U.S. patent application number 16/398323 was filed with the patent office on 2019-08-22 for method for distinguishing an arc from a luminous gas containing at least metal vapor.
The applicant listed for this patent is Eaton Intelligent Power Limited. Invention is credited to Michael Bartonek, Wolfgang Hauer.
Application Number | 20190260195 16/398323 |
Document ID | / |
Family ID | 54064343 |
Filed Date | 2019-08-22 |
![](/patent/app/20190260195/US20190260195A1-20190822-D00000.png)
![](/patent/app/20190260195/US20190260195A1-20190822-D00001.png)
![](/patent/app/20190260195/US20190260195A1-20190822-D00002.png)
United States Patent
Application |
20190260195 |
Kind Code |
A1 |
Bartonek; Michael ; et
al. |
August 22, 2019 |
METHOD FOR DISTINGUISHING AN ARC FROM A LUMINOUS GAS CONTAINING AT
LEAST METAL VAPOR
Abstract
A method for distinguishing an arc from a luminous gas at least
containing metal vapor includes sensing light in a monitoring
region and determining a first intensity I.sub..lamda.1 of the
sensed light at a first wavelength .lamda.1 and a second intensity
I.sub..lamda.2 of the sensed light at a second, greater wavelength
.lamda.2. The ratio I.sub..lamda.1/I.sub..lamda.2 between the first
intensity I.sub..lamda.1 and the second intensity I.sub..lamda.2 is
determined. The sensed light is associated with an arc if said
ratio I.sub..lamda.1/I.sub..lamda.2 is greater than a specifiable
first threshold value and/or with a luminous gas at least
containing metal vapor if said ratio I.sub..lamda.1/I.sub..lamda.2
is less than a specifiable second threshold value.
Inventors: |
Bartonek; Michael; (Vienna,
AT) ; Hauer; Wolfgang; (Vorderweissenbach,
AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Eaton Intelligent Power Limited |
Dublin |
|
IE |
|
|
Family ID: |
54064343 |
Appl. No.: |
16/398323 |
Filed: |
April 30, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15507809 |
Mar 1, 2017 |
10320176 |
|
|
PCT/EP2015/070254 |
Sep 4, 2015 |
|
|
|
16398323 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02H 3/16 20130101; G01R
31/1218 20130101; H02H 1/0023 20130101; G01R 15/247 20130101 |
International
Class: |
H02H 1/00 20060101
H02H001/00; H02H 3/16 20060101 H02H003/16; G01R 15/24 20060101
G01R015/24; G01R 31/12 20060101 G01R031/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2014 |
DE |
10 2014 112 723.4 |
Claims
1: A method for distinguishing an arc from a luminous gas including
a metal vapor, the method comprising: sensing light in a monitoring
region; measuring a first intensity I.sub..lamda.1 of the sensed
light at a first wavelength .lamda.1; measuring a second intensity
I.sub..lamda.2 of the sensed light at a second, greater wavelength
.lamda.2; determining a ratio I.sub..lamda.1/I.sub..lamda.2 between
the first intensity I.sub..lamda.1 and the second intensity
I.sub..lamda.2; and associating the sensed light with the arc if
the ratio I.sub..lamda.1/I.sub..lamda.2 is greater than a
specifiable first threshold value and/or with the luminous gas if
the ratio I.sub..lamda.1/I.sub..lamda.2 is less than a specifiable
second threshold value.
2: The method of claim 1, wherein the first wavelength .lamda.1 is
a range of from 300 to 400 nm and/or the second wavelength .lamda.2
is selected in a range between 650 nm and 750 nm.
3: The method of claim 1, wherein or the first threshold value
and/or the second threshold value is in a range of from 0.0125 to
5.
4: The method of claim 1, wherein the first threshold value and/or
the second threshold value is 2.5.
5: The method of claim 1, further comprising: issuing a first alarm
or a first switching signal if the arc is detected in a monitoring
region.
6: The method of claim 5, wherein the first alarm or a first
switching signal is issued if the arc is detected in the monitoring
region and also if a current in excess of a third threshold value
is detected in a supply line leading to the monitoring region.
7: The method of claim 1, further comprising: issuing a second
alarm or a second switching signal if the luminous gas is detected
in a monitoring region; and/or issuing a third alarm or a third
switching signal if a light sensed in the monitoring region can be
associated neither with the arc nor the luminous gas.
8: The method of claim 1, wherein a monitoring region is located
inside a switch cabinet.
