DE202015009358U1 - RCD - Google Patents

Abstract

Residual current device (1) comprising a differential current transformer (12) having a primary winding (18) comprising at least one phase conductor (3, 3 ', 3' ') and a neutral conductor (4) and a core (21), a secondary winding ( 19) and a test winding (20), with which the differential current transformer (12) can be acted upon by a test current to simulate a defined differential current, the residual current device (1) further comprising a control unit (11) to the test winding (20). for controlling the test current and for measuring a secondary voltage induced in the secondary winding (19) and / or a secondary current resulting from the induced secondary voltage, characterized in that the control unit (11) for calibrating the residual current protective device (1) is designed such that in the case of a deviation of the measured voltage value of the secondary voltage caused by the test current from a voltage In the case of a deviation of the measured current value of the secondary current caused by the test current from a current setpoint, a correction factor is calculated with which the measured voltage values of the secondary voltage caused by differential currents and / or measured current values of the secondary current caused by differential currents are multiplied.

Description

FIELD OF THE INVENTION

The present invention relates to a residual current device comprising a differential current transformer having a primary winding comprising at least one phase conductor and a neutral and a core, a secondary winding and a test winding, with which the differential current transformer can be acted upon by a test current to a defined differential current simulating, the residual current device further comprising a control unit to control the test winding for generating the test current and to measure a induced secondary voltage in the secondary winding and / or a secondary current resulting from the induced secondary voltage.

STATE OF THE ART

Ensuring the safe operation of electrical equipment, in particular of power tools during construction and assembly work, is a challenge, especially as in construction sites faulty electrical installations can not be excluded. In order to increase the safety of users of electrical equipment, therefore, a portable residual current device (sometimes referred to as "portable residual current device" or simply referred to as "PRCD") is connected to the provided via the existing electrical installations low-voltage network. The electrical equipment, in particular power tools are then connected to the portable residual current device - and not directly to the low-voltage network. In principle, however, residual current protective devices must also be provided in completed electrical installations for providing a low-voltage network. A low-voltage network is understood to mean an AC network with an effective voltage of typically 130 V to 1000 V, in particular of 230 V to 400 V.

To detect the fault current in residual current protective devices usually a summation current transformer or differential current transformer is used. The conductors to be monitored, which consist of at least one phase conductor and a neutral conductor, form a primary side with a primary winding of this transformer. In normal operation, their magnetic effect is canceled due to the opposite wiring. Only in the presence of a fault current or differential current, which preferably flows to earth due to a fault, a voltage or secondary voltage is induced in a secondary winding or in a secondary side of the transformer. If the induced secondary voltage and / or a secondary current connected thereto are above set threshold values, this is detected by the fault current protection device as an error. Thereafter, the lines are disconnected from the residual current device, preferably by means of dedicated switch contacts and a switching means (e.g., relays).

The transformer usually has a core, preferably of iron or ferrite. The magnetic flux that triggers is rather small compared to the possible magnetization of the core. Depending on the material used, the core material has a more or less pronounced magnetic remanence. Strong magnetization due to a very large differential current, for example due to a short circuit between a phase conductor and a protective conductor, can drive the core to saturation. Furthermore, strong magnetization can also be caused by momentary currents occurring at power-up between the at least one phase conductor or the neutral conductor and the protective conductor. Such pulse currents are e.g. caused by suppression capacitors of class Y used for radio interference suppression. Due to the strong magnetization, the operating point of the transformer can shift permanently along its remanence characteristic. This is also called a magnetic hysteresis.

In practice, this leads to a change in the sensitivity of the transformer or the residual current device, typically in the range up to ± 50%. As a result, the tripping threshold shifts and the residual current device may be less sensitive, but in some cases more sensitive than intended. In particular, the former case involves a significant security risk for users.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide a residual current device which avoids the above-described disadvantages, in particular too low a sensitivity to fault currents or differential currents.

