CA1056309A - Power line communication system - Google Patents
Power line communication systemInfo
- Publication number
- CA1056309A CA1056309A CA265,767A CA265767A CA1056309A CA 1056309 A CA1056309 A CA 1056309A CA 265767 A CA265767 A CA 265767A CA 1056309 A CA1056309 A CA 1056309A
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- CA
- Canada
- Prior art keywords
- distribution
- communication
- messenger wire
- line
- lines
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
POWER LINE COMMUNICATION SYSTEM
ABSTRACT OF THE DISCLOSURE
A distribution power line communication system wherein communication signals are transferred between a communication terminal at a substation and communication terminals at customer locations. The communication signals are transferred between the terminals by using a two-conductor line, with one of the conductors effectively grounded and with the other of the conductors effectively isolated from ground. The conductor which is isolated from ground provides a conduction path which travels along the primary distribution line to a distribution transformer location. At this location, the conduction path is transferred lines between various distribution supports other transmission lines between various distribution transformer locations. The messenger wire is suitably isolated from ground and the conduction path is transferred to separate secondary distribution lines adjacent to the messenger wire. The final portion of the ground-isolated conduction path which directs signals to the communication terminals at the customer locations is provided by the secondary distribution lines and by the service lines extend-ing to the customer locations.
ABSTRACT OF THE DISCLOSURE
A distribution power line communication system wherein communication signals are transferred between a communication terminal at a substation and communication terminals at customer locations. The communication signals are transferred between the terminals by using a two-conductor line, with one of the conductors effectively grounded and with the other of the conductors effectively isolated from ground. The conductor which is isolated from ground provides a conduction path which travels along the primary distribution line to a distribution transformer location. At this location, the conduction path is transferred lines between various distribution supports other transmission lines between various distribution transformer locations. The messenger wire is suitably isolated from ground and the conduction path is transferred to separate secondary distribution lines adjacent to the messenger wire. The final portion of the ground-isolated conduction path which directs signals to the communication terminals at the customer locations is provided by the secondary distribution lines and by the service lines extend-ing to the customer locations.
Description
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105630g Descri~tion o~ the Prior Art:
Automated po~Jer distribution systems which perform various functions, such as remote meter reading and selective load reducing, require the use o~ a distribution power line communication system. The distribution portion of the communication system conveys information between a substation and the electrical load at the customer location. m is information must be transferred along the subtransmission or primary distributlon line, the seconda~r distribution lines, and the service lines l~hich extend to the customer locations.
Many different types of distribution power line communication systems have been described in the literature and have been used to some extent for actual communication purposes. One type of communication system transfers signals along the primary portion of the distribution system by using one of the high-voltage conductors and the common neutral return or ground conductor~ Other types o~ communi-cation systems use two of the high-voltage conductors. ~lith either method, difficulty is encountered due to power *actor correcting capacitors connected to the primary distribution line which severely attenuate the communication si~nals.
Other types of communication systems have been used, but the probelms of considerable signal attenuation and multipath propagation have not been satisfactorily solved.
The use of existing conductors located along the power distribution system is advantageous from the standpoint of providing an economical communication system. Conse~uently, it is advantageous to use a minimum amount of additional equipment or facilities to provide the carrier communication 3~ system. In addition, expensive components, such as couplers .
. .- . . . - .. .: : . - . .
1(~56309 between the primary and secondary dist~ibution lines, must be used sparingly to provide an economical communication system. Therefore, it is desirable, and it is an object o~
this invention~ to provide an economical distribution power line communication system which provides hi~h ~uality in~orma-tion transmission with a minimum o~ additional cost to the power distribution system.
