EP0509920A1 - Position signalling device of a movable component - Google Patents

Abstract

Device for signalling the status of an apparatus which can assume several discrete states and transmission of the corresponding information, characterised in that it comprises: - means for deriving, inside a shielded enclosure (4) a DC voltage which is free of fluctuations, the said shielded enclosure comprising within it: - a first means (5) for deriving, from the said DC voltage, electrical pulses of duration proportional to the value of an inductor (6), this inductor being capable of taking distinct values according to the various states of the apparatus, - a second means (8) for converting the said electrical pulses into optical pulses and an optical fibre (9) for transmitting these pulses out of the said enclosure to a processing unit (10). <IMAGE>

Description

The present invention relates to a device for signaling the position of a movable member.

The invention finds particular application in electrical engineering, and the present brief will be illustrated by an example which, of course is not limiting.

The example relates to signaling the position of the contacts of an electrical cut-off device, such as a circuit breaker. It is essential for the operator of a substation comprising devices such as circuit breakers, to know with certainty the state, open or closed, of the position of the contacts of each of the circuit breakers; this information, generally available at each of the circuit breakers, is centralized in a control and command station; it is imperative that any failure of the information transmission circuit which connects each of the devices to said station is immediately reported, otherwise the signal received at the station can make it appear that a device is in a given state while it is in the 'reverse state; this error may have unfortunate consequences for the operator of the electricity network.

For the same reasons, it is essential that the device providing the signaling signals itself, to a large extent, that it has failed or that its power supply has failed. This self-monitoring considerably increases the availability of the self-monitored part of the device.

Of course, the problem is not limited to detecting the position of the contacts of a circuit breaker; in electrical substations, this signal isation, also called signal contact, concerns the pressure switches, the oil pressure of the hydraulic control circuits, the oil levels, etc.

Out of 100 major electrical substation failures, around 30 are due to poor signal contact; we therefore understand the importance of the problem.

An object of the invention is therefore to provide a device for signaling the state of a device by detecting this state and transmitting the corresponding information, which is error-free operation possible on the detected condition, which immediately signals its own failure as well as that of the information transmission line.

Another object of the invention is to provide a device insensitive to external influences such as electric fields or magnetic fields as well as common mode disturbances encountered when using galvanic connections.

It is known that the supply by optoelectronic element, the transmission by optical fiber and the shielding of the device make it possible to meet the preceding requirement. We then come up against the problem of consumption of the device; another object of the invention is therefore to produce a device requiring for its operation no more energy than that available by means of a photovoltaic cell.

In US Patent No. 4,626,621, a circuit for determining the position of an object is described, comprising two LR circuits driven by a square signal from a pulse generator. One of the LR circuits has a fixed inductance, the other a variable inductance depending on the position of the object. The establishment of the voltages in the circuits is done, from an instant t1, according to different exponential laws in the two circuits, and the respective instants t2 and t3 corresponding to the establishment on the two circuits of a voltage of given value Vo. The ratio (t3 - t1) / (t2 - t1) provides a value corresponding to the position sought.

Such a circuit is complex since it comprises two LR circuits, two operational amplifiers, two counters, etc., and it does not make it possible to detect its own failures.

An object of the invention is to provide a circuit comprising the minimum of components, and, as already indicated, capable of signaling its own failures.

• des moyens pour élaborer, à l'intérieur d'une enceinte blindée, une tension continue exempte de perturbations, ladite enceinte blindée comportant à son intérieur:
• un premier moyen pour élaborer, à partir de ladite tension continue, des impulsions électriques de durée proportionnelle à la valeur d'une inductance, cette inductance pouvant prendre des valeurs distinctes selon les divers états de l'appareil,
• un second moyen pour convertir lesdites impulsions électriques en impulsions optiques et une fibre optique pour transmettre ces impulsions hors de ladite enceinte vers un centre de traitement.

