EP1039495A2 - Method for limiting current in low voltage networks, its associated arrangement and special use of this arrangement - Google Patents

Abstract

A current-limitation procedure in which during operation with occurrence of load currents, the diffuse arcing modes of an arc occur and in the event of a short-circuit the arc is split into sequential partial arcs. Vacuum interrupters are used, and more specifically, at least one vacuum interrupter with at least one radial field contact is used, and in which the switch contacts generate a magnetic field extending perpendicularly relative to the direction of current in the arc, and a circulating arc is produced.

Description

The invention relates to a method for current limitation in low-voltage networks, in the case of the resulting operating currents diffuse arc modes of a Arc occur and in the event of a short circuit Splitting the arc into partial arcs one behind the other becomes. In addition, the invention relates to an arrangement to carry out the process as well as specific Uses this arrangement.

In low-voltage networks, switchgear and distribution boards must also handle short-circuit currents of up to 200 kA _{rms in} addition to the operating currents. Switching such currents with circuit breakers requires considerable technical effort and is associated with a drastic reduction in the service life of the switching arrangement in the case of selective switches. In the event of arcing faults, the high currents can result in major damage to systems and a serious risk to people. Circuit breakers are therefore required which interrupt these currents with as little effort as possible and / or significantly limit them. Components that can achieve such a limitation independently of a shutdown, in order to relieve the actual switching element, would also be suitable for the same purpose.

When using conventional air circuit breakers with Extinguishing sheet chambers can in the case of short-circuit shutdowns Low voltage networks possible prospective currents through the Voltage build-up of usually 300 - 400 V, that when running in of the arc in the quenching plate chamber occurs considerably be reduced. As a result, the Switching chamber work and the associated thermal loads of switching devices significantly reduced. To the others remain the current forces or those caused by them mechanical stresses in the power distribution considerably below the possible maximum.

Current-limiting devices continue to be used in the low-voltage range Components known that are based on carbon-filled, conductive polymers work where the conductivity for high current densities by several orders of magnitude the nominal current range decreases. Because of the comparatively low However, this principle is the conductivity of the polymers only applicable up to nominal currents of a few 10 A, because otherwise the transmission losses become prohibitively high.

The object of the invention is therefore to develop new methods for current limitation to propose and corresponding orders create and specify related applications.

The object is the subject of the Process claims resolved. Associated orders are indicated by the relevant property claims. The usage claims in contrast, contain specific uses the created arrangement.

In the context of the invention are therefore in the low and medium voltage range successful vacuum interrupters for one Current limitation used. Neither from the specialist or patent literature Up to now, current limiting devices have been used in practice Vacuum switching tubes or corresponding arrangements of vacuum switching contacts known.

In the invention, however, vacuum interrupters are used with such Contact configurations used in which an in Direction to the current in the arc transverse transverse magnetic field occurs, the arc through suitable divider plates is divided into partial arcs. Possibly the arc can also remain in one piece, in which If the divider plates outside the arc thread as Arc cooling plates are used.

The vacuum interrupters used in the invention with current-limiting property thus consists of at least two contacts with measures to generate radially directed Magnetic fields, at least one of which is in contact Movable direction of the power supply relative to the other contact is made of a vacuum-tight envelope, an insulator as well as a largely insulated electrically suspended Sheet package for main arcing enclosing main contacts.

A modified vacuum interrupter can advantageously be used be used in circuit breakers, which thereby get a current limiting function and therefore for Larger nominal currents can be used than with vacuum interrupters conventional design is possible. The vacuum interrupters are in a known manner in the operating state kept closed and when a fault occurs actively opened by a suitable drive mechanism.

Another advantageous area of application results from the possibility of switching tubes as a current-limiting fuse element to use. The key idea is the switching tube to keep closed for operating currents only by spring force. If a short circuit occurs, the is briefly occurring high currents between the contacts generated so high contact-withdrawing current force that the Disconnect contacts. By an appropriate mechanism can then be exceeded when a preset value is exceeded Release force release the springs so that the contacts by the magnetic forces as well as those acting in the arc Release the pressure force completely from each other. This allows the Contact arrangement the described current-limiting effect build up and the current flowing in the distribution network on im Low current values compared to the prospective short-circuit current limit. The rather passive vacuum interrupter in this case thus has a fuse-like, current-limiting Effect and can either work as a one-time backup used or with a suitable design, similar to a circuit breaker, can also be reset several times.