9: A device for distinguishing an arc from a luminous gas including
a metal vapor, the device comprising: at least one light-sensitive
element configured to sense light in a monitoring region; a
measuring device configured to measure a first intensity
I.sub..lamda.1 of sensed light at a first wavelength .lamda.1 and
to measure a second intensity I.sub..lamda.2 of the sensed light at
a second, greater wavelength .lamda.2; and an evaluation unit
configured to determine a ratio I.sub..lamda.1/I.sub..lamda.2
between the first intensity I.sub..lamda.1 and the second intensity
I.sub..lamda.2 and to associate the sensed light with the arc if
the ratio I.sub..lamda.1/I.sub..lamda.2 is greater than a
specifiable first threshold value and/or with the luminous gas if
the ratio I.sub..lamda.1/I.sub..lamda.2 is less than a specifiable
second threshold value.
10: The device of claim 9, wherein: the at least one light
sensitive element includes a first light-sensitive element and a
second light-sensitive element; and further comprising: a first
optical filter disposed in front of the first light-sensitive
element; and a second optical filter disposed in front of the
second light-sensitive element, wherein the first optical filter
predominantly allows light at the first wavelength .lamda.1 to pass
through and wherein the second optical filter predominantly allows
light at the second wavelength .lamda.2 to pass though.
11: The device of claim 10, wherein the first and/or second optical
filter is/are configured as a band-pass filter.
12: The device of claim 11, wherein a maximum transparency of the
first optical filter is in a wavelength range of from 300 to 400
nm, and wherein a maximum transparency of the second optical filter
is in a wavelength range of from 650 to 750 nm.
13: The device of claim 9, further comprising: configured to issue
a first alarm/switching signal in the event of the arc being
detected in a monitoring region and/or a second alarm/switching
signal in the event of the luminous gas being detected in the
monitoring region and/or a third alarm/switching signal in the
event that light sensed in the monitoring region can be associated
neither with the arc nor with the luminous gas.
14: A switch cabinet, comprising: a switching device including the
device of claim 13, wherein the device includes an output connected
to a switch input of the switching device to issue the first
alarm/switching signal.
15: A method of monitoring a monitoring region located in a switch
cabinet, the method comprising: arranging the device of claim 1 in
a monitoring range of the monitoring region.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application. Ser.
No. 15/507,809, filed Mar. 1, 2017, which is a U.S. national stage
application under 35 U.S.C. .sctn. 371 of International Application
No. PCT/EP2015/070254, filed on Sep. 4, 2015, and claims benefit to
German Patent Application No. DE 10 2014 112 723.4, filed on Sep.
4, 2014. The International Application was published in German on
Mar. 10, 2016, as WO 2016/034712 A1 under PCT Article 21(2). The
above applications are hereby incorporated by reference herein.
FIELD
[0002] The invention relates to a method and to a device for
detecting an arc, and to a switch cabinet comprising at least one
switching device and comprising a connected device of the specified
type.
BACKGROUND
[0003] Such a method and such a device are generally known in the
art and are, for example, used in electrical systems to protect
people and/or the system itself, for instance, from the destructive
effects of an arc caused by a short circuit or to mitigate its
effects at the very least. For example, animals or even dropped
tools and (damp) dirt can reduce the insulation or spark gap
between two conductors having different voltage potentials such
that an arc is formed. The very high currents resulting in some
cases can lead to powerful explosions due to the air heating up in
a very short space of time.
[0004] Electrical systems are therefore often monitored to prevent
such an arc occurring, and in many cases this is achieved by
measuring the current flowing through the electrical conductors and
detecting the extremely intensive light resulting from an arc. If
both criteria are fulfilled, an alarm signal or a switching signal
is issued to close a switch between said conductors having
different voltage potentials. On the one hand, this causes the arc
to be extinguished quickly; on the other hand, it also causes very
high currents to occur in the supply lines, which trip a
higher-level circuit breaker, which ultimately isolates the danger
area from the network. Of course, said switching signal can also be
used to directly open a switch or a plurality of switches in the
supply lines leading to the arc.
[0005] In principle, there are a number of publications on this
subject in the prior art. For example, U.S. Pat. No. 6,229,680 B1
discloses a system for optical arc detection in which the light
received by a measurement point is split and passed through two
different band-pass filters. If the difference between the
electrical signal resulting from the received light and the
electrical signal resulting from a background light exceeds a
threshold value, an arc detection signal is issued.
