SK18498A3 - Disconnector for surge arrester - Google Patents

Abstract

The arrangement includes an arrangement (3) recording a current flowing through the over-voltage protection device (1), and a switch-off arrangement triggered by the current measuring arrangement for separating the over-voltage protection device from a line supply. The arrangement records the electric energy received by the over-voltage protection device, and operates the switch-off arrangement when reaching a pre-settable energy quantity which is smaller or equal to the maximum power dissipation of the over-voltage protection device. The switch-off arrangement includes a breaker contact (2) connected in series to the over-voltage protection device.

Description

Technical field

The present invention relates to an overvoltage protector which comprises a surge current defining a device and a disconnecting device triggered by the device to disconnect the overvoltage arresters from the mains.

BACKGROUND OF THE INVENTION

Various components are used for the surge arresters in the power supply network. The most important ones are sparks, varistors, suppressor diodes or similar devices. All have a common voltage dependence of their electrical resistance. That is, if their voltage is less than a certain threshold, they have a relatively high electrical resistance, but as soon as the voltage exceeds the threshold, the electrical resistance drops substantially.

This feature can be used to dissipate the network overvoltages that are most commonly triggered by lightning. Therefore, said components are connected in the power supply lines between the phase conductors L1, L2, L3 and the PE ground, but also between the neutral conductor N and the PE ground. The above-mentioned voltage threshold is selected in such a way that the (permanently connected) mains voltage is below the threshold, therefore the components have high resistances during normal operation and therefore only negligible small leakage currents or no currents can flow through them. .

When the overvoltage occurs, the voltage threshold is exceeded, the components pass into the off-state condition and the overvoltage energy is lifted into the PE conductor. In this way, an increase in the line voltage to the (unacceptably high) overvoltage value can thus be prevented.

According to the energetic content of the overvoltage, relatively large currents occur during the leakage and flow through the overvoltage-dissipating components and therefore heat them.

Therefore, each leakage element is exposed to a thermal stress which it can only withstand to a certain extent. This degree of resistance is given by the maximum limit of energy absorption, which depends on the design type of the component, its volume and material, etc. If this limit is exceeded, the component will be destroyed or at least damaged.

In addition to the relatively short overvoltages caused, for example, by lightning strikes, there are also long-term increases in mains voltage (TOV), which of course also bring the leakage elements to their low ohmic state.

The cause of this phenomenon is as follows:

The low-voltage network used to supply the system is supplied from the medium-voltage network by means of a transformer. Both transformer zero points - the primary and secondary side - are connected by a common ground resistance.

When a ground connection occurs in a medium voltage network, a current flow occurs, resulting in a voltage drop across the ground resistance. This, however, increases the potential of the neutral point on the secondary side and hence the potential of the neutral conductor of the low-voltage network by the aforementioned voltage drop on the grounding resistor. As a result, the potential difference between the phase conductor and the ground also increases in the low voltage grid.

The transient overvoltage amplitude of the TOV type is considerably lower than the amplitude of lightning-induced overvoltage, but it can reach several times the nominal voltage between the phase conductor and ground. The most unpleasant feature of TOV transient overvoltages in relation to the leakage elements is their relatively long exposure time. Similar surge voltages can last for several hundred milliseconds, so they can occur for several periods in a conventional 50Hz network.

However, this is associated with a long-term effect of the leakage current, which results in high thermal stress on the leakage components.

In summary, the leakage component can be destroyed or damaged by both types of lightning surges caused by lightning or TOV surges. The consequence of this is that the damaged component will not reach its full power after the overvoltage has gone, and therefore negligible currents will not flow into the PE even during normal operation. Therefore, a damaged component must be found and disconnected from the mains by means of a separation device. The defective component must then be replaced and the surge arrester must be put back into operation in order to be able to return a new overvoltage to PE.

At present, there are design solutions for the surge arrester with the function described above.

EP-A1-261 606, EP-A1-613 226 and EP-A1-576 395 describe protective circuits in which a disconnecting device is provided for each current circuit which is routed from the mains via a leakage device, downstream of the disconnecting device. with the device, these current circuits are connected to a common ground conductor. This common conductor incorporates a control device that operates on a protective principle using stray currents. For each surge protector, a delay circuit is provided in the secondary circuit of the summation current transformer to prevent the separator from responding to overvoltages caused by the currents. In this way, the electrical strength of the separator against shock currents is created.

