FR2704686A1 - Method and device for securing an energy distribution point, especially an electrical socket, and electrical appliances including this device - Google Patents

Abstract

Method for securing an electrical energy distribution point, particularly a current socket (1) within an electrical power supply mains (2). The method comprises a first stage in which the output port (3) of the distribution point is isolated from the mains voltage, and comprising a sequence of observation of a load possibly applied to this output port (3), and a second stage in which this output port (3) is connected to the mains voltage, this second stage being activated only when a load of lower impedance than a maximum predetermined impedance is observed. Numerous energy distribution equipment items (sockets, multi-socket boxes (adapters), extensions) can be equipped with safety devices implementing this method. Use in low-voltage electrical apparatus.

Description

 The present invention relates to a method for securing an electrical energy distribution point, in particular an electrical outlet. It also relates to a device for the implementation of this method and electrical equipment including these devices.

 The prevention of domestic accidents is currently a major concern when we note that these domestic accidents constitute the main source of mortality for young children.

Electrocutions represent part of these domestic accidents and manufacturers of electrical equipment have already studied and developed methods to prevent contact with a live part at an electrical outlet. Mention may in particular be made of mechanical processes which obturate the female parts of a socket which is only removed when two male parts are introduced simultaneously. However, these closures can be made inoperative by break-in, in particular by force-entry of a metal part. In this case, it is then possible to come into contact with live internal parts and the socket is no longer secure. In addition, the real safety of a socket outlet fitted with a mechanical safety device is seriously affected when an extension cable is connected to this socket. Indeed, if a child puts in his mouth the free end of the socket, he will be directly subjected to mains voltage since the mechanical safety device will have been normally neutralized by the insertion of the male plug of the extension in the socket current.

 Mention may also be made of safety sockets, the tensioning of which is effective only when a plug with a permanent magnet is inserted.

 It is also customary to associate a switch with a power outlet to control the energization of this outlet, this switch being able to be placed either in the immediate vicinity of the outlet, or at a distance from the latter. However, in the first case, the accessibility of the switch does not guarantee that the socket is switched off; in the second case, it is not possible to avoid the occurrence of an untimely operation of the switch while equipment connected to the outlet is in operation.

 In addition, the differential protections do not detect an electric shock between phases, limited to losses passing through the electrical ground.

 The object of the present invention is to remedy these drawbacks by proposing a method for securing an electrical outlet, which ensures that the outlet is switched off when no equipment is connected thereto while maintaining sufficient flexibility of use.

 According to the invention, the method for securing an electrical energy distribution point, in particular a power outlet, within an electrical supply network delivering a mains voltage, this distribution point comprising an input port connected to said supply network and at least one output port to which electrical equipment to be supplied are connected, is characterized in that it comprises a first step in which the output port is placed without mains voltage and comprising an observation sequence of a load possibly applied to said output port, and a second step in which said output port is placed under mains voltage, this second step being activated only when a load of impedance less than a predetermined maximum impedance is observed.

 Thus, with the method according to the invention, accidental contact of a child's fingers or mouth with the outlet terminals of the socket cannot cause electrocution since these terminals are not subjected to mains voltage during observation sequence. Furthermore, the equivalent impedance of this accidental load is necessarily much greater than a predetermined maximum impedance chosen significantly higher than the highest impedance in the range of loads normally connectable to a power outlet. In addition, the method according to the invention allows individual control of each outlet.

 In a first version of the method according to the invention, during the observation sequence, an amplitude measurement voltage much lower than the mains voltage is applied downstream of said interruption means and the impedance of the load applied to the port output is estimated from the measurement of the current absorbed by said load under said measurement voltage.

 In a second version of the method according to the invention, a leakage current possibly called, upstream of the interrupting means, is detected, through a leakage impedance of said interrupting means, by a load applied to the output port, and this leakage current detection leads to an estimation of the impedance of the load and to a control of the interrupting means as a function of said estimation.

According to another aspect of the invention, there is proposed a security device implementing the method according to 1 invention, characterized in that it is disposed between an electrical power supply network and means for connecting a load to the output. supply, in particular a socket, and in that it comprises switch means, means for estimating the impedance of said load, and means for controlling said switch means, so that the output connection means are not energized only when the estimated load impedance is less than a predetermined maximum impedance.

