Electrical switching device for detecting a closed switching contact and a protective conductor interruption in a single- or multi-phase electrical supply line

Abstract

Electrical switching device (2) for detecting a non-open switching contact (K) of a disconnecting device (P4) and for detecting a protective conductor interruption in a single- or multi-phase electrical supply line (L) with live conductors (L1, L2, L3, N) and a protective conductor (PE), with a differential current monitoring module (RCMB) comprising an RCMB controller (P6) for evaluating a measurement signal supplied by a current transformer (P9) and for generating a first shutdown signal (S4a), wherein the current transformer (P9) detects a differential current flowing on the supply line (L), and with a system controller (P8) for generating a second shutdown signal (S4b), wherein the disconnection device (P4) is designed to disconnect the active conductors (L1, L2, L3, N) and has a signal input (P41) for receiving the first disconnection signal (S4a) and the second disconnection signal (S4b), and wherein the system control (P8) for receiving a fault signal (S8) is connected to the RCMB control (P6) of the residual current monitoring module (RCMB), characterized in that that the RCMB control (P6) has a fault current control unit (P61) for generating a control signal pattern (S11) which controls a first electronic switching unit (P11) for switching an artificial passive fault current (IF) flowing through one or more of the active conductors (L1, L2, L3, N) and the protective conductor (PE), wherein the switched, artificial, passive fault current (IF) is adjustable so that it can be detected as a differential current by the differential current monitoring module (RCMB), but does not cause a residual current device (RCD) installed in the supply line (L) to respond, wherein the RCMB control (P6) has a signaling device (P63) which signals a detection of the artificial passive fault current (IF) and thus the presence of the functional protective conductor (PE) as well as a mains voltage (UL1, UL2, UL3) and wherein the RCMB control (P6) includes a fault current comparator (P62) which compares a fault current waveform detected by the measuring current transformer (P9) with the fault current waveform expected based on the control signal pattern (S11) in order to reliably detect the switched, artificial, passive fault current (IF).

Description

[0001] The invention relates to an electrical switching device and a method for detecting a non-opened switching contact and a protective conductor interruption in a single-phase or multi-phase electrical supply line.

[0002] For electrical safety reasons, electrical supply lines consisting of one or more phase conductors and a neutral conductor as active conductors as well as a protective conductor are often provided with isolating devices to separate a consumer from the network infrastructure.

[0003] These disconnecting devices usually have switching contacts (relays) which, under certain operating conditions, for example due to high inrush currents, tend to cause their contacts not to open reliably - they can "stick" - and thus there is a risk that the consumer is not safely disconnected from the mains.

[0004] For example, charging cables for Mode 2 charging and charging stations incorporate switching contacts whose functional opening must be monitored. For multi-phase supply lines, this monitoring must be performed for each phase conductor (phase).

[0005] Another source of error is an interrupted protective earth connection. In this case, an installed residual current device (RCD) may no longer provide sufficient electrical safety, especially when charging an electric vehicle. Monitoring an intact protective earth connection is therefore strongly recommended.

[0006] It is known from the state of the art to install one or more galvanically isolated test systems for each phase to monitor the proper opening of switch contacts in the overall electrical system. These test systems detect the mains voltage and forward the results to a higher-level system controller via evaluation logic. However, the component complexity, space and power requirements, as well as the wiring effort and costs, are considerable. Auxiliary relays for each phase mounted on a DIN rail also represent a very complex alternative solution.

[0007] The published patent application DE 10 2009 034887 A1 describes a charging station with a digital safety and monitoring device for providing electrical energy to an electric vehicle. The safety and monitoring device has sensors for detecting at least one electrical variable in the charging circuit and transmits this variable(s) to an evaluation device, which, based on a safety-relevant trigger criterion, activates a switching device for controlled switching of the charging circuit on and off.

[0008] Further measures that lead to increased safety of the electrical system through continuous protective conductor monitoring are not currently used in charging systems.

[0009] In addition, there are monitoring systems that include function-monitored residual current devices and insulation monitoring devices with differential current measurement.

