CN116054085A - Zero sequence braking method and system for preventing non-fault phase saturation differential protection misoperation - Google Patents
Zero sequence braking method and system for preventing non-fault phase saturation differential protection misoperation Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
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Abstract
The invention discloses a zero sequence braking method and a system for preventing malfunction of non-fault phase saturation differential protection, comprising the following steps: after differential protection of a target power system is started, acquiring a plurality of differential current samples in a backward data window of a differential current starting point; integrating and summing the absolute values of the differential current samples to obtain a sampling point differential current integral; acquiring a plurality of zero sequence braking current samples in a backward data window and a forward data window of a differential flow starting point; integrating and summing calculation is carried out on a plurality of zero sequence braking current samples, so that a sampling point zero sequence braking current integral is obtained; and performing zero sequence braking on the differential protection of the target power system based on a proportional braking discrimination result of the sampling point differential flow integration and the sampling point zero sequence braking current integration. The invention can rapidly and accurately identify the non-fault phase CT saturation caused by fault phase current, effectively prevent the malfunction of the non-fault phase difference protection, can be used as an independent differential element locking module, and is simple and reliable and easy to realize.
Description
Technical Field
The invention relates to the technical field of relay protection of power systems, in particular to a zero sequence braking method and a zero sequence braking system for preventing malfunction of non-fault phase saturation differential protection.
Background
After a single-phase fault outside a transformer area of a power system, the fault phase current can lead to CT saturation of a non-fault phase due to the coupling effect of a large zero-sequence current of a neutral line, so that the non-fault phase generates pulse spike current with continuous several cycles, and the non-fault phase difference protection malfunction is caused. At this time, with the conventional CT saturation detection method such as the moveout method, since the non-fault phase current abrupt change and the differential current are generated simultaneously, the differential protection cannot be effectively locked. At present, a method is proposed to brake non-fault phase difference current through the braking current of a fault phase, consider faults with smaller fault current such as high resistance and the like, and increase harmonic criterion to open.
Disclosure of Invention
The invention aims to solve at least one technical problem and provide a zero sequence braking method and a zero sequence braking system for preventing malfunction of non-fault phase saturation differential protection.
In a first aspect, an embodiment of the present invention provides a zero sequence braking method for preventing malfunction of a non-fault phase saturation differential protection, which is applied to a target power system; comprising the following steps: after the differential protection of the target power system is started, acquiring a plurality of differential current samples in a backward data window of a differential current starting point; the differential flow starting point is a sampling point which meets the differential flow starting condition for the first time; the backward data window takes the sampling moment of the differential flow starting point as a starting point, and comprises the differential flow starting point, wherein the time length of the backward data window is smaller than the judging time of the differential element; integrating and summing the absolute values of the differential current samples to obtain a sampling point differential current integral; acquiring a plurality of zero sequence braking current samples in the backward data window and the forward data window of the differential flow starting point; the forward data is a sampling data window which takes the sampling moment of the differential flow starting point as an end point and does not contain the differential flow starting point, and the time length of the forward data is smaller than the judging time of the differential element; integrating and summing the multiple zero sequence braking current samples to obtain a sampling point zero sequence braking current integral; and performing zero sequence braking on the differential protection of the target power system based on a proportional braking discrimination result of the sampling point differential flow integral and the sampling point zero sequence braking current integral.
Further, the differential stream initiation condition includes: i d |>I dset The method comprises the steps of carrying out a first treatment on the surface of the Wherein I is d For differential current sampling of the differential current start point, I dset And starting a threshold value for differential protection of the target power system.
Further, performing integral summation calculation on absolute values of the differential current samples to obtain a sampling point differential current integral, including: integrating and summing absolute values of the plurality of differential current samples by:
wherein N is the number of sampling points after the differential flow starting point in the backward data window, I dTi For the ith differential current sample, I dsum Integrating the sample point differential stream.