PRESENTATION OF THE INVENTION

According to the invention, the above object is achieved by providing a self-calibrating residual current device. For this purpose, it is in a residual current device comprising a differential current transformer having a primary winding comprising at least one phase conductor and a neutral conductor and a core, a secondary winding and a test winding, with which the differential current transformer can be acted upon by a test current to simulate a defined differential current, the residual current device further comprising a control unit to drive the test winding for generating the test current and a induced secondary voltage in the secondary winding and / or According to the invention, the control unit for calibrating the residual current protective device is designed so that in the event of a deviation of the measured voltage value of the secondary voltage caused by the test current of a voltage setpoint and / or a deviation of the measured current value by the Test current caused secondary current from a current setpoint, a correction factor is calculated, with the measured voltage values of the secondary voltage caused by differential currents and / or measured Stromwer te of the secondary currents caused by differential currents.

In addition to the at least one phase conductor and the neutral conductor, a protective conductor can also form part of the primary winding. In this case, the protective conductor is "wrong" out in a conventional manner, so that a flowing through him on the at least one phase conductor and a load fault current in the effect does not cancel, but amplified.

The voltage induced in the secondary winding is caused by a differential current between the at least one phase conductor and the neutral conductor or by the test current, which simulates a defined differential current. In this case, the magnetic flux associated with the respective current induces the secondary voltage. The test current is preferably a very precisely defined, sinusoidal alternating current in order to simulate a defined differential current between the at least one phase conductor and the neutral conductor. The test current is generated by the control unit, which has corresponding, controlled by at least one microprocessor electronics.

When measuring the secondary voltage or the secondary current flowing through the secondary winding due to the induced secondary voltage, it is preferably provided that the control unit amplifies the secondary voltage / the secondary current and generates a digital signal by means of an analog-to-digital converter, which by means of at least one microprocessor is processed and evaluated.

The correction factor basically results from the quotient of setpoint (dividend) and measured value (divisor). In this way, various factors, such as the aging or the current age of the residual current device, a known hysteresis of the core or the core material or component tolerances are taken into account. Only errors that result from a lack of accuracy of the test current, in particular its amplitude, are not taken into account here. Preferably, the accuracy of the test current in the production of the residual current device is set or measured and stored as a value, so that the accuracy can possibly be taken into account in the correction factor. The specification of the components gives the long-term stability of the accuracy of the test current. Typically, there is an allowable range for the correction factor of from 0.8 to 1.25 inclusive.

However, if the detected deviation of the measured value from the nominal value is greater than it may be, taking into account the known influencing variables-in particular taking into account the magnetic hysteresis of the core, the component tolerances and the aging of the fault current protective device-the correction factor will be too great or too small. There is no correction or calibration, but a calibration error condition is detected. This is preferably signaled, for example by means of a light emitting diode. Therefore, it is provided in a preferred embodiment of the residual current device according to the invention, that the control unit is designed so that a calibration error condition is detected when the correction factor is greater than a predetermined maximum allowable correction factor, preferably greater than 1.55, more preferably greater than 2 is. It is likewise provided in a preferred embodiment of the residual current device according to the invention that the control unit is designed such that a calibration error state is detected if the correction factor is less than a predetermined minimum allowable correction factor, preferably less than 0.65, particularly preferably less than zero , 5 is.

If no calibration error state is detected, then the correction factor calculated by the control unit is stored and multiplied at the next due to an error case occurring differential current with the then measured voltage value or current value. The corrected voltage value or current value thus obtained is subsequently used by the control unit to decide whether the differential current is greater than the permissible limit value. If the latter is the case, the at least one phase conductor and the neutral conductor are switched off by means of the control unit. The protective conductor can also be switched off, for example, depending on the embodiment of the residual current protective device and application remain switched on or switched off with respect to the at least one phase conductor and the neutral conductor with a time delay. In order to avoid danger, the at least one phase conductor and the neutral conductor and possibly the protective conductor are switched off analogously even when the calibration error state is detected. It is therefore provided in a preferred embodiment of the residual current device according to the invention, that the residual current device comprises at least one phase conductor switching contact for on and off interruptible interruption of the at least one phase conductor and a neutral switching contact for on and off interruptible neutral conductor, at least one by means of Control unit controllable switching means is provided to switch the switch contacts, and wherein the control unit is designed so that upon detection of the calibration error state, the switch contacts are turned off and / or switching on the switch contacts is prevented.

