AU427651B2 - Circuit breaker - Google Patents

Description

2 4,9 21/7f The present invention relates to circuit breakers or cut-out switches adapted to open an electric circuit and more particularly to a high-or very high- bower Circuit, such as for example an element in a supply network, a circuit for carrying out experiments in the course of which it is necessary to employ very high intensities and/or very high voltages such as 10,000 amps at 2,000 volts with an a-c or d-c current. For breaking such circuits there has been suggested the utilization of the energy of a pyrotechnic element, the explosion opening the circuit by the self- destruction of the break switch. However, in the numerous known arrangements the problem of the arc produced when breaking the circuit has not been solved in a satisfactory manner. An" object of the present invention is to provide a very simple solution to this problem. The invention provides a circuit breaker having a Pyrotechnic element, wherein said element is disposed in. the centre of a case having an electrically conductive wall provided with a line of reduced resistance dividing the case irnto two parts, the case being filled with a liquid having a high insulating power which is ejected between the lips of the two parts of the case when the case is broken -by the explosion of the pyrotechnic element prevents and/the production and maintenance of an arc between said lips. The insulating liquid moreover performs two other im~portant functions

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24.921/71 It transmits in a definite manner to the wall of :he case the pressures resulting from the explosion of the ,yrotechnic element. It absorbs the expansion of the gaseous and/or ;oli' products of this explosion. Thus the circuit breaker according to the .nvention permits the overall size to be considerably ecreased the construction to be greatly simplified, which .s essential to guarantee reliable operation and economy )f use. There is also an improved rapidity of action and .mproved reproducibility of the latter, which are essential features when it is necessary to synchronize (possibly bear- .ng in mind phase differences) the operation of the circuit )reaker,for example to cut off an electric energy generator )r a part of an electric energy supply network. The circuit

)reaker also has a high intrinsec safety (that is, it is rery insensitive to parasite excitations). Another object of the invention is to provide icircuit breaker system comprising, in each of the :ircuits to be broken simultaneously, a circuit breaker laving a pyrotechnic element of the type defined herein- >efore, all the circuit breakers having their primers :onnected to an ignition circuit. Further features and advantages of the invention till be apparent from the ensuing description with reference o the accompanying drawings.

In the drawings Fig. I is a longitudinal sectional view of an .mproved circuit breaker according to the invention;........

Fig. 2 is an putside view of this circuit breaker ;hown in three stages of operation A, B, C;

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2 4.921/71 Fig. 3 is a longitudinal sectional view of a modification of the circuit breaker; Fig. 4 is a plan view of the circuit breaker shown in Fig. 3;

Fig. 5 shows an arrangement of a circuit breaker according to the invention inside a protective cover, and Fig. 6 is a diagram of a system of three circuit breakers accordingto the invention in a three-phase supply network.

S With reference to Fig. 1, which shows a circuit breaker or cut-out switch C in its preferred form, the circuit breaker comprises a -metal case I of revolution about an axis X-X and constituting a closed housing. The case has a blind aperture 2 followed by a bore 3 and a tapped counter-bore 4 adapted to receive a screwthreaded plug

Disposed in facing relation at the ends of the bore 3 are a part-conical face of a member 6 constituting a further terminal and provided with a stem 7 engaged in the blind aperture 2 which thus centers the further terminal, and a part-conical face of an insulating member 8 provided with a flange 9 which is trapped between a shoulder of the case and the plug

Axially fitted in the member 8 is a support 11 for a pyrotechnic element constituted by a primer-detonator 12. The latter is ignited electrically by volatilization of an element 13 through which an ignition current is passed, this current being supplied by conductors 14 which extend out of the circuit breaker through coaxial bores 15 and 16

4 427651 in'the members 8 and 9 respectively.

The space between the facing part-conical faces of the members 6 and 8 and the bottom of the blind aperture 2 are filled with insulating oil 17 in which is immersed the pyrotechnic element 12. An O-section ring 18 renders the assembly fluidtight.