Figur 1

eine erste Anordnung von in einer Vakuumschaltröhre befindlichen Kontakten mit zugeordneten Lichtbogenteilerplatten in seitlicher Schnittdarstellung,

Figur 2

die Draufsicht auf eine Anordnung gemäß Figur 1,

Figur 3

eine bevorzugte Anordnung mit Kontakten für Transversalmagnetfelder in seitlicher Schnittdarstellung,

Figur 4

eine Draufsicht auf die Anordnung gemäß Figur 3,

Figur 5

eine Anordnung mit Topfkontakten zur Generierung eines radialen Magnetfeldes und zugehörigen Teilerplatten,

Figur 6

eine Draufsicht auf die Anordnung gemäß Figur 5,

Figur 7

eine Schnittdarstellung zur Verdeutlichung der Funktion der Teilerplatten und

Figur 8

unterschiedliche Beispiele für vom Stand der Technik vorbekannte Elektrodengeometrien.

Further details and advantages of the invention result from the following description of the figures of exemplary embodiments with reference to the drawing in conjunction with further subclaims. Show it

Figure 1

a first arrangement of contacts located in a vacuum interrupter with associated arc splitter plates in a side sectional view,

Figure 2

the top view of an arrangement according to Figure 1,

Figure 3

a preferred arrangement with contacts for transverse magnetic fields in a side sectional view,

Figure 4

3 shows a plan view of the arrangement according to FIG. 3,

Figure 5

an arrangement with pot contacts for generating a radial magnetic field and associated divider plates,

Figure 6

5 shows a plan view of the arrangement according to FIG. 5,

Figure 7

a sectional view to illustrate the function of the divider plates and

Figure 8

different examples of electrode geometries known from the prior art.

1 and 2, two contact bolts are shown in FIG the flows to contact carriers 3 and 4 with associated contact pads 9 are performed. There is an extinguishing arrangement 5 as it is known in principle from air switches, the consists of individual extinguishing plates 6a to 6j, one surrounding Ceramic limit 7 is present. The latter will clear from the top view of Figure 2.

Figures 1 and 2 thus show an arrangement that is those used in conventional low voltage circuit breakers Air switch chambers leaned, using suitable materials used for an indicated vacuum interrupter VS. become. This arrangement shows at high short-circuit currents good current limiting behavior. One in the area of the divider plates 6a to 6j stationary burning arc with several 10 kA can, however, if necessary, the divider plates and destroy the outer contact area affected by the arc and therefore do not allow a sufficient lifespan.

For the latter reason, the arrangement according to Figures 1 and 2 not for the actual operational switching of the general occurring operating currents, i.e. usually Currents from a few 100 A to a few kA are provided. The Arcing occurs between the contact pads of the separating contact pieces in the intense Fashion, but go into the with increasing contact distance diffuse fashion about. The approaches extend to the Electrodes over a large area and can also be used in unwanted Switch chamber areas burn. Such orders are therefore only to be used as securing elements.

In FIGS. 3 and 4, 11 and 12 mean two contact bolts for power supply, one of which is via a not shown Bellows is designed to be movable. Even the real one Vacuum interrupter is not shown in detail. There are contact pieces 13 and 14, each corresponding slots for generating radial or have transverse magnetic fields. Between laterally beveled contacts 13 and 14 is an arrangement 15 available, the individual from individual divider plates 16a to 16h and associated ceramic or metal parts. In particular, the divider plates 16a to 16k are on the end introduced into a ceramic holder 17 and is according to Figure 4 has at least one radial slot 18.

With this arrangement, one desired for current limitation Splitting the arc into consecutive ones Partial arcs in the event of a short circuit with simultaneous control of the diffuse arc mode that occurs with operating currents can be achieved. The arrangement is essentially from two contact pieces 13 and 14 and the arrangement 15 with the annular arc splitter plates 16a to 16h.

The basis of this embodiment is that the functioning of Vacuum switch contacts with radial magnetic field and rotating Arc is modified so that the circumferential Arc directed through the magnetic field into a stack of quenching sheets and thereby - while maintaining the rotation - into one Series of series-connected, rapidly rotating individual arcs is split up. Through this previously unknown Measure can both the thermal load of all affected contact parts are kept low as well at the same time such a large amount of burning voltage is built up be that the prospective short circuit current on in this Geometry controllable amplitudes is limited.