And AT-PS-394 285 uses an Fl-protection switch to monitor a faulty leakage element.

This is possible in a simple way

The FI-protection method can be realized by connecting the leakage behind the switch. Each current leakage flows into and out of the earth

The FI protection switch thus represents the triggering fault current, therefore disconnection

Fl-protective switch is activated impermissibly by high leakage currents.

by

AT-PS-391 571 A leakage separator assumes a separating device for each device. Again, the functional principle is the same as the functional principle of the FI protective switch transformer.

is a

Using the current detected

In the secondary transformer coil of this overcurrent current, the measuring current induced overcurrent charges the capacitor, and when a certain voltage at the capacitor is reached, the opening of the contact is connected in series with the leakage component.

All of these design solutions are expected to damage or destroy the downcomer, and when the leakage high leakage currents occur as a result of the damage or downcomer, the separation of the element that raises the overvoltage or the faulty downcomer is induced.

Therefore, it is contemplated that the leakage components can be thermally destroyed by overvoltage, the magnitude of which is only slightly larger than the nominal voltage of the grid and thus is not more dangerous. This results in an obvious disadvantage of the relatively high wear of the leakage components.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an overvoltage isolation device of the aforementioned type, in which the thermal overload of the downcomer would not be expected to flow due to current flow, but in which similar overload could be prevented.

This object is achieved according to the invention in that the device detects the leakage energy received and when a predeterminable amount of energy less than or equal to the maximum possible energy absorption limit of the overvoltage protector is reached, the disconnecting device is activated.

In this way, before or when * x is reached.

the maximum permissible temperature rise, stops the energy supply and hence the heat supply, which makes it possible to prevent damage caused by damage or destruction.

According to a first embodiment of the invention, it is contemplated that a disconnecting device which is a break contact, an overvoltage, and can be operated in series by a circuit breaker lock.

The advantage of this solution is based on the fact that it offers the advantage of offering very little equipment.

costly implementation of disconnect

According to a second embodiment of the invention, it can be assumed that the disconnecting device comprises an overvoltage-connected overvoltage protection device, the series of which is preferably fused in series, operated in parallel by a fuse lock and a pusher to the overvoltage lead and contact.

Disconnect leakage. thus, it is not realized by opening the contact, overcurrent, extremely

In comparison, a device for protection preferably fuses, but is induced by a fast-acting short-circuit. arresters. With fuses, it is possible to realize in a much simpler way a larger "contact distance, possible delay or disabling" but, therefore, the disconnection is a kivivation.

A particularly preferred embodiment of the invention is based on the fact that the energy metering device consists of a series combination of a first circuit for producing a signal proportional to the current through the overvoltage, a second circuit integrating over time the signal and a recognition circuit threshold controlling the circuit breaker lock.

This design can be applied to the leakage elements which, in their low ohmic state, have approximately constant voltages at their terminals, this voltage being known. The device for measuring said voltage can be saved, which substantially simplifies the entire energy measuring device.

It may be assumed, for the purpose of developing the invention, that the signal generating circuit, which is proportional to the current through the overvoltage surge, is constituted by a current measuring transformer, preferably by a current measuring current transformer.

In this way, it is possible to generate a galvanically isolated measuring current from the leakage current with a substantially lower amplitude.

In another construction of the invention, it can be assumed that the signal generating circuit, which is proportional to the current through the surge arrester, is formed by a Hall probe.

In this way it is also possible to generate a galvanic isolated signal from the leakage current, now in the form of a voltage.

Another embodiment of the invention may be based on the fact that the signal generating circuit, which is proportional to the current through the overvoltage, is formed by an inductor.

Even with such a current detection device, as with the Hall probe, the current obtained is proportional to the voltage, and is much easier to manufacture and install than the Hall probe.

Another characteristic of the invention may be that the integration circuit comprises a rectifier circuit and a capacitor.

This embodiment makes it possible to realize functionally reliable integration in a particularly simple manner.

In this context, it can also be assumed that the integration circuit comprises a rectifier and an operational amplifier connected as an integrator.

The amplification of a similar circuit with an integrated circuit can be adjusted by appropriately selecting the values of the circuit components, so the amplitude of the output signal can be easily adapted to the following circuits.

Furthermore, it can be assumed that the threshold recognition circuit is formed by a Zener diode.

Such a component has a precisely defined, time-stable switching level, which makes it possible to maintain the time-constant switching properties of the surge arrester.

