Note: Descriptions are shown in the official language in which they were submitted.
CA 02524606 2005-10-27
SEPARABLE ELECTRICAL CONNECTOR COMPONENT FOR SENDING AND
RECEIVING COMMUNICATION SIGNALS THROUGH UNDERGROUND POWER
DISTRIBUTION LINES
FIELD OF THE INVENTION
The present invention relates to electrical cable connectors, and more
particularly to an
electrical connector component which provides access to a power distribution
cable for sending
and receiving communication signals through the cable and which has standard
coupling or
interface structure that permits separable connection of the component to
existing field installed
electrical cable connectors.
BACKGROUND OF THE INVENTION
Connections in medium-voltage underground power distribution systems, such as
between cables and transformers, are generally accomplished with specially
designed separable
male and female electrical connectors, such as loadbreak connectors and
deadbreak connectors.
Loadbreak cable connectors, used in conjunction with 15, 25 and 35 kV systems,
generally
include a power cable elbow connector and a loadbreak bushing insert. The
elbow connector has
one end adapted for receiving a power cable and another end adapted for
receiving an insertion
end of the loadbreak bushing insert. The opposite end of the bushing insert,
which extends
outward from the elbow connector, may in turn be received in a bushing well of
a transformer,
for example.
Such loadbreak elbows typically comprise a conductor surrounded by a
semiconducting
layer and an insulating layer, all encased in a semiconductive outer shield.
The end of the elbow
adapted for receiving the bushing insert generally includes a conically
tapered inner surface,
which mates with a conically tapered outer surface formed on the insertion end
of the bushing
insert. When connected with a bushing insert, the conductor encased in the
elbow makes
mechanical and electrical contact with a conductor encased in the bushing
insert. The elbow
may further include a cuff at its bushing receiving end for providing an
interference fit with a
molded flange on the bushing insert. This interference fit between the elbow
cuff and the
bushing insert provides a moisture and dust seal therebetween.
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CA 02524606 2005-10-27
Power distribution service personnel, whose function is to monitor and control
such
underground power distribution systems, often need to access the cables and
connectors to
facilitate servicing and repairs. One of the first steps required in servicing
underground cable
systems is the identification (e.g., phase A or phase B) of one cable from
another as it traverses
underground from manhole to manhole. One way of identifying cables is to
inject a signal
voltage onto a cable at one location and then detect the signal on the same
cable at another
location.
However, this procedure requires de-energization of the power distribution
system,
separation of electrical connectors and installation of devices for
transmitting and receiving
tracing signals. Obviously, this conventional procedure results in undesirable
long system
outage time.
Accordingly, it would be advantageous to inject a signal voltage onto the
conductor of an
underground power distribution cable at one location and detect the signal at
another location for
communications, monitoring and control, without having to de-energize the
cable or separate the
electrical connectors. It would also be desirable to provide a component that
permits such signal
transmission and detection, which can be installed in existing field installed
connection
arrangements.
SUMMARY OF THE INVENTION
The present invention is an electrical connector component for sending and
receiving
communication signals through a power distribution line. The electrical
connector component
generally includes an internal conductor, an insulative housing surrounding
the conductor and a
signal filtering device having a medium-voltage end in electrical contact with
the internal
conductor and an opposite low-voltage terminal. The signal filtering device is
adapted to
substantially block or filter passage of power signals yet substantially
permit passage of
communication signals between the medium-voltage end and the low-voltage
terminal.
In a preferred embodiment, the signal filtering device permits passage of
substantially all
communication signals having a frequency greater than about 60 Hz, and more
preferably, the
signal filtering device permits passage of substantially all communication
signals having a
frequency in the range of about 1,000 Hz to about 1 MHz. In this regard, the
signal filtering
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device is preferably a capacitive element which presents a greater impedance
to lower frequency
power signals and a lower impedance to higher frequency communication signals.
The signal filtering device is preferably encapsulated within the insulative
housing and
the insulative housing preferably includes an access port or bore formed in a
protruding boss
portion of the insulative housing for permitting access to the low-voltage
terminal of the signal
filtering device. The insulative housing may include a radially enlarged mid-
section and a
conically tapered insertion end extending from the mid-section, wherein the
insertion end is
adapted for interference fit insertion in a mating elbow connector.
Alternatively, the insulative
housing may include a conically tapered cavity formed therein for receiving a
mating bushing
insert.
In both embodiments, the connector component further preferably includes an
internal
load resistor in electrical communication with the low-voltage terminal of the
signal filtering
device for reducing the voltage output at the low-voltage terminal. Also, the
low-voltage
terminal is preferably adapted for electrical connection with at least one of
a signal generating
device and a signal receiving device.
