Combined device for electrical protection against transient overvoltages and monitoring of an electrical installation

Abstract

The present invention refers to a combined device for electrical protection against transient overvoltages and monitoring of an electrical installation, of those used in installations with alternating single-phase or multi-phase current, or direct current, of those formed by cartridges plugged in to a fixed base or formed by a monoblock, both types of devices comprising one or more components for overvoltage protection in each plug-in cartridge or in the monoblock, characterised in that it comprises monitoring means configured so that they continuously measure and process one or several parameters related to the state of the electrical installation and the protective device itself, and connected to said monitoring means a series of indication means configured to indicate one or a combination of output parameters are comprised.

Claims

1. A combined device for electrical protection against transient overvoltages and monitoring of an electrical installation, as used in single-phase or multi-phase alternating voltage installations, which is formed by cartridges plugged to a fixed base or that is formed by a monoblock, comprising: a minimum of one protection group formed by one or more protective components protecting against transient overvoltages in each plug-in cartridge or in the monoblock, the one or more protective components being a varistor(s), gas arrester(s), gas discharge tube(s), spark gap(s), suppressor diode(s), triac(s), thyristor(s), and/or MOSFET(s); means of monitoring configured to permanently measure and process one or several parameters in relation to the condition of the electrical installation and the one or more protective components; and means of indication connected to said means of monitoring and set up in such a way as to indicate the following output parameter: If an earth resistance value (R.sub.PE) measured by the means of monitoring is inside or outside of certain predetermined limits or margins R.sub.PEMINand R.sub.PEmax; wherein the earth resistance value R.sub.PE measured by the means of monitoring is based on the injection of current impulses to earth via a PE terminal using a phase to earth loop and these impulses are of high enough intensity to determine the increase in voltage caused by the injected impulses with regard to voltage in an earth system, but without triggering a possible residual current circuit device(s) (RCD) which is/are installed in the electrical installation, or causing a malfunction of the residual current circuit device(s) in the long term; wherein the means of monitoring uses a dynamic method to control an angle of injection of the current impulses, depending on the AC supply voltage, and/or resistance of the earth system R.sub.PE, and/or the stability of the R.sub.PE measurement made; and further wherein the means of indication is setup to optionally indicate one or a combination of the following parameters: If the wiring of the combined device to the electrical installation comprising a line conductor (L), a neutral conductor (N), and a protective conductor (PE) or protected earth neutral conductor (PEN) is correct; If a supply voltage of an alternating network (v.sub.L) falls within predetermined normal limits such that v.sub.L is between v.sub.Lmin and v.sub.Lmax, wherein v.sub.Lmin and v.sub.Lmax represent a lower supply voltage limit and an upper supply voltage limit, respectively; If an earthing system voltage (v.sub.PE) is greater than or equal to an earthing system threshold voltage (v.sub.PEmax).

2. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the output parameters of the means of indication comprise an indication of whether at least one of the protective component(s) that is integrated into the combined device has reached the end of its useful life.

3. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein it is formed by a set of one or more cartridge(s) inserted in a fixed base, in which each cartridge comprises the one or more protective components, and inside at least one of the cartridges there are the means of monitoring, and the means of indication.

4. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein it is formed by one monoblock, which comprises the one or more protective components, and which has inside the means of monitoring, and the means of indication.

5. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the means of indication are configured by a first type of indicator and a second type of indicator, wherein: the first type of indicator is activated in different manners of indication for providing information about whether the connection to the mains is incorrect and/or voltage v.sub.PE?v.sub.PEmax and/or mains voltage (v.sub.L) meets the condition of v.sub.Lmin>v.sub.L>v.sub.Lmax; when all of the aforesaid is correct, the first type of indicator issues a corresponding indication in accordance with the R.sub.PE value obtained within the predetermined margins; the second type of indicator issues an indication, lighted or not, if the protective component(s) included in the cartridge or in the monoblock in which the said second indicator is located has reached the end of its useful life.

6. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the means of indication are configured by a first type of indicator, wherein: the first type of indicator is activated in different manners of indication to provide information about whether the mains connection is incorrect and/or voltage v.sub.PE?v.sub.PEmax and/or mains voltage (v.sub.L) meets the condition of v.sub.Lmin>v.sub.L>v.sub.Lmax; when all of the aforesaid is correct, the first type of indicator issues a corresponding indication in accordance with the R.sub.PE value obtained within the predetermined margins.

7. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 6, wherein the first type of indicator also gives another additional indication, when the protective component(s) included in the cartridge where said first indicator is located reaches the end of its useful life.

8. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein it comprises means for disconnecting from the supply voltage at least one of the protective component group(s) that are built into the protective device.

9. The combined device for protection against transient surges and monitoring of an electrical installation, according to claim 1, wherein it comprises certain means of wireless and/or cable transmission or communication of the measured parameters processed by the means of monitoring to another combined device(s) or another type of device(s) inside or outside of the place where the combined device is installed.

10. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the means of monitoring and means of indication are integrated into an electronic circuit.

11. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 10, wherein the electronic circuit is totally or partially integrated in one of the cartridges that form the combined device of plug-in cartridges type.

12. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the value of the resistance of the earth system (R.sub.PE) is obtained by determining the increase in voltage caused by the current impulses injected over the existing voltage in the earth system.

13. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the preferred values of an impulse duration (T.sub.imp) are comprised between 200 ?s<T.sub.imp<300 ?s.

14. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 10, wherein the electronic circuit comprises at least: An AC/DC converter, which supplies a DC voltage (V.sup.+) with respect to a common circuit point (GND), which is connected to the N terminal of the cartridge; A controller, which is supplied by the voltage V.sup.+; and Two adapters, which also are supplied by the voltage V.sup.+; the output voltage of these adapters, v.sub.1(t) and v.sub.2(t) respectively, supply a DC voltage to the controller, normally V.sup.+/2, to obtain a maximum dynamic range and superimposed AC voltage proportional to respective input voltages, wherein v.sub.1(t)=V.sup.+/2+k.sub.1 v.sub.L (t) and v.sub.2(t)=V.sup.+/2+k.sub.2 v.sub.PE (t), and wherein k1 and k2 each represent a gain or an attenuation.

15. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the current impulses are injected between an angle of ??90? and ?150? in relation to the positive half cycle of the supply voltage wherein a specific number of pulses are grouped in bursts.

16. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 15, wherein the decision criterion to adjust the injection angle ? in each half cycle of a burst based on the voltage value v.sub.L (?=90?) is preferably modified in accordance with the R.sub.PE value obtained for the previous burst, so that as the R.sub.PE increases, the ? value progressively increases to further decrease the current and vice versa.

17. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 15, wherein the resistance of the earth system (R.sub.PE) is determined for a burst, by averaging the R.sub.PE values measured for each impulse of the burst.

18. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 17, wherein the average R.sub.PE value obtained for several previous bursts is used to make the system more stable.

19. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 15, wherein the injected current is reduced by reducing a number of impulses per burst, as long as the R.sub.PE stability is good, maintaining an impulse width (T.sub.imp) as well as a separation between bursts (T.sub.r).

20. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 16, wherein the injected current is reduced by reducing a duration of impulses (T.sub.imp), as long as the R.sub.PE stability is good.

21. The combined device for protection against transient overvoltages and monitoring of an electrical installation, according to the claim 10, wherein the electronic circuit comprises, in an integrated manner, a dual protection against transient overvoltages: A first protection stage comprising the protective component(s), which absorb(s) most of the energy of the transient overvoltages, leaving a lower residual voltage between its two poles; A second protection stage in which the residual voltage is limited to acceptable values, which prevents the destruction or malfunction of the means of monitoring, as it causes much greater reduction in disturbances that could affect it, either due to the residual voltage of the protective component, or due to the electromagnetic field that is generated.

22. A plug-in cartridge, of the type that are inserted alone or together with other plug-in cartridges in a fixed base to form a combined device for electrical protection against transient overvoltages and the monitoring of an electrical installation of the type that are used in single-phase or multiphase alternating voltage installations, in which each cartridge comprises: one or more protective components protecting against transient overvoltages and being a varistor(s), gas arrester(s), gas discharge tube(s), spark-gap(s), suppressor diode(s), triac(s), thyristor(s), and/or MOSFET(s); means of monitoring set up in such a manner as to permanently measure and process one or several parameters in relation to the condition of the electrical installation and the one or more protective components; and a means of indication connected to said means of monitoring and configured to indicate the following output parameter: If the value of earth resistance (R.sub.PE) measured by the means of monitoring is inside or outside of certain predetermined limits (R.sub.PEmin and R.sub.PEmax) wherein the earth resistance value R.sub.PE measured by the means of monitoring is based on the injection of current impulses to earth via a PE terminal using a phase to earth loop and these impulses are of high enough intensity to determine the increase in voltage caused by the injected impulses with regard to voltage in an earth system, but without triggering a possible residual current circuit device(s) (RCD) which is/are installed in the electrical installation, or causing a malfunction of the residual current circuit device(s) in the long term; wherein the means of monitoring uses a dynamic method to control an angle of injection of the current impulses, depending on the AC supply voltage, and/or resistance of the earth system R.sub.PE, and/or the stability of the R.sub.PE measurement made; and further wherein the means of indication is setup to optionally indicate one or a combination of the following parameters: Indication of whether at least one of the protective component(s) protecting against overvoltages that are built into the cartridge has reached the end of its useful life; If the wiring between the cartridge and the electrical installation comprising a line conductor (L), a neutral conductor (N), and a protective conductor (PE) or protected earth neutral conductor (PEN) is correct; If a supply voltage of an alternating network (v.sub.L) falls within predetermined normal limits such that v.sub.L is between v.sub.Lmin and v.sub.Lmax, wherein v.sub.Lmin and v.sub.Lmaxrepresent a lower supply voltage limit and an upper supply voltage limit, respectively; If an earth system voltage (v.sub.PE )is greater than or equal to an earthing system threshold voltage (v.sub.PEmax).

23. The plug-in cartridge, according to claim 22, further comprising a means for disconnecting from the supply voltage at least one of the protective components that are integrated into the cartridge.

24. An operational procedure for a combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the means of indication are configured by a first type of indicator and by a second type of indicator, wherein: the first type of indicator is activated in different stages of indication to provide information about whether the connection to the mains is incorrect, and/or voltage v.sub.PE?v.sub.PEmax, and/or the mains voltage (v.sub.L) meets the condition of v.sub.Lmin>v.sub.L>v.sub.Lmax; when all of the aforesaid is correct, the first type of indicator issues a corresponding indication depending on the obtained R.sub.PE value falling within predetermined margins; the second type of indicator emits an indication, if the protective component(s) included in the cartridge or in the monoblock in which the said second indicator is located has reached the end of its useful life, characterized in that the order of actuation of the different stages and different activation conditions of the first type of indicator are: Stage 1 (optional stage): Delay; Stage 2: If the connection to the mains is incorrect.fwdarw.Indication 1 is activated; Stage 3: If voltage v.sub.PE?V.sub.PEmax.fwdarw. Indication 2 is activated; Stage 4: If mains voltage (v.sub.L) has such a value that v.sub.Lmin?v.sub.L>v.sub.Lmax.fwdarw.Indication 3 is activated; Stage 5: If all the above conditions are correct, then the first type of indicator issues the corresponding indication in accordance with the R.sub.PE value obtained within predetermined margins of values of the resistance of the earthing system (R.sub.PE).