The switching on and off or the interruption of the at least one phase conductor and the neutral conductor and optionally the protective conductor preferably takes place on the output side. This ensures that the control unit always remains supplied with voltage and work, in particular can control the switching means for switching contacts. That the calibration can be unaffected by a possible fault current through a consumer by the consumer is not supplied with voltage due to the output-side interruption of the at least one phase conductor and the neutral conductor. The switching means may be, for example, relays, i. to act electromechanical switching means, or contactors or controllable power switch with mechanical and / or electronic switching elements, in particular semiconductor switching elements.

In order to exclude a risk to the user as far as possible by means of a fault current device whose sensitivity to the normal state is reduced, it is provided according to the invention that a calibration is carried out at each switch-on operation of the residual current device. The switch-on process is usually initiated by pressing a power-on button by the user. Preferably, the at least one phase conductor and the neutral are not enabled immediately after actuation of the power button and thus possibly supplied to a consumer with voltage, but only after the calibration and only if no calibration error state has been detected.

Therefore, it is provided in a preferred embodiment of the residual current device according to the invention that the control unit is designed so that the calibration of the residual current device at the beginning of each switching of the residual current device, preferably immediately after a power button of the residual current device has been actuated by a user, is performed.

As a result, the switch-on process is typically delayed by a maximum of 200 ms, preferably a maximum of 100 ms. That This period can elapse between the actuation of the power button by the user and the release of the power supply to further terminals of the residual current device, with which further terminals consumers can be electrically connected. Such a period of time is barely perceived by the user and usually not perceived as disturbing.

This in particular also because there are already times for debouncing the power button, which are within the range of the above-mentioned delay times.

In order to further increase safety, it is provided in a preferred embodiment of the residual current device according to the invention that the control unit is designed so that the calibration of the residual current device when the residual current device is switched on, preferably regularly and / or at predetermined time intervals and / or at predeterminable times. This simultaneously represents a function check or function monitoring.

Useful time intervals would be e.g. once an hour or once a week. In order not to interfere with the correct measurement of an externally induced fault current during in-service calibration, an amplitude reduced test current is preferably used. That The respective value of the secondary voltage caused by the reduced test current or of the secondary current caused by the reduced test current is also reduced and is therefore compared with a respectively reduced nominal value. The reduced setpoint values for the secondary voltage or the secondary current are stored in the control unit.

Thus, during the calibration or functional check in a first step, the most accurate possible determination of the externally caused fault current, because the system is not overridden. For this purpose, the reduced setpoint is subtracted from the current measured value and the resulting difference multiplied by the current correction factor. If the result is above the maximum permissible residual current or tripping value, the residual current device triggers. Otherwise, the next step is to check if the current one Correction factor is still valid, and the correction factor may be updated.

Because this measurement takes place during operation, the result can be disturbed by fluctuating fault currents caused by the load. Accordingly, several measurements and a corresponding filtering or averaging can be provided. That the correction factor is then updated not after a single measurement, but after several measurements based on the filtered or averaged value for the correction factor.

In this way, in particular an age-related change in the sensitivity of the residual current device can be taken into account. That The sensitivity of the fault current device can typically change over longer periods of time, even if no high differential currents occur in these periods - and consequently high magnetic fluxes. For example, a strong external magnetic field at the location of the residual current device may result in a change in the magnetic flux density of the core. Furthermore, the temperature can have a significant influence on the core of the differential current transformer, but also on the electrical resistance of the windings, in particular the secondary winding.

In order to provide a secure power supply of electrical equipment even when they are used in different places, especially on construction sites, it is provided in a preferred embodiment of the residual current device according to the invention that it is a portable residual current device. Such a portable residual current device, which is often referred to as PRCD, is connected at the respective construction site with the existing low-voltage network there. By the electrical equipment, in particular power tools such as drills, angle grinder, etc. are then connected only to the PRCD, maximum safety is ensured.

According to the invention a system for the local provision of alternating current is provided for the safe power supply of electrical equipment, especially on construction sites, comprising a residual current device according to the invention, wherein the protective conductor of the residual current device is electrically connected to the protective conductor of the low voltage network, the neutral of the residual current device with the Neutral conductor of the low-voltage network is electrically connected and wherein the at least one phase conductor of the residual current device is electrically connected to the at least one phase conductor of the low-voltage network.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail with reference to an embodiment (s). The drawings are exemplary and are intended to illustrate the inventive idea, but in no way restrict it or even reproduce it.