Another variant of the invention may be based on the threshold recognition circuit being an operational amplifier.

Switching level similar to easily adjusted and also voltage.

The wiring can be separately changed by selecting the reference

According to another embodiment of the invention, it can be assumed that the threshold recognition circuit is constituted by a transistor structure operating in the closing direction.

Unlike the above-mentioned circuits with operational amplifiers, a similar transistor structure does not require operating voltage, so there are no circuits to create it.

According to a particularly preferred embodiment, a filter circuit that limits the leakage current is proportional to a signal whose frequency is less than or equal to the frequency of the network, is connected to the signal invention, which is proportional to the current generating circuit.

In this way, the likelihood of faulty disconnection at short overvoltages, which should be easily removed, is minimized.

In this regard, in another embodiment of the invention, it can be assumed that the filter circuit has the characteristics of a low pass or band pass.

In this way, the effect of high-frequency leakage currents on the activation of the circuit-breaker lock is reliably suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below with reference to the accompanying drawings.

Fig. 1a shows a schematic block diagram of a first exemplary embodiment of a water surge separator according to the invention.

[0035] FIG. 1b shows a principal block diagram involvement a second exemplary embodiment of the separator

overvoltage arresters according to the invention.

[0035] FIG. 2 shows a schematic block diagram

FIG. for use in connection with varistors

with closeup by illustrating the energy of the measuring circuit. [0035] FIG. 3 shows the maximum flow as a flow / time diagram possible limit energy absorption of varistor.

Fig. Figures 4a-4c show circuit diagrams of two practical embodiments of the surge arrester device according to the invention with a circuit breaker release which is independent of the mains voltage.

Fig. 5 shows the overvoltage separation device of FIG. 4a, 4b with the opening of the circuit-breaker lock which is dependent on the mains voltage.

Fig. 6a-6c illustrate various embodiments of a circuit that determines the load on a downcomer.

DETAILED DESCRIPTION OF THE INVENTION

The basic idea of the invention is to prevent thermal overload of the downcomer that flows through it.

which is induced by the current,

For this purpose, it is envisaged to monitor the amount of energy that has been supplied to the arresters K (varistor, suppressor diode, etc.) and to decouple the line from the network at the latest when the maximum energy absorption limit of the component is reached, preferably at a slightly lower value. than this maximum possible energy absorption limit.

In FIG. 1a shows a schematic circuit diagram of an isolation device for the overvoltage leakage device that makes it possible to meet this requirement. The isolation device according to the invention comprises a device 6 which determines the current through the overvoltage arresters 6 and a disconnecting device which can be activated by the device 6 and which disconnects the device 6 from the mains. In the embodiment of FIG. 1a is formed by a break contact 6 which is connected

It is in series with a protected overvoltage protector 6 and which can be operated with the switch lock 6.

A second embodiment of the disconnecting device is shown in FIG. lb. In this case, the disconnecting device consists of two parts, namely an overcurrent protection device 21 connected in series with an overvoltage leakage device 6, preferably formed by fusible fuses, and a short-circuit contact 22 connected in parallel to the leakage device. Overvoltage £ and is controlled by the switch lock £.

formed

The wires may be identified by reference numerals a_, any conductors b

In a conventional three-phase power supply network, the conductor and most often will consist of one of the conductors L1, the conductor PE. In spirit

L2 or L3 and the wire b will be the idea of the invention it is also possible to connect said series combination of the lead 6 and the break contact 2 i among other pairs of wire overvoltages:

for example between L1-N, L2-N, L3-N, L1-L2 and the like.

The amount of energy supplied to the resistance element can be determined according to the formula:

w * i * t

Therefore, the voltage at the leakage conductor is assumed as well as the device current

3, which is determined by lead 1 and which shows the above calculation.

As soon as the calculated amount of energy reaches a preset value (corresponding to the maximum possible energy absorption limit, or just below this maximum energy absorption limit), the circuit breaker lock 4 is activated, so that in the next step of the embodiment of FIG. 1a opens the break contact 2 and the lead 7 is disconnected from the mains. In the embodiment of FIG. 1b, the short-circuit contact 22 is closed and the overvoltage leakage is bridged by a connection with low electrical resistance. In this way, the short-circuiting of the conductors a, b causes a high current through the overcurrent protection device 21, which results in its activation and hence separation of the feeder from the mains.

