阅读说明：本技术 供电系统的绝缘电阻和保护导体电阻监控的组合监控设备 (Combined monitoring device for insulation resistance and protection conductor resistance monitoring of power supply system ) 是由 朱利安·埃尔克 迈克尔·卡默 温弗里德·莫尔 于 2020-09-24 设计创作，主要内容包括：本发明涉及一种用于在包括接地供电系统和非接地供电系统的供电系统中的绝缘电阻监控和保护导体电阻监控的组合监控设备(20),组合监控设备包括耦接电路(21),用于经由耦接点(28)耦接到接地供电系统的一个或多个有源导体(L1,L2,L3,N),组合监控设备包括有源监控设备(22),包括用于监控供电系统的非接地网络状态中的绝缘电阻(Rf)的第一操作模式和用于监控供电系统的接地网络状态中的保护导体电阻(Rpe)的第二操作模式,以及组合监控设备包括评估单元(25),根据非接地或接地网络状态在第一操作模式和第二操作模式之间是可切换的,并且被配置用于在第一操作模式中测试绝缘电阻(Rf)和在第二操作模式中测试保护导体电阻(Rpe)。(The invention relates to a combination monitoring device (20) for insulation resistance monitoring and protection conductor resistance monitoring in a power supply system comprising a ground power supply system and a non-ground power supply system, the combination monitoring device comprising a coupling circuit (21) for coupling to one or more active conductors (L1, L2, L3, N) of the ground power supply system via a coupling point (28), the combination monitoring device comprising an active monitoring device (22) comprising a first operating mode for monitoring an insulation resistance (Rf) in a non-ground network state of the power supply system and a second operating mode for monitoring a protection conductor resistance (Rpe) in a ground network state of the power supply system, and the combination monitoring device comprising an evaluation unit (25) being switchable between the first operating mode and the second operating mode depending on the non-ground or ground network state and being configured for testing the insulation resistance (Rf) in the first operating mode and for testing the protection conductor resistance (Rpe) in the second operating mode Guard conductor resistance (Rpe).)

1. A combination monitoring device (20, 30, 40) for insulation resistance monitoring and protection conductor resistance monitoring in a power supply system comprising a grounded (6) and an ungrounded (2, 4) power supply system, the combination monitoring device (20, 30, 40) comprising:

a coupling circuit (21), the coupling circuit (21) being for coupling to one or more active conductors (L1, L2, L3, N) of the ground power supply system (6) via a coupling point (28);

an active monitoring device (22, 32, 42), the active monitoring device (22, 32, 42) comprising a first operating mode for monitoring the insulation resistance (Rf) in the non-grounded network state of the power supply system (2, 4, 6) and a second operating mode for monitoring the protection conductor resistance (Rpe) in the grounded network state of the power supply system (2, 4, 6), and

an evaluation unit (25), the evaluation unit (25) being switchable between the first and second operation modes depending on the non-grounded or grounded network state and being configured for testing the insulation resistance (Rf) in the first operation mode and the protection conductor resistance (Rpe) in the second operation mode.

2. Combined monitoring device (20, 30, 40) according to claim 1,

the active monitoring device (22, 32, 42) comprises a switching signal input (26) for switching between the first and the second operation mode by means of an external switching signal.

3. Combined monitoring device (20, 30, 40) according to claim 1 or 2,

the evaluation unit (25) is configured for testing in the first operation mode whether a settable insulation resistance threshold (Rflim) has been fallen below and for testing in the second operation mode whether a settable protection conductor resistance threshold (Rpelim) has been exceeded.

4. The combination monitoring device (20) according to any one of claims 1 to 3, further comprising:

-a switching device (29), said switching device (29) being connected upstream of said coupling point (28) for disconnecting the active conductors (L1, L2, L3, N) of the grounded power supply system (6) to prevent the grounded power supply system (6) from being operated in case of a determined impermissible low insulation resistance (Rf) in the non-grounded power supply system (2, 4).

5. The combination monitoring device (30) according to any one of claims 1 to 3, further comprising:

a first load relay (35), the first load relay (35) being connected upstream of the coupling point (28) for disconnecting the active conductor (L1, L2, L3, N), and

a second load relay (36), the second load relay (36) being connected downstream of the coupling point (28) for disconnecting the active conductor (L1, L2, L3, N).