The subject of the invention is a device for signaling the state of a device which can take at least two discrete states and for transmitting the corresponding information, characterized in that it comprises:

• means for developing, inside a shielded enclosure, a DC voltage free of disturbances, said shielded enclosure comprising inside:
• a first means for developing, from said direct voltage, electrical pulses of duration proportional to the value of an inductance, this inductance being able to take on distinct values according to the various states of the apparatus,
• second means for converting said electrical pulses into optical pulses and an optical fiber for transmitting these pulses out of said enclosure to a processing center.

In an exemplary embodiment, the means for developing a DC voltage comprise a photovoltaic element placed inside said shielded enclosure and illuminated through a window thereof by a light source. As a variant, the means for developing a DC voltage comprise an integrated photovoltaic cell placed inside said shielded enclosure and associated with an optical fiber supplied by a laser diode placed outside of said shielded enclosure.

In a particular embodiment, said first means comprises a circuit for developing rectangular pulses of constant duration and separated by equal time intervals, an integrator circuit receiving said pulses, a first threshold inverter circuit receiving the output signals of the integrator and supplying at the output of the calibrated pulses, a time constant circuit comprising a resistance and said inductance, the output signal of said first threshold inverting circuit being sent both to the input of said time constant circuit and on a second inverter circuit, the output signals of the time constant circuit and of the second inverter circuit being sent to the input of a third threshold inverter circuit, the output of which is connected to an amplifier supplying said second means.

Advantageously, said second means is a photo-diode.

The processing center includes a demodulation circuit and a self-monitoring circuit.

In a particular embodiment, said demodulation circuit comprises a photo-voltaic converter receiving the signal from said optical fiber, a Schmitt trigger and a MEMORY D type circuit.

Advantageously, the self-monitoring circuit comprises a circuit of the diode pump type, supplying an output transistor.

In an alternative embodiment, the self-monitoring circuit comprises an exclusive OR type circuit inserted by a first input upstream of said MEMORY D circuit and comprising a second input connected to a microcontroller capable of providing on this second input a test pulse of duration dt greater than the duration of said rectangular pulses, the microcontroller being connected to the MEMORY D circuit and being programmed to observe a change in position information during said time when the system is at rest.

• la figure 1 est un schéma électrique par blocs du dispositif de l'invention,
• la figure 2 est un schéma d'un mode de réalisation du circuit d'élaboration des impulsions de durée proportionnelle à une la valeur d'une inductance,
• la figure 3 présentent divers diagrammes expliquant le fonctionnement du circuit de la figure 2,
• la figure 4 est un schéma du circuit de contrôle et d'auto-surveillance,
• la figure 5 présente plusieurs diagrammes expliquant le fonctionnement des circuits de la figure 4,
• la figure 6 représente une variante de réal isation du système d'auto-surveillance.

The invention will be better understood from the description given below of an exemplary embodiment given by way of illustration and in no way limiting, with reference to the appended drawing in which:

• FIG. 1 is an electrical block diagram of the device of the invention,
• FIG. 2 is a diagram of an embodiment of the circuit for producing pulses of duration proportional to the value of an inductance,
• FIG. 3 presents various diagrams explaining the operation of the circuit of FIG. 2,
• FIG. 4 is a diagram of the control and self-monitoring circuit,
• FIG. 5 presents several diagrams explaining the operation of the circuits of FIG. 4,
• FIG. 6 represents a variant embodiment of the self-monitoring system.

In FIG. 1, the reference 1 designates a photovoltaic element, powered by a light source 2, for example a lamp powered by a battery 3. The photovoltaic element is placed in a shielded enclosure 4, the light passing through a window 4A; the photovoltaic element supplied by a voltage Vcc for example of 5 volts and capable of delivering 20 mA at peak; an electronic circuit 5, placed inside the shielded enclosure and supplied by the element 4, generates signals representative of the state of the device; for this purpose, the circuit comprises an inductor 6 consisting of a coil 6A and a movable core 6B linked to the movable element of the device, the position of which it is desired to know; the inductance 6 takes two different values depending on whether the core 6B is inside or outside the winding 6A, and takes on changing values in proportion to the penetration of the nucleus between the two aforementioned values. The electrical output signal from circuit 5 is converted into a light signal by an optoelectronic component 8 and routed by an optical fiber 9 to the signal processing station 10. There, an optoelectronic component 11 ensures the conversion of the light signal into an electrical signal which is received by an electronic processing circuit 12 supplying for example a signaling 13 and an alarm 14.

