WO1994005091A1 - Distribution line carrier transmission system - Google Patents

Distribution line carrier transmission system Download PDF

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Publication number
WO1994005091A1
WO1994005091A1 PCT/US1993/007883 US9307883W WO9405091A1 WO 1994005091 A1 WO1994005091 A1 WO 1994005091A1 US 9307883 W US9307883 W US 9307883W WO 9405091 A1 WO9405091 A1 WO 9405091A1
Authority
WO
WIPO (PCT)
Prior art keywords
transmission line
carrier signal
transformer
secondary winding
power distribution
Prior art date
Application number
PCT/US1993/007883
Other languages
French (fr)
Inventor
Kenneth C. Shuey
Original Assignee
Abb Power T&D Company Inc.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Abb Power T&D Company Inc. filed Critical Abb Power T&D Company Inc.
Publication of WO1994005091A1 publication Critical patent/WO1994005091A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B15/00—Suppression or limitation of noise or interference
    • H04B15/02—Reducing interference from electric apparatus by means located at or near the interfering apparatus
    • H04B15/04—Reducing interference from electric apparatus by means located at or near the interfering apparatus the interference being caused by substantially sinusoidal oscillations, e.g. in a receiver or in a tape-recorder
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/54—Systems for transmission via power distribution lines
    • H04B3/56—Circuits for coupling, blocking, or by-passing of signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0264—Arrangements for coupling to transmission lines
    • H04L25/0266—Arrangements for providing Galvanic isolation, e.g. by means of magnetic or capacitive coupling
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5404—Methods of transmitting or receiving signals via power distribution lines
    • H04B2203/5425—Methods of transmitting or receiving signals via power distribution lines improving S/N by matching impedance, noise reduction, gain control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5429—Applications for powerline communications
    • H04B2203/5433—Remote metering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5462—Systems for power line communications
    • H04B2203/5483—Systems for power line communications using coupling circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B2203/00—Indexing scheme relating to line transmission systems
    • H04B2203/54—Aspects of powerline communications not already covered by H04B3/54 and its subgroups
    • H04B2203/5462—Systems for power line communications
    • H04B2203/5491—Systems for power line communications using filtering and bypassing