SUMMARY OF THE INVENTION
mere is disclosed herein a new and use~ul arrange-ment for economically providing a suitable communication system along the distribution portion of a power transmission facllity. The communication system makes maximum use of existing facilities to reduce the cost o~ additional components required to provide the communication system. -The distribution portion of the communication system extends between a substation communication terminal and communication terminals at customer locations. The commun~cation terminal at the substation is coupled to one of the high-voltage conductors o~ the subtransmission or primary distribution line. At the location where a distri-bution trans~ormer is conn~cted to the primary distribution line, the conductor carrying the communication signal is coupled to a metallic wire which is normally used to support another type o~ transmission line, such as a telephone line.
m is metallic wire is used as one conductor o~ the portion of the communication system which conveys in~ormation across the primary portlon of the power distribution system.
; me support or messenger conductor is coupled to the secondary portion of the distribution system at positions where the messenger wire is located conveniently to the l~)S6309 secondary power distribution lines. The communication signal is transferred between the locations where the messen-ger wire is coupled to the secondary distribution lines and the customer loads by propagation along the secondary distri-bution lines and the service lines extending to the customer locations, By using the messenger wire arrangement disclosed herein, only one connection to the primary portion of the distribution line is necessary to serve several separate secondary portions of the distribution line. Thus, a signifi-cant reduction in the number of relatively expensive coupling devices used to couple the primary distribution line to the secondary distribution lines can be achieved, In additionJ
since a ma~or portion of the communication path does not extend along the entire primary distribution line, the e~fect of power ~actor correcting capacitors positioned along the primary portion of the distribution line is reduced, BRIEF DESCRIPTION OF THE DRAWING
.. .. ~
Further advantages and use of this invention will become more apparent when considered in view of the following detailed de~cription an~ drawing, in which:
Figure 1 is a schematic diagram of a communication --; system constructed according to this invention;
Figure 2 is a block diagram Or a communication system constructed according to this invention;
Figure ~ is a view illustrating the physical arrangement of a communication system constructed according to this invention;
Figure 4 is a schematic diagram illustrating an 30 arrangement for isolating a messenger wire from ground ac-:
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- - ~ .
105~3~9 cording to one embodiment of this invention; and Figure 5 is a schematic diagram illustrating an arrangement rOr isolating a messenger wire from ground according to another embodiment of this invention~
DESCE~ or ~Hr PREFERRED EMBODIMENTS
- ` Throughout the ~ollowing description, similar - reference characters refer to similar elements or members in all of the figures of the drawing.
Re~erring now to the drawing, and to Figure 1 in particular, there ls shown the distribution portion of an electrical power system which is arranged ~or the transfer of communication signals across the distribution system.
me subtransmission or primary distribution line 10 receives electrical energy ~rom the substation 12 which would normally ` be connected to a high-voltage transmission line. me dis- -tribution line 10 illustrated in this specific embodiment includes the phase conductors 14J 16 and 18, Although represented as a three-conductor three-phase line, a single phase line may be used within the contemplation of this invention.
The distribution transformers 20 and 22 are connected to the phase conductor 18 of the primary distribution line 10 and to ground. ThUSJ electrical energy may be trans~erred from the primary windings 2l~ and 26 to the secondary windings 28 and 30 of the distribution transformers 20 and 22. me secondary distribution lines 32 and 34 transfer electrical energy ~rom the distribution transformers to the customer loads 36 and 38. As illustrated in Figure 1, the secondary distribution lines 32 and 34 incluae the service lines which normally extend from a customer load to the pole on which ~, . . ~
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105630~
the distribution lines are connected. Although only two distribution transformers are illustrated in Figure 1, it is within the contemplation of this invention that more than two distribution transformers may be used with the communi-cation system o~ this invention.
