Apparatus for and method of attenuating power line carrier communication signals passing between substation distribution lines and transmission lines through substation transformers

• US 4,602,240 A
• Filed: 03/22/1984
• Issued: 07/22/1986
• Est. Priority Date: 03/22/1984
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Perkins, William C., Whang, Keh-Wen
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/592,139
• Time in Patent Office: 852 Days
• Field of Search: 340/310 R, 340/310 A, 323/361, 336/5
• US Class Current: 307/3
• CPC Class Codes: H04B 2203/5425 improving S/N by matching impedance, noise reduction, gain control
• CPC Class Codes: H04B 2203/5466 using three phases conductors
• CPC Class Codes: H04B 2203/5483 using coupling circuits
• CPC Class Codes: H04B 2203/5491 using filtering and bypassing
• CPC Class Codes: H04B 3/56 Circuits for coupling, blocking, or by-passing of signals

Abstract

A shunt three-phase wye-connected capacitor bank is connected intermediate a substation transformer and any source of zero-sequence power line carrier communication signals being transmitted on the substation distribution network to partially alleviate unbalance conditions in the communication signals which in the balanced condition are not passed by a three-phase substation transformer to the main transmission line. The signal is further attenuated by connecting the common wye-point of the capacitor bank through an inductance to neutral to form a shunt element of either an L or pi attenuation circuit with the series inductance of the substation transformer and the transmission line inductance forming the serial elements of the L or pi circuit. A further shunt element at another substation distribution network completes the attenuation circuit for the pi configuration.

Claims

1. The method of reducing crosstalk between three-phase power line carrier transceivers situated at two remote three-phase substation electric power distribution networks that are electrically interconnected through (i) a three-phase transmission line and (ii) substation transformers at opposite ends of the transmission line, where the transceivers are intended to communicate only with other communication devices within a given substation power distribution network, comprising the steps of:

capacitively coupling each of the three-phase lines of each distribution network together in a wye connection to form a capacitor bank at a point between the transceiver and the substation transformer at each substation experiencing substantial crosstalk where the capacitive values are such as to substantially block signals at the electric power frequency and provide substantially no blocking effect at the transceiver carrier frequency; and

connecting the common point of said wye-connected capacitor bank to neutral through a shunt inductance where the inductance is of such a value that there is a high ratio of desired communication signal to crosstalk communication signal, the capacitor bank and shunt inductance at each distribution network at each end of the interconnecting electrical transmission line along with the intermediate reactances connecting the capacitor banks forming a three-phase balanced pi communication frequency attenuation circuit in which the capacitor bank and the associated shunt inductance at each distribution network form a series combination that is in shunt relationship with the main path of the communications signal in the associated distribution network.

2. Apparatus for reducing crosstalk interference between three-phase power line carrier transceivers situated at two remote three-phase substation electric power distribution networks that are electrically interconnected through (i) a three-phase transmission line and (ii) substation transformers at opposite ends of the transmission line, where the transceivers are intended to communicate only with only communication devices within a given substation power distribution network, comprising, in combination:

capacitive first means for capacitively coupling each of the three-phase lines of each distribution network together in a wye connection to form a capacitor bank at a point between the transceiver and the substation transformer at each substation experiencing substantial crosstalk where the capacitive values are such as to substantially block signals at the electric power frequency and provide substantially no blocking effect at the transceiver carrier frequency; and

inductive second means, connected to said first means, for providing a shunt inductance between the common point of said wye-connected capacitor bank and neutral where the inductance is of such a value that there is a high ratio of desired communication frequency signal to crosstalk communication frequency signal, the first means and second means at each distribution network at each end of the interconnecting transmission line along with the intermediate transformer and transmission line inductances forming a three-phase balanced pi communication frequency attenuation circuit in which said first means and the associated second means connected thereto at each distribution network form a series combination that is in shunt relationship with the main path of the communications signal in the associated power distribution network.

8. The combination of claim 2 in which the substation transformer associated with each distribution network comprises a primary winding of delta configuration connected in said transmission line and a secondary winding connected in the associated power distribution network.

9. The combination of claim 8 in which the secondary winding of each of said substation transformers is of a wye configuration and the wye point thereof is connected to neutral.

