The present disclosure relates to the field of electrical switches, for example, in switching installations for high or medium voltage. The present disclosure also relates to a method for determining the wear on a contact element of such a switch, and to an electronic unit for an electrical switch.
Circuit breakers are subject to continual wear and should therefore be monitored and maintained regularly. For instance, the arc that occurs during a switching operation (e.g., a protective shutdown) leads to material wear on the contact pieces and thus makes a considerable contribution to the wear. Contacts generally cannot be checked in a simple manner, without cost-intensive disassembly and turn-off of the power. Therefore, periodic circuit breaker maintenance is usually performed, if appropriate with maintenance brought forward if protective shutdowns with high currents have occurred. Therefore, in general the switch is maintained too often. The maintenance causes avoidable costs, and an additional risk of damage being caused during maintenance. On the other hand, in the case of excessively long maintenance intervals, there is a risk, however, of wear or contact wear not being identified at an early stage. Here there is the risk of a malfunction, but at the least a loss of performance of the switch.
Therefore, it would be desirable to determine the wear on the contact pieces more reliably. However, the wear is difficult to measure or predict since it is influenced by a multiplicity of factors. It is generally assumed that the contact wear is brought about by the cumulative energy conversion (power loss) when an arc occurs with the circuit breaker having been opened. Solely counting the number of faults that have occurred at a circuit breaker therefore cannot yield an accurate estimation with regard to the contact wear.
EP 1475813 A1 describes methods for determining contact wear in electrical switching installations for high or medium voltage, wherein a contact current that flows through the switch during a switching operation is recorded with the aid of a current converter and an evaluation is made with regard to contact wear. In order to determine a state variable characterizing the contact wear, a current measurement signal of the current converter is first measured as a function of time, the presence of a measurement error is detected upon the occurrence of deviations between the expected contact current and the current measurement signal, and, upon detection of the measurement error, at least one characteristic current value is determined from the current measurement signal and used for determining the state variable. DE 10204849 A1 also describes a method for determining contact wear.
However, the known methods for determining wear can still be improved with regard to their reliability. It is also desirable to obtain methods which, in a multiplicity of different switching situations, yield such reliable results that they are suitable for automated (e.g., remote) diagnosis and maintenance. Cost-intensive maintenance work can be reduced in this way. At the same time, reliable continuous state monitoring can be realized. It is also desirable to identify and eliminate problems and wear before they become critical.
An exemplary embodiment of the present disclosure provides a method for determining the wear on a contact element of an electrical switch. The exemplary method includes recording electrical values (I(t), U(t)) which represent an electrical variable, which is relevant to an arc occurring at the switch during a switching operation, as a function of time. The exemplary method also includes calculating a wear value (d), which represents the wear on the contact element, from a plurality of wear contribution values. The wear contribution values are calculated from a plurality of subsets (I(ti); I([ti;t′i])) of the recorded electrical values using a plurality of wear contribution calculation rules (fi), such that each of the wear contribution values is calculated from a respective one of the subsets of values (I(ti); I([ti;t′i])) according to a respective one of the wear contribution calculation rules (fi). At least two of the wear contribution calculation rules (fi) differ from one another.
An exemplary embodiment of the present disclosure provides an electronic unit for an electrical switch. The exemplary electronic unit includes a value input module for obtaining electrical values which represent a variable, which is relevant to the power flowing through the switch during a switching operation, as a function of time. The exemplary electronic unit also includes a wear determination module having a computation unit and a non-transitory data memory having an executable program recorded thereon for execution by the computation unit. The program includes a plurality of wear contribution calculation rules (fi) for calculating respective wear contribution values from respective subsets (I(ti); I([ti;t′i])) of the recorded electrical values. At least two of the wear contribution calculation rules (fi) differ from one another. The program also includes a wear value calculation routine for calculating a wear value (d), which represents the wear on a contact element, from the wear contribution values.
