EP0077249A1 - Chronometry method, centralized management system using this method and its application to the detection of leaks in a fluid transport network - Google Patents

Abstract

1. A method of relative chronometry of events detected by stations which are remotely located from a central managing post, the stations being connected by transmission lines to said post, characterized in - that in the central post, time reference signals are generated and simultaneously transmitted to the stations, the time interval between two said successive signals defining time units of a duration which is by far longer than the cycle duration of interrogations-replies of the central post to all the stations ; - that in each station, a first counter is initialized by the received reference signal, that by means of a clock counting pulses are delivered simultaneously to said first and a second counter, that the second counter is charged with the contents of the first counter as soon as the second counter has reached its maximum capacity, this capacity being greater than the maximum number of counting pulses in a time unit, that to each event, time data are associated which are constituted by the contents of the second counter at the moment of the detection of the event, and by an information concerning the removal of ambiguity and having different states at the beginning and at the end of a time unit, and that the information relating to the event, together with corresponding time data, are transmitted during the interrogations of the stations by the central post, - and that in the central post, the received informations are allocated with supplementary time data corresponding to a time unit number.

Description

The invention relates to operating assistance systems having a centralized management station and more particularly relates to a method and a system for developing and transmitting information making it possible to establish the relative timing of events which have occurred. in different stations managed by the centralized management station.

A large number of operating assistance systems, for networks of all types, are constructed on the following scheme: control and / or command stations are dispersed for controlling an entire network. Each of these stations is connected by an information transmission channel to a central station intended for centralized management of the network; the stations have no links with each other but can cover adjacent areas and transmit information linked to the same event or to events related to each other to the management center.

The problem which then arises in the management center is to date the events which have occurred in the different stations in relation to each other and in relation to a common time reference. This problem occurs in most industrial installations, for example in fluid transport installations, as well as in surveillance installations.

An obvious solution is to establish the timing of events from an absolute time reference. The implementation of this solution is difficult because it imposes the same precise time reference in all the stations and in the management station, which can only be obtained by transmitting resynchronization messages from the reference station. which can possibly be long.

Another solution consists in establishing the chronometry in one place, the central station having the time reference, with repatriation of all the information in this place as soon as it is captured. This can only be achieved by providing a network of transmission lines. transmission connecting each of the stations to the central management station, this additional network having only this function. This solution is expensive.

The subject of the invention is a method for preparing and transmitting information for the establishment of a relative timing which does not have the drawbacks mentioned above, and which in particular can be implemented in systems of operating aid already existing without introducing additional transmission lines.

• - dans le poste central à élaborer et à transmettre simultanément aux stations un signal de référence de temps quasi-périodique, définissant des unités horaires de durée très supérieure au temps de cycle d'interrogations-réponses du poste central à toutes les stations ;
• - dans chaque station à réinitialiser, à chaque unité horaire un premier compteur par le signal de référence reçu, à compter simultanément des impulsions de comptage de rythme donné dans ce premier compteur et dans un second compteur, à charger par le contenu du premier compteur, le second compteur lorsque ce dernier a atteint sa capacité maximum, cette capacité maximum étant supérieure au nombre maximum d'impulsions de comptage dans une unité horaire, à affecter chaque évènement détecté de données horaires constituées du contenu du second compteur lors de la détection de l'évènement et d'une information de levée d'ambiguité ayant des états différents au début et à la fin d'une unité horaire, et à transmettre lors des interrogations des stations par le poste central les informations relatives aux évènements avec les données horaires correspondantes ;
• - et dans le poste central à affecter les informations reçues d'une donnée horaire supplémentaire correspondant à un numéro d'unité horaire.

According to the invention, a method of relative timing of events detected by stations distant from a central management station to which they are connected by transmission lines, is mainly characterized in that it consists:

• - in the central station to develop and simultaneously transmit to the stations a quasi-periodic time reference signal, defining hourly units of duration much longer than the interrogation-response cycle time from the central station to all the stations;
• in each station to be reset, at each hourly unit a first counter by the reference signal received, to count simultaneously counting pulses of rhythm given in this first counter and in a second counter, to be loaded by the content of the first counter, the second counter when the latter has reached its maximum capacity, this maximum capacity being greater than the maximum number of counting pulses in an hourly unit, to be allocated to each detected event of hourly data consisting of the content of the second counter during the detection of the event and ambiguity clearing information having different states at the start and end of a time unit, and to transmit during station interrogations by the central station information relating to events with the corresponding time data ;
• - And in the central station to assign the information received from an additional hourly data corresponding to a time unit number.

The invention also relates to a system intended for the implementation of this method.

The invention also relates to the application of this system to the detection and rapid localization of leaks in a fluid transport network.

