The invention relates to a method and a device for monitoring an electrical network in a
rail vehicle as well as to a rail vehicle.
ln rail vehicles, both asynchronous and synchronous machines, including so-called
permanent magnet machines (PMM), which are also referred to as permanent magnet
motors, are used to drive the rail vehicle. The machines used to drive the rail vehicle are
also referred to hereinafter as drive motors. These machines are supplied with electrical
energy by a generally three-phase electrical network. The electrical network also
comprises a power converter that, in a motor mode of the permanent magnet machine,
converts a DC voltage, for example an intermediate circuit voltage, to a desired AC
tage for supplying the drive motor. However, the power converter can also, in a
generator mode of the drive motor, convert the AC voltage generated by the drive motor
to a DC voltage.
Short circuits may occur in the electrical network. They can occur both inside the drive
motor, for example, inside a housing of the machine, or along a phase line for connecting
the power converter and the drive motor. Short circuits may also occur in the power
converter. ln the event of short circuits, so-called electric arcs may also occurthat may
lead to the undesirable destruction of components of the rail vehicle.
It is known to monitor the level of a phase current, a short circuit being detected when the
level of the phase current exceeds a predetermined threshold.
lf such a short circuit is detected, the power converter is usually electrically disconnected
from the drive motor, for example, by correspondingly arranged circuit breakers. At the
same time, in particular given a permanent magnet machine as a drive motor, the rail
vehicle is braked until it comes to a stop to prevent potentialfeeding of the short circuit.
The technical problem exists of creating a device and a method for monitoring an
electrical network of a rail vehicle as well as a rail vehicle, the device and method enabling
the alternative yet reliable and rapid detection of a network error. Furthermore, the
technical problem exists of enabling the localization of a network error to provide improved
error management.
The technical problem is solved by the subject matters having the features of claims 1, B
and 9. Further advantageous embodiments of the invention are evident from the
dependent claims.
A method is provided for monitoring an electrical network in a rail vehicle. The electrical
network can in particular be a traction network of the rail vehicle or refer to a part of the
traction network of the rail vehicle. The electrical network serves in particular to transfer
energy between a power converter of the rail vehicle and a drive motor of the railvehicle.
The electrical network comprises at least one power converter. The power converter can
be operated both as an inverter and as a rectifier. For example, the power converter can
be designed as a three-phase power conveder. The power conveder can in particular
comprise electrical switching elements, such as MOSFET or IGBT.
On the input side, the power converter can be electrically connected to an intermediate
circuit, in particular an intermediate circuit capacitor, of the rail vehicle. An intermediate
circuit voltage falling across the intermediate circuit capacitor that is thus applied to the
power converter on the input side is a DC voltage. On the output side, the power
converter can be connected to the drive motor, for example, via at least one phase line.
Furthermore, the electrical network comprises at least one drive motor. The drive motor
can, as explained above, refer to an electrical machine for driving the rail vehicle, in
particular to a permanent magnet machine. The drive motor can thus be a synchronous
machine having a permanently magnetized rotor. The drive motor can be operated in a
motor mode. Electrical energy that is transmitted from the power converter to the drive
motor is converted to mechanical energy. The electrical energy is transmitted in the form
of an alternating current and an AC voltage that feed the drive motor. ln a generator
operating mode, mechanical energy is converted to electrical energy by the drive motor, it
being possible to transmit the electrical energy to the power conveder. The drive motor
generates an alternating current and an AC voltage.
Furthermore, the electrical network comprises at least one first phase line for electrically
connecting the at least one power converter and the at least one drive motor. The phase
line refers to an electric line through which a first phase current can flow. The electrical
network preferably comprises more than one, in particular three, phase lines. At least one
electrical switching element, for example, a power switching element, in particular a
MOSFET, an IGBT or a circuit breaker, can be arranged along the first phase line. An
electrical connection of the power converter and the drive motor via the first phase line
can be interrupted or established via the electrical switching element of the first phase
line.
