AU3791700A

AU3791700A - Monitoring system for low-voltage switch gear

Info

Publication number: AU3791700A
Application number: AU37917/00A
Authority: AU
Inventors: Kurt Portschy; Peter Scheibenreiter; Martin Schweikhart
Original assignee: M Schneider Schaltgeratebau und Elektroinstallationen GmbH
Current assignee: M Schneider Schaltgeratebau und Elektroinstallationen GmbH
Priority date: 1999-06-04
Filing date: 2000-06-05
Publication date: 2000-12-07
Also published as: EP1058283A2; EP1058283A3; AT409675B; ATA100099A

Description

rIUU/U I I S/5/Ii1 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: MONITORING SYSTEM FOR LOW-VOLTAGE SWITCH GEAR The following statement is a full description of this invention, including the best method of performing it known to us 1 M. Schneider, Schaltgeraetebau und Elektroinstallationen Gesellschaft m.b. H Monitoring system for low voltage switchgear The invention relates to a monitoring system for low voltage switchgear with integrated overload and short circuit protection, such as strips, holders, and fused interrupters, and a process for acquiring and evaluating the operating voltages of the phases to be monitored with protective devices, such as fuses.

Typical operating voltages of this low voltage switchgear are defined in standard IEC 38.

In the course of monitoring low voltage switchgear, efforts are made to acquire and evaluate, as comprehensively and accurately as possible, the operating voltage with as little cost as possible, i.e. as few measurement points and as little cabling 20 as possible, both with respect to current operating parameters and also failure of one or more phases or interruption of one or more phases by damage in the network, for which reason the protective element, for example the fuse, shuts off.

eeoc In this invention this object is achieved by measurement points which are provided in front of and following the protective S devices, for example fuses, of the phases to be monitored, and a measurement and evaluation unit which is connected to the measurement points, and a control unit which is connected to the measurement and evaluation unit, on which information about the type of network and/or a choice of the phases to be monitored can be set.

Because there is one measurement point in front of and following each protective device of a phase to be monitored, both the phase voltage according to its level and variation as well as the 2 difference voltage present over the protective device can be easily acquired, this type of voltage acquisition being independent of the feed direction. In for example a three-phase system therefore six measurement points are enough, two for each phase, in order to obtain a host of power data of the system and information on the failure of one or more phases or shut-off of one or more protective devices.

Since there are a host of different types of networks, to the extent the operating mode, type of current, type of voltage and voltage level are concerned, and for example in multiphase systems for the most varied reasons all phases are not or cannot always be monitored, the focus is on devising as much as possible only a single monitoring system which can be easily adapted to the respective type of network or which allows a simple choice of certain phases of a multiphase network which are to be monitored.

To achieve this object the invention uses a control unit on which information about the type of voltage system and/or the phases to be monitored can be set.

The initial object is furthermore achieved by a process for acquiring and evaluating the operating voltage of the phases to be monitored with protective devices, for example, fuses, which process is characterized in that the operating voltage relative to ground on one side of the protective device and the difference voltage over the protective device of each phase to be monitored S. are acquired, that these voltages are sent to a measurement and evaluation unit and that these measured actual values of the voltages and/or the values computed from them by the measurement and evaluation unit are compared in the measurement and evaluation unit to the setpoints.

With this process both the phase voltage according to its level and variation and also the difference voltage present over the 3 protective device, for example the fuse, can be easily acquired, this type of voltage acquisition in turn being independent of the feed direction.

In the process as claimed in the invention it is likewise preferred that via a control unit information about the type of network and/or a selection of the phases to be monitored can be set, since this allows adaptation of a standardized monitoring system to different types of networks and simple selection of certain phases of a multiphase network which are to be monitored.

In one embodiment of the invention it is provided that the control unit has switches which are assigned to the measurement and evaluation unit. Ideally the system is designed such that one switch is assigned to each phase. If it is assumed that conventionally no more than three phases need be monitored, a monitoring system which can be used as universally as possible therefore has three switches, depending on the number of phases which are present or which are to be monitored the switch which is assigned 20 to the respective phase being turned on.