 In a first configuration of a security device according to the invention, the estimation means comprise means for detecting a leakage current called by a load possibly applied to the output connection means, this detection leading to an estimation of the impedance of said load.

 In a second configuration of a securing device according to the invention, the estimation means comprise means applying downstream of the switching means a measurement voltage d of amplitude much less than the amplitude of the mains voltage, and means for measuring the current absorbed by the load present at the terminals of the socket.

 The method according to the invention can also be implemented in a power outlet connected to an electrical supply network, intended to be housed in a recessing box and comprising a connection device, characterized in that it comprises furthermore a security device according to the invention, disposed between the network and the connection device and housed in the embedding box.

 I1 is also provided a multi-socket device comprising within a housing several sockets and a power cord, characterized in that it further comprises at least one securing device according to the invention. We can consider a configuration in which each socket is associated with a security device electrically disposed between said socket and power lines supported by the power cord.

But we can also consider a configuration using only one safety device for all the sockets.

 The method according to the invention can also be applied to an electric extension cord comprising a power cord at its ends a male plug and a female plug respectively provided with male connection means and female connection means, characterized in that it further includes, either within any of the plugs, or at the power cord, a securing device according to the invention.

 The present invention also takes into account the securing of preexisting sockets. For this, an adapter is provided to secure a pre-existing socket outlet comprising female connection means and connected to an electrical supply network, characterized in that it comprises male connection means intended to be coupled to the means of female connection of the socket, female connection means provided for receiving a male plug of electrical equipment to be supplied, and a securing device according to the invention electrically disposed between the male connection means and the female connection means.

Other features and advantages of the invention will appear in the description below. In the appended drawings given by way of nonlimiting examples:
- Figure 1A is a block diagram of a first embodiment, said downstream, of a security device according to the invention;
- Figure 1B is a block diagram of a second embodiment, said upstream, of a security device according to the invention;
- Figure 2 is a block diagram of an example of an installation grouping together several outlet configurations incorporating a security device according to the invention;
- Figure 3 illustrates a multiple outlet box implementing the method according to the invention;
- Figure 4 is a sectional view of a socket according to the invention arranged in a wall recess;
- Figure 5 shows a pull-out socket implementing the method according to the invention;
- Figure 6 shows a female socket implementing the method according to the invention, at the end of an electrical extension;
- Figure 7 illustrates a particular embodiment of a security device according to the invention; and
FIG. 8 is a timing diagram corresponding to the operation of the device in FIG. 7.

 We will now explain a first embodiment, called downstream, of a securing device according to the invention, with reference to FIG. 1A. A power outlet 1, connected to a power supply network 2, comprises a connection device 3, of conventional structure, and a security device 10 interposed between the network 2 and the connection device 3. This security device comprises a controlled switch 11, of the bipolar type, a measurement unit 100 and a control unit 12.

The measurement unit 100 comprises a device 13 for applying a measurement voltage across the terminals of the connection device and a current measurement device 14, by a shunt resistor. The load resistance is estimated downstream of the switch. The control unit 12 controls the application of the measurement voltage, receives information on the current flowing in the connection device, and controls the switch 11. This control unit 12 is supplied from the network 2, in upstream of the switch 11 at the terminals 15 for connection of the security device 10 to the network 2.

If we consider a first state of the socket in which no acceptable load is detected at the terminals of the connection device 3, the control unit 12 controls the switch 11 in open mode, applies a low level measurement voltage, for example a DC voltage, and receives information indicative of the absorbed current. As long as this current is less than a predetermined minimum value, corresponding to a load impedance greater than a predetermined maximum impedance, the switch 11 is kept open and the connection device 3 is switched off; only a very modest level measurement voltage, for example less than ten volts, is present at the terminals of the socket. At this stage, if the terminals of the socket are connected, accidentally or voluntarily, to a conductive circuit including a region of a human body, the equivalent charge impedance is then necessarily very high, and the absorbed current is then lower at the minimum current value required to close the switch 11. As soon as an impedance lower than the maximum impedance is detected, corresponding for example to the connection of an electrical equipment or to its power-up, the control unit 12 controls the closing of the switch ll and the powering of the socket. When the equipment is disconnected or stopped, the control unit detects the absence of absorbed current and controls the opening of the switch 11.

