CH642482A5 - Electrical safety device for quick-action disconnection of an electrical mains circuit - Google Patents

Description

The invention relates to an electrical safety device for quickly switching off an electrical mains circuit according to the preamble of claim 1.

Electrical emergency switches for interrupting electrical mains circuits in emergencies are often found in laboratories,

Workshops, factories and commercial facilities application. These emergency switches are usually large, striking red push-button switches that are located in easily accessible places to enable a quick power cut in the event of an emergency.

In known safety systems, the emergency switch is an open pushbutton in the idle state, via which the trigger coil of a circuit breaker protecting the circuit in question is energized when actuated. As a result, separate line connections must be made between the circuit breaker and any location where an emergency switch is to be placed. The cost and complexity of this additional line network often means that fewer emergency switches are actually installed than would actually be desirable. In other cases, it is even possible to completely dispense with the installation of such a security system because of the cost and the complexity of the security system.

Due to the technical connection conditions, safety regulations and other technical guidelines applicable to the power supply, in addition to overload protection, fault current protection is also required for the electrical installations of industrial and commercial companies as well as for household installations. The residual current protective devices are normally designed in such a way that they switch off the relevant electrical mains circuit as soon as fault currents occur, which are much smaller than the tripping currents of the overload protection devices. For example, residual current circuit breakers for household installations are often designed in such a way that they trip at a residual current (earth fault current) of 5 mA.

The invention is based on the object of designing a safety device of the type mentioned at the outset in such a way that a special safety line network is unnecessary.

This object is achieved according to the invention by the arrangement specified in the characterizing part of claim 1.

The safety device according to the invention has the advantage that, apart from the already present conductors of the relevant mains circuit, it does not require any special safety lines, it can be plugged into any socket, portable and easily exchangeable.

In the first basic embodiment of the invention characterized in claim 2, a connection between the phase conductor and the protective conductor is established when the switch is closed. By switching on a correspondingly dimensioned impedance according to claims 5 to 7, it is ensured that when the switch is closed there is no short circuit, but only a fault current with a current strength above the tripping current of the fault current circuit breaker is established. By actuating the switch, a fault current is deliberately caused, which triggers the fault current circuit breaker assigned to the circuit in question, the latter already being present in most electrical installation systems and already mandatory for new systems.

In the case of mains socket-mains plug systems with asymmetrical plug contact arrangement, i.e. With a fixed, non-interchangeable assignment of the individual plug contacts to the phase conductor contact and to the neutral conductor contact of the socket, a simple switch that is connected between the plug contact assigned to the phase conductor and the protective conductor contact of the plug device is sufficient (claim 2).

In the case of mains socket-mains plug systems in which the plug contacts (for example in the German Schuko system) form a rotationally symmetrical arrangement and the two plug contacts for phase and zero when plugged in

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

3rd

642 482

are exchangeable in the phase conductor contact or the neutral conductor contact of the socket, a two-pole switch (claim 3) is required, which is connected on the one hand to the two plug contacts for phase and zero and on the other hand to the protective conductor contact of the plug device and consequently both plug contacts for phase when actuated and connects zero to the protective conductor contact at the same time. This ensures that regardless of the type of insertion of the plug device into the socket, a connection between the phase conductor and protective conductor is established in any case, which results in a fault current.

In multi-phase circuits with multi-phase sockets, a simple switch is sufficient, which is connected between any of the plug contacts assigned to the different phase conductors and the protective conductor contact of the plug device (claim 4), since the residual current circuit breaker always triggers when between any one Phase and the protective conductor a fault current occurs.

The above-mentioned first basic embodiment of the invention can also be used in single-phase or multi-phase mains circuits which branch behind the residual current circuit breaker and in which the phase conductor of each branch is protected with its own overload protection. The entire circuit can then be switched off by operating a safety device according to the invention in any circuit branch. However, this has the prerequisite in the embodiment mentioned that the overload protection of the circuit branch in question is switched on, that is to say the phase conductor of the circuit branch in question is live. Otherwise, no fault current could be generated by operating the safety device.

