FR2786955A1 - Linearly variable loading bank for high-power 3-phase electrical network, comprises resistor bank, with forced air cooling, switched by thyristor pairs, one reverse/parallel pair per phase - Google Patents

Abstract

Each thyristor pair (6) is connected (9a,10a, etc.) between its associated resistor (11a, etc.), in the loading bank (11), and one phase (2a, etc.) of the supply network. Power, voltage and current variations are detected by sensors including, e.g., polarized toroidal current transformers (1a, etc.) on each supply phase, and input to a programmable data processor (3) associated with a circuit security unit (4), which determines any requirement for correction or, in the extreme case, circuit interruption. The processor controls the loading bank via a further unit (5) which determines thyristor firing angles. Opt., some thyristors are replaced by electromagnetic relays. An auxiliary processor (13) controls a forced draught cooling fan (12) for the resistor bank (a separate fan cools the thyristor unit), and also accepts externally input data for passing to the central unit (3).

Description

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LINEAR VARIATION LOAD BENCH

  The invention relates to the field of charging devices and more particularly charging or discharging devices with linear variation of a high power electrical network. This type of device is more particularly suitable for charging or discharging with linear variation of an electrical network comprising motors whose power is of the order of several hundred kilowatts, 500 kilowatts for example, in order to

  preserve constant characteristics on the network.

  However, this type of device can find applications in the field of devices for testing high-power engines such as gas turbines or diesel engines, for example a ship's diesel engine. Generally, electrical networks deliver active power in order to operate, for example, motors, and it is known that these motors can behave under certain conditions like power generators by injecting negative power known as reactive power into the electrical network. All the devices of the electronic equipment, generator or other type which are, on the network, upstream of these engines functioning as power generators,

  are generally protected against reactive power.

  On the other hand, if the reactive power returns to the network of the electricity supplier such as EDF in France, the

  relay installed by the latter cuts off the power to

  beyond a certain threshold of reactive power present on the network thus putting the part of the network creating a

  too much reactive power, out of service.

  Indeed, on all electrical supply networks, there is therefore an active power and a reactive power; and the electricity supplier must maintain a certain balance between active power and reactive power across its entire network; for this purpose, it has all along the network of relays which cut, beyond a certain threshold of negative power,

l i t I -

  - 2 - supply to the unbalanced part of the network so

  to preserve the quality of its supply.

  Such power cuts can cause significant damage to the various electrical devices and therefore an immobilization of these installations, and in particular an immobilization of the electrical installations of an industrial site, during

  several days before its return to service.

  No device allowing such charging or discharging of a high power electrical network exists at present, however low or medium power charging devices exist and allow charging of the medium power network by threshold with times of high reactivity. Indeed, in the field of low or medium power load banks the variation of the load is done by threshold thanks to electromagnetic control relays which, applied to high power loads, would require too many relays increasing so critically the time to

  reaction as well as the cost of such a device.

  One of the aims of the invention is therefore to overcome these drawbacks by proposing a linear variation charge or discharge bank for a high power electrical network so that the network is charged or discharged in such a way linear with great

  responsiveness and at a moderate cost.

  In order to meet these objectives, the subject of the present invention is a device for charging or discharging a high-power electrical network comprising in particular sensors mounted on a three-phase network, a programmable controller which processes the information supplied by the sensors, a trip card, a dimmer and a dissipative circuit; this device is remarkable in that the dimmer is constituted by a limited number of thyristors, mounted two to two spade heads and in parallel, and thus allowing the charging or discharging of the high power network of

linearly.

  According to a particularly advantageous variant of the invention, certain thyristors of the dimmer can

  be replaced by electromagnetically controlled relays.

  Another characteristic of the device according to the invention consists in the fact that the sensors are current transformers constituted by polarized toroidal coils; in the application to the load bench, the device is characterized in that the current transformers are mounted in opposite directions on the three-phase network to measure the reactive power present on the network. Other advantages and features will emerge

  better from the following description, from several

  alternative embodiments, given by way of nonlimiting example, of the device according to the invention intended to charge active power or dissipate reactive powers in a three-phase network, with reference to the attached drawing in which: - Figure 1 is a general representation

  schematic of the device according to the invention.

  - Figure 2 shows a block diagram of

  operation of the device according to the invention.

  With reference to FIG. 1, the device mainly comprises three sensors 1a, 1b and 1c mounted respectively on the three phases 2a, 2b and 2c of the three-phase network. These sensors la, lb and lc collect data in terms of intensity, power and voltage on the network, data which are subsequently transmitted to a programmable controller 3 whose main function is to process the information collected by said sensors la, lb and lc . The programmable controller 3 is itself connected to a so-called safety circuit 4 which controls the information processed in particular in voltage, current and power, thus allowing regulation of the various information, in particular in the event of overcurrent in resistive loads which will be detailed more far. This safety circuit 4 also allows the analog data processed in the programmable controller 3 to be reset to zero.

