WO2017178761A1

WO2017178761A1 - Electrical circuit breaker with liquid vaporization system

Info

Publication number: WO2017178761A1
Application number: PCT/FR2017/050883
Authority: WO
Inventors: Sylvain NICHELE; Christophe Creusot
Original assignee: Supergrid Institute
Priority date: 2016-04-13
Filing date: 2017-04-12
Publication date: 2017-10-19
Also published as: FR3050312A1

Abstract

The invention relates to a medium- or high-voltage current breaking system comprising an arc-extinguishing chamber comprising, in a closed enclosure (10), a pair of arc contacts (4, 5), one (5) of the contacts being movable with respect to the other (4) under the action of a maneuvering member (13), the contacts separating while forming an electric arc in an arc zone (16) inside the enclosure (10). According to the invention, the system is characterized in that it also comprises an injection means (20) suitable for injecting, into an injection zone (17) adjacent to the arc zone (16) (or comprising it), a predefined volume of liquid in a first time that is shorter than a second time required for the appearance of the arc, which second time is composed of a time required by the maneuvering member to take account of a control signal for opening the contacts and setting the contacts in motion and a time required by the maneuvering member to move the contacts until the moment when the contacts physically separate while forming the electric arc. Application to the production of medium- or high-voltage circuit breakers.

Description

Electric circuit breaker with liquid vaporization system

Technical field and state of the art

The invention relates to a current interruption system (or electric circuit breaker), of the type comprising a breaking chamber. In known manner in particular from document WO2016 / 005435, an interrupting chamber comprises (FIG. 1), in a closed enclosure 10, a set of two pairs of arcing contacts 2, 3 and 4, 5, each 2, 5 being relatively movable relative to the other 3, 4 under the action of an operating member 13. The contacts 2 and 3 ensure the passage of the permanent current when the circuit breaker is closed by limiting losses by Joule effect. The contacts 4, 5 are dedicated solely to the passage of the highly destructive electric arc that is generated during the opening of the circuit breaker, at the precise moment of the physical separation of the contacts 4, 5. To cut the current, an opening phase Contacts take place as follows. Initially, the contacts 2, 3 are touching and the contacts 4, 5 are also touching (see Fig. 1) so that an electric current flows through the two contacts 2, 3. When the operating member 13 receives a opening control signal, the operating member 13 moves the relative contact 2 relative to the contact 3 as well as the contact 4 relative to the contact 5. Then the contacts 2, 3 will physically separate. From this precise moment, the electric current begins to circulate only in the contacts 4, 5 which continue to move relative to each other. As long as the contacts 4, 5 touch each other (although in motion), the current continues to flow through the two contacts 4, 5. In contrast, at the moment when the contacts 4, 5 physically separate, that is to say at the moment when the contacts 4, 5 have no common surface, an electric arc arises from the two contacts, in an arc zone inside the enclosure. The electric arc allows the electric current to continue to flow through the contacts 4, 5 which continue to deviate relative to each other. To stop this passage of the current and thus achieve the cut, the electric arc is elongated due to the distance of the contacts 4, 5, then blown until it is extinguished. The contacts 4, 5 continue to move away from each other to a position called "open" where the distance between the two contacts is such that there is more risk than an electric current settles again between contacts. The opening phase is then complete. The chamber is filled with gas, typically SF6; thanks to the dielectric properties and the electronegativity properties of SF6 gas, the medium ionized by the electric arc forming at the time of the separation of the contacts quickly finds good insulating properties by attachment of free electrons on SF6 ions. SF6 has established itself as the reference gas for switching off AC high-voltage lines (HVAC). But because of the impact of SF6 on global warming, solutions are being sought to replace SF6 gas. Among the more environmentally acceptable alternatives, studies are being conducted on carbon dioxide (CO2), nitrogen (N2) or even air. However, these gases have dielectric, electronegativity and / or thermal performances which are less interesting than SF6 and, when dimensioned similarly, the circuit breakers using these gases do not make it possible to cut currents as high as the currents that an SF6 circuit breaker can cut. To compensate for this lower performance, it is also known to inject into the arc zone or near the contacts a liquid whose vaporization will help cut. For this, a pump 15 filled with liquid is conventionally positioned inside the interrupting chamber and the liquid injection is performed at the moment of the arc, by a piston 14 actuated by the operating member 11 (FIG. 1). The liquid injected into the arc zone is vaporized because of the very high temperature generated by the arc. The ions, especially H and F, released in the arc zone help to blow the arc and keep the dielectric medium after the cut.

