FR2844401A1 - Method for providing zone with two secure independent supply points, comprises continuous testing of three independent incoming supplies and switching on fault detection to secure supply points - Google Patents

Abstract

The method may use three independent sources of incoming supply (A,B,C) which are connected to two changeover switches (B1,B2). The outputs from these two switches are in turn connected to two further changeover switches (B3,B4) to give final outputs (P1,P2). The incoming supplies are continuously monitored and on detection of a failure the changeover switches are operated to maintain the final outputs secure Independent claims are also included for the following : 1) Installation which has at least three independent incoming supplies connected to two secure outputs through changeover switches which on any incoming supply failure are automatically operated to secure the outgoing supply points 2) A work station which as part of the installation includes a processor programmed to operate the changeover switches such as to secure the outgoing supply points after a failure of one of the incoming supplies

Description

Method and installation for the electrical supply of a zone

  The present invention relates to a method and an installation for substantially permanently supplying power to activity zones, such as

airports.

  In areas of activity such as airports 10 or factories processing sensitive products, the

  risk of a long power cut is intolerable. The generally applied security standards require that two separate and operational power sources are provided at all times for such areas.

  A usual solution consists in providing then, in addition to a source coming from a distribution network, an autonomous secondary source, of the generator or other type. However, such secondary sources have a limited autonomy over time. In addition, they are costly in design, given the importance of the electrical supply to be provided for activity areas of the aforementioned type. They also require a

  preventative maintenance which is constant.

  One solution to remedy this problem consists in providing two independent sources, both from the distribution network, and switching from one of the sources (usual) to the other (secondary) in the event of failure of the usual source. However, the distribution service itself must guarantee its customers two independent sources, always operational even in the event of possible deterioration of a line of the supply network. The distribution service must also guarantee the supply of the activity area despite the malfunction of a means of switching from one source to another. In addition, certain activity zones cannot withstand long power outages. In this case, activity zones such as airports are equipped with lighting means, in particular runways, comprising sodium lamps or other lamps.

  with inertia in their normal operating regime. Thus, a too long power cut (for example greater than about one second) can lead to an even longer failure of the lighting means 15 and is, as such, intolerable.

  The present invention improves the situation. To this end, it proposes a method of supplying electricity to an activity zone from a distribution network, in which: a) at least three independent arrivals A, B and C are provided, originating from the distribution network distribution, as well as permutation means comprising at least three inputs connected respectively to the three inlets, and two outputs 25 connected respectively to two outlets which are capable of supplying an activity area, b) repeatedly testing the power supply capable to be supplied by each arrival A, B and C, and c) said permutation means are piloted, in the event of an arrival failure, detected in step b), so as to ensure, at the two outputs of the means permutation, two respective, independent power supplies, delivered according to one of the combinations of arrivals A and (B or C), or B and C. According to an advantage which the present invention provides, the independence of perm and, in the event of a failure of one of the arrivals, to continue to ensure the possible supply of the activity area from two independent sources and, in the worst situation 10 corresponding to a failure of two of the arrivals, the feeding of the activity area thanks to the only

valid arrival remaining.

  Compared to the solution advocating the use of one or more generator sets, the present invention offers a scalable solution according to the supply needs of the activity area, the only

  limit being the power tolerated by the cables.

  In an advantageous embodiment, provision is made in step a) for an independent additional supply D to ensure, in step c), an electrical supply, delivered to the two outputs of the permutation means, according to at least one of the combinations arrivals (A or B) and

(C or D).

  Preferably, in step b) a drop in the electrical supply supplied by one of the

  arrivals, below a predetermined threshold and for a selected delay time. As a variant or in addition, it is possible to estimate a slope of the supply drop during said delay time, depending on which step c) is applied or not.

  Advantageously, a latency time is also taken into account for the implementation of step c), while said delay time, added to the latency time, is less than or close to 0.5 seconds. This latency time preferably comprises - a time required to choose an appropriate configuration of the permutation means with a view to connecting the two outputs of the permutation means to two non-faulty arrivals, and - a time required for the physical actuation of means

  that include the permutation means.

