EP0548390B1 - Trip device for electrical switching gear - Google Patents

Abstract

The invention relates to a trip device for electrical switching apparatuses by means of an explosive charge (17) which can be detonated and causes the switching apparatus to trip, the explosive charge being formed by a pyrotechnic gas generator which acts on a pressure piston unit (16) which is coupled to the moving contact part (7) of the switching apparatus. <IMAGE>

Description

The invention relates to a triggering device for electrical switching devices by means of an ignitable explosive charge which triggers the switching device.

In a known tripping device of the type mentioned above (DE-AS 12 02 890), a resistor is switched into the circuit to be interrupted, which resistor is dimensioned such that it melts in the event of an overcurrent and thereby initiates an arc, the voltage of which drives a high current through a fuse . With such a device, trip times of 100 to 120 microseconds can be achieved according to the document. However, the detonating explosive charges are dangerous to the environment and cannot be exactly reproduced. With conventional explosive charges, short, high pressure peaks occur (explosive conversion, short reaction time), which lead to the deformation of the drive piston and therefore prevent it from being actuated several times.

No. 4,617,436 also discloses a triggering device for electrical switching devices by means of an ignitable explosive charge which triggers the switching device. The explosive charge is formed by a pyrotechnic gas generator, which can be used as an energy store for switching a switching device on and off. The energy is transferred to the switchgear via a cylinder that can be moved in two directions through the explosive charge. The document deals with the reloading devices for the gas cartridges for both the switch-on and the switch-off process. However, information about the operative connection of the cylinder with the movable contact with a view to triggering as quickly as possible is not given.

The invention is intended to improve a triggering device of the type mentioned above in such a way that with controlled explosive charge and thus increased safety, similarly short triggering times can be achieved with little technical effort. This is achieved in a simple manner in that the explosive charge is formed by a pyrotechnic gas generator which acts on a pressure piston unit which is directly coupled to the movable contact part of the switching device. Such a device is generally ignited depending on the current. However, it is also possible under certain circumstances, for example for safety reasons in power plants, to quickly protect against high vibrations, such as earthquakes.

The gas generator uses pyrotechnic substances with longer reaction times than with conventional explosive charges ( ^{t (pyrotechn.)} / T (explosive charge) 10: 1), so that considerably lower pressure peaks occur with a comparable pressure-time area and thus deformations on the pressure piston or on the switch mechanism can be avoided. As a result, the pressure pistons can be used several times.

In order to allow the tripping device to act only at extremely high short-circuit currents and to leave the rest of the usual disconnection to the commercially available switching devices, it is advantageous if the movable contact part is part of a commercially available circuit breaker. In the prior art, the resistance and also the igniter must be replaced by the specialist personnel after each triggering. In order not to impair the operability of the switch, it is advantageous if the gas generator or the gas generator is stored in a magazine with pressure pistons. It is advantageous here if an automatic ejection and an automatic refill is provided for the magazine after the release. In order not to let the impact forces occurring during the explosive erosion become so great that when they are exceeded the material strength of the piston or the piston housing is no longer sufficient, it is advantageous if the gas generator and / or the pressure piston are designed in such a way that after shock-like Reaching a predetermined force on the pressure piston results in a predetermined reduction in force. For this purpose, it is advantageous if the pressure piston opens pressure relief openings in the pressure cylinder depending on the path. Another simple type of pressure limitation has been found when pressure limitation pockets are provided in the pressure cylinder. In order to be able to better determine the pressure development of the propellant charge after it has ignited, it is advantageous if the propellant charge of the gas generator is designed as a compact of different grain size. in the special case the pressing body can consist of two partial bodies. To long-term storage under To enable very high ambient temperatures, it is advantageous if the wall of the printing cylinder is made semi-permeable with very fine pores in whole or in parts. In order to avoid endangering the function of the triggering device due to moisture damage, it is advantageous if the outer wall parts are impermeable to moisture. For this purpose, it has also proven to be advantageous if the pressure piston outer and pressure cylinder inner walls are made of corrosion-resistant material, such as a ceramic layer. Several types of ignition have proven to be advantageous for the rapid ignition of the propellant charge. With a cylindrical arrangement of the propellant charge, the jet initiation ignition is particularly suitable for ignition from the cylinder axis. It has proven to be advantageous if the jet initiator consists of a cylindrical, thin-walled sleeve, is embedded in the primer and the end opposite the primer is closed with a thin sheet metal foil designed as a space membrane. If the end of the sleeve having the sheet metal foil is designed as a flow nozzle, the hot vapors resulting from the implementation of the igniter pill can flow onto the propellant charge in a directional high-speed flow. Providing a line-shaped lighter in the propellant charge with quick and even ignition results in an inexpensive design. The line-shaped igniter can consist of a resistance wire with an applied thin layer of high-temperature-resistant safety explosive. An end face initiation, for example by means of a meandering metallic resistance layer, has proven to be advantageous if the propellant charge is arranged flat and a quick and simultaneous ignition is to take place via the flat side. A lateral surface initiation is advantageous for longer cylindrical propellant charges, with rapid ignition of the propellant charge being ensured by simultaneous ignition from the lateral surface. If the end face ignition is provided, become axially parallel in the longitudinal direction If cavities are provided, there is the advantage that the propellant charge reacts quickly by reacting further from the cavities. If the propellant charge is provided with annular circumferential grooves that are open to the ignition side when the lateral surface ignition is provided, the burn-up is improved with regard to volume detection and speed.

