CA2261901A1 - Method and arrangement for optically detecting an electrical variable - Google Patents
Method and arrangement for optically detecting an electrical variable Download PDFInfo
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- CA2261901A1 CA2261901A1 CA002261901A CA2261901A CA2261901A1 CA 2261901 A1 CA2261901 A1 CA 2261901A1 CA 002261901 A CA002261901 A CA 002261901A CA 2261901 A CA2261901 A CA 2261901A CA 2261901 A1 CA2261901 A1 CA 2261901A1
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- optical measurement
- optical
- electric
- measurement
- measurement signals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
- G01R15/247—Details of the circuitry or construction of devices covered by G01R15/241 - G01R15/246
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- General Physics & Mathematics (AREA)
- Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The invention concerns a method of optically detecting an electrical variable (1 ), periodic dependency being established between the optical measuring signal and the electrical variable (I) to be measured. Accordi ng to the invention, two optical, periodically dependent measuring signals are used to obtain an unequivocal measuring signal. The result ant measured values are used as a value pair for unequivocally allocating an absolute value of the electrical variable (1).
Description
.. ~ ..
~ G~ 96 P 3586 p ~ !SA~E~' ,r~ T ~
Description ~ethod and arrangement for optical measurement of an electric variable The invention relates to a method and an arrange-ment for optical measurement of an electric variable, inparticular a current or a voltage.
Optical measurement arrangements which are based, for example, on the magnetooptic Faraday effect are known for the purpose of measuring current and voltage in electrical installations. In this case, linearly polarized measurement light is transmitted by a Faraday element arranged in the vicinity of an electric conduc-tor. The magnetic field generated by the current effects a rotation of the plane of polarization of the measure-ment light by an angle of rotation which is proportional to the path integral over the magnetic field along the path covered by the measurement light.
In the case of a continuous increase in the ~ n' ~~- 'e u-ea~u~~d, ~ ~ -~' rotation can reach 20 a value of more than 90~, 180~, 360~, and even a multiple thereof, with the result that in the case of a simple determination of the angle of rotation it is nr. possible in the evaluation to make a clear statement on the absolute value of the angle of rotation. Consequently, in practice to date it has mostly been only changes in the angle of rotation in a unique range, for example up to 90~, which have been p~rm$tted, and these have been evaluated in a correspsn~;ngly sensitive fashion.
EP O 208 593 Bl discloses a magnetooptic current transformer in which, after traversing a Faraday optical fibre surro~n~i n~ an electrical conductor, linearly polarized measurement light is split by a beam splitter into two component light signals, and each of these light signals is fed to an analyzer. The inherent axes of the two analyzers are aligned at an angle of 0~ or 45~ to the launch polarization of the measurement light. The result is a first, sinusoidal signal at the output of one analyzer and a second, cosinusoidal signal at the output i of the other analyzer.
Theee two signals are in each case ambiguous, oscillating functions of the current in the electric conductor, which are phase-shifted relative to one another by an angle of 90~. A unique measurement signal is now composed from the two amhiguous signals by com-paring the sign and the absolute values of the measured value of the first sinusoidal signal and the second cosinusoidal signal. As soon as the absolute values of sine and cosine are equal, that is to say in the case of an integral multiple of 45~, a switchover is made, as a function of the sign of sine and cosine, from a unique branch of the fir~t, sinusoidal signal into a unique branch of the second, sinusoid~l signal, or ~ice versa.
This procedure is an incremental procedure, with the result that the operating point must again be reset in the event of a current zero, in the event of a failure of the electronic system of a current transformer. See also DE 43 34 469 A1 or DE 43 42 410 Al in this regard.
German Patent Application 195 44 778 proposes a method which makes use of two component measurements. ~-measure the electric measured variable in a prescribed measuring range, a first measurement signal, which is a unique function of the measured variable over the measur-ing range, and a second measurement signal, which is a periodic and non-unique function of the measured variable in the prescribed measuring range, are generated. A third measurement Oi~ai ~ w~icn is unique over the measuring range and has at least the measurement resolution of the second measurement signal, is derived from the two measurement signals. An absolute value can be determ; r~9~
in this way, at least for the unique range of the first measurement signal. In general, reference is further made to the prior art in accordance with US 4,529,875, DE 40 13 125 Al and EP 0 290 780.
It is the object of the invention to specify a method and an arrangement for measuring ~n electric variable using optical means, it being possible to evaluate the optical measurement signals beyond 90~ in a .
simple way.
The object is achieved according to the invention by means of a method for optical measurement of an electric variable, - at least a first and a second optical measurement signal being generated as a function of the electric variable, - the depPn~ence of the two optical measurement signals on the electric variable being periodic, and one period being longer than and at most twice as long as the other, and - the two measurement signals serving the purpose of a pair of values to which an absolute value for the electric variable is assigned.
