FR3016250A1 - ELECTRICAL MEASURING DEVICE EQUIPPED WITH AN ELECTRICAL APPARATUS FOR MEASURING THE RESISTANCE OF A GROUNDING OF AN ELECTRICAL INSTALLATION THAT FEEDS THE APPARATUS - Google Patents

Abstract

The invention relates to a device and an electrical measurement method, the device equipping an electrical apparatus (AED) powered by an electrical installation (INS). The device comprises at least: - a first connection (PE) to an earth ground of the masses (Ra) of the installation; a second link (CN) to a neutral conductor (LN); an alternating current generator (GEN); - a control unit (CPU) adapted to: ○ command the generator to inject alternating current on the earth ground of the masses; ○ measuring, between said first and second links, a voltage generated by said injected current; ○ determine a grounding resistance of the masses according to the injected current and the measured voltage; ○ open the switch when the measured resistance exceeds a predetermined threshold.

Description

Electrical measuring device equipping an electrical apparatus for measuring the resistance of an earth electrode of an electrical installation which supplies the apparatus.

TECHNICAL FIELD The invention relates to the field of electrical installations of electrical power distribution networks, and in particular devices for measuring the grounding resistance of the masses of the electrical installation. The invention further provides an electrical measurement method for monitoring the evolution of the earth ground of the masses of the electrical installation and to issue an alert when the grounding resistance of the masses is not more appropriate for the protection of people. State of the art In the interests of electrical safety, in particular for the protection of third parties against indirect electrical contacts (ie electrification or even electrocution of a person) and the preservation of devices in the event of an electrical malfunction, the electrical installations in circuit diagram Ground connections in TT mode have a grounding ground.

Such grounding materializes in its simplest expression by a metal portion which is driven into the ground to ensure an effective electrical connection with the earth (for example in the form of a metal stake planted in the ground or of buried metal cables). Thanks to the intrinsic electrical properties of the earth, the earth electrode is a reference potential within the electrical installation which is used in particular to discharge electric charges of the installation such as the loads of a fault current. By definition, a fault current can be generated by an electrical anomaly in the installation (such as a localized insulation fault, for example). The fault current then flows via the earth electrode and it can be detected by means of protection associated with the earth electrode (such as a residual current circuit breaker (DDR) for example). In a known manner, if the value of the fault current exceeds a determined threshold, the circuit breaker then goes into a "triggered" position (opening of the electrical circuit) to prevent any electrical hazard. The cooperation of the earth electrode and a residual differential circuit breaker thus makes it possible to avoid dangerous elevations of potential of the masses that can be touched by an individual. However, for the protection of equipment of the installation and the users is effective, it is necessary that the ground of the masses is correctly calibrated. As such and to comply with current legislation (standards NFC 15100 or IEC 60364 for example), the electrical resistance of the earthing of the masses must not exceed a well-defined threshold resistance. This threshold resistance is a function of the type of power supply (according to AC current) and the surrounding humidity conditions. By way of example, in France, it is considered that in dry rooms, the maximum voltage during indirect contact with an individual (following an insulation fault in an appliance, for example) must be 50 V in AC, with a fault current of a maximum of 0.5 A (which is usually the value of the rating of the branch differential circuit breaker (NFC 14-100) associated with earth grounding). In fact, the resistance of the earth must not exceed a threshold resistance of 100 Q.

To date, when newly built buildings are ready to be delivered, a check of the grounding resistance of the masses is done beforehand to ensure that the electrical installation complies with the legislation and that offers good electrical protection. However, this prior checking does not make it possible to know the variations in the time of the resistance of the grounding of the masses. However, the value of this resistance is impacted by various parameters which themselves can be caused to fluctuate, such as: - the aging of the material that makes up the earth electrode, - the degradation or even the breakdown of the mechanical connection of the earth electrode with the electrical installation, - the variation of the humidity level (emanating from water damage, for example); and / or electrochemical phenomena at the periphery of the earth electrode. The fluctuations of these parameters may in particular lead to an exceeding of the threshold resistance of the earth electrode (100 S2 to use the above example). Such an overflow makes the electrical installation dangerous, especially for third parties who can therefore be exposed to electrification and / or severe electrocution by exceeding the voltage of 50 V AC. Since these electrical hazards occur especially in the case of electrical appliances with a lack of electrical insulation, there is therefore a need to implement a solution for monitoring the variations in the time of grounding of the masses and the continuity of the connection. from the device to this earth ground, to ensure that the electrical safety of the electrical device is sustainable and that during aging, the device poses no electrical risk to users. Regular monitoring of the grounding can be done using portable devices known to perform a point measurement of earth grounding. For example, there are portable ground control devices that can be wired or electrically connected to an electrical outlet socket to determine a current excess value of the grounding ground, and intrinsically to ensure the continuity of the protective conductor of the socket base used until the earthing of the masses. Indeed, with this type of measurement (possible only in earth connection scheme in TT mode), the resistance obtained during a measurement is a cumulative resistance of the earthing of the masses and the neutral of the transformer. Since the resistance of the ground of the neutral of the transformer is relatively low, it is considered that the measurement of resistance obtained corresponds to a current value by excess of grounding of the masses. According to another example, there are also devices for measuring the grounding which require the disconnection of the earth ground of the masses of the installation and the implantation in the ground of stakes near the grounding of the masses. . The implanted stakes allow current injections and potential measurements to determine the current grounding resistance of the masses.

That being so, these devices are intended to perform only spot checks of the earthing of the masses. They also have the disadvantages of requiring: - the occupation of a socket socket of the installation (requiring in particular possibly disconnect an electrical device to perform the verification), or - binding implementation operations for each measure to be taken (disconnection of the grounding of the electrical installation, which earth connection of the masses is often difficult to access, and establishment of stakes in the ground, which is not always possible for example in urban environment ); and - to reiterate the aforementioned inconveniences with each new measure. There is therefore a need to implement a durable solution for ground measurement of the masses so as to overcome the disadvantages of the state of the art. Moreover, even if these detectors make it possible to ensure punctually that the grounding of an electrical installation is correct, only the portable model, which one plugs on a base of catch, makes it possible to make sure that the Equipment connected to this socket of the installation are well connected to the ground of the masses. Thus, the second detector which requires the disconnection of the earthing of the masses of the installation can not ensure that the connection of the protective conductors of all the socket-outlets of the installation is connected to the earthing of the masses. . However, the power cable and / or the plug of an electrical appliance may be damaged, resulting in possible non-continuity of the protective conductor, which may cause the circuit-breaker to fail and thus create the appearance of a dangerous voltage on an insulation fault of the device. The user is therefore exposed to the risk of electrocution in case of indirect contact with such an electrical device. SUMMARY OF THE INVENTION The present invention improves the situation. The invention proposes in particular to equip a domestic electrical appliance with an electrical measuring device which performs regularly or even continuously measurements of the grounding resistance of the masses for accurate monitoring of its evolution (ie state of the taking of earth of the masses during its aging). The device also verifies the integrity of the protective conductor of the apparatus in connection with the earth ground of the masses. The device and the method proposed are furthermore designed so as to cut off the power supply of the apparatus in the event of a dangerous situation (1) and to alert a user and / or an operator when an electrical risk has been proved from the measured value of grounding of the masses. For this purpose, a first aspect of the invention relates to an electrical measuring device equipping a domestic electrical appliance powered by an electrical installation connected to a general electrical network. The device comprises at least: a first electrical connection to an earth ground of the masses of the installation; a second electrical connection to a neutral conductor of the network; - a regulated and controlled alternating current generator for injecting alternating current on the first electrical connection; A switch for disconnecting the electrical power supply of the electrical apparatus; a control unit suitable for: controlling the generator to inject regulated alternating current into the earth ground of the masses via the first link; O measuring, between the first and second links, a voltage generated by the injected current; determining a grounding resistance of the masses as a function of at least one value of the injected current and a value of the measured voltage for the value of the injected current; O compare the determined resistance with a predetermined threshold; and o open the switch when the measured resistance exceeds the predetermined threshold.