 In a second embodiment of a security device according to the invention, with reference to FIG. 1B, the device 10 ′, included for example in an electrical outlet 1 ′, connected at 15 to an electrical supply network 2 and located upstream of a connection module 3, comprises a detection unit 16 located upstream of an interrupt unit 11.

The detection unit detects the leakage current called by a load possibly connected to the connection module 3, through the leakage resistors of the interrupting unit 11, and controls via a control circuit 17 the unit d interruption 11 when the detected leakage current is greater than a predetermined value. If the load impedance is greater than a predetermined maximum impedance, the detection unit blocks in the open state the interruption unit 11, which will only be released when a sufficient leakage current has been detected.

 The security device, the general operating principle of which has just been described, can be inserted in numerous characteristic locations of an energy distribution system. Thus, with reference to FIG. 2 which groups together several embodiments of the invention, it is possible to provide fixed power sockets 21, for example in a wall recess, comprising a connection device 211 and a securing device 210 according to the invention. A block 22 of multiple sockets, provided with a cable and a male plug 228 coupled to a female socket 227 connected to the network 2, can also be equipped with security devices 224, 225, 226 associated respectively with sockets 221, 222, 223 It is also possible to design an electrical extension 23 comprising at one or the other of its ends 233, 232 a security device 230, so that, when the extension 23 is connected to a socket 234 connected to the supply network 2, the mains voltage is only present at the other end 232 if a suitable load is actually connected to this end. The method according to the invention can also be implemented in an adapter 24 performing a pull-out socket function and making it possible to secure an ordinary socket 242. The adapter 24 comprises a male connection device 243, a securing device 240 according to the invention, and a female connection device 241 adapted to receive a male plug of an electrical equipment to be supplied (not shown).

A security device 250 according to the invention can also be placed upstream of a sub-network 25 connected to the supply network 2. This may relate, for example, to equipment 251, 252, 253, in particular lighting, equipping a nursery or hospital room. It should also be noted that a securing device 260 can also be mounted at any point of a cord of an extension 26 or of a multi-socket box, using conventional overmolding techniques.

 In an exemplary embodiment of a block of multiple sockets shown in FIG. 3, the block 30 comprises in a now conventional arrangement a plug 32, a power cord 31 and a housing 300, which can be of any shape, for example parallelepipedal or cylindrical example, provided on one of its faces with power outlet 310, 320. With each outlet 310, 320 is associated a security device 31, 32 whose outputs 311, 312; 321, 322 are connected to the input terminals of the corresponding socket 310, 320 and therefore to the female plugs 313, 314; 323, 324, and the inputs of which are connected to the supply wires 33, 34. The connections of the ground plugs 315, 325 of the sockets 310, 320 to the ground wire 35 are not taken into account in the security device according to the invention.

 In the case of a power outlet 49 placed in a recess box 40 inserted in a wall 410, with reference to FIG. 4, it is advantageously possible to insert a security module 41 between the connection device 44 and wires supply 45, 46 connecting the socket to the network via a sheath 42 and connected to the input terminals 400, 401 of the security module 41. The output queues 47, 48 of the latter are connected to the input terminals 402, 403 of the connection device 44. The security device according to the invention can be designed so that it can be housed behind a standard built-in socket.

 If it is desired to secure an ordinary socket without internal modification thereof, with reference to FIG. 5, one can plug into the female connection means 520 of this socket 52 a pull-out socket 50 integrating a securing device 51 according to the The invention between a male connection device 501 comprising male plugs 503, 504, and a female connection device 550.

 In the case of an electrical extension 60 according to the invention, with reference to FIG. 6, this extension 60 comprising at the ends of a power cord 65 a male plug (not shown) and a female plug (63), a security device 61 according to the invention is provided for example upstream of a female connection device 64 included in the female plug 63. The security device 61 is connected at the input to the supply wires 625, 626, and in output to female plugs 627, 628.

