EP1285502A1

EP1285502A1 - Method and system for transmitting data over a low-voltage electricity supply network

Info

Publication number: EP1285502A1
Application number: EP00926632A
Authority: EP
Inventors: Hanspeter Widmer
Original assignee: Ascom Powerline Communications AG
Current assignee: Ascom Intermediate AG
Priority date: 2000-05-30
Filing date: 2000-05-30
Publication date: 2003-02-26
Also published as: IL152444A0; BR0015883A; AU2000245329A1; CN1452816A; TW508912B; WO2001093452A1

Abstract

The invention relates to a low-voltage electricity supply network comprising a first conductor (1) and a second conductor (2) that are parallelly arranged in the manner of a double line in an area, which is provided for transmitting data, of the low-voltage electricity supply network. In order to transmit data, a carrier signal is generated in a push-pull mode between the first conductor (1) and the second conductor (2), whereby the frequency of this carrier signal lies essentially over the network frequency. In addition, symmetrical impedances in both conductors are ensured in the network area provided for transmitting data. This results in achieving an electromagnetic shielding of the network area.

Description

Method and arrangement for the transmission of data via a low-voltage power supply network

Technical field

The invention relates to a method for the transmission of data via a low-voltage power supply network according to the preamble of claim 1 and an arrangement for carrying out said method. State of the art

It is known to also transmit messages such as telephone calls, fax copies, digital data, etc. via low-voltage power supply networks or partial areas of such networks. For this purpose, the data is encoded and a high-frequency carrier signal in a known manner, e.g. by frequency modulation. The modulated carrier signal is coupled into the low-voltage power supply network by the respective transmitter and decoupled and decoded again in the same way by the respective receiver. Message transmission systems that use a power supply network in this way and are particularly suitable for in-house operation are e.g. in WO-A-00/1 1 759 (Ascom Systec AG). Such systems are referred to as powerline communication systems (abbreviated as PLC systems), typically the network frequencies for the power supply in a range between approximately 15 Hz and 100 Hz and the carrier signal frequencies in a range between approximately 1 MHz and 40 MHz.

With regard to electromagnetic compatibility, especially in the case of secondary use of frequencies as carrier signal frequencies, which are primarily allocated to certain radio services, the highest possible electromagnetic shielding of the network area used for data transmission is desirable. The higher this shielding, the smaller the electromagnetic interference fields in the environment of the power supply network caused by the PLC operation and the lower the likelihood of mutual interference between the PLC system and the radio services associated with radio frequencies operated that correspond to the PLC carrier signal frequency.

In principle, it would be possible to achieve electromagnetic shielding of the areas of power supply networks intended for PLC operation by means of measures which are widely used in high-frequency technology. For example, coaxial cables could be used as conductors for the power supply networks. However, this would have considerable disadvantages in terms of the costs for a PLC system. Presentation of the invention

The object of the invention is to provide a PLC system which ensures good electromagnetic shielding of the area of a low-voltage power supply network used for PLC operation and which is also particularly suitable for operation on existing power supply networks.

The solution to the problem is defined by the features of the independent claims. For the transmission of data via a low-voltage power supply network with at least a first and a second conductor by means of a carrier signal, the frequency of which is substantially above the network frequency for the power supply, the carrier signal is in accordance with the invention in a region of the low-voltage power supply network which the two conductors are arranged essentially parallel in the manner of a double line, generated in a push-pull mode between the first conductor and the second conductor. In addition, symmetrical impedances are ensured in the two conductors in this network area.

An arrangement according to the invention for the transmission of data via a low-voltage power supply network with at least a first and a second conductor comprises means for in a region of the low-voltage power supply network in which the two conductors are arranged essentially in parallel in the manner of a double line are to generate a carrier signal in a push-pull mode between the first conductor and the second conductor, the frequency of this carrier signal being substantially above the mains frequency, and means for creating symmetrical impedances in the two conductors in this network region.

In connection with the present description and the claims, two conductors are said to be arranged in parallel in the manner of a double line if they are arranged close to one another and parallel to one another. It does not matter whether other conductors are arranged in parallel to the two conductors in order to form a multi-conductor power line, for example. From this definition both lines with only two conductors and also lines with more than two conductors, provided that in the latter case at least two conductors are arranged close to one another and parallel to one another.

The impedances of two conductors of a pair of conductors arranged in parallel in the manner of a double line are said to be symmetrical if, at any location along the length of the line, the impedance of the first conductor with respect to a reference base (for example with respect to earth) is substantially equal to the impedance of the second conductor on the same Location is opposite the same reference base.