Showing:

1 a schematic representation of a residual current device according to the invention

2 a schematic representation of another embodiment of the residual current device according to the invention with three phase conductors

WAYS FOR CARRYING OUT THE INVENTION

In the schematic representation of 1 is a residual current device according to the invention 1 for a low voltage grid connected to a single phase low voltage grid. Here is a protective conductor 2 the residual current device 1 connected to a protective conductor PE of the low voltage network, a neutral 4 the residual current device 1 with a neutral N of the low voltage network and a phase conductor 3 the residual current device 1 with a phase conductor L of the low voltage network.

In the protective conductor 2 is a protective conductor switching contact 5 switched to the protective conductor 2 on the output side to be able to interrupt and switch off. Analog is in the phase conductor 3 a phase conductor switching contact 6 switched to the phase conductor 3 on the output side to be able to interrupt and switch off. Likewise, in the neutral 4 a neutral contact 7 switched to the neutral 4 on the output side to be able to interrupt and switch off. The switching contacts 5 . 6 . 7 are with further connections 17 electrically connected, via which electrical equipment or consumers supplied with voltage or with the protective conductor 2 , the phase conductor 3 and the neutral 4 can be electrically connected.

For switching the protective conductor switching contact 5 is a relay 8th provided for switching the phase conductor switching contact 6 a relay 9 and for switching the neutral contact 7 a relay 10 , The relays 8th . 9 . 10 be via a control unit 11 driven by lines 13 is powered (in 1 For reasons of clarity, only one line is shown). In 1 are the wires 13 after the differential current transformer 12 arranged. It should be noted, however, that of course, an arrangement before the differential current transformer 12 it is possible that so the power supply to the control unit 11 even before the differential current transformer 12 can be tapped. The power supply of the control unit 11 over the wires 13 But at least it is independent of the position of the switch 5 . 6 . 7 ,

The control unit 11 has at least one exit 16 for controlling the relays 8th . 9 . 10 on (in 1 For reasons of clarity, only one such exit is shown). Here is the residual current device 1 or the control unit 11 preferably designed so that the protective conductor switching contact 5 independent of the phase conductor switching contact 6 and the neutral contact 7 can be switched. Particularly preferred may also be the switching contacts 6 . 7 be switched independently. In principle, however, embodiments are also conceivable in which the switching contacts 5 . 6 . 7 not independently, but always switched the same, for example, via a common switching bridge, for which then only one relay would be necessary.

For detecting a fault current, the residual current device indicates 1 a summation current transformer or differential current transformer 12 on. The differential current transformer has a primary side with a primary winding 18 and a secondary side with a secondary winding 19 on. The primary winding 18 is in the embodiment shown by a respective portion of the phase conductor 3 and the neutral 4 educated. Furthermore, the differential current transformer comprises 12 a core 21 , which consists of a ferromagnetic, in particular soft magnetic material, typically made of iron or ferrite. In the embodiment shown, the core 21 annular, wherein the primary winding 18 or the corresponding sections of the phase conductor 3 and the neutral 4 through the core 21 are arranged running through. The secondary winding 21 includes a conductor that has several turns around a portion of the core 21 is arranged around.

In normal operation, without the presence of a differential current, the signed sum of all currents is on the primary side or in the primary winding 18 zero. Correspondingly, the magnetic fluxes that rise with the currents in the phase conductor also rise 3 and in neutral 4 are connected in the primary winding 18 on, so no voltage in the secondary winding 19 is induced.

If, on the other hand, there is a current - possibly even a user! - flows to earth, so is the signed sum of all currents in the primary winding 18 nonzero. This means a differential current between the phase conductor 3 and the neutral 4 or between the phase conductor L and the neutral conductor N is present, which in turn with one of the primary winding 18 generated magnetic flux is not equal to zero. Since the considered currents, ie also the differential current, are alternating currents, the magnetic flux caused by the differential current is also variable in time. There is therefore an induction of a secondary voltage in the secondary winding 19 and possibly to a secondary current resulting from the secondary voltage through the secondary winding 19 on the secondary side. The secondary voltage or the secondary current are proportional to the differential current.

