FR2649267A2 - Enhanced device and process for transmitting information over an electrical line - Google Patents

Abstract

Process and device making it possible to transmit information over a line of an electrical power transmission network, for example for the remote monitoring of the operation of a bank of lights. In accordance with the main objective, transmission is permitted only when the line is unenergised, the enhancement consisting in transmitting the information in the form of pulses at low frequency and with subtantially zero average amplitude so as to make it possible to cross through transformers.

Description

IMPROVED TRANSMISSION DEVICE AND METHOD
INFORMATION ON ELECTRICAL LINE.

The present invention relates to a method and a device allowing the transmission of information on a line of an electrical energy transport network in accordance with the main title FR 8813268, these method and device being improved with a view to improving the quality and the reliability of the transmission.

In particular, the invention relates to a device, usable in combination with an electrical supply line to which at least one electrical equipment is connected, and suitable for allowing the transmission of information on this line from or to this equipment. , this device comprising for this purpose a central information communication station associated with the line and a peripheral information communication station associated with the equipment and being such that the central station and the peripheral station comprise a transmission block the operation of which is only authorized during periods of power off of the line, and that the peripheral station associated with the remote equipment comprises memorization means for storing at least one item of information, subject to evolution, which must be transmitted to the central station from said equipment or which is transmitted by the central station to said team is lying.

A device of this type is described in the main title
FR 8813268.

In such a device, at least one of the central station and the peripheral station comprises for example a DC voltage source and control means suitable for modulating, at low frequency, the voltage delivered by this source, to produce pulses representative of the information to be transmitted on the line.

Although this technique of transmitting information over de-energized lines overcomes the most important difficulties, a transmission problem persists in certain network configurations, in particular those comprising transformers. In fact, while the presence on these networks of non-negligible reactances encourages the transmission of information by low frequency modulation of a DC voltage, the simultaneous presence of transformers on these same networks can lead to considerable weakening and distortion of the signals. transmitted, due to the saturation of the transformers passed through and to the importance of the magnetizing current passing through them.

 In this context, the aim of the present invention is to provide the device mentioned above with means suitable for improving the quality and reliability of the transmission.

 To this end, the control means of the central station and / or of the peripheral station are designed to produce, whatever the information to be transmitted, pulses whose average amplitude, over at least certain time intervals, is substantially zero, these pulses having a frequency substantially lower than the operating frequency of the line.

 Preferably, the average amplitude of the pulse or pulses corresponding to each piece of information to be transmitted is substantially zero over the time interval corresponding to the transmission of this piece of information. For example, the pulse or pulses corresponding to each piece of information comprise a succession of at least two electrical states of different polarity but of symmetrical amplitudes, two different pieces of information being distinguished from one another by a difference in duration of these states or by a difference in their amplitude.

 According to this method, it is also possible to code an information element by a pulse of zero amplitude for a determined duration, such a pulse constituting an extreme case of bipolar pulse.

 It is also possible to provide that the pulse or pulses corresponding to each item of information comprise a succession of at least two electrical states of different polarities and of non-symmetrical amplitudes, two different pieces of information then being distinguished. on the other by a difference in the electric states which they comprise or in the order of appearance of these states.

 In all cases, two pieces of information can be separated by a time interval during which no signal is transmitted on the line.

 In the case where a transformer possibly present on the line has a significant hysteresis, the average amplitude of the pulse or pulses corresponding to each item of information to be transmitted is chosen to correspond to a zero flux in a transformer present on the line.

The invention also relates to a method for transmitting, on a power supply line to which a set of electrical equipment is connected, information subject to change respectively relating to or intended for this equipment, this method being usable with a line periodically put on or off, eb comprising an operation consisting in storing said information and an operation consisting in authorizing their transmission on the line only in the time intervals when the latter is off.