  In a preferred embodiment, the permutation means comprise rocking means of a first level, comprising inputs connected to the arrivals, and rocking means of a second level, comprising outputs connected to the departures. In step c), a possible failure of a component of the first level flip-flop means is then detected to implement the second-level flip-flop means by ensuring, at the two outputs of the permutation means, respective power supplies valid according to one of said combinations of arrivals A and (B or C), or B and C. The present invention also relates to an installation 25 for implementing the above method, this installation comprising permutation means comprising: - at least three inputs connected respectively to three independent arrivals A, B and C, coming from a distribution network, - two outputs connected respectively to two departures intended to supply an activity area, and - tilting means arranged to ensure, at the two outputs of the permutation means, two respective independent electrical supplies 5, delivered according to one of the combinations of arrivals A and (B or C), or C and B. Advantage wear, the installation includes at least

  a work station capable of controlling the means of permutation in the event of failure of an arrival.

  As such, the present invention also relates to such a workstation, comprising an automaton programmed to estimate, in service, a configuration of the switching means in the event of failure of an arrival and / or in the event of malfunction of a component of the permutation means. Advantageously, the aforementioned installation comprises sensors of the electric power supplied by each arrival, each connected to said work station, and the work station is then arranged to - detect a drop in the electric power supplied by an arrival. , - estimate an appropriate configuration of the permutation means making it possible to deliver, to the two outputs of the permutation means, respective non-faulty electrical supplies, according to one of the combinations of arrivals A and (B or C), or B and C , - and control the switching means of the permutation means for delivering said two respective non-faulty power supplies 30 to the two outputs of the means

permutation.

  Preferably, said work station is further arranged to: control the physical actuation, for example by motorized assistance, of each switching means of the permutation means; - detect a possible operational failure of each tilting means, and

  re-estimate a new configuration of the permutation means, advantageously in the event of a failure of an arrival and / or of a flip-flop means.

  Other features and benefits of

  the invention will appear on examination of the description

  detailed below, and attached drawings in which: - Figure 1 shows an installation within the meaning of the present invention, for supplying, from two feeds P1 and P2, an activity area; FIG. 2 schematically represents the means of permutation of the installation, from four flip-flops, with four arrivals A, B, C and D, and two departures P1 and P2 capable of supplying each the activity zone; FIG. 3 schematically represents the means of permutation of the installation, from four flip-flops, here with three arrivals A, B and C, and two departures Pl and P2 capable of supplying each the activity zone; FIG. 4 schematically represents the means of permutation of the installation corresponding to those shown in FIG. 2, but in which each rocker comprises two switches whose outputs are connected together; FIG. 5 diagrammatically represents the means of permutation of the installation corresponding to those represented in FIG. 3, but in which each rocker comprises two switches whose outputs are connected together; - Figure 6 shows schematically a complete installation comprising permutation means of the type shown in Figure 4, according to a preferred embodiment; and FIG. 7 represents the temporal variation of the supply voltage recovered at one of the departures in the event of failure of one of the initial arrivals

connected to this departure.

  Firstly, reference is made to FIG. 1 in which an activity zone (such as an airport) is supplied from the sole energy of the distribution network, without using an autonomous source (such as a generator), in normal operation or in

emergency march.

  To this end, provision is made in an embodiment

  preferred, four independent arrivals A, B, C and D, coming from the public distribution network and connected to an INS installation within the meaning of the present invention.

  The INS installation includes permutation means (not shown in FIG. 1) so as to deliver, from the four arrivals A, B, C and D, two feed feeds Pl and P2, independent and susceptible

  to supply the activity zone each.

  In a preferred embodiment, the installation INS is capable of managing four independent arrivals to supply power to the departures Pi and P2 corresponding to (A or B) and (C or D). In a variant according to which only three independent arrivals A, B and C are available, the installation supplies feeds to the departures Pl and P2 corresponding to A and (B or C), or B and C, as will be seen below. The INS installation corresponds to a public distribution station which thus constitutes a rapid switching center, between four upstream supply sources A, B, C and D, so as to guarantee continuity of supply on a downstream network. Advantageously, the

  activity zone, in the downstream network, can be permanently supplied by two separate upstream sources Pi and P2.

  When one of the four upstream sources A, B, C or D is faulty, the installation INS detects this fault 15 and proceeds to supply the downstream network from a

other source, by permutation.

  In the example described, the power sources A, B, C and D provide a supply voltage of 20 kV. Of course, it is possible to provide power sources 20 with different voltages, according to the standards.

  of electrical distribution in France.