By comparison with the prior art, using the new method any desired ~YpAn~ion of the measuring range is performed beyond the uniqueness range (lst quadrant). The determination of the electric variable is performed in this case at any time without storage of the prehistory or of the previous measured values, since there is no incremental procedure. It is favour~ in this case if the periodicities of the characteristics of the two measurement signals are situated close to ore snother.
The depen~sncies of the optical measurement signals should differ in this case in such a way that there is a change in the phase shift between the measurement signals in the event of an increase in the electric variable to ba maasured. _~ appropri-te, the measurement signals can, for example, also have a linear or nonlinear dep~n~ence.
It is favourable if there are derived from the optical measurement signals electric measurement signals which serve as a pair of values. Simple digital proces-sing of measured values is possible in this way. In addition, disturbing influences on the optical signal, for example vibrations and temperature, are then pre-vented. Preproce~sing by means of various algorithms to give electric signals can advantageously lead to "normalization of intensity", as a result of which compen~ation of the disturbing effects ia poa~ible.
.
. .
It iB expedient if the two optical measurement signals are generated by measurement light of different frequency. Only one optical sensor or only one measure-ment system i8 required in this way. The depen~ence of the Faraday effect on the wavelength of t~e light is used in this case. Two sensitivities are thus achieved there-by.
The two optical measurement signals can in this case be generated simultaneously or one after another, in particular in a multiplex fashion. In the case of simul-taneous measurement, the measurement signals can be generated simultaneously and separately. Fewer components are required in the case of a multiplex design.
It is advantageously possible for the two optical measurement signals to be generated one after another by continuous variation, in particular by wobbling, of the periodicity of one measurement signal. This produces the continuous transition between the two measurement si-gnals, which in principle permits an infinite multiple of measurement signal~, as a rQsult of w~ch the measurement accuracy and uniqueness of the measurement are particularly high.
The optical measurement signals can be generated by means of different light sensors. Separate generation of measurement signals is possible thereby. The measure-ment signals can also be generated by means of a common light sensor which comprises two light paths. This mode of procedur~ is very simple, the expendituro on compo-nents being low.
In addition, a further measurement signal can be generated whose dep~n~nre on the electric variable is periodic and which serves the purpose of more accurately determining the electric variable. A further enh~ncement of the uniqueness and the accuracy of the measurement signal is provided in this way. A current or a voltage is advantageously suitable as an electric variable.
According to the invention, the object with regard to the arrangement is achieved by means of an arrangement for measurement of an electric variable on a .
, conductor, having:
- at least a first optical sensor which generates at least two optical measurement signals, the depen-dence of the measurement signals on the electric variable being periodic, and one period being longer than and at most twice as long as the other, and - an evaluation device, which is connected to the sensor and generates for the two optical measurement signals serving as a pair of values an assigned absolute value for the electric variable.
This arrangement is particularly simple in design and permits a substantial eYran~ion of the uniqueness range in measurement. Further advantageous embodiments are specified in the rema;ning patent claims. The adv_ntages already mentioned above for the mothod apply analogously for the arrangement.
The sensor can have at least two optical measuring paths of different optical properties for generating the optical measurement signals. The two measurement signals can therefore be generated simply, there being little need for outlay -~ the sensor. It is simple if the two measurement paths are formed by dif-ferent materials. It is possible in this ca~e to achieve a small overall size. Alternatively, the two measurement paths can be of different length, the outlay on material is kept low in this case.
The optical sensor can be of multipart design in accG.~ance with ts nu~e- Or measurement paths. A simple modular design is possible thereby.
It can also be possible to switch over or change the optical properties of the sensor in order to generate the optical measurement signals. The sensor thereby becomes an active element of the arrangement, it being possible to generate any desired number of optical measurement signals by means of only one sensor and its drive circuit.
The sensor can advantageously generate a further measurement signal wh~ch, supplementing the pair of values, serves to generate the value for the electric variable. The measurement accuracy and uniqueness are improved again thereby.
The sensor can be assigned a light source of which the frequency can be periodically varied conti-nuously, in particular in the sense of wobbling, for thepurpose of generating the two light signals. A continuous spectrum of measurement signals can thereby be generated in principle.
Exemplary embodiments of the invention, further details and advantages are explained in more detail below with the aid of the drawing, in which:
Figure 1 shows an arrangement for optical measurement of an electric signal, and Figure 2 show~ a characteristic diagram for two measure-ment signals.
The first step is a general explanation of the new method with the aid of a representation of the principle of an arrangement in accordance with Figure 1.
The aim of the new method is to render it possible to use polarimetric sensor~ to mea~uFe uni~ely startina from non-unique measurement signals.