[0006] EP 1 538 722 A2 also discloses a system for arc detection in
which the light received by a measurement point is combined with a
modulated reference light source and then split and passed through
two band-pass filters. If a first electrical signal, which
represents light at a first wavelength, exceeds a second electrical
signal that represents light at a second wavelength excluding the
modulated reference light, an alarm is issued.
[0007] CH 676174 A also discloses the use of a band-pass filter to
limit the light received by a measurement point to an arc
wavelength range.
[0008] Furthermore, DE 10 2010 016 036 A1 discloses a color sensor
comprising a red filter, a green filter and a blue filter for
detecting an arc.
[0009] Finally, GB 2477970 A discloses an optical fiber having a
fluorescent material which transforms light in a wavelength range
that is characteristic of an arc into light that has a different
wavelength. This transformed light is then passed to an optical
sensor.
[0010] As a general rule, it is difficult to detect a dangerous,
short-circuiting arc with any degree of certainty using methods in
the prior art. This is because, in electrical systems, arcing can
occur even during normal operation, for example in the form of
switching arcs when disconnecting a live switching contact. The arc
in a switching device itself is admittedly not directly visible,
although luminous gas can be emitted by the switching device, said
gas containing at least metal vapor which originates from the
burning switching contacts, or arc deflectors or arc splitters, in
the switching device. In addition, the gas may also contain other
constituents, for example evaporated plastics from the housing of
the switching device.
[0011] This luminous gas may erroneously be interpreted as
dangerous arcing, leading to an electrical system which is actually
working normally being shut down unnecessarily. In the prior art,
this kind of malfunction can in particular be observed if a
phase-to-earth short circuit (without arcing or with arcing outside
the switch cabinet) causes a very high measurable current in the
supply line and also causes an associated circuit breaker to trip.
The luminous gases emitted by the circuit breaker seem to fulfil
the two conditions (high current and bright light) mentioned at the
outset for a dangerous arc.
SUMMARY
[0012] An aspect of the invention provides a method for
distinguishing an arc from a luminous gas including a metal vapor,
the method comprising: sensing light in a monitoring region;
measuring a first intensity I.sub..lamda.1 of the sensed light at a
first wavelength .lamda.1; measuring a second intensity
I.sub..lamda.2 of the sensed light at a second, greater wavelength
.lamda.2; determining a ratio I.sub..lamda.1/I.sub..lamda.2 between
the first intensity I.sub..lamda.1 and the second intensity
I.sub..lamda.2; and associating the sensed light with the arc if
the ratio I.sub..lamda.1/I.sub..lamda.2 is greater than a
specifiable first threshold value and/or with the luminous gas if
the ratio I.sub..lamda.1/I.sub..lamda.2 is less than a specifiable
second threshold value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The present invention will be described in even greater
detail below based on the exemplary figures. The invention is not
limited to the exemplary embodiments. All features described and/or
illustrated herein can be used alone or combined in different
combinations in embodiments of the invention. The features and
advantages of various embodiments of the present invention will
become apparent by reading the following detailed description with
reference to the attached drawings which illustrate the
following:
[0014] FIG. 1 an example of a diagram for the absolute spectral
irradiance [.mu.Wcm.sup.-2nm.sup.-1] as a function of the
wavelength .lamda. for an arc and a luminous gas;
[0015] FIG. 2 an example of a device for distinguishing an arc from
a luminous gas;
[0016] FIG. 3 an example of a switch cabinet comprising a device
for distinguishing an arc from a luminous gas and
[0017] FIG. 4 similar to FIG. 3, but with a device for
extinguishing an arc.
DETAILED DESCRIPTION
[0018] An aspect of the invention provides an improved method and
an improved device for detecting an arc. In particular, it should
be possible to detect dangerous arcing with certainty and avoid
shutting down an electrical system unnecessarily.
[0019] An aspect of the invention provides a method for
distinguishing an arc from a luminous gas at least containing metal
vapor, comprising the following steps: [0020] sensing light in a
monitoring region, [0021] measuring a first intensity
I.sub..lamda.1 of the sensed light at a first wavelength .lamda.1
[0022] measuring a second intensity I.sub..lamda.2 of the sensed
light at a second, greater wavelength .lamda.2 [0023] determining
the ratio I.sub..lamda.1/I.sub..lamda.2 between the first intensity
I.sub..lamda.1 and the second intensity I.sub..lamda.2 and [0024]
associating the sensed light with an arc if said ratio
I.sub..lamda.1/I.sub..lamda.2 is greater than a specifiable first
threshold value and/or with a luminous gas at least containing
metal vapor if said ratio I.sub..lamda.1/I.sub..lamda.2 is less
than a specifiable second threshold value.