3. The method of attenuating crosstalk between communication frequency transceivers which are respectively connected to remotely situated three-phase substation power distribution networks forming parts of a large low frequency three-phase electric power distribution system in which the networks are interconnected through a transmission line and substation transformers at opposite ends of the transmission line and in which the transceivers are intended to communicate with devices solely within the substation power distribution network, comprising the steps of:

capacitively coupling the three phases together in a wye-connected capacitor bank on the load side of the first associated substation transformer between the first associated substation transformer and the transceiver at a first interfering substation to partially rebalance the communication signal amplitudes as seen by said first associated substation transformer;

capacitively coupling the three phases together in a wye-connected capacitor bank on the load side of the second associated substation transformer between the second associated substation transformer and the transceiver at a second interfering substation to partially rebalance the communication signal amplitudes as seen by said second associated substation transformer and

inductively coupling each of the capacitor bank common wye-points to neutral to form shunt elements which (i) in combination with the series inductance of the substation transformers and interconnecting transmission line, create a pi-type communication frequency attenuation network between crosstalk interfering transceivers and (ii) are in shunt relationship with the main path of the communications signal in the associated power distribution network.

4. Pi attenuator apparatus (a series element with a shunt element on each end) for attenuating communication frequency interference signals transmitted over a three-phase electric transmission line interconnecting through first and second substation transformers remotely situated first and second substation electrical power distribution networks, respectively, where said remotely situated substation power distribution networks have their own communication frequency signals superimposed on the low frequency distribution networks, comprising in combination:

first communication frequency shunt circuit element means, connected intermediate a first substation transformer and any communication equipment for the associated first electrical network, comprising a shunt inductor means coupled through a three-phase capacitor bank between the phase conductors of said associated first network and a neutral conductor, said first shunt circuit element means being in shunt relationship with the main path of the communications signal in the associated first network;

second communication frequency shunt circuit element means, connected intermediate a second substation transformer and any communication equipment for the associated second electrical network, comprising a shunt inductor means coupled through a three-phase capacitor bank between the phase conductors of said associated second network and a neutral conductor, said second shunt circuit element means being in shunt relationship with the main path of the communications signal in the associated second electrical network; and

series element circuit means comprising the series combination of the series inductance of the remotely situated substation transformers and the intermediate transmission line.

5. Apparatus for attenuating crosstalk between communication frequency transceivers which are respectively connected to remotely situated three-phase substation power distribution networks forming a part of a large low frequency three-phase electric power distribution system in which the networks are interconnected through a transmission line and substation transformers at opposite ends of the transmission line and in which the transceivers are intended to communicate with devices solely within the associated substation power distribution network, comprising:

first means for capacitively coupling the three phases together in a wye-connected capacitor bank on the load side of the substation between the substation and the transceiver at a first interfering substation to partially rebalance the communication signal amplitudes as seen by the substation transformer of said first substation; and

second means for capacitively coupling the three phases together in a wye-connected capacitor bank on the load side of the substation between the substation and the transceiver at a second interfering substation to partially rebalance the communication signal amplitudes as seen by the substation transformer of said second substation, and

third means for inductively coupling each of the capacitor bank common wye-points to neutral to form, in combination with the inductance of the substation transformers and interconnecting transmission lines, a pi-type communication frequency attenuation network between crosstalk interfering transceivers in which the first and third means at the first substation and the second and third means at the second substation respectively form series combinations that are in shunt relationship with the main path of the communications signal in the associated substation distribution networks.

6. Apparatus for minimizing the amplitude of communication frequency signals, which are superimposed on lower frequency electric power lines for use only on a substation distribution network, which are passed through a three-phase substation transformer to a main power high voltage transmission line connected to the transformer on the opposite side thereof from said network, comprising, in combination:

three-phase wye-connected capacitor bank means, connected to the three-phase substation distribution network lines intermediate any communication equipment for that substation distribution network and the substation transformer for that substation distribution network having a capacitance which acts as a shunt to communication frequency signals; and

shunt inductance means connected between a neutral point and the common wye-point in said wye-connected capacitor bank means, the capacitor bank and shunt inductance forming the shunt element of an L-type attenuator and the series inductance of the substation transformer and the main transmission line forming the series element of said L-type attenuator, said shunt element being in shunt relationship with the main path of the communication frequency signal in said substation distribution network.

7. Apparatus as claimed in claim 6 at each of two substation distribution networks which are interconnected through said transmission line and through substation transformers for the respective substations at opposite ends of said transmission line, where each of the capacitor banks and associated shunt inductances form a shunt element of a pi-type attenuator network, and the transformer and line inductances between the capacitor banks form the series element of said pi attenuator network, said shunt element in each network being in shunt relationship with the main path of the communication frequency signal in said associated network.