However, it may also be desirable to be able to trigger a circuit shutdown in a branched and individually secured network circuit from any circuit branch by means of the safety device according to the invention even if the overload protection of the circuit branch in question is triggered and the associated phase conductor is consequently interrupted.

For this purpose, in a second basic embodiment of the invention characterized in claim 8, which can be used in conjunction with residual current circuit breakers which also trigger when a low-impedance connection between the neutral conductor and the protective conductor occurs, the switch between those assigned to the neutral conductor Plug contact and the protective conductor contact of the plug device switched. When actuated, the switch establishes a low-resistance connection between the neutral conductor and the protective conductor, which triggers the residual current circuit breaker.

Since considerable currents can also flow in the neutral conductor when the circuit is under heavy load, a low-impedance impedance for current limitation is preferably connected in series with the switch.

In all cases, the switch is advantageously a push button.

Some embodiments of the invention are described in more detail below with reference to the accompanying drawings. It shows:

1 shows a safety device 10 according to the invention for generating a fault current between phase and protective conductor,

2 shows a safety device 10 according to the invention for establishing a low-resistance connection between neutral conductor and protective conductor,

Fig. 3 shows a modification of the safety device

Fig. 1 for socket connector systems with rotationally symmetrical plug contact arrangement, and

Fig. 4 shows a development of a safety device according to Fig. 1 for a three-phase socket.

Fig. 1 shows an electrical mains circuit 1 with three conductors, namely a phase conductor L, a neutral conductor N and an earthed protective conductor G. The circuit 1 connected to the left in the drawing to a power source (supply network), not shown, has a number of sockets 2 for Plug in the electrical equipment to be connected; one of these sockets is shown for example. The socket 2 has a contact 3 connected to the phase conductor L, a contact 4 connected to the neutral conductor N and a contact 5 connected to the grounded protective conductor.

The circuit 1 is protected by a fault current circuit breaker 6 which is arranged between the supplying network and the first socket and has an opener 7 located in the phase line L. If a fault current occurs between the phase conductor L and earth as a result of an earth fault and the fault current exceeds a predetermined limit value, the fault current circuit breaker 6 is triggered and the part of the circuit located behind the fault current circuit breaker is disconnected from the mains by opening the contacts of the break contact 7 .

The tripping current of the residual current at which the residual current circuit breaker 6 responds depends on the respective application. For example, for protection against accidental contact with people, the residual current circuit breaker is designed so that a person coming into contact with the phase conductor L and earth at the same time cannot suffer serious damage. The tripping current for this purpose is about 5 mA. This tripping current is of course much smaller than the overload tripping current, since the overload protection is mainly used to protect the conductor itself from damage caused by overcurrents with currents in the range of a few amperes or more.

The safety device 10 shown is used to deliberately induce a fault current between the phase conductor L and earth. If the current of this fault current reaches the tripping current of the fault current circuit breaker 6, it trips and thus disconnects the circuit from the mains.

The safety device 10 is designed as a plug-in device, which is shaped like a mains plug, but contains a switch 11 in the form of a push button with a push button 12. The plug pins 13, 14 and 15 of the plug device come into contact with the conductors L, N and G by plugging into the associated contacts 3, 4 and 5 of the socket 2. The switch 11 and a resistor 16 connected in series therewith are connected between the plug pins 13 and 15, which are assigned to the phase conductor L and the protective conductor G. Accordingly, when the switch is actuated, an electrical connection is established between the pin 13 and the pin 15 by pressing the pushbutton 12, and when the plug device 10 is plugged into the socket 2, a fault current then flows from the phase conductor L via the socket contact 3 Connector pin 13, the resistor 16, the switch 11, the connector pin 15 and the socket contact 5 to the grounded protective conductor G. The resistance value of the resistor 11 is selected in accordance with the mains voltage on the circuit 1 so that the current strength of the resulting fault current is greater than the tripping current strength of the Residual current circuit breaker 6 is. When the pushbutton is actuated, the residual current circuit breaker 6 thus triggers and thereby disconnects the circuit 1 or its part behind the residual current circuit breaker from the mains.