6. The combination monitoring device (40) according to any one of claims 1 to 3, further comprising:

a load relay (44), the load relay (44) for disconnecting the active conductor (L1, L2, L3, N), and

a transfer relay (45), the transfer relay (45) connecting the active conductor (L1, L2, L3, N) to the coupling circuit (21) upstream of the load relay (44) via a first coupling point (28a) for monitoring the grounded power supply system (6) or connecting the active conductor (L1, L2, L3, N) to the coupling circuit (21) downstream of the load relay (44) via a second coupling point (28b) for monitoring the ungrounded power supply system (2, 4).

7. The combination monitoring device (30, 40) of claim 5 or 6, further comprising:

a voltage measurement device (34), the voltage measurement device (34) being configured to measure a switching voltage or switching voltages in the ground power supply system (6) and to automatically switch the evaluation unit (25) into the second operating mode to monitor the protective conductor resistance (Rpe) if the switching voltage or a switching voltage which has been derived from a combination of a plurality of switching voltages exceeds a settable switching voltage threshold and to switch back into the first operating mode for insulation monitoring when a switching voltage threshold is undershot.

8. Combined monitoring device (30, 40) according to claim 7,

the corresponding measured switching voltage is either a conductor-conductor voltage via a measurement point between two arbitrary active conductors (L1, L2, L3, N) of the ground supply system (6) or a conductor-ground voltage via a measurement point between an arbitrary active conductor (L1, L2, L3, N) of the ground supply system (6) and the protection conductor (PE).

Technical Field

The invention relates to a combined monitoring device for insulation resistance monitoring and protection conductor resistance monitoring in a power supply system comprising a grounded power supply system and a non-grounded power supply system.

Background

For operating the electrical consumer and the operating device (in the following the term consumer will be used as a generic term for electrical consumers and operating devices), appropriate protective measures for protection against electric shocks will be taken-for example, as defined in the international standard IEC 61140.

In view of this, when the consumer is operated with a rechargeable energy storage (accumulator/battery or capacitor) and a dangerously high system voltage, protective measures are required when the consumer is operated in an ungrounded network state on the one hand and in a grounded network state on the other hand.

During operation in the non-grounded network state-for example when driving an electric vehicle-there is no galvanic connection to the external power supply, and the electrical installation in operation-for example the electrical system (battery lead) of the electric vehicle-can be regarded as a (mobile) non-grounded power supply system with an energy store as a charge of the power supply.

Each non-earthed power supply system requires suitable insulation monitoring as a protective measure according to the standard IEC 61557-8. According to this specification, an Insulation Monitoring Device (IMD) is mandatory, which continuously monitors the insulation resistance (the resistance of the network to be monitored, including the resistance of all consumers to the ground connected thereto).

In the traveling of the electric vehicle, the insulation resistance is monitored, for example, via an insulation monitoring device installed in the electric vehicle.

The insulation of the power supply system can be monitored via active or passive measuring methods.

In the active measurement method examined herein, a measurement voltage (measurement signal) is applied to the network to be monitored by means of a monitoring device acting as an active insulation monitoring device. The measurement current resulting from the measurement voltage flows through the individual insulation resistances Rf + and Rf- (for example in a direct current network) and is returned via a ground connection (usually a protective conductor, or in the case of an electric vehicle, the vehicle body) and evaluated in the insulation monitoring device. If the insulation resistance calculated from the remeasured measurement current is below the insulation resistance threshold (response value) specified for the specific installation, an alarm signal is triggered. This also allows the identification of symmetrical insulation faults, in contrast to passive measurement methods which do not provide a separately generated measurement signal.

During operation in the ground network state, for example upon charging, the consumer is galvanically connected to the ground supply system. For this network configuration of the grounding network, an effective protection conductor (PE conductor) of the grounding system connecting all conductive touchable parts to the ground power supply system is installed as protection against electrocution according to the IEC60364-41-1 standard.