The power converter is preferably a three-phase power converter that is connected to a
three-phase drive motor via three phase lines.
Furthermore, a level of a current change of the first phase current, in particular during a
predetermined period of time, is determined. The level can be determined as the
magnitude of the current change or refer to the magnitude. Thus, it is not the level of the
current or the current value that is determined, but a temporal change of the first phase
current or a level of this change. The level of the current change can be determined, for
example, by forming the first derivative.
Within the meaning of this invention, the term "determine" refers to the direct detection of
a variable, for example, by a detection means or a sensor, or the calculation of the
variable from at least one directly detected variable. Thus, for example, a current value of
the first phase current can be detected, for example, by a current sensor, the current
change being determined within a predetermined period of time as a function of the
current value.
The network can therefore comprise at least one first detection means for directly
detecting the current change of the first phase current. However, it is also possible that
the electrical network comprises a first detection means for detecting an electrical
variable, for example the current value, of the first phase current and at least a first
determination means, the first determination means determining the level of current
change of the first phase current as a function of the detected electrical variable. The
determination means can be designed as an FPGA.
lf more than one phase line, in particular three phase lines, is present, the electrical
network can, of course, comprise further detection means and, if applicable, determination
means that enable the determination of the current change level of the further phase
currents. Thus, the level of current change of at least one further phase current is
determined given a multiphase connection.
For example, a level of current change of the first phase current and a level of current
change of a further phase current, for example, a second phase current or a third phase
current, can be determined in a three-phase electrical network. The level of current
change of the remaining phase current can then be determined as a function of the levels
of current change already determined. For this purpose, the electrical network can, for
example, comprise a first current sensor for detecting the current value of the first phase
current and a further current sensor for detecting a current value of a further phase
current. The level of the current changes can then be determined by one or more
determination means.
The embodiments specified in the following of the method according to the invention for
the first phase line apply accordingly to further phase lines of the electrical network.
Furthermore, a network error in a machine-side sub-network is detected if at least one
criterion based on a current change is met. The criterion based on a current change is met
if the level of the current change of the first phase current is higher than a predetermined
current change threshold.
The machine-side sub-network refers to at least the part of the electrical network that is
arranged between a determination point of the electrical network, in or at which the level
of current change of the first phase current is determined, and the drive motor and
comprises at least one part of the drive motor. Thus, the machine-side sub-network can at
least comprise the section of the first phase line that connects the determination point
described above to the drive motor and comprises at least one part of the electrical
network of the drive motor.
The determination point refers to a point or section of the first phase line in which the
current change to be determined according to the invention occurs. The determination
point can thus refer to the point or section in which the current sensor described above is
arranged.
ln addition to the machine-side sub-network, the electrical network can also comprise a
sub-network on the power converter side, the sub-network on the power converter side
comprising the part of the electrical network that is arranged between the determination
point and the power converter as well as the power converter itself.
A network error refers in padicular to a short circuit or the occurrence of an undesirable,
low-ind uctance connection.
The current change thresholds can be determined as a function of the electrical properties
of the electrical network, in particular inductances of the electrical network.
The power converter of the electrical network or the part of the electrical network on the
power converter side usually has low inductance. lf a network error occurs in the machineside
part of the electrical network, in particular a short circuit or an undesirably lowinductance
connection, a very high current will flow from the part on the power converter
side to the machine-side part of the electrical network for a short period of time due to the
low inductance of the power converter or the part on the power converter side. The drive
motor and the phase line(s) usually have higher inductance than the power converter or
the part of the electrical network on the power converter side. lf a network error, in
particular a short circuit or an undesirably low-impedance connection, occurs in the part
on the power converter side, a lower current will flow from the machine-side sub-network
to the sub-network on the power converter side for a longer period of time compared to
the case of a network error in the machine-side part. ïhus, it follows that a high current
change occurs in the event of a network error in the machine-side par1, while a
comparably lower current change occurs in the event of a network error in the part on the
power converter side. However, it is to be assumed that at least the current change in the
event of a network error in the machine-side sub-network is higher than a maximum
permissible or maximum expected current change in the error-free state of the electrical
network.