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

642 482

4th

For example, with an AC line voltage of 115 V, the residual current circuit breaker 6 can be set to a tripping current of 5 mA, so that a person who comes into contact with the phase conductor L and earth at the same time is protected against serious damage. When the resistance 16 is rated at 10 kD, a fault current of approximately 12 mA is set when the pushbutton is pressed. This residual current is sufficiently above the tripping current of the residual current circuit breaker 6,

however, far below the overcurrent tripping threshold at which there is a risk of damaging the conductors of the circuit 1.

By choosing a resistance value for the resistor 16 which results in a fault current which is far above the tripping current of the residual current circuit breaker at normal mains voltage, a sufficiently large safety area is obtained which ensures that even in emergency situations in which the mains voltage can drop sharply, a sufficiently high residual current is set to trigger the residual current circuit breaker.

The resistor 16 is not absolutely necessary for the mode of operation of the safety device according to the invention. However, its presence limits the magnitude of the earth fault fault current which arises when the pushbutton is actuated, so that cheap low-current contacts can be used for the switch 16. Instead of a resistor, an impedance can also be selected to limit the current.

A number of advantages are obtained by designing the safety device as a plug device. The plug device can be plugged into any socket 2 of the circuit 1, and any number of sockets of this circuit can be equipped with such safety devices. The cost of a connector is much less than the installation cost of a conventional emergency switch, which requires separate wiring to connect to the trip coil of a circuit breaker. Furthermore, if, for example, an emergency switch is temporarily required at a point remote from the network, the plug device 10 can be connected to the network via a conventional extension cable which is plugged into a socket 2. The plug device can thus be easily brought to any location from which an emergency shutdown should be possible. In addition, the plug-in device can be carried by personnel and used at any location where there is a socket.

Fig. 2 shows a branched mains circuit la, which is connected to a current source (supply network) in the drawing on the left and has two phase conductors LI and L2, a neutral conductor N and a protective conductor G. The circuit la is protected with a residual current circuit breaker 6a, which contains one break contact 7 per phase. The neutral conductor N is grounded in front of the residual current circuit breaker 6a and the protective conductor G is connected to the neutral conductor. Several branch circuits 21, 23, 25 branch off behind the residual current circuit breaker, each having a phase conductor L ', a neutral conductor N' and a protective conductor G ', the neutral conductor N' and the protective conductor G 'of each branch circuit being connected to the neutral conductor N and the protective conductor G and the phase conductor L 'of each branch circuit are connected to one of the two phase conductors LI and L2 and are each protected by their own single-pole overcurrent protective switch 22, 24 and 26, respectively.

In the circuit shown in FIG. 2, the embodiment of the safety device described above with reference to FIG. 1 can only trigger the residual current circuit breaker when the switch is actuated if the

Overcurrent protection switch 22 or 24 or 26 of the relevant branch circuit, with which the safety device is connected by plugging into a socket connected to it, is not switched off. If the overcurrent protection switch in question is switched off, the phase conductor of the branch circuit in question is de-energized and consequently no fault current can be generated to trigger the fault current protection switch by actuating the embodiment of the safety device already described.

The safety device shown in FIG. 2 enables the residual current circuit breaker 6a to be triggered by actuating a plug device 10 plugged into a socket 2 of any branch circuit 21, 23 or 25 even when the overcurrent circuit breaker in the phase conductor L 'of the branch circuit concerned is switched off .