25. An operational procedure for a combined device for protection against transient overvoltages and monitoring of an electrical installation, according to claim 1, wherein the means of indication are configured by a first type of indicator, where the first type of indicator is activated in different stages of indication to provide information about whether the connection to the mains is incorrect, and/or voltage v.sub.PE?V.sub.PEmax, and/or mains voltage (v.sub.L) meets the condition of v.sub.Lmin>v.sub.L>v.sub.Lmax; when all of the aforesaid is correct, the first type of indicator issues a corresponding indication in accordance with the R.sub.PE value obtained within the predetermined margins, characterized in that the order of actuation of the different stages and different activation conditions of the first type of indicator are: Stage 1 (optional stage): Delay; Stage 2: If the connection to the mains is incorrect.fwdarw.Indication 1 is activated; Stage 3: If voltage v.sub.PE?V.sub.PEmax.fwdarw.Indication 2 is activated; Stage 4: If mains voltage (v.sub.L) has such a value that v.sub.Lmin>v.sub.L>v.sub.Lmax.fwdarw.Indication 3 is activated; Stage 5: If all the above conditions are correct, then the first type of indicator issues the corresponding indication in accordance with the R.sub.PE value obtained within predetermined margins of values of the resistance of the earthing system (R.sub.PE).

26. The operational procedure, according to the claim 24, wherein the first type of indicator also gives another additional indication, when the protective component(s) included in the cartridge where said first indicator is located reaches the end of its useful life.

27. The operational procedure, according to the claim 24, wherein the predetermined margins of values of the resistance of the earthing system (R.sub.PE) are preferably: Margin 1: R.sub.PE<30 ? Margin 2: 30 ??R.sub.PE<60 ? Margin 3: 60 ??R.sub.PE<600 ? Margin 4: R.sub.PE?600 ?.

Description

(1) In the figures:

(2) FIG. 1 shows a perspective view from the rear part of an eventual application of the external part of an N-PE cartridge.

(3) FIGS. 2 to 5 show front perspective views of the same cartridge as in FIG. 1 in different applications of possible types of indicators:

(4) FIG. 2 shows the case of a cartridge with three lighted indicators for the R.sub.PE value formed by LEDs,

(5) FIG. 3 shows the case of a cartridge having a sole lighted indicator for the R.sub.PE value,

(6) FIG. 4 shows the case of a cartridge with a first type of lighted indicator for the R.sub.PE value and the second type of indicator for the end of the useful life of the protective component, and

(7) FIG. 5 shows the case of a cartridge with three lighted indicators for the R.sub.PE value formed by LEDs and a second type of indicator for the end of useful life of the protective component.

(8) FIG. 6 shows a front view of the internal part of the cartridge of FIG. 1 with three connection terminals to the fixed base (N, L, PE).

(9) FIGS. 7 to 10 show front perspectives views of a first preferred application of the protective and supervision devices of the present invention formed by one or more plug-in cartridges on a fixed base:

(10) FIG. 7 shows a view of an example of application in which the protective and monitoring device is of the single-phase type (N, L), and fitted with indication means formed by a first indicator and a second indicator. The first indicator, preferably an lighted indicator, is activated differently (for example, giving an indication 1, indication 2, indication 3 and indication 4) and providing information on whether the connection to the network and/or the voltage v.sub.PE?v.sub.PEmax and/or the network voltage (v.sub.L) v.sub.Lmin>v.sub.L>v.sub.Lmax are correct or not. When all of the foregoing is correct, the same lighted indicator gives the corresponding indication according to the R.sub.PE value obtained within the selected margins. If it should also be necessary, another kind of indication could be given in the event that the protective component included in the cartridge has reached the end of its useful life. The second indicator located in the other cartridge gives an indication (which may or may not be lighted) in the event that the protective component/s included in the same (L) has/have reached the end of their useful life.

(11) FIG. 8 shows a view of an example of an application in which the protective and monitoring device is of the three-phase type (N, L1, L2, L3), which is fitted with indication means formed by a first lighted indicator that is activated in a different way, providing information on whether the connection to the network, and/or the voltage v.sub.PE?v.sub.PEmax and/or the network voltage (v.sub.L) v.sub.Lmin>v.sub.L>v.sub.Lmax, are correct or not. When all the foregoing is correct, the first optical indicator provides the indicator corresponding to the value obtained for R.sub.PE within the selected margins. If necessary, it could also give a different indication in the event that the protective component inside the cartridge has reached the end of its useful life. The indicators located in the other three cartridges (L1, L2, L3) provide an indication (which may or may not be lighted) as to whether the protective component included in said cartridges has reached the end of its useful life;

(12) FIG. 9 shows a view of an application in which the protective and monitoring device is for photovoltaic applications (L+, PE, L?), which is fitted with indication means formed by a first lighted indicator that is activated in a different way, giving information as to whether the connection to the supply voltage is correct or not, and/or the voltage V.sub.PE?v.sub.PEmax, and/or the supply voltage v.sub.Lmin>v.sub.L+?v.sub.L?>v.sub.Lmax. are correct or not. When all of the foregoing is correct, the same optical indicator provides the corresponding indication according to the R.sub.PE value obtained within the selected margins. The cartridge has another indicator (which may or may not be lighted), to indicate that the protective component included in said cartridge has reached the end of its useful life. The indicators of the other cartridges (L+, L?) indicate, by lighted or non-lighted means, that the protective component included in them has reached the end of its useful life; and

(13) FIG. 10 shows an exposed of the cartridge (N) of FIG. 1 on the fixed base.

(14) FIGS. 11 and 12 show the respective front perspective views of a second preferred application of the protective device forming the subject matter of the invention, formed by a compact or uniblock SPD:

(15) FIG. 11 shows an example of an application in which the SPD protective device is of the single-phase (N, L) type, and

(16) FIG. 12 shows an application in which the protective SPD device is of the three-phase type (N, L1, L2, L3).

(17) FIG. 13 shows a flow diagram of the different stages and activation conditions in a different way to those of the first indicator, for example giving a type 1 indication, type 2 indication and type 3 indication, with each of the indications being in a different colour.

(18) FIG. 14 shows a block diagram of the electronic circuit for the supervision means of the invention together with the protective component located inside the cartridge.

