MXPA97003779A - System of supply of the auxiliary devices for a pumping station feeding distan - Google Patents

Abstract

A transformer in which the primary windings are connected in series with the pump motor to the secondary windings, which are fed to a cascade rectifier and to a voltage limiter, which regulate the voltage supplied to the auxiliary devices by a bypass of the current supplied in excess by the secondary windings

Description

SYSTEM. OF SUPPLY OF THE AUXILIARY DEVICES FOR A STATION OF PUMPING POWERED AT DISTANCE The present invention relates to a system for feeding the auxiliary devices for a pumping station fed at a distance. In the exploitation of submarine oil wells, it has been established that it is desirable to equip each of the wells with a pumping station. This station must be underwater. It is desirable that it feeds remotely, eventually, from the shore or bank. This makes it necessary to feed the pumping station by means of a power cable, from a power generator. The motor of the pump is an induction motor, it will be fed directly by a power generator, provided with a three-phase alternating current of variable frequency, through a cable system that essentially comprises a power cable with three conductors. To clarify the ideas, the group of the motor pump can consume up to 2500 kW, either 3500 KVA, or even 300 A approximately under 6.6 kV, with a frequency of 100 Hz. However, applications have already been considered at 6000 w . A transformer that raises the voltage and a transformer that lowers the voltage can be, REF: 24798 respectively, inserted in the two ends of the cable to reduce losses. In the pumping station, next to the group of the motor pump, there are several auxiliary devices, such as the electronic boards, which work with direct current and low power, as well as the valves, the fans of the pumps, which work with alternating current at a medium power. This makes it necessary to feed such auxiliary devices and to exchange command and information signals between them. The classic solution is to add a cable for this effect, next to the power cable, or to add additional drivers to it. The documents FR-A-2 699 016, FR-A-2 506 969, FR-A-2 230 141, describe, on the other hand, in different technical domains, that it is possible to avoid the use of additional electric conductors to feed the auxiliary devices associated with a load powered by alternating current. The solution suggested in these documents is to use a current transformer in which the primary is in series with this load, to power the auxiliary devices. FR-A-2 699 016 suggests, in particular, providing such a current transformer for each phase. The three mentioned documents indicate that the current in the secondary must be rectified and regulated to obtain a satisfactory continuous power supply for the auxiliary devices. In particular, documents FR-A-2 699 016 and FR-A-2 230 141, suggest providing a cascade rectifier and a voltage limiter that derives the current excessively provided by the secondary. It is not, however, evident to apply this technique equally in the case of a pumping station powered at a distance, due to the electrical characteristics of the pumping stations indicated above. The excess current can be very important and the conventional means of limitation, such as those of document D4, as well as those, on the other hand, of documents FR-A-2 699 016 and FR-A-2 230 141, lead to the dissipation of excessive powers. The present invention provides a solution to these problems. According to an essential characteristic of the invention, the feeding system for a pumping station supplied at a distance, comprises a transformer in which a primary winding, (per phase), is connected in series with the pumping motor and in the which a secondary winding (per phase), supplies a cascade rectifier and a voltage limiter that derive the current supplied in excess by said secondary winding and a capacitor connected in parallel, to the continuous output of said rectifier, and in which the voltage of the load is compared with a reference voltage, to drive a voltage limiting switch that derives in a short circuit, the DC current supplied in excess by said rectifier. In this way, the derivation of the current is produced by a temporary short circuit, the dissipation of the energy is then minimal. According to another characteristic of the invention, the auxiliary devices are the direct current auxiliary devices that are connected to the output of the rectifier, in parallel on the voltage limiter. Thus, the voltage limiter also regulates the DC voltage that is supplied to DC auxiliary devices. In accordance with another feature of the invention, a diode decoupled between the limiting switch and the capacitor is provided, in order to preserve the charge of the capacitor. According to another characteristic of the invention, the auxiliary devices are the auxiliary alternating current devices, which are connected to the secondary winding (per phase), in parallel on the rectifier. The voltage limiting circuit regulates the amplitude of this voltage, dissipating it in a resistive load, all the excess current. According to another feature of the invention, the voltage limiter is preceded by a switch that allows the output of the rectifier to be shorted, a decoupling diode is provided between this switch and the voltage limiter. According to another feature of the invention, the power system comprises at least two transformers connected in series, to feed, respectively, on the one hand, DC auxiliary devices, and on the other hand, auxiliary alternating current devices. According to another aspect of the invention, there is also provided a power generator for the power supply system of the auxiliary devices defined above, characterized in that it comprises the power means of waiting state, to maintain an initial power supply current. , when the pumping station is stopped. This allows to maintain a waiting state current, insufficient to drive the motor pump, but which allows to maintain the power supply of the auxiliary devices.