Further, the target power system includes a plurality of sampling branches; acquiring a plurality of zero sequence braking current samples in the backward data window and the forward data window of the differential flow starting point, including: acquiring a plurality of zero sequence currents on the plurality of sampling branches at a target sampling moment; the target sampling time is one sampling time in the backward data window and the forward data window; and determining the maximum value of absolute values of the plurality of zero sequence currents as the zero sequence brake current sampling at the target sampling moment.
Further, performing integral summation calculation on the plurality of zero sequence braking current samples to obtain a sampling point zero sequence braking current integral, including: integrating and summing the plurality of zero sequence brake current samples by the following equation:
wherein 3I0 rsum For the zero sequence braking current integration of the sampling points, M is the number of sampling points in the forward data window, N is the number of sampling points after the differential flow starting point in the backward data window, and 3I0 rTi Sampling the ith zero sequence braking current.
Further, based on a proportional braking discrimination result of the sampling point differential flow integral and the sampling point zero sequence braking current integral, performing zero sequence braking on differential protection of the target power system, including: judging whether the sampling point differential flow integral and the sampling point zero sequence braking current integral meet the proportional braking judgment condition or not; if yes, locking the differential element of the target power system; if not, opening the differential element of the target power system.
Further, the proportional braking discrimination conditions include: i dsum <k*3*0 rsum The method comprises the steps of carrying out a first treatment on the surface of the Wherein I is dsum Integrating the difference stream of the sampling points, 3I0 rsum And integrating the zero sequence braking current of the sampling point, wherein k is a braking coefficient.
In a second aspect, the embodiment of the present invention further provides a zero sequence braking system for preventing malfunction of non-fault phase saturation differential protection, including: the system comprises a first acquisition module, a first calculation module, a second acquisition module, a second calculation module and a discrimination module; the first acquisition module is used for acquiring a plurality of differential current samples in a backward data window of a differential current starting point after the differential protection of the target power system is started; the differential flow starting point is a sampling point which meets the differential flow starting condition for the first time; the backward data window takes the sampling moment of the differential flow starting point as a starting point, and comprises the differential flow starting point, wherein the time length of the backward data window is smaller than the judging time of the differential element; the first calculation module is used for carrying out integral summation calculation on absolute values of the differential current samples to obtain a sampling point differential flow integral; the second acquisition module is used for acquiring a plurality of zero sequence braking current samples in the backward data window and the forward data window of the differential flow starting point; the forward data is a sampling data window which takes the sampling moment of the differential flow starting point as an end point and does not contain the differential flow starting point, and the time length of the forward data is smaller than the judging time of the differential element; the second calculation module is used for carrying out integral summation calculation on the plurality of zero sequence braking current samples to obtain zero sequence braking current integral of a sampling point; and the judging module is used for carrying out zero sequence braking on the differential protection of the target power system based on the proportional braking judging result of the sampling point differential flow integral and the sampling point zero sequence braking current integral.
In a third aspect, an embodiment of the present invention further provides an electronic device, including: a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method according to the first aspect described above when executing the computer program.
In a fourth aspect, embodiments of the present invention also provide a computer readable storage medium storing computer instructions which, when executed by a processor, implement a method as described in the first aspect above.
The invention provides a zero sequence braking method and a system for preventing non-fault phase saturation differential protection misoperation, which are used for braking through zero sequence current before the differential element is started, and based on the root cause of non-fault phase saturation, the zero sequence magnetic flux components generated by the larger zero sequence current flowing through a neutral line resistor are gradually accumulated, so that the effect of braking through adding the zero sequence current before the differential element is started is remarkable, the non-fault phase CT saturation can be rapidly and accurately identified after the differential protection is started, the rapid differential protection misoperation is effectively prevented, the differential element can be rapidly opened when the differential element is in the same time as the internal fault, and the method is simple, reliable, easy to realize and wide in applicability.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following description will briefly introduce the drawings that are needed in the detailed description or the prior art, it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a zero sequence braking method for preventing malfunction of non-fault phase saturation differential protection according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a zero sequence braking system for preventing malfunction of non-fault phase saturation differential protection according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
Fig. 1 is a flowchart of a zero sequence braking method for preventing malfunction of a non-fault phase saturation differential protection according to an embodiment of the present invention, which is applied to a target power system. As shown in fig. 1, the method specifically includes the following steps:
step S102, after the differential protection of the target power system is started, a plurality of differential current samples in a backward data window of a differential current starting point are obtained.