However, the liquid injection is difficult to achieve because it must be performed under very strong constraints. The quantity of liquid must be perfectly controlled: too much liquid could result in an overpressure in the enclosure of the arc chute with risk of explosion. In addition, in case of excessive liquid injection, a quantity of liquid may not be vaporized but be carbonized and then come "pollute" the inter-electrode space; this would lead to a degradation of the dielectric strength of the medium. Finally, some liquids can have a significant cost; to inject strictly the necessary quantity of liquid thus also makes it possible to limit the cost of the device.

Moreover, the injection member must be very fast to inject the liquid into the future arc zone during the opening of the circuit breaker. Indeed, the temperature and the pressure are very important in the arc zone at the moment when the arc burns between the two contacts 4, 5. This arc formed from the physical separation of the contacts 4, 5 is a medium. viscous "in which the injected liquid has great difficulty in penetrating: generally, the injected liquid bounces on the surface of the arc.

Finally, because it is occasionally necessary to open and close the contacts several times in succession (OFO cycle), for example in case of electrical fault on the line, it is essential to be able to perform a liquid injection several times, and even several times in a row. However, no simple technical solution is proposed to replenish the liquid injection device several times, possibly at relatively short time intervals.

Description of the invention

The invention proposes a new breaking system, not exhibiting all or part of the disadvantages of the known systems.

For this purpose, the invention proposes a current interruption system comprising an interrupting chamber comprising, in a closed enclosure, a pair of arcing contacts, one of the contacts being movable relative to the other under the action of an operating member, the contacts separating forming an electric arc in an arc zone inside the enclosure. The system according to the invention is characterized in that it also comprises an injection means adapted to inject, in an injection zone adjacent to the arc zone or comprising the arc zone, a predefined volume of liquid in a first time less than a second time necessary for the appearance of the arc, second time composed of a time required for the operating member to take into account a contact opening control signal and put in motion the contacts and a time required for the operating member to move the contacts until the contacts physically separate by forming the electric arc.

Thus, according to the invention, the liquid is injected into the enclosure of the interrupting chamber after the supply of the contact opening control signal but before the appearance of the electric arc. It is recalled that the electric arc arises at the time of the physical separation of the contacts, so after the operating member has taken into account a contact opening control signal and has set in motion one of the contacts relative to the other, but before the contacts are immobilized in a fully open position. Before the physical separation of the contacts and the formation of the arc, the temperature and the pressure are still limited in the breaking chamber, well below the temperature and the pressure generated by the electric arc, and the medium in which the liquid is injected is still gaseous, not "viscous". It follows much easier injection conditions, resulting in a volume of adequate liquid totally injected immediately available to be vaporized at the time of the appearance of the arc to extinguish.

Preferably, the first time is less than a third time required for the operating member to take into account the opening control signal. This ensures that the injection is performed before any movement of the contacts, so well before the creation of the arc and a first rise in pressure in the interrupting chamber.

More preferably, the first time is less than 15 ms, the first time being equal to a time required to take into account a control signal by the injection means plus a time necessary to inject the predefined volume. of liquid. Such a short first time ensures that the liquid is completely injected before the arcing contacts have begun to separate. According to one embodiment, the cut-off system also comprises a control device adapted to simultaneously produce the opening control signal for the operating member and the injection control signal for the injection means when fault is detected. In known manner, connected to the electrical network that it monitors, a protection relay can provide an opening command to the control device when it detects a fault on the electrical network. Thus, the liquid is injected into the interrupting chamber only when the breaking conditions are particularly difficult because of the presence of a fault current generally much higher than the current flowing normally in the line. In the absence of fault current, the gas initially present in the interrupting chamber is sufficient to blow the arc (much lower energy) and allow the cut.

A receptacle such as a cup may be positioned in the injection zone to receive the injected liquid. According to one embodiment, the injection means according to the invention comprises a pump comprising a tubular body in which a piston defines an injection chamber, an outlet of which is connected to the injection zone in the interrupting chamber, the piston being movably mounted between:

• an initial position where the injection chamber has a volume equal to the predefined volume of liquid to be injected, · an end position where the injection chamber has a zero volume.