The protection earth connection is to be continuously monitored with respect to its continuity. When operating in the grounded network state, if an insulation fault occurs, the fault current thus generated discharges via the protective conductor and prevents dangerously high contact voltages. The condition in this case is that the protection conductor is connected to the earth system of the power supply system with a sufficiently low impedance. To ensure such a sufficiently low impedance, the protection conductor may be monitored by appropriate protection conductor resistance measurement or protection conductor impedance measurement, the resistance/impedance being measured via the central earth point and the active conductor (outer conductor or neutral conductor) of the earth supply system. The measurement of the resistance and/or impedance of the guard conductor also comprises in particular an active conductor as return conductor. This allows assuming that the active conductor has a low impedance. Therefore, in the following, when the term PE resistance or protection conductor resistance is used, the entire loop resistance is referred to.

It is known from the prior art to monitor two safety-relevant network parameters, the insulation resistance and the protection conductor resistance, using separate monitoring devices which act separately from one another.

In the field of electric drives, it is accordingly specified by the standard IEC 61851-1 that an additional signal contact point CP (control pilot) is used as an auxiliary conductor for monitoring the protective conductor when charging the energy store of the electric vehicle. A disadvantage, however, is that no statement is made as to the quality of the protected conductor connection, i.e. the resistance of the PE conductor, as low as possible.

A disadvantage of the solutions known from the prior art is that for monitoring the insulation and the protective conductor, separate, individually acting monitoring devices are required in each case. This results in high manufacturing and installation costs and a large installation space. In particular in the field of electric drives, the signal contacts required for each standard for monitoring the protective conductor must also be provided when connecting the consumer to the power supply system.

Disclosure of Invention

It is therefore an object of the present invention to design a monitoring device that enables monitoring of the protection conductor resistance of an earthed power supply system and the insulation resistance of an ungrounded power supply system in an efficient manner with respect to cost, energy consumption, installation space and weight.

According to the invention, this object is achieved by having a combined monitoring device for monitoring the insulation resistance and the protection conductor resistance, comprising: coupling circuitry for coupling to one or more active conductors of the ground power supply system via a coupling point; an active monitoring device comprising a first operating mode for monitoring insulation resistance in an ungrounded network state of the power supply system and a second operating mode for monitoring protection conductor resistance in a grounded network state of the power supply system, and an evaluation unit being switchable between the first operating mode and the second operating mode depending on the ungrounded network state or grounded network state and being configured for testing the insulation resistance in the first operating mode and the protection conductor resistance in the second operating mode.

The above design describes the first embodiment (basic configuration), and its features are also part of the second and third embodiments.

The invention is based on the finding that the monitoring method to be used is applied between the active conductor and the protection conductor system/ground/body of the corresponding power supply system for two monitoring tasks: insulation monitoring is carried out on the one hand when the consumer is disconnected from the supply earth supply system (for example, non-earth network state/operation when driving an electric vehicle), and protection conductor monitoring is carried out on the other hand when connected to the earth supply system (for example, earth network state/operation when charging). In both operating cases, the resistance can be detected by applying a measurement voltage: in the non-grounded operation, the resistance to be detected is an insulation resistance, and in the grounded operation, it is a protection conductor resistance.

According to the prior art, the insulation monitoring device is installed in an ungrounded power supply system, for example in a battery network of an electric vehicle, which must be switched off if this network is galvanically connected to a grounded power supply network. Otherwise, the insulation monitoring device will be triggered, since the connection of the non-grounded network to the grounded network, e.g. by inserting a charging cable, will result in the non-grounded network being converted into a grounded network and the measured insulation resistance will become zero.

Since the installed insulation monitoring device thus stops the service for detecting the insulation resistance in the grounding operation, the insulation monitoring device can be used as an active monitoring device for monitoring the continuity (low impedance) of the protection conductor envisioned by the present invention during the grounding operation.

These considerations lead to the subject of the invention being a combined monitoring device which switches or is switched to the required protection function (monitoring insulation resistance or protection conductor resistance) depending on the network to be monitored, i.e. adapts to the grounded/ungrounded network configuration and thus ensures protection against electric shocks across all functions in grounded and ungrounded operation (e.g. at charging or in operational driving operation).

To this end, the combination monitoring device is arranged above the coupling circuit for coupling to one or several active conductors of the ground supply system via the coupling point and above the active monitoring device.

The active monitoring device has a first operating mode for monitoring the insulation resistance in an ungrounded network state of the power supply system and a second operating mode for monitoring the protection conductor resistance in a grounded network state of the power supply system, and comprises an evaluation unit which can be switched between the first operating mode and the second operating mode depending on the ungrounded or grounded network state and which is configured for testing the insulation resistance in the first operating mode and for testing the protection conductor resistance in the second operating mode.