A person skilled in the art can determine the current change threshold(s) as a function of
the electrical properties of the electrical network, for example, using suitable simulations
and/or experiments and/or calculations.
Advantageously, the result as a whole is that a network error can be detected reliably and
rapidly by evaluating the level of current change, it being possible to additionally associate
this network errorwith the machine-side sub-network. Thus, the localization of the network
error is advantageously made possible at the same time in addition to the mere detection
of a network error.
As explained in even more detail hereinafter, protective functions depending on an error
location can thus be initiated.
ln a further embodiment, the current change of the first phase current is cyclically
determined. A cycle can have a predetermined duration, for example a duration within a
range of 1 ps (including) to 5 ¡rs (including). The duration of a cycle is preferably 2 ps,
The criterion based on a current change is met if the levelof current change is higherthan
the predetermined current change threshold for at least a predetermined number of
cycles, in particular of cycles in immediate chronological succession. As a result, the
reliability of the detection is advantageously increased.
ln a furlher embodiment, an errer location in the machine-side sub-network is determined
as a function of the level of current change.
For example, it can be assumed that a correlation between the level of current change
and a distance of the error location in the machine-side sub-network from the
determination point described above is such that the level of current change decreases as
the distance increases. For example, the level of current change can decrease linearly or
exponentially as the distance increases.
This distance can referto a length of an, in particularshortest, electrical connection, for
example, of the phase line, that connects the determination point described above to the
error location.
The current change threshold described above can be selected in such a way that a
network error can be detected regardless of the error location in the machine-side subnetwork.
This means that the predetermined current change threshold is selected in such
a way that a network error can be detected even at a maximum distance between the
error location in the machine-side sub-network and the determination point.
ln addition, the distance of the error location can be determined depending on the
determined level of current change as a function of the previously known correlation
between the level of current change and the distance described above.
It is, for example, possible to divide the machine-side sub-network into several sections.
Each section can be associated with a section-specific minimum level of current change
and a section-specific maximum level of current change and thus a section-specific
interval of the level of current change. The smaller the distance of the section from the
determination point, the higher the section-specific minimum level of current change and
the section-specific maximum level of current change to be selected.
As a function of the level of current change determined according to the invention, the
corresponding interval, in which the determined level of current change lies, can be
determined. The section that is associated with this interval can then be determined as an
error location.
This advantageously results in a more precise spatial localization of the error location.
This in turn advantageously enables the improved error location-dependent execution of
protective functions.
ln a further embodiment, a level of the first phase current is determined. The levelcan be
determined as a magnitude or refer to the magnitude. The level can, for example, be an
amplitude or an RMS value of the first phase current. Furthermore, a network error is
detected in the machine-side sub-network if a criterion based on a current value is
additionally met, the criterion based on a current value being met if the level of the firsi
phase current is higher than a predetermined current value threshold.
Thus, at least two criteria must be met in order to detect a network error in the machineside
sub-network. As a result, the reliability of the detection is furlher increased.
ln a further embodiment, an error location in the machine-side sub-network is determined
when a network error is detected in the machine-side sub-network and an error locationdependent
protective function is executed, wherein a current flow in an erroneous network
section is reduced. The erroneous network section can include the error location. For
example, a current flow in the erroneous network section can be interrupted. For this
purpose, the erroneous network section can be isolated on one side or two sides. The
reduction or interruption of the current flow in the erroneous network section can, for
example, be done by opening at least one electrical switching element, which connects
the erroneous network section to a further network section. This is particularly
advantageous if the drive motor is designed as a permanent magnet machine.
For this purpose, the electrical network, in particular the first phase line, can comprise one
or more electrical switching elements that can interrupt or establish an electrical
connection for various sections of the phase line.