If the protected lead is a varistor, which is very common in practice, it is possible to simplify the circuit diagram of FIG. 1a and FIG.

In fact, in its low ohmic state, the varistor has the property that the voltage e on its terminals has a constant current practically independent of current, this value being known.

The energy supplied is therefore proportional to the other unknown, the product of i * t, the integral of the current over time. In order to perform the above calculation, it is therefore necessary to measure the product i * t.

As shown in FIG. 2, the energy measuring device 3 for the varistors must comprise:

a first circuit 5 which generates a current through the overvoltage leakage 1 proportional to the signal a second circuit 6 which over time integrates this signal a threshold recognizing circuit 7 (symbolized by a comparator) which can activate the circuit breaker lock 6, which takes place at the latest when the line is leaked. The amount of energy supplied reaches the maximum possible energy absorption limit. Instead of

zobra zeného interrupter contact 2 is again possible use as on the Fig. lb shorting contact 22 in connection with equipment 21 na protection from overcurrent, what FIG. 2 no is a explicitly shown.

In a particularly simple manner, the described disconnection condition can be represented graphically, as in FIG.

3. The starting point of this diagram is the equation for the maximum possible energy absorption limit of the varistor:

^w max = u * i * t, where u = const.

therefore

W _max j proportional to ^e i * t

The plotted line g is the set of all points where the product i * t acquires a constant value which, when multiplied by a constant voltage, gives the maximum possible energy absorption limit of the varistor.

In the spirit of the invention, let us now assume that the tripping characteristic of the surge arrester according to the invention (not important as it is) is located by all its protected leads by points below the line g. can never occur

Then take too much energy to damage it.

A particularly simple practical embodiment of the block FIG. 2 is shown in the wiring diagram according to and will be explained in the following description.

4a, 4b

Again, an overvoltage protector 7 is used in which a break contact 2 is connected. 4a, the break contact 2 is connected after but it is not always necessary to use the conductors 1, it can be connected before the lead of FIG. 4b. It is also possible overvoltage. This arrangement because the overvoltage break contact, which clearly results in a disconnection of all poles of the feeder, can be achieved by placing the break contacts controlled by the switch in the two surge arresters. 4b.

This is shown in FIG.

Fig. 4c shows a practical embodiment of a block diagram of the apparatus according to the device shown in the dotted lines in accordance with FIG. lb. How can the device 21 be on /

the overcurrent protection removed from the current circuit 1 and can be wired across the device then not only the entire consumer system is disconnected from the mains. In a similar manner, the device 21 can be protected from being a disconnecting lead 7, but an arrangement of the assembly. When activated by overcurrent, it consists of house connection fuses, which are always available.

The leakage current 7 in this embodiment is determined by the current transformer 50. Due to its small dimensions, a current-carrying current transformer has proved particularly advantageous for this purpose.

Any other current measurement technique may be used in place of the current transformer 50. By way of example, a Hall probe or induction coil, in which the current through the lead 7 induces a voltage, is immediately used as a leakage current proportional to the signal.

As will be explained later, the dotted outlined filter circuit 10 is used only tentatively and, assuming it is not used, the capacitor is removed and the resistor is replaced by a short circuit.

The signal supplied by the current sensors must be integrated over time. Depending on the nature of the current sensor supplied, the corresponding circuit components must also be used. In the embodiment of FIG. 4, the leakage current is proportional to the current again, which after rectification by the diode 61 can be particularly easily integrated over time by means of a capacitor 60, because

U _c = 1 / C and dt

The integration thus results in an instantaneous voltage across the capacitor 60.

When using a sensor that returns a voltage signal, it is necessary to use a circuit that can integrate voltage values. The simplest example of this circuit is an operational amplifier connected as an integrator (see Figure 6c).

The capacitor capacitor voltage is supplied by

A zener diode 70 for the trigger relay 71, wherein the trigger relay 71 is coupled to the switch lock 4. As soon as the capacitor voltage exceeds the breakdown voltage of the Zener diode 70, the capacitor 60 is charged via the trigger relay 71 and causes a disconnection which can be accomplished by opening the break contact 2, but in accordance with the circuit shown in FIG. 1b can also be accomplished by short-circuiting the lead 6 and then activating the overcurrent protection device 21 connected before the lead 6.

The capacitor capacitance 60 and the breakdown voltage of the Zener diode 70 are selected in such a way that the disconnection takes place according to the invention before the maximum possible energy absorption limit of the lead is reached.