By combining both uses in a combined monitoring device or by using a device which implements this combined monitoring device in a plurality of ways, costs, energy consumption and weight can be reduced in an advantageous manner and there is less need for installation space. In the case of two monitoring devices which hitherto have been required to function separately and independently of one another, the requirements for electrical safety can be met by only one (combined) device.

For example, these factors play an increasingly important role in the automotive industry. The combination monitoring device may serve another market segment and may generate a competitive advantage.

A further advantage emerges in view of the electric drive, so that no additional signal contacts for monitoring the resistance of the protective conductor are required. In addition to charging stations and home charging stations, electric vehicles can therefore be charged at almost all common electric coupler junctions.

When using a combination monitoring device it is not important whether the grounded supply network is a supply network according to the IEC standard (50 Hz: AC 230V; 3AC 400V; 3NAC 400V/230V) or the UL standard (60 Hz: AC 120V; 2AC 240V).

The combination monitoring device according to the invention can be used in all application environments in general, in which a grounded network can be switched to an ungrounded network and vice versa in a targeted manner. This can generally take place in all possible ungrounded power supply systems, such as uninterruptible power supplies, micro grids or in the field of electric drives.

In another embodiment, the active monitoring device comprises a switching signal input for switching between the first and second operation mode by means of an external switching signal.

The switching action by means of the manually or automatically generated external switching signal is therefore carried out in accordance with the monitoring task and thus depending on the network state of the power supply system to be monitored.

Advantageously, the evaluation unit is configured for testing in the first operating mode whether a settable insulation resistance threshold is undershot and for testing in the second operating mode whether a settable protection conductor resistance threshold is exceeded.

Depending on the monitoring task, the settable resistance threshold is interpreted in the evaluation unit as an insulation resistance threshold or a protection conductor resistance threshold, and the settable resistance threshold is tested with regard to checking whether the identified insulation resistance or protection conductor resistance is below or exceeds the threshold.

In addition, the combination monitoring device comprises a switching device connected upstream of the coupling point for disconnecting the active conductor of the earthed power supply system to prevent the earthed power supply system from being operated in case an inadmissibly low insulation resistance is detected in the non-earthed power supply system.

According to a second embodiment, the combination monitoring device advantageously comprises a first load relay connected upstream of the coupling point with respect to a direction determined by the inputs and outputs of the combination monitoring device for disconnecting the active conductor of the earthed power supply system, and a second load relay connected downstream of the coupling point for disconnecting the active conductor of the earthed power supply system.

The first load relay and the second load relay enable the network to be tested to be operated alternately on the combination monitoring device, while the other network is disconnected. Thus, the disconnection of the network to be tested is determined by the switching states of the first and second load relays.

According to an advantageous third embodiment, the combination monitoring device comprises a load relay for disconnecting an active conductor of the earth supply system and a changeover relay for connecting the active conductor via a first coupling point to a coupling circuit upstream of the load relay for monitoring the earth supply system or via a second coupling point to a coupling circuit downstream of the load relay for monitoring the non-earth supply system.

As an alternative to the design of the second embodiment with two load relays, only one load relay may operate the network to be tested together with the changeover relay and disconnect the surviving network. To this end, the conversion relay is connected to the active conductor of the ungrounded power supply system via a first/second coupling point upstream/downstream of the load relay, in order to connect the corresponding network to the coupling circuit.

The use of a changeover relay proves to be an even more advantageous alternative in terms of cost and installation space compared to an embodiment with two load relays, since the load relays need to switch the load current compared to the changeover relay.

Preferably, the combination monitoring device comprises a voltage measuring device for measuring one or several switching voltages in the ground supply system and for automatically switching the evaluation unit-and the upper active monitoring device-to a second operating mode for monitoring the resistance of the protective conductor when the switching voltage or a switching voltage derived from combining a plurality of switching voltages exceeds a settable switching voltage threshold value and to a first operating mode for insulation monitoring when the switching voltage threshold value is undershot.