• - la figure 1 représente schématiquement un système d'aide à l'exploitation à gestion centralisée selon l'invention ;
• - la figure 2 représente, en détails, une partie d'une station éloignée de ce système ;
• - la figure 3 représente un chronogramme de l'évolution du contenu des compteurs.

The invention will be better understood and other characteristics will appear from the following description with reference to the appended figures:

• - Figure 1 schematically shows an operating assistance system with centralized management according to the invention;
• - Figure 2 shows, in detail, a part of a station remote from this system;
• - Figure 3 shows a timing diagram of the evolution of the content of the counters.

For the development of a relative chronometry, time references are transmitted from the management center to the stations, and the latter date the information captured by transmitting with this information hourly data derived from these time references.

In the operating assistance systems of the type described above, certain procedures are common to all the stations and controlled from the management center by a general order, that is to say intended simultaneously for all the stations. To this end, each station is capable of decoding, in addition to its own address used for the transmission of orders which are only intended for it, a general address used for the simultaneous transmission of a single general order to all stations.

In a first step of the method according to the invention, this general order function is used to transmit to all the distant stations an order of synchronization of local time bases, this order constituting the time reference common to all the stations for an interval of time determined by the interval between two successive synchronization orders. When the differences in propagation time of this general order, between the management center and the different stations, are greater than the desired precision, an additional offset intended to compensate for these differences can be achieved at each station; this compensation linked to the geographical location of the different stations in relation to the management center is pre-established and stored in each station.

The information concerning the events detected in an area covered by a station is transmitted by the normal link between station and management center, but it is transmitted with hourly data supplied by the local time base; thus they can be stored a certain time before their transmission in order not to interrupt a priority procedure in progress. These local time bases are synchronized, as indicated above. This synchronization is carried out by a periodic general order which depends on the desired precision, but this periodicity is not a characteristic of the system and the general order can be delayed with respect to its normal maturity when the management center is being processing another procedure.

To prevent information from being lost when the general synchronization order arrives at the station at the time when it has to date an event that occurs, a local time base with specific structure is provided in each station which includes a clock associated with a double counter, the first reset to zero by the general synchronization order, the second, of capacity greater than the maximum period between two resets to zero by two consecutive general orders, is automatically loaded by the content of the first when it reaches its maximum capacity. The content of this second counter is the first time information which is stored with the information to be transmitted concerning an event.

Given the chronometry method described above, between two resets of the first counter, the content of the second can pass twice through the same series of values. To resolve this ambiguity, the method according to the invention consists in transmitting, in addition to the first hourly datum, a second datum intended to resolve the ambiguity. Finally, in the management center, the information received is stored with the corresponding received time data and with additional information produced in the management center itself setting the corresponding time unit (between two synchronization orders).

In a preferred mode, the method for preparing and transmitting chronometry information comprises an additional step after each synchronization which consists in preparing and transmitting to the management center additional reporting information to notify it that synchronization has been completed. This information can be transmitted by change of signaling state.

The description which follows relates to the means for implementing the method described above in an operating aid system such as that shown in FIG. 1.

The operating assistance system represented in this figure comprises a management center, PC, connected by bilateral transmission lines T ₁ , T ₂ , T ₃ ... to stations S ₁ , S ₂ , S3. .. dispersed, for the control and command of a network, for example a pipeline. In the diagram in FIG. 1, the management center PC and one of the stations SI have been detailed in an exemplary embodiment.

Each remote station includes information sensors, c ₁ , c ₂ , c3 giving network state characteristics. The information is transmitted to a processor p ₁ (for active stations) which stores (and possibly processes) the information, and transmits it during an interrogation by the management center to a modulator-demodulator, m ₁ . The output of this modulator-demodulator provides the information to be transmitted on the transmission channel T ₁ connected to the management center.

The PC management center includes a modulator-demodulator M which receives the information transmitted by the remote stations and transmits it after demodulation to a processor P ₁ . In the system shown, the processor P _l manages the transmission of the data received from the stations which it transmits to a random access memory, MV, or to the associated operating means, ME, while a second processor P ₂ manages the means operating from data stored in memory MV and orders, entered by an operator; a printer I, which is an example of an operating aid unit, has been shown in this figure as a peripheral of the processor P ₂ . Other processors can also be provided for additional processing, as well as other memories. Furthermore, the station S ₁ , which is active, includes the processor p ₁ , but other stations may be only passive and not include a processor.

In such a system, for the preparation and transmission of timing information, each station includes a timing circuit, CH ₁ for the station S ₁ . The function of this timing circuit is to date the information transmitted by the sensors c ₁ , c ₂ , c3 ... when it appears, the dated information then being transmitted via the processor p ₁ , the modem m, and the line of normal transmission T ₁ to the central PC management station.