The speed of the drive motor can alternatively or cumulatively be reduced. For this
purpose, a rotor of the permanent magnet machine can, for example, be braked.
However, the rail vehicle can preferably be braked via at least one braking device. Of
course, the speed of the drive motor can be reduced to zero.
Of course, it is also possible to reduce, in particular interrupt, the current flow through the
phase line without determining the error location in the machine-side sub-network, and/or
it is possible to reduce the speed of the drive motor.
This advantageously results in a method for managing errors in the electrical network.
ln an alternative embodiment, the speed of the drive motor is reduced when a network
error is detected in the machine-side sub-network. Reference can be made here to the
precedíng explanations. Thus, in this alternative embodiment, no error location is
determined in the machine-side sub-network. An error location-independent protective
function is thus implemented.
ln this case, the electrical connection between the power converter and the drive motor,
i.e. at least the first phase line, will alternatively or cumulatively be interrupted. This
advantageously results in high operational safety if an error location in the machine-side
sub-network cannot be determined with sufficient accuracy or is not determined. ln this
case, the drive motor is partially or preferably fully braked to prevent the network error, in
particular the short circuit, from being fed.
ln a further embodiment, the electrical network comprises three phase lines for electrically
connecting the at least one power converter and the at least one drive motor, a level of
current change being determined for all phase currents. For this purpose, all phase
currents can be detected, for example, via a current sensor. lt is also only possible to
detect two of the three phase currents and calculate the remaining phase current as a
function of the detected phase currents.
Furthermore, a phase-specific network error in the machine-side sub-network is detected
if the at least one criterion based on a current change is met for any of the phase Iines.
This advantageously results in the ability to reliably monitor a three-phase network.
lf a network error is detected in only one of the phase lines, this phase line or all phase
lines can be interrupted. lf network errors are detected in only two of the phase lines,
these two phase lines or all phase lines can be interrupted. lf network errors are detected
in three phase lines, all phase lines can be interrupted.
Furthermore, a device is provided for monitoring an electrical network in a rail vehicle. The
device is designed in such a way that a method according to any of the embodiments
described above can be performed using the device. ln particular, the device comprises at
least one evaluation device.
The electrical network, which is monitored via the device, is designed as explained above.
Furthermore, the device comprises at ieast one evaluation device and at least one first
means for determining a level of current change of a first phase current. The first means
for determining the current change can be designed, as explained above, as a means for
detecting the current change. Alternatively, the first means can also comprise a means for
detecting an electrical variable and a determination means, it being possible for the
determination means to determine the current change as a function of the detected
electrical variable. The evaluation device and the at least one means for determination
can also be designed as a combined means. The means for detecting an electrical
variable and the determination means can also be designed as a combined means.
Furthermore, the level of current change of the first phase current can be determined.
Furthermore, a network error in a machine-side sub'network can be detected by the
evaluation device if at least one criterion based on a current change is met, the criterion
based on a current change being met if the level of current change of the first phase
current is higher than a predetermined current change threshold.
The device advantageously allows any of the methods described above to be carried out.
Also provided is a rail vehicle, the rail vehicle comprising the device described above. This
advantageously results in a rail vehicle having high operational safety.
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The invention is described in greater detail based on several exemplary embodiments.
The figures show:
Fig. 1 shows an exemplary equivalent circuit diagram of an electrical network in a
rail vehicle,
Fig.2 shows a schematic circuit diagram of an electrical network of the rail
vehicle and various types of error detection and
Fig. 3 shows an exemplary functional correlation between a level of current
change and a distance of an error location from a determination point.
Below, identical reference numbers refer to elements having the same or similar technical
features.
ln Fig. 1, an equivalent circuit diagram of the electrical network 1 of a rail vehicle (not
shown) is illustrated. This is a 2-phase system, the electrical components of a feed and
return line in the upper phase line being summarized. The electrical network 1 comprises
a power converter C (see Fig. 2), a resulting inductance L1_C and a resulting resistance
R'1_C of the power converter C being shown in Fig. 1. Also shown is an intermediate
circuit capacitor C_k. Furthermore, the electrical network '1 comprises a permanent
magnet machine M, a resulting inductance L_M and a resulting resistance R_M of the
permanent magnet machine M also being shown. Also shown is a phase line P having a
first section A, a second section B and a third section C.