Exemplary embodiments according to the invention are described with the aid of the drawing.

FIG 1

den prinzipiellen Aufbau der erfindungsgemäßen Auslösevorrichtung,

FIG 2

eine konstruktive Ausführungsmöglichkeit für den schnellen pyrotechnischen Schalter,

FIG 3

eine Diagrammdarstellung der Charakteristiken des Kraftzeitverlaufs am Kolben,

FIG 4

eine Schnittdarstellung für eine mögliche Ausbildung der Druckkolbeneinheit,

FIG 5

eine Ausführungsart der Druckkolbeneinheit zur Spitzendruckbegrenzung bei schnellem Abbrand der Treibladung mit Taschen als Platzmembran,

FIG 6

eine Ausbildungsmöglichkeit des Druckzylinders zur Erreichung einer Langzeittemperaturstabilität,

FIG 7

ein Diagramm über den Druckverlauf im Kolbenraum bei Verwendung unterschiedlicher Pulverkorngrößen für die Treibladung,

FIG 8

eine Ausführungsform mit einem Jet-Initiierungszünder

FIG 9

eine Ausführungsform mit Linienzünder

FIG 10

eine Stirnflächen- und

FIG 11

eine Mantelflächenzündung für die Treibladung.

FIG 12

zeigt eine Ausführungsform der Treibladung für Stirnflächenzündung mit durchlaufenden Hohlräumen.

Show it:

FIG. 1

the basic structure of the triggering device according to the invention,

FIG 2

a design option for the fast pyrotechnic switch,

FIG 3

2 shows a diagram of the characteristics of the force-time curve on the piston,

FIG 4

2 shows a sectional illustration for a possible design of the pressure piston unit,

FIG 5

an embodiment of the pressure piston unit for peak pressure limitation in the case of rapid combustion of the propellant charge with pockets as a space membrane,

FIG 6

a possibility of training the pressure cylinder to achieve long-term temperature stability,

FIG 7

a diagram of the pressure curve in the piston chamber when using different powder grain sizes for the propellant charge,

FIG 8

an embodiment with a jet initiator

FIG. 9

an embodiment with line igniter

FIG 10

an end face and

FIG 11

a surface ignition for the propellant charge.

FIG 12

shows an embodiment of the propellant charge for face ignition with continuous cavities.