The present invention further involves a method for sending and receiving
communication signals through a power distribution line. The method generally
includes the
steps of providing an access point on a power distribution line without de-
energizing the power
distribution line, generating a communication signal and inputting the signal
into the power
distribution line through the access point, filtering power signals from
passing through the access
point and detecting the communication signals permitted to pass through the
access point.
The access point is preferably provided by an electrical connector component
connected
to the power distribution line. The electrical connector component includes a
signal filtering
device having a medium-voltage end in electrical communication with the power
distribution
line and an opposite low-voltage terminal. The signal filtering device blocks
passage of
substantially all power signals yet permits passage of substantially all
communication signals
between the medium-voltage end and the low-voltage terminal.
A preferred form of the electrical connector component, as well as other
embodiments,
objects, features and advantages of this invention, will be apparent from the
following detailed
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description of illustrative embodiments thereof, which is to be read in
conjunction with the
accompanying drawings.
In accordance with one aspect of the present invention, there is provided an
electrical
connector component comprising: an internal conductor; an insulative housing
surrounding
said conductor; a signal filtering device having a medium-voltage end in
electrical contact
with said internal conductor and an opposite low-voltage terminal, said signal
filtering
device being adapted to substantially block passage of power signals yet
substantially permit
passage of communication signals having a frequency in the range of about
1,000 Hz to
about 1 MHz between said medium-voltage end and said low-voltage terminal; and
a
communication signal generating/receiving device connected to said low-voltage
terminal of
said signal filtering device for inputting a low-voltage communication signal
into said signal
filtering device.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a side view of a conventional elbow connector, loadbreak bushing
insert
and bushing well of the prior art.
Figure 2 is a cross-sectional view of a conventional elbow connector of the
prior art.
Figure 3 is a cross-sectional view of a conventional loadbreak bushing insert
and
bushing well of the prior art.
Figure 4 is a schematic view of a Y-type elbow connector having an electrical
connector component of the present invention connected thereto.
Figure 5 is a schematic view of an H-type bushing insert having an electrical
connector component of the present invention connected thereto.
Figure 6 is a cross-sectional view of an electrical connector component of the
present
invention in the form of a bushing insert.
Figure 7 is a cross-sectional view of an electrical connector component of the
present
invention in the form of an elbow connector.
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DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
Referring first to Figures 1-3, conventional 200A loadbreak connectors are
illustrated. In Figure 1, a power cable elbow connector 10 is illustrated
coupled to a
loadbreak bushing insert 11, which is seated in a universal bushing well 12.
The bushing
well 12 is seated on an apparatus face plate 13. The power cable elbow
connector 10
includes a first end 14 adapted for receiving the loadbreak bushing insert 11
and has a flange
or elbow cuff surrounding the open receiving end thereof A power cable
receiving end 15
is provided at the opposite end of the power cable elbow connector 10 and a
cable 16 having
a conductive member therein extends from the power cable receiving end for
connection to
a power distribution cable (not shown).
Figure 2 is a cross-sectional view of a conventional power cable elbow
connector 10,
which includes a cable receiving end 15 having a cable 16 extending outwardly
therefrom. The
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CA 02524606 2005-10-27
other end of the power cable elbow 10 is a loadbreak bushing insert receiving
end 14 having a
probe or energized electrode 17 positioned within a central opening of the
bushing receiving end.
The probe 17 is in electrical communication with the conductive member 16 via
a connection
element 18. The power cable elbow 10 includes an electrically conductive
shield 19 formed
from a conductive peroxide-cured synthetic rubber, known and referred to in
the art as EPDM.
Within the shield 19, the power cable elbow 10 includes an insulative inner
housing 20, typically
molded from an insulative rubber or epoxy material, and within the insulative
inner housing, the
power cable elbow connector includes a conductive insert 21 which surrounds
the connection
element 18.
Figure 3 is a cross-sectional view of a conventional loadbreak bushing insert
11. The
loadbreak bushing insert 11 includes a mid-section 22 having a larger
dimension than the
remainder of the bushing insert. Extending in one direction from the mid-
section 22 is a
conically tapered upper section 24 which is inserted into the power cable
elbow connector 10.
Between the mid-section 22 and the upper section 22 is a transition shoulder
portion 23. The
transition shoulder portion 23 and the elbow cuff 14 of the elbow connector 10
provide a
moisture and dust seal through an interference fit therebetween.
Extending in the opposite direction from the mid-section 22 is a bushing well
insertion
end 25, which is adapted for insertion into a universal bushing well 12. The
loadbreak bushing
insert 11 further includes a current carrying member 26 for providing
electrical connection from
the elbow 10 to the bushing well 12 through the insert.
