AT406208B - Residual current device (fault-current protective circuit breaker, earth leakage circuit breaker) with overvoltage tripping - Google Patents

Abstract

Four-pole or two-pole residual current device comprising a housing having connecting terminals 1 for external and neutral conductors of a three-phase system, a contact apparatus 2 having an associated latching mechanism and an operating member 3, a residual current release 4 which operates the latching mechanism, a core-balance transformer 6, a circuit arrangement 5 for detecting the fault current signal coming from the core-balance transformer 6, comprising a circuit arrangement 8 which is connected to at least one outer conductor on the network side and to the neutral conductor on the load side and, when mains-frequency overvoltages occur between two outer conductors and the neutral conductor when there is a single-pole short in a three-phase system, said circuit arrangement 8 carries a current which energizes the core-balance transformer 6 sufficiently to trip the latching mechanism 3. <IMAGE>

Description

AT 406 208 B

The invention relates to a residual current circuit breaker (hereinafter referred to as Fl switch) comprising a housing with connecting terminals for power lines, a contact apparatus with associated switch lock and actuating member, a residual current release actuating the switch lock, a total current transformer and a circuit arrangement for detecting the residual current signal coming from the total current transformer.

Such Fl switches, which belong to the well-known prior art, only respond to fault currents flowing to earth. If such fault currents flow, the system is in an impermissible operating state, for example there is a live line in contact with an earthed device part, a person touches live parts or the like. In all such cases there is a danger to the system user, so that a quick shutdown must be made, for which the previously known Fl switches are suitable.

In addition to the insulation faults in the system, short circuits can also occur in the distribution network. As a result of such errors, which are dealt with in more detail below, there are usually line-frequency overvoltages. Such overvoltages endanger not only the functionality of the Fl switch itself, but above all the electrical equipment in the affected system.

Network faults occur only rarely in modern electrical distribution networks because more and more cables are being laid and overhead lines are now used as bundle conductors.On the other hand, many consumer devices with electronic components (e.g. television sets) have become very sensitive to overvoltages.

It is expressly pointed out that such overvoltages are neither switching overvoltages nor atmospheric overvoltages, the duration of which is in the micro- and millisecond range, but rather mains-frequency, stationary overvoltages that can be present for minutes, even hours. Such overvoltages are most often caused by short circuits between an outer conductor and the neutral conductor or PEN conductor in the distribution network, e.g. by tearing conductor ropes during storms and hoarfrost, in which case it often takes hours to repair the damage.

Figures 1 and 2 show the voltage ratios in such a case, as they arise in a three-phase network in the event of a short circuit L1-N due to zero point shifts. The amount of the voltage shift depends on the ratio of the impedances of the outer conductor to the neutral conductor (the following considerations apply mutatis mutandis to the PEN conductor). Part of the short-circuit current flows back into the network via the operational earthing via the near-transformer operational earthing, so the impedance of the neutral conductor current path will generally be lower than that of the outer conductor due to the parallel current path via the operating earthing.

If one takes these impedances as a simple example, then in a three-phase network 3N - 400/230 V, the voltage drop of the outer conductor and neutral conductor is 115 V each, and in the voltage triangle the voltages of the two outer conductors not affected by the short circuit result against the neutral conductor by means of a simple calculation with around 300 V, which can also be measured in the field. In the vicinity of the short-circuit point in the distribution network, these overvoltages occur in the consumer systems in all assigned single-phase circuits (e.g. in the sockets) and this leads to destruction after a short time if the equipment is just switched on (e.g. incandescent lamps, TV sets). Fl switches, whose function depends on the mains voltage, for example if they use mains voltage-dependent amplifier circuits for evaluating the fault current signal, can also be damaged if the voltage supply happens to be from an outer conductor that is not affected by the short circuit.

To protect a system from the described effects of such overvoltages, it must be switched off. This could be done by separate switching elements that respond to overvoltages, but these have the disadvantages of the additional space requirement in the distributor, the increased assembly effort and the higher overall price of the system.

It is an object of the invention to prevent such additional opening and to change an earth leakage circuit breaker of the type explained in the introduction in such a way that it can take over the function of a switch-off device when mains-frequency overvoltages occur. 2nd

AT 406 208 B

According to the invention, this is achieved in that a residual current circuit breaker is equipped with an additional circuit arrangement connected after the contact apparatus with at least one line-side outer conductor and after the summation current transformer with a consumer-side neutral conductor, which in the event of line-frequency overvoltages of two line conductors against the neutral conductor in the case of a single-pole short circuit in a three-phase system carries a current that causes sufficient excitation of the summation current transformer to trigger the switch lock

A Fl switch that has been expanded in this way in its function has no external differences from a conventional Fl switch, and is therefore just as easy to assemble and wire. In particular, for Fl switches with high tripping reliability according to the Austrian patent applications A 80/91, A 232/91 and A 1090/91, this addition leads to a protective device that meets all the requirements to be made, i.e. reliability of switching off, security against false tripping in the event of thunderstorm surges , Protection against overloads and disturbances in the distribution network.