In the basic circuit shown in FIG. 1, the network with terminals 1, 2 is above switch 3, in the present case In the case of a circuit breaker, and via a current and voltage detection 4 on the consumer, in the present case a branch with a motor 5. The detection device 4 can consist, for example, of a current and voltage converter for each phase. The network states occurring here are evaluated with regard to steepness, frequencies, power and duration and, depending on the rapid rise and the short-circuit current to be expected, a pulse is given to a pyrotechnic drive 6. The pyrotechnic drive is activated by an electronically operated ignition device. The external voltage-dependent ignition method using a fuse element according to DE-AS 12 02 890 is subject to its scatter in the I ² t melting value and requires a specific short-circuit current time interval for tripping. The adaptation of a very quickly reacting fuse element to operating current conditions seems difficult, moreover the fuse element has to be replaced after each switch-off, whereby the contact must be very low-resistance (1 m). In contrast to conventional explosive charges, the pyrotechnic drive 6 consists of a gas generator which acts on a pressure piston unit coupled to the movable contact part of the switching device. The switch shown in FIG 2 consists of the movable contact part 7, which rests on the counter-contact part 9 by means of spring force 8. The contact pads have the reference numerals 10, 11. The supply lines are designated 12, 13. An arc extinguishing device 14 extinguishes the arc that occurs when the switch is opened. In the normal case of a short circuit, magnetic forces of the magnetic field built up between the movable and counter-contact part overcome the contact force applied by the spring 8 and thus open the switch. The other tripping devices of this switch are not shown in the drawing. In the event of a critical short circuit, a pressure piston unit 15 with an adjustable operating point is actuated by the detection device 4 via the initial ignition and the propellant charge. The pressure piston 16 presses with high force on the movable contact part 7 and opens the contact with high Acceleration. The force is applied by the combustion of a pyrotechnic propellant charge contained in the pyrotechnic gas generator 17. The propellant charge is ignited by an igniter, which is also part of the gas generator 17. The propellant charge must be burned off in such a way that a high burn rate is achieved in the shortest possible time. On the other hand, the erosion must not start explosively, since the associated impact forces could lead to the material strength of the piston or piston housing being exceeded. The most favorable time profile of the force acting on the piston to be realized by the time profile of the erosion is shown as an example in FIG. 3 for a commercially available circuit breaker with short-circuit release. This force-time curve changes only slightly at operating temperatures in the switch housing 18 approx. 10 ° C to approx. 150 ° C. This is achieved by a suitable composition of the propellant charge of the pyrotechnic gas generator. According to the invention, material-related and structural dimensions for the pyrotechnic element are proposed for implementation, which are described in detail in the following section.

The design of the pyrotechnic gas generator 17 as a cartridge propellant charge allows the pressure piston unit 15 and the gas generator 17 to be separated. The gas generator is introduced as a charge cartridge into the pressure piston unit via an automatic charging system with an ignition device 19 and positioned on the piston. This is done by a locking piece with a lock 20. After actuation of the pyrotechnic element, the burned-out cartridge is removed in a known manner via a pull-out claw, which is not shown, and a new one is supplied from the magazine 21. At the same time, the piston is moved back to its starting position by a return spring, not shown. An electrical center contact 22 represents the connection to the initial ignition.

3 shows the pyrotechnic force on the left and the time on the right. Line 23 is shown as a sudden onset of force. With line 24, the force required exceeds the permissible maximum force. Both force profiles lead to possible damage to the switching element. Line 25 shows the force course to be aimed for, which can be achieved with the following means. The line for the maximum permissible force is labeled 25a. The pressure piston unit shown in FIG. 4 represents the pressure piston 16 in the rest position. A guide aid 26 with a seat for the pyrotechnic element, gas generator 17, and the holder for the pressure piston unit, the pressure cylinder 27, and a fine thread 28 for setting the working point Limiting the peak pressure and for reducing the pressure after the acceleration phase of the pressure piston 16 has ended, bores 29 are provided in the pressure cylinder 27 and the guide sleeve 26. These are released after approx. 60 to 80% of the piston stroke, so that the gaseous reaction products under high pressure can escape from the pressure cylinder space. In the embodiment according to FIG. 5, pressure limiting pockets 32 are provided on the inner wall 30 of the pressure cylinder space 31, which may be designed as buckling or space diaphragms and, if the internal pressure setpoint is exceeded during combustion, e.g. can increase the gas space at a high ambient temperature as a result of an increased burn rate. This is done in two stages.

1st stage:

First, the membrane bulges out at pressure values that are only slightly above the target range. The additional volume released thereby slows down the increase in the burn-up rate.

2nd stage:

If this is not sufficient to limit the pressure, then if the pressure rises further, the membrane flakes off along a predetermined breaking point attached to the circumference.

The pressure limitation is approximately 2 kbar. With long-term storage under a very high ambient temperature, a slight decomposition of the propellant charge is possible. This releases reaction gases which can slowly increase the pressure inside the charge cartridge and in turn accelerate the decomposition process. As a result, this feedback influence could lead to the uncontrolled implementation of the propellant charge. In order to avoid this, the wall of the piston chamber is designed to be semi-permeable, in whole or in part, with fine pores, see FIG. 6, in such a way that the decomposition gases can gradually escape through the pores and the internal pressure remains limited to non-critical values, and at the same time moisture from outside to inside cannot penetrate (condensation in the micro-cavities of the pores). The wall of the printing cylinder 27 is divided into two parts here. One part represents a porous wall 33 and the other a moisture-impermeable part 34. Both during combustion and during slow decomposition, the propellant powders in question generate nitrous gases (NO, NO ₂ , NO _x ), which have a corrosive effect in a moist atmosphere. Therefore, the combustion chamber side surfaces of the piston and combustion chamber wall should be made of corrosion-resistant material. For example, a ceramic layer or sputtered corrosion-resistant metal oxide layers can be used.