Figure 1 shows a conductor 1 which conducts a cu rent I with a voltage ~. Arranged on the conductor 1 i8 a sensor 3 which operates on an optical basis. The mode of operation can, for example, be based on the Faraday effect or on the Pockels effect. The aim in this case is to measure the current I or the voltage ~. By way of example, it will ~e assumed in thi~ ca~e that measure-ment of current is in question.
The sensor 3 is connected via an optical fibre 5 to a light source 7 which feeds the ~ensor 3 a polari-zed light. The polarization of the polarized light is varied in the sensor 3 as a function of the electric variable I, in particular its plane of polarization is rotated, and then fed to an evaluation device 11 via a second optical fibre 9. Of course, it i8 also possible to u~e arrangements in which the sensor, polarizer and analyzer form a structural unit.
The rotation of the plane of polarization genera-ted in the case of the measurement signal is determined in the evaluation device 11. The rotation is in this case a measure of the electric variable to be measured.
In the present case, the first sensor 3 supplies a periodic output signal. That is to say, in the case of electric variables which effect a phase rotation beyond 90~, the measurement signal is no longer unique. The following procedure is adopted for the purpose of uniquely measuring the electric variable:
The first step is to generate two optical measu-rement signals. The dep~n~nce of the two optical measu-rement signals on the electric variable, specifically the current I, is periodic in each case, it being the case, however, that one period is longer than, but at most twice as long as the other. The result is an only slightly different sensitivity in the two-fold acquisi-tion of the measured value of the electric variable.
Depen~ ng on the instantaneous value of the electric variable, the different sensitivities in the case of measurement mean that the two optical measurement signals have different amplitude val~ which are in each case not unique per se. The absolute value of the elec-tric variable can be determined by subsequer' ~.rocessing or assessment of these two values on the basis of mathe-matical considerations or with the aid of tabular com-parisons or assignments. The sensitivities or depen-dencies of the two measurement signals are such that ,here i8 a changa -n ~he phase shift between the measure-ment signals giving a change in the electric variable to be measured.
Various methods are available for generating the two optical measurement signals. For example, for this purpose the light source 7 can emit measurement light of different frequencies. This can be performed simulta-neously, with the result that the two optical measurementsignals can also be detectod simultaneously.
Alternatively, a multiplex mode of procedure (referred to the light transmitter end or the evaluation device end) i8 al80 conceiv ble. Varying the light frequency by means .
of a wobble method can also be favourable in this case.
Starting from measurement light which has only one frequency and is fed to the sensor 3, it is also conceivable to construct the sensor 3 per se for the purpose of forming two optical measurement signals. For example, for this purpose it can comprise two light paths which both have different optical properties and to which a common measurement light is fed.
In the simplest case, it would be possible, for example, to conceive of a fibre coil which has a tap, with the result that two outputs are provided. Light paths of different lengths would be formed in this way.
Of course, it i8 also possible to have two completely separate light paths which are formed from identical materials of different dimensions, or of different materials. The sensitivity of the sensor can be adjusted in principle using the number of the wind;ngs of the fibre coil.
As a further variant, Figure 1 shows in a ~R~e~
representation a control deYice 1~ wh~ch permits the first sensor 3 to be controlled or switched over vi- a line of action 15. This design would be obvious for ~ltiplex measured-value acquisition, in which the optical properties of the sensor 3 are continuously switched over or continuously reversed ao that different measurement signals are generated alternately. Of course, the evaluation device 11 must be synchronized for this purpose witn the control device 1;. Aa an alternative to this, it is also possible that the light source 7 can be switched over or continuously reversed.
Figure 2 shows a diagram with two characteristics M1 and M2 of two measurement signals. The measurement signal can be understood here as the optical measurement signals or the electric measurement signals already derived therefrom and which are normally used to carry out electronic, in particular digital processing of measured values.
The characteristics M1 and M2 represent amplitude characteristics correspon~ing to the variation in angle , .
.
GR 96 P 3586 P - g -of rotation as a function of the electric variable to be measured. It is to be seen in this case that both charac-teristics M1 and M2 are periodic between a minimum and a m-Y;mll~ value, MIN and MAX, respectively, and have periods which differ slightly from one another. The characteristics shown represent, as it were, the charac-teristic diagrams for measuring the two optical measured values.
However, for a prescribed value of the electric variable the respective amplitude values are not unique in themselves. In principle, it is possible to determine a unique value with the aid of two variables. It is favourable for this purpose if the periods of the two characteristics lie close together, with the result that it is possible to make unique measuremsnts for many quadrants.
A possibility for determining the exact value resides in determining the phase shift in the character-istics from the two signals. The phase shift, and thus the value of the electric variable, can be determined, for example, in accoraance Wlt~ following relation-ship:
The value of the electric variable =
8( 2 sin (ArcSln (Pl) ~ + ArcSln (~2 ) ,~ ) 8ere, P1 and P2 signify the values of the measurem-nt signals dete~;ne~ in the manner of a pair of values, and R ~ignifies a prescribable factor.