In the embodiment of the invention, the differential stream starting point is the first sampling point which meets the differential stream starting condition. Specifically, the differential stream start-up conditions include:
|I d |>I dset
wherein I is d For differential current sampling at the differential current start point, I dset The threshold is activated for differential protection of the target power system.
The backward data window takes the sampling moment of the differential flow starting point as a starting point and comprises the differential flow starting point and the sampling data window with the time length smaller than the judging time of the differential element.
In the embodiment of the invention, after the differential protection is started, the sampling point differential flow in a differential flow starting short data window (namely a backward data window) is calculated, the time length of the backward data window is selected to be smaller than the judgment time of the fastest differential protection, so that the CT saturation identification is ensured to lock the differential protection before the differential element is operated, and for example, the differential protection can be set to be 2 ms-3 ms.
Step S104, integrating and summing the absolute values of the differential current samples to obtain the differential current integration of the sampling points.
Specifically, the absolute values of the plurality of differential current samples are integrated and summed by the following equation:
wherein N is the number of sampling points after the differential flow starting point in the backward data window, I dTi For the ith differential current sample, I dsum Integrating the difference stream for the sampling point.
In the embodiment of the invention, N may be selected according to the sampling frequency and the time length of the data window, for example, 2-3 points may be sampled at 24 points per cycle, and 2-5 points may be sampled at 48 points per cycle. I dTi For differential flow of sample points within backward data windows, e.g. I dT0 、I dT1 …I dTN And the differential streams are sampling point differential streams at the moments T0 and T1 … TN respectively, wherein T0 is the sampling moment of the differential stream starting point.
Step S106, acquiring a plurality of zero sequence braking current samples in a backward data window and a forward data window of a differential flow starting point; the forward data is a sampling data window which takes the sampling moment of the differential flow starting point as the end point and does not contain the differential flow starting point, and the time length is smaller than the judging time of the differential element.
And S108, carrying out integral summation calculation on a plurality of zero sequence braking current samples to obtain a sampling point zero sequence braking current integral.
Specifically, the integral summation calculation is performed on a plurality of zero sequence brake current samples by the following formula:
wherein 3I0 rsum For zero sequence braking current integration of sampling points, M is the number of sampling points in a forward data window, N is the number of sampling points after a differential flow starting point in a backward data window, and 3I0 rTi Sampling the ith zero sequence braking current.
Step S110, based on the proportional braking discrimination result of the sampling point differential flow integral and the sampling point zero sequence braking current integral, the differential protection of the target power system is braked in zero sequence.
Specifically, judging whether the sampling point differential flow integral and the sampling point zero sequence braking current integral meet the proportional braking judgment condition or not;
if yes, locking a differential element of the target power system, wherein the sampling point differential flow integral is braked by the zero sequence braking current integral;
if not, the differential element of the target power system is opened, and at the moment, the sampling point differential flow integral is not braked by the zero sequence braking current integral.
Optionally, the proportional braking criterion includes:
I dsum <k*3I0 rsum
where k is the brake coefficient.
The invention provides a zero sequence braking method for preventing non-fault phase saturation differential protection misoperation, which is characterized in that zero sequence current before the differential element is started is used for braking, and based on the root cause of non-fault phase saturation, the zero sequence magnetic flux components generated by the larger zero sequence current flowing through a neutral line resistor are gradually accumulated, so that the effect of braking by adding the zero sequence current before the differential element is started is remarkable, the non-fault phase CT saturation can be rapidly and accurately identified after the differential protection is started, the rapid differential protection misoperation is effectively prevented, the differential element can be rapidly opened when the same time is in fault, and the method is simple, reliable, easy to realize and wide in applicability.