The layout of the contact pieces 13 and 14 is similar to that of the spiral contacts used in vacuum switching technology. In this case, the magnetic force acting on the intense arc that arises between the separating contact pads has components that drive the arc in the direction of a rotating race 19. During this arc hike, an extension of the arc is achieved by chamfering the contact pieces 13 and 14. During this movement process, the arc will switch to diffuse mode and thereby extend over the entire contact surface if a limit current of I _G ≈ 15-25 kA, which is dependent on the contactor diameter D, is not exceeded. In the case of instantaneous currents which are above this limit value, on the other hand, the arc remains in the contracted mode, whereby its voltage requirement during hiking increases as a result of the extension to a few 100 V and thus the current limitation becomes effective. In the vicinity of the race 19, the voltage requirement of a long arc will be greater than the sum of the voltage requirements of partial arcs, between two individual divider plates 16a to 16h or between the race 19 and one of the divider plates 16a to at least for the unstable arcing configurations that occur again and again Burn 16h. For such arcing configurations, the commutation of the long arc into the area of the divider plates and its division takes place within a few microseconds. In this process, the burning voltage and the associated current limitation are only insignificantly reduced. Only when the instantaneous current falls below the limit value I _G before the current zero does the arc withdraw from the divider plate area and switch to diffuse mode. It spreads over the contact surface, and the arc voltage also drops with decreasing current.

The running direction of between two of the divider plates 16a contracted arcs up to 16h is due to the local magnetic field determined by the current flow in the Contact pieces or races and the divider plates depends. The directions of individual partial arcs can therefore for the individual sheets, as in FIG. 7 for a section the divider plates and races are shown, different his.

Because the current-limiting effect when switching off if possible should start quickly and immediately with the build-up of the arc voltage connected, the arc must be rapid move from the contact pads towards the divider plates. In addition, the commutation in the area of the divider plates be done quickly so that re-ignitions in the back of the Arc and thus arc voltage drops can be avoided.

Windmühlenflügel-Kontakt", sind bei entsprechender Modifikation ebenfalls geeignet.These demands on the arc behavior can be met by the design of the switching elements and divider plates. The main body of the contact pieces should be made of oxygen-free copper (Cu) or the material of the contact pads such as. B. chrome copper (CrCu) or tungsten copper (Wcu) exist. Numerous investigations are known from the literature, according to which these materials are suitable for vacuum switching contacts with regard to their running and reigniting behavior. The contact pieces are preferably designed as spiral contacts and have 3-5, preferably 4 slots, which can be designed according to Appendix 4 or one of the in the application 19624920.1 v. June 21, 1996 have the forms described. The bevelling of the contact pieces should be characterized by an angle of inclination ψ with respect to the contact surface of ψ = 15 - 45 °, preferably ψ = 30 °, since the running behavior of the arc is only slightly influenced by new ignitions for this angular interval. The running area of the arc in the outer area of the spiral blades can, as shown in Appendix 2 as an example, also be formed by an additional race made of a burn-resistant contact material such as chrome-copper (CrCu), tungsten-copper (WCu) or tungsten-carbide-copper (WCCu) become. Other possible contact geometries with radial magnetic fields, such as the so-called contrate contact or the so-called

Windmill wing contact ", are also suitable with appropriate modification.

The material for the divider plates is both oxygen-free Copper (Cu) or chrome-copper (CrCu) due to their commutation behavior a flawless occurrence and arc running guarantee, as well as stainless steels on. When using magnetic stainless steels by amplifying the magnetic field component that the arc drives into the divider plates, the division of the arch be relieved. To avoid eddy current losses at nominal and operating currents, the divider plates should provided with at least one slot in the radial direction his. The width of the divider plates should be around b ≈ 0.1 - 0.3 * D, where D is the outside diameter of the contacts is. The width a of the races is usefully not larger than that of the divider plates; but it must be wider than be the largest base diameter. It will therefore chosen for a ≈ 0.5 - 1.0 * b.

In a modification of the arrangement according to Figures 3 and 4 well-known pot contacts used from vacuum switching technology. In the case of these pot contacts, there is a corresponding slot the radial magnetic field is generated in the carrier part of the pot. There must also be a bevel on the side so that appropriate divider plates can be inserted.