Additional refinements, advantages and features of the present disclosure are described in more detail below with reference to exemplary embodiments illustrated in the drawings, in which:
In order to improve at least some of the drawbacks associated with known techniques as mentioned above, the present disclosure provides a method for determining the wear on a contact element of an electrical switch, an electronic unit (e.g., a switch controller) for an electrical switch, and a switching installation which can include the electronic unit and/or perform the method of the present disclosure. Further advantages, features, aspects and details of the present disclosure are described below with reference to exemplary embodiments of the present disclosure, as illustrated in the drawings.
An exemplary embodiment of the present disclosure provides a method for determining the wear on a contact element of an electrical switch (e.g. a vacuum switch), for example, of a switching installation for high or medium voltage. The method includes recording electrical values which represent an electrical variable, which is relevant to an arc occurring at the switch during a switching operation, as a function of time. The electrical values can be recorded, for example, as a continuous function or as a data series (vector) with discretely sampled values, but can also include virtual values, for example, (partly) simulated, interpolated, or fitted values, in which case virtual values are recorded. By way of example, the electrical values can be current values which represent a contact current flowing through the switch during a switching operation as a function of time. The method furthermore includes calculating a wear value, which represents the wear on the contact element, from a plurality of wear contribution values. The wear contribution values are calculated from a plurality of subsets of the recorded electrical values using a plurality of wear contribution calculation rules, with the result that each of the wear contribution values is calculated from a respective one of the subsets of values according to a respective one of the wear contribution calculation rules. At least two of the wear contribution calculation rules differ from one another. In this case, a subset of values should be understood such that it can also include all of the recorded electrical values.
An exemplary embodiment of the present disclosure provides an electronic unit, for example, a control and/or monitoring system, for an electrical switch (e.g. a vacuum switch), for example, for a switching installation for high or medium voltage. The electronic unit includes a value input module for obtaining electrical values (e.g. current values) which represent an electrical variable, which is relevant to an arc occurring at the switch during a switching operation, as a function of time. The value input module can therefore be equipped, for example, for obtaining recorded electrical values from a value measuring device, but possibly also electrical values recorded by (partial) simulation or interpolation, etc. The electronic unit furthermore includes a wear determination module having a computation unit and a non-transitory data memory (e.g., a computer-readable recording medium such as a non-volatile memory) having an executable program recorded thereon which can be executed by the computation unit. The program, including instructions of the program, includes a plurality of wear contribution calculation rules which are intended to calculate respective wear contribution values from respective subsets of the recorded electrical values. At least two of the wear contribution calculation rules differ from one another. The electronic unit also includes a wear value calculation routine for calculating a wear value, which represents the wear on the contact element, from the wear contribution values. According to an exemplary embodiment, the program can include rules and/or instructions for executing any of the methods mentioned herein.
The present disclosure also relates to an apparatus for performing the methods disclosed and also includes apparatus parts for performing respective individual method steps. The method steps can be performed by hardware components, by a computer programmed by means of corresponding software, by a combination of both, or in any other manner. The present disclosure is furthermore also directed to methods in accordance with which the apparatuses respectively described operate. It includes method steps for performing each function of the apparatuses.
In the case of the embodiments described below, individual aspects and features can be combined modularly with the aspects and features of other embodiments. By means of such combination, further embodiments can in turn be obtained, which should likewise be regarded as associated with the present disclosure. A switch for a single phase is described below. Three phases with a respectively associated circuit breaker are generally present. The respective instances of wear can then generally be determined independently of one another, in accordance with any of the aspects described herein.
A description is given below principally of those embodiments in which current values are recorded, and the wear contributions are calculated from the current values. More generally, the wear contributions can also be calculated from other electrical values. In this case, electrical values are understood to be any values of variables which are relevant to an arc occurring at the switch during a switching operation. For example, the electrical values can be current values, voltage values and/or combinations thereof (e.g. arc power values formed by a product of current and voltage). The computation rules mentioned herein on the basis of the current are analogously also applicable on the basis of such further electrical values, by replacement of the current values I in the same computation rules by the other electrical values.