In this case, the voltage generated between the first and second links can be measured: - according to an instantaneous potential difference for peak values of the injected current when the latter is a sinusoidal alternating current, or - according to a true rms voltage (RMS ). In an open position, the bipolar switch opens the single-phase power supply circuit. The electrical apparatus is therefore no longer supplied with electricity. In fact, if this device has an insulation fault, the conductive grounds of this device are no longer powered by the active conductors (phase or neutral), which avoids any risk of electrification or electrocution of an individual with the device in question. By being installed or delivered with the electrical device, the measuring device is thus directly implanted in a fixed manner at the end of the electrical installation. Monitoring the evolution of the connection of the device with the earthing of the masses of the installation makes it possible to ensure that the electrical apparatus is properly connected. This monitoring makes it possible, in particular, to: - monitor the evolution over time of the installation's earth connection, - ensure the integrity of the connection between the electrical device and the earth electrode (typically the integrity of the plug and / or power cable of the device, including the power, neutral and protective conductors). The safety of the user is therefore increased since the device is powered only if the grounding resistance of the masses of the installation protects it from an electrical hazard dangerous to humans (otherwise the power to the device is cut off by the switch which is placed in the open position). Regular measurements (daily or weekly, for example) or continuously can therefore be performed on the earthing of the masses without requiring, at each measurement carried out, installation actions (disconnection of the earth electrode, installation of stakes, etc.), disconnecting the appliance or monopolizing an electrical socket in the installation. Advantageously, the control unit may also be adapted to emit a first warning setpoint when the measured resistance exceeds the predetermined threshold.

The measuring device thus makes it possible to warn of a predetermined threshold overrun. A user or an operator can thus be warned by the alert issued of an inappropriate value of the resistance of the earthing of the masses, which value can lead to a risk situation for users. This risky situation can in particular result in the achievement of a resistance value which causes a tripping circuit breaker only for a fault voltage beyond a threshold of dangerousness to humans. In this situation, in case of indirect contact of the device with the user, the user may be exposed to serious injury or even death. The power failure and the alert generated by the present device thus make it possible to prevent dangerous electrical faults for a user, and to de-energize the apparatus whose grounding is defective. It is understood by indirect contact, a physical contact between an individual and a mass of the electrical device connected to the installation, this mass having been accidentally switched on, for example in the event of an insulation fault. A mass can typically be embodied as a conductive metal portion of electrical equipment or installation that can be energized and touched by an individual. The device thus makes it possible to follow rigorously the variations in the earthing of the masses in time, and the connection of the device to this earth electrode, and to alert a user or an operator as soon as the grounding of the earths masses no longer conform to a safe state (ie resistance within a safe range). With this rigorous monitoring, a quick detection as soon as the defect appears is possible. An intervention can thus be carried out quickly to repair the connection to the earthing of the masses or to check and possibly build a new earth ground and thus reduce its value below the predetermined threshold. The safety range can be based in particular according to the requirements defined by the NFC standards 15-100 and / or IEC 60364. In fact, it is understood that the device guarantees that the electrical safety of the device, the user and of the installation is perennial.

The device is particularly adapted to be installed in a low voltage electrical installation performed according to a ground connection scheme in TT mode.

According to an advantageous embodiment, the device may further comprise an autonomous source of power supply. A power supply can be taken upstream of the bipolar switch to allow the device to recharge the backup battery in case of loss of power to the device and thus continue to operate by generating including a warning set. In addition, when the switch goes to the open position, cutting off the power received by the device, the device issues an alarm. Advantageously, the injected current is regulated in time according to at least a first level of current and a second level of current successively injected, the first and second current levels being distinct. The injection of current according to two distinct levels makes it possible to obtain a more accurate global ohmic measurement value. In fact, by injecting different current levels, the voltage levels generated by these currents make it possible, by differentiating them, not to resist the neutral conductor. The ohmic measurement is therefore more precise, concerning only the grounding resistance of the masses and the resistance of the grounding of the neutral (the latter being very weak or even zero). According to an advantageous embodiment, the device may further comprise a third electrical connection to a phase conductor of the network. The control unit may further be adapted to: o measure a true rms voltage between the second and third links; o compare the true rms voltage with a required voltage range; and o issuing a second alarm instruction when the true rms voltage is not within said required voltage range. In particular, the required voltage range may be between 200 volts and 250 volts. Therefore, the control unit can prevent voltage measurements and issue an alert, in particular to propose an intervention of an operator of the power distribution network to restore a supply voltage expected by the device. The control unit therefore conducts voltage measurements when the electrical conditions allow stable current injections by the generator.

In addition, the device may further comprise a non-volatile memory capable of storing data such as data relating to the predetermined threshold, to the measured voltage, to said measured true rms voltage and / or to the determined resistance.

The data of the predetermined threshold and the values of measured voltages and the determined resistance values are thus stored durably within the device. According to an advantageous embodiment, the resistance compared to the predetermined threshold may be an average grounding resistance value of the masses calculated by the control unit from data stored in the memory. The memory may further be adapted to store data relating to the calculated average resistance value. According to this embodiment, the determined average value can be based on resistance values measured at specific times. This average is a representative value of the state of grounding of the masses over a given period of time. This weighted average makes it possible to integrate any non-homogeneous calculated resistance values due to a possible instability observed in the measurements of the voltages between the neutral conductor and the ground, since the injected current is considered stable if the generator regulates the current under the above-mentioned required voltage range (which may be between 200 volts and 250 volts).

Typically, the average value may be a weighted average of the resistance values measured each hour during a day. The average obtained is therefore representative of the state of grounding of the masses for the day in question. The average value may in particular be compared with the predetermined threshold to determine whether the resistance of the earthing of the masses is, during a given period of time, in a state generally suitable for the installation or requires the emission of an alert to report a dangerous situation. The average value recorded thus makes it possible to have a good representation of the evolution of the grounding of the masses in time, without requiring the processing of a very large number of measured values at each post-processing of the archived data. According to one possible embodiment, the data archived in the device can be time stamped when stored in the memory.

According to this embodiment, the stored and time stamped data can be used in post-processing or by the control unit to establish a history of the measurements and to trace the variations of measured voltages and resistances over time encountered by the earth electrode. masses.