Complementary to the switching option input via the switching signal by means of the external switching signal, the operating mode can be automatically switched to the second operating mode PE monitoring internal in the combination monitoring device. To this end, a voltage measuring device measures at least one switching voltage in the supply-grounded power supply system. If the measured switching voltage or the switching voltage resulting from combining a plurality of switching voltages exceeds a settable switching voltage threshold, it can be assumed that the earthed power supply system is connected to its grid voltage and that the voltage measuring device triggers the evaluation unit to switch to the second operating mode PE monitoring. If the switching voltage threshold is subsequently undershot, the evaluation unit preferably switches back to the first operating mode insulation monitoring after a settable delay time (hysteresis).

The corresponding measured switching voltage is the conductor-conductor voltage via the measurement point between two arbitrary active conductors of the ground supply system or the conductor-ground voltage via the measurement point between an arbitrary active conductor and the protection conductor of the ground supply system.

Drawings

Further advantageous embodiment features emerge from the description below and the drawings, which describe a preferred embodiment of the invention using examples. In the following, the following description is given,

figure 1 shows a monitoring system for insulation resistance monitoring and protection conductor resistance monitoring according to the prior art,

figure 2 shows a combination monitoring device according to the invention as a first embodiment (basic configuration),

figure 3 shows a second embodiment of a combined monitoring device according to the invention with voltage measurement and two load relays,

FIG. 4 shows a third embodiment of a combined monitoring device according to the invention with a voltage measurement, a load relay and a changeover relay, an

Fig. 5 shows the use of a combination monitoring device according to the invention based on the prior art.

Detailed Description

Fig. 1 shows the structure of a monitoring system for insulation resistance monitoring and protection conductor resistance monitoring known from the prior art in a functional block diagram.

In the ground network state, the ungrounded power supply system 2 (ungrounded network) is connected as a battery network 4 via a connecting cable 8 to the ground power supply network 6 (grounded network), by means of which connection the battery network 4 with the rechargeable electrical energy store 10 (battery) is grounded via a central grounding point ZEP and is converted into a consumer of the ground power supply system 6. The case resistance Rg of the consumer case to ground (central ground point ZEP) is generally considered to be a high impedance.

As an example, the ground supply system 6 is configured as a supply three-phase network with active conductors L1, L2, L3 and N and a protection conductor PE (PE conductor). The guard conductor PE has a guard conductor resistance Rpe. The continuity of the protection conductor PE must be ensured and therefore the protection conductor resistance Rpe must have a sufficiently low impedance.

The additional signal contacts 16, as specified for example in the field of electric drives according to the IEC 61851-1 standard, are used for protection conductor monitoring during operation in the ground network state. Via this signal contact 16, a defined signal 18 is sent from the supply infrastructure (e.g. a charging station of the ground supply system 6) to the supplied consumer (e.g. an electric vehicle) and returned via the PE conductor PE. The presence of the PE conductor PE is tested by means of the returned signal. However, in the example of an electrical drive, further data is exchanged via this signal contact and the PE conductor. It proves to be disadvantageous that no conclusions can be drawn about the quality of the protective conductor resistance Rpe, since only the presence of the protective conductor PE ("PE present" or "PE not present") can be determined.

In the non-grounded network state, during operation, the insulation resistance is monitored via a separately arranged active insulation monitoring device 14 (IMD).

Thus, according to the prior art, the need for two devices (one for monitoring the protection conductor resistance and the other for monitoring the insulation resistance) has the resulting disadvantages with regard to cost, energy consumption and installation space.

Fig. 2 to 4 below show in functional block diagrams three embodiments of a combined monitoring device 20, 30, 40 according to the invention, which can be connected together with the earthed 6 and non-earthed 2, 4 power supply system according to fig. 5.

The combination monitoring devices 20, 30, 40 each comprise a coupling circuit 21 with a coupling resistance Rc for coupling to the active conductors L1, L2, L3, N of the ground supply system 6 via a coupling point 28. The combination monitoring devices 20, 30, 40 each also comprise an active monitoring device 22, 32, 42, so that, based on the active measurement method, during the active measurement method a measurement voltage is superimposed on the non-grounded network 2 by means of the symbolically shown measurement voltage source 23, and during the active measurement method a resulting measurement current is detected via a voltage drop at the measurement resistance within the active monitoring device 22, 32, 42 for determining the insulation resistance Rf or, in a modified function according to the invention, for determining the protection conductor resistance Rpe.