Electrical switches such as those which are used, for example, as circuit breakers in a switching installation for high or medium voltage usually have two or more contact pieces. With the switch closed, the contact pieces are in electrically conductive direct contact with one another. When the switch is opened, the contact pieces are moved away from one another and separated, such that current can no longer flow from one contact piece to the other contact piece. If a current flows during the switching process, then during the separation of the two contact pieces from one another the current flow is not immediately interrupted completely, rather an arc arises between the two contact pieces, which continues to carry the current for a certain time. Such an arc also occurs in circuit breakers, for example, special types of switch which are designed to switch under load, and especially in the case of circuit breakers for high voltage (e.g., voltages of more than 50 kV, e.g. 50-800 kV), or for medium voltage (e.g., voltages of 5 kV to 50 kV).
Such a switching process under load with an arc is illustrated in
In the example illustrated, the contact pieces 10, 20 are designed as the TMF type. TMF type means that the contact pieces are designed such that the switching current during a switching process brings about a predominantly transverse magnetic field (perpendicular to the general current flow direction or to a main direction of the arc, i.e. parallel to an area defined by the contact surfaces 14 and 24). This is achieved here by means of slots in the contact plates 14 and 24. The slots predefine a current flow direction of the current 31b, 31c in the plates such that the current induces a transverse magnetic field (in the horizontal plane in
The switch illustrated in
One difficulty in the case of switches, and in particular in the case of circuit breakers, is the wear on the contact pieces (e.g. contact pieces 10, 20 in
One method mentioned here for illustration purposes provides for this purpose a current integral of the following form, for instance, for determining the wear:
d=k*∫I(t)αdt (1)
The wear is indicated here by a thickness d (in mm) by which, during a switching process, material is eroded from the contact surface of the contact piece on account of the arc. In this case, I(t) represents the contact current flowing through the switch during a switching operation as function of time t, i.e. the current which flows through the arc 33 at the time t, see
However, the computation rule (1) yields inaccurate results particularly for medium or high switching currents. If the parameters k and α are calibrated for low switching currents, then the wear for high switching currents and long arc durations (phase length 0.75 π or more) tends to be overestimated by the rule (1), and the wear for medium or high switching currents and short arc durations (phase length 0.25 π or less) tends to be underestimated. Therefore, the issue arises of wanting a more realistic or more accurate rule for determining the wear d also for a wide range of switching currents and arc durations. For this purpose, there might be occasion to replace the integrand in (1) by a more complex expression (having more parameters to be adapted empirically). However, the accuracy that can be achieved with such an approach is likewise limited and cannot justify the increase in the number of parameters to be adapted.
According to the present disclosure, these difficulties are at least alleviated by the following method for determining the wear on the contact element: firstly, the current values I(t) which represent the contact current flowing through the switch during a switching operation are recorded as a function of time t. The current values I(t) can be recorded as a continuous function or as a data series (vector) were discretely sampled values. The sampled current values can comprise not only measured values but also virtual values, e.g. values that are fitted or interpolated or simulated on the basis of the measurement values and/or a suitable model. By way of example, the current can be assumed to be sinusoidal, and the amplitude and phase and, if necessary, the frequency of the signal can be adapted on the basis of measured values, thus resulting in good correspondence of the sinusoidal current to the measured values.
The wear value d is then calculated from a plurality of N wear contribution values di, i=1 . . . N (for instance as a sum of the wear contribution values). The wear contribution values di are in turn calculated from a plurality of subsets of the recorded current values I(t) using a plurality of wear contribution calculation rules fi, with the result that each of the wear contribution values is calculated from a respective one of the subsets of current values according to a respective one of the wear contribution calculation rules fi (a subset of current values can also comprise all of the recorded current values, that is to say can be a proper or an improper subset). In this case, at least two of the wear contribution calculation rules differ from one another (as functionals or mappings).
One aspect of the present disclosure is based on the insight that different arc phases occur during a switching process. Said arc phases approximately succeed one another temporally. Said different arc phases lead to respectively different wear on the contact pieces, that is to say that the wear is dependent on the current differently, depending on the arc phase: whereas a diffuse arc, for instance, leads to rather uniform and minor wear on different parts of the contact piece, a stationary constricted arc leads to intensive wear on a limited part of the contact piece, and is thus more relevant overall to the wear.