  Referring now to Figure 2 in which the permutation means of the installation of Figure 1 comprises four inputs connected to the arrivals A, B, C 25 and D, and two outputs connected to the two departures Pl and P2, respectively. These permutation means ensure the routing of electrical energy from arrivals to departures, in particular in the event of failure of one of the arrivals. To this end, these permutation means comprise: - a first flip-flop B between the arrival A and the arrival B; - a second flip-flop B2 between arrival C and arrival D; - A third flip-flop B3 between the output of the first flip-flop BE and the output of the second flip-flop B2, the output of this third flip-flop B3 being connected to the first start Pi; and a fourth flip-flop B4 between the output of the first flip-flop Bi and the output of the second flip-flop B2, the output of this fourth flip-flop B4 being connected to the

second start P2.

  Each of the four flip-flops BE, B2, B3 and B4 may include a switch between two positions to direct the electrical energy between two arrivals, towards a departure. In a variant corresponding to a preferred embodiment, as shown in Figure 4, each flip-flop comprises two switches whose outputs are connected together. These switches are advantageously in the form of circuit breakers

or secure switches.

  In a normal operating mode, the two flip-flops Bi and B2 are configured to connect the arrivals B and D, respectively, to their outputs. Furthermore, the third and fourth flip-flops B3 and B4 are configured so as to connect only one arrival (respectively B and D) to a departure (respectively Pi and P2). Thus, the arrival B is connected to the departure Pl and

  the arrival D is connected to the departure P2.

  In the event of failure of the arrival B, the first flip-flop BE changes state to direct the energy supplied by the arrival A, towards the departure Pl, via the flip-flop B3 which does not change state . In the event of failure of the arrival D, the flip-flop B2 changes state to direct the energy supplied by the arrival C to the departure P2, via the flip-flop B4 which does not change state. Furthermore, if the first flip-flop B1 has a malfunction, or even if the two arrivals A and B are faulty at the same time, one of the non-faulty sources C and D feeds the two feeders 10 Pl and P2. Similarly, if the second flip-flop B2 has a malfunction, or if the two arrivals C and D are faulty at the same time, one of the two sources does not

  faulty A and B feeds the two feeders Pl and P2.

  In particular, starting from the configuration in normal mode of FIG. 2, if the source B becomes faulty and that, moreover, the first flip-flop B1 malfunctions, the third flip-flop B3 changes state so that the two starts Pl and P2 are supplied by the same source D. Likewise, if the arrival D 20 is faulty and the second flip-flop B2 has a malfunction, the fourth flip-flop B4 changes state and the two feeds Pl and P2 are supplied by the same arrival B. Thus, firstly, a failure of one of the four arrivals will be detected and, secondly, a possible failure of a first level rocker means such as one will be detected first and second flip-flops B1 and B2, as we will see below. In particular, in the event of a malfunction of the first level rocking means Bl or B2, provision will be made for a permutation in the second level rocking means

level B3 or B4.

  In the embodiment shown in FIG. 2, a supply combination is then obtained, at the level of the departures Pi and P2, corresponding to A and (C or D), or B and (C or D), or A or B or C or D only. Of course, in a more sophisticated variant, it can be

  provided an additional weighing stage making it possible to make arrivals A and B independent on the one hand, and arrivals C and D on the other hand, which makes it possible to obtain a set of combinations corresponding to A and ( B or C 10 or D), or C and (D or B), or A, B, C or D only.

  In the embodiment shown in FIG. 3, only three independent arrivals A, B and C are provided. Nevertheless, the permutation means of FIG. 2 are preserved, with however arrivals 15 of the first and second flip-flops Bl and B2 connected to the same arrival B. Thus, in the event of failure of the source A, the first flip-flop Bi changes state to direct the energy delivered by the source B, towards the departure Pl. In the event of failure of the first flip-flop Bi, the two departures Pl and P2 are supplied by the same arrival B or C. In this case, the third flip-flop B3 changes state and connects the first start P1 to the second flip-flop B2. Symmetrically, if the source C fails, the second flip-flop B2 changes state to connect the arrival B to the departure P2. Similarly, if the second flip-flop B2 has a malfunction, the flip-flop B4 changes state to connect the arrival A to the second departure P2. This embodiment thus makes it possible to deliver to the feeders P1 and P2 a supply according to one of the combinations A and (B or C), or B and C, or A, B or C only. In the respective embodiments of the

  Figures 4 and 5, the flip-flops B1, B2, B3 and B4 have been replaced respectively by pairs of switches IA and IB, IC and ID, Il and I2, I3 and I4. The outputs of the 5 switches of each pair are linked together.

  As indicated above, in this preferred embodiment, the switches are preferably circuit breakers usually used in public distribution, so that the risks of malfunction of the switching means are limited.