In an embodiment of the invention, the target power system comprises a plurality of sampling branches. The sampling time of the differential flow starting point is marked as the time T0, and the sampling point time after the time T0 is marked as T1 and T2 … TN in sequence.
n is the number of sides or branches, I is the number of branches, I i The instantaneous value of the current sampled for each branch.
In the embodiment of the invention, differential current sampling is performed by acquiring current instantaneous values of a plurality of sampling branches at each sampling point, and then summing the instantaneous values of the plurality of sampling branches to obtain differential current sampling corresponding to each sampling point.
In an embodiment of the present invention, sampling of zero sequence braking current includes:
acquiring a plurality of zero sequence currents on a plurality of sampling branches at a target sampling moment; the target sampling time is one sampling time in the backward data window and the forward data window;
and determining the maximum value of absolute values in the plurality of zero sequence currents as the zero sequence braking current sampling at the target sampling moment.
Specifically, the forward data window before the moment T0 and the backward data window after the moment T0 are started by the differential flow to perform zero sequence braking current calculation, the time length of the data window after the moment T0 is selected to be the same as the time length of the differential flow integration, and the time length of the forward data window at the moment T0 can be selected by referring to the time length of the backward data window at the moment T0, for example, the time length can also be selected to be 2-3 ms; the time of the forward sampling point at the moment T0 is recorded as T-1 and T-2 … T-M in sequence, and zero sequence braking current calculation is carried out on each sampling point in a data window from the moment T-M to the moment TN according to the following steps:
3I0 r ＝max{|3I0 1 |,|3I0 2 |…|3I0 n |}
i.e. zero sequence brake current sample 3I0 r Sampling point zero sequence current 3I0 of each branch i (i=1, 2 … n) and n is the number of sides or branches.
Thus, the zero sequence brake current sampling of M+N+1 sampling points is obtained through the calculation of the above formula.
When I dsum <k*3I0 rsum I.e.
The differential element is locked, otherwise the differential element is opened. k is a brake coefficient, and is selected according to the length of the data window before and after the time of starting T0, for example, when m=3 and n=2, the k value may be between 0.2 and 0.3.
As can be seen from the above description, in order to avoid rapid differential protection malfunction of the non-fault phase, the present invention provides a zero sequence braking method for preventing the malfunction of the non-fault phase saturation differential protection, wherein the root cause of the non-fault phase saturation is caused by the larger zero sequence current flowing through the neutral line, so that the method can rapidly and accurately identify the non-fault phase CT saturation caused by the fault phase current, effectively prevent the rapid differential protection malfunction, and is simple and reliable, and easy to implement.
Example two
Fig. 2 is a schematic diagram of a zero sequence braking system for preventing malfunction of a non-fault phase saturation differential protection according to an embodiment of the present invention. As shown in fig. 2, the system includes: the system comprises a first acquisition module 10, a first calculation module 20, a second acquisition module 30, a second calculation module 40 and a discrimination module 50.
Specifically, the first obtaining module 10 is configured to obtain, after the differential protection of the target power system is started, a plurality of differential current samples in a backward data window of a differential current starting point; the differential flow starting point is a sampling point which meets the differential flow starting condition for the first time; the backward data window takes the sampling moment of the differential flow starting point as a starting point and comprises the differential flow starting point and the sampling data window with the time length smaller than the judging time of the differential element.
Specifically, the differential stream start-up conditions include:
|I d |>I dset
wherein I is d For differential current sampling at the differential current start point, I dset The threshold is activated for differential protection of the target power system.
The first calculation module 20 is configured to perform integral summation calculation on absolute values of a plurality of differential current samples, so as to obtain a differential flow integral of sampling points.
Specifically, the absolute values of the plurality of differential current samples are integrated and summed by the following equation:
wherein N is the number of sampling points after the differential flow starting point in the backward data window, I dTi For the ith differential current sample, I dsum Integrating the difference stream for the sampling point.