According to a first variant of the invention, in the case of four-pole embodiments of a residual current circuit breaker according to the invention, it can be provided that the circuit arrangement which detects mains overvoltages is formed from three identical impedances which are interconnected at a star point, on the one hand the impedances to the breaker contacts in the Fl switch to the three outer conductors are connected and on the other hand the star point is connected to the neutral conductor after the summation current transformer.

In the normal operating state, the currents of these impedances add up to zero; in the event of a short circuit of an outer conductor to the neutral conductor, the current becomes an impedance to zero, while the currents of the two, which are somewhat increased due to the overvoltage, connect to the remaining outer conductors which are driving the mains overvoltage add geometrically, whereby the summation current transformer is excited with the impedance current. Through the simultaneous monitoring of all three outer conductors, an overvoltage is detected in any case, regardless of which outer conductor exactly occurs.

The detection of overvoltages is even easier with a two-pole F1 switch. There are various solutions, such as a series connection bypassing the summation current transformer between an outer conductor and the neutral conductor, which a voltage-dependent component, e.g. a varistor and an electromechanical release, which acts on the key switch in addition to the residual current release. According to another variant, the test circuit can be supplemented with series connections of voltage-dependent resistors which bridge the interrupter contact of the test device, whereby tripping occurs in the event of overvoltages. Of these many possibilities, only a technically and economically advantageous circuit should be protected according to the invention.

Such a circuit arrangement, which detects mains voltages, for a two-pole F1 switch can, according to the invention, consist of at least one voltage-dependent component, e.g. Varistor, be formed, the first connection of which is connected to the outer conductor after the break contact and the second connection of which is bypassed by the summation current transformer on the consumer side to the neutral conductor.

The symmetry of the mains voltages in the normal operating state cannot be exploited here, but the voltage-dependent components that can be replaced according to the invention represent a particularly simple replacement.

According to a second variant of the invention, in the case of four-pole or two-pole F1 switches in which the circuit arrangement provided for detecting the fault current signal coming from the summation current transformer has an energy storage circuit, it can be provided that the terminal point of the impedances or the second connection of the voltage-dependent component is above a voltage divider is connected to the neutral conductor and that the voltage divider is preferably connected to the energy storage circuit by means of a rectifier circuit, so that it can be charged from the circuit arrangement up to response in the event of overvoltages, as a result of which the Fl switch is switched off.

In a further embodiment of the invention, it can be provided that the three impedances are formed from three identical capacitors, as a result of which energy losses are avoided.

In a modification, the three impedances can, according to the invention, be formed from three identical, voltage-dependent resistors (varistors), which increases the effect of the voltage increase in the event of a short circuit. 3rd

AT 406 208 B

Another feature of the invention can be that a protective choke is installed in the connecting line neutral point-neutral conductor or second connection of the voltage-dependent component-neutral conductor.

In this way, currents which are too high can be avoided if there are errors in the impedances. This solution has the further advantage that it can also provide rough protection against transient overvoltages, such as those caused by atmospheric discharges, i.e. thunderstorms.

In a further development of the invention it can also be provided that the connecting line neutral point neutral conductor or second connection of the voltage-dependent component - neutral conductor is led through the summation current transformer with at least one turn, that is to say has its own winding in the summation current transformer

This allows the error signal to be amplified further when overvoltages occur.

If an energy storage circuit is used for the actuation of the residual current release, such as e.g. for the usual triggering by fault currents that result from insulation faults in the systems, e.g. in the applications AT 80/91, AT 232/91 and AT 1090/91 for a Fi switch with high tripping reliability, then even smaller fault currents are required for charging the energy storage unit and the impedances for the star point for overvoltage release can be dimensioned particularly small.

The invention will now be explained in more detail with reference to the particularly preferred exemplary embodiments shown in the drawing figures.

Fig. 1 shows a distribution network 3N - 400/230 V, in which there is a short circuit between an outer conductor LI and the neutral conductor N with the associated voltages of the outer conductor against the neutral conductor and against the reference earth;

Fig. 2 shows in the voltage triangle the voltage shifts of the outer conductor and the neutral conductor;

Fig. 3 shows the circuit arrangement for a four-pole F1 switch

Mains overvoltages consisting of three star-connected impedances made of ohmic, inductive or preferably capacitive resistors;

Fig. 4 shows the circuit arrangement for a four-pole F1 switch

Mains overvoltages consisting of three capacitors connected in a star and a protective choke for current limitation;

Fig. 5 shows the circuit arrangement for a four-pole F1 switch

Mains overvoltages consisting of three varistors and an additional winding in the total current transformer;

6 shows the circuit arrangement for mains overvoltages consisting of three varistors and a voltage divider circuit for the division of the energy storage circuit in the event of overvoltages and for a four-pole F1 switch with an energy storage circuit

Fig. 7 shows the circuit arrangement for a two-pole F1 switch

Mains overvoltages, which consists of a simple parallel circuit with a varistor, which is connected bypassing the summation current transformer after the break contact of the outer conductor and the neutral conductor.