  Reference is now made to FIG. 6 to describe a preferred embodiment of an installation within the meaning of the present invention. In this embodiment, eight switches are provided for connecting two feeders Pl, P2 15 to four possible arrivals A, B, C and D, as described above with reference to FIG. 4. Preferably, the switching of each switch is controlled by an electrical control controlled by a STE workstation. In fact, two arrivals must be avoided in parallel. This is how the switches of each pair IA and IB, IC and ID, Il and I2, I3 and I4 are never in the same state, closed. Furthermore, voltage sensors are provided upstream of each switch connected to an inlet (first level switches). These voltage sensors are connected to the STE workstation, which makes it possible to detect the failure of one of the arrivals A, B, C or D, in particular if this faulty arrival was initially connected to one of the departures Pl and P2. Thus, the work station STE is arranged to detect the failure of one of the arrivals, or even a malfunction of one of the switches of the installation. Advantageously, independent compartments S1, S2, on the one hand, and S3, 5, on the other hand, are provided for the first level rocking means and for the second level rocking means, respectively. In addition, independent compartments are provided for the switches connected to arrivals A and B, on the one hand, and for the 10 switches connected to the other two arrivals C and D, on the other hand. These compartments are advantageously separated geographically, in isolated enclosures and formed in concrete structures with a surface area of around ten m2. Thus, in the event of a fire in compartment S1 (comprising the switches connected to arrivals A and B) causing degradation of one of the switches IA or IB, compartment S2 (comprising the switches connected to arrivals C and D) is preserved. Likewise, the compartment S3 (comprising the switches 20 connected to the feeders Pi and P2) is preserved. Thus, the switches Il and I2 connected to the start Pi can change state and only one of the sources C or D supplies the two

Pl and P2 departures.

  In a less sophisticated embodiment, the 25 compartments S1 and S2 can be provided in the same enclosure, however geographically separated from the

compartment S3.

  The STE workstation preferably comprises a central unit connected to an input device such as a keyboard and to a control monitor. In the memory of the central unit is stored software for estimating the respective configurations of the switches, in the event of a failure of an arrival, or in the event of a malfunction of one of the switches. Thus, the workstation STE connected to the 5 motors M and to the aforementioned voltage sensors implements a PLC programmed beforehand to estimate as quickly as possible the configuration of the permutation means, in the event of any failure (of a

source or switch).

  Advantageously, the workstation STE is regularly controlled by a master workstation STM, capable of replacing the slave workstation

  STE, in case of failure of the latter.

  Reference is now made to FIG. 7 to describe the permutation steps that the workstation performs in the event of a failure of one of the sources or

  a switch malfunction.

  In principle, for activity zones such as airports, each of the two departures P1 and P2 should not be subjected to a voltage dip, or to a power cut of greater than or on the order of one second. A voltage dip is defined for example by a 15% drop in three-phase voltage. The cut-off time is counted from the crossing of the 15% threshold (start of the duration tl in FIG. 7). In a preferred embodiment, the first flip-flop (the switches IA, IB, IC and ID) has priority over the second set of flip-flops (the switches Il, I2, I3 and I4) and this second flip-flop is not triggered that if permutations in the first stage have not worked or cannot work due to a failure of one of the

first floor switches.

  For each possible changeover, the parallel connection of two arrivals A, B, C or D is prohibited in 5 automatic mode. A changeover therefore takes place in a sequence comprising the following steps - detection of a voltage dip; - estimation of a permutation configuration; command to open the switch connected to the faulty inlet; - confirmation of the opening of this switch by transmitting its position to the STE workstation; and - control of a motor for closing a second switch (for example the switch IA in the event of failure of the inlet B, as shown on the

figure 4).

  Preferably, each sensor upstream of the switches IA, IB, IC and ID is a digital voltage relay capable of sending, for each phase of the supply, "voltage dip" information, if the supply voltage is 15% lower than usual nominal voltage. In a more sophisticated variant, a voltage drop slope can be estimated and "voltage dip" information is sent to the workstation STE if the slope of this voltage drop is

  greater than a predetermined slope value.

  Referring again to FIG. 7, the duration tl corresponds to a time for acquisition of the measurement by the aforementioned digital voltage relay (voltage sensor upstream of the incoming switches), to which is added a time of calculation cycle in the estimation of the permutation configuration to be adopted. This last cycle time depends essentially on the speed of the processor provided in the central unit of the STE workstation. In practice, the overall duration tl is close to 70 milliseconds, with the means for detecting voltage dips and calculating the configuration of the

current permutation.