In the context of the invention, this method further comprises an operation of coding the information to be transmitted in the form of bipolar electrical pulses whose average amplitude is chosen to correspond, at least for all of the information to be transmitted, to a substantially zero flux in a transformer possibly present on the line.

Other characteristics and advantages of the invention will emerge from the description which is given below, for information only and in no way limitative, with reference to the appended drawings, among which:
FIG. 1 is a general diagram of a control and distribution cabinet, of the associated central station, of possible line departures and of links with the equipment to be monitored.

 FIG. 2 shows the different forms of voltage pulses U which can represent the information elements and the corresponding currents I as a function of time t, in the case of non-capacitive lines, including transformers assumed to be linear.

 Figure 3 shows the diagram of the central station switch block when the feeders are single-phase. It is identical to Figure 7 of the main title, except for step-down transformers.

 Figure 4 shows the diagram of the central station switch block corresponding to a three-phase feed.

 FIG. 5 shows the composition of the phases which can result from the transformers inserted on the main starting lines and from the transformer inserted in the routing block, as well as the different voltages appearing during a transmission. For the sake of clarity, the transformation ratio has been reduced to 1 for the drawing of this figure.

 FIG. 6 describes a possible embodiment for a transmission block from the central station or from a peripheral station.

 FIG. 7 describes a possible embodiment for a reception block of the central station or of a peripheral station.

The device of the invention allows the transmission of any type of information between a central sending station (1) (see
Fig. 1) included in or located in the immediate vicinity of a control and distribution cabinet (2) and answering machine peripheral stations (3), each having a personalized call code, inserted in the branches which supply the equipment to be monitored or control (4), connected in parallel on electrical lines (5-1, 5-2), these lines may include transformers (6-1, 6-2) interposed in the connection with the control and distribution (2) .The essential function of the latter is to insert contacts (/ -1, T-2) between the energy supply line (8) and the line feeders (9-1, 9- 2), controlled by an external process via actuators (10). In an application envisaged primarily, the device now allows, with the improvements described, remote monitoring of a lighting network called "Medium voltage" comprising a set of luminaires (4), distributed over low voltage power lines (5), low voltage / medium voltage transformers (6), the "on" or "off" state of which is controlled by the medium voltage control and distribution cabinet (2), the information relating to the state of the various luminaires (4) being directly conveyed by these lines. The improved device nevertheless continues to apply to the initial configuration devoid of transformers, when the control and distribution cabinet is supplied by a low voltage network. The central station includes, as in the past, a power supply unit (11), responsible for generating the auxiliary voltages and their possible backup, a reception unit (12) detecting the signals present on the line, a logic control unit. and interpretation (13), managing the recognition of the codes detected by the reception block and driving the transmission block (14) whose task is to transmit the signals requested by the control block (13). A switching block (15) switches the internal line PN to the external line to be monitored or to that which gives the best signal, as explained below.

 The central station may or may not be connected by an optional link (16) to a monitoring station which concentrates and uses the data collected by one or more central stations.

 The possible transformers (6) inserted on the line prohibit the transmission by pulses of direct voltage as soon as the latter reach saturation. In addition, the intensity of magnetization allowing the flux to continuously increase rapidly reaches values which correspond to high powers.

 To overcome these particular constraints, the transmission method of the invention comprises the emission of sequences of pulses of direct voltage on the line when the latter is no longer supplied, the average value of which is almost zero, 1 objective being to obtain at the end of transmission a zero flow in the transformers (6) possibly present on the line. Each pulse also has a duration and an amplitude such that it in no case saturates the magnetic circuit of the transformer. The theoretical limit of the voltage product duration of the pulses is of the order of a volttsecond when the latter are emitted on the low voltage side of the transformers, here assumed to be calculated for a nominal voltage of 220 Volts at 50 Hz. In practice, much lower values. This process makes it possible to work with very highly capacitive lines, including high power transformers, but it can also be used on lines which do not have these characteristics. FIG. 2 describes different forms of voltage pulses U which can be used in the context of this improvement and the corresponding currents I emitted to obtain them, as a function of time t, assuming a zero charge on the line, other than the transformers.