Thanks to the use of shielding, to the supply by a photovoltaic element and to the transmission by optical fibers, the measurements carried out are sheltered from all possible disturbances (in particular the absence of galvanic connection makes it possible to avoid any common mode voltage on the position transducer).

As a variant, represented by dashed lines in FIG. 1, the DC voltage is produced by means of an integrated photovoltaic cell 1A placed inside the shielded enclosure (this cell is for example an ASGA cell sold by the company SPECTEC ), connected by an optical fiber 4B passing through the wall of the shielded cell and supplied by a laser diode 3A.

In FIG. 2, the circuit 5 comprises a Schmitt trigger 20 receiving the voltage Vcc, and comprising a component 21, an adjustable resistor 22 and a capacitor 23; this trigger delivers at output A rectangular pulses whose rising edges are distant for example from 100 microseconds and whose duration is for example from 40 microseconds. (see Figure 3 A).

At the output of the trigger is placed an integrator circuit 30 which comprises a capacitor 31, a resistor 32 and a diode 33 making it possible to strongly attenuate the peaks due to the falling edges of the pulses (FIG. 3B).

The integrator is followed by an inverting element 40 with threshold s1 which supplies at output C, calibrated length pulses, for example 10 microseconds (FIG. 3C).

avec t* voisin de L/R3 et Imax voisin de Vcc/R3, la résistance du bobinage étant négligeable.In C, the signal is sent on a time constant circuit comprising the variable inductance 6, of value denoted L, and an adjustable resistance of value R3. The 3D curve shows, on its left side, the shape of the output signal of the LR3 circuit, at point D, when the inductance at a high value (core 6B inside the winding 6A); the 3D curve shows, on its right side, the shape of the signal in D when the inductance at a low value (core outside the winding). The difference in the shape of the curves is explained by the law for establishing the current i in a time constant circuit LR, which is: $$\text{i = Imax (1-exp-t / t *)}$$

with t * close to L / R3 and Imax close to Vcc / R3, the winding resistance being negligible.

The output signal of the inverter element is inverted by an inverter circuit 50 and the output signal at F (diagram 3F) is sent, together with the signal at D, to a threshold inverting circuit 60, the threshold of which s2 is shown in Figure 3D.

At the output of circuit 60, pulses of short duration (3 microseconds for example) are obtained when the inductance L is low (core out) and of longer duration (greater than 5 and less than 10 microseconds for example) when the value L is high (core retracted); these pulses are shown respectively to the left and to the right of the 3G diagram. The relation A makes it possible to show that if the threshold of the trigger is indeed constant, the width of the pulses is directly proportional to L / R3, therefore to L, since R3 is substantially constant.

The pulses at the output of circuit 60 are sent to a transistor 61 supplying, through a resistor 62, a diodeemissive 63, for example of the TI510 type from the company Hewlett Packard, connected to an optical fiber 64 which passes through the shield 4 and routes the information, in the form of light pulses, to a processing center.

The capacitor Cc, in parallel on the resistor R3, serves to compensate for the internal capacity of the winding.

In most applications, the device of the invention will be used to make "signal" contacts, so that only two inductance values will be required to determine two pulse widths. We will then use for the inductance a winding with a ferromagnetic core, for example mumetal in the form of a tongue; the two induction values will be determined by the fact that the ferromagnetic core will be in the winding or completely outside the winding. It is understood that this application is not limiting and that one could consider using more than two inductance values, with intermediate positions of the ferromagnetic core and thus determine more than two pulse durations.

FIG. 4 is a diagram of the control circuit for the position of the signal contact and of the self-monitoring operation circuit.