(19) FIG. 15 shows a simplified diagram for the injection of positive and negative impulses.

(20) FIG. 16 shows examples of a 2 impulse bursts; in the second diagram the case is shown of bursts by 2 positive impulses, and the third diagram shows the case of bursts of one positive impulse and one negative impulse in which the variable T.sub.r is the time lapse between bursts.

(21) FIG. 17 shows a detail of a impulse in a positive half cycle, in which the variable T.sub.imp is the duration of the impulse.

(22) FIG. 18 shows diagrams in which the effect of the capacity in the v.sub.PE signal is shown. The last diagram is for a capacity of 12 ?F and it shows that there is an error. For this reason, the maximum capacity of the PE system considered is about 10 ?F.

(23) FIG. 19 shows the stages for the reduction of the injected current by decreasing the number of impulses per burst, provided the stability of R.sub.PE is satisfactory, maintaining the width of the impulse for the bursts. In this case, for example, initially 3 impulse bursts are used, which could afterwards change to two impulse bursts and then one impulse if the stability of R.sub.PE is satisfactory. The output impulses from the controller are adapted to the necessary gate-to-source voltage (V.sub.GS) for the conduction of the MOSFET. It is during this time when the current impulse is injected. In all of the stages, the width of the impulses (T.sub.imp) as well as the separation between bursts (T.sub.r) is maintained.

(24) FIG. 20 shows the reduction stages of the duration of the impulses (T.sub.imp), provided that the stability of R.sub.PE is satisfactory. In this case, for example, bursts with 4 impulses are used with an initial duration T.sub.imp1, which may be reduced to a shorter duration T.sub.imp2 (that is T.sub.imp2<T.sub.imp1). The output impulses from the controller are adapted to the necessary gate-to-source voltage (V.sub.GS) in order that the MOSFET conducts, and during this time the current impulse is injected.

(25) FIG. 21 shows the equivalent circuit when the MOSFET Q conducts.

(26) FIG. 22 shows the two types of connections, depending on the system configuration of the three-phase power mains.

DESCRIPTION OF A PREFERRED APPLICATION OF THE INVENTION

(27) A practical but not limitative application of the invention is a protective and monitoring device (10, 10, 10, 10, 10) in which one of the cartridges (11) incorporates the component/s of the protection (20), the supervision means necessary for the supervision of the installation and the necessary indication means, for example by several LEDs (27) and disconnecting means (28).

(28) For example, FIG. 1 shows a cartridge (11) connected between N-PE, using as the protective component (20) a gas arrester or arc arrester, which is used as protection between N-PE of a single-phase and three-phase protective device in TT and TN-S systems. Said cartridge (11) has three connection terminals with the fixed base (18), connected respectively to line (L), neutral (N) and protective conductor (PE). In this case, the transient discharge current, normally of the order of kA, circulates in this case through terminals N-PE, and a lower current circulates through terminal (L), for which reason the cross section may be reduced.

(29) Additionally other connection terminals may be added for protective devices, for instance three-phase devices in which it is necessary to know the voltages in each phase.

(30) Added connection terminals can also be used to transmit the information obtained from the monitoring device and/or the end of life or status indicator of the protective component to the fixed base.

(31) However, if needed due to installation requirements necessary, a varistor or another protective component can be used.

(32) FIG. 6 shows the layout of the electronic circuit (19) that integrates the monitoring means and the double protective component/s (21) in one of the cartridges (11), which in this particular example determine: the value of the impedance from the PE terminal to earth, if there is voltage in the earthing system that could be dangerous, if the supply voltage of an AC or DC network V.sub.L falls within normal limits, i.e. if the V.sub.L is between V.sub.Lmin and V.sub.Lmax and if there are any errors in the SPD device connection or wiring installation, indicating to the user the situation. If desired, optional means can also be included to indicate that the protective component has reached the end of its life.

(33) The above indication of these parameters is preferably carried out by several LED diodes (27), of different colours, that can be fixed or flashing to allow the user to correctly interpret the situation, for example with three or four diodes. See the different configurations in FIGS. 2 to 5.

(34) FIG. 13 shows the order of operation of the various stages and activation conditions in a different manner from the first indicator light, for example giving an indication 1, indication 2, indication 3 and an indication depending on different R.sub.PE values: Stage 1 (optional): when connecting the power to the monitoring circuit, there may be a delay before performing the different tests, with the main objective of allowing voltage in the electronic circuitry of the device to stabilise, in order to prevent a false failure indication. Stage 2: if the network connection is incorrect.fwdarw.Indication 1 is activated. Stage 3: if the voltage in the earthing system v.sub.PE?v.sub.PEmax.fwdarw.Indication 2 is activated. Step 4: if the mains voltage (v.sub.L) has a value such that v.sub.Lmin>v.sub.L>v.sub.Lmax.fwdarw.Indication 3 is activated. Stage 5: if all the above conditions are correct, then the same visual indicator (in the case of FIG. 7) gives the corresponding indication according to the R.sub.PE value obtained within the 4 preferred R.sub.PE value margins: Margin 1: R.sub.PE<30 ? Margin 2: 30 ??R.sub.PE<60 ? Margin 3: 60 ??R.sub.PE<600 ? Margin 4: R.sub.PE?600 ?

(35) The indication corresponding to R.sub.PE?600 ?clearly indicates a dangerous situation in the facility, as it means the earthing system is in an open circuit.

(36) To determine the value of the earthing system impedance (R.sub.PE) in step 5, the monitoring means inject current impulses to earth through the PE terminal.

(37) If any of the checks in stage 2, stage 3 or stage 4 are incorrect (i.e. the connection, the earth system voltage (v.sub.PE) or the value of the network voltage (v.sub.L), then the system stops at that point and checks it regularly (preferably every few seconds). Once the failure has been corrected, it proceeds to step 5 of the impulse injection. If the process does not stop, the values obtained in the monitoring of the earthing system impedance in Step 5 would be incorrect.