C. e Furthermore, there can be a switch for the classification of the type of voltage which for example enables differentiation between the three-phase current on the one hand and direct and alternating current on the other, so that a uniform monitoring system or device can also be used for these different types of voltages.

o *X In engineering it is becoming more and more common to transmit measurement data or operating data from devices of any type via bus systems to network control centers or mainframe computers; this is also possible for the data which have been evaluated or acquired by the monitoring system as claimed in the invention.

Alternatively, it can therefore be provided that the control unit, for example a computer, is connected via the bus line to the measurement and evaluation unit. The information or control 4 parameters relating to the type of voltage system and/or the phases to be monitored are set in this embodiment in a control center which is connected via the bus system to the measurement and evaluation unit.

When two or more monitoring systems as claimed in the invention are combined into a bus system, it is necessary to provide a terminal resistance in the monitoring system which is located at the end of the data line. To enable simple switching towards and away from this terminal resistance, it can be provided in another sequence that there is one switch for one terminal resistance of the bus system.

To further increase the flexibility of the monitoring system it 15 can be provided that the measurement and evaluation unit is voltage-supplied separately and that it measures and evaluates the operating voltage of the phases, optionally via a voltage divider, relative to ground of the measurement and evaluation unit. For example, in three-phase systems it can happen that 20 they can be routed without neutral conductors and/or grounding conductors so that the operating voltage relative to ground could not be directly measured. Since in this embodiment of the invention the operating voltages are measured relative to the ground of the voltage supply of the measurement and evaluation unit, it is always possible in a uniform circuit structure to measure the operating voltages directly, regardless of whether the three-phase system is now routed with or without neutral conductors and/or grounding conductors.

In order to display proper system operation or the failure of phases and/or shut-off of the protective devices, it is provided in one development of the invention that an optical display device is assigned to the measurement and evaluation unit.

5 This display can be a remote display and/or a display device which is located on the housing of the measurement and evaluation unit.

It is preferable if the display device has an optical signal means, preferably three, which correspond to the number of phases. These signal means are not active for example in proper operation, conversely when one phase fails and/or the protective element shuts off the respective signal means lights or blinks, for example.

Furthermore, it can be provided that the display device has an optical signal means for display of operating voltage monitoring so that it can be easily recognized whether all operating 15 voltages of the system are in order.

Finally, to further check that the monitoring system is working properly it can be provided that the display device has an optical signal means for the voltage supply of the measurement and evaluation unit.

In monitoring systems like this one, it is a problem that parts of the monitoring system work in the extra-low voltage range, other parts conversely in the low voltage range so that a close spacial relation of these parts operating in a different voltage range is to be avoided or must be avoided. In the invention this problem is solved by the parts of the measurement and evaluation unit working in the extra-low voltage range being located on one board in the housing and that in the housing there is another board on which the components of the monitoring system working in the low voltage range are located.

The process as claimed in the invention is characterized preferably by an initialization phase and an operating phase, its being checked in the initialization phase whether the determined voltages and/or the values computed therefrom can be assigned to one of at least two stipulated network types, and its being monitored according to proper assignment in the subsequent operating phase whether the determined actual values of voltages and/or the values computed therefrom deviate from stipulated setpoints for the type of network.

This process has the major advantage that the system can execute logic comparison of the actual type of network with the information or selected phases which have been set on the control unit.

In this way the monitoring system can ascertain in the initialization phase for example that there is an error when in an alternating current system three switches are turned on; this should only be the case in a three-phase current network or, if for example in an alternating or direct current network, only two S 15 switches are correctly turned on, assignment of the switches to the actually connected lines however is not right.