A further possibility for determining the abso-lute value of the electric variable would be using a table to compare the measured values determined with stored pairs of values. For this purpose, the measured values can serve as tabular address for f;n~;ng the correspQn~;ng value of the electric vari~ble. In addi-tion, it would alao be possibl- to employ a comparison of the polar$tios of th- respective amplitud- values, and the difference in the amplitudes to d-termine the ~lec-.
.
tric variable.
The determination of the absolute value of the electric variable can also be performed in a direct way, specifically by calculating from the two available S measured values using general mathematical methods with the aid of appropriate algorithms.
As the case may be, it is also ad~antageously possible to take account of the en~elope of the beating of the two characteristics, the result being a unique determination of the electric variable. This basic idea is already at least taken into account in princ~ple in the abovenamed relationship.
~ sing future materials and methods, it is also conceivable, as the case may be, to generate or acquire measured values uniquely using a controllable sensor which modulates the measurement light with suitable methods and can thereby generate, if appropriate, further measurement information, for example temperature.
Of course, the specified features of the method and of the arrangement can be combined with one another or with features according to the prior art wi~ t departing from the basic concept of the present idea. It is essential for this purpose that a conclusion is obt~; ne~ concerning the original electric variable by starting from two non-unique measurement signals.
A preferred application of the measurem-nt method and of the arrangoment is in optical measurement of current a~d v~ltage. in particular for high voltage or medium voltage. It is possible thereby to acquire measured variaDles over a wide measu-ing range using only one sensor.
~ G~ 96 P 3586 p ~ !SA~E~' ,r~ T ~
Description ~ethod and arrangement for optical measurement of an electric variable The invention relates to a method and an arrange-ment for optical measurement of an electric variable, inparticular a current or a voltage.
Optical measurement arrangements which are based, for example, on the magnetooptic Faraday effect are known for the purpose of measuring current and voltage in electrical installations. In this case, linearly polarized measurement light is transmitted by a Faraday element arranged in the vicinity of an electric conduc-tor. The magnetic field generated by the current effects a rotation of the plane of polarization of the measure-ment light by an angle of rotation which is proportional to the path integral over the magnetic field along the path covered by the measurement light.
In the case of a continuous increase in the ~ n' ~~- 'e u-ea~u~~d, ~ ~ -~' rotation can reach 20 a value of more than 90~, 180~, 360~, and even a multiple thereof, with the result that in the case of a simple determination of the angle of rotation it is nr. possible in the evaluation to make a clear statement on the absolute value of the angle of rotation. Consequently, in practice to date it has mostly been only changes in the angle of rotation in a unique range, for example up to 90~, which have been p~rm$tted, and these have been evaluated in a correspsn~;ngly sensitive fashion.
EP O 208 593 Bl discloses a magnetooptic current transformer in which, after traversing a Faraday optical fibre surro~n~i n~ an electrical conductor, linearly polarized measurement light is split by a beam splitter into two component light signals, and each of these light signals is fed to an analyzer. The inherent axes of the two analyzers are aligned at an angle of 0~ or 45~ to the launch polarization of the measurement light. The result is a first, sinusoidal signal at the output of one analyzer and a second, cosinusoidal signal at the output i of the other analyzer.
Theee two signals are in each case ambiguous, oscillating functions of the current in the electric conductor, which are phase-shifted relative to one another by an angle of 90~. A unique measurement signal is now composed from the two amhiguous signals by com-paring the sign and the absolute values of the measured value of the first sinusoidal signal and the second cosinusoidal signal. As soon as the absolute values of sine and cosine are equal, that is to say in the case of an integral multiple of 45~, a switchover is made, as a function of the sign of sine and cosine, from a unique branch of the fir~t, sinusoidal signal into a unique branch of the second, sinusoid~l signal, or ~ice versa.
This procedure is an incremental procedure, with the result that the operating point must again be reset in the event of a current zero, in the event of a failure of the electronic system of a current transformer. See also DE 43 34 469 A1 or DE 43 42 410 Al in this regard.
German Patent Application 195 44 778 proposes a method which makes use of two component measurements. ~-measure the electric measured variable in a prescribed measuring range, a first measurement signal, which is a unique function of the measured variable over the measur-ing range, and a second measurement signal, which is a periodic and non-unique function of the measured variable in the prescribed measuring range, are generated. A third measurement Oi~ai ~ w~icn is unique over the measuring range and has at least the measurement resolution of the second measurement signal, is derived from the two measurement signals. An absolute value can be determ; r~9~
in this way, at least for the unique range of the first measurement signal. In general, reference is further made to the prior art in accordance with US 4,529,875, DE 40 13 125 Al and EP 0 290 780.