[0010] The published patent application DE 10 2011 082 941 A1 shows a monitoring device and a method for ensuring the function of a residual current device, wherein a DC residual current is detected and, in the event that the detected residual current exceeds a limit value which endangers the protective function of the residual current device, the relevant line outgoing device is switched off.

[0011] The published patent application DE 10 2013 207 141 A1 relates to a residual current device and a method for universal current sensitive residual current measurement with a voltage-dependent functional unit, which has an universal current sensitive residual current measuring device, consisting of a current sensor and an universal current sensitive current detection module, as well as a microcontroller for configuring the voltage-dependent functional unit and for evaluating the residual current detected by the universal current sensitive residual current measuring device.

[0012] Furthermore, published patent application DE 10 2013 225 946 A1 discloses a device and method for insulation monitoring in a power supply system, wherein a main system and a subsystem each have a differential current measuring device for detecting a differential current. In an active measuring method, a measuring signal is impressed, and the residual current driven by the measuring signal is detected by means of a differential current measurement in the line outlets to be monitored.

[0013] US patent US 5 231 309 A describes a residual current device for a copier in which false triggering can be prevented by a time and level control.

[0014] Continuous monitoring of the switching contacts of the protective devices and the protective conductor connection is not provided for in the aforementioned state of the art.

[0015] The present invention is therefore based on the object of taking technical measures that reliably monitor the functional opening of a switching contact and a protective conductor connection.

[0016] This object is achieved with the features according to patent claim 1 by an electrical switching device for detecting a non-opened switching contact and a protective conductor interruption in a single-phase or multi-phase electrical supply line with active conductors and a protective conductor.

[0017] It is known from the prior art to use a residual current monitoring module (RCMB) to monitor fault currents caused, for example, by a ground fault. This module has a controller (RCMB controller) for evaluating a measurement signal supplied by a measuring current transformer and for generating a (first) shutdown signal. The measuring current transformer detects a fault current appearing as a residual current on the supply line.

[0018] Furthermore, it is known to couple the residual current monitoring module with a disconnection device that disconnects the active conductors of the supply line.

[0019] A higher-level system controller can also be present in a known manner, which transmits a second shutdown signal to the shutdown device as an alternative or in addition to the residual current monitoring module. The higher-level system controller is informed of the occurrence of a residual current via an error signal from the control of the residual current monitoring module.

[0020] According to the invention, the control of the residual current monitoring module (RCMB control) is expanded to include a fault current control unit for generating a control signal pattern. The control signal pattern consists of a sequence of switch-on pulses that are forwarded to a first electronic switching unit to excite a possible artificial, passive fault current on one or more of the active phase conductors and the protective conductor (as the return conductor). If the switch contact to be tested is not open and the protective conductor is intact in a closed circuit, this fault current then actually flows and can be detected and evaluated. According to the control signal pattern specified in the RCMB control, a temporal pattern of switched-on / switched-off fault current curves is generated on the electrical supply line, which in turn is detected by the measuring current transformer and evaluated in the RCMB control.

[0021] By varying control signal patterns during monitoring, reliable detection of the artificial, passive fault current is ensured even at high dynamic interference levels during ongoing operation of the electrical system (supply line) to be monitored.

[0022] According to the invention, the amplitude of the switched artificial passive residual current is set such that it can be detected as a residual current by the residual current monitoring module, more precisely by the RCMB control of the residual current monitoring module, but does not lead to a response of a residual current device (RCD) installed in the electrical supply line.

[0023] The magnitude of the artificial, passive fault current is preferably in the range of 200 µA to 3500 µA, thus below the response value (trip threshold) of a residual current device (RCD). This magnitude is therefore also below the permissible protective conductor current and the permissible touch current.

[0024] If such an artificial, passive fault current is detected, this is considered an indication that a functioning protective conductor is present and that a mains voltage is present at the respective active conductor. Thus, the monitored switch contact is closed and the protective conductor is intact. The presence of the intact protective conductor and the mains voltage is indicated by a signaling device.