The control unit 11 has an entrance 14 to measure for those in the secondary winding 19 induced secondary voltage or for the resulting from the secondary voltage secondary current. When measuring the secondary voltage or the secondary current, due to the induced secondary voltage through the secondary winding 19 flows, it is preferably provided that the control unit 11 amplifies the secondary voltage / secondary current and generates a digital signal by means of an analog-to-digital converter, which is processed and evaluated by means of at least one microprocessor.

In principle, a fault can be detected if the measured secondary voltage or the measured secondary current over a specified, preferably in the control unit 11 adjustable limit is. If such an error is detected, the switching contacts are usually switched off 6 . 7 or remain the switch contacts 6 . 7 switched off. At the secondary connections 17 then no voltage is available. Preferably, the protective conductor switching contact 5 remain switched on or be switched on despite the occurrence of a fault. Of course, it is also conceivable, also the protective conductor switching contact 5 off.

The comparison of the measured values mentioned above with a limit presupposes that a certain differential current actually results in a certain secondary voltage or a certain secondary current, ie that a certain degree of transmission is given. However, the transmission rate can be changed in practice by different factors. In particular, due to a remanence of the nucleus 21 the operating point of the differential current transformer 12 change if the core 21 exposed to large magnetic fluxes, as the core 21 undergoes a magnetic hysteresis. Next play, for example, component tolerances and the aging of the residual current device 1 a role. All these influencing factors can therefore do so cause the sensitivity of the residual current device 1 changes. In particular, if the sensitivity changes so that a differential current, which should actually have a secondary voltage or a secondary current, which lie above the error case defining limits, causing a secondary voltage or a secondary current, which are below these limits, this is represents a great danger to the user. According to the invention, this risk or a changing sensitivity of the fault current device 1 encountered by the control unit 11 for calibrating the residual current device 1 is designed.

For this purpose, the differential current transformer 12 with a well-defined test current, preferably with a sinusoidal test current of precisely defined amplitude, which is typically a tripping value of the residual current device 1 is equal to or within a range of ± 10% around the tripping value, applied to simulate a defined differential current. Typical tripping values are 10 mA, 30 mA or 100 mA. The secondary winding 19 is adjusted accordingly.

The application of the test current is done by means of a test winding 20 in the embodiment shown with at least one turn around a portion of the core 21 is arranged. The test current is from the control unit 11 generated corresponding thereto, preferably controlled by the at least one microprocessor electronics. The control unit controls 11 the test winding 20 via an exit 15 at.

Then the induced secondary voltage or the resulting secondary current by means of the control unit 11 measured and compared with a voltage setpoint or a current setpoint. At a tripping value of 30 mA fault current on the primary side, the secondary voltage induced by a fault current or differential current of 30 mA is typically in the range from 1 mV to 5 mV. Accordingly, the setpoint for the secondary voltage caused by a test current of 30 mA is in this range.

If the measured values deviate from the nominal values, this is done by the control unit 11 calculates a correction factor, which basically results from the quotient of setpoint (dividend) and measured value (divisor). In this way, various known influencing variables, such as the aging or the current age of the residual current device 1 , a known hysteresis behavior of the core 21 or the core material or component tolerances. Typically, the correction factor ranges from 0.8 to 1.25 inclusive.

The calculated correction factor is provided by the control unit 11 stored and subsequently multiplied by the secondary voltage values or secondary current values, which are measured as a result of occurring differential currents. The measured values corrected in this way are now compared with the limit values in order to decide whether an error has occurred or not. In the event of a fault, the switching off of the switching contacts already described above takes place 6 . 7 and possibly the protective conductor switching contact 5 or remain the switch contacts 6 . 7 and possibly the protective conductor switching contact 5 off.

However, it may also be the case that when performing the calibration, the determined deviation of the respective measured value from the desired value is greater than it taking into account the known influencing variables - in particular taking into account the magnetic hysteresis of the core 21 , component tolerances and aging of the residual current device 1 - may be such that the correction factor is too large or too small. This is preferably the case when the correction factor is greater than 1.65, in particular greater than 2 or less than 0.65, in particular less than 0.5. There is then no correction or calibration, but it is from the control unit 11 a calibration error condition is detected.