The predetermined threshold may in particular be an electrical resistance value of between 25 and 100 Ω. According to this embodiment, the electrical resistance value can thus be fixed in accordance with the requirements of the NFC 15-100 standard (or the European standard IEC 60364). . Typically, the value of the predetermined threshold is: - for a power grid in France supplying AC power: o 100 S2 when the environment of the low-voltage installation is dry, o 50 S2 when the environment of the installation at low voltage is wet, o 25 S2 when the environment of the low-voltage installation is immersed, - for a power grid in France supplying a DC DC power supply: o 240 S2 when the network environment is dry, o 120 S2 when the network environment is wet, o 60 S2 when the network is submerged. For increased security, the predetermined threshold can be initialized according to is a value slightly lower than the limits prescribed by the standard, such as 5% lower than the above values.

In any case, it should be noted that the value of the predetermined threshold can also be initialized according to a value that may exceed 100 S2 (800 S2 for example in Spain with a branch circuit breaker of I4n 30 mA), provided that this value ohmic does not expose a user to a voltage higher than 50 Volts with a circuit breaker of I4n 500 mA, in case of indirect contact.

According to an advantageous embodiment, the device may further comprise a communication unit transmitting to a remote entity the first and / or the second alert issued.

In this way, the measurement device can issue the alerting instructions to a remote entity such as a management center or a communicating equipment of a user such as a mobile phone (typically a smartphone). Therefore, when a risk situation is detected or the voltage supplied to the device is outside the required range, the instruction is sent directly to the management center or to the user so that a rapid intervention can be implemented. to repair or replace the earthing of the masses, or restore a correct power supply of the device (according to a voltage of about 230 Volts typically). The safety of individuals is thus further improved.

In addition, the communication unit may also be able to transmit, on request, data stored in said memory. Thus, the determined resistance data, the measured voltage data and / or the predetermined threshold value can be transmitted, on request from a remote entity or a user (via an application on his Smartphone for example). This communicated data notably allows the deployment of remote monitoring services of the grounding failures of the device and its power supply. In addition or alternatively, the device may further comprise a local alarm module emitting a signal when one of the first and second alerting instructions is issued.

Typically, the local alarm module may comprise: a loudspeaker emitting an audible signal when the predetermined threshold is detected and / or the device is not powered by a voltage within the required voltage range; and / or a light source such as an LED emitting, for example, a color light signal: green when the grounding resistance of the masses is substantially constant and below the predetermined threshold; o red when a predetermined threshold is exceeded and / or the device is not supplied with a voltage within the required voltage range; and o orange when the grounding resistance of the masses is less than the predetermined threshold but evolves in an increasing slope.

The electrical measuring device may further comprise a display screen displaying the nature of the alert when an alert instruction is issued, or the date and time when this instruction was issued. The display screen can also show the last average resistance and network voltage.

According to a second aspect, the invention relates to a domestic electrical appliance connected to an electrical installation connected to a general electrical network, which installation is provided with a grounding ground, The electrical appliance is connected to the earth electrode of masses and is equipped with an electrical measuring device as described above. According to a third aspect, the invention relates to an electrical measurement method by means of an electrical measuring device equipping a domestic electrical appliance powered by an electrical installation connected to a general electrical network. The method comprises at least the steps of: a) controlled alternating current injection on a ground of the masses of the installation; b) measuring, between the earthing of the masses and a neutral conductor of the network, a voltage generated by the injected current; c) determining a grounding resistance of the masses as a function of at least one value of the injected current and a value of the measured voltage for the value of the injected current; d) comparing the determined resistance with a predetermined threshold; and e) disconnecting a power supply from the electrical apparatus when the measured resistance exceeds the predetermined threshold. Advantageously, the method may further comprise a step of transmitting a first warning setpoint when the measured resistance exceeds the predetermined threshold. According to an advantageous embodiment, the current injection step comprises a regulation of the current in time according to at least a first level of current and a second level of current successively injected, the first and second levels being distinct.

Advantageously, the method may furthermore comprise steps of: measuring a true rms voltage between the neutral conductor and a phase conductor of the network; o comparing the true rms voltage with a required voltage range; and o issuing a second alarm instruction when the true rms voltage is not within the required voltage range. Furthermore, the method may further comprise: a step of initialization of the threshold according to an electrical resistance value and a step of storing data relating to the threshold in a non-volatile memory. In addition or alternatively, the method may further comprise a step of time stamping and storage in the data memory relating to the measured voltage and the determined resistance.

Advantageously, in the comparison step, the resistance compared with the predetermined threshold is an average grounding resistance value of the masses calculated by the control unit from data stored in the memory. In addition, the method may comprise a step of communicating with an entity that is distant from the first and / or the second alert setpoint sent.

According to an advantageous embodiment, the steps a) and b) can be repeated successively according to a first frequency, the step c) can be repeated according to a second frequency, the steps d) and e) can be repeated successively according to a third frequency. In this embodiment, the first, second and third frequencies may respectively be of decreasing frequency value.

Typically, the first frequency may be a so-called high frequency in a regular manner (every 500 ms for example), or even continuously. The second frequency may be a frequency so as to perform regularly (typically every minute or every hour) the weighted average value calculation of the grounding resistance of the masses according to the values of the resistances calculated over the period considered. This weighted average makes it possible to integrate any non-homogeneous calculated resistance values due to a possible instability observed in the measurements of the voltages between the neutral conductor and the ground, since the injected current is considered stable if the generator operates under the range. aforementioned voltage requirement. The third frequency can be a frequency adapted to the monitoring of the evolution of grounding masses over time such as a daily or weekly frequency. This lower frequency can be adapted to calculate the differences between two weighted averages during a day, a week or a month, and to deduce the possible growth of the resistance of the earth electrode on this duration.