Alternatively, the total stroke of the piston is set and the volume of the pump body determines the predefined volume of liquid injected at each activation of the piston to achieve the desired performance. According to another variant, the initial position of the piston can be adjusted precisely according to the volume of liquid to be injected. The injection means also comprises a first valve positioned between the injection chamber and the interrupting chamber and adapted to:

• allow the passage of the liquid to be injected from the injection chamber to the interrupting chamber when the piston moves from its initial position to its final position, and

• prevent a possible return of liquid from the cutting chamber to the injection chamber when the piston moves from its final position to its initial position.

The injection means further comprises a reservoir of liquid to be injected, an outlet of which is connected to an inlet of the injection chamber via a second valve of the injection means, said second valve being adapted to:

Allow the passage of the liquid to be injected from the reservoir to the injection chamber when the piston moves from its final position to its initial position, and

• prevent a possible return of liquid from the injection chamber to the reservoir when the piston moves from its initial position to its final position.

The presence of a reservoir of liquid to be injected makes it possible to refill the injection chamber of the pump immediately after an injection. Thus the injection means is ready to be reused in a very short practical time, similar to the time required to inject the predefined volume into the interrupting chamber.

The injection means also comprises a purge member adapted to evacuate any gas from the injection chamber before or at the time of a first filling of the injection chamber. The absence of gas in the injection chamber ensures that any movement of the piston is immediately translated by a movement of liquid (and not a gas compression), and thus allows to control precisely the amount of liquid to be injected .

The injection means, and if necessary the reservoir, may (may) be positioned outside the interrupting chamber. The conditions of installation and maintenance of the injection means are thus facilitated, in particular the filling of the reservoir for successive uses. In addition, the injection means outside the interrupting chamber is only subjected to ambient temperature and pressure conditions which makes its sizing easier, lighter; finally, the risk of undesired vaporization of the injection liquid inside the injection chamber or the reservoir is discarded.

Finally, according to one embodiment of the invention, the breaking chamber is filled with a gas selected from carbon dioxide, nitrogen, air or a combination of these gases; the injected liquid can in turn comprise compounds of hydrogen and / or fluorine. Hydrogen has very interesting thermal properties to remove from the arc zone a significant part of the energy released at the time of the cut. Fluorine is very electronegative and thus easily captures the electrons released during the cut. Thus, fluorine makes it possible to limit the risk of restarting an electric arc in the second phase of electrical failure, when a very difficult transient recovery voltage appears at the contacts when the current is cut off.

Brief description of the figures

The invention will be better understood, and other features and advantages of the invention will emerge in the light of the following description of an example of a breaking system according to the invention. This example is given as a non-limiting example. The description is to be read in conjunction with the accompanying drawings in which

· Figure 1 shows a known breaking chamber,

FIG. 2 is a block diagram of a breaking system according to the invention,

FIGS. 3a, 3b are a functional representation of an injection phase in a breaking system according to the invention and

FIGS. 4a, 4b are a functional representation of a refueling phase of a breaking system according to the invention.

Description of Embodiments of the Invention

As said above, the invention relates to a power failure system (electric circuit breaker) comprising a breaking chamber; the interrupting chamber comprises (Figs.1-2), in a closed enclosure 10, a pair of arcing contacts 4, 5, one of the contacts being movable relative to the other (the two contacts may be movable ) under the action of an operating member 13. During the physical separation of the contacts, an electric arc is formed in an arc zone 16 inside the enclosure 10. The enclosure is filled with a gas, for example carbon dioxide, nitrogen, air or a combination of such gases, replacing the SF6 gas commonly used.

The system according to the invention also comprises an injection means 20 for injecting into an injection zone 17 adjacent to the arc zone 16 (or comprising it) a predefined volume of liquid. In the example shown in FIG. 2, the injection means is positioned outside the interrupting chamber, to facilitate the maintenance and filling operations of the injection means without opening the circuit breaker (see even without the turn off the filling time). Also, a receptacle 18 such as a cup is provided in the injection zone to receive the injected liquid.