  Furthermore, the duration t3 corresponds to the time 10 necessary to physically actuate the switches of the installation (opening of the switch IB, closing of the switch IA, in the event of failure of the arrival B), including the confirmation of the IB switch, transmitted to the STE workstation. 15 In principle, the duration t3 of mechanical actuation of the

  switches is close to 200 milliseconds, in particular between 160 and 220 milliseconds, depending on the characteristics of the permutation means used.

  It will be noted in particular that the supply voltage 20 U of one of the feeders Pl and P2 is zero for the duration t3 since it is first necessary to open the switch of the faulty feeder, then close the switch of

non-faulty arrival.

  Thus, the total duration necessary for the detection of a failure and for the subsequent permutation (corresponding to the duration tl + t3) is at most close to 300 milliseconds. As the activity zone, in this embodiment, requires that the power cuts do not exceed one second, there therefore remains a duration t2 30 allowing a time delay, before mechanically triggering the permutation. This delay time t2 chosen, close to 200 milliseconds in the example described, then makes it possible to ensure that a momentarily faulty voltage does not ultimately rise to the nominal value Un, of normal operation. This time delay 5 t2 makes it possible in particular to avoid carrying out permutations which, ultimately, are not necessary, and above all to avoid a break

  supplying the activity zone for a period t3.

  If, in the event of failure of one of the arrivals, 10 confirmed during the time t2, the work station STE detects a malfunction of one of the switches during the time t3, a new configuration of the permutation is estimated, during a duration close to tl, and two of the second level switches Il and I2 15 or I3 and I4 change state, for a duration close to t3. Thus, the supply voltage of one of the stations Pi and P2 is zero for a period close to t3 + tl + t3,

  or about 500 milliseconds maximum.

  In the event of a switchover required in the second level, the permutation operation (detection of failure, timeout, first permutation failed, new estimation, second permutation successful) is

  ultimately lasting less than a second.

  Thus, according to one of the advantages afforded by the present invention, a first-level and second-level permutation structure makes it possible to compensate for both a failure of a power source and a

  malfunction of a tilting means.

  Of course, the present invention is not limited to the embodiment described above by way of

  For example; it extends to other variants.

  Thus, it will be understood that the number of independent arrivals planned may be greater than three or four arrivals. Furthermore, the supply voltages of 20 kV are given here by way of example. They can vary, on the one hand, according to the distribution of the network and, on the other hand, according to the needs of the

activity area.

  Likewise, to ensure complete independence between the permutations relating to each source A, B, C 10 and / or D, an adequate number of switches or flip-flops may be provided, which however strikes the cost becomes installation.

Claims (22)