According to a fourth aspect, the invention further relates to a computer program for storage in a memory of an electrical measuring device. This computer program includes instructions readable by a processor of a control unit of the device, the processor implementing the method described above when said instructions are executed by the processor. According to a fourth aspect, the invention furthermore relates to a computer program intended to be stored in a memory of an electrical measuring device. This computer program includes instructions readable by a processor of a control unit of the device, the processor implementing the method described above when said instructions are executed by the processor. BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will become apparent upon examination of the detailed description below, and the appended figures in which: FIG. 1 represents an example of an electrical installation which comprises an electrical appliance integrating the electrical measuring device according to the invention; FIG. 2 represents an exemplary embodiment of the electrical measuring device; FIG. 3 is a flow chart showing an example of a succession of steps of the electrical measurement method according to the invention. For the sake of clarity, the dimensions of the various elements shown in these figures are not necessarily in proportion to their actual dimensions. In the figures, identical references correspond to identical elements for the various embodiments shown. DETAILED DESCRIPTION Referring firstly to FIG. 1, on which is illustrated an exemplary embodiment of the electrical measuring device DIS equipping a domestic electrical appliance AED with a low-voltage INS electrical installation connected to a general electrical network RG of FIG. AC three-phase power distribution, 230/400 V, 50 Hz with single-phase connection. This set forms a low voltage electrical system where the DIS device is integrated with the AED apparatus. The AED device is a device operating on a power supply provided by a low voltage domestic RED power grid. Such an appliance may be domestic electrical equipment (refrigerator, washing machine, dryer, etc.) or any other electrical housing equipment (domestic hot water system, radiators, air conditioner, etc.). The panel TE is intended to receive a power supply from a distribution transformer T or other installation of an electric power distributor. The distribution transformer T is here a three-phase star transformer with accessible neutral point, supplying electrical conductors L1, L2, L3 and whose accessible neutral point is connected to the earth ground of the neutral RN used as reference neutral point with the LN neutral electric conductor of the RG network. The power distribution network RG is arranged according to a ground connection scheme in TT mode. Also, the neutral of the distribution transformer T is grounded via the earth ground of the neutral RN and, as detailed below, the masses of the electrical equipment connected to the domestic electrical network RED, such as the apparatus AED, have their own connection to the GRO grounding of the INS installation via the PE conductor. The panel TE is thus connected: to the neutral of the distribution transformer T via a neutral conductor CN connected to the electrical conductor LN; - to its own earth ground Ra via the PE conductor; and via a phase conductor C3 to a conductor of the network RG fed by the transformer T (such as the conductor L3). The power received from the transformer T by the panel TE is then distributed to different branches of the domestic electrical network RED. For this purpose, Table 5 distributes the conductors C3, CN and PE in the domestic network RED to power the electrical devices connected to the latter. A branch circuit breaker DB (typically a residual current circuit breaker (DDR) with a rating of 500 mA, denoted I4n 500 mA respectively) can be arranged upstream of the low-voltage switchboard TE to protect the distribution transformer T, the low-voltage switchboard TE and the RED network in case of failure. The panel TE is arranged at the head of the RED network and makes it possible to feed the various downstream RED power lines securely via circuit breakers D. In this example, the circuit breakers D are organized in the form of 15 rows of circuit breakers. The circuit breakers D may in particular be residual differential circuit breakers (RCDs) calibrated so as to protect against electrical damage to the power lines associated with them (such as an electrical overload or a short circuit). Generally, the circuit breakers of a housing board TE are of a 30 mA rating (i.e. I4n of 30 mA). The electrical lines they protect may consist of the phase conductor C3, the neutral conductor CN and the ground conductor PE. The PE conductor is connected to the earth ground GN of the INS installation. Typically, the grounding of the masses Ra of the INS installation can materialize in the form of: 25 - metal stakes planted in the ground, - metal cables buried in the ground, - metal plates, - concrete reinforcements embedded in the ground, - or other. 30 This earth connection is usually located in the building with the INS facility or nearby.

The power lines downstream of the panel TE are intended to supply the domestic electrical network RED and the electrical equipment (not shown in the figures) connected to it. The equipment is then connected to the neutral via the CN conductor of the corresponding power line, and to the power supply via the conductor C3 and to the ground via the PE conductor of this same line. In order for D circuit breakers to provide the expected protection on associated power lines, and to prevent individuals such as consumers from being exposed to dangerous indirect contacts, the resistance of the earth electrode should not exceed a security threshold value. For example, the NFC 15-100 standard defines that the resistance of the grounding must not exceed 100 S2, if the RED network is in AC supply in dry premises. Through the RED network, the AED apparatus is thus also in connection with: the neutral of the distribution transformer T via a neutral conductor CN connected to the LN conductor; the earth ground of the masses Ra of the INS installation via the PE conductor; and - via the phase conductor C3, to a conductor of the network RG fed by the transformer T (such as the driver L3). In the example shown purely for illustrative purposes, the power received by the AED apparatus is therefore a single-phase power supply. To obtain a three-phase power supply, the AED device can be provided with additional conductors respectively connected to the L1 and L2 conductors via the RED network and the TE switchboard. The AED apparatus integrates the electrical measuring device DIS allowing the monitoring of the earth ground of the masses Ra and the PE link. It should be noted that the AED apparatus may integrate the DIS device in situ or may be equipped with such a device. Since the device AED is equipped with the device DIS, the device AED is arranged in such a way that the device is connected to at least: - the earth ground of the masses Ra via the connection to the conductor PE, - to the CN driver, and - to the driver C3.

The phase and neutral conductors can be crossed in the socket or the junction box that supplies the device. These same conductors can also be crossed in the plug of the power cable or on the terminal block of the device. Also, the DIS device can be provided with an inverter switch that powers the GEN generator. This inverter switch is controlled in a first position by the unit UC if a voltage close to the nominal voltage (230 Volts for example) is measured between the conductors C3 and PE. In the opposite case, the unit UC controls the switch in position 2. It is understood that the device DIS which equips the apparatus can therefore, according to possible embodiments, be installed on the apparatus AED, outside the enclosure of the AED device or close to the device by being connected to the device via a dedicated power line, or arranged as an interface between the RED network and the power supply cable of the device or else arranged on the power cable of the device. In the example shown in FIG. 1, the device DIS is integrated in the apparatus AED, arranged in an intermediate position between the network RED and the terminal block BOR of the apparatus AED. Reference is now made to FIG. an embodiment of the DIS device has been shown.

The device DIS comprises, in particular, connections to the earth ground of the masses Ra, to the neutral conductor LN of the network RG and to a phase conductor L3 of the network RG via electrical connections such as: a PE conductor connected to the tap ground of the masses Ra of the INS installation, - a neutral conductor CN connected to the neutral conductor LN of the network RG; a phase conductor C3 connected to the phase conductor L3. The device DIS further comprises: - a control unit UC; a regulated and controlled current generator GEN; - A switch INT1 bipolar power supply of the AED device; a reversing unipolar switch INT2, which ensures that the phase is well received by the generator GEN as a function of its position (position 1 or position 2); a non-volatile memory MEM; a RAM RAM; a COM communication unit; - a local ALM alarm module; an LED light source (of the electroluminescent diode type); - an HP sound source (speaker type); - an ECR screen; an autonomous BAT power supply (rechargeable battery type or other charge accumulator); - an HMI man-machine interface; and - a CONV AC / DC converter.

The converter is intended to transform the AC power received by the device between the links C3 and CN into DC power supplies for powering the various electrical and electronic components of the DIS device mentioned above (including the unit UC, the screen ECR, GEN generator, etc.). The grounding resistance measurement of the masses can be carried out in particular by means of a ground fault current loop technique consisting in: - injecting, into the earth ground of the masses, alternating current CA in phase with the voltage received via the conductors C3 and CN; and - measuring a voltage generated between the CN and PE conductors by the injected current (by measuring an instantaneous potential difference for peak values of the injected current when the latter is a sinusoidal alternating current, or else by measuring the effective voltage true (RMS)). On the basis of Ohm's law for example, the resistance (Rdet) of earth ground can be determined by the unit UC as a function of the value of the injected current (Lu) and the value of the voltage measured (Urns). For this purpose, the generator GEN is regulated and controlled by the control unit UC to provide a stable alternating current in one or two levels (respectively 1 and 15 mA peak value for example), the alternating current being injected in phase with the power supply received from the C3 and CN conductors. In order for the current injected by the GEN generator to be stable, it must be ensured that the power supplied by the C3 and CN conductors is in accordance with the required supply voltage range. For example, this power range can be between minus ten percent (-10%) and plus six percent (+ 6%) of a nominal voltage of 230 volts. As such, the unit UC can be adapted to measure the RMS value of the supply voltage between the conductors C3 and CN (being connected to an electronic circuit for measuring true RMS voltage connected between drivers C3 and CN for example). Thus, when the potential difference between the conductors C3 and CN is not within the given power supply range (10% / + 6% of 230 volts), the unit UC can prevent voltage measurements and transmit alert (as detailed below). The alert emitted may in particular provide an intervention of an operator of the power distribution network to restore a supply voltage in the required voltage range. If the detected voltage is zero, the alert emitted indicates a power failure. Thus, the unit UC conducts voltage measurements only for a stable current injected by the generator GEN according to at least one regulated level.