Definitions

  • the present invention generally relates to power distribution systems, and more particularly relates to an improved distribution line carrier transmission system.
  • the present invention relates to a filter for increasing the injection of current from a carrier transponder to a transformer in a distribution line carrier transmission system.
  • power from a power generation substation is carried by a high voltage waveform on a transmission line; a transformer converts the power to a low voltage waveform, and the low voltage waveform is carried on a low voltage transmission line to a consumer.
  • a power meter monitors the power delivered to the consumer.
  • a carrier transponder inside or associated with the power meter has means for sending and receiving information to and from the power generation substation.
  • the present invention relates to power distribution line carrier communication technology and particularly to methods for transmitting and receiving communication signals on power distribution networks that include long secondary service wiring.
  • Distribution networks comprise various lengths of secondary wiring that typically provide an impedance sufficiently low to allow the injection of normal current levels by the transponders. Injection current (i.e. , the current injected into the secondary winding of the transformer) is critical for establishing successful communications. There are cases where the secondary impedance, due to excessive wire length and wiring practices, can present an unusually large series impedance to the transponder and keep adequate current from being injected.
  • Figure 1A depicts a prior art distribution line carrier transmission system comprising a high voltage transmission line 10 and a distribution transformer 12 having an internal leakage reactance 14 (e.g. , -jlO ohms) .
  • the transformer 12 supplies voltage over a low voltage transmission line to a transponder 18.
  • the low voltage transmission line typically presents a secondary wiring impedance 16 of approximately +jl0 ohms, the exact value depending upon the length of the transmission line.
  • the reactance values given are for a carrier frequency of 12.5 Khz.
  • the system of Figure 1A will result in 1 ampere (20 V/J20 ⁇ ) of injection current delivered from the transponder 18 to the secondary winding of the transformer 12.
  • One solution to this reduced injection current is to locate a signal repeater in the area of the transponder to pick up the reduced signal and retransmit it to the substation. This is a relatively costly solution since it requires work crews to install equipment on the high voltage primary lines. (Placing the repeater on the secondary side of the transformer would be impractical because reception would be limited to a single phase winding.
  • the injection current would be attenuated by the transformer.
  • an alternative solution is to increase the voltage generated by the transponder 18, however this is considered too expensive .
  • the secondary wiring is short and normal current is injected into the transformer but the injection current is still inadequate to get two-way communications established.
  • a primary goal of the present invention is to provide a mechanism to improve these situations by increasing the transformer injection current.
  • a further goal of the present invention is to provide a technique by which the individual transformers can be analyzed and signal improvement can be made with very low associated cost.
  • a power distribution system in accordance with the present invention comprises a high voltage transmission line, a transformer comprising a primary winding coupled to the high voltage transmission line and a secondary winding, a low voltage transmission line coupled to the secondary winding, a carrier transponder operatively coupled to the low voltage transmission line, and filter means for effecting an anti-resonant condition across the secondary winding at a predetermined carrier frequency of the carrier transponder.
  • the transformer is characterized by a leakage reactance and the filter means comprises a capacitor connected across the secondary winding and matched to the leakage reactance such that a capacitive reactance of the capacitor combines with the leakage reactance to produce the anti-resonant condition.
  • the capacitive reactance in preferred embodiments appears as less than approximately 20 ohms (20 ⁇ ) (e.g., approximately five to ten ohms (5-10 ⁇ ) ) to a 5-20 KHz (e.g., 12.5 KHz) carrier signal.
  • the present invention also encompasses power distribution systems comprising a first transmission line; a transformer comprising a primary winding coupled to the first transmission line and a secondary winding, the transformer characterized by a leakage reactance associated with the secondary winding; a second transmission line coupled to the secondary winding; and a capacitor coupled across the secondary winding and presenting a capacitive reactance that matches the leakage reactance.
  • An anti- resonant condition is effected for a carrier signal oscillating on the second transmission line at a carrier frequency.
  • Preferred embodiments further comprise transponder means for generating the carrier signal on the low voltage transmission line.
  • the present invention also encompasses methods for operating a distribution line carrier transmission system.
  • Methods in accordance with the invention comprise the steps of transmitting a carrier signal of a predetermined frequency and magnitude on a low voltage transmission line coupled via a transformer to a high voltage transmission line, and charging a capacitor coupled across a secondary winding of the transformer with the carrier signal until a voltage across the capacitor is approximately equal in magnitude to the predetermined magnitude, whereby the current and voltage drop between the point where said carrier signal originates and said capacitor are reduced and a transformer injection current is increased.
  • Other features of the invention are described below in connection with a detailed description of preferred embodiments.
  • Figure 1A is a schematic depiction of a prior art distribution line carrier transmission system.
  • FIGS. IB and 1C are schematic depictions of a distribution line carrier transmission system in accordance with the present invention.
  • Figure 2A depicts another embodiment of a prior art distribution line carrier transmission system.
  • Figure 2B depicts another embodiment of a distribution line carrier transmission system in accordance with the present invention.
  • FIG. 1B depicts a distribution line carrier transmission system in accordance with the present invention.
  • This system is like the system of Figure 1A but for the addition of a secondary filter capacitor 20 coupled across the terminals of the transformer 12.
  • the capacitor's value is selected to match the leakage reactance 14 of the transformer and combine with this reactance to provide an anti-resonant condition at the carrier frequency (e.g., 5-20 KHz) .
  • the leakage reactance can either be calculated or measured by well known techniques; for example, an approximation of the leakage reactance can be obtained by determining the ratio of the voltage and current (V/I) at the terminals of the secondary winding without the capacitor 20.)
  • V/I voltage and current
  • Typical carrier frequency transmitters are current limited at 2 amperes to keep from exceeding the current rating of low impedance transformers.
  • Figure 2A depicts a typical prior art short secondary wiring situation where the injection current is at the normal current limit level (2 amps) into a large transformer with a relatively low secondary leakage reactance 14' (e.g., j5 ohms) .
  • Figure 2B shows the same network with a matching capacitor 20' applied across the terminals of the transformer 12 to raise the impedance of the combination. The resultant transformer injection current is shown to have increased from the normal 2 amperes to 4 amperes, for an improvement of 6 dB.
  • the present invention is not limited to the specific embodiments described above.
  • the effective impedance of the transformer winding could be reduced by replacing the capacitor 20 with a series resonant capacitor in series with the transformer winding; however, a low impedance coil would have to be placed in parallel with the capacitor to allow the 60 Hz power current to flow through the winding. The coil would have to be capable of handling the 60 Hz power current.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