The desired communication link exists betT,Jeen the communication terminal 40 which is located at the substation 12 and the communication terminals 42 and 44 which are located at the customer load locations. Normally, these communication systems are of the two-way type in which signals are generated and received by each communication terminal, In describing the path of the communication signal between the communlcation terminals in this specific embodiment, the direction ~f communication propagation will be assumed to be from the substation communication terminal 40 to the customer load communication terminals, me communication terminal 40 generates a communi-cation signal between ground potential and the phase conductor 18 by use of a signal coupler 46 which includes the coupling transformer 48 and the capacitor 50. The communication signal is propagated along the conductor 18 until it reaches the terminal 52 of the distribution transformer 20. Assuming that any power factor correcting capacitor banks are connected to the primary distribution line 10 beyond the distribution transformer 20, negligible attenuat~on of the communication signal arriving at the terminal 52 is caused by the capacitor ban~s. me communication slgnal applied to the distribution transformer 20 is coupled, through the coupling capacitor 54 and the coupling transformer 56, to the conductor 58. A
repeater or signal amplifier may also be used to transfer , .
~056309 communication signals between the terminal 52 and the con-ductor 58.
Conductor 58 is an electrical conductor which is independent of the primary or secondary distribution lines and has a high resis~ance compared to the conductors of the primary and secondary distribution lines. mus, the conductor 58 is not used for the transmission of electrical energy between the various locations ln the primary distribution ~ -system. Such a conductor may consist of the support or messenger wire which is normally used to support other transmission lines~ such as telephone lines and community antenna television cables, between conventional power line supporting structures. Figure 3, ~hich will be referred to hereinafter in more detail, illustrates the use of a messenger wire to support another transmission line between poles, me conductor 58 i5 used to provide part o~ the communication signal path between the various distribution transformers connected to the primary distrlbution line 10 The conductor 58 is coupled ~o the secondary distribution lines 32 and 34 by the coupling capacitors 60 and 62J respec-tively. At the cuætomer loads, the conductors 64 and 66 are appropriately connected to the communication terminals 42 and 44J respectively. Thus, a communication path exists bet~een the messenger wire or conductor 58 and the communica-~ tion termlnals associated with the various customer loads -~ whlch are supplied by the power distribution system.
~ Figure 2 is a block diagram o~ the arrangement `~ shown in Figure 1 with more distr~bu~ion transformers ~llu-ætrated to indicate the interconnections between the system elements~ me system substat1on 70 delivers energy to the primary distribution lines 72 and 74 and, through the distri-bution transformers "T", to the customer loads 76 and 78, Communication signals applied to the primary distribution lines 72 and 74 at the substation 70 are propagated outwardly from the substation 70 to the signal couplers 80, 82 and 84.
mese couplers may be constructed from suitable isolating components, such as the transformer 56 and capacitor 54 shown in Figure lo The location of a signal coupler is determined primarily by the continuity of the messenger wire between the various secondary distribution lines associated with the power distribution system, In general, only one signal coupler is needed for each portion of the distributlon system wherein the secondary distribution line is accesslble to the same messenger wire or conductor. merefore, di~ferin~
numbers of distribution trans~ormers and secondary distri-bution lines may be associated with a particular signal coupler. For illustrative purposes, Figure 2 indicates the use of the signal coupler 80 with the distribution trans-formers 86 and the messenger wire 88. Similarly, the signalcoupler 82 is associated with the distribution transformers 90 and the messenger wire 92, and the signal coupler 84 is associated with the distribution transformers 94 ~ld the messenger wire or conductor 96. merefore, it can be seen that communication signals are required to be propagated along the distrlbution lines 72 and 74 only as ~ar as the furthest signal coupler.
Communication signals propagated along the distribu-tion line 72 are transferred to the conductor or messenger 0 wire 88 by the signal coupler 80, By suitable coupling . . .