Furthermore, in the initialization phase for example it can be Sautomatically ascertained which voltage class of the network is involved so that a uniform monitoring system for different voltage levels of networks can be used, at the same time the operator being relieved of the corresponding adjustment work, thus also eliminating a source of errors.

oe o Other features and advantages of the invention follow from the description of embodiments of the invention given below with reference to the drawings.

Figure 1 shows one embodiment of a fused interrupter with the cover of the housing removed and a monitoring system attached, Figures 2a to 2h show different network systems which can be monitored with the monitoring system as claimed in the invention, Figure 3 shows the housing of the monitoring system in the disassembled state, the boards of the monitoring system which are equipped with electrical or electronic parts being shown schematically, Figure 4 shows an oblique view of the housing from 7 above and Figure 5 shows an oblique view of the housing from underneath.

Figure 1 shows a fused interrupter 1 to which a monitoring system 2 as claimed in the invention is connected. The housing cover and the touch guard 3 of the fused interrupter 1 are shown in the removed state so that contact reeds 4 can be recognized on the base body 5 of the interrupter 1. From the contact reeds 4 a total of six lines 6 run to the bottom of the housing 7 of the monitoring system 2 and are inserted through holes 8 in the bottom 9 of the housing 7 (Figure 3).

As shown in Figure 3, the housing 7 consisting of a housing cover and the housing bottom 9 accommodates two boards 11, 12 on which the electrical or electronic components of the monitoring system are located. The components are separated to the extent that components working in the extra-low voltage range are located on board 11 and the components working in the low voltage range are located on board 12. Accordingly the lines 6 which are S 20 routed through the holes 8 in the bottom 9 are connected to board 12 via connectors 13.

S.The measurement and evaluation unit with parts which are located on board 11 has its own power supply. The plug unit 14 which is assigned to the measurement and evaluation unit for the power supply is likewise located on board 12. The network-side plug part 15 is also shown symbolically in Figure 3. All measurement and supply voltages which are in the low voltage range are lowered by voltage dividers or other suitable means on the board 12 to an extra-low voltage range or the measurement range in which the measurement and evaluation unit on board 11 is working.

As was described previously in conjunction with the attached drawings, in this embodiment it is possible to tap the voltages of the three phases on the contact reeds 4 via six lines 6 in front of and following one fuse at a time, which can be inserted -8via a swivel mechanism in the housing cover 3 between the contact reeds 4 which are assigned to one another in pairs. Thus for example a three-phase system without neutral conductors and/or grounding conductors can be monitored and evaluated. One such three-phase system is shown symbolically in Figure 2a, in which three phases Rl-R2, Sl-S2 and T1-T2 (on the housing bottom 9 in Figure 5 labelled Li-LI', L2-L2', L3-13') are protected via fusible links 16. At the measurement points 17, 18, 19 the operating voltages of the three phases are tapped in front of and behind the fuses 16 and are supplied to the measurement and evaluation unit via the lines 6. The measurement points 17, 18, 19 correspond to the connection points of the lines 6 to the contact reeds 4.

S 15 At the six measurement points 17, 18, 19 now both the difference voltages over the individual fuses 16 and the operating voltage "in front of" and/or "following" the fuses 16 can be tapped, the expressions "in front of" and "following" the fuses 16 having been arbitrarily chosen since the monitoring system as claimed in the invention can work independently of the feed direction.

Figures 2b and 2c, like Figure 2a, show three-phase systems, in Figure 2b only one phase Rl-R2 being equipped with a fuse 16, and in Figure 2c two phases Rl-R2 and S1-S2 being equipped with fuses 16.

In order to make the monitoring system 2 usable not only for the three-phase system which is shown in Figure 2, but also for the alternating and the direct current systems which are shown in Figures 2d through 2h, the measurement and evaluation unit has switches 20 to 25 (Figure Here for example the switches to 22 are assigned to the three possible phase inputs with two measurement lines 6 each. When all three phases are to be monitored, all three switches 20, 21 and 22 should be turned on.