A power distribution system comprises a high voltage transmission line (10), a transformer (12), a low voltage transmission line coupled to the secondary winding of the transformer, a carrier transponder (18) coupled to the low voltage transmission line, and a capacitor (20). The capacitor (20) is matched to the leakage reactance such that a capacitive reactance of the capacitor combines with the leakage reactance to produce an anti-resonant condition that effectively increases the current in the secondary winding and thereby improves communications between the transponder and a power generation sub-station.

Description

DISTRIBUTION LINE CARRIER TRANSMISSION SYSTEM FIELD OF THE INVENTION
The present invention generally relates to power distribution systems, and more particularly relates to an improved distribution line carrier transmission system.
Still more particularly, the present invention relates to a filter for increasing the injection of current from a carrier transponder to a transformer in a distribution line carrier transmission system.
BACKGROUND OF THE INVENTION
In a power distribution system, power from a power generation substation is carried by a high voltage waveform on a transmission line; a transformer converts the power to a low voltage waveform, and the low voltage waveform is carried on a low voltage transmission line to a consumer. A power meter monitors the power delivered to the consumer.
In a distribution line carrier transmission system, a carrier transponder inside or associated with the power meter has means for sending and receiving information to and from the power generation substation. This
■information is used for billing and/or load management. The present invention relates to power distribution line carrier communication technology and particularly to methods for transmitting and receiving communication signals on power distribution networks that include long secondary service wiring.
Distribution networks comprise various lengths of secondary wiring that typically provide an impedance sufficiently low to allow the injection of normal current levels by the transponders. Injection current (i.e. , the current injected into the secondary winding of the transformer) is critical for establishing successful communications. There are cases where the secondary impedance, due to excessive wire length and wiring practices, can present an unusually large series impedance to the transponder and keep adequate current from being injected.
For example, Figure 1A depicts a prior art distribution line carrier transmission system comprising a high voltage transmission line 10 and a distribution transformer 12 having an internal leakage reactance 14 (e.g. , -jlO ohms) . The transformer 12 supplies voltage over a low voltage transmission line to a transponder 18. The low voltage transmission line typically presents a secondary wiring impedance 16 of approximately +jl0 ohms, the exact value depending upon the length of the transmission line. The reactance values given are for a carrier frequency of 12.5 Khz. Thus, if the transponder output voltage is limited to 20 volts (which is a typical open circuit output voltage at 12.5 KHz) , the system of Figure 1A will result in 1 ampere (20 V/J20Ω) of injection current delivered from the transponder 18 to the secondary winding of the transformer 12. One solution to this reduced injection current is to locate a signal repeater in the area of the transponder to pick up the reduced signal and retransmit it to the substation. This is a relatively costly solution since it requires work crews to install equipment on the high voltage primary lines. (Placing the repeater on the secondary side of the transformer would be impractical because reception would be limited to a single phase winding. In addition, the injection current would be attenuated by the transformer.) Moreover, an alternative solution is to increase the voltage generated by the transponder 18, however this is considered too expensive . In addition to the problem of secondary wiring loss, there are some instances where the secondary wiring is short and normal current is injected into the transformer but the injection current is still inadequate to get two-way communications established.
Accordingly, a primary goal of the present invention is to provide a mechanism to improve these situations by increasing the transformer injection current. A further goal of the present invention is to provide a technique by which the individual transformers can be analyzed and signal improvement can be made with very low associated cost.
SUMMARY OF THE INVENTION
A power distribution system in accordance with the present invention comprises a high voltage transmission line, a transformer comprising a primary winding coupled to the high voltage transmission line and a secondary winding, a low voltage transmission line coupled to the secondary winding, a carrier transponder operatively coupled to the low voltage transmission line, and filter means for effecting an anti-resonant condition across the secondary winding at a predetermined carrier frequency of the carrier transponder.
In one preferred embodiment of the present invention, the transformer is characterized by a leakage reactance and the filter means comprises a capacitor connected across the secondary winding and matched to the leakage reactance such that a capacitive reactance of the capacitor combines with the leakage reactance to produce the anti-resonant condition. The capacitive reactance in preferred embodiments appears as less than approximately 20 ohms (20Ω) (e.g., approximately five to ten ohms (5-10Ω) ) to a 5-20 KHz (e.g., 12.5 KHz) carrier signal.