apparatlls, indicated ~enerally by the coupling capacitors 98, the communication signals on the messenger ~ire 88 are transferred to seconda~y distribu~ion lines~ such as the line 100, which are associated with the distribution trans-~ormers 86, The communication signal is transferred from the secondary distribution lines through service lines, such as ~he line 102, to the various customer loads 76. Thus, only one signal coupler is required between the high-vol~age primary distribution line 72 and the lower voltage components of the communication system where such components are assoc-ciated with a common messenger wire. Coupling of the communi-cation signals to the other service lines illustrated in Figure 2 is accomplished by similar apparatus, with the ma~or distinction illustrated in Figure 2 being the number of distribution transformers associated with a particular messenger wire. It is emphasized ~hat the signal path described is the path conducted by the portion of the communi-cation signal transmission system which is isolated from ground potential that is, is "above ground". me return or second conductor of the communication system is provided by the grounded conductors of the electrical power system, In addition, it may be practical in some installations to connect together two or more, messenger wires by appropriate conductors to extend the useful range of a messenger wire and reduce the number of required couplers.
Figure 3 is a view illustrating a conventional electrical power system pole arrangement wherein a messenger wire is utilized~ me pole 106 supports the cross-arm 10~ -and the insulators 110. The primary distribution line consists of the conductors 112, 114 and 116. The secondary _ g _ '~
~: . : . . . . . .
~056309 distribution line consists o~ the conductors 118, 120 and 122. The messenger wire 124 exten~s between the pole 106 and the ad~acent poles to help support the cable 126.
Couplin~ o~ the communication signal to the secon-dary distribution line conductors 118) 120 and 122 is not indicated in Figure ~. ~ormally~ this would be acco~plished at the location in the power distribution system where the secondary distribution line is connected, through a distri-bution transformer, to the primary distribution line. Also, the service lines which would be connected to the secondary distribution lines shown in Figure 3 are not illustrated in the interest of clarity.
In some installations, the messenger wire 124 is not directly connected to ground potential throughout the distribution system. Therefore, the messenger wire 124 can be used conveniently as a conductor for the "above ground"
portion o~ the communication signal path. However, when an electrical ground is desired between the messenger wlre 124 and a conductor at ground potential, such as the ground wire 1~0, a suitable isolator 132 may be provided. The isolator 132 isolates the messenger wire 124 ~rom ground potential at the carrier communication frequencies.
Figure 4 represents schematically the connection of an isolator between the messenger wire 124 and ground potential, The lsolator illustrated in Figure 4 consists o~ -an inductor 136 which has a relatively high impedance at the carrier communication frequency and a relativ~ly low impedance at the power line ~requency. Figure 5 illustrates the use ; of an inductor 1~8 and a capacitor 140 connected in parallel ; ~0 to provide isolat~on between the messenger wire 124 and - . ~, -~ - .: . - . .
glound potential. This arrangement ha~ the advanta~e that the isolator presents a relatively low impedance between the messenger ~ire 12LI and ground potential at polJer line frequen-cies, and also presents a relatively low impedance at extremely high frequencies, such as frequencies present due to lightning surges.
me carrier communication signal arrangement described herein makes novel use of existing components often found in conventional power distribution ~ystems. By 10 suitable isolation o~ the messenger wire when needed, and by ~ -using the messenger wire as a part of the "above ground"
path for the communication signal, an efficient substation to customer load communication path may be provided. In addition, the effect Or attenuation of communication signals around distribution transformers is practically eliminated.
Also, the requirement that a limited number o~ couplers are needed for connection to the high-voltage primary distri-bution line is attractive from an economic standpoint.
Slnce numerous~changes may be made in the above described apparatus, and since different embod~ments of the invention may be made without departing from the spirit thereor, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.
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r~ .v~nt~ r~l~.t~ r~ l, t~ Y',--?-~Co~ iC?t ~ a~rste~ , r~r~ .,3eciPiC^l~r, t~ c~-AlAc~r arrz,n-;e~ents ~or t e~ns~errin, cor.,^.,-lunlc-.t ~r si~-r.al~ "~e'~ eer ~r-i~r.z,ry 2.n~ secondGry ~o-Jer distribut~ or lines .
. . .
;
: , - - . - - . ~. :
.- . . . . : .
~ . ~ , .
.