The method according to the present disclosure advantageously makes it possible to calculate the contribution of different arc phases to the wear of the contact element as a respective dedicated wear contribution value. Each of the wear contribution values can be calculated by means of a wear contribution calculation rule specific to the respective arc phase. For this purpose, it is advantageous to choose the subsets of current values and/or the wear contribution calculation rules such that a specific recorded current value, depending on the arc phase in which it occurs, leads to a respectively different wear contribution.
For this purpose, firstly it is necessary to determine the respective subsets of current values. As subsets of current values it is possible to determine those current values which belong to a respective arc phase. For this purpose, it is possible to determine the intervals of time for the respective arc phases (e.g. for ith arc phase the time interval [ti;t′i] from ti to t′i), and it is possible to choose the subsets of current values as the subsets of current values I([ti;t′i]) associated with the respective time interval [ti;t′i]. For this purpose, the limit times ti, t′i for the respective arc phase are suitably determined (see further below), and the subsets of current values are defined taking these times into account.
The temporal delimitation between the individual arc phases can be somewhat blurred, with transition periods therebetween. Nevertheless, it is possible to determine at least approximately a limit time for the limit (start or end) of a phase, that is to say ti for the start or t′i for the end of the ith arc phase. Generally, such a limit time can be either a start time for the start of the arc (or of the first arc phase), or a transition time for the transition from one phase to a respective next phase, or an end time for the end of the arc (or of the last arc phase). Accordingly, the transition time does not relate to the start or the end of the arc as such, since different arc phases do not merge into one another here.
In the case of TMF switches, the type and movement of the arc can be recorded by observations on specially shaped contact pieces. In this case, in an exemplary TMF switch it was possible to distinguish the following different arc phases from one another:
In the above example, therefore, it is possible to determine as the limit time a start time t0 (or, more precisely, topen) for the start of the diffuse arc, a transition time t′0=t1 for the transition from the diffuse arc to the constricted stationary arc, a further transition time t′1=t2 for the transition from the constricted stationary arc to the wandering arc, and an end time t′2=t3 for the end of the wandering arc. If these transition periods are determined in a suitable manner, then the subsets of current values can be determined as a first, second and third subset of current values I([t0;t′0]), I([t1;t′1]), I([t2;t′2]).
Referring to
The current illustrated in
At the time t1=t′0, the diffuse arc undergoes transition to a constricted stationary arc. This transition can be recorded e.g. by virtue of the fact that the current overshoots a predefined current threshold Iconstr. The exact choice of the threshold value Iconstr is dependent on the geometry of the contact pieces and on further details, and can be calibrated e.g. by measurements. Through various observations it was ascertained that Iconstr can generally be more than 10 kA, that is to say e.g. 15 kA. Alternatively, the transition to the constricted stationary arc can also be defined in some other way. Further possible alternatives for determination are described further below.
At the time t2=t′1 the stationary arc undergoes transition to a moving arc, under the influence of the transverse magnetic field generated by the flowing current. The movement of the arc leads to an increased noise component in the measured voltage and the measured current. Therefore, the transition to the moving arc can be recorded by virtue of the fact that the noise component in the voltage (ratio of the variance in a predefined frequency range to an averaged value of the voltage) overshoots a predefined threshold. The exact choice of the frequency range and the threshold value is dependent on the geometry of the contact pieces and on further details, e.g. the evaluation of the noise signal is particularly meaningful in the case of the spiral TMF type. The threshold value etc. can be calibrated e.g. by measurements. Alternatively, the transition to the constricted stationary arc can also be defined in some other way, as described further below.
At the time t3=t′2 the arc is extinguished, and the arc phase thus ends as well. This time can be identified e.g. by virtue of the fact that the current decreases significantly. More generally, the time t3 can be defined by a decrease in the current and/or voltage to below a predefined limit value.