[0025] In this respect, depending on the objective of the monitoring task, it can be determined whether the switching contact to be monitored is actually open as intended and therefore no fault current should flow, or, if the switching contact is intended to be closed for operational reasons, whether the protective conductor is interrupted.

[0026] The invention thus leads to an increase in electrical safety through the proposed monitoring and makes it possible to reduce the number and cost of components as well as the required installation space and power consumption.

[0027] The RCMB control system includes a fault current comparator that compares a fault current waveform detected by the measuring current transformer with the fault current waveform expected based on the control signal pattern in order to reliably detect the switched, artificial, passive fault current.

[0028] By specifying an on / off switching pattern for the fault current to be switched by the RCMB controller using the control signal pattern, the artificial fault current can be reliably distinguished from actual, unintentionally occurring fault currents or other interference. Only if the detected fault current profile matches the fault current profile expected based on the control signal pattern is the detected fault current interpreted as an indication of the presence of voltage and thus of a closed switching contact and an intact protective conductor.

[0029] In further advantageous embodiments, the residual current control unit is designed to generate a first control signal to a second electronic switching unit in order to switch an artificial tripping current for triggering the residual current protective device and / or the system controller is designed to generate a second control signal to the second electronic switching unit in order to switch an artificial tripping current for triggering the residual current protective device.

[0030] In order to force a residual current device installed in the supply line to trip and thus disconnect the consumer from the network infrastructure, an artificial tripping current is generated by the residual current control unit or the system control, which causes this residual current device to trip.

[0031] This ensures that, in order to detect an interruption in the protective conductor, the supply line can be safely separated or connected consumers can be switched off from the overall system without the need for additional switching-off devices.

[0032] Advantageously, the first electronic switching unit has three electronic switches, wherein each of the three active phase conductors is assigned an electronic switch in order to switch an artificial, passive fault current separately for each of the three active phase conductors.

[0033] In this configuration, in the case of a three-phase supply line, a separate fault current is switched for each active phase conductor, which is detected by the measuring current transformer and evaluated by the RCMB controller. This information can be forwarded to a higher-level system controller in the form of a fault signal.

[0034] Advantageously, the RCMB control system comprises a measuring device for measuring the mains frequency and / or for detecting the rotating field direction by means of suitable control signal patterns on the active phase conductors.

[0035] By using a different control signal pattern for each of the active phase conductors, a mains frequency measurement and / or a rotary field direction detection can be carried out.

[0036] As an alternative to the separate switching of the artificial, passive fault currents for each of the three active phase conductors, the first electronic switching unit has precisely one electronic switch that switches a common artificial, passive fault current for the three active phase conductors in a three-phase supply line. In this configuration, all three active phase conductors are considered in such a way that the potential fault current flows simultaneously through all three active phase conductors.

[0037] The object underlying the invention is further achieved by a method according to the invention for detecting a non-opened switching contact and a protective conductor interruption in a single-phase or multi-phase electrical supply line with active conductors and a protective conductor.

[0038] The method according to the invention forms the basis for the aforementioned realization by means of the electrical switching device according to the invention.

[0039] In this respect, the advantages and technical effects mentioned apply equally to the method according to the invention.

[0040] Further advantageous design features will become apparent from the following description and the drawings, which illustrate a preferred embodiment of the invention using examples. They show: Fig. 1: State-of-the-art electrical protective devices for an electrical supply line, Fig. 2: an electrical circuit device according to the invention for a phase conductor, Fig. 3: an electrical switching device according to the invention for three-phase conductors, Fig. 4: an electrical switching device according to the invention for three-phase conductors (variant), Fig. 5: an electrical circuit device according to the invention according to Fig. 4 with second electronic switching unit and Fig. 6: a time course of an artificial, passive fault current.

[0041] Fig. Figure 1 shows state-of-the-art electrical protection devices for a three-phase electrical supply line L and essentially corresponds to a standard configuration for monitoring with a modular residual current monitoring device (residual current monitoring module RCMB).

[0042] The supply line L comprises three phase conductors L1, L2, L3 and a neutral conductor N as active conductors, as well as a protective conductor PE. Furthermore, the supply line L is protected by a residual current device (RCD), which disconnects a load P5 from the power supply if a fault current exceeds the response value of the residual current device (RCD). The response value (rated residual current) is usually above 6 mA.