The present invention also encompasses power distribution systems comprising a first transmission line; a transformer comprising a primary winding coupled to the first transmission line and a secondary winding, the transformer characterized by a leakage reactance associated with the secondary winding; a second transmission line coupled to the secondary winding; and a capacitor coupled across the secondary winding and presenting a capacitive reactance that matches the leakage reactance. An anti- resonant condition is effected for a carrier signal oscillating on the second transmission line at a carrier frequency. Preferred embodiments further comprise transponder means for generating the carrier signal on the low voltage transmission line.
The present invention also encompasses methods for operating a distribution line carrier transmission system. Methods in accordance with the invention comprise the steps of transmitting a carrier signal of a predetermined frequency and magnitude on a low voltage transmission line coupled via a transformer to a high voltage transmission line, and charging a capacitor coupled across a secondary winding of the transformer with the carrier signal until a voltage across the capacitor is approximately equal in magnitude to the predetermined magnitude, whereby the current and voltage drop between the point where said carrier signal originates and said capacitor are reduced and a transformer injection current is increased. Other features of the invention are described below in connection with a detailed description of preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1A is a schematic depiction of a prior art distribution line carrier transmission system.
Figures IB and 1C are schematic depictions of a distribution line carrier transmission system in accordance with the present invention.
Figure 2A depicts another embodiment of a prior art distribution line carrier transmission system. Figure 2B depicts another embodiment of a distribution line carrier transmission system in accordance with the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Figure IB depicts a distribution line carrier transmission system in accordance with the present invention. This system is like the system of Figure 1A but for the addition of a secondary filter capacitor 20 coupled across the terminals of the transformer 12. The capacitor's value (capacitance) is selected to match the leakage reactance 14 of the transformer and combine with this reactance to provide an anti-resonant condition at the carrier frequency (e.g., 5-20 KHz) . (The leakage reactance can either be calculated or measured by well known techniques; for example, an approximation of the leakage reactance can be obtained by determining the ratio of the voltage and current (V/I) at the terminals of the secondary winding without the capacitor 20.) By applying the capacitor 20 to the transformer 12, the impedance of the transformer-capacitor combination is significantly higher than the transformer impedance alone and the current from the transponder 18 is reduced below the 1 ampere value discussed above. In this case, though, the 20 volt output of the transponder is applied to the transformer and capacitor combination because the series impedance will not drop significant voltage with the reduced transponder output current. In other words, a 2 ampere current loop is established. The result is that the transformer current will be 2 amperes instead of 1 ampere. The filter capacitor 20 therefore supplies the increased transponder injection current and increases it above that of the Figure 1A system by a factor of 2 (6 dB) .
Another positive effect of placing the capacitor 20 across the transformer terminals is in the improvement in receive voltage coming through the transformer 12 from the primary side. Referring to Figure 1C, assume the receive voltage is 100 millivolts. When the capacitor 20 is connected across the terminals of the transformer 12, the receive signal will be increased due to the action of the capacitor working with leakage reactance of the transformer in a series resonant manner. Calculations made with a quality factor (Q) of 3 indicate that the receive voltage would increase from 100 millivolts to 333 millivolts.
Typical carrier frequency transmitters are current limited at 2 amperes to keep from exceeding the current rating of low impedance transformers. Figure 2A depicts a typical prior art short secondary wiring situation where the injection current is at the normal current limit level (2 amps) into a large transformer with a relatively low secondary leakage reactance 14' (e.g., j5 ohms) . Figure 2B shows the same network with a matching capacitor 20' applied across the terminals of the transformer 12 to raise the impedance of the combination. The resultant transformer injection current is shown to have increased from the normal 2 amperes to 4 amperes, for an improvement of 6 dB. The present invention is not limited to the specific embodiments described above. For example, the effective impedance of the transformer winding could be reduced by replacing the capacitor 20 with a series resonant capacitor in series with the transformer winding; however, a low impedance coil would have to be placed in parallel with the capacitor to allow the 60 Hz power current to flow through the winding. The coil would have to be capable of handling the 60 Hz power current.