Turning now to Figures 4 and 5, the present invention is a separable connector
component 30a or 30b that is intended to take the place of a conventional
connector in an
existing power cable connection scenario so as to provide a safe access point
into the power line
31 without any retrofitting. Specifically, the connector component 30a and 30b
of the present
invention is provided with a standard interface making it adapted to be
connected in the field to
an existing elbow connector or an existing multiple connecting point
connector, such as a Y-
connector, T-connector or an H-connector, to establish a signal transmission
and receiving port,
while maintaining the continuity of the power line.
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In this regard, the separable connector component 30a or 30b of the present
invention
may be made similar in size and shape to a conventiona1200A bushing insert 11
(or similarly
shaped elbow insulating plug) or elbow 10, as shown in Figures 1-3, and be
adapted to
interconnect with respective 200A mating connectors. However, the present
invention is
particularly well suited for interconnection with 600A, 15kV or 25kV medium-
voltage
connectors since such connectors are typically bolted in place and the present
invention
eliminates the need to unbolt these connectors.
Thus, Figure 6 shows a 600A separable connector component 30a, according to
the
present invention, in the form of an elbow insulating plug, which has a
somewhat similar size
and shape to a conventional 200A loadbreak bushing insert 11. Thus, like a
conventional
loadbreak bushing insert, the connector component 30a includes a molded
insulative housing 32
having an enlarged mid-section 34 and enclosed within a conductive shield 35.
The connector
component 30a also has a conically tapered upper section 36 extending from the
mid-section and
having an outer surface 37 which is sized and shaped to be interference-fit
within a standard
mating connector. The connector component 30a further includes a contact or
bus bar 38
centrally disposed within the upper section 36, which is adapted to
electrically couple with a
conductor of a mating elbow connector, as would a conventional bushing insert.
Thus, the
connector component 30a shown in Figure 6 is designed for a water-tight, fully
insulated
connection with existing field-installed 600A elbow-type connectors.
However, the connector component 30a of the present invention further includes
at least
one signal filtering device 40 encapsulated within the insulative housing 32.
Preferably, the
filtering device 40 is molded within the insulative housing 32 during molding
of the housing.
Alternatively, the filtering device 40 can be pressed into the housing 32
after molding.
The filtering device 40 is on one side in electrical communication with the
bus bar 38 and
is provided on its opposite side with a low-voltage terminal 42. Electrical
contact between the
filtering device 40 and the bus bar 38 can be achieved, for example, with a
threaded rod 39. The
low-voltage terminal 42, on the opposite side, is in turn adapted to be
connected with a signal
generating/receiving device 44, as shown in Figures 4 and 5, so that a low-
voltage signal can be
input to or received from an energized power line through the connector
component 30a. In a
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CA 02524606 2005-10-27
preferred embodiment, the connector 30a includes two signal filtering devices
40 connected in
series to better distribute the voltage.
The signal filtering device 40 is preferably a conductive member in close
proximity to the
medium voltage conductor to form a capacitive element. While it has been
common practice to
form capacitors in this way, the capacitance levels produced have been
sufficient to detect the
power frequency voltage, but not a signal voltage. Thus, the connector
component of the present
invention overcomes these problems by providing a capacitive element of
sufficient value to
limit signal attenuation so it can be detected in the presence of system power
voltage.
Specifically, the capacitive element presents a greater impedance to lower
frequency
power signals and presents a lower impedance to higher frequency communication
signals. In
this manner, the capacitive signal filtering device 40 serves to substantially
filter or block signals
in the standard 50 - 60 Hz power frequency range but permit passage of signals
above 60 Hz.
Preferably, a capacitive signal filtering device 40 is selected having an
impedance value which
permits passage of communication signals in the 1000 Hz - 1 MHz frequency
range.
A suitable off-the-shelf capacitive element 40 for use in the present
invention is a large
high-voltage ceramic capacitor having a capacitance about 1900 pico farads, an
impedance of
about 2.8 mega ohms and a resistance of about 370 ohms. Such a capacitor is
sufficient to limit
signal attenuation so that a low-voltage signal can be detected in the
presence of the system
power voltage. It has been found that the DHS Series Capacitors supplied by
Murata
Manufacturing Co. (www.murata.com) are suitable for use in the present
invention.
Access to the low-voltage terminal 42 of the filtering device 40 is achieved
via a direct
access port or bore 46 formed in the insulative housing 32. The access bore 46
provides a port
for connection with a signal generating/receiving device 44 to send or detect
a low-voltage signal
through the component 30a. The access bore 46 may be similar to the type
formed in
conventional elbow connectors for cable restoration fluid injection. Moreover,
the access bore
46 is preferably formed in a protruding boss portion 47 of the insulative
housing which simulates
a voltage detection point of a conventional connector. In this manner a
standard voltage test cap,
such as Voltage Test Cap No. 200TC-1, obtainable through the Elastimold
Division of Thomas
& Betts Corp., Hackettstown, New Jersey, may be utilized as an interface
between the connector
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30a and the signal generating/receiving device 44. Connection through the port
46 can be
temporary, as it would be for cable identification, or permanent, as in the
case of communication
applications for circuit control.