A second acquisition module 30, configured to acquire a plurality of zero sequence braking current samples in a backward data window and a forward data window of a differential flow start point; the forward data is a sampling data window which takes the sampling moment of the differential flow starting point as the end point and does not contain the differential flow starting point, and the time length is smaller than the judging time of the differential element.
The second calculation module 40 is configured to perform integral summation calculation on the plurality of zero sequence braking current samples, so as to obtain a zero sequence braking current integral of the sampling point.
Specifically, the integral summation calculation is performed on a plurality of zero sequence brake current samples by the following formula:
wherein 3I0 rsum For sampling point zero sequence braking current integration, M is the sampling point number in the forward data window, 3I0 rTi Sampling the ith zero sequence braking current.
The discriminating module 50 is configured to perform zero sequence braking on the differential protection of the target power system based on the proportional braking discrimination result of the sampling point differential flow integration and the sampling point zero sequence braking current integration.
The invention provides a zero sequence braking system for preventing non-fault phase saturation differential protection misoperation, which is used for braking through zero sequence current before the differential element is started, and is simple, reliable, easy to realize and wide in applicability because the zero sequence magnetic flux components generated by the larger zero sequence current flowing through the neutral line resistor are gradually accumulated based on the root cause of the non-fault phase saturation, so that the effect of braking through adding the zero sequence current before the differential element is started is remarkable, the non-fault phase CT saturation can be rapidly and accurately identified after the differential protection is started, the rapid differential protection misoperation is effectively prevented, and the differential element can be rapidly opened when the same time is in fault.
Optionally, in an embodiment of the present invention, the target power system includes a plurality of sampling branches; the second acquisition module 30 is further configured to:
acquiring a plurality of zero sequence currents on a plurality of sampling branches at a target sampling moment; the target sampling time is one sampling time in the backward data window and the forward data window;
and determining the maximum value of absolute values in the plurality of zero sequence currents as the zero sequence braking current sampling at the target sampling moment.
Specifically, the discriminating module 50 is further configured to:
judging whether the sampling point differential flow integral and the sampling point zero sequence braking current integral meet the proportional braking judgment condition or not;
if yes, locking the differential element of the target power system;
if not, the differential element of the target power system is opened.
The proportional braking distinguishing conditions comprise:
I dsum <k*3I0 rsum
where k is the brake coefficient.
The embodiment of the invention also provides electronic equipment, which comprises: a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method as in the first embodiment described above when executing the computer program.
The embodiment of the invention also provides a computer readable storage medium, wherein the computer readable storage medium stores computer instructions which, when executed by a processor, implement the method in the first embodiment.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present disclosure describes embodiments, not every embodiment is provided with a separate embodiment, and that this description is provided for clarity only, and that the disclosure is not limited to the embodiments described in detail below, and that the embodiments described in the examples may be combined as appropriate to form other embodiments that will be apparent to those skilled in the art.
Claims (10)
1. A zero sequence braking method for preventing non-fault phase saturation differential protection misoperation is characterized by being applied to a target power system; comprising the following steps:
after the differential protection of the target power system is started, acquiring a plurality of differential current samples in a backward data window of a differential current starting point; the differential flow starting point is a sampling point which meets the differential flow starting condition for the first time; the backward data window takes the sampling moment of the differential flow starting point as a starting point, and comprises the differential flow starting point, wherein the time length of the backward data window is smaller than the judging time of the differential element;
integrating and summing the absolute values of the differential current samples to obtain a sampling point differential current integral;
acquiring a plurality of zero sequence braking current samples in the backward data window and the forward data window of the differential flow starting point; the forward data is a sampling data window which takes the sampling moment of the differential flow starting point as an end point and does not contain the differential flow starting point, and the time length of the forward data is smaller than the judging time of the differential element;
integrating and summing the multiple zero sequence braking current samples to obtain a sampling point zero sequence braking current integral;
and performing zero sequence braking on the differential protection of the target power system based on a proportional braking discrimination result of the sampling point differential flow integral and the sampling point zero sequence braking current integral.