105630g Descri~tion o~ the Prior Art:
Automated po~Jer distribution systems which perform various functions, such as remote meter reading and selective load reducing, require the use o~ a distribution power line communication system. The distribution portion of the communication system conveys information between a substation and the electrical load at the customer location. m is information must be transferred along the subtransmission or primary distributlon line, the seconda~r distribution lines, and the service lines l~hich extend to the customer locations.
Many different types of distribution power line communication systems have been described in the literature and have been used to some extent for actual communication purposes. One type of communication system transfers signals along the primary portion of the distribution system by using one of the high-voltage conductors and the common neutral return or ground conductor~ Other types o~ communi-cation systems use two of the high-voltage conductors. ~lith either method, difficulty is encountered due to power *actor correcting capacitors connected to the primary distribution line which severely attenuate the communication si~nals.
Other types of communication systems have been used, but the probelms of considerable signal attenuation and multipath propagation have not been satisfactorily solved.
The use of existing conductors located along the power distribution system is advantageous from the standpoint of providing an economical communication system. Conse~uently, it is advantageous to use a minimum amount of additional equipment or facilities to provide the carrier communication 3~ system. In addition, expensive components, such as couplers .
. .- . . . - .. .: : . - . .
1(~56309 between the primary and secondary dist~ibution lines, must be used sparingly to provide an economical communication system. Therefore, it is desirable, and it is an object o~
this invention~ to provide an economical distribution power line communication system which provides hi~h ~uality in~orma-tion transmission with a minimum o~ additional cost to the power distribution system.
SUMMARY OF THE INVENTION
mere is disclosed herein a new and use~ul arrange-ment for economically providing a suitable communication system along the distribution portion of a power transmission facllity. The communication system makes maximum use of existing facilities to reduce the cost o~ additional components required to provide the communication system. -The distribution portion of the communication system extends between a substation communication terminal and communication terminals at customer locations. The commun~cation terminal at the substation is coupled to one of the high-voltage conductors o~ the subtransmission or primary distribution line. At the location where a distri-bution trans~ormer is conn~cted to the primary distribution line, the conductor carrying the communication signal is coupled to a metallic wire which is normally used to support another type o~ transmission line, such as a telephone line.
m is metallic wire is used as one conductor o~ the portion of the communication system which conveys in~ormation across the primary portlon of the power distribution system.
; me support or messenger conductor is coupled to the secondary portion of the distribution system at positions where the messenger wire is located conveniently to the l~)S6309 secondary power distribution lines. The communication signal is transferred between the locations where the messen-ger wire is coupled to the secondary distribution lines and the customer loads by propagation along the secondary distri-bution lines and the service lines extending to the customer locations, By using the messenger wire arrangement disclosed herein, only one connection to the primary portion of the distribution line is necessary to serve several separate secondary portions of the distribution line. Thus, a signifi-cant reduction in the number of relatively expensive coupling devices used to couple the primary distribution line to the secondary distribution lines can be achieved, In additionJ
since a ma~or portion of the communication path does not extend along the entire primary distribution line, the e~fect of power ~actor correcting capacitors positioned along the primary portion of the distribution line is reduced, BRIEF DESCRIPTION OF THE DRAWING
.. .. ~
Further advantages and use of this invention will become more apparent when considered in view of the following detailed de~cription an~ drawing, in which:
Figure 1 is a schematic diagram of a communication --; system constructed according to this invention;
Figure 2 is a block diagram Or a communication system constructed according to this invention;
Figure ~ is a view illustrating the physical arrangement of a communication system constructed according to this invention;
Figure 4 is a schematic diagram illustrating an 30 arrangement for isolating a messenger wire from ground ac-:
.
- - ~ .
105~3~9 cording to one embodiment of this invention; and Figure 5 is a schematic diagram illustrating an arrangement rOr isolating a messenger wire from ground according to another embodiment of this invention~
DESCE~ or ~Hr PREFERRED EMBODIMENTS
- ` Throughout the ~ollowing description, similar - reference characters refer to similar elements or members in all of the figures of the drawing.