The following powder mixtures have proven particularly suitable for long-term storage stability under ambient temperatures up to 150 °:

B / KNO ₃ , TiH _x / Ba (NO ₃ ) ₂ and Zr / Ba (NO ₃ ) ₂ .

The latter two powders have the lowest decomposition rates.

The powders mentioned are not very reactive (hence the high temperature stability). If necessary, the burning rate can be increased even further with additives.

Quantities in the range of high-energy explosives such as octogen are suitable for this.

The propellant charge mixture from the above-mentioned powders, optionally with additives, is in the form of granules. These granules consist of a mixture of two grain sizes with a focus on the size distribution around the values approx. 10 to 30 µm. The advantage of this double distribution is that due to the ignition process, the particle fraction with the smaller grain size burns off very quickly, thus ensuring a very rapid increase in pressure in the piston chamber. The powder fraction with the larger grain size burns more slowly and in this way ensures that the pressure in the piston chamber is maintained during the piston ejection in the decisive acceleration phase (piston stroke) up to approx. 60% of the end stroke that determines the short-circuit interruption. The combustion process is shown schematically in FIG. 7. The mass fraction of the smaller powder grains determines the steepness of the pressure increase in the piston chamber, i.e. the time until the pressure maximum is reached. The diagram in FIG. 7 shows the pressure in the piston chamber on the left and the piston stroke on the right. The pressure curve in the piston chamber, determined by the double distribution of the powder grain sizes, is represented by line 35, the smaller powder grain size fraction KGV1 and the larger powder grain size fraction KGV2 being designated. The pressure reduction across the relief openings is shown in dashed lines.

• a) als homogene Pulver-Mischung (siehe FIG 8),
• b) als Pulver der kleineren Körner plus poröser Preßkörper der größeren Körner (siehe FIG 9),
• c) insgesamt als poröser Preßkörper.

The two grain size fractions can be in the following form:

• a) as a homogeneous powder mixture (see FIG. 8),
• b) as powder of the smaller grains plus porous compact of the larger grains (see FIG. 9),
• c) overall as a porous compact.

The compact is of low mechanical strength, such that it disintegrates into its fine constituents (powder grains, grain clusters) even at low pressure in the piston chamber (= early phase of combustion).

The pressed propellant powder body can advantageously be equipped with open cavities that face the ignition side.

Forms of such bodies are shown in FIGS. 11 and 12. They show annular grooves 36 or cylindrical cavities 37 parallel to the axis, which influence the burn-off in a suitable manner after volume detection and speed. They are intended for surface or front surface ignition.

Another form of the propellant charge body, which has a favorable effect on the burn-up, is a large-pored or cavity-filled compact, the pore size or cavity diameter of which gradually decreases from the point of ignition.

For the type and embedding of the igniter, reference is made to FIGS. 8-11. The ignition process must achieve a high burn rate in a short time without initiation. This can be achieved through various measures:

Jet initiation igniter (see FIG 8)
An electrical ignition pulse of high power ignites a high-temperature-resistant igniter pill, which is embedded in a cylindrical thin-walled sleeve 38. The squib 39 is located at the upper end of the sleeve 38. The sleeve is closed at the lower end 40 with a thin sheet metal foil, which can be designed as a space membrane. Furthermore, the lower part 40 of the sleeve 38 can be designed as a flow nozzle, so that they result from the implementation of the igniter pill, in a directed high-speed flow onto the propellant charge stream. The whirling up of the powder by the hot swaths or the penetration of the hot swath flow into the cavities of the propellant charge body favors the rapid onset of a high burn rate.

Line-shaped lighters (see FIG. 9)
With this type of ignition, a linear reactive element 41, for example resistance wire with an applied thin layer of high-temperature-resistant safety explosive, is embedded in the propellant charge.

The thickness of the explosive layer is far below the limit thickness for detonative implementation (see NONEL).