The system according to the invention also comprises a control device 40 adapted to simultaneously control, via the control signals 41, 42, the operating member and the injection means when it receives an opening command issued by the relay. protection 50 having detected an electrical fault on the electrical network 60 that it monitors continuously.

The control device is also adapted to control, via a signal 43, only the operating member for an opening of the contacts 4, 5, when no fault current is detected on the network 60. In this case indeed, the energy of the arc at the moment of the cutoff is much lower than in the case of a fault current, the gas present in the chamber of the arc chute is sufficient to blow the arc and it does not it is not necessary to inject liquid. This is the case for example when the opening of the contacts is triggered by an operator.

According to the invention, the injection of the liquid is firstly less than a second time required for the operating member to take into account an opening control signal 41 of the contacts 4, 5 and physically separate the contacts , and preferably less than a third time required for the operating member to take into account the opening control signal 41. The first time is equal to a time required to take into account a control signal of injection 42 by the injection means 20 plus a time required to inject the predefined volume of liquid.

Figures 3 and 4 show a preferred embodiment of an injection means according to the invention comprising a pump 21 and a reservoir 27. The pump comprises a tubular body 22 closed at one end 22a; in the body 22, a sliding piston 23 defines a variable volume injection chamber; the piston is driven in motion by a jack (not shown but whose action is shown schematically by an arrow in Figs.3a, 4a); at the end 22a, an outlet of the injection chamber is connected to the breaking chamber 10 in the injection zone 17 via a pipe on which is mounted a first valve 24; on a pipe connecting an inlet of the injection chamber to an outlet of the tank 27 is mounted a second valve 25. According to a variant, the injection means does not comprise a reservoir of injection liquid and the inlet of the injection chamber is connected to a liquid distribution network for example.

According to one embodiment, the first valve and / or the second valve are check valves likely to let a liquid pass in a single direction under the pressure of said liquid. According to another embodiment, the first valve and / or the second valve are electro-pneumatic valves controlled by the injection control signal 41, the second valve being open after closure of the first valve.

The piston is here mounted mobile between two extreme positions: An initial position (FIG 4b) in which the injection chamber has a volume equal to the predefined volume of liquid to be injected; as an indication, the volume of the injection chamber is of the order of a few milliliters; for example, the predefined volume is of the order of 11 ml for a circuit breaker capable of cutting a current of 50 kA;

• an end position (fig.3b) where the injection chamber has a zero volume. The first valve 24 of the injection means is adapted to:

• allow the passage of the liquid to be injected from the injection chamber to the interrupting chamber when the piston moves from its initial position to its final position (Figs 3a, 3b), and

• prevent a possible return of liquid from the cutting chamber to the injection chamber when the piston moves from its final position to its initial position (figs.4a, 4b). The second valve 25 of the injection means is adapted to:

• allow the passage of the liquid to be injected from the reservoir to the injection chamber when the piston moves from its final position to its initial position (Figs 4a, 4b), and

• prevent a possible return of liquid from the injection chamber to the reservoir when the piston moves from its initial position to its final position (Figs 3a, 3b). Also, the pump 21 comprises a purge member 26 adapted to evacuate any gas from the injection chamber before or at the time of a first filling of the injection chamber. Finally, the injection means and the reservoir are positioned outside the interrupting chamber. The liquid in the reservoir may be composed of hydrogen atoms H with very advantageous thermal properties for absorbing the energy released by the arc towards current zeros and / or highly electronegative fluorine F atoms capable of easily capturing the electrons released at the time of the opening of the contacts and thus limit the risks of a restart of the arc.

In its most elaborate version, the operation of the breaking system according to the invention is as follows.

After installation of the breaking system according to the invention, the circuits of the injection means are first purged via the purge member 26 to expel any residual gas that may be present in the injection means of the circuits. The piston 23 is then brought to its initial position (FIG. 4b), the first valve 24 being closed and the second valve 25 being open: the injection chamber fills with injection liquid. The injection means is thus ready to be used.