The optical signals emitted by the converter 63 of FIG. 3 are conveyed by an optical fiber 64 and transformed into electrical signals using an opto-electronic converter 65, for example a circuit R2501 from the company Hewlett Packard.

The output signals of the converter (point H in FIG. 4) are represented in diagram 5H in FIG. 5, in which two pulses of small width are shown on the left of the diagram and two pulses of large width on the right of the diagram. diagram.

The pulses are inverted by an inverter circuit 66; the output signal from circuit 66 (point J in FIG. 4) is represented in diagram 5J in FIG. 5.

The signal at J is addressed to a Schmitt trigger (for example a circuit 4093 from the company Radio Corporation of America, symbolized in FIG. 5 by a resistor r and a capacitor c; the output signal from the Schmitt trigger, at the point K of figure 4, is represented in diagram 5K of figure 5.

The signal at K is sent to a threshold reversing circuit 67, which can take a value Vcc or a value 0 as output; the signal switches from Vcc to 0 when the input signal exceeds a first threshold s3 and switches from 0 to Vcc when the signal crosses a second threshold s4 (s3> s4). The output signal (in M) of circuit 67 is represented in diagram 5M in FIG. 5.

The signal at M is sent to the 'DATA' input of a circuit 68 called 'MEMORY D' (for example a circuit 4013 from the company Control Data), whose input 'CLOCK' is connected to point M. This circuit provides on its output Q, at each 0-1 transition of the signal at M, a signal corresponding to the state of the "DATA" input. The corresponding signal, in the example chosen, is represented in the diagram 5Q of FIG. 5. Preferably, to supply the information "POSITION" of the contact, the complementary signal Q *, represented in the diagram 5Q * of FIG. 5.

• un transistor T à effet de champ,polarisé par une source continue Vcc à travers une résistance 70,
• une première diode 71 en série avec un condensateur entre le point J et la grille du transistor,
• un condensateur 73 et une résistance 74 en parallèle entre la base du transistor et la terre et,
• une seconde diode 75.

The demodulation circuit which has just been described is associated with a self-monitoring circuit of the signaling device of the invention. This self-monitoring circuit consists of a "diode pump" comprising, in a conventional manner:

• a field effect transistor T, polarized by a direct source Vcc through a resistor 70,
• a first diode 71 in series with a capacitor between point J and the gate of the transistor,
• a capacitor 73 and a resistor 74 in parallel between the base of the transistor and the earth and,
• a second diode 75.

The diagram in FIG. 5N shows the potential on the gate of the transistor, at N, which always remains greater than or equal to Vcc as long as the opto-electronic chain is working; the transistor then remains blocked.

If for any reason (disappearance of the light source, cut of one of the optical fibers, failure of an electronic component in the chain, including the diode pump circuit, etc.) the signal at J disappears , the voltage on the gate of the transistor T disappears by discharging the capacitor 73 in the resistor 74 and a signal appears at X on the drain of the transistor T. It will be noted that only the memory D partially escapes this self-monitoring.

FIG. 6 illustrates an alternative embodiment of the self-monitoring circuit.

Compared to the circuit of FIG. 4, it differs by the disappearance of the chain comprising the transistor T.

A circuit 90, of the exclusive OR type, comprising two inputs E1 and E2 and an output S, is inserted by its input E1 between the threshold inverting circuit 67 and the MEMORY circuit D 68.

A microcontroller mP, connected to the output Q * of the circuit 68 to acquire this information, is capable of sending on the input E2 a unit pulse "1" of duration dt> to. This pulse corresponds to the start of the self-monitoring and is designated in the following by test pulse.

We immediately observe the truth table below from circuit 90.

When E2 = 0, the exclusive OR copies the input E1 to S, so this additional circuit does not modify the information initially delivered in Q *.

On the other hand, we note that as soon as the test pulse is launched, E2 = 1. The software having checked that the system is in the rest state, no order having been launched, there must be mandatory replacement of Q * by Q *, whatever the initial value of Q *, if the return pulses from the transducer do exist. It is sufficient for this that the test pulse has a width slightly greater than t0, period of emission of the pulses.

