bar in the
vicinity of the selected cable. By "in the vicinity"
is preferably meant at or near the selected cable e.g.
nearer to the selected cable than to any of the other
cables connected to the bus-bar.
Where a telecommunications signal is to be connected to
a plurality of power cables, one aim is usually to
ensure a roughly equal distribution of
telecommunications signal power among the power cables.
By making the physical connection in the vicinity of
one of the central cables in the line, as proposed
above, this helps to ensure that the signal power is
approximately distributed in as equal away as possible.
Preferably, the telecoms signals have a carrier
frequency of at least 1 MHZ.
While a single phase application is possible, typically
the power cables in question will be polyphase power
cables (e.g. containing 2, 3, 4 or more phases) and
there will therefore be a plurality of bus-bars with
one bus-bar for each phase, plus probably a neutral
bus-bar. Clearly the respective phases of each cable
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will each be connected to a respective bus-bar of the
appropriate phase. As an example, if each cable is a
three phase cable (e. g. red, yellow and blue phases),
then there will be three live bus-bars (red, yellow and
blue phases) and each yellow phase of each cable will
be connected to the yellow phase bus-bar, each blue
phase of each cable to the blue phase bus-bar etc. In
such a case, the telecommunications signal will
preferably be coupled to each of the bus-bars in the
vicinity of the connections of the respective phases of
the selected cable. The telecommunications signal may
be coupled to as many or as few of the available
phases/conductors as desired in eg balanced-balanced,
balanced-unbalanced or unbalanced-unbalanced or
unbalanced-balanced modes.
If there are an odd number of cables arranged in, for
example, a line then the selected cable will preferably
be the centre cable in the line. However, if there are
an even number of cables in the line then the selected
cable may be one of the two centre cables in the line
or possibly the coupling may be made at a point e.g.
substantially centrally between the two centre cables
in the line. If the arrangement is other than in a
line then the decision of where to make the physical
coupling will be based on which location is likely to
provide the most even telecommunications signal power
distribution to the power cables - which is of course
the same consideration as applies when the power cables
are in a line.
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As mentioned above, each electricity distribution
feeder cable (and indeed each phase of each cable) may
be connected to the respective bus-bars by separate
fuse links. Such fuse links, or fuse holders, are
5 generally relatively easily removable from a system in
order that the fuses can be replaced when necessary.
However the fuse links are usually of an approved
design and so substantial modifications to that design
might necessitate further approval.
Accordingly, in a second aspect, the present invention
provide a fuse holder for use in a power network, the
holder including means for holding a fuse element,
means for connecting the fuse element to the power
network, and means for coupling a telecommunications
signal to the power network.
By incorporating means for coupling a
telecommunications signal to the power network in to
the fuse holder, a simple coupling mechanism is
provided which is relatively easy to retro-fit to
existing power networks.
Preferably, the fuse holder is of a standard approved
type, for example containing a fuse link held in place
by one or more clamps and also incorporating one or
more fixing means for fixing the fuse holder in place
on a bus-bar once the fuse holder has been inserted
into or onto the bus-bar. Preferably the means for
coupling the telecommunications signal to the power
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network includes at least one capacitive coupler (e. g.
a capacitor) and a connector means by which a
telecommunications signal cable can be connected to the
means for coupling. The means for coupling may also
include an in-line fuse.
This second aspect of the present invention may be used
in connection with the first aspect of the present
invention or alternatively may be used in systems where
the first aspect of the present invention is not used
and/or appropriate.
Embodiments of the present invention will now be
described by way of example with reference to the
accompanying drawings in which:
Figure 1 is a schematic view of a typical distribution
cable and bus-bar connection arrangement, showing how a
telecommunications signal may be coupled to the
arrangement according to the present invention.
Figure 2 is a side view of an embodiment of a fuse
holder according to the present invention.
Figure 3 is a top view of the embodiment of figure 2
along the line of arrow 3.
Figure 4 is a cross sectional view along the line 4-4
of figure 2.
