As it is known, residual current-operated circuit breakers are normally provided in home and industrial systems in order to prevent a fault current from causing danger to users and to the loads connected to the electric line.

Essentially, the residual current-operated circuit breaker, when it detects the fault current, disconnects the line, accordingly interrupting the supply of power to the load or loads arranged downstream.

After the release of the residual current-operated circuit breaker, and once the correct operating conditions of the system have been restored, the residual current- operated circuit breaker must be reset.

The operating conditions often restore themselves spontaneously, because the fault is of a transient type caused by overvoltages.

Such reset normally occurs manually by acting on an appropriately provided reset lever.

However, if the user performs the reset after an opening or release of the residual current-operated circuit breaker, he cannot be sure that the fault has been removed.

Therefore, when the user performs the reset, a subsequent closely spaced release of the residual current-operated circuit breaker can occur, because the problem has not been solved correctly.

The aim of the present invention is to provide an automatic reset device particularly for residual current-operated circuit breakers and the like that allows to check the correct operation and status of the system before resetting the residual current- operated circuit breaker.

Within this aim, an object of the present invention is to provide an automatic reset device particularly for residual current-operated circuit breakers that provides the user

with assurance of continuity of service by reclosing the residual current-operated circuit breaker after temporary faults, after checking the status of the system before performing the actual reset.

Another object of the present invention is to provide an automatic reset device that is furthermore capable of checking the correct connection of the device itself to the system.

Another object of the present invention is to provide an automatic reset device that is highly reliable, relatively simple to provide and at competitive costs.

This aim and these and other objects that will become better apparent hereinafter are achieved by an automatic reset device, which includes an actuator for automatically resetting a residual current-operated circuit breaker that is connected to an electrical line, upstream of a load, characterized in that it includes control means that is suitable to actuate the actuator, the control means being connected upstream of the residual current-operated circuit breaker and downstream of the residual current-operated circuit breaker, upstream of the load, in order to bypass the residual current-operated circuit breaker when the residual current-operated circuit breaker is released, the control means including a circuit for checking the connection of the reset device to the electrical line and a circuit for detecting leakage current, in order to check for the presence of a leakage current, before actuating the actuator to automatically reset the residual current-operated circuit breaker.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the reset device according to the present invention, illustrated by way of non-limiting example in the accompanying drawings, wherein: Figure 1 is a general circuit diagram of the device according to the present invention; Figure 2 is a block diagram of the reset device according to the present invention; and Figure 3 is a circuit diagram of the reset device according to the present invention.

With reference to the figures cited above, the reset device according to the

present invention, associated with a residual current-operated circuit breaker, includes control means 1, which is conveniently connected to a residual current-operated circuit breaker 2 by virtue of connections 3 and 4, which connect the control means 1 downstream of the residual current-operated circuit breaker 2 and upstream of a load 5 on one side and upstream of the residual current-operated circuit breaker 2 by way of connections 6 and 7 on the other side, so as to bypass the residual current-operated circuit breaker, without any connection to the ground system.

Figure 1 and the other figures show the electrical line with the phase 8 and the neutral 9.

The control means 1, conveniently constituted by a control board, is therefore interposed between the electrical line and the residual current-operated circuit breaker 2 and between the residual current-operated circuit breaker 2 and the load 5, accordingly constituting a bypass of the residual current-operated circuit breaker.

An actuation means 10, suitable to actuate the resetting of the residual current- operated circuit breaker 2, is connected to the control board 1 and powered by the line 8, 9 by virtue of the connection of the control board 1 to the line.

In detail, the control means 1 includes a control unit 15, which is connected to a power supply means 16 so as to derive a control voltage that is equal to half the mains supply voltage of the device. The power supply means furthermore includes a power supply 17 for the control unit.

The device furthermore has a circuit for detecting the presence and value of the power supply voltage, designated by the reference numeral 18, which is connected to the control unit 15 and sends to the control unit a response signal 19 related to the presence and value of the supply voltage.

A circuit 20 for checking the cables connected to the system, electrically separated from the remaining circuit, is further connected to the control unit 15 in order to verify the correct connection of the cables, i. e. , verify that the reset device is correctly connected to the system.

The circuit 20 receives in input a signal 21 requesting a check of the connection of the cables and outputs to the control unit 15 a signal 22 that indicates the outcome of the

cable check.

The device according to the invention furthermore includes a circuit 23 for detecting the leakage current of the connected system; this detection occurs by virtue of a unidirectional pulsed voltage derived from the mains voltage, which is closed, in case of fault, on the mains by virtue of the ground ; finally, the device includes a circuit 24 for protection against electrical shocks during the system verification cycle.

The control unit 15 sends an actuation signal 25 to the thermal actuator 10 in order to activate the reset device.

With reference to the figures, the operation of the reset device according to the present invention is as follows.

The control means 1 is supplied with power by the closure of a contact 30 exclusively after release of the associated residual current-operated circuit breaker, which opens the contacts 2 and removes power from the system.

The control means closes immediately a relay 31, connecting the system to be verified to the previously described measurement circuits.

The control unit 15 sends a signal requesting a check of the cables 21 to the control circuit 20, which checks the connection of the cables, verifying that there is an impedance between test points A and B. This verification indicates correct connection of the device to the system before continuing the test sequence. An impedance value exceeding a preset value prevents the reset device from continuing the sequence.

At this point, the control unit 15 verifies, by virtue of the circuit 23, the possible presence of an earth leakage current, and if the earth leakage current exceeds a preset threshold it blocks the automatic reclosure of the device.

If one of the two verifications described above fails, the device reports the anomaly by switching on a LED with a steady light.

If the entire first step ends with a positive outcome, the control unit provides power to the thermal actuator 10 in order to reset the device. Such thermal actuator is a hot-wax actuator, which resets the associated residual current-operated circuit breaker, accordingly supplying power to the system connected thereto.

If the residual current-operated circuit breaker trips a second time within a preset time, the reset device does not attempt a second reset and remains in a blocked status, which is indicated by the fixed lighting of the above cited LED, until the associated circuit breaker is reset manually.

Substantially, the automatic reset device according to the present invention allows to check both the connection of the reset device and any occurring leakage current before being able to actually actuate the automatic reset of the residual current-operated circuit breaker.

In practice it has been found that the device according to the present invention fully achieves the intended aim and objects, since it allows to perform, prior to an automatic reset operation, a series of checks on the device and on the system in order to perform a reset if the conditions are such as to ensure subsequent correct operation of the system.

The device thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims ; all the details may furthermore be constituted by other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.