*. Lorsque l'impulsion est coupée, le microcontrôleur mP ouvre une nouvelle fenêtre temporelle de durée dt. Dans cette deuxième fenêtre, il vérifiera que Q2 = $\overline{\text{Q1}}$

= Qo.To do the self-test, the program first notes the value Q * o of Q *, then it sets E2 to "1" during dt and checks that during this window dt, Q * has become Q1 = $\overline{\text{Q}}$

*. When the pulse is cut off, the microcontroller mP opens a new time window of duration dt. In this second window, it will check that Q2 = $\overline{\text{Q1}}$

= Qo.

By this procedure, and by a suitable choice of dt, the entire measurement chain is checked, including the MEMORY circuit D 68 and the gate 67 which escaped surveillance in the circuit of FIG. 4.

lorsque l'impulsion de test est lancée.Note that any failure of the OU exclusive 90 circuit will also be detected by self-monitoring, as it would result in the non-replacement of Q * by $\overline{\text{Q *}}$

when the test pulse is launched.

The self-monitoring can be periodic, with its own periodicity, or be part of the normal information capture cycle which is carried out by sampling with a given frequency.

Of course, the invention is not limited to the embodiments described and shown, which have been given only by way of example, in which the means or groups of means described can be replaced by means or groups of equivalent means.

Claims (9)

1 / Device for signaling the state of a device which can take several discrete states and transmitting the corresponding information, characterized in that it comprises: - Means for developing, inside a shielded enclosure (4), a DC voltage free of disturbances, said shielded enclosure comprising inside: a first means (5) for developing, from said direct voltage, electrical pulses of duration proportional to the value of an inductor (6), this inductor can take on distinct values according to the various states of the device, - a second means (8) for converting said electrical pulses into optical pulses and an optical fiber (9) for transmitting these pulses out of said enclosure to a processing center (10). 2 / Device according to claim 1, characterized in that the means for developing a DC voltage comprise a photovoltaic element (1) placed inside said shielded enclosure (4) and illuminated through a window thereof by a light source (2). 3 / Device according to claim 1, characterized in that the means for developing a DC voltage comprise an integrated photovoltaic cell (1A) placed inside said shielded enclosure (4) and associated with an optical fiber (4B) powered by a laser diode (3A). 4 / Device according to one of claims 1 to 3, characterized in that said first means comprises a circuit (20) for developing rectangular pulses of constant duration and separated by equal time intervals, an integrator circuit (30) receiving said pulses, a first threshold inverting circuit (40) receiving the output signals from the integrator and supplying output of calibrated pulses, a time constant circuit comprising a resistor (R3) and said inductance (L), the signal of output of said first threshold inverter circuit (40) being sent both to the input of said time constant circuit and on a second inverter circuit (50), the output signals of the time constant circuit and of the second inverter circuit (50) being addressed to the input of a third threshold inverter circuit (60), the output of which is connected to an amplifier (61) supplying said second means (8). 5 / Device according to one of claims 1 to 4, characterized in that said second means (8) is a photo-diode (63). 6 / Device according to one of claims 1 to 5, characterized in that said processing center (10) comprises a demodulation circuit and a self-monitoring circuit. 7 / Device according to claim 6, characterized in that said demodulation circuit comprises a photo-voltaic converter (65) receiving the signal from said optical fiber (64), a Schmitt trigger (r, c, 67) and a circuit MEMORY D (68). 8 / Device according to claim 4, characterized in that the self-monitoring circuit comprises a circuit of the diode pump type, supplying an output transistor (T). 9 / Device according to claim 7, characterized in that the self-monitoring circuit comprises an exclusive OR type circuit (90) inserted by a first input (E1) upstream of said MEMORY D circuit (68) and comprising a second input (E2) connected to a microcontroller (mP) capable of providing on this second input a test pulse of duration dt greater than the duration of said pulses rectangular, the microcontroller being connected to the MEMORY D circuit (68) and being programmed to observe a change in the position information Q * during said duration when the system is at rest.

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