(38) Internally, the first lighted indicator is formed, in accordance with a possible application, by a series of LEDs in different colours, depending on the type of indication, with some or others lighting up, depending on their status. In addition said LEDs can be fixed or flashing.

(39) To determine the value of the earth system impedance (R.sub.PE) or earth voltage (v.sub.PE), it is not necessary to use means with a very high degree of sophistication, since for the specific implementation of this invention, the applicant has found that it is sufficient with values having an accuracy of less than 10%. Thus it is possible to obtain a device for the protection and monitoring that is both small and has a low cost. With this degree of accuracy, the visual indications given to the user have ample safety margins.

(40) The means for determining the value of the impedance of the earthing system (R.sub.PE) or earth voltage (v.sub.PE) are based on the application of current impulses to earth via the PE terminal using the phase-earth loop. These impulses meet a number of requirements:

(41) They are of sufficiently high intensity to determine the voltage increase in the earthing circuit, but in turn must not cause the actuation of the possible residual current circuit breakers in the circuit, nor should they cause a malfunction in the residual current circuit breaker at long term.

(42) Long term malfunctioning of the residual current circuit breaker can happen for several reasons. The RCD contain sensitive magnetic components with a degree of magnetisation adjusted by each manufacturer and which depends on its sensitivity to detect the difference of AC currents between conductors that cross it. If current impulses of a single polarity are applied with a high repetition rate, e.g. in each cycle or half cycle of network, such as in the ES2266761 patent or trains with large numbers of impulses, such components may be magnetised/demagnetised permanently in the long term (a few years) and their malfunction is not detected until there is a fault in the installation. The user could periodically check the operation of the RCD, as indicated by their manufacturers, but this is rarely, mainly in household environments.

(43) All these requirements described can be met largely by using current impulses of a small value, with a very small number of impulses in the injected bursts and a very low burst repetition frequency (which is variable and controlled from some seconds to several minutes).

(44) Other known systems today employ currents and frequencies with a much higher repetition to reduce the influence of noise and obtain a reduced accuracy value for very low impedances, in which the increase of voltage in the earthing system caused by the injected impulse is very low. These features are not only unnecessary in the device forming the subject matter of the invention but would also be counterproductive. The claimed protective and monitoring device is not essentially a measuring instrument, but a protective device that includes means to permanently monitor the most important parameters during the facility installation, operation and maintenance processes, in addition to alerting the status of the installation and of the device itself.

(45) When determining the impedance of the earthing system it must also be considered that this does not generally have a purely resistive component, and depending on the state of the installation, it will also present inductive and capacitive components. However, as the monitoring means are preferably installed in the device, the key components are normally resistive and capacitive, since the SPD device is installed in the origin of the installation and the wiring length is reduced and is specifically executed to minimise the inductive effects that it could introduce.

(46) Therefore, the applicant has concluded, after several tests, that the duration of the current impulse (T.sub.imp) must be long enough to not be affected by the capacitive component of the impedance in the measurement of the voltage increase. The monitoring circuit used by the present invention is provided to obtain an accuracy lower than 10%, having capacitive components as high as 10 ?F, but they are generally much lower.

(47) Through numerous experimental tests of repeated measurements in different types of facilities, the applicant has finally determined that the preferred values of the duration of the current impulse (T.sub.imp) are between 200<T.sub.imp<300 ?s. The tests made by the applicant in different types of RCD devices, both new ones and devices installed for many years, suggest that this range of values is more desirable for optimum results with earthing system impedances that have high capacitive components. However, other values could be used for the T.sub.imp application of this invention, without changing the essence of the invention.

(48) The value of the earthing system impedance (based on the above considerations, only its resistive R.sub.PE value may be considered) is obtained by determining the voltage increase caused by the injected impulse current with regard to the voltage in the earthing system (this voltage is variable over time, normally at the same frequency as the supply voltage and may have a sufficiently high value to alter the result of the R.sub.PE measurement if not considered), the measurement of the increase in the earthing system voltage is carried out in the last microseconds of the injected impulse to minimise the influence of capacity and/or inductance that may exist. Considering the duration values of the impulse current (T.sub.imp) indicated above, the values of the voltage increase have stabilised sufficiently to meet the accuracy requirements.

(49) Another requirement to be met by the circuit that conforms to the monitoring means is to indicate whether the mains voltage (v.sub.L) is within the operating range of the SPD device and the monitoring circuit. In most countries, the standard voltage margin tends to be between +10%-15% of the rated voltage, so when sizing the SPD device, a Uc value that is 15-20% higher is normally used (v.sub.Lmax) at the rated voltage (v.sub.Lnom). This prevents the SPD from conducting for the maximum voltage values of the mains voltage and becoming permanently damaged. If the voltage value (v.sub.L) is less than the minimum value indicated (v.sub.Lmin), the monitoring circuit can give incorrect indications, and the operation of connected loads and installation equipment may also be affected; if the voltage value is higher than the SPD Uc, the life of the device is reduced or it may be permanently damaged, also affecting to the equipments and loads connected downstream of the SPD. The voltage ranges indicated are considered the preferred ones, as they are those most commonly used, but different values may be used if deemed necessary.

(50) The protective and monitoring function of the present invention is preferably performed according to the electronic circuit scheme shown in FIG. 14. In this example the AC/DC (22) converter supplies a DC voltage V.sup.+ from the common circuit point (GND), which is connected to terminal (N) of the cartridge. This AC/DC (22) converter must comply with strict requirements in terms of performance characteristics, its line regulation must be very high because the AC input voltage margin is high. It must also be able to withstand temperature margins ranging between ?40? C. and +80? C. (which are the usual margins for SPD devices) and regulate the V+ voltage correctly, since this voltage depends on the correct result of the voltage measurements. The V.sup.+ voltage is used to power the controller (25) and adapters (23) and (24). The output voltage of these adapters (23) and (24) provide the controller (25) with DC voltage, normally V+/2, for a maximum dynamic range and a superimposed AC voltage in proportion to their input voltages:
v1(t)=V.sup.+/2+k1V.sub.L(t)[1]
v2(t)=V+/2+k2V.sub.PE(t)[2]

(51) Hereafter the time-dependent variables (v.sub.1 (t) and v.sub.2 (t)) shall be indicated only with the letter of the variable and in the lower case.