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  or even the emergency stop of the device. The programmable controller 3 is also connected to a trigger card 5 with which it continuously exchanges information. This trigger card 5 controls the triggers of the thyristors 6 fitted to the dimmer 7. According to a first embodiment of the invention and in accordance with FIG. 1, the dimmer 7 consists of six thyristors 6 mounted two by two head to tail and in parallel forming thus three pairs 8a, 8b and 8c of thyristors 6. Such an assembly of the thyristors 6 mounted two with two spades and in parallel, makes it possible to load and unload the three-phase network 2a, 2b and 2c in accordance with the object of the invention, the thyristors 6 do not tolerate reverse voltage across their terminals. The upper terminals 9a, 9b and 9c of the respective pairs 8a, 8b and 8c are respectively connected to phases 2a, 2b and 2c of the three-phase network and the lower terminals 10a, 10b and 10c are respectively connected, in this particular and non-limiting example of realization, with three-phase resistive loads 11a, 11b and 11c thus allowing a discharge of the reactive power of the three-phase network, by transformation into heat energy which it is advisable to evacuate; for this purpose the device according to the invention provides a fan 12 to allow continuous cooling of the resistive loads 11a, 11b and 11c and thus ensure continuous charging or discharging of the three-phase electrical network 2a, 2b and 2c. This fan is incidentally controlled by an automatic peripheral control 13 which is itself connected to the programmable controller 3 with which it exchanges information continuously. According to a particular arrangement of the dimmer 7, one or more thyristors 6 can be replaced by one or more electromagnetically controlled relays. This type of mixed dimmer then makes it possible not to have too great a reactivity within the framework of an unbalanced electrical network as well as to reduce the cost of such a device.

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  With reference to FIG. 2, we will now describe in

  detail the operation of the device according to the invention.

  In accordance with the first step, the information on power, voltage and intensity on the three-phase electrical network 2a, 2b and 2c is carried out using intensity transformers la, lb and l1, constituted as we have already said by polarized toroidal coils. These intensity transformers la, lb and l1, and more precisely these polarized toroidal coils are mounted upside down on each of phases 2a, 2b and 2c of the three-phase electrical network in order to be able to detect the reactive power actually present on said electrical network . The information transmitted by these sensors is first of all processed by a power transmitter which transforms them into voltage setpoints which vary between 0 and 10 Volts so that the programmable controller 3 can process them. This programmable controller 3 operates first of all the acquisition of the data, which can be external data coming from the peripheral control automation 13 or even from the security card 4 allowing, for example, a reset of the analog data or well again an emergency stop. The automaton 3 then operates a data processing step which consists in comparing the data supplied by the sensors la, lb and lc with a

preset power threshold.

  It goes without saying that this threshold can be modified according to the use of the device according to the invention, this threshold will therefore depend on the initial characteristics of the three-phase electrical network 2a, 2b and 2c as well as on the final characteristics which it is desired to obtain on

  said three-phase electrical network.

  In this regard, if the power threshold initially defined is exceeded, then the programmable controller 3 transmits a power command to the trigger card 5 in proportion to the set voltage varying as we have seen between 0 and 10 Volts. The

I. I I T

  - 6 trigger card 5 first requests an order confirmation from the programmable controller 3 for safety reasons, then once the power order is confirmed, the trigger card actuates the triggers of the thyristors 6 contained in the dimmer 7 by varying the phase angle of the current delivered across the terminals of the

thyristor triggers 6.

  It goes without saying that the triggering of the triggers of the thyristors 6 can be obtained by means of a wave train or by any other equivalent means known to those skilled in the art. The triggering of the triggers then allows the loading of active power, for example, active power which will be dissipated in the resistive loads 11a, 11b and 11c. This device, as described in this nonlimiting example, therefore allows a linear variation of active or reactive load in high power for purely electrical use, which allows, for example, to maintain constant characteristics, in power, on a network. type of electricity supplier or an autonomous network of the generator type. It goes without saying that a thyristor cooling circuit is necessary but not shown in FIG. 1. This circuit mainly consists of a simple fan which therefore ensures the cooling of the thyristors. Finally, it is obvious that it will always be possible to adjust the value of the resistive loads according to the envisaged application, the examples cited in the

  description given for information only and in no way

  limiting cases as to the fields of application of the device. -7

Claims (5)

RESELL I CATIONS   1 - Device for charging or discharging a high-power electrical network comprising in particular sensors (la, lb, lc) mounted on a three-phase network (2a, 2b, 2c), a programmable controller (3) which processes the information supplied by the sensors (la, lb, lc), a trip card (5), a dimmer (7) and a dissipative circuit (11) characterized in that the dimmer (7) consists of a limited number of thyristors ( 6), mounted two to two head to tail and in parallel, to allow the charging or discharging of the high power network of linearly.   2 - Device for charging or discharging a high power electrical network according to claim 1 characterized in that certain thyristors (6) of the dimmer (7) can be replaced by relays with electromagnetic control.   3 - Device for charging or discharging a high power electrical network according to any one of   claims 1 and 2 characterized in that the   sensors (la, lb, lc) are current transformers   constituted by polarized toroidal coils.   4 - Device according to claim 3 characterized in that the current transformers are mounted in   opposite direction on the three-phase network (2).   5 - Device for charging or discharging a high power electrical network according to any one of   claims 1 to 4 characterized in that the circuit   dissipative consists of resistive charges (lla, llb, lc) and cools by a fan (12) allowing the transformation of electrical energy into heat energy.