In order to determine the abovementioned limit times which delimit the individual arc phases, it is also possible to use further events which are correlated in some way with the start or the end of an arc phase. Such an event can be, for example:
The limit time can be chosen, for example, as the time of a corresponding event. The limit time can also be calculated taking account of a plurality of the events mentioned, for instance by logical or weighted combination of a plurality of events or by averaging of a plurality of corresponding times. The limit time is, for example, a transition time representing a transition from a stationary arc state to a wandering arc state.
The at least one limit time can also be determined taking into account at least one of the following measurement values:
Depending on the availability of measurement values and events, it is possible to select elements from the above list and to suitably calibrate the determination rules for a respective arc phase. It is also possible to employ a plurality of determination rules and to combine their results, e.g. by averaging or forming a weighted average value.
In accordance with an exemplary embodiment, the respective intervals of time for the subsets of current values can be determined, for example, in the following manner:
The end of the constricted rotating arc (phase 2) can be determined e.g. by virtue of the current again undershooting a predefined threshold value.
The numbers in the left column refer to the time segments illustrated in Figures
As is shown in
Generally, in order to calculate the wear value, therefore, at least one transition time is determined, which, for example, represents a respective transition between different phases of an arc occurring during the switching operation. The intervals of time are defined, for example, such that the transition time defines a transition between a first one of the intervals of time [ti;t′i] and a second one of the intervals of time [tj;t′j] such that t′i=tj is formed by the transition time. For example, the method can involve defining an end t′i of the first interval of time [ti;t′i] and a start tj of the second interval of time [tj;t′j] taking account of the transition time determined, e.g. such that the transition time lies between the first interval of time and the second interval of time; for example such that the first interval of time is earlier than or identical to the transition time, and the second interval of time is later than or identical to the transition time. In other words, the first interval of time then precedes the second interval of time, with the transition time therebetween. The subsets of current values are then determined taking account of the at least one transition time determined.
The subsets of current values I([ti;t′i]) are accordingly determined as the current values associated with a respective interval of time [ti;t′i]. At least one of the intervals of time [ti;t′i] is defined taking account of the at least one limit or transition time determined.
Possible embodiments of the individual wear contribution calculation rules (per subset of current values or per arc phase) are described below. In one embodiment, at least one, or else all, of the wear contribution calculation rules is/are evaluated as a respective integral of the form (1) (or as a sum approximated by such an integral), wherein the respective time integral or the sum is restricted only to the respective interval of time or the respective subset of current values. The respective parameter k and α in (1) can then be chosen in each case separately per subset of current values (or per arc phase), e.g. can be predefined on the basis of a model or calibrated on the basis of measurements.
A wear contribution calculation rule fi for the ith subset of current values (represented here as the subset of current values associated with the interval of time [ti;t′i]) can then be formulated as
wherein ki and. Ki, αi correspond to the parameters k and α in (1). In equation (2′), the parameter K is capitalized in order to indicate the different physical unit by comparison with the parameter k from equations (1) and (2): [k]=cm A−αi s−1; [K]=cm A−αi. Otherwise, the parameters k and K are equivalent. In one embodiment, it is possible to choose the form (2) or (2′) for two subsets of current values (e.g. first (i=1) and second (i=2) subsets of current values) where α1≠α2 or K1≠K2. For example, in embodiments, 0.5≦α1,α2≦2.
However, calculation rules other than (2), (2′) are also possible. In general, the calculation rule includes forming a contribution in the form
for at least two of the wear contributions (where i=1 for a first wear contribution and i=2 for a second wear contribution, such that φ1≠φ2, wherein the inequality sign here denotes: “not identical as functions”). Here, I(t) respectively denotes a current value included in the subset of current values associated with the ith wear contribution. Equations (2) and (2′) are special cases of (3) and (3′), respectively, e.g. where φi(I(t))=Ki*I(t)α
The wear value can then be calculated as the sum of the individual wear contributions di=fi[I], i=0 . . . (N-1), for instance in the form
where fi denotes one of the wear contribution calculation rules described herein.