Re~erring now to the drawing, and to Figure 1 in particular, there ls shown the distribution portion of an electrical power system which is arranged ~or the transfer of communication signals across the distribution system.
me subtransmission or primary distribution line 10 receives electrical energy ~rom the substation 12 which would normally ` be connected to a high-voltage transmission line. me dis- -tribution line 10 illustrated in this specific embodiment includes the phase conductors 14J 16 and 18, Although represented as a three-conductor three-phase line, a single phase line may be used within the contemplation of this invention.
The distribution transformers 20 and 22 are connected to the phase conductor 18 of the primary distribution line 10 and to ground. ThUSJ electrical energy may be trans~erred from the primary windings 2l~ and 26 to the secondary windings 28 and 30 of the distribution transformers 20 and 22. me secondary distribution lines 32 and 34 transfer electrical energy ~rom the distribution transformers to the customer loads 36 and 38. As illustrated in Figure 1, the secondary distribution lines 32 and 34 incluae the service lines which normally extend from a customer load to the pole on which ~, . . ~
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105630~
the distribution lines are connected. Although only two distribution transformers are illustrated in Figure 1, it is within the contemplation of this invention that more than two distribution transformers may be used with the communi-cation system o~ this invention.
The desired communication link exists betT,Jeen the communication terminal 40 which is located at the substation 12 and the communication terminals 42 and 44 which are located at the customer load locations. Normally, these communication systems are of the two-way type in which signals are generated and received by each communication terminal, In describing the path of the communication signal between the communlcation terminals in this specific embodiment, the direction ~f communication propagation will be assumed to be from the substation communication terminal 40 to the customer load communication terminals, me communication terminal 40 generates a communi-cation signal between ground potential and the phase conductor 18 by use of a signal coupler 46 which includes the coupling transformer 48 and the capacitor 50. The communication signal is propagated along the conductor 18 until it reaches the terminal 52 of the distribution transformer 20. Assuming that any power factor correcting capacitor banks are connected to the primary distribution line 10 beyond the distribution transformer 20, negligible attenuat~on of the communication signal arriving at the terminal 52 is caused by the capacitor ban~s. me communication slgnal applied to the distribution transformer 20 is coupled, through the coupling capacitor 54 and the coupling transformer 56, to the conductor 58. A
repeater or signal amplifier may also be used to transfer , .
~056309 communication signals between the terminal 52 and the con-ductor 58.
Conductor 58 is an electrical conductor which is independent of the primary or secondary distribution lines and has a high resis~ance compared to the conductors of the primary and secondary distribution lines. mus, the conductor 58 is not used for the transmission of electrical energy between the various locations ln the primary distribution ~ -system. Such a conductor may consist of the support or messenger wire which is normally used to support other transmission lines~ such as telephone lines and community antenna television cables, between conventional power line supporting structures. Figure 3, ~hich will be referred to hereinafter in more detail, illustrates the use of a messenger wire to support another transmission line between poles, me conductor 58 i5 used to provide part o~ the communication signal path between the various distribution transformers connected to the primary distrlbution line 10 The conductor 58 is coupled ~o the secondary distribution lines 32 and 34 by the coupling capacitors 60 and 62J respec-tively. At the cuætomer loads, the conductors 64 and 66 are appropriately connected to the communication terminals 42 and 44J respectively. Thus, a communication path exists bet~een the messenger wire or conductor 58 and the communica-~ tion termlnals associated with the various customer loads -~ whlch are supplied by the power distribution system.