The functionally illustrated coupling circuit 21 can also be a structural part of the active monitoring device 22, 32, 42.

The active monitoring devices 22, 32, 42 each comprise an evaluation unit 25, the evaluation unit 25 being configured to be switchable between a first operating mode and a second operating mode. The first operating mode is used to identify whether the detected insulation resistance Rf is below an insulation resistance threshold Rflim, and the second operating mode is used to identify whether the detected guard conductor resistance Rpe exceeds a guard conductor resistance threshold Rpelim.

The difference between the two modes of operation can be summed by means of the following characteristics:

insulation monitoring mode (for non-grounded networks):

high resistance value (of detected insulation resistance) good state

Low resistance value (of detected insulation resistance) bad state

Alarm > when below the insulation resistance threshold Rflim

PE monitoring mode (for grounded networks):

high resistance value (of detected protective conductor resistance) bad state

Low resistance value (of detected protection conductor resistance) good state

Alarm signal > when the protection conductor resistance threshold Rpelim is exceeded,

the threshold value between the high resistance value and the low resistance value is specified by the corresponding threshold value Rflim, Rpelim according to the specifications of each facility.

Therefore, for switching the operating mode, it is necessary to "invert" only the decision logic of the evaluation unit 25 and to adjust the threshold values depending on the network configuration and the resulting monitoring task.

With all three embodiments of the combination monitoring device 20, 30, 40, the operating mode can be switched by means of an external switching signal via the switching signal input 26 of the active monitoring device 22, 32, 42; in addition, with embodiments 30, 40, as shown in fig. 3 and 4, the operating mode can be switched automatically via the voltage measuring device 34.

For transmitting the alarm signal, the evaluation unit 25 comprises at least one alarm signal output 27. For example, the alarm signal output 27 may switch an external relay to galvanically disconnect the battery network 4 from the connected ground power supply system 6. A number of alarm signal outputs 27 provide further possibilities, which may be configured, for example, analog and digital and represent different alarm levels (pre-alarm, master alarm).

In fig. 2, a combination monitoring device 20 is schematically shown in a first embodiment. In this case, all-pole coupling (to all active conductors L1, L2, L3, N) via a coupling resistor Rc is taken as an example. Generally, a unipolar coupling is also sufficient, as it is used for the other embodiments of the combined monitoring devices 30, 40 in fig. 3 and 4. Then, for measuring the protection conductor resistance, whether the unipolar coupling is on the outer conductor L1, L2, L3 or on the neutral conductor N is irrelevant. However, for voltage measurement and accompanying automatic switching, it must be ensured that the combination monitoring device 20 is coupled to the outer conductors L1, L2, L3.

In this first embodiment, the operation mode is switched only by the external switching signal via the switching signal input 26.

In order to disconnect the active conductors L1, L2, L3, N of the grounded power supply system 6, a switching device 29 is connected upstream of the coupling point 28 to prevent the grounded power supply system 6 from operating in case an impermissibly low insulation resistance Rf is detected in the ungrounded power supply systems 2, 4.

Fig. 3 shows a combination monitoring device 30 according to a second exemplary embodiment of the invention, which has a symbolically shown voltage measuring device 34, a first load relay 35 and a second load relay 36.

A first load relay 35 is connected upstream of the coupling point 28 with respect to the direction determined by the input and output of the combination monitoring device 30 for disconnecting the active conductor of the earth supply system 6, and a second load relay 36 is connected downstream of the coupling point 28 for disconnecting the active conductor of the earth supply system 6.

The operating mode is switched automatically by measuring the voltage by means of the voltage measuring device 34, but may also be triggered by an external switching signal as in the first embodiment.

When switching is caused by voltage measurement, if a voltage exceeding a settable switching voltage threshold is measured between two arbitrary conductors L1, L2, L3, N, the second load relay 36 is opened and the first load relay 35 is closed. Thus, the non-grounded network 2 is disconnected from the active monitoring device 32 and the active monitoring device 32 is coupled to the ground supply system 6 via the coupling circuit 21 for protection conductor monitoring. The evaluation unit 25 operates in the PE monitoring mode and detects the protective conductor resistance Rpe. If the protection conductor resistance Rpe is below the previously defined protection conductor resistance threshold value and if the previously detected insulation resistance Rf exceeds the defined insulation resistance threshold value Rflim before the second load relay 36 is opened, the second load relay 36 is closed again and the non-grounded power supply system 2, 4 connected to the connection OUT _ x is therefore grounded.