The voltage relationships shown in FIGS. 1 and 2 in a three-phase distribution network 3N - 400/230 V with a short circuit L1-N have already been discussed above and are not to be described again here. They only represent the theoretical background for the invention, but do not reveal the possible embodiments.

The basic idea of the invention is to be explained on the basis of FIG. 3 and relates to four-pole and two-pole F1 switches which are dependent on the mains voltage, conditionally dependent on the mains voltage or independent of the mains voltage and comprise a housing with connecting terminals 1 for connecting the lines L1, L2, L3 and N on the mains and consumer side, a contact apparatus 2 with associated switch lock and actuating member 3, a test circuit with test button and test resistor 7, a fault current release 4 actuating the switch lock 3, a summation current transformer 6, a circuit arrangement 5 for evaluating the fault current signal coming from the summation current transformer.

An additional circuit arrangement 8, which triggers the switching mechanism 3 in the event of line-frequency overvoltages of two external conductors L1, L2, L3 against the neutral conductor N in the event of a single-pole short circuit in a three-phase system,

AT 406 208 B enables four-pole Fl switches to switch off even in the event of mains-frequency overvoltages and thus protect itself and the downstream consumer system.

The response threshold at which the overvoltage detection circuit 8 triggers the switching lock 3 can in principle be set within wide limits. A value between 1.1 times and 1.2 times the nominal value of the mains voltage can be specified as the usual value for this, i.e. for U = 230 V overvoltages between approximately 260 V and 280 V, the mains voltage being between an outer conductor and the neutral conductor Assuming zero. It is clear that two-pole and four-pole Fl switches can be protected, regardless of whether their residual current is triggered depending on the mains voltage, conditionally on the mains voltage or independently of the mains voltage

The solution for conditionally voltage-dependent four-pole Fl switches with energy storage circuit is particularly advantageous because only a few small electronic components have to be used in addition and in addition to the mains-frequency overvoltage protection, coarse protection against thunderstorm overvoltages can also be achieved.

FIGS. 3 to 7 show examples of Fl switches according to the invention, FIGS. 3, 4, 5 and 6 showing four-pole designs and FIG. 7 showing a two-pole construction. Systems independent of the mains voltage are shown in FIGS. 3, 4, 5 and 7; FIG. 6 shows a conditionally mains voltage-dependent design, in which the fault current is detected by an energy storage circuit 5 which is independent of the mains voltage, and the switching lock 3 is triggered by an electromechanical or electronic converter relay, depending on the mains voltage 16 and a shunt release 4.

FIG. 3 shows an exemplary embodiment of a four-pole mains voltage-independent Fl switch with a circuit arrangement 8 for detecting mains frequency overvoltages, which consists of three ohmic, inductive or preferably capacitive impedances 9 connected in a star. The star point of this interconnection is connected after the summation current transformer 7 to the neutral conductor N, the other, not connected connections of the impedances 9 are connected to the three outer conductors L 1, L2, L3, each after the breaker contacts 2. In the normal operating state, only a small compensating current flows via the star point to the neutral conductor N. In the event of a short circuit in the network, however, the entire unbalance current flows to the neutral conductor N, which excites the residual current transformer 6 as a residual current and actuates the residual current release 4 via the circuit arrangement 5 and thus releases the switching lock 3

Figure 4 shows an embodiment in which the impedances 9 are designed as capacitors and a protective choke 10 is also installed in the connecting line, which, for example, has a current limiting effect when a capacitor breaks down. The capacities prevent heat losses in continuous operation.

A reduction in the design by a smaller tripping current can be achieved if, according to FIG. 5, the connecting point, star point-neutral conductor of the circuit arrangement 9 is passed through the summation current transformer 6 with at least one turn, that is to say equips it with an additional winding 11

FIG. 7 shows a two-pole F1 switch independent of the mains voltage with a simple, inexpensive solution for the mains-frequency overvoltage monitoring. It consists of a circuit arrangement 8, which now consists only of a voltage-dependent component (varistor) 9. It is connected to the outer conductor after the break contact 2 and to the neutral conductor N after the summation current transformer 6. If the varistor 9 becomes conductive in the event of an overvoltage, the summation current transformer 6 is excited and the FL switch switches off. Of course, this solution can also be achieved through the measures described above, e.g. an additional winding 11 can be added to the summation current transformer 6.