Furthermore, in connection with the present description and the claims, a carrier signal generated in push-pull mode between a first conductor and a second conductor means that the two conductors have opposite voltages. A push-pull line is understood to mean a line with at least two conductors, between which a signal is generated in push-pull mode.

The invention creates a so-called symmetrical operating state for data transmission (i.e. for PLC operation) in an area of the low-voltage power supply network designed in the manner of a double line. In order to achieve a symmetrical operating state in a double line, the double line must be supplied symmetrically (e.g. by an appropriately trained generator), the symmetry must not be disturbed by terminating resistors or by connecting resistors from network branches connected to the double line and the double line must be symmetrical above the earth be constructed.

By creating a symmetrical operating state for the PLC operation according to the invention in a multi-conductor line, an electromagnetic shielding of the line is achieved, because opposite high-frequency currents (ie high-frequency currents) in the two conductors at each point of the line at any time flow with opposite voltage) of the same size, the long-range electromagnetic effect of the high-frequency currents in the two conductors is canceled. The invention makes it possible for areas of existing low-voltage power supply networks, such as those found in most existing buildings, comprising multi-conductor lines to be usable for data transmission in connection with PLC systems without great additional outlay. As the only measure to be taken on such a power supply network itself, it is only necessary to ensure an impedance symmetry in two conductors arranged in the manner of a double line in the area of the power supply network provided for data transmission.

Symmetrical impedances in two conductors of an existing low-voltage power supply network can e.g. can be produced by connecting one or more electrical components with a predetermined impedance. This is particularly easy to implement if house installation devices, e.g. comprise an on / off switching element and / or a switching element and / or a socket, are designed and arranged (for example by being provided with additional, unused connecting terminals) such that further electrical components can be connected to them. In this case, electrical components with a predetermined impedance can be mounted directly on these house installation devices in order to create symmetrical impedances and thereby achieve electromagnetic shielding of the network area provided for data transmission.

The means for creating symmetrical impedances preferably comprise at least one electrical component with a specific capacitance and / or at least one electrical component with a specific inductance. In the present context, an electrical component with a specific capacitance (e.g. a capacitor) is also referred to as a capacitance and an electrical component with a specific inductance (e.g. a coil) is also referred to as an inductor.

According to a variant of the invention, an impedance balancing means in the form of a capacitance is used to bridge a switching element in a network branch, which are connected to the network area provided for PLC operation. Such Switching elements cause a disturbance in the impedance symmetry in the network area intended for PLC operation without corresponding countermeasures for impedance balancing.

Bridging capacitors suitable as impedance balancing means only have to be specified for the mains voltage of the supply network. However, they do not have to be designed to pass the mains current to the consumers and can be dimensioned accordingly weak. Such bridging capacitors thus represent a particularly small and inexpensive form of means for creating symmetrical impedances according to the invention.

The capacities are to be dimensioned in such a way that they act as high-pass filters and essentially conduct currents whose frequency is substantially above the mains frequency, while essentially damping currents in the region of the mains frequency. Capacities between 1 nF and 1 μF, in particular between 10 nF and 0.1 μF, are preferred for PLC operation with a mains frequency in the range from 15 Hz to 100 Hz and a carrier signal frequency in the range from 1 MHz to 40 MHz.

Bridging capacitors suitable for impedance symmetry can be easily and quickly installed in electrical home installation devices, e.g. in light switch / push button or in light switch / push button socket combinations. Often such modern house installation devices are provided with one or more additional connection terminals for each connection pole, which are generally not used. In this case, the bypass capacitors can be connected to these additional connection terminals in the simplest way.

House installation devices of modern design are often also provided with a socket for inserting a glow lamp for orientation or control purposes, which, for example, bridges a light switch. For cost reasons, however, no appropriate glow lamp is usually installed. In this case, instead of a plug-in glow lamp, a plug-in bypass capacitor in a housing, the outer shape of which Glow lamp housings are used as a means of creating symmetrical impedances for PLC operation. This bridging capacitor must then be switched according to the orientation lamp (bridging the light switch).

The use of impedance balancing means in the form of capacitors is limited to network branches, the branch conductors of which are arranged essentially in parallel in the manner of double lines. In the case of network branches with branch conductors not arranged in parallel, symmetry of the impedances can be achieved by means of inductors, in particular by means of coils, which are connected between the branch conductors and the network area provided for PLC operation. The inductances are to be determined in such a way that they strongly attenuate currents whose frequency is significantly above the mains frequency, but attenuate currents in the region of the mains frequency as little as possible. Such inductors or coils are also referred to below as RF chokes or as RF choke coils. For PLC operation with a mains frequency in the range from 15 Hz to 100 Hz and a carrier signal frequency in the range from 1 MHz to 40 MHz, inductances between 1 μH and 100 μH, in particular inductances in the order of 10 μH, are preferred.