If a voltage below the switching voltage threshold is measured, the first load relay 35 is opened and the insulation monitoring mode is reactivated, since it can be assumed that the connection to the ground supply system 6 has been interrupted. In the insulation monitoring mode, when the insulation resistance threshold Rflim is undershot, an alarm signal is given via the alarm signal output 27, for example to disconnect the battery 10 (fig. 5).

The switching voltage threshold may generally be set to any threshold value, which corresponds to a safety target and is specific to the installation, and may for example have a safety ultra-low voltage 50 of 50V in terms of protective measures.

In addition to signaling an alarm, the first load relay 35 is also opened in the PE monitoring mode. The non-grounded network 4 is now available again by opening the first load relay 35. The second exemplary embodiment therefore has the advantage over the first exemplary embodiment that, in the event of a fault, when the protection conductor resistance threshold (Rpelm) is exceeded, the power electronics in the load are then galvanically disconnected from the supply network 6.

Starting from the evaluation unit 25, the first/second load relay 35/36 is controlled by the active monitoring device 32 by means of a first/second control signal line 37/38.

Fig. 4 shows a combination monitoring device 40 in a third embodiment according to the invention.

In this embodiment the combi monitoring device 40 works according to the same principle as the second embodiment, except that the second load relay 36 (fig. 3) is not required and the network to be tested 2, 4 (not grounded) or 6 (grounded) is operated alternately by a (central) load relay 44 together with a transfer relay 45.

According to the corresponding operating mode, the coupling resistance Rc of the coupling circuit 21 is coupled upstream of the load relay 44, shown on the left side of the load relay 44, for PE monitoring via a first coupling point (28a), or downstream of the load relay 44, shown on the right side of the load relay 44, for insulation monitoring via a second coupling point (28 b). The indication of the alarm signal is given in the same manner as in the second embodiment.

The advantages with respect to installation space, power consumption and cost obtained by omitting the second load relay 36 (fig. 3) become more apparent when the active monitoring device 42 is coupled to one pole.

Starting from the evaluation unit 25, the load relay 44/switching relay 45 is controlled by the active monitoring device 32 by means of a control signal line 47/ac signal line 48.

IN fig. 5, the use of a combination monitoring device 20, 30, 40 is shown using the example of a consumer which is not galvanically disconnected and has an integrated rechargeable electrical energy store 10, the combination monitoring device 20, 30, 40 being usable IN one of the three embodiments 20, 30, 40 for shared insulation resistance and loop resistance monitoring and being connectable on the input side to the active conductors L1, L2, L3, N via the connections IN _ L1, IN _ L2, IN _ L3 and on the output side to the active conductors L1, L2, L3, N via the connections OUT _ L1, OUT _ L2, OUT _ L3, OUT _ N.

The insulation resistance Rf of the ungrounded battery network 4, which is formed by the individual insulation resistances Rf + and Rf-, is monitored with respect to the electrically conductive housing of the consumer, for example the vehicle body, when operating in an ungrounded network state, for example when driving an electric vehicle.

However, in the case of a ground network state, for example when charging an electric vehicle, the ungrounded battery network 4 becomes a consumer of the normally grounded power supply network 6 via a connection which is not galvanically disconnected, so that a complete ground network is produced. This is the operating means of protection class 1 according to IEC 60140. This means that protection against electrocution must be ensured by connecting the PE conductor PE (i.e. in this case the conductive housing of the consumer) to the ground protection potential of the grounded supply network 6, in which case the state of the protection conductor PE (i.e. its low impedance) is critical to the effectiveness of the protection measures.

Thanks to the combination monitoring device according to the invention, a low impedance connection to ground potential (center ground point ZEP) can be determined without additional auxiliary conductors and, in addition, the actual resistance value of the protection conductor resistance Rpe can be determined by measuring the loop resistance of L1, L2, L3 and N in the grounding operation (depending on the type and number of active conductors L1, L2, L3, N and the type of coupling of the supply ground supply system 6), e.g. in comparison to an electric drive, via the protection conductor resistance Rpe back to the vehicle.