[0043] The residual current monitoring module RCMB and a disconnection device P4 are connected between the residual current device RCD and the consumer P5.

[0044] The RCMB residual current monitoring module comprises a measuring current transformer P9, which detects a residual current on the supply line L and transmits a measurement signal to the RCMB controller P6 for evaluation. The evaluation result is forwarded to a higher-level system controller P8 in the form of an error signal S8. Both the RCMB controller P6 and the system controller P8 each generate a shutdown signal S4a, S4b, which activates the shutdown device P4, which disconnects the supply line L.

[0045] The shutdown device P4 has switching contacts K, which serve to disconnect the supply line L and whose functional opening behavior must be monitored.

[0046] Fig. 2 shows an electrical circuit device 2 according to the invention for a phase conductor L1 of the supply line L.

[0047] An arrangement with a 3-phase supply line L is shown, but the electrical switching device 2 can also be used in an analogous manner in a single-phase supply line L for detecting a non-opened switching contact K of a shutdown device P4 and for detecting a protective conductor interruption.

[0048] According to the invention, the RCMB controller P6 is expanded with a residual current control unit P61, which generates a control signal pattern S11 that controls a first electronic switching unit P11. In accordance with the transmitted control signal pattern S11, the first electronic switching unit P11 switches on a residual current IF via a current-limiting resistor R1 by means of a switch P11a. This residual current IF flows via the phase conductor L1 and the protective conductor PE. This residual current IF is detected by the measuring current transformer P9 and evaluated in the RCMB controller P6. The control signal pattern generated by the residual current control unit P61 causes the first electronic switching unit P11 to switch the residual current IF on and off according to the predetermined control signal pattern S11.If a fault current IF corresponding to this control signal pattern S11 is detected by the measuring current transformer P9, and a fault current comparator P62 determines that this detected fault current IF corresponds to the generated control signal pattern S11, the fault current IF is considered to be detected. This, in turn, is considered an indication that a phase line voltage (mains voltage) UL1 (. Fig. 6) prevails, meaning that the switching contact K of the disconnecting device P4 to be tested is (still) closed. If the corresponding switching contact K is to be opened for operational reasons, this indicates a non-functional (opening) behavior of this switching contact K. If, however, the switching contact K is to be closed for operational reasons, the detection of the fault current—which is equivalent to the presence of a mains voltage—can be interpreted as indicating that the protective conductor connection (PE) is intact.

[0049] In Fig. 3 shows an electrical circuit device 2 according to the invention for a three-phase supply line L.

[0050] In extension of the circuit device 2 according to the invention from Fig. 2, the first electronic switching unit P11 has been supplemented in such a way that it has three electronic switches Pl1a, P11b, P11c, wherein each of the three active phase conductors L1, L2, L3 is assigned the respective switch Pl1a, P11b, P11c in order to switch an artificial, passive fault current IFa, IFb, IFc separately for each of the three active phase conductors L1, L2, L3 via the respective current-limiting resistors R2, R3, R4.

[0051] This design also enables the individual generation of a control signal pattern S11 and thus an individually flowing fault current for each active phase conductor L1, L2, L3. In addition, using suitable control signal patterns S11 on the respective phase conductors L1, L2, L3, a frequency measurement and / or phase rotation detection can be performed.

[0052] The Fig. 4 shows an electrical circuit device 2 according to the invention for the three-phase supply line L in a variant.

[0053] Based on the design according to Fig. 3 the first electronic switching unit P11 has been simplified in that it has only one switch P11d, which switches a fault current IFd flowing for all active phase conductors L1, L2, L3 simultaneously via the respective current-limiting resistors R5, R6, R7.

[0054] Fig. Figure 5 shows an electrical circuit device according to the invention for the three-phase supply line L according to the variant according to Fig. 4 extended by a second electronic switching unit P19.