The unit UC can also be made to measure the voltage between the CN and PE conductors, generated by the current or currents injected into the PE conductor. The potential difference can in particular be measured according to: - according to an instantaneous potential difference for peak values of the injected current when the latter is a sinusoidal alternating current, or - according to a true rms voltage (RMS). This potential difference or true rms voltage can be measured by the CPU unit via a digital analog converter type device connected to a voltage sensor disposed between the PE and CN conductors. The analog digital converter is driven by the unit.

According to a possible embodiment, the determined resistance (Rdet) is a function of the injected current (4) and a measurement of the instantaneous voltage (Urn ') performed simultaneously with the injection of the current. An excess value of the grounding resistance of the masses Ra is then obtained because the determined resistance (Rdet) therefore includes the grounding resistance of the neutral RN and the neutral conductors LN and CN. In fact, by applying Ohm's law, we obtain: Rdet = RN + LN + CN + Ra = (Urns) / This calculation mode determines a resistance Rdet which is a value of resistance not very precise by excess of the resistance of the grounding of the masses Ra. It has the advantage of having an excess value of grounding Ra which makes it possible to introduce a safety margin (since RN + LN + CN + Ra is of a value greater than the real resistance value of the grounding of the masses Ra). However, it can give rise to false alarms (resistance Ra taken in reality well below the threshold). According to an advantageous variant, the determined resistance (Rdet ') is a function of a current injected according to two distinct levels of AC currents (Irnj), sinusoidal and in phase with the supply voltage of the device DIS received from the conductors C3 and CN. These current levels can be injected into the earth ground of the masses Ra. The measurement of the two levels of instantaneous voltages (Urns) between the CN and PE conductors, which is synchronized with peak values of the two levels of injected currents, makes it possible to deduce the resistance RN + Ra by applying the Ohm's law: Rdet In fact, this differential calculating mode determines a resistance Rd and which is also an excess resistance value of the grounding resistance of the masses Ra. Indeed, it takes into account the resistance of the ground of the neutral RN of the distribution transformer T. However, it has the advantage of subtracting the resistance of LN and CN conductors. The additional resistance RN being relatively small, the value of Ra by excess makes it possible to introduce a reasonable margin of safety (since RN + Ra is only slightly higher than the actual resistance value of the earth ground of the masses Ra ). According to another possible variant, the determined resistance (Rdet-) is also a function of the injected current according to two distinct levels of AC currents (iinj), sinusoidal and in phase with the supply voltage of the device DIS received from the conductors C3 and CN. In addition, an average M (AUmes) N is determined. This average corresponds to the homogeneous values obtained for N instantaneous voltage measurements synchronized with the peak values of the AC currents injections according to two levels. The mean M (AUmes) N also makes it possible to deduce the resistance (RN + Ra) by applying the Ohm law: Rdet "= RN + Ra = M (Umes) N / I Aiinj This differential calculation mode determines a resistance Rdet "which is based on an average of homogeneous values of measured voltages, which values constitute a majority of representative values. This average value makes it possible to avoid taking into account the bad values inherent, for example, of an electrical instability encountered on the LN conductor during the current injections and the associated voltage measurements. Resistance Rdet- is therefore determined more robustly, avoiding nuisance alerts caused by momentary electrical instability during a measurement. According to another possible embodiment, X homogeneous values among Z values of Rdet Rdet 'or Rdec are averaged to obtain a value representative of the resistances measured during a determined duration (during a day for example). It should be noted that the measurement data of the voltages generated by the injected currents can be stored: - temporarily in the random access memory RAM for post-processing such as the calculation of the average M (AU ''s) N ; durably in the nonvolatile MEM memory in order to establish a history of the voltage measurements made between the conductors C3 and CN. The memory MEM is also intended to store the data relating to the value of the threshold resistance not to be exceeded. The memory MEM can also archive the data relating to the resistance values determined by the device DIS. This memory is non-volatile in order to be able to preserve the archived data durably, even in the event of a power failure of the memory. To do this, the unit UC can be adapted to: o control the position of the switch INT2 inverter position 1 if a voltage close to the nominal voltage (230 Volts for example) is measured between the conductors C3 and PE of DIS device and, if not according to the position 2 of the switch INT2; o to command the generator GEN to inject at least one determined current level (or even two distinct current levels) on the earth ground of the masses Ra via the PE conductor, the current being injected in phase or in a constant phase shift with the power received via the CN and C3 conductors; measuring, via the PE and CN conductors, at least one voltage level generated by the current injected into the earth ground of the masses Ra (or even two voltage levels when two different level currents are injected successively); o Determine, via Ohm's law in particular, the sum of the grounding resistance of the masses Ra and the neutral RN (or even the CN and LN conductors in the case of a single voltage measurement synchronized with the value peak of the single current injection) as a function of the injected currents and the measured voltages; o store in RAM for example ten measurements Urns of instantaneous voltage or ten values RN + Ra in memory MEM to calculate the average of the majority of the most representative values taking into account for example the possible instability of the voltage observed on the driver LN during the current injections in the earth ground of the masses Ra; o compare with a predetermined threshold, the determined resistance or the average of the majority of the most representative determined resistances; o open the switch INT1 when the determined resistance or the average of resistances exceeds the predetermined threshold; and o issuing an alarm instruction when the determined resistance or the average of resistances exceeds the predetermined threshold.

The unit UC can send commands to the GEN generator to drive one or two AC current injections on the earth ground of the masses Ra (via the PE conductor). As an illustration, the sinusoidal current injections are in phase with the voltage measured between the conductors C3 and CN at the frequency of 50 Hz and are of a peak value intensity of 1 and 15 mA. When two currents are injected at different levels, the currents can be respectively injected successively at five and three periods.