In contrast to the impedance balancing means in the form of capacitors, the impedance balancing means must be designed in the form of inductors for the passage of the low-frequency network current (i.e. the actual supply current of the power supply network) to the consumers connected to the network branches. They are therefore generally larger and more expensive than the former. For this purpose, impedance symmetry in the network area intended for PLC operation can be achieved by means of impedance balancing means in the form of inductors, even in the case of network branches with non-parallel branch conductors, which is generally not possible by means of impedance balancing means in the form of capacitors.

From the following detailed description and the entirety of the claims, further advantageous embodiments and combinations of features of the invention result. Brief description of the drawings

The drawings used to explain the exemplary embodiment show:

Fig. 1 in a schematic representation of a first partial view of an arrangement for the

Transmission of data according to a preferred embodiment of the invention;

Fig. 2 shows a schematic representation of a further partial view of the arrangement

Fig. 1;

Fig. 3 shows a schematic representation of a further partial view of the arrangement

Fig. 1;

Fig. 4 shows a schematic representation of a further partial view of the arrangement

Fig. 1.

In principle, the same parts are provided with the same reference symbols in the figures.

Ways of Carrying Out the Invention

In Fig. 1 a first section of a low-voltage power supply network is shown in a simplified, schematic representation, which is operated with an AC voltage of 230 V and a network frequency of 50 Hz and which has an arrangement for the transmission of data according to a preferred embodiment of the Invention is provided.

A section of this power supply network provided for PLC operation comprises a power line in the form of a three-core power cable. A first conductor 1 (or a first

Core 1) of the power cable serves as phase conductor 1, a second conductor 2 (or a second one)

Core 2) as neutral conductor 2 and the third conductor 3 (or the third core 3) as protective earth 3 Power line. As usual, the three conductors 1, 2, 3 are arranged essentially parallel to one another in a common cable. Thus in particular the phase conductor 1 and the neutral conductor 2 are arranged essentially parallel to one another in the manner of a double line.

For PLC operation, a carrier signal is generated in a push-pull mode between phase conductor 1 and neutral conductor 2 for data transmission. The frequency of this carrier signal is considerably above the mains frequency. The carrier signal frequency is between 1 MHz and 40 MHz and is preferably approximately 10 MHz.

As can be seen in FIG. 1, a first network branch is connected to the low-voltage power supply network in the network area provided for data transmission, in order to supply a first consumer in the form of a room lamp (not shown) with power from the power supply network. This network branch comprises a first branch conductor 11, which is connected to the phase conductor 1, and a second branch conductor 12, which is connected to the neutral conductor 2. The two branch conductors 11, 12 are arranged essentially parallel to one another in the manner of a double line in a common two-wire cable.

The first branch conductor 11 connected to the phase conductor 1 is provided with an on / off switching element 16 of the type of an interruption switch 16, with which this branch conductor 11 can either be interrupted or short-circuited in order to switch the room lamp on or off.

In order to prevent the branch conductors 11, 12 from having different impedances at their connection points to the phase conductor 1 or the neutral conductor 2 in the area of the carrier signal frequency, depending on the position of the interruption switch 16, a bypass capacitor 15 is connected in parallel to the switch 16. The bypass capacitor 15 has a capacitance between 10 nF and 0.1 μF. It therefore acts as a high pass filter. Currents with frequencies in the area of the carrier signal are hardly damped, but currents with frequencies in the area of the network frequency are essentially prevented. Thus, the two branch conductors 1 1, 12 of the network branch for signals in the area of the carrier signal frequency, regardless of the position of the interruption switch 16, always provide a conductive connection between the conductors 1 and 2 of the area of the power supply network intended for PLC operation and that at the other end of the branch conductor connected consumers. The impedances in this frequency range in the two branch conductors 1 1, 12 are always symmetrical.

FIG. 2 shows a further section of the three-wire cable of the low-voltage power supply network provided for PLC operation and shown in FIG. 1. In the network area provided for data transmission, another network branch to the. Low-voltage power supply network connected to supply another consumer in the form of a lamp (not shown) with electricity from the power supply network.