This current can also serve to maintain the temperature of the pump motor, thanks to the energy it supplies. According to another feature of the invention, the relay means of the stand-by power supply are also provided, providing a temporarily increased current during spaced periods, when the pumping station is at rest. This increased current, provides an excess of energy to the pump, but for a short time, so that it can support it, its rise in temperature remains within the limits provided. The frequency is now such that the motor pump group remains stopped. The increased current allows obtaining the necessary voltage for the power supply of the auxiliary alternating current devices. The different objects and features of the invention will appear clearer in the following description, given by way of non-limiting example, of an example of the application of the invention, with reference to the Attached figures, which represent: - Figure 1, a general diagram of a power and drive system for a remote-powered pumping station, which employs the power systems of the auxiliary devices of the invention, - Figure 2, a more detailed diagram of an application mode of the power supply system of the auxiliary devices of the invention, provided for the power supply of DC auxiliary devices. - Figure 3, a more detailed diagram of an application mode of the power supply system of the auxiliary devices of the invention, provided for the power supply of the auxiliary alternating current devices. Figure 1 represents, essentially, the submerged part 1, of a power system driven by a pumping station 2, to which a cable 3 which comprises a three-phase power line 4 and an optical fiber 5. Power 3 is inserted, before it reaches a motor pump group 6, a current transformer 7, which extracts from the line a supply current supplied to a power supply unit of the auxiliary devices 8, which, in the modes, are represented in Figures 2 and 3, which feeds the auxiliary devices 9 coupled to the motor pump group 6. Several transformers 7 are eventually connected in series in the power line, each associated with a remote power unit 8, to feed different auxiliary devices, as will be seen below.

On land, the power generator of the pumping station 10 supplies on the power line 3 a current of an intensity and frequency appropriate to provide the motor pump group 6 with a desired speed. For this purpose, it is driven by a drive and control unit 11, which itself receives the running commands 12. The unit 11 communicates by the optical fiber 5 with the auxiliary devices 9. It receives in a particular way, the information on the conditions of the motor pump unit 6, which allows a drive in circuit of the motor pump group. The interest of such a system of feeding and of the drive of the pumping station, is that it only comprises a submarine power cable with three conductors and an optical fiber (or several), so it is economical, particularly due to the fact that such cables are available in the market for other applications. The use of a current transformer placed in series on the power line, provides a load in series / however, limited, as will be seen, and which is taken into consideration automatically within the framework of a drive in circuit of the voltage supplied to the motor pump unit. This does not penalize the power supply of the motor pump unit.

It will be examined now in more detail, with reference to Figure 2, a first application of the invention, that is, of the power supply system of the auxiliary devices comprising the current transformer 7 and the power supply unit of the auxiliary devices 8 of Figure 1, suitable for the power supply of DC auxiliary devices. The three-phase power line that passes, before arriving at the motor pump unit 6 (Figure 1), by a primary winding 13 (for each phase), of a current transformer 7. A secondary winding 14, (per phase), of this current transformer feeds a bridge rectifier 15, coupled to a voltage limiter by a line 'bifilar, through which a DC output is fed, to which DC auxiliary devices are connected, that is, they require a DC voltage supply of a defined value and that they consume collectively, a certain direct current that the power system must be able to supply. Between the bridge rectifier 15 and the limiter 16, a circuit of protection against excessive tensions 17, essentially comprises a rectifier 18, operated through a Zener diode 19 and with a current flow over a short circuit. The voltage at the output of the bridge rectifier is thus limited by the priming of this protection circuit, in case of abnormal excessive voltage, caused, for example, by a fault of the motor pump unit. Once the driven rectifier 18 becomes conductive, the voltage supplied to the voltage limiter is canceled. It must, as a consequence, cut the current on the cable so that the driven rectifier is blocked and the voltage supplied to the voltage limiter is restored. The current limiter 16 comprises a rectifier 20, which charges a capacitor 21. The charging voltage of this capacitor is a regulated voltage that supplies the DC controlled regulated supply; it is supplied to a voltage comparator 22 which also receives a reference voltage E, and which subtracts one from the other. The difference of these voltages drives, by means of a hysteresis circuit 23, a switch 24. When the DC voltage exceeds a value determined by the hysteresis of the circuit 23, at the reference voltage E, the switch 24 derives the supplied current by the rectifier on a short circuit. The diode 20 is blocked. The capacitor 21 maintains the power of the auxiliary devices, but is discharged and the DC voltage decreases. When it reaches the lower threshold of the hysteresis of the circuit 23, the switch 24 opens again, the capacitor is recharged and so on.

