Title of Invention

METHODS FOR CONTROLLING AN ELECTRONIC OVERCURRENT TRIP FOR LOW-VOLTAGE CIRCUIT BREAKERS

Abstract The invention relates to a method for controlling an electronic overcurrent trip for low-voltage circuit breakers, according to which digitized signals for the electricity values are generated and evaluated, and a tripping device providing short-circuit protection is activated when an overcurrent event is assumed to take place based on the evaluation. According to the inventive method, signals whose electricity value does not lie between the electricity values of the previous signal and the subsequent signal, or whose electricity value does not correspond to the electricity values of the previous signal or the subsequent signal, are rated as potentially erroneous signals and are tested by means of additional criteria.
Full Text WO 2005/027292 - 1 -
PCT/DE2004/001909
Description
Method for controlling an electronic overcurrent triP for
low-voltage circuit breakers
The invention relates to a method for controlling an electronic
overcurrent release for low-voltage circuit breakers, having
the features mentioned in the precharacterizing clause of claim
1
Overcurrent releases are used in low-voltage circuit breakers
to detect an overcurrent, event (for example a short circuit) in
good time when such an event occurs, and to prevent damage or
destruction of the low-voltage circuit breaker by suitable
means, for example means for immediate disconnection of the
contacts
The current flowing through the low-voltage circuit breaker is
determined for this purpose. According to the. prior art, this
Can be achieved, for example, by means of air-cored coils which
are arranged close to the current-carrying elements of the
low-voltage circruit- breaker. The conductor through which
current flows produces a magnetic field whose rate of change
leads to a voltage in the coil. This voltage signal is normally
converted by means of an analog/digital converter to a digital
signal, which is integrated and represents a parameter for the
current flowing through the low-voltage circuit breaker within
a time interval. This digitized current signal is supplied to a
microprocessor, which evaluates the individual, successive
current signals. If a more than proportional current rise (an
overcurrent event) is now deduced from the digitized current
signal, the microprocessor produces a

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signal which activates a release for shore-circuit protection
One particular problem in the case of electronic overcurrent
releases is their susceptibility to interference. The
introduction of interference through power supply units or EMC
influences can corrupt the digital current signals. The use of
capacitors is known, by way of example, in order to make it
possible to filter out corrupted current signals
However, a highly complex and thus costly filter mechanism would
be required ir> order to provide the capability co effectively
filter out all interference signals. For this reason, it is
Known for interference signals to be filtered out not only by
means of electrical circuits (for example. capacitors) but also
after digitization of the current signals Filtering of
interference signals is important for an assessment of whether
an overcurrent event has occurred, because spurious tripping of
the overcurrent release could occur if the interference signals
were not filtered.
in order to filter the already digitized current signals, it is
Known for the value (current level) of a digitized current
signal to be compared with three times the value of the
previous digitized current signal. If the current level is more
than three times the previous current level, this was filtered.
out according to the prior art, since it was assumed that the
current level had been influenced by interference- Filtering
means that this (filtered) current level is no longer used for
current detection and calculation, and thus for assessment of
whether an overcurrent event has occurred.

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The known method has the disadvantage that interference can be
identified only when the current signals are not greater than
one third of the measurement range of the A/D converter.
Otherwise, all interference is identified as being valid and is
included in the current detection and calculation, so that
spurious trippung of the overcurrent circuit breaker can occur
A further disadvantage is that the only interference which can
be identified is that which has a considerable influence on the
current levels (three times the previous current level)
Relatively mirror interference which does not reach three times
the previous current level can, however, likewise lead to
spurious tripping of the overcurrent release, if it occurs
repeatedly
The object of the present invention is thus to specify a method
for controlling an electronic overcurrent release for
law-voltage circuit breakers, which is less susceptible to
interference caused by power supply units and EMC influences.
According no the invention, this object is achieved by the
features of the characterising part of claim 1 in conjunction
with the features in the precharac ten zing clause Expedient
refinements are contained in the dependent claims.
One particular advantage of the method according to the
invention for controlling an electronic overcurrent release for
low-voltage circuit breakers is that this method is less
susceptible to interference caused by power supply units or EMC
influences Since signals whose current level is not between
the current levels of the previous signal and of the subsequent
signal, or whose current level does not match the current
levels

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of the previous signal or of the subsequent signal, are
classified as being potentially incorrect signals and are
checked by means of further criteria, it is also passible to
identify and filter out that interference which has less
influence on the digitised current levels than three times the
previous current level.
One preferred embodiment variant provides that those signals
which are classified as being potentially incorrect and whose
current levels exceed the current levels of the previous signal
by a predetermined value are not included in the evaluation for
the assessment of an overcurrent event.
This means that those current levels which are between the
current levels of the previous signal and of the subsequent
Signal or match the current levels of the previous signal or of
the subsequent signal axe always included in the evaluation for
the assessment of an overcurrent event since, according to the
invention, it is assumed that these signals are not subject to
interference from power supply units or EMC influences which
may result in spurious tripping of the overcurrent release.
Those signals which do not satisfy the criteria mentioned, above
are, however, initially regarded as being potentially incorrect
and checked by at least one further criterion to determine
whether these signals are subject to interference from power
supply unite or EMC influences. This can be assumed to be the
case if the current level of a potentially incorrect signal
exceeds the current level of a previous signal by an amount
that xs defined in advance. This amount is, for example,
dependent on the power data of the low-voltage circuit breaker,
on the measurement.