~ Figure 2 is a block diagram o~ the arrangement `~ shown in Figure 1 with more distr~bu~ion transformers ~llu-ætrated to indicate the interconnections between the system elements~ me system substat1on 70 delivers energy to the primary distribution lines 72 and 74 and, through the distri-bution transformers "T", to the customer loads 76 and 78, Communication signals applied to the primary distribution lines 72 and 74 at the substation 70 are propagated outwardly from the substation 70 to the signal couplers 80, 82 and 84.
mese couplers may be constructed from suitable isolating components, such as the transformer 56 and capacitor 54 shown in Figure lo The location of a signal coupler is determined primarily by the continuity of the messenger wire between the various secondary distribution lines associated with the power distribution system, In general, only one signal coupler is needed for each portion of the distributlon system wherein the secondary distribution line is accesslble to the same messenger wire or conductor. merefore, di~ferin~
numbers of distribution trans~ormers and secondary distri-bution lines may be associated with a particular signal coupler. For illustrative purposes, Figure 2 indicates the use of the signal coupler 80 with the distribution trans-formers 86 and the messenger wire 88. Similarly, the signalcoupler 82 is associated with the distribution transformers 90 and the messenger wire 92, and the signal coupler 84 is associated with the distribution transformers 94 ~ld the messenger wire or conductor 96. merefore, it can be seen that communication signals are required to be propagated along the distrlbution lines 72 and 74 only as ~ar as the furthest signal coupler.
Communication signals propagated along the distribu-tion line 72 are transferred to the conductor or messenger 0 wire 88 by the signal coupler 80, By suitable coupling . . .
apparatlls, indicated ~enerally by the coupling capacitors 98, the communication signals on the messenger ~ire 88 are transferred to seconda~y distribu~ion lines~ such as the line 100, which are associated with the distribution trans-~ormers 86, The communication signal is transferred from the secondary distribution lines through service lines, such as ~he line 102, to the various customer loads 76. Thus, only one signal coupler is required between the high-vol~age primary distribution line 72 and the lower voltage components of the communication system where such components are assoc-ciated with a common messenger wire. Coupling of the communi-cation signals to the other service lines illustrated in Figure 2 is accomplished by similar apparatus, with the ma~or distinction illustrated in Figure 2 being the number of distribution transformers associated with a particular messenger wire. It is emphasized ~hat the signal path described is the path conducted by the portion of the communi-cation signal transmission system which is isolated from ground potential that is, is "above ground". me return or second conductor of the communication system is provided by the grounded conductors of the electrical power system, In addition, it may be practical in some installations to connect together two or more, messenger wires by appropriate conductors to extend the useful range of a messenger wire and reduce the number of required couplers.
Figure 3 is a view illustrating a conventional electrical power system pole arrangement wherein a messenger wire is utilized~ me pole 106 supports the cross-arm 10~ -and the insulators 110. The primary distribution line consists of the conductors 112, 114 and 116. The secondary _ g _ '~
~: . : . . . . . .
~056309 distribution line consists o~ the conductors 118, 120 and 122. The messenger wire 124 exten~s between the pole 106 and the ad~acent poles to help support the cable 126.
Couplin~ o~ the communication signal to the secon-dary distribution line conductors 118) 120 and 122 is not indicated in Figure ~. ~ormally~ this would be acco~plished at the location in the power distribution system where the secondary distribution line is connected, through a distri-bution transformer, to the primary distribution line. Also, the service lines which would be connected to the secondary distribution lines shown in Figure 3 are not illustrated in the interest of clarity.
In some installations, the messenger wire 124 is not directly connected to ground potential throughout the distribution system. Therefore, the messenger wire 124 can be used conveniently as a conductor for the "above ground"
portion o~ the communication signal path. However, when an electrical ground is desired between the messenger wlre 124 and a conductor at ground potential, such as the ground wire 1~0, a suitable isolator 132 may be provided. The isolator 132 isolates the messenger wire 124 ~rom ground potential at the carrier communication frequencies.