A manually operated return device 8 is provided for the restarting of the overvoltage isolation device. If the disconnecting device consists of a short-circuit contact 22 and an overcurrent protection device 21, the reconnection or replacement of the overcurrent protection device 21 must be carried out together with the reset of the switch lock.

The above-described type of control of the switch lock 6 operates independently of the mains voltage, but within the scope of the invention it is possible to realize by activating the switch lock 8 which is dependent on the mains voltage (shown in Fig. 5).

The principle construction corresponds to that of FIG. 4a. In this case, however, the capacitor 60 discharges via relay 72, which does not immediately open the switch lock 4, but connects the trigger relay 71 to the mains via contact 7 3. The trigger relay 71 is therefore activated and triggers the switch lock 6 associated therewith.

Instead of the break contact 2, can the leakage device be used here? 1 overvoltage bridging contact 2 2 in conjunction with an overcurrent protection device 21 connected in series with the overvoltage protector 1.

As is customary in switch protections of all kinds, a test device can be envisaged in the surge arrester of the present invention. This test device consists of a second primary coil 51 of the current transformer 50, which can be connected to the mains by means of a button 9. Upon pressing the button 9, an unacceptable high current through the line 7 is simulated, which, when the separator is properly operated, causes its activation.

In FIG. 4 and 5, the series combination of the overvoltage arresters and the break contact 2, respectively the series combination with the torsion arrester and the overcurrent protection device 21 are each connected between the conductors L and PE. However, this does not constitute a limitation of the use of the invention to these two conductors, as already mentioned in connection with the interpretation of FIG. 1 and 2. Said series combinations may also be connected between any conductor pairs of the power supply network.

The above-mentioned recognition of the limit value by the Zener diode 70 can be carried out in the spirit of the invention by other means, as in the circuits according to FIG. 6a-6c. For the sake of clarity, only the deployment of the trigger relay 71 is shown in these figures, but the remaining parts of the surge arrester are omitted.

In FIG. 6a, the Zener diode is replaced by a transistor assembly 11 operating in a closing direction, which in the simplest case consists of one transistor.

Transition base emitter of this transistor is in series and in the forming direction connected in series with the trigger relay 71, at a precisely defined voltage breaks (similar to

Zener diode) and thereby allow current to flow through the trigger relay 71. By using a series connection of a plurality of transistors (indicated by a dashed line), the breakdown voltage of the transistor assembly 11 can be increased in a simple manner.

Normally, only small currents can flow through the transistor base to the transistor, which are usually too small to trigger the trigger relay 7 1. Therefore, it is necessary to complement the transistor structure 11 with additional circuit elements of greater power. An example of this addition is shown in FIG. 6b.

The transistor structure 11 consists of transistors 12 and 13 and resistors 14 and 15. The capacitor 16 may be advantageous because it shortens the interference signals. The transistors 12 and 13 are interconnected by positive feedback. The resistors 14 and 15 serve for the high ohmic connection of the transistor assembly 11, thereby ensuring that the transistor assembly 11 does not appear to be a load on the capacitor 60 during its charging. Transistors 14, 15 should be selected with high current amplification. Once the transistor structure 11 becomes conductive in its closing direction, the voltage drop across the resistor 14 ensures that the transistor 12 goes into a conductive state. The current, which then flows through the resistor 15, causes a voltage drop across it, due to which the transistor 13 goes into a conductive state. An even greater current will then flow through the resistor 14, since the voltage drop across the transistor 13, which is in the conductive state, is substantially lower.

Therefore, it can be said that the triggered current 71 flows virtually emitter-collector

12, only conductive and therefore the junction may have an amplitude that is necessary to activate the respective trigger relay without causing any damage.

According to an embodiment of the illustrated invention,

6c, the threshold recognition by the amplifier 20 is shown in FIG.

values that is connected as a comparator. Integration of the signal, which is proportional to the leakage current, provided by the operational amplifier

17, a capacitor having, due to the connection with resistor 19, the characteristics of a known integrator.

In FIG. 6a-6c, the limit value recognition circuits and the integration circuits, respectively, may be used in any combination. For example, the capacitor 60 of FIG. 6a, 6b can be replaced by the operational amplifier 17 of FIG. 6c. Conversely, the transistor structure 11 of FIG. 6a, 6b it is possible to replace the operational amplifier 20, which acts as a comparator.