 The security device can be produced in many ways, in particular according to economic and space requirements, or even reliability. By way of nonlimiting example of making a securing device illustrated in FIG. 7, a securing device 70, associated with an electrical outlet 3 and connected at the input to a supply network 2, comprises on each line d 'power supply two diodes mounted head to tail 73a, 74a; 73b, 74b and a triac 71a, 71b upstream of the input terminals of the electrical outlet 3. Each pair of diodes performs the function of detecting the presence of a load; each triac assumes the interrupt function, presenting in blocked mode a leakage resistance 75a, 75b. An electronic voltage multiplication device 72a, 72b is connected to the terminals of each pair of diodes 73a, 74a; 73b, 74b. This electronic device 72a, 72b amplifies the voltage VD (t) present at the terminals of the pair of diodes and controls the corresponding triac 71a, 71b. We will now explain the operation of the device 70 with reference to FIG. 8.

 We consider a first state A in which no load is connected to the socket 3. The mains voltage v (t) is actually present at the input of the safety device 70 but is not present at the external terminals of the socket 3. Indeed, due to the absence of a load, no leakage current ia (t) flows in the security device, the detection diodes are therefore not polarized and there is a zero voltage at their terminals. The triacs 71a, 71b receive a blocking command Sa, Sb, for example of low logic level 0.

 If we now consider a state B corresponding to an accidental electrical contact of a child's hand or mouth with the two external terminals of a power outlet, a leakage current effectively settles through the resistors leakage of the triacs, but this leakage current is not sufficient to directly bias the detection diodes and the triacs always remain blocked. Safety is therefore ensured since the child's body will never be subjected to mains voltage. If we now connect an electrical equipment having an impedance Zc lower than the maximum impedance (state C), the leakage current called by the load through the leakage resistors will become sufficient to bias the detection diodes which will then present threshold voltages which are amplified by the amplification devices 72a, 72b generating commands Sa, Sb allowing the conduction of the triacs 71a, 71b. The socket 3 is then energized and supplies the connected equipment. When the latter is disconnected or stopped, the current i (t) in the security device 70 is canceled and the detection diodes are blocked, causing the triacs 71a, 71b to be blocked and the socket 3 to be de-energized.

As a practical and nonlimiting example, the following ranges of resistance values can be cited:
- electrical resistance (measured in direct current) between two conductors each held in one hand: from 80 kQ to 1 MQ;
- electrical resistance (measured in direct current) between two metallic conductors held close to each other, in the mouth: from 30 to 100 kQ;
- highest resistance presented when connecting usual small household appliances (1 W, impedance at 50 Hz: 48 kQ): 3 kQ.

 It can be seen that it is easy to define a safety threshold between the minimum resistance presented by the human body and the maximum resistance of a device when it is connected or started up.

 It should be noted that the security devices used in the invention can either be an integral part of the equipment with which it is associated, for example being overmolded with the other components of this equipment, or be produced in the form of autonomous modules.

 Furthermore, in the case of a multi-outlet box or an electrical extension, it is possible to place the securing device on the power cord, for example by molding this device.

 The controlled switch implemented in a security device according to the invention can be a triac or a relay device.

 Of course, the invention is not limited to the examples which have just been described and numerous modifications can be made to these examples without departing from the scope of the invention.

 Thus, it is possible to envisage many other practical embodiments of the security device according to the invention than that described with reference to FIG. 7.

In particular, it is possible to provide for a current detection, a comparison of the detected current with a predetermined current setpoint and a command of the switch according to the result of this comparison.

 In addition, security devices according to the invention can be placed at numerous points on a network depending on the installations and specific security needs.

 Furthermore, the security method according to the invention can be easily combined with other methods, in particular protection against overloads and short-circuits or differential protection.

Claims (18)