2. The method according to claim 1, characterized in that: the differential stream start-up conditions include:
|I d |>I dset
wherein I is d For differential current sampling of the differential current start point, I dset And starting a threshold value for differential protection of the target power system.
3. The method according to claim 1, characterized in that: integrating and summing absolute values of the differential current samples to obtain a sampling point differential current integral, wherein the integrating and summing absolute values comprise:
integrating and summing absolute values of the plurality of differential current samples by:
wherein N is the number of sampling points after the differential flow starting point in the backward data window, I dTi For the ith differential current sample, I dsum Integrating the sample point differential stream.
4. The method according to claim 1, characterized in that: the target power system includes a plurality of sampling branches; acquiring a plurality of zero sequence braking current samples in the backward data window and the forward data window of the differential flow starting point, including:
acquiring a plurality of zero sequence currents on the plurality of sampling branches at a target sampling moment; the target sampling time is one sampling time in the backward data window and the forward data window;
and determining the maximum value of absolute values of the plurality of zero sequence currents as the zero sequence brake current sampling at the target sampling moment.
5. The method according to claim 1, characterized in that: integrating and summing the plurality of zero sequence braking current samples to obtain a sampling point zero sequence braking current integral, wherein the integrating and summing the plurality of zero sequence braking current samples comprises the following steps:
integrating and summing the plurality of zero sequence brake current samples by the following equation:
wherein 3I0 rsum For the zero sequence braking current integration of the sampling points, M is the number of sampling points in the forward data window, N is the number of sampling points after the differential flow starting point in the backward data window, and 3I0 rTi Sampling the ith zero sequence braking current.
6. The method according to claim 1, characterized in that: based on the proportional braking discrimination result of the sampling point differential flow integral and the sampling point zero sequence braking current integral, performing zero sequence braking on the differential protection of the target power system, wherein the method comprises the following steps:
judging whether the sampling point differential flow integral and the sampling point zero sequence braking current integral meet the proportional braking judgment condition or not;
if yes, locking the differential element of the target power system;
if not, opening the differential element of the target power system.
7. The method according to claim 6, wherein: the proportional braking discrimination conditions include:
I dsum <k*3I0 rsum
wherein I is dsum Integrating the difference stream of the sampling points, 3I0 rsum And integrating the zero sequence braking current of the sampling point, wherein k is a braking coefficient.
8. A zero sequence braking system for preventing malfunction of non-fault phase saturation differential protection, comprising: the system comprises a first acquisition module, a first calculation module, a second acquisition module, a second calculation module and a discrimination module; wherein,,
the first acquisition module is used for acquiring a plurality of differential current samples in a backward data window of a differential current starting point after the differential protection of the target power system is started; the differential flow starting point is a sampling point which meets the differential flow starting condition for the first time; the backward data window takes the sampling moment of the differential flow starting point as a starting point, and comprises the differential flow starting point, wherein the time length of the backward data window is smaller than the judging time of the differential element;
the first calculation module is used for carrying out integral summation calculation on absolute values of the differential current samples to obtain a sampling point differential flow integral;
the second acquisition module is used for acquiring a plurality of zero sequence braking current samples in the backward data window and the forward data window of the differential flow starting point; the forward data is a sampling data window which takes the sampling moment of the differential flow starting point as an end point and does not contain the differential flow starting point, and the time length of the forward data is smaller than the judging time of the differential element;
the second calculation module is used for carrying out integral summation calculation on the plurality of zero sequence braking current samples to obtain zero sequence braking current integral of a sampling point;
and the judging module is used for carrying out zero sequence braking on the differential protection of the target power system based on the proportional braking judging result of the sampling point differential flow integral and the sampling point zero sequence braking current integral.
9. An electronic device, comprising: memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the method according to any of claims 1-7 when the computer program is executed.
10. A computer readable storage medium storing computer instructions which, when executed by a processor, implement the method of any one of claims 1-7.
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