In the arrangement shown in FIG. 2, the residual current circuit breaker 6a additionally has a device 20 for generating voltage pulses which are transmitted to the neutral conductor N via an exciter transformer 27. If a low-impedance connection is established between the neutral conductor N and earth behind the residual current circuit breaker, a circuit is closed so that pulse currents flow due to the voltage pulses induced in the neutral conductor. The residual current circuit breaker contains means that respond to these pulse currents and immediately trigger the residual current circuit breaker, so that when a low-resistance connection between the neutral conductor and earth occurs behind the residual current circuit breaker, the break contact 7 is opened and thus the entire circuit is disconnected la from the supply network. This neutral earth-fault circuit protection is often used in residual current circuit breakers to increase the safety and reliability of the residual current circuit breaker, because although a grounded neutral conductor is not a danger in itself, a ground fault of the neutral conductor can increase the sensitivity of the residual current - Reduce the circuit breaker for residual currents. A more detailed description of such residual current circuit breakers with neutral earth fault protection can be found, for example, in US Pat. Nos. 3959693 and 3611035.

The safety device 10 shown in Fig. 2 is used to intentionally ground the neutral, i.e. establish a low-resistance connection between neutral conductor and protective conductor. For this purpose, the switch 11 of the plug device 10 in the embodiment according to FIG. 2 is connected between the plug pin 14, which interacts with the socket contact 4 connected to the neutral conductor N ', and the plug contact 15, which connects with the protective conductor G' Socket contact 5 interacts. A low-resistance resistor 16a is connected in series with the switch 11 and has, for example, a value of lfi. Although this resistor is not absolutely necessary for the functioning of the safety device, it is advantageous for current limitation, since a considerable current flows through the neutral conductor when the relevant branch current is heavily loaded, since cheap low-current contacts can then be used for the switch 11. Instead of a resistor, it is of course also possible to use another impedance, for example a coil or a capacitor, to limit the current.

When the switch 11 is actuated by pressing the push button 12, an electrical connection is established between the plug pins 14 and 15, so that when the plug device 10 is plugged into a socket 2, corresponding pulse currents via the branch circuit due to the voltage pulses induced in the neutral conductor N Neutral conductor N ', the socket contact 4, the plug pin 14, the switch 11, the resistor 16a, the plug pin 15, the

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

5

642 482

Socket protective conductor contact 5 and the protective conductor can flow. These pulse currents are detected by the residual current circuit breaker, which then trips and disconnects the entire circuit la from the network.

The embodiments described above with reference to FIGS. 1 and 2 are tailored to mains socket / mains plug systems with a plug contact arrangement in which the three plug contacts, due to their different shape and their non-rotationally symmetrical arrangement when inserted, are unmistakably the phase conductor contact 10 or the neutral conductor contact or the protective conductor contact of the socket are assigned, so that a specific plug pin of the plug pins is clearly assigned to the phase conductor and another specific plug pin is clearly assigned to the neutral conductor. 15

In the case of socket-plug systems with a rotationally symmetrical plug-in contact arrangement and identical shape of the two-phase and zero-assigned plug contacts, for example in the German Schuko system, the plug can be securely plugged into the socket in two different positions, namely rotated by 180 °, so that one of these two plug contacts comes into contact with the phase conductor and the other of these two plug contacts comes into contact with the 25 neutral conductor of the two plug contacts provided for phase and zero, depending on the type of insertion of the plug into the socket, this respective plug contact assignment being made by reversed insertion of the plug is interchangeable.

When realizing a safety device of the basic type described above with reference to FIG. 1 to be used in connection with sockets of such a plug-socket system, a fault current between the phase conductor and the neutral conductor is therefore required for this purpose Care should be taken to ensure that a connection between the phase conductor and the neutral conductor is established regardless of the type of insertion of the safety device, which in turn is designed as a plug device, into the socket.

FIG. 3 shows a plug device 40 in connection with a German Schuko socket 32. The socket 40 has two symmetrically arranged contacts 33 and 34 of the same shape, which are connected to the phase conductor L and the neutral conductor N

are connected. In addition, the socket has two electrically connected protective contact springs 35 which are connected to the protective conductor G.

