Note: Descriptions are shown in the official language in which they were submitted.
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SIGNAL COUPLER
The present invention relates to apparatus for coupling
communications equipment to a conductor or cable. In
particular, it relates to an "elbow" or "T" shaped type
coupler.
Various published patent applications of the present
applicant disclose systems whereby telecommunications
signals can be conveyed along an electricity distribution
and/or transmission network. These applications include
the following; W094/09572, W095/29536, W095/29537,
W096/07245, W098/19398, the disclosures of which are
incorporated herein by reference.
In order to safely, efficiently and cost effectively
couple communication signals onto power distribution
and/or transmission networks it becomes desirable to
consider not only the interconnecting device itself, and
its component parts (e. g. a high pass filter), but also
the ease with which such a device might be retro-fitted
to an existing energised power distribution and/or
transmission network. This becomes a more complex issue
as the distribution and/or transmission network voltage
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increases. Furthermore, the actual location of such
interface devices requires to be carefully considered in
order to permit other associated functions, such as
transformer by-pass, to be safely and cost effectively
implemented as necessary.
In some electricity distribution/transmission networks it
is desirable to provide a communications signal bypass
path so that the communication signal can be routed
around the transformer, as a transformer may act as an
attenuator for high frequency signals.
In, for example, the USA it is common for pad (ground)
mounted transformers to be used in electricity
distribution and transmission networks. The primary
windings of such transformers are often connected in a
ring and, for this purpose, each transformer is usually
provided with two primary winding connection terminals
or sockets - in figure 4 these are labelled Hla and Hlb.
The intention is that a high voltage cable may be
connected to, for example, terminal Hla and then if a
further connection onto another pad mount transformer is
required, such connection can be made via a further lead
connected to terminal Hlb. Obviously if no further
connection is required then nothing will be connected to
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terminal Hlb.
The high voltage connections to terminals Hla and Hlb are
usually madc by means of an elbow connector, as shown in
figure 6. The connector consists of a resin filled elbow
shaped package 60 protruding from one end of which is a
probe or pin 62. This probe 62 locates inside socket Hla
(for example) when connected to a transformer. Probe 62
is electrically connected via a connection 64 to a
terminal 66. Terminal 66 is connected to a high voltage
cable or conductor when in use.
The present invention aims to provide a method and
apparatus for effectively coupling conanunication signals
onto and off an existing, possibly energised,
distribution or transmission network.
Accordingly, in a first aspect, the present invention
provides a coupler including a pin for electrical
connection to a socket, the pin being adapted or arranged
so as to be suitable for connection to a socket of a
transformer, high pass filter means electrically
connected to the pin and connection means for connecting
the high pass filter means only to a high frequency
signal source. Preferably, the pin is adapted or
arranged so as to be suitable for connection to a primary
terminal of a transformer.
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Such a connector is suitable for use in situations where,
for example, terminal H1b as described above is not
otherwise in use. In this way, a high frequency
communication signal coupling may be made to the primary
winding of the transformer without any need to interrupt
the operation of the transformer or the power supply to
consumers. Furthermore, the installation of the
connection is safe and easy to do, which as will be
appreciated, is important in high voltage equipment.
However, as was explained above, the terminal Hlb (for
example) may not always be free and will not be free if
a number of transformers have been connected in a ring or
a line.
Accordingly, in a second aspect, the present invention
provides a coupler including: a pin for electrical
connection to a socket, a second socket electrically
connected to the pin and being adapted for receipt of a
second pin of a further (e.g. high/medium voltage, low
frequency) connector, high pass filter means electrically
connected to the pin and connection means connected to
the high pass filter means for receipt of a signal from
a signal source.
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In this way, the connector may be formed in a "T" shaped
package and can be interposed between a regular low
voltage connector (e.g. an elbow shaped connector as
shown in figure 6) and the input socket of, for example,
5 a transformer. Again, this allows the coupling of
communications equipment to the low voltage line in a
safe and efficient manner. In particular, if a number of
transformers are connected in a ring as described above,
then this allows one of the connectors (e.g. attached to
terminal H1b as described above) to be disconnected
without any interruption to the consumers' electricity
supply and for the "T" shaped connector then to be
connected safely.
Preferably the coupler of either of the above aspects is
arranged in a standard "elbow" or "T" shaped
configuration so as to fit standard sockets on
transformers. Preferably the coupler also includes a
fuse which may be located between the high pass filter
means and the pin. The high pass filter means may be
provided by a capacitor and also included may be a
protective balun and/or isolation transformer. The whole
connector package may be filled with a suitable
insulative resin and/or oil or other suitable insulative
medium, preferably with adequate stress relief
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capabilities.