When the control device detects a fault current on the line connected to the contacts 4, 5, the control device produces an opening signal 41 to the contact operating member and an injection signal 42 to injection means. Quickly, in the injection means, the piston of the pump is set in motion, the first valve 24 being open and the second valve 25 being closed. The liquid is pushed into the injection zone of the blowing chamber until the piston reaches its final position. The actuator has not yet physically separated the contacts, the arc is not yet formed and the pressure in the interrupting chamber is "low" which facilitates the work of the piston to inject the liquid into the chamber cut. After the end of the injection of the liquid, the operating member, slower than the injection means, then begins to physically separate the contacts 4, 5. When the contacts separate, an arc is created, the temperature and the pressure increases in the breaking chamber, the liquid is vaporized and the resulting gas helps to blow the arc to the zero of the current. Once the cut is achieved (arc off and contacts 4, 5 immobilized in the open position), the injection system can be filled again with liquid, by moving the piston 23 to its initial position, the first valve 24 being closed and the second valve 25 being open. In this case, a part of the liquid present in the reservoir 27 is sucked up to fill the injection chamber. The injection means is then very quickly ready for a next injection in the case of an OF-0 cycle, for example, with re-filling and injection times in line with those required to close and reopen the contacts. .

NOMEMCLATURE

4, 5 pair of contacts

10 closed enclosure

13 maneuvering body contacts

14 piston

15 pump

16 arc area

17 injection area

18 receptacle

20 injection medium

21 pump

22 bodies

22a closed end of the body 22

23 piston

24 first valve

25 second valve

26 purge organ

27 tank

40 control device / TerminalBar

41 control signal of the actuator in the event of a fault

42 command signal of the injection means in the event of a defect

43 control signal of the control unit in the absence of a fault 50 protection relay

60 electrical network

Claims

A medium or high voltage cut-off system comprising an interrupting chamber comprising, in a closed enclosure (10), a pair of arcing contacts (4, 5), one (5) of the contacts being movable relative to the other (4) under the action of an operating member (13), the contacts separating by forming an electric arc in an arc zone (16) inside the enclosure ( 10), characterized in that it also comprises an injection means (20) adapted to inject into an injection zone (17) adjacent to the arc zone or comprising the arc zone (16) a predefined volume of liquid in a first time less than a second time necessary for the appearance of the arc, second time composed of a time required for the operating member to take into account a contact opening control signal and put in motion the contacts and a necessary time to the maneuvering organ to move the contacts until the moment when the contacts separate physically by forming the electric arc.

2. Cutoff system according to claim 1 wherein the first time is less than a third time required for the operating member to take into account the opening control signal (41).

3. Cutoff system according to one of the preceding claims wherein the first time is less than 15 ms, the first time being equal to a time required to take into account an injection control signal (42) by the injection means plus a time required to inject the predefined volume of liquid.

4. Cutoff system according to the preceding claim also comprising a control device (40) adapted to simultaneously produce the opening control signal (41) for the operating member and the injection control signal (42) for the injection means when a fault current is detected on a monitored electrical network (60).

5. System according to one of the preceding claims also comprising a receptacle (18) such as a cup for receiving the injected liquid, said receptacle being positioned in the injection zone (17).

6. Cutoff system according to one of the preceding claims wherein the injection means comprises a pump (21) comprising a body (22) in which a tubular piston (23) defines an injection chamber whose output is connected to the interrupting chamber in the injection zone, the piston being movably mounted between:

An initial position where the injection chamber has a volume equal to the predefined volume of liquid to be injected,

• a final position where the injection chamber has a zero volume.

7. System according to claim 6 wherein the injection means also comprises a first valve (24) positioned between the injection chamber and the interrupting chamber and adapted to:

· Allow the liquid to be injected to pass from the injection chamber to the interrupting chamber when the piston moves from its initial position to its final position, and • prevent a possible return of liquid from the cutting chamber to the injection chamber when the piston moves from its final position to its initial position.

8. System according to one of claims 6 or 7 wherein the injection means also comprises a reservoir (27) of liquid to be injected, an outlet is connected to an inlet of the injection chamber via a second valve (25) of the injection means, said second valve being adapted to:

9. System according to one of claims 6 to 8 wherein the injection means also comprises a purge member (26) adapted to evacuate any gas from the injection chamber before or at the time of a first filling of the injection chamber.

10. System according to one of claims 8 to 9 wherein the injection means, and optionally the reservoir, is (are) positioned (s) outside the interrupting chamber.