A removable insulated protective cap 48 is preferably provided to seal the
direct access
bore 46 when the connector component 30a is not connected to a signal
generating/receiving
device 44. The cap 48 preferably includes a prong 50 extending into the bore
46 when the cap is
secured on the housing 32.
For additional safety, the connector component 30a further preferably includes
an internal
load resistor 52 connected to ground via a grounding wire 54. The internal
load resistor 52 may
also be integrally molded with the insulative housing 36, or it may be
subsequently installed in or
assembled to the connector component 30a. The internal load resistor 52 is
positioned in the
insulative housing 36 so as to be in electrical contact with the low-voltage
terminal 42 to reduce
the power frequency voltage output based on the selected value of the
resistor. A resistor 52
having a resistance value of between about 4,000 - 30,000 ohms is sufficient
in this regard.
Connection between the low-voltage terminal 42 and the internal load resistor
52 may be
facilitated via a connection block 56, which permits dual connection of the
terminal to the
resistor and the signal generating/receiving device 44.
As mentioned above, the connector component of the present invention can take
various
forms and be adapted for connection to connectors with various electrical
ratings. For example,
Figure 7 shows a separable connector component 30b, according to an
alternative embodiment of
the present invention, in the form of a 200A elbow-type connector. Thus, like
a conventional
elbow connector, the connector component 30b includes a molded insulative
housing 60,
typically molded from an insulative rubber or epoxy material, enclosed within
a conductive
shield 62 and having a bushing insertion end 64. The bushing insertion end 64
has an internal
conically tapered cavity 66 for receiving a mating conventional loadbreak
bushing insert. The
conically tapered cavity 66 of the connector component 30b is sized and shaped
to be
interference-fit with a mating loadbreak bushing insert or a multiple
connecting point connector,
as would a conventional elbow connector.
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Also like a conventional elbow connector, the connector component 30b includes
a
conductive member 68 connected to a probe 70 via a connection element 72. The
probe 70 is
positioned within the central opening of the bushing receiving end 64 to be
electrically connected
with a contact of a bushing insert, or a multiple connecting point connector.
Like the bushing-type connector component 30a described above, the elbow-type
connector component 30b of the present invention further includes at least one
capacitive
element 40 encapsulated within the insulative housing 20. Again, the
capacitive element 40 is
preferably molded within the insulative housing 60 during molding of the
housing. The
capacitive element 40 is in electrical communication on one side with the
conductive member 68
and is provided on its opposite side with a low-voltage terminal 42.
Electrical contact between
the capacitive element 40 and the conductive member 68 can again be achieved,
for example,
with a threaded rod 39. The low-voltage terminal 42, on the opposite side, is
in turn adapted to
be connected with a signal generating/receiving device 44, as described above.
Access to the low-voltage terminal 42 is achieved via a direct access bore 65
formed in a
protruding boss portion 67 of the insulative housing 60 and a removable
protective cap 48, as
described above, may be provided to seal the direct access bore 65 when the
connector
component 30b is not connected to a signal generating/receiving device 44.
Again, a standard
voltage test cap may be utilized as an interface between the connector
component 30b and the
signal generating/receiving device 44 to minimize shock hazards. Moreover, an
internal load
resistor 52 is also preferably provided to reduce the power frequency voltage
output of the power
line, as described above.
In use, the connector component 30a or 30b of the present invention provides a
direct
access point for inputting and receiving low-voltage communication signals via
a power
distribution line. A signal generating/receiving device 44 is simply connected
to the direct
access port 46 or 65 of a connector component 30a or 30b, already installed in
the field, to send
or receive signals via the power distribution line. As a result, the line does
not need to be de-
energized, nor do any connectors need to be disassembled.
Thus, the connector component 30a, 30b incorporating a capacitive element in a
separable connector component provides a proven safe connection method to a
utility
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distribution system for the sending and receiving of communication signals
over the power
cables. Moreover, the access to the output of the connector component 30a, 30b
is provided
through a direct access port that is insulated and sealed against water
egress. Finally, the
connector components 30a, 30b of the present invention include standard
interfaces for easy
application to existing distribution systems.
Although the illustrative embodiments of the present invention have been
described
herein with reference to the accompanying drawings, it is to be understood
that the invention is
not limited to those precise embodiments, and that various other changes and
modifications may
be effected therein by one skilled in the art without departing from the scope
or spirit of the
invention.