Also shown are a current sensor CS and an evaluation device AE. The current sensor CS
detects a currentvalue in a determination point BP of the phase line P. Acurrent I is
shown here by way of example.
The evaluation device AE determines a current change dlidt as a function of the current
value and a duration dt. This current change is cyclically determined.
11
Also shown are resulting resistances R_A, R_8, R_C of the individualsections A, B, C of
the phase line P. Accordingly, resulting inductances L_4, L_8, L_C of the sections A, B, C
are also shown.
A first electrical switching element S1 is arranged along the phase line P, which, for
example, can be referred to as a motor circuit breaker. A fufiher electrical switching
element 52 is also arranged along the phase line P, which, for example, can be referred
to as an emergency motor circuit breaker. An electrical connection between the power
converter C and the permanent magnet machine M via the phase line P can be
established or interrupted by the switching elements S1, 52.
The first section A comprises at least one section of the phase line P between the
determination point BP and the first electrical switching element S1.
The second section B comprises a section of the phase line P between the first electrical
switching element S1 and the second electrical switching element 52.
The switching elements S1, 52 are arranged in such a way that the first section A can be
connected to the second section B via the first switching element S1. Furlhermore, the
second section B can be connected to the third section C via the second switching
element 52. Motor protection switches, which allow the electrical connection at terminal
points AP of the permanent magnet machine M to be interrupted, are not shown.
The third section C comprises a section of the phase line P between the second electrical
switching element 52 and a terminal point AP of the permanent magnet machine M. Also
shown is a fourth section D that comprises the electrical network of the permanent magnet
machine M up to the terminal points AP.
A level or magnitude of current change of the phase current I can be determined in each
cycle via the evaluation device AE. The evaluation device AE is also used to evaluate
whether a criterion based on a current change is met, this criterion being met if the level of
current change of the phase current I in each cycle is higher than a first predetermined
magnitude or the magnitude of the current change threshold SW1 (see Fig. 3).
lf the criterion based on a current change is met, a network error, in padicular a short
circuit, is thus detected in a machine-side sub-network TN_M. The machine-side subnetwork
TN_M comprises at least the part of the electrical network 1 that comprises the
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part of the phase line P which is arranged between the determination point BP and
terminal point AP of the permanent magnet machine M. The machine-side sub-network
TN_M also comprises at least one part of the electrical network of the permanent magnet
machine M.
A sub-network on the power converter side TN_C is likewise shown. This comprises at
least one part of the electrical network of the power converter C (not shown) as well as the
part of the phase line P that connects the power converter C and the determination point
BP.
The network error detected as described above is detected in the machine-side subnetwork
TN_M.
It is also possible that a level or magnitude of the phase current I is determined by the
evaluation device AE. ln this case, a network error in can be detected in the machine-side
sub-network TN-M if a criterion based on a current value is additionally met. This criterion
is met if the levelof the phase current lis higherthan a predetermined currentvalue
threshold.
lf a network error is detected in the machine-side sub-network TN_M, at least one of the
switching elements S1, 52, preferably both switching elements S'1, 52, can be opened.
ln Fig. 2, a three-phase electrical network '1 of a rail vehicle (not shown) is illustrated
schematically. An intermediate circuit capacitor C_k is again shown here that is
electrically connected to a power converter C on the input side. On the output side, the
power converter C is connected to a permanent magnet machine M via three phases P1,
P2, P3. No resulting resistances or resulting inductances are shown in Fig. 2.
A first current sensor CS_P1 for detecting a first phase current l_P1 in a first phase line
P1 is also shown. A further current sensor CS_P3 for detecting a third phase current l_P3
in a third phase line P3 is also shown. A second phase current l_P2 in a second phase
line P2 can be determined as a function of the remaining phase currents l_P1, l_P3.