(52) Adapters (23) and (24) are composed of passive and/or active devices, further allowing the possibility of filtering high frequency components (generally noise and/or harmonics) that may come from the v.sub.L voltage network or the v.sub.PE earthing system voltage. The parameters k.sub.1 and k.sub.2 in the above equations [1] and [2] can represent both a gain and an attenuation of signals v.sub.1 and v.sub.2, and may or may not be dependent on the frequency (filter). k.sub.1=k.sub.2 and are normally<1. In certain applications, it may be necessary for the adapter (24) to amplify the v.sub.PE voltage so k.sub.2 would exceed k.sub.1.

(53) As shown in the diagram of FIG. 13, based on the voltage in L, N and PE the circuit detects whether the wiring connecting the SPD device or installation is correct, e.g. the V.sup.+ voltage is a positive voltage regardless of whether the L and N connection is correct or interchanged, and at this point the circuit can measure the v.sub.1 voltage (obtained from v.sub.L) and v.sub.2 voltage (obtained from v.sub.PE) and determine whether the L? N connection is correct or not (v.sub.L?v.sub.PE?v.sub.L and voltage v.sub.N?v.sub.PE?0). If the result of this check is correct, the monitoring process continues, otherwise, the circuit gives an indication of this failure and the situation is checked periodically every few seconds until the fault has been corrected.

(54) If the result of the above check is correct, the device then checks the v.sub.PE voltage, and if it is less than the maximum value set (preferably in the range from 20V to 40V) the monitoring process continues, otherwise the circuit gives the indication of this failure, checking the situation periodically every few seconds until the fault has been corrected.

(55) The process continues to determine the value of the voltage by voltage value v.sub.1, which is proportional to v.sub.L. If this value is within the range v.sub.Lmin?v.sub.L?v.sub.Lmax the monitoring process continues, otherwise the circuit gives an indication of this failure, checking the situation regularly (preferably every few seconds) until the fault is corrected.

(56) When all checks are successful, then it proceeds to the injection impulse on the PE terminal to determine the earthing system impedance value. However, the above checks are still carried out regularly. Even so, in certain cases the non-interruption of the process may be partially assumed, despite the existence of faults, for example, if the wiring is correct but the system voltage earthing is higher than that set, it could indicate this fault, but continue measuring the voltage to ensure it is within the correct margins. However, it would be advisable not to inject current impulses in the earthing system.

(57) The method indicated in FIG. 13 represents an advantage in terms of the safety of the installation or users with respect to other known devices. In the device of the invention, it is provided, optionally, that when the power is connected, there is a time delay before the different tests are performed. Previously it was indicated that one of its objectives was to permit the stabilising of voltage in the electronic circuitry of the device, to avoid false failure indications, and another goal is to prevent anything from interfering with the operation of the RCD device when connecting the AC supply voltage.

(58) The protection and monitoring uses the v.sub.1 and v.sub.2 signals respectively (which are proportional to the v.sub.L and v.sub.PE signals) to determine the earthing system impedance value (R.sub.PE). This process is performed by injecting a impulse in a positive half cycle, but it is preferably repeated up to 4 times in consecutive half cycles (bursts of 1, 2, 3 or 4 impulses, injected continuously and always containing the same number of impulses). See FIG. 16. The v.sub.PE voltage increase caused by the current impulse allows the earthing system impedance to be obtained for each unit impulse applied. It takes as the earth system impedance that obtained for each burst, this being determined preferably by the average value obtained for each unit impulse. The reason for this to minimise the influence of variations that may exist in v.sub.1, and/or v.sub.PE voltage and/or noise present on the network and the value obtained is used when giving the indication to the user (27) or other possible warning signs if deemed necessary.

(59) As indicated above, the process is repeated continuously, and continuous impulse bursts are applied, with a separation between them, preferably of between several seconds and several minutes. The separation between bursts (T.sub.r) will be depend on the stability obtained in the earthing system impedance measurement (since the power dissipation of the circuit is very low with the method used). For example, when the power is connected, a separation of a few seconds can be used, and then gradually increased to several minutes, when it remains stable, unless variations are detected, such as a higher impedance, preferably between 10-20% from one burst to the next, in which case the separation between bursts is reduced. These variations may be caused for example by breaking the connection between the SPD device and the earthing system and/or by noise or fluctuations in v.sub.L and/or v.sub.PE signals, since as indicated above, impedance changes take place very slowly (significant changes in the temperature and/or humidity of the soil).

(60) Using multiple measurements on different types of installations, it has been found that this number of impulses per burst and the indicated separation between bursts are sufficient to obtain the required accuracy within the established margins. The value margins indicated are considered the preferred ones, but different values may be used for the number of impulses per burst and the separation between them if deemed appropriate, without altering the essence of the invention. However, it has become apparent that it would be desirable to use the minimum number of impulses possible, which greatly reduces the probability of the unwanted actuation of the RCD, possible interference in the operation of sensitive equipment connected to the network and the premature ageing thereof due to changes in the magnetisation of the components incorporated into the RCD.

(61) The process continues by determining the zero passage of the v.sub.L voltage from the negative half cycle to the positive one. This signal is taken as a 0? reference of the AC voltage network, and the impulse is preferably injected at an ? angle between 90? and 150?. To that end, the controller generates an impulse with a duration T.sub.imp that turns on the MOSFET transistor (Q). Under these conditions, the equivalent circuit is shown in FIG. 21.