In a further aspect, the present invention provides a
method of coupling a communication signal to an
electricity network and/or bypassing a transformer of the
network using the apparatus as described above. A signal
cable may be coupled to the signal source connector of
the coupler which in turn may be connected to an
amplifier and/or signal regenerator (could be analogue or
digital) and/or modem device, and/or remodulator. This
in turn may be connected to a further low voltage coupler
which is then connected to one or more of the terminals
of the secondary of the transformer.
Embodiments of the present invention will now be
described with reference to the accompanying drawings in
which:-
Figure 1 shows a coupler according to a first embodiment
of the present invention.
Figure 2 shows a coupler according to a second embodiment
of the present invention.
Figure 3 is a schematic circuit diagram of the coupler
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according to an embodiment of the present invention.
Figure 4 shows a typical pad mount transformer with
couplers according to embodiments of the present
invention being used.
Figure 5 is a schematic diagram of a bypass system for a
transformer according to an embodiment of the present
invention.
Figure 6 is a schematic diagram of a prior art low
voltage coupler.
Figure 1 shows a coupler according to the first
embodiment of the present invention. The coupler is
included in a typical elbow connector profile package
such as might be obtained from Elastimold (TM), for
example their 160 series. Such connectors are utilised,
particularly in the USA, to connect underground single
phase medium voltage (e.g. 13.8kv) distributor cables to
the primary connections of a pad mount transformer such
as that shown in figure 4.
The coupler includes a medium voltage probe 1 encased in
a housing 3 which has been filled with an insulative
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resin 2 and/or stress relieving rubber. The probe 1 is
connected to a fuse 4 which in turn is connected to a
medium voltage capacitor (e. g. 0.01 microfarads) which
acts as a high pass filter for the communication signals .
The capacitor 5 is connected to a balun and/or isolation
transformer 6 which provides a protective coupling for
high frequency communication signals. The transformer 6
is in turn connected to a connector 7 which may, in use,
be connected to a signal source (not shown).
As is explained above, such a coupler may be used to
couple to an unused primary winding terminal ( a . g . H1b in
figure 4) of a pad mount transformer.
Figure 2 shows a coupler according to a second embodiment
of the present invention. The coupler includes a pin 20
which, as for the embodiment of figure l, is dimensioned
so as to fit into a standard high voltage socket of e.g.
a pad mount transformer as shown in figure 4. The pin 20
is again connected to a fuse 21, capacitor 22,
balun/isolation transformer 23 and connected 24 in the
same way as the embodiment of figure 1. However, the
difference lies in the inclusion of a pin socket 25 which
is electrically connected to pin 20 and is in line with
pin 20 in the upper arm of the "T" shaped coupler
package. Socket 25 is dimensioned so as to receive a pin
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(which will be similar dimensions to pin 20) from a
standard low voltage coupler such as that shown in figure
6.
In this way, a prior art coupler such as shown in figure
6 can be "piggy-backed" onto the coupler of figure 2
which in turn is connected to a socket of a transformer.
This permits the coupler of figure 2 to be connected to
transformers such as that shown in figure 4 where both
terminals Hla and Hlb are already in use.
A schematic diagram of the electrical circuit of the
couplers of figures 1 and 2 is shown in figure 3. A fuse
link 30 is shown connected respectively to a transformer
bus bar 31 and a capacitor 32. As before, the capacitor
32 is connected to a balun and/or isolation transformer
(or other suitable transformer) 33, one winding of which
is connected to a signal source 34. The secondary
winding of the balun transformer terminates in a suitable
high frequency connector (e.g. a BNC connector) and a
safety earth bonding strap 35 is also provided.
Figure 4 illustrates a pad mount transformer as utilised
in a typical North American underground power
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distribution network. The transformer includes primary
winding terminals H1a and H1b and also secondary winding
terminals X1, X2 and X3. A medium voltage high frequency
coupler (such as the embodiment of figure 1) 40 is
5 connected to terminal Hlb and from the coupler 40 a
connection 42 may be made to high frequency communication
signal apparatus. Also shown are a number of earth
connections 44 for the various couplers and also for the
secondary winding socket X2.
Figure 5 is a schematic diagram of a transformer bypass
which could be used with, for example, the transformer of
figure 4. A "T" shaped connector 50, such as that of the
embodiment of figure 2, is "piggy-backed" with a normal
low voltage connector 52 and both of these are connected
to a primary winding terminal Hla. Communication signals
may be propagated along the cable or conductor 51 as has
been described in previous published patent applications
by the present applicant.
The communication signals may be removed from cable 51
using coupler 50 and then passed through an optional
amplifier or signal regenerator 53. The signals can then
be passed to a low voltage coupler 54 which in turn
connects the signals to one or more of the secondary
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winding terminals X1, X2 and X3. The signals are then
propagated on the low voltage network (LV).
As will be appreciated, the above embodiments are given
by way of example only and modifications will be apparent
to those skilled in the art.