[0025] An aspect of the invention provides a device for
distinguishing an arc from a luminous gas containing at least metal
vapor, comprising [0026] at least one light-sensitive element for
sensing light in a monitoring region, [0027] a measuring device for
measuring a first intensity I.sub..lamda.1 of the sensed light at a
first wavelength .lamda.1 and for measuring a second intensity
I.sub..lamda.2 of the sensed light at a second, greater wavelength
.lamda.2, and [0028] an evaluation unit for determining the ratio
I.sub..lamda.1/I.sub..lamda.2 between the first intensity
I.sub..lamda.1 and the second intensity I.sub..lamda.2 and for
associating the sensed light with an arc if said ratio
I.sub..lamda.1/I.sub..lamda.2 is greater than a specifiable first
threshold value and/or with a luminous gas at least containing
metal vapor if said ratio I.sub..lamda.1/I.sub..lamda.2 is less
than a specifiable second threshold value.
[0029] Finally, an aspect of the invention provides a switch
cabinet comprising at least one switching device which comprises a
device of the above-mentioned type, having an output connected to a
switch input of the at least one switching device.
[0030] Finally, an aspect of the invention provides a method of the
above-mentioned type or a device of the above-mentioned type to
monitor a monitoring region located in a switch cabinet.
[0031] The proposed measures make it possible to distinguish a
dangerous arc with a high degree of certainty from the (potentially
harmless) gases emitted by a switching device. This method makes
use of the fact that the light spectrum of the luminous gas is
different to the light spectrum of the arc. The temperature of the
luminous (burning) gas ranges from approximately 2,500.degree. K to
4,500.degree. K, whereas the temperature of the arc ranges between
approximately 10,000.degree. K and 20,000.degree. K. Accordingly,
the light emitted by an arc has a higher proportion of short-wave
radiation.
[0032] Advantageously, it is not necessary to use complicated
spectral analyses to achieve the object of the invention. Instead,
two values are determined for light intensity in two specific
wavelength ranges and simple mathematical operations and
comparisons are used in the manner described above to distinguish
an arc from a luminous gas at least containing metal vapor. As a
result, the described method is also not very susceptible to
problems and can be implemented in practice with minimal technical
outlay.
[0033] It should be noted at this point that the luminous gas may
also, in particular, contain gaseous decomposition products of
plastics, for example hydrogen, carbon, hydrocarbons and similar
products in addition to metal vapor. Despite this variation in the
composition of the luminous gas, the described method or the
described device makes it possible to safely detect an arc or the
luminous gas, or to safely distinguish the two.
[0034] In a preferred embodiment of the invention, the sensed light
may be associated with an arc if said ratio
I.sub..lamda.1/I.sub..lamda.2 lies in a first range and/or with a
luminous gas at least containing metal vapor if said ratio
I.sub..lamda.1/I.sub..lamda.2 lies in a second range. In other
words, an associated upper threshold value is provided in addition
to the first lower threshold value and an associated lower
threshold value is provided in addition to the second upper
threshold value.
[0035] Further advantageous embodiments and developments of the
invention are described in the dependent claims and in the
description in conjunction with the figures.
[0036] It is advantageous if the first wavelength .lamda.1 is
selected in a range between 300 nm and 400 nm and/or the second
wavelength .lamda.2 is selected in a range between 650 nm and 750
nm. It is particularly advantageous if .lamda.1=350 nm is selected
as the first wavelength and/or .lamda.2=700 nm is selected for the
second wavelength. These wavelengths or wavelength ranges have
proved to be particularly suitable for distinguishing an arc from a
luminous gas.
[0037] It is particularly advantageous if the first threshold value
and/or the second threshold value is/are selected in a range from
0.0125 to 5. The second threshold value is in this case preferably
less than or equal to the first threshold value, but in principle
the second threshold value can also be greater than the first
threshold value. In this range it is possible to clearly
distinguish an arc from a luminous gas.
[0038] It is also advantageous if a value of 2.5 is selected for
the first threshold value and/or the second threshold value. Even
more preferable values for the first threshold value are 3.5 and
4.5, and 1.5 and 0.5 for the second threshold value. This is a
particularly good way of successfully distinguishing an arc from a
luminous gas.