 The pulse shapes 17a, 17b and 18a, 18b allow a discrimination of the information elements (bits for example by the width of the pulses, these being symmetrical, the shape of the pulses 18a, 18b also introducing a duration during which the line potential is forced to zero, between the transmission of two pieces of information, so that the individual flux of each transformer can continue to decrease. The shapes 19a, 19b and 20a, 20b are asymmetrical, separated by a zero potential, the information elements being respectively distinguished by the first polarity or the duration of the first polarity appearing.The shapes 22a, 22b and 21a, 21b are identical to the previous ones, but without separation by a zero potential. 23a to 23c and 24a to 24c correspond to pulses, one of which 23b, 24b, of zero amplitude for a certain duration, describes an element of information, the other e being described by a symmetrical pulse 23a, 23c, or asymmetrical 24a, 24c.

 The duration of the pulses is chosen according to the networks between 20 and 400 ms, with the lowest possible voltage U compatible with good reception, so that the maximum current I is at most of the order of 1 Ampere, between others to stay within reasonable cost of completion areas.

 To fix the orders of magnitude in the case of a public lighting network supplied with medium voltage comprising for example 4000 homes of 150 Watts, the capacitive load of the network is of the order of 0.05 Farad. Assuming that the current emitted or absorbed by the emission blocks is limited to one Ampere, the rise and fall times of the pulses will be of the order of 20 Volts per second, or approximately 5 milliseconds to reach the level of emission also fixed at 100 millivolts.

Given this value, a pulse polarity duration can be fixed at around 50 milliseconds, which corresponds to a product voltage and duration of 0.005 volttseconds.

The nominal current of the assembly being approximately 3000 Amperes (220 Volts side), the no-load current necessary to obtain 220 Volts on the secondary of a transformer of this line can be estimated at 100 effective Amperes (150 Ampere peak for a excitement of iV * s). An excitation of 0.005 volttsecond will therefore correspond to maximum intensities of less than 0.05 amperes, the no-load current of the transformers decreasing faster than the voltage, because the magnetic permeability of the sheets increases when the magnetic excitation decreases.

 The minimum environment necessary for the invention is identical to that described in the main title.

 If the general organization remains the same, the functional nature of three blocks can be changed. These are the central station switching block (15), the transmission blocks (14) (central station and / or peripherals) and reception blocks (13) (central station and / or peripherals).

 As will be understood by those skilled in the art, the sequences described in the main title for the recognition of the information elements will be adapted to the new coding adopted in this improvement of the process, without the functional nature of the blocks concerned being affected.

In particular, because of the greater number of devices connected to this type of network, the coding of the peripheral stations will be carried out on more than eight bits.

BLOCK FUNCTION
NEEDLE BLOCK (15)
In the case of single-phase medium-voltage feeders (see
Fig. 3), the function of this block comprises, in addition to the switching function described in the main title, a function of lowering the voltage to a value making it economical to produce the central station, for example 110 or 220 Volts, ( transformer (29)), but the need for which is not functional.

 If on the other hand the medium-voltage feeders are three-phase, and if the transformers present on the line have a coupling and a type making possible the separation of the three channels each corresponding to a set of low-voltage single-phase feeders from transformer stations interposed between the feeders and equipment, the block ensures this separation prior to the referral function, which brings us back to the previous case.

 If, in the case of three-phase feeders, the separation cannot be done by combination of windings (see Fig. 4>, the block integrates the logic necessary for the optimum signal extraction by determining the channel which restores the best level and by routing it on the internal line, after a step-down transformer (30).

 Indeed, as shown in Figure 5, if one excites a channel u, the line (5-2) for example, the physical laws which govern the behavior of the transformers make that one will observe, in the chosen example two pulses v and w on the other channels (5-3) and (5-4), of half amplitude and of reversed polarity.