Corresponding to the phase line P shown in Fig. 1, each of the phase lines P1, P2, P3
comprises a first electrical switching element S1_P1, S'1_P2, S1_P3 and a second
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electrical switching element 52_ P1 , S2_P2, S2_P3. A subdivision of the respective
phase line P1, P2, P3 into sections A, B, C is likewise shown. Terminal points AP of the
permanent magnet machine M are likewise shown, a fourth section D comprising an
electrical network of the permanent magnet machine M. Here, it is shown that the first
electrical switching elements S'1_P1, S1_P2, S1_P3 are controlled by a control device 2,
i,e. can be opened or closed. The first electrical switching elements S1_P1, S1_P2,
S1_P3 can be controlled jointly, in particular simultaneously, by the control device 2.
It is also shown that the second electricalswitching elements S2_P1, S2_P2, S2_P3 are
controlled by a second control device 3, i.e. can be opened or closed. The second
electrical switching elements S2_P1 , S2_P2, S2_P3 can likewise be controlled jointly, in
particular simultaneously, by the second control device 3.
A level or magnitude of a current change of the first phase current l_P1 , the second phase
current l_P2 and the third phase current l_P3 can be determined cyclically by an
evaluation device AE. A network error in a machine-side sub-network can be detected if
the criterion based on a current change described above is met for at least one of the
phase currents l_P1, l_P2, l_P3.
lf a network error is detected in the machine-side sub-network TN_M, at least two, but
preferably all, of the first switching elements S1_P1, S1_P2, S'1_P3 can be opened. At
least two, but preferably all, of the second switching elements 51_P1, S1_P2, S1_P3 can
be opened alternatively or cumulatively. ln particular, the first and/or second switching
element(s) S1_P1, S'1_P2, S1_P3, S2_P1 , S2_P2, S2_P3 of the phase line(s) for which
the criterion based on a current change is met can be opened.
A device for monitoring the electrical network 1 can at least comprise the evaluation
device AE. lt can preferably also comprise the current sensors CS_P1, CS_P3.
ln Fig. 3, an exemplary correlation is shown between a level of current change dl/dt and a
distance d of an error location from a determination point BP (see Fig. 1) in a phase line
P1, P2, P3. Here, it is shown thatthe levelof current change determined bythe
evaluation device AE becomes higher the closer the error location is to the determination
point BP. ln particular, the level of current change decreases exponentially as the distance
d from the determination point BP increases.
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lf the level of current change is higher than a first predetermined current change threshold
SW1, a network error in the machine-side sub-network TN_M (see Fig. 1 and Fig. 2) can
be detected. Thus, it is also possible to detect the presence of a network error either in the
first section A, in the second section B, in the third section C or in the fourth section D
(see Fig. 1).
lf such a network error is detected, the speed of the permanent magnet machine M can be
reduced, in particular by partially or fully braking the rail vehicle, i.e. to a standstill.
An error location in the fourth section D can be detected if the level of current change is
higher than the first predetermined current change threshold SW1 and lower than or the
same as a second predetermined current change threshold SW2,
lf the level of current change determined by the evaluation device AE is higher than the
second predetermined current change threshold SW2, it is possible to detect the presence
of an error location either in the first section A or in the second section B or in the third
section C of the machine-side sub-network TN*M. lf the level of current change is lower
than or the same as a third predetermined current change threshold SW3 but higher than
the second predetermined current change threshold SW2, it is possible to detect the
presence of the error location in the third section C.
Accordingly, it is possible to detect the presence of the error location in the second section
B if the level of current change is higher than the third predetermined current change
threshold SW3 but lower than or the same as a fourth predetermined current change
threshold SW4. The presence of the error location in the first section A can be detected if
the level of current change is higher than the fourth predetermined current change
threshold SW4.