Provided roughly in the middle of the length of space filled with oil, and.in the region of the element 12, is a line of reduced resistance in the case in the form of a circumferential groove 19 which is formed in the outer face of the case 1 and divides the latter into two parts la, lb.

The case has two tabs or terminals 20 and 21 for its insertion, for example by means of bolts, between two elements such as two bars of the circuit to be broken. The metal case I can be advantageously of an aluminium alloy, such as the alloy A5 as defined by the French standard NFA 57-650, have the following properties:

annealed Mean Meanhreaking load The primer-detonator 12 is preferably of the known type having a wire exploded without primary pyrotechnic compositions. This primer-detonator is charged solely with "secondary,"explosive such as pentrite and its low sensitivity ensures optimum operational reliability and safety. The oil 17 employed can have for example the following properties

Dielectric rigidity at 250 35 KV per 2.5 mm 0 Viscosity at 25 C 2.-0.5 cxntisldkes

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24,921/71 The circuit breaker according to the invention

operates in the following manner

With reference to Figs. 1 and 2, when the

detonator 12 is made to explode by an excitation by a

current outside the circuit breaker provided by some known

means, as the discharge of a capacitor, oil 17 subjects

the wall of the case 1 to a high radial pressure of expansion,

the part-conical faces of the members 6 and 7 concentrating

the shock waves on the case. Under the pressure of the oil

17, the case first expands or swells (stage A, Fig. 2) and

the groove 19 is enlarged to 19a, then the case breaks into

two parts la and lb along this groove (stage B, Fig. 2) and

provides two breakage lips 23, 24.

The power of the detonator is so calculated, bearinc

in mind the nature and thickness of the wall of the case 1,

that the two parts of the wall very quickly assume the shape

of petals 25, 26 (stage C) which open and then symmetrically

fold back with respect to the initial plane Y-Y of the

groove 19 while remaining attached to the corresponding part

of the case. Thus there is no projection of metal splinters.

The insulating oil 17, under the pressure causing

the bursting of the wall of the case, is itself subjected

after this bursting to a residual pressure which expels it

at 17a between the metal lips 23 and 24 throughout the

circumference of these lips and thus prevents any formation

of an arc between the lips.

Tests have shown that, with the aforementioned

materials

The time delay between :the address of the firing

order and the start of the breakage of the conductive

tube is 3 0.3 10 seconds.

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2 4,9 21 /7 The speed of radial expansion of the liquid 17 case immediately after fracture of the groove 19 in.the

is 370 m/sec.

In addition to the aforementioned advantages,

the following may be mentioned

the relative nature and disposition of the

elements of the circuit breaker are such that it is always circuit to be easy to integrate the circuit breaker in the

broken substantially without increasing the initial

impedance of the latter;

the electrically conductive case 1 ensures circuit the initial continuity in the circuit in which the

breaker is integrated;

as the pyrotechnic element is placed in the

centre of the case, its operation results in a symmetrical

explosion of the latter; the insulating liquid 7 having a high

dielectric rigidity completely fills the space unoccupied

by the pyrotechnic element.

Figs. 3 and 4 show another form of circuit

breaker C' according to the invention. The case 1' has

of a generally spherical shape and an equatorial line

reduced resistance in the form of an outer groove 19' lb'. The which divides the case into twvo.hemispheres la',

primer-detonator carrier 11' is fixed in a radial position

to the case 1' by a nut 27 with interposition of insulating

washers 38, 39 andan insulating spigot 30. The centre

detonator 12 is ignited as in the first embodiment by vol-

atilization of the filament.

The operation of this circuit breaker is identical

to that of the first embodiment.

