CZ325396A3 - Voltage discharge gap in fuse carrier - Google Patents

Abstract

A voltage discharge gap in a fuse carrier to protect the electrical device against surges of any origin, arranged in the fuse carrier case (10) as a mounted array of the varistor plate (1) with a fusing conductor (4) connected in series. The fusing conductor (4) is surrounded by extinguisher powder (12) inside the case (10).<IMAGE>

Description

Surge arrester in pad insert

Technical field

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relates to a surge arrester arranged in the insert to protect electrical equipment from, which may be of any origin.

Invention in fuse effects of overvoltage

BACKGROUND OF THE INVENTION

An essential part of most known surge arresters is a zinc oxide varistor plate which, for the rated voltage of the electrical equipment, exhibits a high electrical resistance to the passage of electrical current from the protected electrical equipment to ground.

If the voltage of the protected electrical device exceeds a specified voltage value, the varistor plate immediately becomes conductive and conductively connects the protected electrical device to ground, thereby protecting said electrical device from the effects of overvoltage. The voltage level is determined by the thickness of the varistor plate. In order to increase the voltage level, the varistor plates can be arranged in series. The current carrying capacity is determined by the area of the varistor plate. In order to increase the current carrying capacity of the plates, they can also be shifted in parallel.

it is possible to use these varistor

In the case of prolonged overvoltage or very high overvoltages, the varistor plate can overheat and be destroyed. The varistor plate becomes permanently conductive and a short-circuit current, limited only by the resistance of the electrical circuit, then flows from the protected electrical device to ground. The electrical circuit is overloaded and can naturally cause thermal or electrodynamic damage to the electrical equipment.

To avoid this emergency all known solutions of equipment wiring equipped with a serial state, almost surge arresters are in the electrical pre-fuse or circuit breaker. These are used in particular as protection of the electric circuit against the aforementioned short-circuit effects, which may occur as a result of the aforementioned destruction of the varistor plate, in particular after its thermal overload or even after its aging.

The main disadvantage of this series arrangement of electrical elements is further complicated electrical equipment, increased acquisition costs, more complicated remote control of the recognition of the cause of the emergency state in the electrical equipment and the like.

Another disadvantage of the known arresters in which varistor plates and short-circuit fuse elements are combined in a single body is hitherto their relatively low technical parameters, which cannot be further effectively increased in existing concepts, in particular with respect to short-circuit breaking capacities.

electrical installation equipment as well as

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a bias voltage arrester which eliminates the number of otherwise necessary elements in the protected circuit, without imposing any particular demands on its own production, and in particular to exhibit many times higher short-circuit breaking capacity without danger of housing destruction; This object is achieved by a pre-assembled set of varistor plate and a fusible conductor connected in series to the fuse-link housing, at least the fusible conductor being surrounded by an extinguishing powder in the housing.

According to the invention, in terms of cost-effectiveness in achieving the penetrating effects of arc quenching, sand is preferred.

that the extinguishing powder is siliceous

According to the invention, further penetrating effects in the arc quenching can be achieved in that the extinguishing powder is formed in the form of a solid electric arc quenching structure by liquid bonding reinforcement.

In order to suppress the destructive effects of the electric arc when switching off the short-circuit current, in particular to prevent the melting conductor from burning up to the insulating material of the varistor plate, it is very advantageous according to the invention that the melting conductor is connected to the electrode of the varistor plate.

For some modifications of the surge arrester, especially from a production point of view, it may seem very advantageous if the extinguishing backfill, strengthened to form a solid arc arc, fills the entire cavity space of the fuse-link housing. Then the operation of watering the varistor plate with the insulating material is eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and effects of the invention are apparent from the accompanying drawing, in which: Fig. 1 is a longitudinal cross-sectional view of a fuse-link housing with a pretensioner with a view of a complete pre-assembled input and output contact assembly, fusible and varistor plate underneath; external signalization of melting conductor melting and glass positioning rod of the whole system in the middle, fig. 2 longitudinal section of the fuse-link housing with pre-tensioned arrester, showing further disposition of mutual arrangement of fusible conductor and laminated varistor plate with middle outlet for supply belt and orientation Fig. 3 is a side view of the sub-assembly of the varistor plate and its electrodes, Fig. 4 is a plan view of the sub-assembly of the varistor plate and one of its outer electrodes with perforation.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of a surge arrester according to the invention is explained below for its application to the housing 10 of a known ceramic fuse-link.

An essential part of the surge arrester is a varistor plate 1, for example of zinc oxide, which, for the rated voltage of the electrical device, exhibits a high electrical resistance to the passage of electric current from the protected electrical device (not shown) to earth.

If the voltage of the protected electrical device exceeds the set voltage value, the varistor plate 1 immediately becomes conductive and conductively connects the protected electrical device to ground, thereby protecting said electrical device from the effects of overvoltage. The voltage level is determined by the thickness of the varistor plate 1. To increase the voltage level, the varistor plates 1 are arranged in series. The current rating is determined by the surface of the varistor plate 1. To increase the current rating, these varistor plates 1 can be arranged in parallel. 3 and 4 show the parallel connection of two varistor wafers 1 by means of three copper electrodes 2, 3, which are soldered to the varistor wafers 1. Technically, the varistor plates 1 and the copper electrodes 2,3 can be coupled by the pressure exerted, for example, by a spring (not shown).