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Figure 5 is a side view of the embodiment of figure 2
in the direction of arrow 5.
Figure 6 is a schematic view of the coupling means
included in the embodiment of figure 2.
Figure 7 is a schematic diagram of a polyphase to earth
RF signal interface configuration according to an
embodiment of the present invention.
Figure 8 is a schematic diagram of a phase to phase RF
signal interface configuration according to an
embodiment of the present invention.
Figure 1 shows a system of connections between a
plurality (in this case 7) distribution cables 15 and a
bus-bar system. In this case the bus-bar system
consists of four bus-bars lI-14; these are three live
phase bus-bars 11-13 (red, blue and yellow phases
respectively) and a neutral bus-bar 14. For
simplicity, no connections to the neutral bus-bar have
been shown although in practice each distribution cable
would usually have a further connection to the neutral
bus-bar.
Each distribution cable is a polyphase cable, in this
case including three phases each of which is on a
separate conductor 16, 17, 18. The respective phase
conductors of each distribution cable are each
connected to the appropriate bus-bars i.e. the red
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Chas= cond~~ctor to of th= first distriauticr. cGb7.e is
cC:~nacted tc the red phase bus-bar .1 a~d so on. =he
sewn discributior, cables 15 are arranged in a straight
lir.= and thmi= respeL:.ive connections to Lhe bus-bars
11-~,3 are sim_lar=y i.n stra_ght :sires . Each
distr i.buci on cable phs.se cor3uctcr _s corrected :.o an
appropriate bus-bsr via a fuse holder 19.
r,. ~ccard~.ng to the present invention, i.r. is desixed to
~fl make a eor~ection batwesn a tel?communicsCio:~s signal
carr~,ring canCUctor 20 and each of th a swan
distributio:~ cables. Tnis =s done by selecrir_g the
c~r~t=s.l discrib~stior~ cable 21 in trs line az
distribution cab-es ~.nd n~a~:irg the co nection between
rha te7.ecommunications signal azd the bua-ba=s aitYar
to cable 21 ox' to the b~;s-bars in the ~riC~.nity o~ the
correction between cable 21 and tha bus-baxs. In the
example shewr., th ° connection betvraan the
teletocnmurioa~ions aigna_ .s mach to eacr phase
Z4 Conductor of di6tributiori C3.ble 27. zit. the fuse holder
19 wi~ich corrects thos= phase conduc tcrs co their
respective bus-baxs. =n. .his Way the signal powex of
the ta7.ecnrrimur~icaCions =igrcal 20 is disc~ibuted
rsaso~ably eve:ly betw~an the se~ren distr:.butior. cables
~5 'S.
~igura 2 o-hows a aLIS° holder (genexa.It indi sated ,~'~'l
GCcor~inC to a:~ wspeet of the presant iwT~r.t' ar.. The
19
Fuse zo:~der ?X consists of a ma~.n bcdy moulding 23
30 whica carries a fuse link 24 held in plats by a pair of
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bolt c7.~mps 25 aid carrier assc~l.ES 50 tbetter seen
in rigors 5)- ~~=en Lhs ~use carrier is lots=e3 in
place ir~ or or. a bus-bar socket (usually after having
beer. ~usred home a . g . by rr.and) , the iu.se ::o'._der is hall
in dace by i : sul ated :bomb screws 26, ~.~hich arc
us~~ally rotated cloc'rcwisa to secure =he 'use holder .n
dace .
~"~e toss holder shown in figure 2 is~'.mod~.f;ed from a
f ...
St&ricat:."d fus° holder 5y the inclusion of a
teleconmuricat:.oas signal connector, shaWn generally as
Zi. This wll be describe3 in more dttail with
~efer2nce co figure 6.
':.5 Figures 3-5 show other views cf chn fuse holder ?2, as
ex~=wined a't~ove.
FiS~.:re 6 shows in ;note detail the t=lecomm:m~ic2tiors
swgnal eornector 27 which is inserted into tha slot ;r_
S~
2~ the fuse holder .~3', shown by a dashed line ~.n figure 2.