 It will be the same at the terminals ul, vl, wl, of another transformer connected on the same RST line, if its connection is identical, for example the transformer (30) of the switch block (15).

 In the case mentioned above, since the transmission can reverse the polarity of the pulses, it is preferable not to choose the pulse forms (19) and (22) where the discrimination of the information element takes place. on the first polarity to appear.

TRANSMISSION BLOCK (14):
The emission block described in the main title allows the function to be performed, but only under certain specific conditions (line characteristics, shape of the signals, uniform direction of the current). The object of the present improvement is therefore, inter alia, to propose an improved architecture for this emission block, allowing a reversal of emission current and consequently, the production of all the signals described in FIG. 2, whatever the characteristic of the line.

 On the basis of the orders transmitted to it by the control unit of the central station (13) or of the peripheral station, in the form of duration, value and pulse polarity for example, the emission block controls, during this duration, output voltage injected on the internal PN line at a predetermined value, chosen according to the specific characteristics of the starting lines, from a few standard settings. This block is inhibited in the event of a mains presence. The elaboration of the instructions by the control unit is naturally adapted to the signals chosen and respects the conditions which are the subject of the improvement.

RECEPTION BLOCK (12):
The receiving block monitors the state of the internal line
PN, filters the waves received and restores the polarity and the level of the pulses it detects on the internal PN line to the control unit of the central station (13) or of the peripheral station. This block also ensures the detection of the presence of the sector on the internal line to inhibit the transmission block (14).

 As part of this improvement, this block can advantageously consist, for its reception part, of one or three analog / digital converters physically integrated in a microcontroller managing the control blocks.

REALIZATION OF BLOCKS
NEEDLE BLOCK (15):
Figures 3 and 4 describe two variants of a switch block. A decoder (25) receives the routing orders from the logic control block of the central station (13) by the link (26>. Through amplifiers (2F) it controls relays (28) whose function is to put the PN internal line in communication with either single-phase feeder lines such as (9-1) through a single-phase step-down transformer (29), or with a phase from a three-phase step-down transformer (30) also connected to a feeder three-phase (9-2), denoted RS T. One of the relays has the function of putting a resistor (31) in parallel on the internal line, the function of which is to improve the damping of the line. 32), it is activated either by a specific order or as soon as any switch is selected As will be understood by those skilled in the art, the transformer (30) can be composed of three transformers (29) suitably connected; similarly, a referral block can include both single-phase and three-phase ts. In the case of three-phase feeders, it is advantageously but not necessarily possible to provide a discriminator (33), preceded by a filtering and clipping cell (34) which determines the line having the best level in reception. towards a luminaire, the switch block arbitrarily chooses the first switch of the start.

Upon reception, the discriminator will identify the best channel and transmit the "channel number" information via the link (26) to the central station which will store it in order to interrogate the luminaire concerned in the future.

In the event of non-response or error in the response, the central station will order the switch to the other possible lines.

 After this learning phase, which occurs only at the start of a new installation, or after a memory loss (backup battery discharged for example) the discriminator only checks if the memorized channel is still the right one and rectify the memory of the central station if necessary, which makes it possible to adapt to changes in the network structure, occasional or permanent.

 The membership of this discriminator (33) in the switching unit is only of a functional nature. It can be three channels of an analog to digital converter integrated in a microcontroller managing the central station.

OMISSION BLOCK (14):
The emission block described in FIG. 6 is very similar in principle to that described in the main title.

The difference is essentially the possibility of emitting or absorbing current in the phase of regulation of the output voltage associated with the possibility of putting the block in high impedance state (no voltage control). To this end, the output stage is symmetrical, formed by the transistors (35), (36), (37), the diodes (38), (39) and the resistors (40) and (41) on the V + side. (current emission) and by the transistors (42), (43), (44), the diodes (45), (46) and the resistors (47) and (48) on the V side (current absorption). The transistor (37), respectively (44) ensures the limitation of the current in the power transistor (35) respectively (42), the latter being preceded by a transistor current amplification stage (36) respectively (43)) The diodes (38) and (45) protect the respective transistors from reverse polarity, while the diodes (39) and (46) evacuate the leakage currents of the diodes (38) and (45).