Claims

I claim:
1. A power distribution system, comprising:
(a) a high voltage transmission line;
(b) a transformer comprising a primary winding coupled to said high voltage transmission line and a secondary winding;
(c) a low voltage transmission line coupled to said secondary winding;
(d) a carrier transponder operatively coupled to said low voltage transmission line; and
(e) filter means for effecting a condition wherein the impedance of said secondary winding/filter means combination is increased at a predetermined carrier frequency of said carrier transponder.
2. A power distribution system according to claim 1, wherein the transformer is characterized by a leakage reactance and the filter means comprises a capacitor connected across the secondary winding and matched to the leakage reactance such that a capacitive reactance of the capacitor combines with the leakage reactance to produce an anti-resonant condition.
3. A power distribution system according to claim 2, wherein said capacitive reactance appears as less than approximately 20 ohms (20Ω) to a 5-20 KHz carrier signal.
4. A power distribution system according to claim 2, wherein said capacitive reactance appears as approximately five to ten ohms (5-10Ω) to a 5-20 KHz carrier signal .
5. A power distribution system according to claim 2, wherein said capacitive reactance appears as approximately 10 ohms (10Ω) to a 5-20 KHz carrier signal. 6. A power distribution system, comprising:
(a) a first transmission line;
(b) a transformer comprising a primary winding coupled to said first transmission line and a secondary winding, said transformer characterized by a leakage reactance associated with said secondary winding;
(c) a second transmission line coupled to said secondary winding; and
(d) a capacitor coupled across said secondary winding and presenting a capacitive reactance that matches said leakage reactance, whereby, for a carrier signal oscillating on said second transmission line at a carrier frequency, an anti-resonant condition is effected.
7. A power distribution system according to claim 6, further comprising transponder means for generating said carrier signal on said low voltage transmission line.
8. A power distribution system according to claim 7, wherein said carrier signal has a frequency of approximately 5-20 KHz and said capacitive reactance appears as less than approximately 20 ohms (20Ω) to said carrier signal.
9. A power distribution system according to claim 8, wherein said capacitive reactance appears as approximately ten ohms to said carrier signal .
10. A power distribution system according to claim 8, wherein said capacitive reactance appears as approximately five ohms to a said carrier signal .
11. A method for operating a distribution line carrier transmission system, comprising the steps of: (a) transmitting a carrier signal of a predetermined frequency and magnitude on a low voltage transmission line coupled via a transformer to a high voltage transmission line; and
(b) charging a capacitor coupled across a secondary winding of the transformer with said carrier signal until a voltage across said capacitor is approximately equal in magnitude to the predetermined magnitude, whereby the current and voltage drop between the point where said carrier signal originates and said capacitor are reduced and a transformer injection current is increased.
AMENDED CLAIMS
[received by the International Bureau on 11 January 1994 (11.01.94); original claim 2 cancelled; Original claims 1,3-6 and 11 amended; other claims unchanged (3 pages)]
1. A power distribution system, comprising:
(a) a high voltage transmission line;
(b) a distribution transformer comprising a primary winding coupled to said high voltage transmission line and a secondary winding;
(c) a low voltage transmission line coupled to said secondary winding;
(d) a carrier transponder operatively coupled to said low voltage transmission line; and (e) filter means for effecting a condition wherein the impedance of the secondary winding in combination with the filter means is increased at a predetermined carrier frequency of said carrier transponder; wherein the transformer is characterized by a leakage reactance and the filter means comprises a capacitor connected across the secondary winding and matched to the leakage reactance such that a capacitive reactance of the capacitor combines with the leakage reactance to produce an anti-resonant condition.
3. A power distribution system according to claim 3, wherein said capacitive reactance appears as less than approximately 20 ohms (20Ω) to a 5-20 KHz carrier signal.
4. A power distribution system according to claim 3, wherein said capacitive reactance appears as approximately five to ten ohms (5-10Ω) to a 5-20 KHz carrier signal.
5. A power distribution system according to claim 3, wherein said capacitive reactance appears as approximately 10 ohms (10Ω) to a 5-20 KHz carrier signal.
6. A power distribution system, comprising:
(a) a first transmission line;
(b) a distribution transformer comprising a primary winding coupled to said first transmission line and a secondary winding, said transformer characterized by a leakage reactance associated with said secondary winding;
(c) a second transmission line coupled to said secondary winding; and
(d) a capacitor coupled across said secondary winding and presenting a capacitive reactance that matches said leakage reactance, whereby, for a carrier signal oscillating on said second transmission line at a carrier frequency, an anti-resonant condition is effected.
7. A power distribution system according to claim 6, further comprising transponder means for generating said carrier signal on said low voltage transmission line.
8. A power distribution system according to claim
7, wherein said carrier signal has a frequency of approximately 5-20 KHz and said capacitive reactance appears as less than approximately 20 ohms (20Ω) to said carrier signal.
9. A power distribution system according to claim
8, wherein said capacitive reactance appears as approximately ten ohms to said carrier signal.
10. A power distribution system according to claim 8, wherein said capacitive reactance appears as approximately five ohms to a said carrier signal.
11. A method for operating a distribution line carrier transmission system, comprising the steps of: (a) transmitting a carrier signal of a predetermined frequency and magnitude on a low voltage transmission line coupled via a distribution transformer to a high voltage transmission line; and
(b) charging a capacitor coupled across a secondary winding of the transformer with said carrier signal until a voltage across said capacitor is approximately equal in magnitude to the predetermined magnitude, whereby the current and voltage drop between the point where said carrier signal originates and said capacitor are reduced and a transformer injection current is increased.
STATEMENT UNDER ARTICLE19
Claim 2 has been cancelled and all of its limitations have been incorporated into independent claim 1. The dependencies of claims 3-5 have been appropriately corrected. The independent claims (l, 6 and 11) have been amended to recite that the transformer is a distribution transformer.
PCT/US1993/007883 1992-08-24 1993-08-23 Distribution line carrier transmission system WO1994005091A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US93471292A 1992-08-24 1992-08-24
US934,712 1992-08-24