If not all phases are to be monitored, the switch or switches to 22 which are assigned to the phase or phases not to be 9 monitored are turned off. The individual switches 20 to 22 are accessible through an opening 27 in the bottom 9 of the housing 7 of the measurement and evaluation unit 2.

The possibility of being able to switch away the phases or inputs which are not to be monitored offers the possibility of using the monitoring system as claimed in the invention also for the types of networks shown in Figure 2d to 2h.

Figure 2d is an alternating current system in which both the phase L and also the neutral conductor N are protected via fuses 16 and also the two conductors L, N are to be monitored.

Depending on to which of the terminals 13 the measurement points 17, 18 are connected via the conductors 6, only two of the three switches 20, 21 and 22 need be turned on.

i "•The corresponding applies to the alternating current system which se. is shown in Figure 2e and in which only the phase L, but not the neutral conductor N, is protected via a fuse 16.

Conversely, in the alternating current system as shown in Figure 2f, only the phase L is protected and monitored so that only one of the three switches 20 to 22 need be turned on.

What was stated regarding alternating current systems as shown in Figures 2d and 2e applies analogously to the direct current networks as shown in Figures 2g and 2h, i.e. that two of the three switches 20 to 22 need be turned on in order to monitor the two direct current systems. For reasons of clarity it is pointed out that the term "phase" is also used for the positive and negative conductor.

Since the three-phase system as shown in Figure 2a is routed without neutral conductors and/or grounding conductors, the operating voltage cannot be measured directly relative to ground.

To make the monitoring system as claimed in the invention usable 10 for these cases as well, the operating voltage relative to the ground of the power supply 14, 15 of the measurement and evaluation unit is measured. This type of measurement of operating voltage offers the major advantage that a uniform circuit structure of the monitoring system is possible since of course the operating voltage can also be measured in three-phase systems with neutral conductors and/or grounding conductors relative to ground of the power supply of the measurement and evaluation unit.

The corresponding of course also applies to the current networks which are shown in Figures 2d to 2h, and in which likewise the operating voltage is measured relative to ground of the power supply of the measurement and evaluation unit.

S In the three-phase systems which are shown in Figures 2a, 2b and 2c the voltage is acquired in such a way that first the operating o0oo voltages of the individual phases are acquired at the measurement points 17, 18, 19 on one side of the fuses relative to ground.

Furthermore the difference voltages between the two measurement points 17, 18 and 19 of each phase are acquired, the difference voltage being measured even with zero in the phases in which there are no fuses 16.

The measurement and evaluation unit 2 then computes from the operating voltages of the individual phases the phase-to-phase voltages, i.e. the voltage differences between Ri-Si, RI-Ti and S1-T1. The phase-to-phase voltages on the other side of the fuses are then computed on the basis of the already computed phase-to-phase voltages on one side of the fuses and the difference voltages AR, AS, and AT, i.e. R2 S2 R1 S1 AR AS; R2 T2 R1 T1 AR AT; S2 T2 S1 T1 AS AT.

If the difference voltage over a fuse 16 deviates from a stipulated boundary value, the monitoring system outputs an error message.

11 In the three-phase systems as shown in Figures 2b and 2c, in which not all phases have fuses, the phase-to-phase voltages are computed on the second side accordingly, although the difference voltages AR, AS and AT between the measurement points 17, 18 and 19 are different, depending on whether there is one fuse or there are different fuses or not.

Continuous monitoring of voltages, phase shifts and the like takes place more then using the phase-to-phase voltages and the difference voltages which are continuously compared to the setpoints, the monitoring system delivering an error message when an actual value deviates unduly from the respectively stipulated setpoint.

S 15 In the alternating current and direct current systems as shown S•in Figures 2d to 2f, monitoring does not take place on the basis of phase-to-phase voltages, but here the operating voltages of the individual phases and the difference voltages over the fuses are used directly and are compared to setpoints.