The value of the resistors (40) and (47) determines the current limitation threshold, the reference potential being that of the emitter voltage base of the transistors (37) and (44). The bases of the transistors (36) and (43) are connected to the output of the operational servo amplifier (49) by the resistors (50) and (51) respectively. The switching on of the transistors (52) and (53) puts the output stage in a high impedance state. This is controlled by inputs (54) and (55); 1 is activated in the event of mains presence, while the other is deactivated only during the transmission of the messages transmitted by the block, through the transistor (56). The principle of the servo is identical to that described in the main title. The control block delivers to the input (57) the inverse of the desired output signal and deactivates the blocking of the output stage simultaneously by (54 ). The resistors (58) and (59) determine the gain of the device, while the resistance (60) and the capacitor (61) determine the frequency from which the integral correction occurs. If the availability of the components requires it, in particular for the transistor (35) which is a PNP which must support the network voltage, the PN line of the transmitter block can be connected to the internal line through a transformer. As a variant, the current transmission part can be produced with NPN transistors preceded by an isolation stage (specialized amplifier, pulse transformer, etc.). This block is supplied by two voltages V + and V- whose common point is connected to the line
N. These voltages come from the Power Supply
RECEPTION BLOCK (12):
An exemplary embodiment of a reception block in the case of a pulse transmission of constant voltages and alternating polarities is described in Figure 7. It is common to the central station and to the peripheral stations. It essentially consists of a signal detection function and a safety function, detecting high voltages on the line, in particular the presence of the sector, but also an incomplete discharge of the line capacities.

 This block is supplied by two voltages V + and V-, the common point of which is connected to line N. These voltages come from the Power Supply block.

 The lines P and N are respectively, as for the transmission block, the phase and the neutral of the internal line of the central or peripheral stations.

For the signal detection function, the resistor (62) takes the signal on the line P, the capacitor (63) and the two diodes (64) and (65) ensuring filtering and clipping. The amplifier (66), mounted as an adjustable gain follower by the resistors (67) and (68) is an impedance reducer; there is at its output the filtered line signal, normally not clipped, except in the event of a mains presence on the line. To restore the transmitted pulse, this signal is compared after possible amplification to two references, one positive, the other negative, by the comparators (69) and (70). In this example, the reference potentials are given by the chain formed by the resistor (71), the diode (72), the diode (73) and the resistor (74), connected between V + and V-, with the common point of the two diodes connected to the common of the power supplies. Other combinations are possible if the threshold voltage must be different. For the sake of stability, the comparators are each equipped with a network of resistors (75) and (76) for (69), (77) and (78) for (70), giving hysteresis to the tilting voltages, centered around of the reference potentials. We will therefore have at the output (79) of the comparator (69) a voltage V + when the line potential is lower than the reference voltage, and V- otherwise, except for the hysteresis. , and at the output (80) of the comparator (70) of a voltage V + when the line potential is less than the negative reference voltage, and
V- in the contrary case, always with the hysteresis near
The signals are possibly reversed by (81) and (82), before being transmitted by the links (83) and (84> to the logic control block of the central station or of the peripheral station as the case may be.

 If an ar logical / digital converter architecture has been chosen for the realization of the discriminator of the turnout block, the sub-assemblies (85) (clipping) and (86) (threshold comparators) may be materially identical to the assemblies (34) and (33 ) of the referral block, the referral function then being of a software nature for the reception part. In this case, we can consider a more sophisticated signal processing algorithm than the simple monitoring of a threshold.