In (2′) for the wear contribution calculation rule fi summation is effected only within the limits ti to t′i. Instead of a hard limit for these sums, summation can also be effected over a longer period of time, wherein the contributions are weighted with a time-dependent function γi(t) which is greater inside an interval of time [ti, t′i] than outside the interval of time. Any correspondingly generalized equation (2′) then has the following form:
Examples of the functions γi(t) are illustrated in
An alternative function γi(t) is illustrated in
The function γi(t) can be expressed as follows: γi(t)={tilde over (γ)}((t−ti)/(t′i−ti)) where {tilde over (γ)} denotes a function having greater values inside the interval [0;1] than outside the interval. The functions outlined in
In a generalization of equation (4), the wear can be expressed as a sum
where
wherein, in the example of equation (3), φi(I(t))=Ki*I(t)α
The above calculation rule can correspondingly also be applied to integrals over current values recorded temporally continuously. In this case, in accordance with the above generalization, the wear can be expressed as the integral
The integral can be numerically approximated.
Even further possible modifications will be described below. In accordance with one modification, it is possible to calculate the wear contribution values for a plurality of the arc phases with a similar wear characteristic by means of a common wear contribution calculation rule. Nevertheless, not all arc phases should be calculated in the same way, i.e. at least two of the wear contribution calculation rules differ from one another.
In accordance with a further modification, besides the currents I, the arc voltages U are also recorded and taken into account when calculating the wear value. In accordance with one embodiment, the voltages could be recorded e.g. by means of additional voltage sensors. A corresponding wear function could then have the following form, for example:
Generally, any desired electrical value which represents a variable relevant to the power flowing through the switch during a switching operation can be used for the calculation, that is to say e.g. the current I, the arc voltage U, a product thereof (as in the above equation).
In a further embodiment, the power P(t)=I(t)*U(t) as a function of time, instead of I(t), can also be inserted directly into any of the equations mentioned above, e.g. (2), (2′), (3), (3′).
In accordance with a further modification, it is also possible to omit individual arc phases which make only an insignificant contribution to the wear. By way of example, the diffuse arc phase (zeroth phase between t0 and t1) can be omitted in the example of
A description is given below of a switch controller and a switching installation suitable for performing the method described herein. The switch controller includes a current value input module for obtaining current values (e.g. obtaining recorded current values from e.g. a current measuring device, but also from a device for simulation, interpolation, etc.) which represent a contact current flowing through the switch during a switching operation as a function of time. The switch controller furthermore includes a wear determination module having a computation unit (e.g., a processor) and a non-transitory data memory (e.g., a non-volatile memory) having an executable program recorded thereon which can be executed by the computation unit. The program includes a plurality of wear contribution calculation rules fi which are intended to calculate respective wear contribution values from respective subsets I([ti;t′i]) of the recorded current values, with the result that each of the wear contribution calculation rules calculates a respective one of the wear contribution values from a respective one of the subsets of current values. At least two of the wear contribution calculation rules fi differ from one another. The program furthermore includes a wear value calculation routine for calculating a wear value d, which represents the wear on the contact element, from the wear contribution values (e.g. as the sum thereof).
The executable program includes, for example, instructions for executing any method described herein. For example, the wear contribution calculation rules fi are intended to calculate a corresponding plurality of wear contribution values from a corresponding plurality of subsets I([ti;t′i]) of the recorded current values, with the result that each of the wear contribution calculation rules fi calculates a respective one of the wear contribution values from a respective one of the subsets of current values I([ti;t′i]).
In accordance with an exemplary embodiment, the switching installation is designed for high or medium voltage, and is, for example, a circuit breaker, e.g. a vacuum circuit breaker (but a gas-insulated circuit breaker is also possible). The switching installation includes the switch controller described above. The contact current is, for example, an arc current. The switching installation has, as contact element, for example a contact piece of the TMF type since here there are particularly distinct arc phases. A contact piece of the TMF type is characterized in that its design promotes a predominantly transverse magnetic field during the switching process or during an arc. The transverse magnetic field promotes the movement of the arc and thus leads to pronounced arc phases. The contact piece can be, for example of the spiral TMF type (as illustrated in
The switching installation can contain a plurality of contact elements (e.g. 3 contact elements for 3 phases). In this case, the wear can occur separately for each of the contact elements as described herein.