In this way, when the current in the power line is sufficient, that is to say, the same as when the motor pump unit is in standby state, as will be seen later, the voltage limiter 16 operates and limits the voltage supplied in the CD output. The same voltage considered through the rectifier 15 and the transformer 7, is that which loads the power circuit and that must be supplied by the generator 10. It is minimum: a few volts, and whatever the operating speed of the motor pump. More precisely, outside the pumping regime, the generator 10 is arranged to maintain a minimum supply current of 30 A, for example, the voltage is approximately 60 V, at the level of the pumping station. In these conditions, the voltage at the terminals of the output of the bridge rectifier is, for example, 50 V, the limiting circuit supplies approximately 200 W, under a voltage that oscillates around the voltage E, within the limits of the hysteresis of the circuit 23. The protection circuit does not work. In pumping mode, regulated continuous DC feeding is ensured under the conditions described above. The limit switch 24 must carry all the current supplied by the rectifier 15, less the current consumed by the auxiliary devices, but in a short circuit, so that the power dissipated is minimum. In case the limiter 16, and mainly the switch 24, suffered an overload, the protection circuit would intervene, its silicon controlled rectifier 18 can withstand much higher currents. An advantage of this circuit is that it can work with currents on the cable, which vary in large proportions, since the DC supply voltage is limited by a short circuit, ie without energy dissipation. Returning now to Figure 3, which represents another mode of application of the invention, appropriate this time to the power supply of the auxiliary alternating current devices. In this example, in which the structure is generally similar to that of the unit of Figure 2, all the functionally identical components have retained the same reference as in Figure 2. It is also observed that the transformer 7, the rectifier 15 , the protection module 17, and the voltage limiter 16, are invariant, except that, in the voltage limiter 16, the diode 20 is absent, while a load resistor 27 is connected in series with the switch of limitation 24. On the other hand, in the case of the direct connection between the modules 16 and 17 is broken, an optional module 28 is supplied, comprising a series diode 25, as well as a switch switch 26, driven by CD, can deriving the current from the continuous output of the rectifier 15 over a short circuit. The alternating current auxiliary devices to be powered are connected to the AC output, which is the three-phase output of the winding 14. The operation of the transformer 7, the rectifier 15, the protection circuit 15, and the limiter 16 is that which is described with respect to Figure 2, or sufficiently similar, as will be readily understood by one skilled in the art, with the exception of what is explained hereinafter. In such a way, when charging the capacitor. 21 does not reach the reference voltage E, the voltage limiter does not intervene, and the alternating voltage AC is that which supplies the winding 14. When the load of the capacitor 21 exceeds the reference voltage E, of the hysteresis threshold of the circuit 23, the limiting switch 24 should pass, however the current is diverted to the load resistor 27. The effect is that the voltage stops crossing the terminals of the capacitor, the output of the rectifier and the output of the winding 14. This regulates the voltage three-phase alternating supplied on the AC output.

It is thus understood that the diode 20 of Figure 2 is not necessary. With regard to the modality of Figure 2, it is easily observed that it is the same as in Figure 3, since it offers the same effects of limiting the voltage drop on the power and voltage regulation line supplied to the devices The auxiliary devices, this time imposes a dissipation of the power in the limiting switch 24 and in the load resistor 27. This does not constitute a disadvantage for the following reason: the auxiliary devices in question, fans of the pump of an accumulator of oil pressure (for the lubrication of the motor pump), they do not need to work permanently, when the power system is at rest, the motor pump is stopped. Intermittent operation is sufficient. To meet this need, it is provided that the generator 10 supplies, for periods (5 minutes every 10 minutes, for example), a current of 130 A and of no more than 30 A, the frequency is and remains relatively high, so that the motor pump group remains stopped. Its temperature then rises, but the duration of the period and the cyclical relationship are such that it remains within the norms.