This is preferably signaled, for example by means of a light emitting diode (not shown). As in the event of a fault due to a too large differential current, the switching off of the switching contacts already described above then takes place 6 . 7 and possibly the protective conductor switching contact 5 or remain the switch contacts 6 . 7 and possibly the protective conductor switching contact 5 off.

To endanger the user by a relation to the normal state disturbed sensitivity of the fault current device 1 exclude as possible, it is provided according to the invention that the calibration of the residual current device 1 at the beginning of each turn-on of the residual current device 1 he follows. It is switched on by the user a power button 22 actuated. The phase conductor 3 and the neutral 4 will not be immediately after pressing the power button 22 unlocked, and thus possibly a consumer, with the continuative connections 17 is electrically connected, but only after the calibration and only if no calibration error condition has been detected. Typically, this means that the switch-on process is delayed by a maximum of 200 ms, preferably a maximum of 100 ms, which is within the range of the time required for debouncing the switch-on button 22 is needed.

Furthermore, the calibration can also during operation, ie with the residual current device switched on 1 be carried out, in particular regularly and / or at predetermined time intervals and / or at predetermined times. At the same time this represents a function check or function monitoring. The control unit 11 can be programmed accordingly to set the times for performing the calibration. Typical time intervals would be once per hour or once a week.

In order not to interfere with the correct measurement of an externally induced fault current during in-service calibration, an amplitude reduced test current is preferably used. This means that the respective value of the secondary voltage caused by the reduced test current or of the secondary current caused by the reduced test current is reduced and is therefore compared with a respectively reduced nominal value. In this case, the reduced setpoint values for the secondary voltage or the secondary current in the control unit 11 deposited. Thus, during the calibration or function monitoring in a first step, the most accurate possible determination of the externally caused fault current, because the system is not overridden. For this purpose, the reduced setpoint is subtracted from the current measured value and the resulting difference multiplied by the current correction factor. If the result is above the maximum permissible residual current or above the tripping value, the residual current device triggers 1 out. Otherwise, the next step is to check whether the current correction factor is still valid, and if necessary, update the correction factor.

Because this measurement takes place during operation, the result can be disturbed by fluctuating fault currents caused by the load. Accordingly, several measurements and a corresponding filtering or averaging can be provided. That the correction factor is then updated not after a single measurement, but after several measurements based on the filtered or averaged value for the correction factor.

2 shows a further embodiment of the residual current device according to the invention 1 for a low voltage network that is completely analogous to in 1 constructed embodiment, wherein the low-voltage network, with which the residual current device 1 is connected, but has three phase conductors L1, L2, L3. Basically, the works in 2 shown embodiment of the residual current device according to the invention 1 completely analogous to the embodiment of 1 , For a detailed description of the functionality or the calibration of the fault current device 1 of the 2 can therefore essentially on the above for residual current device 1 of the 1 Said be directed.

Corresponding to the three phase conductors L1, L2, L3, the residual current device 1 of the 2 also three phase conductors 3 . 3 ' . 3 '' on, which are connected to the phase conductors L1, L2, L3. The primary winding 18 of the differential current transformer 12 is in this case by a section of the phase conductors 3 . 3 ' . 3 '' and the neutral 4 educated. These sections are the phase conductors 3 . 3 ' . 3 '' and the neutral 4 through the annular core 21 arranged extending therethrough.

It is understood that for all three phase conductors 3 . 3 ' . 3 '' associated phase conductor switching contacts 6 . 6 ' . 6 '' are provided. In the embodiment shown are three relays 9 . 9 ' . 9 '' provided to the phase conductor switching contacts 6 . 6 ' . 6 '' to be able to switch. The switching of the individual phase conductor switching contacts 6 . 6 ' . 6 '' can be done independently of each other, or the phase conductor switching contacts 6 . 6 ' . 6 '' are always switched simultaneously.