Obviously, the varistor plates 1 are subjected to high stresses during operation. In order not to skip the electric discharge on the sides of the varistor plates 1, these are embedded in the insulating material 13 (Fig. 2). For lower current loads or for varistor wafers 1 with the surface treatment of their sides, it is not necessary to embed this with an insulating material 13.

In the case of prolonged overvoltage or very high overvoltages, the varistor plate 1 can overheat and be destroyed. The varistor plate 1 is then)

it becomes permanently electrically conductive and an electrical current limited by the circuit resistance, which means that a short circuit occurs, starts to flow from the protected electrical device to the wall. In order to avoid this emergency condition, a melting conductor 4 is connected to the er-11 varistor plate 1, for example in the form of a transversely perforated strip used in power fuses. One side of the fusible conductor 4 is connected to the copper electrode 3 of the varistor plate 1 via a lead-in strip 6. The other side of the fusible conductor 4 is conductively connected to the inlet external contact 11 of the entire fuse-link. The fusible conductor 4 is connected to the copper electrode 3 via a large cross-sectional feed passage 6 so as not to penetrate the potting insulating material 13 of the varistor plate 1. This prevents the fuse-link housing 10 from being destroyed.

the effect conductor leads

Thus, after irreversible destruction of the varistor plate 1, a short-circuit current begins to pass through the arrester circuit. The melter conductor 4 is surrounded by an extinguishing backing 12 within the housing 10 so that the arc arrester in the arrester is very high. This overvoltage arrester function shifts to a level similar to that of the power fuses. The interface between the sealing compound 13 and the extinguishing powder 12 is approximately in the center of the fuse-link. The fire-extinguishing powder 12, for example quartz sand, is decisively involved in extinguishing the arc because of its high ability to cool the arc intensively during the power cut-off process. By means of a final process, for example using a liquid binder and subsequently induced chemical reaction, it is possible to solidify said extinguishing powder 12 to form a relatively solid extinguishing formation surrounding 4. A reinforced extinguisher for a more intense arc and better heat dissipation from the surge arrester resulting in a substantial reduction the energy balance of the tripping process and the resulting further improvement of the monitored electrical parameters of the surge arrester. For some modifications of the surge arrester, especially from a production point of view, it may seem very advantageous if the fire-extinguishing powder reinforced into the powder 12 in its practical ability to extinguish the electrical forms of a solid arc of a quenching formation fills)

inserts. It is then not necessary, with the varistor, to completely fill the cavity cavity of the fuse housing 10 with a part of the cavity of the housing with an insert 13 encapsulated with insulating material 13.

In case of melting of the melting conductor 4 it is necessary to signal locally. or a remote surge arrester failure. For this purpose, it is externally on one of the faces 8

insurance inserts arranged signaling spring 7, between which and inlet waist 6 is stretched i resistive wire 5. He is after remelting fusible conductor 4 remelts also. The team up in advance prestressed signal spring 7 releases. T ímto Yippee vidi tělně

overvoltage arrester failure indicated. Above the signal spring it is possible to place a microswitch or other device (not shown) in the isolation signal and to carry out a remote signaling by means of it. The resistance wire 5 is also located in the extinguishing powder 12.

separate This subassembly is

The varistor plate 1, the copper electrodes 2,3, the lead-in strip 6, the melting conductor 4, the output and input contacts 11, the positioning glass rod 17 form a pre-assembled unit - subassembly.

The entire subassembly mentioned above is connected to the fronts 8 by means of screws 16 and these fronts 8 are connected to the ceramic casing 10 by means of external screws 15. To increase the tightness for technological operations and firefilling backfill and the casing 10, washers 9 are inserted.

watering with insulating material 12 - are between the fronts 8

Industrial applicability

The surge arrester in the fuse-link is preferably intended to protect electrical equipment and electrical networks from the effects of electrical overvoltages of any origin, in particular to protect destructive transformers, electrical apparatus, computers and computer networks and the like.

Claims (6)

PATENT CLAIMS Surge arrester in a fuse-link, characterized in that a pre-assembled set of varistor plate (1) and a fusible conductor (4) connected in series are arranged in the fuse-link housing (10), at least the fusible conductor (4) being in the housing (10) surrounded by an extinguishing backfill (12). Surge arrester according to claim 1, characterized in that the extinguishing powder (12) is made of quartz sand. Surge arrester according to claim 1, characterized in that the extinguishing backfill (12) is consolidated in the form of a fixed electric arc of the quenching formation. Surge arrester according to claim 1, characterized in that the fusible conductor (4) is connected to the electrode (3) of the varistor plate (1) by at least a double cross-sectional reinforced supply belt (6). Surge arrester according to claims 1 and 2, characterized in that a signal spring (7) is arranged externally at one of the faces (8) of the fuse-link housing (10), between which a biasing resistor is arranged a wire (5) surrounded by an extinguishing backfill environment (12). Overvoltage arrester according to the fact that the extinguishing backfill (12) is an electric arc of the quenching cavity of the housing (10). of claims 1 and 3, characterized in that they are reinforced to form a solid, filling the entire space