In FIGS. 5 and 6, 21 and 22 mean two contact bolts for power supply, one of which is via a not shown Bellows is designed to be movable. The real one Vacuum interrupter VS is again only hinted at. There are Pot contact pieces 23 and 24 available, as from the state of Technology are known. Through such slotted pot contacts can, provided two are symmetrically opposite Pot contact pieces 23 and 24 slots inclined towards each other have one with respect to the current direction in the arc Generate transverse magnetic field, so that such contact pieces also called radial field contacts. On the actual pot contacts 23 and 24 are for the actual Contact rings 29 applied from contact material. The Rings 29 have a corresponding to the arrangement of Figure 3 specific shape. It is special from the inside to the closed Condition of the switch contacting part via bevels achieved with a predetermined angle ψ that in the outer Area there is a larger free space. In this free space reach from the outside according to Figure 2 divider plates 26a to 26h, which are held on the outside by a ceramic part 27.

In the case of the pot contacts 23 and 6 shown in FIGS 24 each individual contact piece consists in particular of one Contact body 30, in the straight slots 31 under predetermined Incline are introduced.

On the basis of FIG. 7 it is clarified how in particular between the individual divider plates 6a to 6j from Figure 1 and 16a to 16h from Figure 3 or 26a to 26h from Figure 5 the division of the arc can take place. Thus, the desired one Effect of current limitation in vacuum reached.

8 shows four possible examples I to IV Geometries of the actual contact plate, as they do are known from the prior art. It is essentially about that in example I around the so-called spiral contacts, in which 100 spiral slots in a contact plate 101 to 104 are present and a circular one in the middle Indentation 105 is present in the contact plate 100. A such contact geometry ensures radial circulation of the arc.

For simplified production, in Example II are in one Contact plate 200 with a circular recess 205 three tangential straight slots 201 to 203 introduced. Here results essentially the same effect.

In Examples III and IV there are 300 in the contact plates or 400 with concentric recesses 305 or 405 as well straight slots 301 to 304 or 401 to 404 are present, which are bent at right angles in example III and in the example IV are provided with circular recess 205. Such Slots can also be comparatively easily inserted into existing ones Contact plates are introduced.

While the arrangement according to Figures 3/4 and 5/6 essentially for operational switching of high currents with Current limitation is provided, the arrangement according to the figure 1 and FIG. 2 essentially only as a current limiting or Monitoring element available, with which no reversible Work is possible.

Can be used as current limiting fuse elements in the arrangements according to the figures described, the contact pieces in the switching tube for the operating currents Spring force must be closed, when a short circuit occurs a contact-withdrawing current force is generated, which separate the contact pieces. It is for one in such a case also possible if a short circuit occurs to release a latching mechanism by means of the current and the contact pieces by spring force, pneumatic or hydraulic separate from each other.

In particular with the arrangements according to Figures 3/4 and Figure 5/6 there are rotationally symmetrical radial field contacts, where the circulating arc through the magnetic field and through the arc splitter plate while maintaining the rotation in a series of cascaded, fast rotating Single arc is split. In a certain The arc can also be modified in one piece remain, in which case the divider plates only as Arc cooling plates are used. According to FIG. 1/2 it is possible when using a vacuum interrupter with a transverse magnetic field and a non-rotationally symmetrical contact arrangement to realize a straight arc, the arc through the magnetic field and through at least an arc splitter plate while maintaining the motion in a series of individual arcs connected in series is split up. In a specific modification can with such a non-rotationally symmetrical Contact arrangement of the rectilinear arc also stay in one piece, in which case the divider plates outside of the arc path again as arc cooling plates serve.

Claims (23)