In the event of an impermissibly high overvoltage, the arrester must perform its function without being disturbed in any way, i.e. without the overvoltage arrester being activated. In the separator of the type described so far, this condition is maintained only if the amount of surge surge energy is less than the maximum possible energy absorption limit of the downcomer.

The purpose of use from the surge conductor, however, is to dissipate the surge regardless of their energy content, although this could eventually destroy the aquifers. The electrical strength against the surge currents of the leakage separator, which has so far been considered only for 'energy-poor surge surges', should therefore be extended to 'energy-rich surge surges'.

To solve this problem, according to the invention, it is envisaged not to take into account, when calculating the amount of electrical energy supplied to the arrester, the currents flowing through the protected arrester 7 whose frequency is greater than the grid frequency.

Circumferentially, this task is realized in such a way that generating a current through the overvoltage leakage 10 proportional to the connected filter circuit 10, which limits the signal beyond the circuit 5, is a leakage current proportional to a signal whose frequency is equal to that of the network. Initially, the aforementioned TOV transient overvoltage have a grid frequency, and thus are fully included in the calculation of the amount of energy absorbed by the overvoltage discharge device and therefore respond to them.

In order to ensure that the unsuitable frequencies are suppressed, the filter circuit 10 must have a frequency response similar to that of a low pass or band pass and be tuned to the network frequency.

In FIG. 2, this filter circuit 10 is indicated by a dashed line. This circuit can be practically realized by a simple passive RC double gate (indicated in Figs. 4 and 5), but also by any other known connection having the necessary transmission properties.

Claims (14)

PATENT A separation equipment on water (1) overvoltage, containing current from v o to m (D overvoltage determining equipment (3) and these equipment (3) triggered disconnect device which ones performs disconnection z v o d Fc * '(1) power surge, v y wit u j u c e clothes m, the device (3) figuring out downpipe (1) energy surge and at reaching forward adjustable quantity energy, which ones is smaller or equal maximum possible energy absorption limit of the protected overvoltage, the disconnecting device is activated. Isolation device according to claim 1, characterized in that the isolation device comprises a break contact (2) which is connected in series with the overvoltage protector (1) and is controlled by the circuit breaker lock (4). Separating device according to claim 1, characterized in that the overvoltage protection device (21) connected to the overvoltage wires (1), preferably fusible fuses and a short-circuit contact (22) connected in parallel to the surge conductors (1), is connected in series. zvodflM. (1) overvoltage and is controlled by the key switch (4). Separation device according to claim 1 2 or 3, characterized in that the energy-determining device (3) is a series combination of a first circuit (5) that generates a signal proportional to the current through the overvoltage (1) of the second circuit (6), which over time integrates this signal and the threshold value of the recognition circuit (7), the switch lock (4). who controls Separation device according to claim 4, characterized in that the signal generating circuit (5) which is proportional to the current through the overvoltage (1) is formed by a current measuring transformer, preferably by a current measuring current transformer. Separation device according to claim 4, characterized in that the signal circuit (5) which is proportional to the current leakage is formed by a Hall probe. designed to create (1) overvoltage, 7, characterized in that the integration circuit (6) comprises a rectifier circuit (61) of a capacitor (60). Separation device according to one of claims 4 to 4, characterized in that the integration circuit (6) of the rectifier circuit (61) of the operational amplifier comprises (17) connected as an integrator. Separation device according to claim 4, characterized in that the signal circuit (5) which is proportional to the current leakage is formed by an induction coil. designed to create (1) overvoltage, Separation device according to one of claims 4 to 10 9, characterized in that the threshold value recognition circuit (7) is a transistor structure (11) operated in the closing direction. 9, characterized in that the threshold recognition circuit (7) is formed by an operational amplifier (20). 9, characterized in that the threshold recognition circuit (7) is formed by a Zener diode (70). Separation device according to one of claims 4 to 10 Separation device according to one of claims 4 to 11 12, characterized in that a filter circuit (10), which limits the leakage current, is proportional to the signal whose frequency is less , re spe kt ive equals the network frequency. Separation device according to one of claims 4 to 12 Separation device according to one of claims 4 to 15 14. A separation equipment according to claim 13, v y z on the No. u j u c e sa t filtering circuit (10) my lower characteristic culverts. 15 Dec A separation equipment according to claim 13, v y z on the No. u j u c e sa t filtering circuit (10) my band-pass characteristic.