Preferably, the maximum intensity of the injected AC current is chosen to be lower than the lowest tripping current of the circuit-breakers of the installation (which is typically 30 mA for a circuit-breaker D of the low-voltage switchboard TE) in order to avoid inadvertent tripping of the latter during measurements of the grounding resistance of the masses Ra. It should be noted that it is possible that the measurements cause the tripping of a circuit breaker having an IAn of 30 mA if the circuit considered is already subject to a current of leakage to the ground to which is added that of the measurement . In this case, a search must be made on the installation to repair the faulty equipment. The unit UC may for example comprise an electronic circuit of the microprocessor type, microcontroller, programmable logic circuit (FPGA, PLD or other). As mentioned above, the unit UC can be connected to means known from the state of the art for measuring a potential difference or true rms voltage between the CN and PE conductors on the one hand, and the CN and C3 conductors on the other hand: voltage sensor, analog digital converter or other. Furthermore, the unit UC can be made so as to determine an average of: - voltage values measured and temporarily stored in the RAM; resistance values determined and stored in the MEM memory. The determined resistance values compared with the predetermined threshold may therefore be a function of: an instantaneous voltage measurement between the PE and CN conductors synchronized with the peak value of a stable current injection on the PE conductor; a weighted average of the values of instantaneous voltages measured between the PE and CN conductors synchronized with peak values of stable current injections on the PE conductor; a weighted average of the values of the instantaneous voltages measured between the PE and CN conductors synchronized with peak values of injections according to two distinct levels of stable currents on the PE conductor; a weighted average of the resistance values determined according to one of the three abovementioned techniques. By way of example, for ten instantaneous voltage measurements respectively between the CN and PE conductors which are synchronized with peak values of injected current with a maximum value of 1 mA and six measurements of instantaneous voltages between the CN and PE conductors which are synchronized with the peak value of an injected current with a maximum value of 15 mA, the unit UC determines the weighted average of the absolute values of the ten and six voltage measurements to calculate the difference which remains always positive. From the distance obtained, it is then possible to determine the total resistance of the earths of the masses Ra and the neutral RN by applying Ohm's law with the stable current injected which is of known value (since controlled by the UC unit). Indeed, since the currents injected by the generator GEN are regulated according to stable levels when the power supply received by the device DIS is in the given power supply range (-10% / + 6% of 230 volts), the difference (44) between the levels of stable injected currents is known. Typically, when the unit UC controls a current injection by the generator GEN according to a first level of maximum value of 1 mA and a current injection according to a second maximum level of 15 mA, the unit UC knows the difference of injected current levels (44) which is 14 mA in maximum value. Finally, the unit UC calculates the value RN + Ra then resumes new injections of currents and voltage measurements in order to obtain new values of RN + Ra. The unit UC can perform the voltage measurements, determine the earth resistance values of the masses Ra by excess and compare the determined resistance values with the predetermined threshold at different frequencies (in particular according to the three frequencies described above. before). The second and third frequencies can be parameterized by the consumer or by an operator via the device's HMI interface, which notably comprises setting buttons. The values of these frequencies may furthermore be stored in the MEM memory of the DIS device.

In addition, the generator GEN and the unit UC may be provided to detect that the current injected into the ground of the masses by the generator is zero. In this case, the electrical connection of the device or electrical panel TE may have been broken (dangerous situation for the user). The unit UC can then issue an alert for rapid intervention to be performed in order to restore the earth connection of the device masses and the table TE if necessary. In addition, the unit UC may comprise a calendar and an internal clock that allow time stamping the data relating to the measured voltages and to the determined resistance. Thus, the archived data make it possible to establish a history of measurements making it possible to establish the variations in time of the measured voltages (between the CN and PE conductors, and between the conductors C3 and CN) and the resistance of the earth electrode. Ra masses by excess. The unit UC can consult the measurement data stored in the memory MEM. From the data consulted, the unit UC can calculate a daily, monthly or even annual average value of the grounding resistance of the masses Ra (by excess). This average can also be stored in the memory MEM in order to give an overall representation of the state of the grounding of the masses Ra by excess over a given period. This average can for example be displayed on the ECR screen or transmitted to the user via the COM unit.

When the INT1 switch is placed in the open position by the CPU unit, the circuit that supplies the terminal block BOR is open which cuts off the power received by the AED device. When the power disappears on the conductors C3 and CN, the autonomous source BAT takes over so as to supply the converter CONV according to a power supply enabling to send an alarm setpoint to the alarm module ALM and to the communication module COM .

The BAT stand-alone power source can be a Lithium-ion battery type or a capacitor that is permanently charged by the power supply as long as it is present on the C3 and CN conductors. The device DIS then warns the user when a risk situation is detected by one or more measurements of the grounding of masses Ra by excess. This risky situation is reflected in particular by the cutting of the power supply of the apparatus (opening of the switch) and the issuance of an alarm instruction when the resistance of the earth ground of masses Ra by excess and the PE bond is too high (greater than 100 S2 for example). The user can be warned by means of different means emitting an alarm signal upon receipt of the alert instruction. The alarm signal can in particular be emitted by: the local alarm module ALM which can be embodied by the loudspeaker HP (emission of a particular sound signal) and / or the light source LED (passage of a green light (if the grounding value of the masses Ra is constant and less than 100 S2) to a red light (if the grounding value of the masses exceeds 100 S2) .The LED source displays an orange light if the grounding value of the masses Ra is increasing but below the threshold, - the ECR screen (display of an alert message with the measured value) and / or - a remote entity which has received a notification of alert via the COM unit The ECR screen (which can be an LCD screen typically) can display various information such as: - the nature of the alert (exceeding the resistance threshold, non-standard network voltage, power failure, etc.), - the date and time of the measurement of the grounding of the masses or the mains voltage having generated the warning, - a preventive message for carrying out a control of the grounding of the masses Ra, - a request for intervention (which may be sent via the COM unit) to a repairer for verification or repair of the grounding of the masses Ra; - an intervention request (which can be sent via the COM unit) to a service provider to measure the voltage and call on the network operator to carry out a distributed voltage adjustment if necessary.

The user is therefore warned locally of a dangerous situation by the light signal emitted by the LED source, by the sound signal emitted by the speaker HP or by the information displayed on the screen of the DIS device. An acknowledgment button (present on the HMI interface for example) allows you to suppress the audible alarm.

The user can also be remotely notified by receiving a notification sent by the COM unit on receipt of the alert instruction. This notification can be sent to the user via a web page, an e-mail message or a user's phone application. The COM unit may also receive a notification from a remote entity such as the mobile phone of the user, for example to acknowledge an alert. The COM unit may be a radio frequency communication module of Wi-Fi, Bluetooth, GSM or other module capable of transmitting data over the air to a remote entity (not shown in the figures). The unit COM allows in particular to issue instructions or alert notifications to a remote entity such as a management center or a communicating equipment of a user. Furthermore, upon request from a remote entity, the COM unit can access the data stored in the memory MEM and transmit it to the requesting entity. Thus, the requesting entity can exploit the transmitted data to know the precise variations over time of the resistance of the earth ground Ra or the network voltage. The interface HMI (which can materialize in particular in the form of buttons accessible to the user on the device DIS) can be adapted so as to be able to: - parameterize the device DIS (initialization of the predetermined resistance threshold: 25, 50, 95 or 100 S2, and more for example, choice of time intervals between each control of earth ground of masses, entry of the GSM number for transmission of the alarms, etc.), - acknowledge the audible and / or luminous alarm, - navigate the information displayed on the ECR screen.

Once set, the predetermined threshold and the choice of time intervals between each resistance measurement are stored in the MEM memory of the DIS device. Using the IIHM interface, it is also possible to update the CPU's calendar and clock and access the data stored in the MEM memory. A user can thus display on the ECR screen a representation of the variations in time of the network voltage and the resistance of the earth ground of the masses Ra (in the form of a graph for example). This history makes it possible, for example, via a smartphone of the user for example, to represent a curve of the evolution of the voltages measured by the device and the evolution of the grounding of the masses Ra. This representation can allow the user to have a quick overview and a regular monitoring of the data measured and calculated by the device. The voltage monitoring provided to the device may enable the user to provide evidence to the energy distributor if the distributed voltage does not comply with the required voltage range (-10% / + 6% with respect to a nominal voltage 230 Volts). In addition, the memory MEM is adapted to store a computer program comprising instructions readable by a processor of the unit UC. The processor can also implement the method described below in the light of FIG. 3, and this when the instructions of the program are executed by this processor. Referring now to Figure 3 in which there is shown an exemplary flow chart comprising steps of the electrical measurement method implemented via the DIS device.