[0039] It is also advantageous if the device for distinguishing an
arc from a luminous gas comprises an output which is designed to
issue a first alarm or a first switching signal in the event of an
arc being detected in the monitoring region. Accordingly, it is
advantageous if a first alarm or a first switching signal is issued
if an arc is detected in the monitoring region. A higher-level
control system or monitoring staff can thus be notified of the
fault in the electrical system. Alternatively or in addition, the
first switching signal can be sent directly to a switching device,
which automatically isolates the electrical system from the power
network supplying it with power in the event of a fault. It would
also be conceivable to send the first switching signal to a
switching device to short-circuit the arc and thus extinguish said
arc. The resulting high short-circuit current leads to a circuit
breaker tripping on the corresponding supply line. The first
switching signal can thus cause a switching contact to close and
can also cause a switching contact to open.
[0040] It is particularly advantageous if the first alarm or the
first switching signal is issued if an arc is detected in the
monitoring region and also if a current in excess of a third
threshold value is detected in a supply line leading to the
monitoring region. A dangerous situation in the monitoring region
can be identified particularly effectively by incorporating a
further criterion.
[0041] It is also advantageous if the device for distinguishing an
arc from a luminous gas comprises an output which is designed to
issue a second alarm/switching signal in the event of a luminous
gas at least containing metal vapor being detected in the
monitoring region and/or a third alarm/switching signal if the
light sensed in the monitoring region can be associated neither
with an arc nor a luminous gas at least containing metal vapor. It
is accordingly advantageous if a second alarm or a second switching
signal is issued if a luminous gas at least containing metal vapor
is detected in the monitoring region and/or a third alarm or a
third switching signal if the light sensed in the monitoring region
can be associated neither with an arc nor with a luminous gas at
least containing metal vapor. In specific terms, the third
alarm/third switching signal is issued if the ratio
I.sub..lamda.1/I.sub..lamda.2 lies between the first and second
threshold value. If ranges of values are provided to associate the
sensed light with an arc or a luminous gas at least containing
metal vapor, the third alarm/third switching signal is issued if
the ratio I.sub..lamda.1/I.sub..lamda.2 lies outside the range of
values proposed for the arc or the luminous gas.
[0042] The proposed measures mean that monitoring staff or a
higher-level control system can be provided with additional
information which does not necessarily indicate a dangerous
situation in the switch cabinet. In specific terms, the signals not
only indicate an arc in the switch cabinet, but also a luminous gas
emitted by a switching device and another light source, for example
daylight entering the switch cabinet when said cabinet is opened or
even a photo flash. The second and/or third switching signal can in
turn be passed to a switching device and is able to isolate or
close a power circuit.
[0043] The device for distinguishing an arc from a luminous gas
advantageously comprises two light-sensitive elements and optical
filters placed in front of the light-sensitive elements, the
filter(s) placed in front of the first light-sensitive element
predominantly allowing light at the first wavelength to pass
through and the filter(s) placed in front of the second
light-sensitive element predominantly allowing light at the second
wavelength to pass through. In particular, the first and/or second
optical filter may be designed as a band-pass filter. In this way,
two light-sensitive elements having an identical design can be used
to sense light from the monitoring region. In principle, however,
it is also conceivable to use a high-pass filter and a low-pass
filter.
[0044] It is particularly advantageous when using band-pass filters
if the first optical filter allows light to pass through in a
wavelength range between 300 nm and 400 nm and/or the second
optical filter allows light to pass through in a wavelength range
between 650 nm and 750 nm, or if the maximum transparency of the
first optical filter lies in this wavelength range and in
particular at 350 nm and if the maximum transparency of the second
optical filter lies in the above-mentioned wavelength range and in
particular at 700 nm. As already mentioned, these wavelengths or
wavelength ranges have proved to be particularly suitable for
distinguishing an arc from a luminous gas.
[0045] It is also particularly advantageous if the monitoring
region is located inside a switch cabinet. The advantages of the
invention are particularly evident in this case as the problem of
safely distinguishing an arc from a luminous gas often arises
inside a switch cabinet.
[0046] At this point it should be noted that the disclosed
variations on the described method and the resulting advantages
relate equally to the device for distinguishing an arc from a
luminous gas, to the described switch cabinet and to the described
use of such a method or such a device, and vice versa.
[0047] FIG. 1 shows a diagram for the absolute irradiance I as a
function of the wavelength .lamda. for an arc (Graph A) and a
luminous gas at least containing metal vapor (Graph B).