When a high power electrical pulse is applied, the resistance wire evaporates. This in turn brings about a practically spontaneous conversion of the explosive layer into hot vapors, which ignite the propellant charge at a high rate of burn-off along the cylindrical contact surface.

Face initiation
The propellant charge can be ignited over a large area on the end face by means of a metallic resistance layer 42, for example in the form of a meander, with an electrical high-power pulse (see FIG. 10). Resistance layers of this type can be applied to a ceramic carrier body, for example, by sputtering technology. This is in close mechanical contact with a flat ignition charge of low layer thickness, which can consist of the same material as the propellant charge.

Shell surface initiation
The cylindrical propellant charge can also be ignited via the cylindrical surface 42. In principle, this can be done in the manner described for the end face initiation. A modified ignition is designed as follows: the transfer set 43, which is applied to the inner wall of the propellant charge cartridge, for example as a thin layer of explosive, is ignited electrically by a resistance wire - FIG. 11 - which surrounds the transfer set in a ring, or a resistance layer, see FIG. 10. The resistance wire can, as shown in FIG. circulate the thin cylindrical transfer layer 43 in a single or (not shown) multiple helical manner.

Claims (21)

1. Tripping device for electrical switchgear (3) by means of an ignitable explosive charge (17) which causes the switchgear to trip, characterized in that the explosive charge is formed by a pyrotechnical gas generator (17) which acts on a pressure piston unit (15) which is directly coupled to the moving contact part (7) of the switchgear (3).
2. Tripping device according to claim 1, characterized in that the moving contact part (7) is part of a commercial circuit breaker (3).
3. Tripping device according to claim 1 or 2, characterized in that the gas generator (3) or the gas generator (3) is magazined by the pressure piston (16).
4. Tripping device according to claim 3, characterized in that an automatic ejection and an automatic refilling with respect to the magazining is provided after the tripping.
5. Tripping device according to one of the preceding claims, characterized in that the gas generator (3) and/or the pressure piston (16) are constructed in such a way that after the abrupt reaching of a specified force on the pressure piston (16) a specified reduction of the force takes place.
6. Tripping device according to claim 5, characterized in that the pressure piston (16) opens pressure relief openings (29) in the pressure cylinder (27) in a path-dependent manner.
7. Tripping device according to claim 5, characterized in that pressure control pockets (32) are provided in the pressure cylinder (27).
8. Tripping device according to claim 5, characterized in that the propellant of the gas generator (17) is constructed as a pressing body of varying granulation.
9. Tripping device according to claim 8, characterized in that the pore size decreases gradually from the ignition site.
10. Tripping device according to one of the preceding claims, characterized in that the wall (31) of the pressure cylinder (27) is designed entirely or in partial areas to have very fine pores and to be semipermeable.
11. Tripping device according to claim 10, characterized in that the outer wall parts are impermeable to moisture.
12. Tripping device according to claim 11, characterized in that the outer wall of the pressure piston and the inner wall of the pressure cylinder consist of corrosion-resisting material, such as a ceramic layer.
13. Tripping device according to one of the preceding claims, characterized in that a jet initiation igniter is provided to ignite the propellant.
14. Tripping device according to claim 13, characterized in that the jet initiation igniter consists of a cylindrical, thin-walled sleeve (38), in which the ignition pellet (39) is embedded and which at the end opposite the ignition pellet (39) is closed with thin tinfoil formed as a rupture diaphragm.
15. Tripping device according to claim 14, characterized in that the end of the sleeve (38) with the tinfoil is constructed as a flow nozzle (40).
16. Tripping device according to one of the preceding claims, apart from claims 13 - 15, characterized in that a linear igniter (41) is embedded in the propellant (17).
17. Tripping device according to claim 16, characterized in that the linear igniter (41) consists of a resistance wire with an applied thin layer of permitted explosive with high-temperature stability.
18. Tripping device according to one of the preceding claims, apart from claims 13 - 17, characterized in that an end-face initiation is provided by way of a metallic resistance layer (42) designed to have a meandering shape.
19. Tripping device according to one of the preceding claims, apart from claims 13 - 18, characterized in that a surface-area initiation is provided.
20. Tripping device according to claim 5, characterized in that with the provision of end-face ignition the propellant is provided with parallel cavities (37) extending in the longitudinal direction and open to the ignition side.
21. Tripping device according to claim 5, characterized in that with the provision of surface-area ignition the propellant is provided with grooves (36) which are open to the ignition side and circulate in an annular manner.

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