In a first INIT step, the installer of the device or the user can adjust or update the value of the predetermined resistance threshold. It can also determine the time interval chosen between the different current injections or between two groups of several measurements (group of ten measurements, for example) of the grounding resistance of the masses Ra.

According to a step M, the data of the predetermined threshold and / or time intervals chosen and initialized in the INIT step are stored in the memory MEM.

According to step Ti, the unit UC can compare the supply voltage of the device DIS (supplied by the conductors C3 and CN) with a given nominal voltage range (between -10% and + 6% of 230 Volts per second). example), a range corresponding to the expected requirements of the operator of the energy network and makes the generator GEN work properly. If the supply voltage is not included in this range (arrow N at the output of step Ti), then an ALERT1 step provides for the issuance of an alarm instruction indicating that the measurements of the earth masses can not be achieved and the nominal voltage is not respected. This alert can in particular propose to control the network voltage and to involve an operator of the power distribution network to regularize the situation and reduce the voltage in the power range expected by the DIS device. If the ALERT1 step is triggered, a validation of an operator (via an acknowledgment button on the HMI of the DIS device or via a command received via the COM module) may be required to acknowledge the acknowledgment. alarm (especially local). Next, a restart of the flow chart can only be performed by a specific button on the HMI of the DIS device or by a command received via the COM module and this to reiterate the step T 1. The following steps of the method are therefore performed only when the received power supply makes it possible to obtain current injections in one or two stable and regulated levels, which subsequently makes it possible to calculate the grounding resistance of the masses Ra excessively depending on a single unknown, the value of the instantaneous voltage measured between the CN and PE conductors generated by the injected stable current (which voltage can however be disturbed during the measurement by variations of the neutral voltage, as this has been already quoted earlier in the text). On the other hand, if the supply voltage is correct at step Ti (included in the range -10% / + 6% with respect to the nominal voltage of 230 Volts), then the unit UC proceeds to a step A ( arrow O at the output of step Ti). Prior to step A, the voltage between the conductors C3 and PE can be measured. If the measured voltage is close to the nominal voltage of 230 volts, then the unit UC controls the switch INT2 inverter in position 1. In the opposite case, the unit UC controls the switch INT2 inverter in position 2. Thus, it is ensured that the generator GEN receives well the phase of the supply provided by the RED network. According to step A, the unit UC controls the current generator GEN to inject alternating current AC (4) (according to two distinct and successive sinusoidal levels for example) in phase with the supply voltage of the device DIS. These currents are injected into the earth ground of the masses Ra. According to one possible embodiment, an additional verification step may be performed (not shown in the figures), in which it is verified that the current injected into the earth ground of the masses is not zero. If necessary, an alarm instruction can be issued so that the ground connection of the device masses and the TE panel is controlled and repaired if necessary by a specialist. According to a step B, the unit UC then measures the voltage, i.e. the instantaneous voltage (Urn ') generated or the generated true rms voltage (Urn'), between the CN and PE conductors by the injected current (Int).

According to a MRAM step, the data relating to the measured voltage values are temporarily stored in the RAM memory (which serves as a working memory for calculating the average of the voltages measured during a step C). The steps A, B and MRAM can be repeated according to a determined frequency, for example every second to proceed to at least: a given number of successive current injections and in phase with the supply voltage on the earth electrode Ra masses (sixteen injections for example, ten at a first level of current and six at a second level of current, stably injected over a period of 160 ms), - a determined number of instantaneous voltage measurements synchronized with the peak values of the injections of currents which generated them (typically, sixteen corresponding measurements over a period of 160 ms), storage of the measured voltage values in the RAM memory. According to step C, the unit UC determines the grounding resistance of the masses as a function of the injected current and the measured potential difference. To do this, the CPU can extract the temporarily stored data into the RAM. The resistance can in particular be calculated on the basis of the resistors Rdet, Rdet 'OR Rdet- described above.

According to a step MI-I, the data relating to the determined resistance values (Rclet, Rclef or Rdet-) are archived and timestamped in the memory MEM. At this step, the unit UC can further store and time stamp the averages calculated by the unit UC in the memory MEM for post-processing.

The steps C and MI-I may be repeated successively every minute or hour typically so as to determine a grounding resistance of the masses according to a weighted average of the resistance measurements already stored in the memory. According to a step T2, the unit UC compares the determined value of the grounding resistance of the masses (Rde, Rdet 'or Rclet' '), or the weighted average of this resistance, with the value of the predetermined threshold. For this comparison, the unit UC extracts from the memory MEM the necessary values. If the resistance or the weighted resistance average does not exceed the predetermined threshold value (arrow N at the output of step T2), the process terminates (step 15 END). On the other hand, if the value or the weighted average of resistance exceeds the value of the predetermined threshold (arrow O at the output of step T2), then a step OUV provides for cutting off the power supply of the apparatus AED by controlling the passage switch INT1 in an open position. Next, an ALERT2 step consists in emitting an alarm instruction when the measured resistance exceeds the predetermined threshold in order to warn the user or an operator of a fault occurring at the device or the earth electrode. Since the apparatus is no longer powered, there is no risk of electrocution of the user in the event of indirect contact with the apparatus having an improper earth ground. The step T2 (and the step ALERT2 if necessary) can be repeated at a frequency adapted to the monitoring of the evolution of earth ground masses over time such as a daily or weekly frequency. This lower frequency can be adapted to regularly calculate a weighted average of the resistances determined during a day, a week or a month, and to deduce a global value representative of the state of the taking. over this period.

The process can remain stuck in the ALERT2 step until an operator intervention has been performed (validation by acknowledgment button or remote command), then go to the END step once the Grounding safety has been verified and validated by a second local or remote action. This embodiment makes it possible to restart the measurement cycle of the grounding of the masses Ra in safe electrical conditions. Following the step END, the steps of the flowchart can be successively repeated to perform a new measurement of the grounding resistance of the masses Ra.

At any time during the execution of the process, if the supply voltage disappears from the conductors C3 and CN at the input of the device DIS then the unit UC issues an alert requesting an intervention on the installation so as to verify fuses or power circuit breaker. The reappearance of the supply voltage on the conductors C3 and CN then restarts the process in step Ti.

In addition to the ALERT1 and ALERT2 steps, communication steps (not shown in the figure) of the alert setpoint to a remote entity can be implemented. In addition, in addition to the steps M, MIRAM and MI1, steps for calculating the earth ground deviation of the masses (not shown in the figure) can also be implemented to control, for example, the orange LED source of the DIS device. and generating an alerting instruction to a remote entity in the event of grounding of the masses lower than the predetermined threshold but of increasing value over time. Furthermore, another step may consist in transmitting, on request, to a remote entity the data stored in the memory MEM in steps M and MIL. Also, in view of the foregoing, it should be noted that the device and the method proposed provide continuous near-real-time monitoring of the ohmic value of the grounding of the excess masses Ra and the PE conductor, as well as their possible drift over time with respect to the threshold which may be 100 S2 (or more ) or slightly lower than the limit value (95 S2 for example).