LIST OF REFERENCE NUMBERS

1

RCD

2

Protective earth of the residual current device

3, 3 ', 3' '

 Phase conductor of the residual current device

4

Neutral of the residual current device

5

Protective conductor switching contact

6, 6 ', 6' '

 Phase conductor switching contact

7

Neutral switch contact

8th

Relay for switching the protective conductor switching contact

9, 9 ', 9' '

 Relay for switching the phase conductor switching contact

10

Relay for switching the neutral contact

11

control unit

12

Differential current transformer

13

Power supply of the control unit

14

Input of the control unit for a secondary voltage and / or a secondary current

15

Output of the control unit for a test current

16

Output of the control unit for controlling the relays

17

Continuing connection

18

primary

19

secondary winding

20

test winding

21

Core of the differential current transformer

22

Power

L, L1, L2, L3

 Phase conductor of the low voltage network

N

Neutral of the low voltage network

PE

Protective conductor of the low voltage network

Claims (8)

Residual current device ( 1 ) comprising a differential current transformer ( 12 ), which is a primary winding ( 18 ) comprising at least one phase conductor ( 3 . 3 ' . 3 '' ) and a neutral ( 4 ) and a core ( 21 ), a secondary winding ( 19 ) and a test winding ( 20 ), with which the differential current transformer ( 12 ) can be acted upon by a test current to simulate a defined differential current, the residual current device ( 1 ) further comprising a control unit ( 11 ), the test winding ( 20 ) to generate the test current and one in the secondary winding ( 19 ) secondary voltage induced and / or secondary current resulting from the induced secondary voltage, characterized in that the control unit ( 11 ) for the calibration of the residual current device ( 1 ) is designed so that when a deviation of the measured voltage value caused by the test current secondary voltage of a voltage setpoint and / or a deviation of the measured current value of the secondary current caused by the test current from a current setpoint, a correction factor is calculated with the measured voltage values of Differential currents caused secondary voltage and / or measured current values of the secondary currents caused by differential currents are multiplied. Residual current device ( 1 ) according to claim 1, characterized in that the control unit ( 11 ) is designed so that a calibration error condition is detected when the correction factor is greater than a predetermined maximum allowable correction factor, preferably greater than 1.55, more preferably greater than 2. Residual current device ( 1 ) according to one of claims 1 to 2, characterized in that the control unit ( 11 ) is designed so that a calibration error condition is detected when the correction factor is less than a predetermined minimum allowable correction factor, preferably less than 0.65, more preferably less than 0.5. Residual current device ( 1 ) according to one of claims 2 to 3, characterized in that the residual current device ( 1 ) at least one phase conductor switching contact ( 6 . 6 ' . 6 '' ) for the interruption of the at least one phase conductor which can be switched on and off ( 3 . 3 ' . 3 '' ) and a neutral contact ( 7 ) for interrupting the neutral conductor ( 4 ), wherein at least one by means of the control unit ( 11 ) controllable switching means ( 9 . 10 ) is provided to the switching contacts ( 6 . 6 ' . 6 '' . 7 ), and wherein the control unit ( 11 ) is designed so that upon detection of the calibration error state, the switching contacts ( 6 . 6 ' . 6 '' . 7 ) are switched off and / or switching on the switching contacts ( 6 . 6 ' . 6 '' . 7 ) is prevented. Residual current device ( 1 ) according to one of claims 1 to 4, characterized in that the control unit ( 11 ) is designed so that the calibration of the residual current device ( 1 ) at the beginning of each switching on of the residual current device ( 1 ), preferably immediately after a power-on button ( 22 ) of the residual current device ( 1 ) has been operated by a user is performed. Residual current device ( 1 ) according to one of claims 1 to 5, characterized in that the control unit ( 11 ) is designed so that the calibration of the residual current device ( 1 ) with the residual current device switched on ( 1 ) takes place, preferably regularly and / or at predetermined time intervals and / or at predeterminable times. Residual current device ( 1 ) according to one of claims 1 to 6, characterized in that it is a portable residual current protective device ( 1 ). System for the local provision of alternating current comprising a residual current device ( 1 ) according to one of claims 1 to 7, wherein a protective conductor ( 2 ) of the residual current device ( 1 ) is electrically connected to a protective conductor (PE) of the low-voltage network, wherein the neutral conductor ( 4 ) of the residual current device ( 1 ) is electrically connected to a neutral conductor (N) of the low-voltage network and wherein the at least one phase conductor ( 3 . 3 ' . 3 '' ) of the residual current device ( 1 ) is electrically connected to at least one phase conductor (L; L1, L2, L3) of the low-voltage network.

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