By the circumstance that there are two measurement points one each in front of and following the fuse 16, if present (Figures 2b, 2c, 2e, 2h) per phase or conductor, and the operating voltage occurs relative to ground of the power supply of the measurement and evaluation unit, comprehensive monitoring and evaluation of the connected network is possible by at most six measurement points 17, 18 and 19, and in addition to the most varied power data of the network it can also be easily acquired whether at this point a fuse 16 is turned off or a phase has failed completely.

The sole adjustment which the customer must make in this embodiment is turning the three switches 20, 21 and 22 on and off in order to establish which of the three conductors or phases are to be monitored.

12 In order to enable or simplify a more comprehensive evaluation of the power data of the network system, in the embodiment shown there is another switch 23 on which the user sets whether it is a three-phase systems (three-conductor system) or a direct current or alternating current system. This differentiation can be necessary since the user could also release only one or two operating phases of a three-phase system by corresponding actuation of the switches 20 to 22 for monitoring. The differentiation whether it is an alternating current or direct current system can in turn be done by the measurement and evaluation unit itself by measuring how large the direct current portion of the individual phases or conductors is. A threshold value of for example 50 V can be stipulated for the direct current portion, the measurement and evaluation unit then deciding for a direct 15 current system when the direct current portion of a phase is :greater than this threshold value. It goes without saying that this threshold value can be set higher or lower according to the respective requirements. Furthermore there can also be another switch, for example a switch 24, in order to impart further differentiation between the alternating current system and the direct current system.

The measurement and evaluation unit can be designed such that using the measured voltages the voltage class of the system can 25 be automatically determined and when stipulated boundary values of the respective voltage class are exceeded or not reached, it reports an error. The measurement and evaluation unit here can work such that it measures either firstly all of the voltages at the inputs 13 and then using the on or off switches 20 to 24 executes the respective voltage or network classification, or using the on or off switches 20 to 22 measures and evaluates only those voltages at the inputs 13 which are turned on by the switches 20 to 22.

Finally there is another sixth switch 25 which can be used in conjunction with the bus system. Via one such bus system within 13 the framework of technical capabilities any number of monitoring systems can be combined and connected to a data processing system, for example a monitoring center or message center. Since in these bus systems it is necessary for the last unit in the bus system to have a terminal resistance, as claimed in the invention one such terminal resistance which is provided on a standard basis on the measurement and evaluation unit can be switched towards or away via the switch 25 so that the monitoring system as claimed in the invention can be easily connected to the start, into the middle or to the end of the bus system. To connect the bus system, on the cover 10 of the housing 7 in addition to the plug 14 for power supply of the measurement and evaluation unit there are two plugs 35 and 36 which are located on the board 11.

Via one such bus system the individual low voltage switching devices can also be connected to a control unit, for example, a computer. In this case the switches 20 to 24 on the measurement and evaluation unit 2 can be omitted since the corresponding information about the type of network and/or the choice of phases to be monitored can be set via the bus system. It is of course also possible with the bus system connected to leave the switches 20 to 24 on the measurement and evaluation unit 2 since the user then with the uniform system himself has the choice whether to set the corresponding parameters on the switches or via the bus system. In this case of course provisions must be made to prevent competition between the settings which have been made on the switches and via the bus system by for example assigning priority to the settings via the bus system over the settings on the switches 20 to When the monitoring system as claimed in the invention is operating, the measurement and evaluation unit in conjunction with the settings of switches 20 to 24 in the initialization phase first tries to recognize the type of network and the voltage class. If this recognition has been successfully completed, the operating mode of the measurement and evaluation 14 unit changes into the monitoring mode in which it is continuously checked whether the determined network operating data and especially the operating voltages or the phase-to-phase voltages and difference voltage of the individual monitored phases are within the boundary values which have been stipulated for the respective voltage class. When one of the determined actual values exceeds the boundary value, the measurement and evaluation unit outputs an error message.