Process for current limitation in low-voltage networks, in which diffuse arc modes of an arc occur during operation with the resulting operating currents and in which, in the event of a short circuit, the arc is split into partial arcs located one behind the other, characterized by the use of vacuum interrupters. A method according to claim 1, characterized in that at least one vacuum interrupter with at least one radial field contact is used, in which the switching contacts generate a magnetic field running perpendicular to the direction of current in the arc and a circulating arc is effected, the circulating arc being generated by the magnetic field and by at least an arc splitter plate is split into a series of rapidly circulating individual arcs while maintaining the rotation (FIG 3/4, FIG 5/6). Method according to claim 1, characterized in that a radial field contact on the one hand and a slanted plate contact on the other hand are used. Method according to Claim 2, characterized in that at least one vacuum interrupter with at least one radial field contact is used, in which the switching contacts generate a magnetic field which is perpendicular to the current direction in the arc and a circulating arc is produced, the arc remains in one piece and the divider plates outside the arc path can be used as arc cooling plates (FIG 3/4, FIG 5/6). A method according to claim 1, characterized in that at least one vacuum interrupter with a transverse magnetic field is used and that an arc running in a straight line in a non-rotationally symmetrical contact arrangement is used, the arc through the magnetic field and through at least one arc splitter plate while maintaining the movement in a series of single arcs connected in series is split (FIG 1/2). Method according to Claim 5, characterized in that at least one vacuum interrupter with a transverse magnetic field is used and that an arc running in a straight line in a non-rotationally symmetrical contact arrangement is used, the arc remaining in one piece and the splitter plates outside the arc path being used as arc cooling plates (FIG. 1/2 ). Method according to Claim 1, characterized in that suitable, in particular oxygen-free, vacuum switch materials are used for the contact arrangement and the arc splitter plate. Arrangement for current limitation in low-voltage networks using the method according to claim 1 or one of claims 2 to 7, characterized by at least one vacuum interrupter (VS) with two switching elements (13, 14; 23, 24) and by annular arc splitter plates (16a - 16K, 26a - 26k), which are at least partially arranged between the switching pieces (13, 14; 23, 24). Arrangement according to claim 8, characterized in that the switching pieces (13, 14) have the shape of spiral contacts (100) in their plan. Arrangement according to claim 8, characterized in that the spiral contacts (100) have three to six, preferably four slots (101-104). Arrangement according to claim 8, characterized in that the switching pieces (13, 14; 23, 24) are bevelled in the zones which follow the actual contacting area in the radial direction outwards. Arrangement according to claim 11, characterized in that the bevelling of the switching pieces (13, 14; 23, 24) has an angle of inclination (ψ) with respect to the contact surface of 15 °> ψ ≤ 45 °, preferably ψ = 30 °. Arrangement according to claim 8, characterized in that at least the contact surface of the contact pieces (13, 14; 23, 24) made of a contact material which is resistant to erosion, preferably chromium-copper (CrCu), tungsten-copper (Wcu) or tungsten-carbide-copper (WCCu ), consists. Arrangement according to claim 8, characterized in that the divider plates (16a to 16k, 26a to 26k)) consist of oxygen-free copper (Cu) or chromium-copper (CrCu). Arrangement according to claim 8, characterized in that the divider plates (16a to 16k, 26a to 26k) consist of stainless steel, in particular magnetic stainless steel. Arrangement according to claim 14 or claim 15, characterized in that the divider plates (16a to 16k, 26a to 26k) have at least one slot (17, 27) in the radial direction. Arrangement according to claim 14 or claim 15, characterized in that the width (b) of the divider plates (16a - 16k, 26a - 26k) has a dimension of 0.1 D ≥ b ≤ 0.3 D, D being the outside diameter of the contacts ( 13, 14; 23, 24). Arrangement according to claim 8, characterized in that the contact pieces (13, 14; 23, 24) of the contact rings (19, 29) are formed which are a width (a) smaller than the width (b) of the divider plates (16a - 16k, 26a - 26k). Arrangement according to claim 18, characterized in that the width (a) of the races () corresponds to the dimensioning 0.5 b ≤ a ≤ 1.0 b. Arrangement according to claim 18, characterized in that the race (9, 19, 29) consists of a different material than the contact body ((3, 4; 13, 14; 23, 24). Arrangement according to claim 17, characterized in that the switching elements (3, 4; 13, 14, 23, 24) consist of oxygen-free copper (CU) or copper-chromium (CuCr). Use of an arrangement according to claim 8 or one of the Claims 9 to 20 as a current-limiting fuse element, the contact pieces (3, 4, 13, 14; 23, 24) in the switching tube (VS) closed for operating currents by spring force are and in the event of a short circuit a contact-withdrawing Electricity is generated and thereby the contact pieces (13, 14; 23, 24) are separated from each other. Use of an arrangement according to claim 8 or one of the Claims 8 to 21 as a current-limiting fuse element, wherein the contact pieces (3, 4, 13, 14; 23, 24) in the switching tube (VS) closed for operating currents by spring force and if a short circuit occurs due to current a latch mechanism is released and the contact pieces (13, 14; 23, 24) by spring force, pneumatic or hydraulic be separated from each other.

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