The further network branch shown in FIG. 2 comprises two branch conductors 23, 24 which can be alternately connected to a branch conductor section 21 by means of a changeover element 36, which in turn is connected to the phase conductor 1 in the network area provided for PLC operation. The two branch conductors or phase conductors 23, 24 are arranged parallel to one another in the manner of a double line and can be alternately connected to another branch conductor piece (not shown) by means of a further similar switching element (not shown), which in turn is connected to the lamp. Parallel to the two switchable branch conductors 23, 24 and the branch conductor pieces 21 is one. arranged further branch conductor 22, via which the lamp is connected to the neutral conductor of the supply network. By means of this known circuit arrangement, the lamp can optionally be switched on and off by means of the two switching elements 36, the two switching elements 36 being able to be actuated independently of one another.

In the case of the arrangement shown in FIG. 2, a bridging capacitor 25 is connected in a bridging function between the two switchable branch conductors 23, 24 for the impedance symmetry in the network area provided for the PLC operation. This bridging capacitor is in turn dimensioned such that it acts as a high pass filter works and hardly attenuates currents with frequencies in the range of the carrier signal, but essentially suppresses currents with frequencies in the range of the network frequency. The two switchable phase conductors 23, 24 are capacitively coupled to one another by the capacitor 25 for high frequencies. They are also long enough so that they have a sufficiently large switching capacity for the PLC operating frequency such that an additional bypass capacitor can be dispensed with. In the high-frequency range, the impedances in the branch conductor 22 connected to the neutral conductor on the one hand and in the branch conductor 21, 23, 24 connected to the phase conductor are always symmetrical, regardless of the switching positions of the two switching elements 36.

FIG. 3 shows a further section of the three-wire cable of the low-voltage power supply network provided for PLC operation and shown in FIG. 1. In the network area provided for data transmission, a further network branch is connected to the low-voltage power supply network in order to supply another power consumer (not shown) with power from the power supply network.

The network branch shown in FIG. 3 comprises a first branch conductor 31, which is connected to the phase conductor 1, and a second branch conductor 32, which is connected to the neutral conductor 2. The two branch conductors 31, 32 are each designed as independent single-core cables. These each create an electrically conductive connection between the consumer connected to the network branch on the one hand and the phase conductor 1 or the neutral conductor 2 of the power supply network on the other hand, in order to supply the consumer with electricity. The two branch conductors 31, 32 lead via separate paths. They are not arranged parallel to one another.

The first branch conductor 31 connected to the phase conductor 1 is provided with an on / off switching element 36 of the type of an interruption switch 36, with which this branch conductor 31 can either be interrupted or short-circuited in order to switch the room lamp on or off. > In order to prevent the branch conductors 31, 32 from having different impedances at their connection points to the phase conductor 1 or the neutral conductor 2 in the area of the carrier signal frequency depending on the position of the interruption switch 36, the two branch conductors 31, 32 are each connected by a coil 37 and 38 connected to phase conductor 1 and neutral conductor 2, respectively. The two coils 37, 38 each have an inductance on the order of 10 μH. They are also designed to pass the supply currents to the consumer. The coils 37, 38 thus each act as an RF choke, which essentially suppress both common-mode currents and push-pull currents with frequencies in the area of the carrier signal, but hardly dampen currents with frequencies in the area of the mains frequency. The coils in the high frequency range shield the network area provided for the PLC area from the network branch shown in FIG. 3 with the branch conductors 31, 32, so that this network branch does not impair the impedance symmetry in the network area provided for the PLC area in the high frequency range can.

FIG. 4 shows a further section of the three-wire cable of the low-voltage power supply network provided for PLC operation and shown in FIG. 1. In the network area provided for data transmission, a further network branch is connected to the low-voltage power supply network, which is similar to the network branch shown in FIG. 3.

The network branch shown in FIG. 4 comprises a first branch conductor 41, which is connected to the phase conductor 1, and a second branch conductor 42, which is connected to the neutral conductor 2. The two branch conductors 41, 42 are each designed as independent single-core cables and connected to a consumer (not shown) via separate, non-parallel paths in order to supply the consumer with electricity. The first branch conductor 41 connected to the phase conductor 1 is in turn provided with an on / off switching element 46 of the type of an interruption switch 46 in order to be able to switch the current to the consumer either on or off. In contrast to the arrangement shown in FIG. 3, a ring core 45 made of ferrite material is provided in the arrangement shown in FIG. 4 for the impedance symmetry, which ring core 41, 42 ^' in the vicinity of their connections to the phase conductor 1 and the Neutral conductor 2 encloses. By guiding the two branch conductors 41, 42 through the toroidal core 45, in principle a toroidal core coil 45 with the number of turns 1/2 is formed, which acts as an HF choke and in the high-frequency range also the network area intended for PLC operation from the network branch shields the two branch conductors 41, 42 in order to prevent impairment of the impedance symmetry in the network area provided for the PLC operation.