It is the object of the invention to specify a method and an arrangement for measuring ~n electric variable using optical means, it being possible to evaluate the optical measurement signals beyond 90~ in a .
simple way.
The object is achieved according to the invention by means of a method for optical measurement of an electric variable, - at least a first and a second optical measurement signal being generated as a function of the electric variable, - the depPn~ence of the two optical measurement signals on the electric variable being periodic, and one period being longer than and at most twice as long as the other, and - the two measurement signals serving the purpose of a pair of values to which an absolute value for the electric variable is assigned.
By comparison with the prior art, using the new method any desired ~YpAn~ion of the measuring range is performed beyond the uniqueness range (lst quadrant). The determination of the electric variable is performed in this case at any time without storage of the prehistory or of the previous measured values, since there is no incremental procedure. It is favour~ in this case if the periodicities of the characteristics of the two measurement signals are situated close to ore snother.
The depen~sncies of the optical measurement signals should differ in this case in such a way that there is a change in the phase shift between the measurement signals in the event of an increase in the electric variable to ba maasured. _~ appropri-te, the measurement signals can, for example, also have a linear or nonlinear dep~n~ence.
It is favourable if there are derived from the optical measurement signals electric measurement signals which serve as a pair of values. Simple digital proces-sing of measured values is possible in this way. In addition, disturbing influences on the optical signal, for example vibrations and temperature, are then pre-vented. Preproce~sing by means of various algorithms to give electric signals can advantageously lead to "normalization of intensity", as a result of which compen~ation of the disturbing effects ia poa~ible.
.
. .
It iB expedient if the two optical measurement signals are generated by measurement light of different frequency. Only one optical sensor or only one measure-ment system i8 required in this way. The depen~ence of the Faraday effect on the wavelength of t~e light is used in this case. Two sensitivities are thus achieved there-by.
The two optical measurement signals can in this case be generated simultaneously or one after another, in particular in a multiplex fashion. In the case of simul-taneous measurement, the measurement signals can be generated simultaneously and separately. Fewer components are required in the case of a multiplex design.
It is advantageously possible for the two optical measurement signals to be generated one after another by continuous variation, in particular by wobbling, of the periodicity of one measurement signal. This produces the continuous transition between the two measurement si-gnals, which in principle permits an infinite multiple of measurement signal~, as a rQsult of w~ch the measurement accuracy and uniqueness of the measurement are particularly high.
The optical measurement signals can be generated by means of different light sensors. Separate generation of measurement signals is possible thereby. The measure-ment signals can also be generated by means of a common light sensor which comprises two light paths. This mode of procedur~ is very simple, the expendituro on compo-nents being low.
In addition, a further measurement signal can be generated whose dep~n~nre on the electric variable is periodic and which serves the purpose of more accurately determining the electric variable. A further enh~ncement of the uniqueness and the accuracy of the measurement signal is provided in this way. A current or a voltage is advantageously suitable as an electric variable.
According to the invention, the object with regard to the arrangement is achieved by means of an arrangement for measurement of an electric variable on a .
, conductor, having:
- at least a first optical sensor which generates at least two optical measurement signals, the depen-dence of the measurement signals on the electric variable being periodic, and one period being longer than and at most twice as long as the other, and - an evaluation device, which is connected to the sensor and generates for the two optical measurement signals serving as a pair of values an assigned absolute value for the electric variable.
This arrangement is particularly simple in design and permits a substantial eYran~ion of the uniqueness range in measurement. Further advantageous embodiments are specified in the rema;ning patent claims. The adv_ntages already mentioned above for the mothod apply analogously for the arrangement.
The sensor can have at least two optical measuring paths of different optical properties for generating the optical measurement signals. The two measurement signals can therefore be generated simply, there being little need for outlay -~ the sensor. It is simple if the two measurement paths are formed by dif-ferent materials. It is possible in this ca~e to achieve a small overall size. Alternatively, the two measurement paths can be of different length, the outlay on material is kept low in this case.
The optical sensor can be of multipart design in accG.~ance with ts nu~e- Or measurement paths. A simple modular design is possible thereby.
It can also be possible to switch over or change the optical properties of the sensor in order to generate the optical measurement signals. The sensor thereby becomes an active element of the arrangement, it being possible to generate any desired number of optical measurement signals by means of only one sensor and its drive circuit.
The sensor can advantageously generate a further measurement signal wh~ch, supplementing the pair of values, serves to generate the value for the electric variable. The measurement accuracy and uniqueness are improved again thereby.
The sensor can be assigned a light source of which the frequency can be periodically varied conti-nuously, in particular in the sense of wobbling, for thepurpose of generating the two light signals. A continuous spectrum of measurement signals can thereby be generated in principle.