[0048] In a method for distinguishing an arc from a luminous gas at
least containing metal vapor, [0049] light is sensed in a
monitoring region, [0050] a first intensity I.sub..lamda.1 of the
sensed light at a first wavelength .lamda.1 is measured, [0051] a
second intensity I.sub..lamda.2 of the sensed light at a second,
greater wavelength .lamda.2 is measured, [0052] the ratio
I.sub..lamda.1/I.sub..lamda.2 between the first intensity
I.sub..lamda.1 and the second intensity I.sub..lamda.2 is
determined and [0053] the sensed light is associated with an arc if
said ratio I.sub..lamda.1/I.sub..lamda.2 is greater than a
specifiable first threshold value and/or with a luminous gas at
least containing metal vapor if said ratio
I.sub..lamda.1/I.sub..lamda.2 is less than a specifiable second
threshold value.
[0054] The first wavelength .lamda.1 is preferably selected in a
range between 300 nm and 400 nm and/or the second wavelength
.lamda.2 is selected in a range between 650 nm and 750 nm. In the
specific example shown in FIG. 1, the values for the first
wavelength are .lamda.1=350 nm and/or .lamda.2=700 nm for the
second wavelength. In the example shown in FIG. 1 the ratio
I.sub..lamda.1/I.sub..lamda.2 has a value of 5 for the arc (Graph
A), and 0.0125 for the luminous gas (Graph B). If a value of 2.5 is
selected for the first and second threshold value, the measured
ratio I.sub..lamda.1/I.sub..lamda.2 is clearly associated with an
arc or a luminous gas at least containing metal vapor. Other even
more preferable values for the first threshold value are 3.5 and
4.5, and 1.5 and 0.5 for the second threshold value. As a general
rule, the first and second threshold value should lie in a range
between 0.0125 and 5, the second threshold value being preferably
less than or equal to the first threshold value.
[0055] In the example shown, the described method thus comprises
the following specific steps: [0056] sensing light in a monitoring
region, [0057] measuring a first intensity I.sub..lamda.1 of the
sensed light at a wavelength .lamda.1=350 Nm. [0058] measuring a
second intensity I.sub..lamda.2 of the sensed light at a second,
greater wavelength .lamda.2=700 nm, [0059] determining the ratio
I.sub..lamda.1/I.sub..lamda.2 between the first intensity
I.sub..lamda.1 and the second intensity I.sub..lamda.2 and [0060]
associating the sensed light with an arc if said ratio
I.sub..lamda.1/I.sub..lamda.2 is greater than 2.5 and/or with a
luminous gas at least containing metal vapor if said ratio
I.sub..lamda.1/I.sub..lamda.2 is less than 2.5.
[0061] Advantageously, to associate the light with an arc or a
luminous gas, it is sufficient to measure two values for the
intensity I.sub..lamda.1/I.sub..lamda.2 of the light in two
specific wavelength ranges .lamda.1, .lamda.2 and carry out simple
mathematical operations and comparisons. On the other hand, there
is no need for complicated spectral analyses. The described method
is therefore not very susceptible to problems and can be
implemented in practice with minimal technical outlay, as shown in
FIG. 2.
[0062] FIG. 2 shows an example of a device 1 for distinguishing an
arc from a luminous gas at least containing metal vapor. The device
1 comprises [0063] two light-sensitive elements 2a, 2b for sensing
light in a monitoring region (3), [0064] a measuring device 4 for
measuring a first intensity I.sub..lamda.1 of the sensed light at a
first wavelength .lamda.1 and for measuring a second intensity
I.sub..lamda.2 of the sensed light at a second, greater wavelength
.lamda.2, and [0065] an evaluation unit 5 for determining the ratio
I.sub..lamda.1/I.sub..lamda.2 between the first intensity
I.sub..lamda.1 and the second intensity I.sub..lamda.2 and for
associating the sensed light with an arc if said ratio
I.sub..lamda.1/I.sub..lamda.2 is greater than a specifiable first
threshold value and/or with a luminous gas at least containing
metal vapor if said ratio I.sub..lamda.1/I.sub..lamda.2 is less
than a specifiable second threshold value.
[0066] In this example, two optical filters 6a, 6b are placed in
front of the two light-sensitive elements 2a, 2b, the filter 6a
placed in front of the first light-sensitive element 2a
predominantly allowing light at the first wavelength .lamda.1 to
pass through and the filter 6b placed in front of the second
light-sensitive element 2b predominantly allowing light at the
second wavelength .lamda.2 to pass though. In specific terms, the
two optical filters 6a, 6b are advantageously designed as band-pass
filters. With reference to the example shown in FIG. 1, one
particular possibility is that the first filter 6a may
predominantly allow light having a wavelength of .lamda.1=350 nm to
pass through and the second filter 6b may predominantly allow light
having a wavelength of .lamda.2=700 nm to pass through.