The predetermined threshold may be of an electrical resistance value set in accordance with the requirements of the NFC standards 15-100 and / or IEC 60364, such that: - for a power grid in France supplying a power supply AC: o 100 S2 when the network environment is dry, o 50 S2 when the network environment is wet, o 25 S2 when the network is submerged, - for a power grid in France supplying DC power: o 240 S2 when the network environment is dry , o 120 S2 when the environment of the network is wet, o 60 S2 when the network is immersed, For an increased security, the predetermined threshold can be set to a value slightly lower than the prescribed limits, for example 5% lower than the above values . The device and the method thus provide protection to users against indirect contact that is dangerous for humans, which device is in continuous operation, with continuous or at least regular measurements (and this without the need for any constraining steps). installation as in the prior art).

The device thus significantly improves the security of property and people, can also serve as a platform for the implementation of electrical safety services in housing and intervention request for repair of the grounding of the masses and / or the connection of the device to this ground. The invention has been described with reference to particular embodiments that are not limiting. Of course, the present invention is not limited to the embodiment described by way of example and extends to other variants. For example, the device can be integrated into a device as soon as it is manufactured or can be mounted on an existing device, the device then being connected to a dedicated electrical connection connected to the installation to which the device is connected.

Claims (8)

REVENDICATIONS1. Electrical measuring device (DIS) fitted to a domestic electrical appliance (AED) powered by an electrical installation (INS) connected to a general electrical network (RG), said device comprising at least: - a first electrical connection (PE) to a socket earth ground (Ra) of said installation (INS); a second electrical link (CN) to a neutral conductor (LN) of said network (RG); - an alternating current generator (GEN) regulated and controlled to inject alternating current on said first electrical connection (PE); - a switch (INT1) of power supply cutoff of said electrical device (AED); - A control unit (UC) adapted to: o control said generator (GEN) to inject regulated alternating current on said earth ground (Ra) via said first link (PE); o measuring, between said first (PE) and second (CN) links, a voltage generated by said injected current; o determining a grounding resistance of the masses as a function of at least one value of the injected current and a value of the measured voltage for said value of the injected current; o comparing said determined resistance with a predetermined threshold; and o open the switch when the measured resistance exceeds the predetermined threshold. 2. The electrical measuring device according to claim 1, wherein said control unit is further adapted to emit a first warning setpoint when said measured resistance exceeds said predetermined threshold. 3. Electrical measuring device according to one of claims 1 or 2, further comprising an autonomous source (BAT) power supply. 4. Electrical measuring device according to one of the preceding claims, wherein said injected current is regulated in time according to at least a first level of current and a second level of current injected successively, the first and second current levels being separate. . Electrical measuring device according to one of the preceding claims, further comprising a third electrical connection (C3) to a phase conductor (L3) of said network (RG), in which the control unit (UC) is in further adapted to: o measuring a true rms voltage between said second (CN) and third (C3) links; o comparing said true rms voltage with a required voltage range; and o emitting a second alarm instruction when said true rms voltage is not within said required voltage range. An electrical measuring device according to claim 5, wherein said required voltage range is between 200 volts and 250 volts. 7. Electrical measuring device according to one of the preceding claims, further comprising a non-volatile memory (MEM) capable of storing data relating to at least: - said predetermined threshold; at said measured voltage; at said measured true effective voltage; and / or - at said determined resistance. An electrical measurement device according to claim 7, wherein said resistance compared to said predetermined threshold is a weighted average grounding resistance value of masses calculated by the control unit (UC) from data stored in the memory (MEM) .Electric measuring device according to one of claims 7 or 8, wherein the data stored in said memory (MEM) are time stamped. Electrical measuring device according to one of the preceding claims, wherein the predetermined threshold is of an electrical resistance value of between 25 and 100 Q Electrical measuring device according to one of the preceding claims, further comprising a communication unit (COM) transmitting to a remote entity the first and / or second alert issued. Electrical measuring device according to claim 11, wherein the communication unit is further able to transmit, on request, data stored in said memory (MEM). An electrical measurement device according to one of the preceding claims, further comprising a local alarm module (ALM) transmitting a signal when one of the first and second alerting instructions is issued. Domestic electrical appliance (AED) connected to an electrical installation (INS) connected to a general electrical network (RG), which installation is provided with a grounding ground (Ra), said electrical apparatus (AED) being connected to said earth ground and being equipped with an electrical measuring device (DIS) according to one of the preceding claims. 15. A method of electrical measurement via an electrical measuring device equipping a domestic electrical appliance (AED) supplied by an electrical installation (INS) connected to a general electrical network (RG), said method comprising at least the steps of: a) controlled alternating current (A) injection on a grounding ground (Ra) of said installation (INS); 9. 10. 11. 12. 13. 14.b) measuring, between the earthing of the masses (Ra) and a neutral conductor (LN) of said network (RG), a voltage generated by said injected current; c) determining (C) a grounding resistance of the masses as a function of at least one value of the injected current and a value of the measured voltage for said value of the injected current; d) comparing (T2) said determined resistance with a predetermined threshold; and e) disconnecting (OV) an electrical supply of said electrical apparatus (AED) when the measured resistance exceeds said predetermined threshold. 16. The electrical measurement method according to claim 15, further comprising a step (ALERT2) for transmitting a first warning setpoint when the measured resistance exceeds said predetermined threshold. 17. An electrical measurement method according to one of claims 15 or 16, wherein said current injection step (A) comprises a regulation of the current in time according to at least a first current level and a second current level. injected successively, the first and second levels being distinct. 18. An electrical measurement method according to one of claims 15 to 17, further comprising steps of: measuring a true rms voltage between said neutral conductor (LN) and a phase conductor (L3) of said network ( RG); o comparing (T1) said true rms voltage with a required voltage range; and o issuing a second alarm instruction (ALERT1) when said true rms voltage is not within said required voltage range. 19. Electrical measurement method according to one of claims 15 to 18, further comprising: - an initialization step (INIT) of said threshold according to an electrical resistance value and - a data storage step (M) relating to said auditing threshold in a non-volatile memory (MEM). 20. The electrical measurement method according to claim 19, further comprising a step of timestamping and storing (1 \ 41-1) in said memory (MEM) data relating to said measured voltage and to said determined resistor. The electrical measurement method according to claim 20, wherein in the comparing step (T2), said resistance compared to said predetermined threshold is an average grounding resistance value of the masses calculated from data stored in the memory (SAME). 22. The electrical measurement method according to one of claims 15 to 21, further comprising a step of communicating to an entity remote from the first and / or second alert issued. 23. Electrical measurement method according to one of claims 15 to 22, wherein: - steps a) and b) are repeated successively at a first frequency; step c) is repeated according to a second frequency; steps d) and e) are successively repeated according to a third frequency; and wherein the first, second and third frequencies are respectively of decreasing frequency value. 24. Computer program intended to be stored in a memory of an electrical measuring device, which computer program comprises instructions readable by a processor of a control unit of said device, said processor implementing the method according to one of the claims 15 to 23 when said instructions are executed by said processor.