Exemplary embodiments of the invention, further details and advantages are explained in more detail below with the aid of the drawing, in which:
Figure 1 shows an arrangement for optical measurement of an electric signal, and Figure 2 show~ a characteristic diagram for two measure-ment signals.
The first step is a general explanation of the new method with the aid of a representation of the principle of an arrangement in accordance with Figure 1.
The aim of the new method is to render it possible to use polarimetric sensor~ to mea~uFe uni~ely startina from non-unique measurement signals.
Figure 1 shows a conductor 1 which conducts a cu rent I with a voltage ~. Arranged on the conductor 1 i8 a sensor 3 which operates on an optical basis. The mode of operation can, for example, be based on the Faraday effect or on the Pockels effect. The aim in this case is to measure the current I or the voltage ~. By way of example, it will ~e assumed in thi~ ca~e that measure-ment of current is in question.
The sensor 3 is connected via an optical fibre 5 to a light source 7 which feeds the ~ensor 3 a polari-zed light. The polarization of the polarized light is varied in the sensor 3 as a function of the electric variable I, in particular its plane of polarization is rotated, and then fed to an evaluation device 11 via a second optical fibre 9. Of course, it i8 also possible to u~e arrangements in which the sensor, polarizer and analyzer form a structural unit.
The rotation of the plane of polarization genera-ted in the case of the measurement signal is determined in the evaluation device 11. The rotation is in this case a measure of the electric variable to be measured.
In the present case, the first sensor 3 supplies a periodic output signal. That is to say, in the case of electric variables which effect a phase rotation beyond 90~, the measurement signal is no longer unique. The following procedure is adopted for the purpose of uniquely measuring the electric variable:
The first step is to generate two optical measu-rement signals. The dep~n~nce of the two optical measu-rement signals on the electric variable, specifically the current I, is periodic in each case, it being the case, however, that one period is longer than, but at most twice as long as the other. The result is an only slightly different sensitivity in the two-fold acquisi-tion of the measured value of the electric variable.
Depen~ ng on the instantaneous value of the electric variable, the different sensitivities in the case of measurement mean that the two optical measurement signals have different amplitude val~ which are in each case not unique per se. The absolute value of the elec-tric variable can be determined by subsequer' ~.rocessing or assessment of these two values on the basis of mathe-matical considerations or with the aid of tabular com-parisons or assignments. The sensitivities or depen-dencies of the two measurement signals are such that ,here i8 a changa -n ~he phase shift between the measure-ment signals giving a change in the electric variable to be measured.
Various methods are available for generating the two optical measurement signals. For example, for this purpose the light source 7 can emit measurement light of different frequencies. This can be performed simulta-neously, with the result that the two optical measurementsignals can also be detectod simultaneously.
Alternatively, a multiplex mode of procedure (referred to the light transmitter end or the evaluation device end) i8 al80 conceiv ble. Varying the light frequency by means .
of a wobble method can also be favourable in this case.
Starting from measurement light which has only one frequency and is fed to the sensor 3, it is also conceivable to construct the sensor 3 per se for the purpose of forming two optical measurement signals. For example, for this purpose it can comprise two light paths which both have different optical properties and to which a common measurement light is fed.
In the simplest case, it would be possible, for example, to conceive of a fibre coil which has a tap, with the result that two outputs are provided. Light paths of different lengths would be formed in this way.
Of course, it i8 also possible to have two completely separate light paths which are formed from identical materials of different dimensions, or of different materials. The sensitivity of the sensor can be adjusted in principle using the number of the wind;ngs of the fibre coil.
As a further variant, Figure 1 shows in a ~R~e~
representation a control deYice 1~ wh~ch permits the first sensor 3 to be controlled or switched over vi- a line of action 15. This design would be obvious for ~ltiplex measured-value acquisition, in which the optical properties of the sensor 3 are continuously switched over or continuously reversed ao that different measurement signals are generated alternately. Of course, the evaluation device 11 must be synchronized for this purpose witn the control device 1;. Aa an alternative to this, it is also possible that the light source 7 can be switched over or continuously reversed.
Figure 2 shows a diagram with two characteristics M1 and M2 of two measurement signals. The measurement signal can be understood here as the optical measurement signals or the electric measurement signals already derived therefrom and which are normally used to carry out electronic, in particular digital processing of measured values.
The characteristics M1 and M2 represent amplitude characteristics correspon~ing to the variation in angle , .
.
GR 96 P 3586 P - g -of rotation as a function of the electric variable to be measured. It is to be seen in this case that both charac-teristics M1 and M2 are periodic between a minimum and a m-Y;mll~ value, MIN and MAX, respectively, and have periods which differ slightly from one another. The characteristics shown represent, as it were, the charac-teristic diagrams for measuring the two optical measured values.