The switching installation can furthermore include a diagnosis system, which is connected to the switch controller in order to receive the calculated wear values. The diagnosis system can comprise, for instance, the following functions (separately per phase):
Even further general aspects of the present disclosure will be mentioned below. In accordance with one aspect, a method for determining the wear on a contact element involves calculating a wear value (d), which represents the wear on the contact element, from the recorded current values (I(t)), wherein a first wear contribution value is calculated according to a first wear contribution calculation rule (fi) from the at least one current value (I(ti); I([ti;t′i])) for the first interval of time (ti; [ti;t′i]), and a second wear contribution value is calculated according to a second wear contribution calculation rule (fj) from the at least one current value (I(tj); I([tj;t′j])) for the second interval of time (tj; [tjt′j]), wherein the first wear contribution calculation rule (fi) differs from the second wear contribution calculation rule (fj).
Generally, the wear contribution calculation rule need not be uniform within the respective current values. Recording can comprise a measurement, for example a sampling measurement in discrete sampling time intervals, but also (partial) simulation. The simulation can be based on a model, e.g. assumption that current values lie on a sinusoidal curve, or can comprise an interpolation between measurement values. In this way, the current values can be available as a continuous function of time or as a vector of discrete recorded values.
The wear contribution calculation rule is not identical to zero (as functional). A calculation rule identical to zero as functional would yield no wear contribution at all (i.e. always zero) independently of the electrical values of the subset of values. Such a calculation rule is not regarded as a wear contribution calculation rule.
It will be appreciated by those skilled in the art that the present disclosure can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.
Number | Date | Country | Kind |
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09177112 | Nov 2009 | EP | regional |
This application claims priority as a continuation application under 35 U.S.C. §120 to PCT/EP2010/066346, which was filed as an International Application on Oct. 28, 2010 designating the U.S., and which claims priority to European Application 09177112.1 filed in Europe on Nov. 25, 2009. The entire contents of these applications are hereby incorporated by reference in their entireties.
Number | Name | Date | Kind |
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20040223276 | Wimmer | Nov 2004 | A1 |
20070222427 | Takeuchi et al. | Sep 2007 | A1 |
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102 04 849 | Aug 2002 | DE |
1 318 533 | Jun 2003 | EP |
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Entry |
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Ronald L. Graham, Donald E Knuth, Oren Patashnik, Concrete Mathematics, 1994, Chapter 2. |
Notification Concerning Transmittal of International Preliminary Report on Patentability (Forms PCT/IB/326 and PCT/IB/373) and the Written Opinion of the International Searching Authority (Form PCT/ISA/237) issued on Jun. 7, 2012, in corresponding International Application No. PCT/EP2010/066346. (7 pages). |
Notification of Transmittal of Translation of the International Preliminary Report on Patentability (Forms PCT/IB/338 and PCT/IB/373) and the Written Opinion of the International Searching Authority (Form PCT/ISA/237) issued on Jun. 14, 2012, in corresponding International Application No. PCT/EP2010/066346. (6 pages). |
International Search Report (PCT/ISA/210) issued on Feb. 1, 2011, by the European Patent Office as the International Searching Authority for International Application No. PCT/EP2010/066346. |
Written Opinion (PCT/ISA/237) issued on Feb. 1, 2011, by the European Patent Office as the International Searching Authority for International Application No. PCT/EP2010/066346. |
Search Report issued on Apr. 19, 2010, by the European Patent Office for Application No. 091771121. |
Number | Date | Country | |
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20120253695 A1 | Oct 2012 | US |
Number | Date | Country | |
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Parent | PCT/EP2010/066346 | Oct 2010 | US |
Child | 13480927 | US |