Figure 4 represents schematically the connection of an isolator between the messenger wire 124 and ground potential, The lsolator illustrated in Figure 4 consists o~ -an inductor 136 which has a relatively high impedance at the carrier communication frequency and a relativ~ly low impedance at the power line ~requency. Figure 5 illustrates the use ; of an inductor 1~8 and a capacitor 140 connected in parallel ; ~0 to provide isolat~on between the messenger wire 124 and - . ~, -~ - .: . - . .
glound potential. This arrangement ha~ the advanta~e that the isolator presents a relatively low impedance between the messenger ~ire 12LI and ground potential at polJer line frequen-cies, and also presents a relatively low impedance at extremely high frequencies, such as frequencies present due to lightning surges.
me carrier communication signal arrangement described herein makes novel use of existing components often found in conventional power distribution ~ystems. By 10 suitable isolation o~ the messenger wire when needed, and by ~ -using the messenger wire as a part of the "above ground"
path for the communication signal, an efficient substation to customer load communication path may be provided. In addition, the effect Or attenuation of communication signals around distribution transformers is practically eliminated.
Also, the requirement that a limited number o~ couplers are needed for connection to the high-voltage primary distri-bution line is attractive from an economic standpoint.
Slnce numerous~changes may be made in the above described apparatus, and since different embod~ments of the invention may be made without departing from the spirit thereor, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.
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Claims
1. A distribution power line carrier communi-cation system transmitting carrier signals to electric customer load locations served by a distribution power line system carried on support poles, said communication system comprising:
a primary line conductor of said distribution system transmitting said carrier signals and carried by said support poles;
a plurality of secondary line conductors of said distribution system carried by predetermined ones of said support poles for connection to said customer load locations;
at least one distribution transformer connected between the primary and secondary distribution line conduc-tors;
a cable supporting messenger wire having a high resistance and being suspended between said predetermined ones of said support poles;
frequency responsive impedance means connected between said messenger wire and ground potential, said impedance means having a high impedance at the carrier sig-nal frequencies and a low impedance at the power line fre-quency;
first signal coupling circuit means connected between said primary line conductor and said messenger wire for transmitting carrier signals therebetween and around said one distribution transformer; and second signal coupling circuit means connected between said messenger wire and said plurality of secondary line conductors for transmission of said carrier signals between said messenger wire and said customer load locations.
a primary line conductor of said distribution system transmitting said carrier signals and carried by said support poles;
a plurality of secondary line conductors of said distribution system carried by predetermined ones of said support poles for connection to said customer load locations;
at least one distribution transformer connected between the primary and secondary distribution line conduc-tors;
a cable supporting messenger wire having a high resistance and being suspended between said predetermined ones of said support poles;
frequency responsive impedance means connected between said messenger wire and ground potential, said impedance means having a high impedance at the carrier sig-nal frequencies and a low impedance at the power line fre-quency;
first signal coupling circuit means connected between said primary line conductor and said messenger wire for transmitting carrier signals therebetween and around said one distribution transformer; and second signal coupling circuit means connected between said messenger wire and said plurality of secondary line conductors for transmission of said carrier signals between said messenger wire and said customer load locations.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA265,767A CA1056309A (en) | 1976-11-16 | 1976-11-16 | Power line communication system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA265,767A CA1056309A (en) | 1976-11-16 | 1976-11-16 | Power line communication system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1056309A true CA1056309A (en) | 1979-06-12 |
Family
ID=4107288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA265,767A Expired CA1056309A (en) | 1976-11-16 | 1976-11-16 | Power line communication system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1056309A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4626622A (en) * | 1983-11-15 | 1986-12-02 | Hydro-Quebec | Telephasing method and system for remotely identifying unknown phases of transmission or distribution lines within an electrical network |
-
1976
- 1976-11-16 CA CA265,767A patent/CA1056309A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4626622A (en) * | 1983-11-15 | 1986-12-02 | Hydro-Quebec | Telephasing method and system for remotely identifying unknown phases of transmission or distribution lines within an electrical network |
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