[0055] The second electronic switching unit P19 receives a first control signal S19a from the residual current control unit P61 and / or a second control signal S19b from the system controller P8 to switch a tripping current IA through a current-limiting resistor R11. In contrast to the residual current IFd switched in the first electronic switching unit P11 through the current-limiting resistors R8, R9, R10, this tripping current IA is significantly higher, so that it triggers the residual current device (RCD). Provided that a functional protective conductor (PE) has been detected beforehand, this can ensure safe disconnection of the supply line L.

[0056] Just like the variant according to Fig. 4, the arrangement with individual generation of the control signal pattern S11 according to Fig. 3 can be expanded accordingly with the second electronic switching unit P19.

[0057] This extension can also be used with the second electronic switching unit P19 in conjunction with a single-phase supply line L.

[0058] Fig. Figure 6 shows schematically the generation of the artificial, passive fault current IF.

[0059] Part a of the Fig. Figure 6 shows the waveform of the phase conductor voltages UL1, UL2, UL3. Part b shows the time profile of a control signal pattern S11 generated by the residual current control unit P61 of the RCMB control unit P6. Part c of the Fig. 6. This fault current IF is measured by means of the measuring current transformer P9 and evaluated in the RCMB control P6 with the fault current comparator P62, generating a corresponding fault signal S8. If this fault signal S8 correlates - particularly with regard to its temporal progression - with the control signal pattern S11, as can be seen by comparing the representation in part b and part c of the Fig. 6 is easily visible, it can be assumed that the intentionally generated, artificial, passive fault current IF is actually flowing. This can be used to verify that the switching contact K being tested is still closed and that the protective conductor PE is functioning.