FIG. 2 represents the detailed diagram of an embodiment of this chronometry circuit CH ₁ . It includes a clock 10, the output of which is connected to the counting input of the two counters 11 and 12. In practice, the clock can be made of a quartz associated with a series of dividers to obtain the desired counting rate. One of the counters, 11, is synchronized by resynchronization ticks transmitted by the central management station PC to all the stations simultaneously, by a general order. In practice, this synchronization consists in zeroing the counter 11. For this, the synchronization order applied to the input E _RESET of the chronometry circuit is transmitted via a shaping circuit 13 to the reset input to zero, RESET, of counter 11. This signal is also applied to the control input of a report loop, 22, which performs a change of state of the output S _CR for transmission to the central station in order to indicate that the reset has been completed. The second counter 12 counts at the same time as the first but progresses to its maximum counting capacity which is greater than the maximum number of pulses at the frequency of the clock 10 between two successive resets of the counter 11. When this counter 12 has reached its maximum capacity, an impulse is supplied to the output D of this counter and applied to the reading input L of the counter 11. The parallel outputs of this counter 11 are connected to the parallel inputs of the counter 12, this the latter is loaded by the content of the counter 11 at this instant and then continues to count from this new initial value, which is always different from zero. The parallel outputs of the counter 12 give a time reference at any time to a first entry of time data from a memory 14.

To resolve the ambiguity when an event is affected by hourly data belonging to a series reproduced twice in an interval between two resets of the first counter, the chronometry circuit further comprises a rocker, 21, the input of which is connected to the output of the shaping circuit 13, a pulse supplied to this input causing the output of this flip-flop at state 1. This flip-flop has a reset input connected to the output D of the counter 11. The output, SA, of this flip-flop is connected to a second time data input from the memory 14.

Furthermore, the sensors c _l , c 2 c3 associated with this station supply the signals which they detect to shaping circuits, respectively 15, 16 and 17. The outputs of these circuits are connected to the input of a filtering circuit 18, the output of which is connected to an input for taking account of memory 14, which when it receives a pulse stores the content of counter 12 present at the first time data input and a information bit corresponding to the state of the second time data entry. These data are transmitted to the output of the chronometry circuit for storage, with the corresponding information in the station's processor, then transmission to the management center.

By way of example, if a current precision of the order of 10 ms on the time bases of the stations is sufficient, the chronometry circuit must not introduce an error greater than 10 ms on the hourly data transmitted. For this, a maximum duration of 10 ⁶ ms or sixteen minutes and forty seconds must be provided between two synchronizations. By choosing the counting frequency equal to 100 Hz (period 10 ms), a counter counting capacity equal to 2 ¹⁶ either 65536 or 655 360 ms, and a general resynchronization every 600,000 ms, or every ten minutes, the desired precision is obtained.

The hourly data at the output of the counter 14 are therefore coded on 16 bits. In a system where the information transfer buses have 8 bits, the timing circuit further comprises a multiplexer 20 which transfers the contents of the memory in two bytes, the first transmitted on order 0 and the second immediately after on order 01. The state of the ambiguity removal signal SA can be stored in a bit of the byte reserved for entering the event, this entry generally not occupying 8 bits.

The transmission of state change information from the sensors of a station is controlled by the management center. In an exemplary embodiment, the processor of a station p _l can store in its processing stack 21 bytes. If it is assumed that the information coming from a sensor occupies three bytes as indicated above, it is possible to acquire the data corresponding to 7 information coming from the sensors between two interrogations of the station by the central station of management.

With regard to the station itself, the information from the sensors is read every 20 ms for example and detected by variation of state during two consecutive periods. The minimum interval for detecting information from the same sensor is therefore 40 ms. Consequently, if events occur and are detected by several sensors from the same station in a slot less than 40 ms, they are associated with the same time information. On the other hand, they are associated with the time information corresponding to their arrival if they are offset by more than 40ms.

• (0, 65536), (5537, 65536), (537, 65536) etc...

FIG. 3 represents, for the capacities of the counters indicated, above the evolution of the content Cp _C of the counter of the management center; those C ₁₁ and C ₁₂ of the two counters 11 and 12 from an instant when their contents are equal to the same value 4000 and the signal SA. The first reset of counter 11 is carried out at its normal expiry, that is to say ten minutes after the previous one, when counter 11 has reached the content 60000. The second counter 12 continues to count until 65536. During of the next clock pulse, it is loaded by the content of the first counter, then at 5537, then it continues to count from this new initial value. The second reset to zero of the first is assumed to be carried out later, when the content of counter C ₁₁ reaches 65000. The second has not yet reached its maximum capacity and continues to count as in the previous period until 'to 65536. On the next impulse it is loaded by the content of the counter 11, C _11, ie 537 and counts from this new initial value. The time information that will be transmitted with the corresponding status information will therefore belong to the following intervals:

• (0, 65536), (5537, 65536), (537, 65536) etc ...