The conr_ector 27 co:~sists of a.n in=~~'-ared body 60 ,
ir_sids which arC CoiWa.~.ned various corn;ctor
components. ~leczriral connection is made =tom the
connector com~onen:s to tht ~use link 2~ cr holder 25
25 via a read 62 which extends out of the insulac_d bcdy
0. ~ detachable RF connection is :nave to the device
via a sa=et'y probe 64 which connects to a socket G
The p,~ signal-s are then capaci'ively :oupled 'Via one or
more capacitors (63, 65) and an optional fuse o'7 to ti:e
30 cor:nector 62. The value vF the couplir_g capac.=ox(s)
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is chosen and their safe working voltages) is
dependent upon the RF signal frequency(ies) and the
bus-bar phase to phase and/or phase to neutral and/or
earth potentials at 50/60Hz (i.e. the relatively high
5 amplitude power components) respectively.
The RF signal should be fed, via the modified fuse
links, onto the necessary phase conductors, if
appropriate with respect to neutral and/or earth, of
10 the network with the necessary safety earth(s),
matching devices (i.e. balanced to unbalanced,
unbalanced to balanced, polyphase to neutral earth etc)
and over voltage and/or surge protection devices.
Figure 7 illustrates a polyphase to earth RF signal
interface configuration. The RF communication signals
are interfaced via the unbalanced coaxial port 701 via
the resistive splitter/combiner network consisting of
resistors 702-705 each of which feed a portion of the
RF signals via the coupling capacitors 706-708 onto
each of the 3 bus-bars 710, 720 and 730 via fuse links
732-734 respectively. Also the RF signals propagate
via the main fuse links 735-737 onto the polyphase
cable 740 which is assumed to be of a clad type with a
neutral earth sheath. Cable 742, which is another
distribution cable, is also assumed to be of a similar
type.
The RF chokes (inductors)712-714 provide a low
impedance path at 50/60 Hz (i.e. at power frequencies)
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should capacitors 705-708 become short circuit thus
enabling fuse links 732-734 to fail to safety. However
the chokes 712-714 are constructed such that they have
a relatively high impedance with respect to the RF
communication signals and therefore do not attenuate
these signals.
The power transformer secondary windings 750-752 are
shown for clarity and the neutral or star point 753 is
earthed in this configuration. Each of the three major
component assemblies 760-762 may be separately housed
if required for safety reasons. Components 706-708 and
732-734 are incorporated in their respective main fuse
link housings, 735-737 as detailed in figure 2.
Figure 8 illustrates a phase to phase RF signal
interface configuration. The RF communication signals
are interfaced via the unbalanced coaxial port 801, the
balun transformer (consisting of windings 803-805 which
might typically be wound on a ferrite ring core),
capacitors 806, 807 and fuse links 808, 809 onto bus-
bars 810, 811.
Balun transformer windings 803 and 805 provide low
impedance paths to earth at 50/60 Hz should capacitors
806 and/or 807 fail to short circuit and thereby enable
fuse links 808 and/or 809 to fail to safety. The balun
transformer windings 803-805 maintain a relatively high
impedance with respect to the RF communication signals
and therefore do not attenuate these signals.
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The RF communication signals applied to bus-bars 810
and 811 are similarly linked to cable 820 via the main
fuse links 822 and 823 and similarly onto cable 821 via
main fuse links 824 and 825. The power transformer
secondary windings 830-832 are shown for clarity and
the neutral or star point 833 is earthed in this
configuration. Each of the three major component
assemblies 840, 841, 842 may be separately housed if
required for safety reasons. Components 806, 807 and
808, 809 are incorporated in their respective main fuse
link housings 822 and 823 as detailed in figure 2.
The above embodiments of the present invention have
been described by way of example only and various
alternative features or modifications from what has
been described can be made within the scope of the
invention, as will be readily apparent to persons
skilled in the art.
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