Claims

[1] Electrical switching device (2) for detecting a non-opened switching contact (K) of a switching device (P4) and for detecting a protective conductor interruption in a single-phase or multi-phase electrical supply line (L) with active conductors (L1, L2, L3, N) and a protective conductor (PE), with a differential current monitoring module (RCMB), which has an RCMB controller (P6) for evaluating a measuring signal supplied by a measuring current transformer (P9) and for generating a first shutdown signal (S4a), wherein the measuring current transformer (P9) detects a differential current flowing on the supply line (L), and with a system controller (P8) for generating a second shutdown signal (S4b), wherein the shutdown device (P4) is designed to disconnect the active conductors (L1, L2, L3, N) and has a signal input (P41) for receiving the first shutdown signal (S4a) and the second shutdown signal (S4b), and wherein the system controller (P8) is connected to the RCMB controller (P6) of the differential current monitoring module (RCMB) for receiving an error signal (S8). characterized by , that the RCMB control (P6) has a fault current control unit (P61) for generating a control signal pattern (S11) which controls a first electronic switching unit (P11) for switching an artificial, passive fault current (IF) flowing via one or more of the active conductors (L1, L2, L3, N) and the protective conductor (PE), wherein the switched, artificial, passive residual current (IF) is adjustable so that it can be detected as a residual current by the residual current monitoring module (RCMB), but does not lead to a response of a residual current device (RCD) installed in the supply line (L), wherein the RCMB control (P6) has a signalling device (P63) which signals a detection of the artificial, passive fault current (IF) and thus the presence of the functional protective conductor (PE) as well as a mains voltage (UL1, UL2, UL3) and wherein the RCMB controller (P6) has a fault current comparator (P62) which compares a fault current curve detected by the measuring current transformer (P9) with the fault current curve expected on the basis of the control signal pattern (S11) in order to reliably detect the switched, artificial, passive fault current (IF). [2] Electrical circuit device (2) according to claim 1, characterized bythat the residual current control unit (P61) is designed to generate a first control signal (S19a) to a second electronic switching unit (P19) in order to switch an artificial tripping current (IA) for tripping the residual current device (RCD), provided that the functional protective conductor (PE) has been detected beforehand. [3] Electrical circuit device (2) according to one of claims 1 or 2, characterized by the system controller (P8) is designed to generate a second control signal (S19b) to a / the second electronic switching unit (P19) in order to switch an artificial tripping current (IA) for tripping the residual current device (RCD). [4] Electrical circuit device (2) according to one of claims 1 to 3, characterized byin that the first electronic switching unit (P11) in the case of a 3-phase supply line (L) has three electronic switches (P11a, P11b, P11c), wherein each of the three active phase conductors (L1, L2, L3) is assigned an electronic switch (P11a, P11b, P11c) in order to switch an artificial, passive fault current (IFa, IFb, IFc) separately for each of the three active phase conductors (L1, L2, L3). [5] Electrical circuit device (2) according to claim 4, characterized by that the RCMB control (P6) has a measuring device (P64) for measuring the mains frequency and / or for detecting the rotating field direction by means of suitable control signal patterns (S11) on the active phase conductors (L1, L2, L3). [6] Electrical circuit device (2) according to one of claims 1 to 3, characterized bythat the first electronic switching unit (P11), in the case of a 3-phase supply line (L), has an electronic switch (P11d) which switches a common, artificial, passive fault current (IFd) for the three active phase conductors (L1, L2, L3). [7] Method for detecting a non-opened switching contact (K) of a disconnecting device (P4) and for detecting a protective conductor interruption in a single-phase or multi-phase electrical supply line (L) with active conductors (L1, L2, L3, N) and a protective conductor (PE), wherein the supply line is equipped with a residual current monitoring module (RCMB) which has an RCMB controller (P6) for evaluating a measuring signal supplied by a measuring current transformer (P9) and for generating a first disconnection signal (S4a), wherein the measuring current transformer (P9) detects a residual current flowing on the supply line (L), and the supply line is equipped with the disconnecting device (P4) for disconnecting the active conductors (L1, L2, L3, N) and with a system controller (P8) for generating a second disconnection signal (S4b), comprising the method steps: - Generating a control signal pattern (S11) in a residual current control unit (P61) of the RCMB control (P6) - controlling a first electronic switching unit (P11) with the control signal pattern (S11) for switching an artificial, passive fault current (IF) flowing via one or more of the active conductors (L1, L2, L3, N) and the protective conductor (PE), - Setting the switched, artificial, passive residual current (IF) so that it can be detected as a residual current by the residual current monitoring module (RCMB), but does not lead to a response of a residual current device (RCD) installed in the supply line (L), - Signaling a detected artificial, passive fault current (IF), - Comparing a fault current curve detected by the measuring current transformer (P9) with the fault current curve expected on the basis of the control signal pattern (S11) by means of a fault current comparator (P62) in the RCMB control (P6) in order to reliably detect the switched, artificial, passive fault current (IF). [8] Method according to claim 7, characterized by Disconnecting the active conductors (L1, L2, L3, N) by means of the disconnection device (P4) via the first disconnection signal (S4a) or the second disconnection signal (S4b) if the artificial, passive fault current (IF) is signaled. [9] Method according to claim 7 or 8, characterized by Generating a first control signal (S19a) to a second electronic switching unit (P19) by means of the residual current control unit (P61) in order to switch an artificial tripping current (IA) for tripping the residual current device (RCD), provided that the functional protective conductor (PE) was previously detected. [10] Method according to one of claims 7 to 9, characterized by Generating a second control signal (S19b) to a / the second electronic switching unit (P19) by means of the system controller (P8) in order to switch an / the artificial tripping current (IA) for tripping the residual current device (RCD). [11] Method according to one of claims 7 to 10, characterized by that in the case of a 3-phase supply line (L) an artificial, passive fault current (IFa, IFb, IFc) is switched separately for each of the three active phase conductors (L1, L2, L3), wherein an electronic switch (P11a, P11b, P11c) is assigned to each of the three active phase conductors (L1, L2, L3) in the first electronic switching unit (P11). [12] Method according to claim 11, characterized by Measuring a mains frequency and / or detecting a rotating field direction in a measuring device (P64) of the RCMB control (P6) by means of suitable control signal patterns (S11) on the active phase conductors (L1, L2, L3). [13] Method according to one of claims 7 to 10, characterized bythat in the case of a 3-phase supply line (L) for the three active phase conductors (L1, L2, L3) a common artificial, passive fault current (IFd) flowing via the protective conductor is switched by means of exactly one electronic switch (P11d).

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