A further reduction in the fault current of the circuit arrangement 8 required for tripping can be achieved if the circuit arrangement 5 provided for detecting the fault current signal coming from the summation current transformer 6 has an energy storage circuit. Such an energy storage circuit is conceivable in both a four-pole and a two-pole embodiment.

FIG. 6 shows a four-pole, conditionally voltage-dependent Fl switch with such a circuit arrangement 5 with the energy storage elements rectifier circuit 12, storage capacitor 13 and voltage-dependent switching element 14.

In the case of the usual insulation faults in the protected consumer system, the residual current transformer 6 is excited by the fault current flowing to earth and the Fl switch switches to 5

Claims (8)

AT 406 208 B the response of the energy storage circuit and the resulting impulse to the converter relay 16 via the shunt release 4 by unlatching the switch lock 3. If mains-frequency overvoltages occur, the same effect can be achieved in that the star point of the impedances 9 - if there is a four-pole F1 switch - or the second connection of the voltage-dependent component 9 - if there is a two-pole F1 switch - via a voltage divider 17, 18 is connected to the neutral conductor N and this voltage divider 17, 18 is connected to the energy storage circuit 12, 13, 14 via a rectifier circuit 15. This can therefore not only be charged by the summation current transformer 6 but also by the circuit arrangement 8 and activated. Since enough time (a few tenths of a second) is available, the smallest charging currents are sufficient for the release. Claims: 1. Residual current circuit breaker (hereinafter referred to simply as Fl switch) comprising a housing with terminals (1) for the outer and neutral conductors of a three-phase system, a contact apparatus (2) with associated switch lock and actuator (3), one the switch lock Actuating fault current release (4), a summation current transformer (6), a circuit arrangement (5) for detecting the fault current signal coming from the summation current transformer (6), characterized by one after the contact apparatus (2) with at least one line-side outer conductor (L1, L2, L3) and after the summation current transformer (6) with a consumer-side neutral conductor (N) connected circuit arrangement (8), which leads to a current in the event of line-frequency overvoltages from two external conductors against the neutral conductor in a single-pole short circuit in a three-phase system, which triggers the switch lock (3 ) sufficient excitation of the total current transformer (6) causes. 2. Four-pole F1 switch according to claim 1, characterized in that the circuit overvoltage-detecting circuit arrangement (8) is formed from three identical impedances (9) which are interconnected to a star point, the impedances (9) on the one hand after the interrupter contacts (2 ) are connected in the Fl switch to the three outer conductors (L 1, L2 and L3) and on the other hand the star point after the summation current transformer (6) is connected to the neutral conductor (N) (Fig. 3). 3. Two-pole Fl switch according to claim 1, characterized in that the circuit arrangement (8) from at least one voltage-dependent component, e.g. Varistor (9) is formed, the first connection of which is connected to the outer conductor (L1) after the interrupter contact (2) and the second connection of which is bypassing the summation current transformer (6) on the consumer side to the neutral conductor (N) (Fig. 7 ). 4. Four- or two-pole F1 switch according to claim 2 or 3, wherein the circuit arrangement (5) provided for detecting the residual current signal coming from the sum current transformer (6) has an energy storage circuit (12, 13, 14), characterized in that the The terminal point of the impedances (9) or the second connection of the voltage-dependent component (9) is connected to the neutral conductor (N) via a voltage divider (17, 18) and that the voltage divider (17, 18) is preferably connected via a rectifier circuit (15) the energy storage circuit (12, 13, 14) is connected, so that it can be charged from the circuit arrangement (8) until it is activated in the event of overvoltages, as a result of which the Fl switch is switched off (FIG. 6). 5. Four-pole Fl switch according to claim 2 or 4, characterized in that the three impedances (9) are formed from three identical capacitors (Fig. 4). 6. Four-pole Fl switch according to claim 2 or 4, characterized in that the three impedances (9) are formed from three equal, voltage-dependent resistors (varistors) (Fig. 5). 7. Four-pole or two-pole Fl switch according to claims 1 to 6, characterized in that in the connecting line stem point - neutral conductor (N) or 6 AT 406 208 B second connection of the voltage-dependent component · neutral conductor (N) a protective choke (10) is installed (Fig. 4). 8. Four-pole or two-pole Fl switch according to claims 1 to 6, characterized in that the connecting line stem point neutral conductor (N) or second connection of the voltage-dependent component neutral conductor (N) with at least one turn through the summation current transformer (6) is, so has its own winding (11) in the total current transformer (Fig. 5). Including 7 sheets of drawings 7