The reference voltage E is thus chosen in such a way that the regulation operates a little below this value of the current, by the voltage resulting from a current of 120 A for example, when, taking into account the ratio of the transformation , the three-phase voltage at the output of the secondary winding 14, and on the AC output, is approximately 400 V. In this way, the current to be derived by the voltage limiter, and in particular by the limiting switch, in the periods in which it will reach its maximum (the 300 A mentioned above), will be much smaller than that which should derive the voltage limiter of Figure 2. The power dissipated in the switch 24 and the load resistor 27, will be thus limited, which provides the economically viable solution. It is necessary to consider the case in which the optional module 28 is supplied. It essentially comprises a switch switch 26, which, under the effect of the drive Cd (which can be provided by one of the direct current auxiliary devices, for example), short-circuited to the continuous output of the rectifier 15. The alternative voltage supplied over the AC output is now practically voided. Auxiliary AC devices are not powered anymore. The diode 25, like the diode 20 (Figure 2), protects the capacitor 21 and, in this more particular case, avoids the short circuit. Since the CD drive is suppressed, the switch switch is re-locked and the three-phase AC voltage is reset to its previous value over the AC output. Thus, this additional module is installed as many times as necessary to be able to stop the operation of the auxiliary alternating current devices during a period in which they are powered to function. Now, always according to the invention, in a pumping installation comprising the direct current auxiliary devices and the auxiliary alternating current devices, a transformer 7 associated with a unit according to Figure 2 will be provided for the first ones, afterwards, in series, a second transformer 7 and a unit according to Figure 3, for the seconds. If several DC power outputs must be produced, the same several assemblies will be provided according to Figure 2, wherein the transformers 7 will be equally in series. The same will be done for several alternative voltage outputs. It will be noted, therefore, that the DC output of the power supply unit of Figure 3 can provide a DC voltage of approximately 500 V, at the same time as the AC voltage, this is only to allow a very simple control of the presence of the latter. It will be evident that the foregoing descriptions have been provided only by way of example and are not limiting and that the numerical values, in particular, they can vary according to the example of the application considered. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. A system for feeding the auxiliary devices to a pumping station supplied at a distance, characterized in that it comprises a transformer, with a primary winding (per phase), which is connected in series with the motor of the pump, and with a secondary winding ( per phase), which supplies a cascade rectifier and a voltage limiter, which derive the current supplied in excess by the secondary winding and which comprises a capacitor connected in parallel, in the rectifier's continuous output, and where the voltage load is compared with a reference voltage (E), to drive a voltage limiting switch, deriving, in a short circuit, the DC current excessively supplied by the rectifier, the capacitor maintains the voltage of the output when the switch of voltage limitation derives the DC current in excess.

2. The feeding system of the auxiliary devices for a pumping station according to claim 1, characterized in that the auxiliary devices are the DC auxiliary devices, which are connected to the output of the rectifier, in parallel on the voltage limiter .

3. The feeding system of the auxiliary devices for a pumping station according to claim 2, characterized in that a decoupling diode is provided between the limiting switch and the condenser, in order to preserve the charge of the condenser.

4. The system for feeding the auxiliary devices for a pumping station according to claim 1, characterized in that the auxiliary devices are the auxiliary alternating current devices that are connected to the secondary winding (per phase), in parallel on the rectifier.

5. The feeding system of the auxiliary devices for a pumping station according to claim 4, characterized in that the limiting switch derives the current supplied in excess by the rectifier.

6. The system for feeding the auxiliary devices for a pumping station according to claim 5, characterized in that the limiting switch derives the current supplied in excess by the rectifier, in a load resistor.

7. The feeding system of the auxiliary devices for a pumping station according to claim 6, characterized in that the limiting switch is preceded by a switch switch, which allows the short circuit of the rectifier output, a decoupling diode is provided between the switch and the voltage limiter.

8. The feeding system of the auxiliary devices for a pumping station according to claim 1, characterized in that the feeding system comprises at least two transformers, connected in series to feed, respectively, on the one hand, according to claim 2 or 3, auxiliary direct current devices, and on the other hand, in accordance with claim 4, 5 or 7 (CA), the auxiliary alternating current devices.

9. The feeding system of the auxiliary devices for a pumping station according to claim 2 or 3, characterized in that it comprises a power generator for the feeding system of the auxiliary devices that were defined above, which comprises the feeding means in standby state to maintain a minimum power flow when the pumping station is stopped.

10. The feeding system of the auxiliary devices for a pumping station according to claim 9, characterized in that the generator comprises the standby power supply means supplying a temporarily increased current during spaced periods, when the pumping station is stop.