Depending on a section A, B, C, D of the error location determined in this manner, an
error location-dependent protective function can be executed. lf the error location is, for
example, in the second section B, the first switching element S1 and the second switching
element S2 (see Fig. 1) can be opened. lf the location is in the third section C, the second
switching element 52 can, for example, be opened, and the electrical connection at the
terminal point AP of the permanent magnet machine M can be interrupted.
15
lf the error location is, for example, in the fourth section D, the electrical connection at the
terminal point AP can be interrupted, and the speed of the engine can be decreased. lf the
error location is in the first section A, the first switching element S'1 can be opened.
The overall, advantageous result is thus a method and a device for monitoring the
electrical network 1 of a rail vehicle enabling the reliable and rapid detection of a network
error. At the same time, unnecessary train shutdowns, i.e. unnecessary decelerations of
the rail vehicle, can be avoided. lf an error location is determined outside of the sections C
and D, a reduction of the speed of the permanent magnet machine M is not absolutely
necessary. Thus, it is possible to drive the rail vehicle using further drive means, such as
further permanent magnet machines.

We claim:
1. A method for monitoring an electrical network (1) in a railvehicle, the electrical
network (1) comprising at least one power converter (C), at least one drive motor and
at least one first phase line (P, P1) for electrically connecting the at least one power
converter (C) and the at least one drive motor,
characterized in that
a levelof current change of a first phase current (1, l1) is determined, a network error
being detected in a machine-side sub-network (TN_M) if at least one criterion based
on a current change is met, the criterion based on a current change being met if the
level of current change of the first phase current (1, l1) is higher than a predetermined
current change threshold (SW1).
2. A method according to claim 1, characterized in that the current change of the first
phase current (1, l1) is cyclically determined, the criterion based on a current change
being met if the levelof current change is higherthan the predetermined current
change threshold (SW1) for at least a predetermined number of cycles.
3. A method according to any of the preceding claims, characterized in that an error
location in the machine-side sub-network (TN_M) is determined as a function of the
level of current change.
4. A method according to any of fhe preceding claims, characterized in that a level of
the first phase current (1, l1) is determined, a network error being detected in the
machine-side sub-network (TN_M) if a criterion based on a current value is
additionally met, the criterion based on a current value being met if the level of the
first phase current (1, l1) is higher than a predetermined current value threshold.
5. A method according to any of the preceding claims, characterized in that an error
location in the machine-side sub-network (TN_M) is determined when a network error
is detected in the machine-side sub-network (TN_M) and an error location-dependent
protective function is executed, a current flow in an erroneous network section being
reduced and/or a speed of the drive motor being reduced.
6. A method according to any of claims 1 to 5, characterized in that a speed of the drive
motor is reduced and/or at least the first phase line (P, Pl) is interrupted when a
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7.
network error is detected in the machine-side sub-network (TN_M).
A method according to any of claims 1 to 6, characterized in that the electrical
network (1) comprises three phase lines (P, P1, P2, P3) for electrically connecting
the at least one power converter (C) and the at least one drive motor, a level of
current change of all phase currents (1, 11, 12, l3) being determined, a phase-specific
network error being detected in the machine-side sub-network (TN_M) if the at least
one criterion based on a current change is met for one of the phase lines (P, P1, P2,
P3).
A device for monitoring an electrical network (1) in a rail vehicle, the electrical
network (1) comprising at least one power converter (C), at least one drive motor and
at least one first phase line (P, P1) for electrically connecting the at least one power
converter (C) and the at least one drive motor, the device comprising at least one
evaluation device (AE) and at least one first means for determining a level of current
change of a first phase current (1, 11, 12, l3),
characterized in that
a level of current change of the first phase current (1, l1) is determinable,
a network error in a machine-side sub-network (TN_M) being detectable by the
evaluation device (AE) if at least one criterion based on a current change is met, the
criterion based on a current change being met if the level of current change of the
first phase current (1, l1) is higher than a predetermined current change threshold
(sw1).
L A railvehicle comprising a device according to claim L