(62) Whereas the adapters (23) and (24) have an input impedance that is high enough to get currents i.sub.1 and i.sub.2<<i.sub.PE, the following equation is obtained:
i.sub.PE=v.sub.L?v.sub.PE/R.sub.1+R.sub.PE=v.sub.3?v.sub.PE/R.sub.PE[3].

(63) In this equation [3] v.sub.3 is the voltage in the terminal PE of the SPD when the current impulse is injected. The indicated v.sub.PE value generator is the earth voltage when the impulse is not injected, normally is a voltage at the same frequency as the network but in normal conditions of a reduced value.

(64) v.sub.L is determined from the measurement of the voltage v.sub.1 and v.sub.3 from the v.sub.2 measurement, with R.sub.1 being known and established by design to limit the injected current to earth through Q. As R.sub.PE and v.sub.PE are unknowns, if is possible to determine the value of v.sub.PE the R.sub.PE value can be determined by calculation in the controller.

(65) It is possible to obtain a very approximate value of v.sub.PE by measuring its value a few microseconds before injecting the current impulse and this value can be used in equation [3], since the duration of the applied impulse is very short and it can be considered that v.sub.PE is about the same value as during the measurement of v.sub.L and v.sub.3. These two variables are measured during the last microseconds of the current impulse, so that the voltage v.sub.3 is stabilised, thus preventing the effect of the capacitance and inductance of the earthing system. It should also be considered that the v.sub.L and v.sub.3 measurements are made simultaneously, so that a possible variation in the network voltage will not affect the measurement result. Thus, a value of R.sub.PE with the adequate accuracy required by the monitoring system is obtained that is largely independent from the existence of voltage in the earthing system, variations or noise in the network voltage, and high capacitance or inductance in the earthing system.

(66) There is one more factor that has not been considered until now, namely to avoid increased corrosion problems in the earthing system caused by electrolysis. This phenomenon is increased by the injection current with a DC component, it is true that the average current values used (evaluated in years) are small but they increase the corrosion process that occurs in the electrodes and the means of interconnection with the earthing conductor. The electrolysis is further increased by moisture but precisely is convenient that the earth electrodes installation remains moist. This type of corrosion is significantly attenuated by using protective conductors, earth electrodes (usually rods) and interconnecting pieces of the same material. This situation occurs very rarely. The materials used in the earthing installation are usually copper for the protective conductor and for the electrodes and interconnecting pieces, iron or galvanized steel, stainless steel, and copper coated steel.

(67) The first two types (iron or galvanized steel and stainless steel) are those most commonly used for the electrodes and interconnecting parts, which are those most affected by corrosion. More and more often, steel electrodes are used with different copper coating thicknesses, making them more resistant to corrosion. However, the manufacturers of these materials and installers who inspect the earthing system find that their length is significantly shorter than forecasted. One of the influencing factors that is not usually considered is continuous earth leakage in the installation, which increases considerably with the mass incorporation of electronic equipment in all types of facilities.

(68) It would not be wise to install a system to monitor the status of the earthing system that accelerated its corrosion, as it injects current impulses with a continuous component, and it is always necessary to bear in mind that it must evaluate the behaviour of the set for many years: SPD with monitoring device+RCD+earthing system installation.

(69) In summary, the protective and monitoring circuit must inject the smallest possible number of impulses with the minimum amplitude of current possible to obtain the adequate accuracy for the product under consideration. To this end, the present invention uses a method for controlling the dynamic current impulse injection angle, depending on the AC supply voltage, the earthing system resistance and the stability of the measurement taken.

(70) The process for injecting a minimum current value so that the required accuracy is obtained is by injecting the current impulse preferably an angle ??90? and ?150? of the voltage of each positive half cycle of the unit comprising the burst, thus reducing the injected cur rent as the value ? increases to a value of 50% of the maximum value (sin 150?=0.5). It should be noted that whenever possible it is necessary to avoid injecting impulse areas in areas close to 90?, because at such points the filter capacitors used in power supplies with input network voltage rectifiers are recharged. Although the increase in voltage caused by the current impulse is small, its frequency spectrum is high, since current impulses in microseconds and with much smaller rise/fall times are injected, the high frequency components could eventually affect the controller if it is not correctly designed. The ? angle is controlled depending on the v.sub.L voltage network; for v.sub.Lmax an angle ? of 150? is preferably used and for v.sub.Lmin ? a 90? angle is preferably used. For intermediate values of v.sub.L it is preferable to adjust the angle ? in a linear way, and other criteria may be used if appropriate.

(71) The ? angle control is set individually for each of the impulses of the burst, since v.sub.L may vary from one half cycle to another. For this purpose the circuit determines the zero passage of the voltage of the negative half cycle to the positive as reference ?=0?, and determines the value of v.sub.L as 90? and depending on that value it applies the impulse at the angle. As a numerical non-restrictive example for a nominal voltage network v.sub.LNOM=230V?15% the following equations are obtained:
v.sub.Lmax=264.5 V.fwdarw.v.sub.L(90?)=374 V.fwdarw.?=150?
v.sub.Lmin=195.5 V.fwdarw.v.sub.L(90?)=276 V.fwdarw.?=90?
v.sub.Lnom=230 V.fwdarw.v.sub.L(90?)=325 V.fwdarw.?=130?

(72) The injection of the impulse at an exact angle is not a critical aspect, as when measuring v.sub.PE and v.sub.L voltages simultaneously, they do not the changes in the sinusoidal signal in the half cycle, and neither do they have any noticeable effect on the fact that a superimposed noise may exist in measuring the voltage at 90? that affects its value and applies a phase angle that is different from the one calculated since ? is bounded between 90? and 150? and besides, resistance R.sub.PE is obtained by averaging the value obtained for each individual impulse of the burst, which tends to cancel out any errors.

(73) From the standpoint of the user, we should also consider that the indication of the earthing impedance values in the cartridge is preferably done by value margins using LEDs. A series of R.sub.PE margins that have been shown to be suitable are: Margin 1: R.sub.PE<30 ? Margin 2: 30??R.sub.PE<60 ? Margin 3: 60??R.sub.PE<600 ? Margin 4: R.sub.PE?600 ?