Correspondingly, the plug device 40 has two plug pins 43 and 44, which can be inserted into the socket contacts 33 and 34, and two protective conductor contacts 45, which cooperate with the contact springs 35 of the socket when inserted. So that when the pushbutton 12 of the plug device 40 is actuated, a fault current can be generated between the phase and the protective conductor regardless of whether the plug pin 40 with the contact 33 and the plug pin 44 with the contact 34 or, when the plug is inserted in the opposite direction, when the plug device 40 is inserted Plug pin 43 with the contact 34 and the plug pin 44 with the contact 33 of the socket 32 comes into contact, the plug device 40 contains two coupled and actuable switches 1 la and IIb, each with the protective conductor contacts 45 and the plug pin 43 or the plug pin 44 and are each connected in series with a current limiting resistor 46a or 46b.

Fig. 4 shows a safety device for generating a fault current, which can be inserted into a three-phase socket of a three-phase circuit.

The three-phase socket 52 has four contacts 53, 54, 55 and 56, which are connected to the neutral conductor N and the three phase conductors R, S and T, and a protective conductor contact 57, which is connected to the protective conductor G. Guide lugs 58 prevent incorrect insertion of a plug.

The safety device 60 designed as a plug device has four plug pins 63, 64, 65 and 66, which are assigned to the neutral conductor contact 53 or the three phase conductor contacts 54, 55 and 56 of the socket, and a protective conductor contact plug 67. Since it is sufficient to trigger the residual current circuit breaker to generate a residual current between any phase and the protective conductor, the plug device 60 contains a switch 61 which is connected to the protective conductor contact pin 67 and one of the three connector pins assigned to the three phases, for example that of the Phase R associated pin 64 connected and connected in series with a current limiting resistor 62.

G

3 sheets of drawings

Claims (8)

642 482 1 lb; 61) an impedance (16; 46b, 62) is connected in series. 1.Electrical safety device for the rapid shutdown of an electrical mains circuit, which contains at least one phase conductor, a neutral conductor and a grounded protective conductor and a number of mains sockets and is protected by a residual current circuit breaker, characterized in that the safety device is designed as a mains socket (2; 32 ; 52) insertable plug device (10; 40; 60) with an open, in the idle state, manually operated switch (11; lia, 1 lb; 61) is formed, which is connected between the plug contacts of the plug device in such a way that it activates when actuated Leakage current from the value ensuring the tripping of the residual current circuit breaker flows to the protective conductor (G). 2. Electrical safety device according to claim 1, characterized in that the switch (11) between the phase conductor (L) associated plug contact (13) of the plug-in device (10) and the protective conductor (G) associated plug contact (15) is connected and at Actuation creates a ground fault current between the phase and protective conductor with a current that exceeds the tripping current of the residual current circuit breaker (6). 2nd PATENT CLAIMS 3. Safety device according to claim 1 or 2 for a single-phase mains circuit and sockets with a rotationally symmetrical plug contact arrangement, in which the two plug contacts for phase and neutral when plugged in can be plugged into the plug-in device contacts assigned to the phase or neutral conductor, characterized in that two switches (lia, 1 lb) are provided, which are connected on the one hand to the two plug contacts (43, 44) for phase (L) and neutral conductor (N) and on the other hand to the protective conductor contact (45) of the plug device (40). 4. Safety device according to claim 1 or 2 for a multiphase mains circuit with multiphase sockets, characterized in that the switch (61) between one of the phase contacts (R, S, T) assigned to the plug contacts (64, 65, 66) and the protective conductor contact ( 67) of the plug device (60) is switched. 5. Safety device according to one of claims 1 to 4, characterized in that with the switch (11; 1 la, 6. Safety device according to claim 5, characterized in that the impedance is a resistor (16; 46a, 46b; 62). 7. Safety device according to claim 5 or 6, characterized in that the impedance or resistance value is dimensioned such that the current intensity of the ground fault current which occurs when the switch (11; 1 la, 1 lb; 61) is actuated is at least twice the tripping current strength of the residual current circuit breaker (6). 8. Safety device according to claim 1 for a mains circuit, in which the residual current circuit breaker also triggers when a low-resistance connection occurs between the neutral conductor and the protective conductor, characterized in that the switch (11) between the plug contact (14) assigned to the neutral conductor (N) ) and the plug contact (15) of the plug device (10) assigned to the protective conductor.