[0067] Furthermore, the device 1 is connected to an optional light
conductor 7, which conducts the light from the monitoring region 3
to the optical filters 6a, 6b or to the light-sensitive elements
2a, 2b. Finally, the device 1 also comprises an optional alarm
output or switching output 8.
[0068] The arrangement illustrated in FIG. 2 operates as
follows:
[0069] Light is conducted from the monitoring region 3 via the
light conductor 7 and the optical filters 6a, 6b to the
light-sensitive elements 2a, 2b, which convert the light into an
electrical signal. This electrical signal is evaluated by the
measuring device 4 and converted into intensity values
I.sub..lamda.1, I.sub..lamda.2 for the sensed light. The evaluation
unit 5 determines the ratio I.sub..lamda.1/I.sub..lamda.2 between
the first intensity I.sub..lamda.1 and the second intensity
I.sub..lamda.2 and associates the sensed light with an arc if said
ratio I.sub..lamda.1/I.sub..lamda.2 is greater than a specifiable
first threshold value and/or with a luminous gas at least
containing metal vapor if said ratio I.sub..lamda.1/I.sub..lamda.2
is less than a specifiable second threshold value. With reference
to FIG. 1, a value of 2.5 is in particular selected for the first
threshold value and the second threshold value. However, any other
threshold values mentioned in connection with FIG. 1 are of course
also conceivable. A first alarm or a first switching signal is
preferably issued if an arc is detected in the monitoring region 3.
Of course, if an arc or a luminous gas is detected, this can also
be transmitted in a different manner. In particular, it is also
possible to report that a luminous gas or the occurrence of light
which can be associated neither with an arc nor with a luminous gas
has been detected in addition to the arc or as an alternative to an
arc.
[0070] As a general rule, the measuring device 4 can be designed as
an analog-to-digital converter which converts the electrical signal
from the light-sensitive elements 2a, 2b to a digital value, and
the evaluation units 5 can be designed as a microprocessor in which
a software algorithm is carried out to determine the ratio
I.sub..lamda.1/I.sub..lamda.2 and to associate the received light
with an arc or a luminous gas.
[0071] However, it would also be conceivable to use analog modules
to determine the ratio I.sub..lamda.1/I.sub..lamda.2 and to
associate the received light with an arc or a luminous gas. In this
case, the measuring device 4 is primarily used to amplify the
signal, but may also be omitted in principle.
[0072] It would also be conceivable to create a structural unit
from a light-sensitive element 2a, 2b and a measuring device 4. For
example, this structural element may issue an (amplified) analog
signal or may also issue a digital value directly. In a first
embodiment of the invention, a light-sensitive element 2a, 2b and
an optical filter 6a, 6b may form a structural unit. For example,
the housing of the light-sensitive element 2a, 2b may be
correspondingly colored. It is also conceivable to combine a
light-sensitive element 2a, 2b, a measuring device 4 and an optical
filter 6a, 6b in a structural unit.
[0073] Finally, it is also possible to use just one light-sensitive
element 2a, in front of which the optical filters 6a, 6b may be
moved consecutively one after the other. For example, the filters
6a, 6b may be located on a motor-driven, rotating disc.
[0074] FIG. 3 shows an example of a switch cabinet 9 illustrated in
a purely symbolic fashion comprising three circuit breakers 10a . .
. 10c each associated with one phase of a three-phase system, a
higher-level circuit breaker 11, and a device 1 for distinguishing
an arc from a luminous gas at least containing metal vapor, which
is connected to a light-sensitive element 2 and a current
measurement loop 12. In addition, said device 1 comprises an alarm
output or switching output 8. Lastly, three loads 13a . . . 13c are
also connected to the switch cabinet 9.
[0075] The device 1 in this example has an extended functional
scope compared to the example shown in FIG. 2, due to the fact that
the signal from a current measurement loop 12 is also evaluated in
addition to optical monitoring of a monitoring region 3. In this
example, a first alarm signal and/or a first switching signal are
issued by the output 8 if an arc is detected using the method
described above, AND if the current measured by the current
measurement loop 12 exceeds a threshold value.
[0076] In the example shown in FIG. 3, a short circuit in the load
13b causes a higher current flow through the circuit breaker 10b,
the high-level circuit breaker 11 and the current measurement loop
12. The short-circuit current trips the circuit breaker 10b,
causing arcing via the resulting open contacts in a manner known
per se.