 For the sector detection function, the resistor (87) takes the signal on the line P, the dipole (88) ensuring an attenuation of the order of 10 and a clipping. At its terminals there is attenuated line voltage, normally not clipped except in the event of mains presence on the line. As the comparators (89) and (90) compare this signal to the same two references as above, as moreover these reference voltages are chosen at around 25% of the voltages emitted by the transmission block, the comparators normally have the output "in the air" during normal transmissions, These two comparators have "open collector" outputs, so that their connection constitutes a logical "OR". If the sector would pair, according to its polarity, one of the two comparators will switch, forcing the common output to V- and discharging the capacitor (91) through the resistor (92). When the mains voltage goes to zero, for a few hundred microseconds, neither of the two comparators will be active. On the other hand, we will continue to observe the same potential on the common output, the resistance (93) being of high value to determine with the capacitor t91) a time constant of the order of a second. If even the output returns to the high logic level at this time, there will be no risk of destruction of the corresponding transmitter because at this time the line voltage will be low. An inverter (94) attacks the link (54) which will inhibit the transmission block and possibly give the information of presence of mains voltage to the control block.

Claims (8)

1. Device, usable in combination with an electrical supply line to which at least one electrical equipment is connected, and adapted to allow the transmission of information on this line from or to this equipment, this device comprising in this end a central information communication station associated with the line and a peripheral information communication station associated with the equipment and being such that the central station comprises a transmission block whose operation is only authorized during the line power-off periods, and that the peripheral station associated with the remote equipment comprises memorization means for storing at least one item of information, subject to change, which must be transmitted to the central station from said equipment or which is transmitted by the central station to said equipment, according to claim 1 of the main title, characterized in that at least one of the central station and the peripheral station comprises a source of direct voltage and control means capable of modulating, at a frequency substantially lower than the operating frequency of the line, the voltage delivered by this source, to produce pulses representative of the information to be transmitted on the line, and in that these pulses have an average amplitude substantially zero, over certain time intervals at least, whatever the information to be transmitted on the line. 2. Device according to claim 1 above, characterized in that the information to be transmitted being formed from a series of pieces of information, the average amplitude of the pulse or pulses corresponding to each piece of information to be transmitted is substantially zero over the time interval corresponding to the transmission of this element of information. 3. Device according to claim 2, characterized in that two successive pieces of information are separated by a time interval during which no signal is transmitted on the line, the latter being forced to a zero potential. 4. Device according to any one of the preceding claims, combined with claim 2, characterized in that the pulse or pulses corresponding to each piece of information comprise a succession of at least two electrical states of different polarities but of amplitudes symmetrical, two different pieces of information being distinguished from one another by a difference in the duration of these states or by a difference in their amplitude. 5. Device according to any of claims 1 to 4, combined with claim 2, characterized in that the pulse or pulses corresponding to each piece of information comprise a succession of at least two electrical states of different polarities and d 'non-symmetrical amplitudes, two different pieces of information being distinguished from one another by a difference in the electrical states which they comprise or in the order of appearance of these states. 6. Device according to any one of the preceding claims, combined with claim 2, characterized in that the average amplitude of the pulse or pulses corresponding to each item of information to be transmitted is chosen to correspond to a zero flux in a transformer possibly present on the line. 7. Method for transmitting on a power supply line to which a set of electrical equipment is connected, information subject to change respectively relating to or intended for this equipment, this method being usable with a line periodically energized or de-energized , and comprising an operation consisting in storing said information and an operation consisting in authorizing their transmission on the line only in the time intervals when the latter is switched off, according to claim 9 of the main title, characterized in that '' it further includes an operation of coding the information to be transmitted in the form of bipolar electrical pulses whose average amplitude is chosen to correspond, at least for all of the information to be transmitted, to a substantially zero flux in a transformer possibly present on the line. 8. Method according to claim 7, characterized in that an information element is coded by a pulse of zero amplitude for a determined duration.