EP0548390A1 - 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 above-mentioned type (DE-AS 1 202 890), 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 an igniter . 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.

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 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 ensure rapid protection 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 are stored in magazines 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 define 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 consist 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 here if the jet initiation igniter consists of a cylindrical, thin-walled sleeve, is embedded in the primer and the end opposite the primer is sealed 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 igniter 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 rapid and simultaneous ignition is to take place via the flat side. A lateral surface initiation is advantageous for longer cylindrical propellant charges, with a rapid reaction 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 Provided cavities, there is the advantage of a rapid reaction of the propellant charge in that the propellant charge continues to react from the cavities. If the propellant charge is provided with annular grooves that are open to the ignition side and the circumferential 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 conditions occurring here are evaluated with regard to steepness, frequencies, power and duration and depending on the rapid rise and the expected short-circuit current, a pulse is given to a pyrotechnic drive 6. The pyrotechnic drive is activated by an electronically operated ignition device. The ignition voltage-dependent ignition method using a fuse element according to DE-AS 12 02 890 is subject to its scatter in the I²t 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 appears 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 great 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 must be burned off in such a way that a high burn-up 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 returned 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 required force 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 Limitation of 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 can be designed as buckling or space diaphragms and, if the target range of the internal pressure 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 slowly increase the pressure inside the charge cartridge and can 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 very fine pores, see FIG. 6, such 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 impression 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, nitrous gases (NO, NO 2, NO _x ) are formed in the propellant powders in question, which have a corrosive effect in a moist atmosphere. For this reason, the partial surfaces of the piston and the combustion chamber wall on the combustion chamber side should consist 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 / KNO₃, TiH _x / Ba (NO₃) ₂ and Zr / Ba (NO₃) 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 the ignition process causes the particle fraction with the smaller grain size to burn 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 pressed body 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 the erosion).

The compressed propellant powder body can advantageously be equipped with open cavities which 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-up in a suitable manner after volume detection and speed. They are intended for ignition of the lateral surface or front surface.

Another form of the propellant charge body, which has a favorable effect on the burn-up, is a large-pored or hollow body, the pore size or hollow 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 of a shock. 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 primer, 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 igniters (see FIG. 9)

In this type of ignition, a linear reactive element 41, e.g. Resistance wire with an applied thin layer of high-temperature-proof safety explosives, 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 results in 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 at 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). Such resistance layers can e.g. Apply to a ceramic carrier body using 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 single or (not shown) multiple helical.

Claims (21)

Tripping device for electrical switching devices by means of an ignitable explosive charge which triggers the switching device, characterized in that the explosive charge is formed by a pyrotechnic gas generator which acts on a pressure piston unit coupled to the movable contact part of the switching device. Tripping device according to claim 1, characterized in that the movable contact part is part of a commercially available circuit breaker. Tripping device according to claim 1 or 2, characterized in that the gas generator or the gas generator are magazined with pressure pistons. Release device according to claim 3, characterized in that an automatic ejection and an automatic refill is provided in the magazine after the release. Tripping device according to one of the preceding claims, characterized in that the gas generator and / or the pressure piston are designed such that a predetermined reduction in the force takes place after a predetermined force is suddenly reached on the pressure piston. Tripping device according to claim 5, characterized in that the pressure piston opens pressure relief openings in the pressure cylinder depending on the path. Tripping device according to claim 5, characterized in that pressure limiting pockets are provided in the pressure cylinder. Tripping device according to claim 5, characterized in that the propellant charge of the gas generator is designed as a compact of different grain size. Tripping device according to claim 8, characterized in that the pore size gradually decreases from the point of ignition. Tripping device according to one of the preceding claims, characterized in that the wall of the pressure cylinder is made semi-permeable in very fine pores or in partial areas. Tripping device according to claim 10, characterized in that the outer wall parts are impermeable to moisture. Release device according to claim 11, characterized in that the pressure piston outer and pressure cylinder inner walls consist of corrosion-resistant material, such as a ceramic layer. Tripping device according to one of the preceding claims, characterized in that a jet initiation igniter is provided to ignite the propellant charge. Tripping device according to claim 13, characterized in that the jet initiator consists of a cylindrical, thin-walled sleeve in which the primer is embedded and the end opposite the primer is closed with a thin sheet metal foil designed as a space membrane. Tripping device according to claim 14, characterized in that the end of the sleeve having the sheet metal foil is designed as a flow nozzle. Tripping device according to one of the preceding claims, except for claims 13-15, characterized in that a linear igniter is embedded in the propellant charge. Tripping device according to claim 16, characterized in that the linear igniter consists of a resistance wire with an applied thin layer of high-temperature-resistant safety explosive. Tripping device according to one of the preceding claims, except for claims 13-17, characterized in that an end face initiation is provided by a meandering metallic resistance layer. Tripping device according to one of the preceding claims, except for claims 13-18, characterized in that a lateral surface initiation is provided. Tripping device according to claim 5, characterized in that the propellant charge is provided with longitudinally extending, parallel cavities which are open to the ignition side when the end face ignition is provided. Tripping device according to claim 5, characterized in that the propellant charge is provided with ring-shaped circumferential grooves open to the ignition side when the jacket ignition is provided.

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