 1. Method for securing an electrical energy distribution point (1), in particular a power outlet, within an electrical supply network (2) delivering a mains voltage, this distribution point (1) comprising a input port connected to said supply network (2) and at least one output port (3) to which electrical equipment to be supplied are connected, characterized in that it comprises a first step in which the output port (3 ) is placed in mains voltage by means of interruption, this first step comprising a sequence of observation of a load possibly applied to said output port (3), and a second step in which said output port (3) is placed under mains voltage, this second step being activated only when a load of impedance (Zc) lower than a predetermined maximum impedance is observed.  2. Method according to claim 1, characterized in that, in said observation sequence, a measurement voltage (u (t)) of amplitude much lower than the mains voltage is applied downstream of said interruption means and in that the impedance (Zc) of the load applied to the output port is estimated from the measurement of the current (i (t)) absorbed by said load under said measurement voltage (u (t)).  3. Method according to claim 1, characterized in that, in said observation sequence, a leakage current possibly called through a leakage impedance (75a, 75b) is detected upstream of the interrupting means (71a, 71b). ) of said interruption means (71a, 71b) by a load applied to the output port, and in that this leakage current detection leads to an estimation of the impedance (Zc) of the load and to a control of the means of interruption (71a, 71b) according to said estimate.  4. Securing device (10, 10 ') implementing the method according to any one of the preceding claims, characterized in that it is arranged between an electrical supply network (2) and means for connecting at the output. a load to be supplied (3), in particular an outlet, and in that it comprises switch means (11), means (100, 16) for estimating the impedance (Zc) of said load, and means (12, 17) for controlling said switch means (11), so that the output connection means (3) are only energized when the estimated impedance (Zc) of the load is less than a maximum impedance predetermined.  5. Device (10 ') according to claim 4, characterized in that the estimation means comprise means (16) for detecting a leakage current called by a load possibly applied to the output connection means, this detection leading an estimate of the impedance of said load.  6. Device (70) according to claim 5, characterized in that the detection means comprise at least one pair of head-to-tail diodes (73a, 74a; 73b, 74b) mounted in series with the interrupting means (71a , 71b), and means (72a, 72b) for amplifying the voltage across said pair of diodes, in order to generate a control signal from said interrupt means (71a, 71b).  7. Device (70) according to claim 6, characterized in that each supply line comprises separate detection means (73a, 74a; 73b, 74b) and separate interruption means (71a, 71b).  8. Device (10) according to claim 4, characterized in that the estimation means comprise means (13) applying downstream of the switching means (722) an amplitude measurement voltage much lower than the amplitude of the mains voltage, and means (14) for measuring the current absorbed by the load present at the terminals of the socket outlet (3).  9. Power outlet comprising means for connection to a power supply network and output connection means for connecting equipment to be supplied, implementing the method according to one of claims 1 to 3, characterized in that 'it further comprises means for interrupting the supply of said output connection means, means for estimating the impedance of the load at the terminals of said output connection means and means for controlling said switch means so that the means of the output connection are only energized when the estimated impedance of the load is less than a predetermined maximum impedance.  10. Power outlet (49) connected to an electrical power supply network (2), designed to be housed in a recessing box (40) and comprising a connection module (44), characterized in that it comprises furthermore a securing device (41) according to any one of claims 5 to 8 electrically disposed between the network (2) and the connection module (44) and housed in the embedding box (40).  11. Multi-outlet device (30) comprising, within a housing (300), several electrical outlets (310, 320) and a power cord (31), characterized in that it also comprises at least one device Securing device (31, 32) according to any one of Claims 5 to 8.  12. Multi-socket device (30) according to claim 11, characterized in that it further comprises, for each socket (310, 320), a securing device (31, 32) according to any one of claims 5 to 8 located upstream of said outlet (310, 320).  13. Multi-socket device according to claim 11, characterized in that it further comprises a single securing device according to any one of claims 5 to 8 for all the sockets.  14. Multi-outlet device according to claim 13, characterized in that the securing device is mounted on the power cable.  15. Extension cord (60) comprising a power cord (65) comprising at its ends a male plug and a female plug (63) respectively provided with male connection means and female connection means (64), characterized in that that it further comprises a securing device (61) according to any one of claims 5 to 8.  16. Extension cable according to claim 15, characterized in that the securing device is arranged in any one of said male or female plugs.  17. Extension cord according to claim 15, characterized in that the securing device is mounted on the power cable.  18. Adapter (50) for securing a pre-existing socket outlet (52) comprising female connection means (520) and connected to an electrical supply network, characterized in that it comprises male connection means (501, 503, 504) designed to be coupled to the female connection means (520) of the socket (52), female connection means (550) provided for receiving a male plug of an electrical equipment to be supplied, and a securing device (51) according to any one of claims 5 to 8 electrically disposed between the male connection means (501) and the female connection means (550).