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Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3696383A (en) * 1970-01-17 1972-10-03 Tokyo Electric Power Co Information transmission system for metered magnitudes
US3964048A (en) * 1974-01-28 1976-06-15 General Public Utilities Corporation Communicating over power network within a building or other user location
US4130861A (en) * 1976-12-22 1978-12-19 General Electric Company Power line carrier noise elimination
US4136319A (en) * 1976-03-26 1979-01-23 Cgee Alstlom S.A. Filtering device for high-voltage power lines used as high-frequency transmission media
US4321581A (en) * 1978-03-10 1982-03-23 Siemens Aktiengesellschaft Powerline carrier control system
US4383243A (en) * 1978-06-08 1983-05-10 Siemens Aktiengesellschaft Powerline carrier control installation
US4602204A (en) * 1984-11-02 1986-07-22 Hase A M Auto-start and magnetic shut down battery charging and surveillance circuits
US4697166A (en) * 1986-08-11 1987-09-29 Nippon Colin Co., Ltd. Method and apparatus for coupling transceiver to power line carrier system
US4973940A (en) * 1987-07-08 1990-11-27 Colin Electronics Co., Ltd. Optimum impedance system for coupling transceiver to power line carrier network

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3696383A (en) * 1970-01-17 1972-10-03 Tokyo Electric Power Co Information transmission system for metered magnitudes
US3964048A (en) * 1974-01-28 1976-06-15 General Public Utilities Corporation Communicating over power network within a building or other user location
US4136319A (en) * 1976-03-26 1979-01-23 Cgee Alstlom S.A. Filtering device for high-voltage power lines used as high-frequency transmission media
US4130861A (en) * 1976-12-22 1978-12-19 General Electric Company Power line carrier noise elimination
US4321581A (en) * 1978-03-10 1982-03-23 Siemens Aktiengesellschaft Powerline carrier control system
US4383243A (en) * 1978-06-08 1983-05-10 Siemens Aktiengesellschaft Powerline carrier control installation
US4602204A (en) * 1984-11-02 1986-07-22 Hase A M Auto-start and magnetic shut down battery charging and surveillance circuits
US4697166A (en) * 1986-08-11 1987-09-29 Nippon Colin Co., Ltd. Method and apparatus for coupling transceiver to power line carrier system
US4973940A (en) * 1987-07-08 1990-11-27 Colin Electronics Co., Ltd. Optimum impedance system for coupling transceiver to power line carrier network

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