If the initialization process cannot be correctly completed, i.e.

the operating voltage or phase-to-phase voltage and the type of network cannot be correctly assigned to a certain class using the switches 20 to 24 which have been turned on, this process is repeated after a certain time interval has passed. Here it is either possible to repeat this process any number of times or to stipulate a maximum number of repetitions after which this Sinitialization phase is finally stopped.

The indication of proper operation or of faults can be done in 20 different ways.

.oe On the one hand this can be done by the aforementioned bus system.

On the other hand, it is possible to provide a remote indication which is activated for example via a relay which is provided in the measurement and evaluation unit. In the simplest form this relay is released in proper operation and as soon as some error occurs, it is picked up so that the remote indication is activated. It goes without saying that in this simplest type of remote indication it is only possible to display fundamentally any error, detailed fault location having to take place on site.

A plug for one such remote indication using a relay is labelled 26 in Figures 3 and 4.

15 The third possibility for error indication provided in the monitoring system as claimed in the invention is accomplished by an optical display means 28 on the cover 10 of the housing 7 and has five optical signal means 30 to 34, preferably LED, which are located on the board 11 and which can be seen on the display means 28. Here the LEDs 30, 31 and 32 are assigned to the three possible phases or lines and on the cover they are labeled L1, L2 and L3. As long as the network is working property, the LEDs 31 and 32 are inactive. As soon as an error occurs, i.e. a fuse 16 turns off, the assigned LED 30, 31 or 32 begins to blink, for example, red.

There is a fourth LED 33 to indicate that on one monitored phase the voltage is correct. As soon as a boundary value has not been reached for one phase in front of or following the fuse or the voltage drops or completely fails, the LED 33 begins to light, for example yellow, and the LED 30, 31 or 32 which is assigned to the corresponding phase shows red.

Finally, there is a fifth LED 34 which shows green when the **measurement and evaluation unit is working properly and goes out or blinks in case of an error.

To indicate that the system was not able to assign the operating 25 voltages in the initialization phase to a certain class, for example the LEDs 30 to 32 which are assigned to the three phases blink red in opposition. In the initialization phase for example the LED 34 shows green, the LED 33 blinks yellow and the LEDs to 32 show red. If an initialization error occurs, for example LED 34 shows green, the LED 33 is off and the LEDs 30 to 32 blink in opposition.

For proper operation for example the LED 34 shows green and the red LEDs 30 to 32 and the yellow LED 33 are off.

16 In the initialization phase the measurement and evaluation unit can execute for example the following logic checks and stop initialization in case of one of the following errors: all switches 20 to 24 are on "OFF"; all three switches 20 to 22 are on, the switch 23 for the three-phase current is not; only the switch 23 is on, but none of switches 20 to 22; it is a three-phase system and not all phase-to-phase voltages are present and/or in the allowable range for the respective voltage class; it is a direct current or alternating current system and not all operating voltages are present and/or in the allowable range for the respective voltage class.

.o.