(74) Margin 4 clearly indicates a dangerous situation in the installation because the system would understand that the system is an open circuit.

(75) On the contrary, margin 1 indicates that the impedance is suitable from the point of view of safety and the effectiveness of the transient overvoltage protection.

(76) The number of R.sub.PE margins, the value of the R.sub.PE margins and the number of indicators and indications can be modified and adapted according to the specific needs of the protection and supervision device, so using different ones will not alter the essential nature of the present invention.

(77) The above process is also completed by using the R.sub.PE value obtained in each burst. In other known devices higher values are generally used in the current impulses and it should be noted that with very low levels of R.sub.PE the voltage increase resulting from the impulse is reduced and, therefore, likely to be affected by noise. This is not necessary in the circuit of the invention with R.sub.PE resistances exceeding tens of ohms, since the voltage increase caused by the impulse current in the system earth is high enough to not be significantly affected by noise. However the operation can be improved for small R.sub.PE, because the circuit includes adapters (23) and (24), which can amplify the corresponding signals, filter and for example, enter a variable gain, depending on the voltage level input to prevent damage to the controller (or limit the output voltage level).

(78) This means that the decision criterion for adjusting the injection angle ? in each half cycle of the burst based on the value of the voltage v.sub.L ?=90? is preferably modified depending on the value of R.sub.PE obtained for the previous burst, so that as the R.sub.PE ? value rises, the current value 0 is increased to reduce the current further, and vice versa.

(79) For example, the mean R.sub.PE value obtained could be used for several prior bursts to make the system more stable as it has already been indicated that under normal conditions, R.sub.PE changes slowly and seasonally throughout the year.

(80) A sudden change between one burst and the next occurs in the event of an interruption in the earthing system, due, for instance, to the disconnection or failure of the earthing system somewhere on its path, and this would be detected by the circuit because the process of applying the bursts is indefinite unless an error is detected in the connection, if v.sub.PE is higher than the established value or if v.sub.L were out of the correct margins. Once these problems have been solved, the circuit would continue with the impulses injection.

(81) Another factor to be considered in the present invention when controlling the ? angle is the stability of the R.sub.PE value obtained from one burst to the next. One of the preferred criteria used is as follows: if between one burst and the next there is a variation in R.sub.PE of more than 10-20% ? and/or T.sub.r will be gradually reduced to increase the level of the injected current, obtain greater in v.sub.PE voltage increases and check more quickly whether there has been a change in the current R.sub.PE or whether it was due to a perturbation in the mains voltage. Thus the effect of any noise or existing variations in v.sub.L and/or v.sub.PE voltages is reduced, as it has been detected that the stability in determining the R.sub.PE value is within the ranges indicated and ? and/or T.sub.r will be modified, based on v.sub.L and R.sub.PE.

(82) Another criterion that can be applied is to use the change of status in the R.sub.PE indicators so that in the event of a change in status of the indications, minimum ? and T.sub.r values are applied. This will increase the sensitivity of the system and the indication will be updated more quickly.

(83) These criteria or methods described are given as a guideline, but others could be used without changing the meaning of the invention.

(84) We should consider that with the ? margin indicated (90-150?), accuracies below 10% were obtained in determining the resistance of the earthing system, and ? values higher than 150? could be considered if greater accuracies were admitted.

(85) The present invention aims to inject the smallest possible number of current impulses with the lowest possible value.

(86) However, it can be considered that the development of a controller with such types of control may increase the cost of the circuit, either due to the characteristics of ?C or due to the software development time required. Therefore, the decision could be taken to use only one of the above criteria, for example varying the ? angle based only on the value of v.sub.L or R.sub.PE.

(87) Other criteria that could also be applied in order to reduce the average current injected into the earthing system are the following: The progressive decrease in the number of impulses per burst, as long as this fulfils the criterion that the stability of R.sub.PE is satisfactory, keeping the pulse width (T.sub.imp) for the blasts. For example, in FIG. 19 pulse bursts of 3, which could then become two impulse bursts and then 1 pulse burst, depending on the stability of R.sub.PE. The use of current bursts with a mean value of approximately zero current, i.e. injecting current impulses of different polarities in each half (for example in FIG. 16). With this system, the problems caused by the injection current with the DC component are avoided. In this case, a reduction in the number of impulses could also be applied. Reduce the impulse duration (T.sub.imp), preferably to 75% of the value initially used. It is not considered advisable to reduce it further to avoid measurement errors if the earthing system impedance is capacitive. Other values can be used without altering the essence of the invention. The Ti.sub.mp reduction can be progressive or instantaneous, but preferably the latter, to avoid complicating the development of the controller software and/or the need for a better performance.

(88) When reducing the current, one, several or all of the above criteria can be applied. However, to prevent the system from inputting a stable but incorrect R.sub.PE measurement (it has been possible to reduce the injected current but the device could be more sensitive to noise or other unforeseen parameters) it is highly recommended (but optional) to perform a periodical reset on the measures, i.e. to return to the measurement situation with maximum sensitivity, apply impulses at 90? (regardless of the mains voltage and R.sub.PE), minimum time between bursts, maximum number of impulses initially decided and duration of the initial impulse. From then on, the reduction criteria could be applied gradually. The time between resets is recommended to be a value between 12 and 24 h, although other values can be used at the discretion of the user.

(89) Unlike other devices known to date, in the combined protective and monitoring device described in the present invention the current impulses injected into the loop come from the mains supply and are supplied by the means integrated into the cartridge (when conducting the Q transistor), so there is no need to use any type of battery. On the other hand, filter devices can be used on the adapter (23) and/or digital filtering in the controller software in the case of the present invention to reduce the potential error in the determination of the 0? step. In addition, the device of the invention will not only be noticeable affected by the angle of injection impulse, as it is variable and controlled.