However, for a prescribed value of the electric variable the respective amplitude values are not unique in themselves. In principle, it is possible to determine a unique value with the aid of two variables. It is favourable for this purpose if the periods of the two characteristics lie close together, with the result that it is possible to make unique measuremsnts for many quadrants.
A possibility for determining the exact value resides in determining the phase shift in the character-istics from the two signals. The phase shift, and thus the value of the electric variable, can be determined, for example, in accoraance Wlt~ following relation-ship:
The value of the electric variable =
8( 2 sin (ArcSln (Pl) ~ + ArcSln (~2 ) ,~ ) 8ere, P1 and P2 signify the values of the measurem-nt signals dete~;ne~ in the manner of a pair of values, and R ~ignifies a prescribable factor.
A further possibility for determining the abso-lute value of the electric variable would be using a table to compare the measured values determined with stored pairs of values. For this purpose, the measured values can serve as tabular address for f;n~;ng the correspQn~;ng value of the electric vari~ble. In addi-tion, it would alao be possibl- to employ a comparison of the polar$tios of th- respective amplitud- values, and the difference in the amplitudes to d-termine the ~lec-.
.
tric variable.
The determination of the absolute value of the electric variable can also be performed in a direct way, specifically by calculating from the two available S measured values using general mathematical methods with the aid of appropriate algorithms.
As the case may be, it is also ad~antageously possible to take account of the en~elope of the beating of the two characteristics, the result being a unique determination of the electric variable. This basic idea is already at least taken into account in princ~ple in the abovenamed relationship.
~ sing future materials and methods, it is also conceivable, as the case may be, to generate or acquire measured values uniquely using a controllable sensor which modulates the measurement light with suitable methods and can thereby generate, if appropriate, further measurement information, for example temperature.
Of course, the specified features of the method and of the arrangement can be combined with one another or with features according to the prior art wi~ t departing from the basic concept of the present idea. It is essential for this purpose that a conclusion is obt~; ne~ concerning the original electric variable by starting from two non-unique measurement signals.
A preferred application of the measurem-nt method and of the arrangoment is in optical measurement of current a~d v~ltage. in particular for high voltage or medium voltage. It is possible thereby to acquire measured variaDles over a wide measu-ing range using only one sensor.
Claims (16)
1. Method for optical measurement of an electric variable whereby:
a) at least a first and a second optical measurement signal being generated as a function of the electric variable b) the dependencies of the two optical measurement signals on the electric variable being periodic in each case, c) electric measurement signals which serve as a pair of values being derived from the optical measurement signals.
characterized in that, d) the period of dependence of one optical measurement signal of the electric variable being longer than and at most twice as long as the period of the other optical measurement signal, and e) an absolute value for the electric variable being determined e1) according to the relation whereby P1, P2 represent the values of the electric measurement signal and K represents a prescribable factor e2) or by a tabular comparison of the electric measurement value with deposited value pairs.
a) at least a first and a second optical measurement signal being generated as a function of the electric variable b) the dependencies of the two optical measurement signals on the electric variable being periodic in each case, c) electric measurement signals which serve as a pair of values being derived from the optical measurement signals.
characterized in that, d) the period of dependence of one optical measurement signal of the electric variable being longer than and at most twice as long as the period of the other optical measurement signal, and e) an absolute value for the electric variable being determined e1) according to the relation whereby P1, P2 represent the values of the electric measurement signal and K represents a prescribable factor e2) or by a tabular comparison of the electric measurement value with deposited value pairs.
2. Method according to claim 1, characterized in that the two optical measurement signals are generated by measurement light of different frequency.
3. Method according to claim 1 or 2, characterized in that the two optical measurement signals are generated simultaneously or one after another, in particular in a multiplex fashion.
4. Method according to claim 3, characterized in that the two optical measurement signals are generated one after another by continuously varying, in particular continuously wobbling, the periodicity of one signal.
5. Method according to one of claims 1 to 4, characterized in that the optical measurement signals are generated by means of different light sensors.
6. Method according to one of claims 1 to 4, characterized in that the optical measurement signals are generated by means of a common light sensor (3) which comprises two light paths.
7. Method according to one of claims 1 to 6, characterized in that a further optical measurement signal are generated whose dependence on the electric variable is periodic, and which serves the purpose of determining the electric variable more accurately.