claims   1. A method of supplying electricity to an activity area from a distribution network, in which: a) at least three independent arrivals A, B and C are provided, originating from the distribution network, as well as permutation means comprising at least three inputs connected respectively to the three inlets, and two outputs connected respectively to two outlets (Pl, P2), capable of supplying an activity zone, b) the electrical supply capable of d 'be supplied by each arrival A, B and C, and c) piloting said permutation means, in the event of failure of an arrival, detected in step b), so as to ensure, at the two outputs of the means permutation, two respective independent power supplies, delivered according to one of the combinations of arrivals A and (B or C), or B and C. 20   2. Method according to claim 1, in which a drop in the electrical supply supplied by one of the inlets is detected in step b), below a predetermined threshold and for a chosen delay time (t2 ).   3. Method according to one of claims 1 and 2, in which, in step c), any faulty supply is firstly disconnected from an output of the permutation means, before connecting at least one non-faulty supply. to one   of said outputs of the permutation means.   4. Method according to one of claims 2 and 3, in which one takes into account, in addition, a latency time (tl + t3) for the implementation of step c), while said delay time , added to the time of   latency, is less than or close to 0.5 seconds. 5. The method as claimed in claim 4, in which said latency time comprises: a time (tl) required to choose an appropriate configuration of the permutation means in order to connect the two outputs of the permutation means to two non-faulty arrivals, and   - A time (t3) required for the physical actuation of flip-flop means which include the permutation means.   6. Method according to one of the preceding claims, in which the permutation means comprise rocking means of a first level (B1, B2), comprising inputs connected to the arrivals, and rocking means   of a second level (B3, B4), comprising outputs connected to the feeders, and in which, in step c), a possible failure of a component of the first level rocker means for implementing the second level flip-flop means 25 ensuring, at the two outputs of the permutation means, respective valid supplies according to one of said combinations of arrivals A and (B or C), or B and C. 7. The method of claim 6, taken in combination   with one of claims 2 and 3, in which we take   taking into account, in the event of a failure of a component of the first level flip-flop means, an additional latency time comprising: - a time (tl) required to choose a new configuration of the permutation means, in particular of said flip-flop means second level, and - a time (t3) required for additional physical actuation of the flip-flop means that comprise the permutation means, and in which the implementation of step c), in the event of a component failure first level toggle means, is of duration less than or close to one second.   8. Method according to one of the preceding claims,   in which there are provided in step a) four independent arrivals A, B, C and D to ensure, in step c), an electrical supply, delivered to the two outputs of the permutation means, according to at least one of the 20 combinations of arrivals (A or B) and (C or D).   9. Installation for implementing the method according to one of claims 1 to 8, characterized in that it   includes permutation means comprising: - at least three inputs connected respectively to three independent arrivals A, B and C, coming from a distribution network, - two outputs connected respectively to two departures (Pl, P2) intended to supply a zone activity, and - rocking means arranged to provide, at the two outputs of the permutation means, two respective, independent electrical supplies, delivered according to one of the combinations of arrivals A and (B or C), or C and B . 10. Installation according to claim 9, characterized in that the permutation means comprise four inputs connected respectively to four independent arrivals A, B, C and D, coming from a distribution network, and in that the switching means are 10 arranged to ensure, at the two outputs of the permutation means (Pl, P2), two respective, independent electrical supplies, delivered according to at least one   combinations of arrivals (A or B) and (C or D).   11. Installation according to claim 10, characterized in that the permutation means comprise: - a first flip-flop (Bl) between a first input connected to the arrival A and a second input connected to the arrival B, - a second flip-flop (B2) between a third input connected to the inlet C and a fourth input connected to the inlet D, - a third flip-flop (B3) between the output of the first flip-flop and the output of the second flip-flop, including the output is connected to a first start (Pl), and - a fourth flip-flop (B4) between the output of the first flip-flop and the output of the second flip-flop, of which   the output is connected to a second start (P2).   12. Installation according to claim 11, characterized   in that each scale includes a switch.   13. Installation according to claim 11, characterized in that each rocker (Bl; B2; B3; B4) comprises two switches (IA, IB; IC, ID; I1, I2; I3, I4) whose outputs are interconnected.   14. Installation according to one of claims 9 to 13, characterized in that it comprises at least one work station (STE) capable of controlling the means of   permutation in case of failure of an arrival.   15. Installation according to claim 14, characterized in that it comprises a second work station (STM), standby, capable of replacing a first work station (STE), in the event of failure of said first station.   16. Installation according to one of claims 14 and 15, characterized in that it comprises sensors of the electrical supply supplied by each inlet, each 20 connected to said work station, and in that the   work station is arranged to: - detect a drop in the electrical supply supplied by an inlet, - estimate an appropriate configuration of the permutation means 25 enabling two respective independent electrical supplies to be supplied to the two outputs of the permutation means, non-faulty, according to one of the combinations of arrivals A and (B or C), or B and C, - and order the switching means of the permutation means to deliver said two respective non-faulty supplies to the two outputs of the means permutation.   17. Installation according to claim 16, characterized in that said work station is arranged to control the physical actuation of each means of toggles permutation means.   18. Installation according to claim 17, characterized in that said work station is arranged for   detecting an operational failure of each flip-flop means, and in that it is arranged to re-estimate a new configuration of the permutation means, in the event of failure of an arrival and / or a flip-flop means.   19. Installation according to claim 18, taken in combination with claim 11, characterized in that said station is arranged to control the actuation of the third (B3) and / or the fourth (B4) rocker, in the event of failure of one of the first (B1) and second (B2) flip-flops.   20. Installation according to claim 19, characterized in that it comprises at least one first station (S1, S2)   comprising the first and second scales and a second station (S3) comprising the third and fourth scales, and in that said first and second stations are electrically connected and arranged in geographically separate enclosures.   21. Installation according to one of claims 9 to 20, taken in combination with claim 10, characterized in that it comprises a first station (Si) comprising tilting means (IA, IB) between two arrivals (A , B) among the four arrivals (A, B, C, D) and one   second station (S2) comprising means for switching (IC, ID) between two other arrivals (C, D), and in that said first and second stations are arranged in enclosures separated geographically.   22. Work station intended to equip an installation according to one of claims 14 and 15, characterized in that it comprises an automaton (STE) programmed to estimate, in service, a configuration of the permutation means in the event of failure. of an arrival and / or in the event of a malfunction of a component of the permutation means.