Claims

2. Monitoring system as claimed in claim 1, wherein the control unit has switches (20 to 25) which are assigned to the measurement and evaluation unit
3. Monitoring system as claimed in claim 1 or 2, wherein a switch (20 to 22) is assigned to each phase (Rl-R2, S1- S2, Tl-T2)
4. Monitoring system as claimed in one of claims 1 to 3, wherein there is one switch (23) for classification of 25 the voltage system.
5. Monitoring system as claimed in one of claims 1 to 4, wherein the measurement and evaluation unit is connected via a bus line to a data processing system, for example, a computer.
6. Monitoring system as claimed in one of claims 1 to 4, wherein there is one switch (25) for the terminal resistance of the bus system. 18
7. Monitoring system as claimed in claim 5 or 6, wherein the control unit, for example, a computer, is connected to the measurement and evaluation unit via the bus line.
8. Monitoring system as claimed in one of claims 1 to 7, wherein the switches (20 to 25) are located on an opening (27) in the housing of the measurement and evaluation unit (2)
9. Monitoring system as claimed in one of claims 1 to 8, wherein the measurement and evaluation unit has a separate voltage supply (14, Monitoring system as claimed in one of claims 1 to 9, 15 wherein an optical display device (27) is assigned to the :°ooo o measurement and evaluation unit (2) .:oeoi
11. Monitoring system as claimed in claim 10, wherein the indication device (28) is located on the housing of the measurement and evaluation unit.
12. Monitoring system as claimed in claim 10 or 11, wherein the indication device (28) has signal means (30, 31, 32) which correspond to the number of phases, preferably 25 three optical means.
013. Monitoring system as claimed in one of claims 10 to 12, wherein the indication device (28) has an optical signal means (33) for operational indication of network or voltage monitoring.
14. Monitoring system as claimed in one of claims 9 and 10 to 13, wherein the indication device (28) has optical signal means (34) for the voltage supply of the measurement and evaluation unit. 19 Monitoring system as claimed in one of claims 1 to wherein the measurement and evaluation unit (2) located in a housing which can be connected to housing 5) of a fuse system. 14, is the
16.
17. a Monitoring system as claimed in claim 15, wherein the parts of the measurement and evaluation unit working in the extra-low voltage range are located on a board (11) in the housing and wherein in the housing there is another board (12) on which the components of the monitoring system working in the low voltage range are located. Process for acquiring and evaluating the operating voltages of phases of low voltage switchgear which are to be monitored, with protective devices, for example, fuses, wherein the operating voltage relative to ground on one side of the protective device and the difference voltage over the protective device of each phase to be monitored are acquired, wherein these voltages are sent to a measurement and evaluation unit and wherein these measured actual values of the voltages and/or the values computed from them by the measurement and evaluation unit are compared in the measurement and evaluation unit to the setpoints. Process as claimed in claim 17, wherein the operating voltage of the phases is measured, optionally via a voltage divider, relative to ground of a separate voltage supply of the measurement and evaluation unit. Process as claimed in claim 17 or 18, wherein the measurement and evaluation unit delivers an error message when an actual value deviates from the setpoints. a a. 25 a. a a
18.
19. 4, 20
21.
22.
23. Process as claimed in claim 17 or 19, wherein data from at least two, preferably six, measurement points are supplied to the measurement and evaluation unit. Process as claimed in one of claims 17 to 20, wherein information about the type of network and/or a choice of the phases to be monitored can be set via the control unit. Process as claimed in claim 21, wherein only the voltages of those phases which have been selected on the control unit are supplied to the measurement and evaluation unit. Process as claimed in claim 21, wherein all acquired voltages are sent to the measurement and evaluation unit, but only the voltages of those phases are evaluated which have been selected on the control unit. Process as claimed in one of claims 17 to 22, wherein in a three-phase system using the acquired operating voltages, optionally only the selected phases, the phase- to-phase voltages on one side of the protective device are computed, and wherein the phase-to-phase voltages on the other side of the fuses are computed based on the computed phase-to-phase voltages and the acquired difference voltages. Process as claimed in one of claims 17 to 24, character- ized preferably by an initialization phase and an operating phase, its being checked in the initialization phase whether the determined voltages and/or the values computed therefrom can be assigned to one of at least two stipulated network types, and its being monitored according to proper assignment in the subsequent operat- ing phase whether the determined actual values of the
24. a 4 21 voltages and/or the values computed therefrom deviate from stipulated setpoints for the type of network.
26. Process as claimed in claim 25, wherein the measurement and evaluation unit delivers an error message when the initialization phase is not properly completed.
27. Process as claimed in one of claims 17 to 26, wherein during the initialization phase the direct current portion of the phases to be monitored is determined and if the direct current portion of a phase exceeds a stipulated threshold value, the measurement and evalua- tion unit classifies the system as a direct current system. o *o DATED this 5th day of June 2000. e* M. Schneider, Schaltgeratebau und Elektroinstallationen Gesellschaft m.b.H. WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN. VIC. 3122.