8. Method according to one of claims 1 to 7, characterized in that the electric variable is a current or a voltage.
9. Arrangement for measurement of an electric variable (1) on a conductor (1), having:
a) at least a first optical sensor (3) which generates at least two optical measurement signals, the dependence of the measurement signals on the electric variable (I) being periodic, b) an evaluation device (11) which is connected to the sensor (3), and which has means for converting the two optical measurement signals in electric measurement signals which serve as a pair of values, characterized in that c) the period of dependence of one optical measurement signal of the electric variable (I) being longer than and at most twice as long as the period of the other optical measurement signal, and d) the evaluation device (11) having means for determining the absolute value d1) according to the relation whereby P, P2 represent the values of the electric measurement signal and K represents a prescribable factor d2) or by a tabular comparison of the electric measurement values with deposited value pairs.
a) at least a first optical sensor (3) which generates at least two optical measurement signals, the dependence of the measurement signals on the electric variable (I) being periodic, b) an evaluation device (11) which is connected to the sensor (3), and which has means for converting the two optical measurement signals in electric measurement signals which serve as a pair of values, characterized in that c) the period of dependence of one optical measurement signal of the electric variable (I) being longer than and at most twice as long as the period of the other optical measurement signal, and d) the evaluation device (11) having means for determining the absolute value d1) according to the relation whereby P, P2 represent the values of the electric measurement signal and K represents a prescribable factor d2) or by a tabular comparison of the electric measurement values with deposited value pairs.
10. Arrangement according to claim 9,.characterized in that the sensor (3) has at least two optical measurement paths of different optical properties for the purpose of generating the optical measurement signals.
11. Arrangement according to claim 10, characterized in that the two measurement paths are formed by different materials.
12. Arrangement according to claim 10, characterized in that the two measurement paths are of different length.
13. Arrangement according to claim 10, 11 or 12, characterized in that the optical sensor (3) is of multipart design in accordance with its number of measurement paths.
14. Arrangement according to claim 9, characterized in that it is possible to switch over or change the optical properties of the sensor (3) in order to generate the optical measurement signals.
15. Arrangement according to one of claims 9 to 14, characterized in that the sensor (3) is assigned a light source (7) of which the frequency can be periodically varied continuously, in particular in the sense of wobbling, for the purpose of generating the two light signals.
16. Arrangement according to one of claims 9 to 15, characterized in that the sensor (3) generates a further optical measurement signal which, in supplementing the pair of values, serves to generate the value for the electric variable.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19631138 | 1996-08-01 | ||
| DE19631138.1 | 1996-08-01 | ||
| PCT/DE1997/001480 WO1998005975A1 (en) | 1996-08-01 | 1997-07-14 | Method and arrangement for optically detecting an electrical variable |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2261901A1 true CA2261901A1 (en) | 1998-02-12 |
Family
ID=7801529
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002261901A Abandoned CA2261901A1 (en) | 1996-08-01 | 1997-07-14 | Method and arrangement for optically detecting an electrical variable |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0916095A1 (en) |
| CN (1) | CN1230257A (en) |
| CA (1) | CA2261901A1 (en) |
| WO (1) | WO1998005975A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE59904579D1 (en) | 1998-12-22 | 2003-04-17 | Siemens Ag | METHOD AND ARRANGEMENT FOR OPTICALLY DETECTING AN ELECTRICAL CURRENT VIA LIGHT SIGNALS WITH DIFFERENT WAVELENGTH |
| DE10039455A1 (en) * | 2000-08-12 | 2002-02-21 | Abb Patent Gmbh | DC converter |
| WO2011154029A1 (en) | 2010-06-07 | 2011-12-15 | Abb Research Ltd | High-voltage sensor with axially overlapping electrodes |
| RU2677126C2 (en) | 2014-02-21 | 2019-01-15 | Абб Швайц Аг | Interferometric sensor |
| CN106062506B (en) | 2014-02-21 | 2021-06-01 | Abb电网瑞士股份公司 | Interferometric sensor |
| CN111474553B (en) * | 2020-06-22 | 2020-11-27 | 深圳市汇顶科技股份有限公司 | Time-of-flight ranging method and device |
| DE102022210973B4 (en) * | 2022-10-18 | 2025-04-03 | Hsp Hochspannungsgeräte Gmbh | Measuring an electric current |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3141325A1 (en) * | 1981-10-17 | 1983-04-28 | BBC Aktiengesellschaft Brown, Boveri & Cie., 5401 Baden, Aargau | Method for measuring the current on an electric conductor by means of the Faraday effect |
| US5963026A (en) * | 1994-08-23 | 1999-10-05 | Siemens Aktiengesellschaft | Method and device for the measurement of electric currents in at least two measuring ranges |
-
1997
- 1997-07-14 EP EP97934422A patent/EP0916095A1/en not_active Ceased
- 1997-07-14 CN CN 97197759 patent/CN1230257A/en active Pending
- 1997-07-14 CA CA002261901A patent/CA2261901A1/en not_active Abandoned
- 1997-07-14 WO PCT/DE1997/001480 patent/WO1998005975A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0916095A1 (en) | 1999-05-19 |
| WO1998005975A1 (en) | 1998-02-12 |
| CN1230257A (en) | 1999-09-29 |
| WO1998005975A8 (en) | 1999-05-27 |
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