Between the two resets, defining in a counter of the management center, the hourly unit of number n, the references between the values before initialization 60000 and 65000 appear twice. The two-level signal SA gives the information which removes the ambiguity.

In the processor P ₁ of the central management station PC, the content C _PC of the modulo counter 10mn (normal value of the counting time in the stations) commands, at the end of each 10mm cycle, the issuance of the order general synchronization and the increase of one unit of the content of this capacity counter 144. As indicated above, when a priority procedure is in progress, the transmission of this general order can be delayed as much as possible until that the counter 11 reaches its maximum capacity. Indeed, it is automatically reset to zero if it reaches this value. In return, the information arriving at the management center is stored there with on the one hand the hourly data transmitted with them, which fix the time in an hourly unit of approximately 10 minutes, and on the other hand the value of the counter the management center setting the corresponding time unit among the 144 units forming 24 hours.

There is no ambiguity on the allocation of time units to the information received from the stations because the response interrogation cycle of all the stations by the management center has a duration much less than the time unit and that these interrogations have priority over the issue of the general synchronization order.

The processor P ₂ of this same management center can control the printing of the results, that is to say the appearances of the events with the corresponding times, classified in the order of appearance in the different stations, for example for facilitate the recognition of events linked to each other.

The invention applies to all telecontrol or remote monitoring installations having a centralized technical management station in which it is necessary to obtain timing information with an accuracy better than the installation cycle time.

It applies in particular to a system for assisting the operation of pipelines for the detection and rapid localization of leaks. Such The system in fact comprises control stations associated with a central operating station to which they are connected by a transmission medium consisting of a telephone channel. When a leak appears at a point in the network, a pressure drop occurs which propagates on each side in the pipeline, in the form of a negative pressure wave. These waves arrive in stations with offsets with respect to the time of appearance of the leak as a function of the distance between the point of escape and the stations, and the speed of this wave, (of the order of 900 m / s).

From the hourly data associated with the detection in two stations, of pressure waves consecutive to the appearance of a leak and of the distance between these stations, it is easy to locate the leak quickly and with very good accuracy.

This system is very advantageous since it does not require a very precise clock in each station and nevertheless gives good precision.

Claims (5)

1. Method of relative timing of events detected by stations distant from a central management station to which they are connected by transmission lines, characterized in that it consists: - in the central station to develop and simultaneously transmit to the stations a quasi-periodic time reference signal, defining hourly units of duration much longer than the interrogation-response cycle time from the central station to all the stations; in each station to be reset, at each hourly unit a first counter by the reference signal received, to count simultaneously counting pulses of rhythm given in this first counter and in a second counter, to be loaded by the content of the first counter, the second counter when the latter has reached its maximum capacity, this maximum capacity being greater than the maximum number of counting pulses in an hourly unit, to be allocated to each detected event of hourly data consisting of the content of the second counter during the detection of the event and ambiguity clearing information having different states at the start and end of a time unit, and to transmit during station interrogations by the central station information relating to events with the corresponding time data ; - And in the central station to assign the information received from an additional hourly data corresponding to a time unit number. 2. Method according to claim 1, characterized in that, in each station, information item of initialization report is generated during the initialization of the first counter and transmitted to the management center. 3. Method according to one of the preceding claims, characterized in that the initialization consists in resetting the first counter to zero. 4. Centralized technical management system comprising a central management station and remote stations connected to it by a transmission channel, the central station communicating with the stations either by general orders taken into account by all the stations, or by particular orders taken into account only by some of these stations, stations comprising event sensors to be timed, characterized in that it comprises, for the implementation of the timing process according to any one of the preceding claims, - in the central station, means of processing and transmitting, in general order, the time reference signal setting the time units and a counter for these time units, - And in each station a timing circuit (CH _I ) comprising a clock (10) connected to the counting inputs of a first and a second counter (11,12) a reference signal input connected to the input a flip-flop (21), and an initialization input (RESET) of the first counter, the second counter comprising a multiple loading input connected to the multiple output of the first counter and an output (D) connected on the one hand to a reading input (L) of the first counter controlling the loading of the second counter and to an input for controlling the change of state of the flip-flop (21), the timing circuit further comprising a transfer circuit (14,20 ) having a control input coupled to the sensors and data inputs coupled to the outputs of the second counter and of the scale, to transmit to the output of the chronometry circuit the corresponding hourly data when an event is detected, the station further comprising means of memo storage ire detected events and corresponding hourly data. 5. Application of the system according to claim 4, to the detection and rapid localization of leaks in a fluid transport network, the stations being distributed along the network, and the events detected being negative pressure waves, consecutive to a leak, detected by the station sensors respectively upstream and downstream of the leak, the location and the instant of appearance of a leak being determined from the hourly data associated with the detected events.

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