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24.921/71 Either of the embodiments C, C' of the circuit

breaker can be if desired surrounded by a cover 31 which

precludes projection of the oil. This cover can be for

example composed of glass-wool and have such strength that

even if the circuit breaker operated in an accidental

manner, this occurs without danger to an operator holding

it in his hand. Fig. 5 shows such a cover 31 in the case

of a circuit breaker C according to the first embodiment.

By way of example,Fig. 6 shows a circuit breaking

system for a three-phase network or supply.- In each of the

conductors 32 of this network there is disposed, as illustr-

ated, a circuit breaker according to *he invention of the

type C shown in Figs. 1-3 or a circuit breaker of the type

shown in Fig. 4 which may have if desired a protective

cover.

S- The filaments for igniting the primer-detonators

of these circuit breakers are connected in parallel through

the conductors 14 to a firing device 33 which is supplied with current through a conductor 34 by a source of current

which receives the firing order from a receiving device

36 which responds to the event (electrical or other event)

which must cause the opening of the network 32. This

responsive device 36 is connected to the firing device 33

through a shaping device 37. The latter is adapted to

convert the information from the receiver 36 into a firing

order transmitted to the firing device 33.

The devices 33, 36, 37 are well known in remote

control systems and therefore need not be described in

detail.

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_i_

Claims (1)

1. 24.9211/7 The claims defining the invention are as follows

   1. A circuit breaker having a pyrotechnic element

   for a high-or very high-power circuit, wherein said

   element is disposed in the centre of a case having an

   electrically conductive wall provided with a line of

   reduced resistance dividing the case into two parts, the

   case being filled with a liquid having a high insulating

   power which is ejected between the lips of the two parts

   of the case when the case is broken by the explosion of the

   pyrotechnic element and prevents the production and

   maintenance of an arc between said lips.

   A circuit breaker as claimed in claim 1,

   comprising a cylindrical case to which are attached two

   members having facing part-conical faces adapted to deviate.

   in the direction of the cylindrical wall of the case the

   shock waves due to the explosion of the pyrotechnic element,

   the line of reduced resistance being a peripheral groove

   contained in a transverse plane perpendicular to the long-

   itudinal axis of the case and located at roughly.equal

   distances from the two part-conical faces.

   3. A circuit breaker as claimed in claim 1,

   wherein the case is generally spherical in shape and

   comprises two hemispherical parts interconnected by the. bottom of an equatorial groove constituting the line of

   reduced resistance.

   4. A circuit breaker as claimed in any one of

   the preceding claims, wherein the pyrotechnic element is

   a primer-detonator charged with a "secondary" composition

   such a pentrite.

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   2 49 21171 A circuit breaker as claimed in any one of liquid is an the preceding claims, wherein the insulating

   oil having the following properties 0 Dielectric rigidity at 25 about 35 KV per 2.5 mm 0 2.8 0.5 centistokes. Viscosity at 25

   6. A circuit breaker as claimed in any one of

   the preceding claims, wherein the case is of aluminium

   having the following properties annealed

   Mean 38%/

   Mean breaking

   7. A circuit breaker as claimed in any one of with a the preceding claims, wherein the case is provided

   protective cover of glass-wool or the like. 8. A circuit breaking system comprising in

   each of the circuits to be broken simultaneously, a circuit

   breaker having a pyrotechnic element according to any one

   of the preceding claims, all of the circuit breakers having

   their primers connected to one ignition circuit.

   9. A circuit breaker having a pyrotechnic

   element for a high- or very high-power circuit, substantially in as hereinbefore described with reference to and as shown

   Figs. 1 and 2 of the accompanying drawings. A circuit breaker having a pyrotechnic

   element for a high- or very high-power circuit, substant-

   and as ially as hereinbefore described with reference to

   shown in Figs. 3-5 of the accompanying drawings.

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   2 4,9 21 /71 Dated this 28th day of' January, 1971

   COMPAGNIE FRIANCAISE THOMPSON HOUSTON- HOTCHKISS BRANDT By its Patent Attorneys A. WALLACE SMITH CO.

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