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range of the A/D converter and on the time interval between the
current or voltage measurements.
The digitized current signal are preferably generated for the
root mean square values of the current flowing through the
low-voltage circuit breaker
The assessment and filtering of the digitized current signals
are preferably carried out on the basis of the criteria
mentioned above by means of a data processing appliance. In one
particularly preferred embodiment variant, the data processing
appliance is a. microprocessor. The method described above makes
it possible to considerably reduce the susceptibility of
low-voltage circuit breakers to interference caused by power
supply units or EMC influences.
The invention is not restricted to the exemplary embodiments
described here. In fact, it is possible to provide further
embodiment variants by combination and modification. of the
stated means and features, without departing from the scope of
tne invention.

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Patent Claims
1. Method for controlling an electronic overcurrent release
for low-voltage circuit breakers, in which digitized signals
for the current values are generated and evaluated and a
release for short-circuit protection is activated as a
consequence of the evaluation when an overcurrent event occurs,
characterized in that
signals whose current level is not between the current levels
of the preceding signal and of the subsequent signal or whose
current level does not match the current levels of the previous
signal or of the subsequent signal are classified as being
potentially incorrect, and are checked by means of further
criteria
2 The method as claimed in claim 1,
characterized in that
those signals which are classified as being potentially
incorrect and whose current levels exceed the current levels of
the previous signal by a predetermined value are not included
in the evaluation for the assessment of an overcurrent event.
3 The method as claimed in claim 1 or 2,
characterized in that
the digitized signals are generated for the root mean square
values of the current flowing through the low-voltage circuit
breaker.
4 The method as claimed in one of the preceding claims,
characterized in that

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the current levels are determined toy measurement of voltages
which are produced in coils
5. The method as claimed in one of the preceding claims,
characterized in that
the digitized signals are produced by means of an A/D
converter, which converts the voltages which are produced in
coile to digital signals.
6 The method as claimed in one of the preceding claims,
characterized in that
the digitised signals are processed by means of a
microprocessor

The invention relates to a method for controlling an electronic overcurrent trip for low-voltage circuit breakers, according to which digitized signals for the electricity values are generated and evaluated, and a tripping device providing short-circuit protection is activated when an overcurrent event is assumed to take place based on the evaluation. According to the inventive method, signals whose electricity value does not lie between the electricity values of the previous signal and the subsequent signal, or whose electricity value does not correspond to the electricity values of the previous signal or the subsequent signal, are rated as potentially erroneous signals and are tested by means of additional criteria.

Documents:

00451-kolnp-2006-abstract.pdf

00451-kolnp-2006-claims.pdf

00451-kolnp-2006-description complete.pdf

00451-kolnp-2006-form-1.pdf

00451-kolnp-2006-form-2.pdf

00451-kolnp-2006-form-3.pdf

00451-kolnp-2006-form-5.pdf

00451-kolnp-2006-gpa.pdf

00451-kolnp-2006-international publication.pdf

00451-kolnp-2006-international search authority.pdf

00451-kolnp-2006-others.pdf

00451-kolnp-2006-pct forms.pdf

00451-kolnp-2006-priority document.pdf


Patent Number 245409
Indian Patent Application Number 451/KOLNP/2006
PG Journal Number 03/2011
Publication Date 21-Jan-2011
Grant Date 18-Jan-2011
Date of Filing 27-Feb-2006
Name of Patentee SIEMENS AKTIENGESELLSCHAFT
Applicant Address WITTELSBACHERPLATZ 2, 80333 MUNCHEN, GERMANY.
Inventors:
# Inventor's Name Inventor's Address
1 ANDREAS KRAUSS DE WARTBURGSTR. 31 10825 BERLIN
2 ANDREAS PANCKE DE BERNAUER STR. 47 13507 BERLIN
3 LLKA REDMANN DE KIRCHSTR. 8 14612 FALKENSEE
4 KLAUS NEIDHARDT DE DIEFFENBACHSTRA├čE 78 10967 BERLIN
PCT International Classification Number H02H 3/08
PCT International Application Number PCT/DE04/001909
PCT International Filing date 2004-08-24
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10343350.3 2003-09-12 Germany