[0077] The arc in the circuit breaker 10b itself is admittedly not
usually directly visible to the light-sensitive element 2, although
luminous gas can be emitted by the circuit breaker 10b, said gas
containing at least metal vapor originating from the burning
switching contacts, or arc deflectors or arc splitters in the
circuit breaker 10b. In addition, the gas may also contain other
constituents, for example evaporated plastics from the housing of
the circuit breaker 10b.
[0078] Arc detection devices according to the prior art issue an
erroneous alarm signal or switching signal in this situation, as
not only is bright light detected in the switch cabinet 9, but an
excessively high current is also identified by the current
measurement loop 12.
[0079] However, the device 1 according to the invention is able to
safely distinguish between a visible arc burning in the switch
cabinet 9 and the luminous gas and in such a situation does not
give rise to an erroneous alarm signal or switching signal. Said
signal is only issued if an arc is visibly burning in the switch
cabinet 9, for example because animals have entered the switch
cabinet or tools have been dropped, causing the insulation or spark
gap between two conductors having different voltage potentials to
be reduced to such an extent that arcing results.
[0080] FIG. 4 shows an arrangement that is very similar to the
arrangement illustrated in FIG. 3. However, this arrangement also
includes the switching devices 14a . . . 14c, which are able to
short-circuit the individual phases with respect to one another. In
this case, for example, the first switching signal 8 can be sent to
the inputs of the switching devices 14a . . . 14c. If a fault
occurs, the switching devices 14a . . . 14c are closed, thus
extinguishing the arc burning between the phases. The overcurrent
caused by the short circuit causes the circuit breakers 10a . . .
10c or the circuit breaker 11 to trip, as a result of which the
system is ultimately disconnected from the power network. Of
course, the first switching signal 8 can also be issued by the
switch cabinet 9, leading to an alarm, for example. It is also
conceivable that the switching devices 14a . . . 14c are connected
to earth, in which case the phases can accordingly be
short-circuited to earth (and with respect to one another) using
the switching devices 14a . . . 14c.
[0081] It should be noted at this point that not only can the
formation of an arc (first alarm/first switching signal) be
reported, but also the formation of a luminous gas at least
containing metal vapor (second alarm/second switching signal) and
the occurrence of light that is associated neither with an arc nor
with a luminous gas at least containing metal vapor (third
alarm/third switching signal). The principle disclosed in relation
to the first alarm/first switching signal can also be applied in
the same manner to the second alarm/second switching signal and to
the third alarm/third switching signal. For example, the second
and/or third switching signal can be passed to a switching device
and is able to isolate or close a power circuit. In particular,
monitoring staff or a higher-level control system can be provided
with additional information in this manner which does not
necessarily indicate a dangerous situation in the switch cabinet 9.
In specific cases, for example, daylight entering the switch
cabinet 9 when opening said cabinet or even a photo flash can be
identified and reported.
[0082] Finally, it should be noted that the device 1 and the switch
cabinet 9 or their components are not necessarily shown to scale
and therefore may also assume different proportions. Moreover, a
device 1 for distinguishing an arc from a luminous gas or the
switch cabinet 9 may also comprise more or fewer components than
illustrated. References to positions (e.g. "top", "bottom", "left",
"right", etc.) refer to the specific figure being described and
should be adapted accordingly to the new position if said position
changes. Finally, it should be noted that the above embodiments and
developments of the invention can be combined in any manner.
[0083] While the invention has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive. It will be understood that changes and
modifications may be made by those of ordinary skill within the
scope of the following claims. In particular, the present invention
covers further embodiments with any combination of features from
different embodiments described above and below. Additionally,
statements made herein characterizing the invention refer to an
embodiment of the invention and not necessarily all
embodiments.
The terms used in the claims should be construed to have the
broadest reasonable interpretation consistent with the foregoing
description. For example, the use of the article "a" or "the" in
introducing an element should not be interpreted as being exclusive
of a plurality of elements. Likewise, the recitation of "or" should
be interpreted as being inclusive, such that the recitation of "A
or B" is not exclusive of "A and B," unless it is clear from the
context or the foregoing description that only one of A and B is
intended. Further, the recitation of "at least one of A, B, and C"
should be interpreted as one or more of a group of elements
consisting of A, B, and C, and should not be interpreted as
requiring at least one of each of the listed elements A, B, and C,
regardless of whether A, B, and C are related as categories or
otherwise. Moreover, the recitation of "A, B, and/or C" or "at
least one of A, B, or C" should be interpreted as including any
singular entity from the listed elements, e.g., A, any subset from
the listed elements, e.g., A and B, or the entire list of elements
A, B, and C.
* * * * *