In other variants of the invention, not shown in the figures, the branch conductors can also be wound in the manner of a bifilar winding with a large number of turns around the ring core in order to increase the inductance of the ring core coil (and thus the effect of the RF choke). Furthermore, instead of only two branch conductors, a single toroidal core can also enclose a plurality of branch conductors, and these can be wound around the toroidal core in the manner of a multi-filament winding in order to form a toroidal core coil acting as an HF choke with a large number of turns and a large number of conductors form.

The toroidal coils with bifilar winding only suppress high-frequency balancing currents, but not high-frequency push-pull currents. This creates the possibility that a network branch which is connected to a network area intended for PLC operation by means of a toroidal core coil can in some cases also be used outside of the toroidal core coil for PLC operation.

In summary, it can be stated that the invention creates a PLC system which ensures good electromagnetic shielding of the area of a low-voltage power supply network used for PLC operation and which is also particularly suitable for operation on existing low-voltage power supply networks.

Claims

claims

1. A method for the transmission of data over a low-voltage power supply network with at least a first (1) and a second conductor (2), wherein a carrier signal is used for data transmission, the frequency of which is substantially above the mains frequency, characterized in that In a region of the low-voltage power supply network in which the two conductors (1, 2) are arranged essentially in parallel in the manner of a double line, the carrier signal is generated in a push-pull mode between the first conductor (1) and the second conductor (2) and that symmetrical impedances in the two conductors (1, 2) are provided in this network area in order to achieve electromagnetic shielding of this area of the low-voltage power supply network.

2. The method according to claim 1, characterized in that for the production of symmetrical impedances in the two conductors (1, 2) one or more electrical components (15, 25, 37, 38, 45) with predetermined impedances in an existing low voltage - Power supply network can be connected.

3. The method according to claim 2, characterized in that at least one of the electrical components (15, 25, 37, 38, 45) with predetermined impedance to an at least one on / off switching element (16, 36, 46) and / or Switching element (26) and / or a socket comprising house installation apparatus is connected.

4. Arrangement, in particular for performing the method according to one of claims 1 to 3, for the transmission of data via a low-voltage power supply network with at least a first conductor (1) and a second conductor (2), characterized in that the The arrangement comprises means for, in a region of the low-voltage power supply network in which the two conductors are arranged essentially in parallel in the manner of a double line, a carrier signal in one To generate push-pull mode between the first conductor (1) and the second conductor (2), the frequency of this carrier signal being substantially above the mains frequency, and means (15, 25, 37, 38, 45) for creating symmetrical impedances in the two Conductors (1, 2) in this network area in order to achieve electromagnetic shielding of the network area provided for data transmission.

Arrangement according to Claim 4, characterized in that the means (15, 25, 37, 38, 45) for creating symmetrical impedances have a capacitance, in particular a capacitor (15, 25) with a specific capacitance, and / or an inductance, in particular a coil (37, 38, 45) with a specific inductance.

Arrangement according to Claim 5, characterized in that the means (15, 25, 37, 38, 45) for creating symmetrical impedances comprise a bridging capacitor (15) which functions in parallel with an on / off switching element (16) in this bridging function , is connected to a branch conductor (11) provided with the on / off switching element (16), which is connected in the network area provided for data transmission to one of the two conductors (1) arranged in the manner of a double line.

Arrangement according to Claim 5, characterized in that the means (15, 25, 37, 38, 45) for creating symmetrical impedances comprise a bridging capacitor (25) which is connected in a bridging function between two branch conductors (23, 24) which alternately via a Umschaltgiied (26) in the for the

Network area used for data transmission are connected to one of the two conductors (1) arranged in the manner of a double line.

Arrangement according to Claim 5, characterized in that the means (15, 25, 37, 38, 45) for creating symmetrical impedances comprise at least one coil (37, 38) in the manner of a high-frequency choke, which is connected between a branch conductor (31, 32) and one of the two conductors (1, 2) arranged in the manner of a double line.

Arrangement according to claim 5, characterized in that the means (15, 25, 37, 38, 45) for creating symmetrical impedances comprise a ring core (45) made of ferrite material which encloses at least two branch conductors (41, 42), which are each connected in the network area used for data transmission to one or the other of the two conductors (1, 2) arranged in the manner of a double line.

Arrangement according to claim 9, characterized in that the two branch conductors (41, 42) are wound in the manner of a bifilar winding around the ring core (45) in order to form a toroidal core coil (45) which acts as an HF choke.