ARRANGEMENT INCLUDING A MEASURING DEVICE AND METHOD FOR ITS OPERATION

Description

[0001] The invention relates to arrangements with measuring devices that are suitable for measuring an output signal provided by a measuring unit, which describes an operating variable of a technical system, and for generating a measured value. Furthermore, the invention relates to methods for operating such arrangements.

[0002] In medium- and high-voltage grids, currents are typically measured using measuring units in the form of current transformers / sensors. On the one hand, currents are measured (with lower accuracy) to provide protective devices with operating values; on the other hand, grid operators increasingly want to use precise current measurements (together with voltage measurements) for energy / power calculations. In the future, (wide-range) small-signal transformers will also be increasingly used. Due to increased cost pressure, one goal is to be able to use the same or identically constructed transformers / sensors for both applications. This could reduce component costs, wiring effort, and operating costs.

[0003] Furthermore, even in pure protection device applications, there are increasingly stringent demands on the accuracy of current measurements. In particular, lower operating currents result in greater inaccuracies in both amplitude and phase position. This leads to deviations in power measurements and potentially to inaccuracies in various protection functions.

[0004] The invention is based on the object of improving arrangements of the type described with regard to the requirements for the working accuracy of connected measuring units.

[0005] This object is achieved according to the invention by an arrangement having the features according to claim 1 and by a method according to claim 12. Advantageous embodiments of the arrangement according to the invention are specified in the subclaims.

[0006] According to the invention, the arrangement comprises a correction unit which is designed to correct the measured value generated by the measuring device in accordance with a correction instruction assigned to the individual measuring unit and to generate a corrected measured value, wherein the degree of correction in accordance with the individual measuring unit correction instruction depends on the measured value generated by the measuring device and / or on the level of another operating variable of the technical installation.

[0007] A key advantage of the arrangement according to the invention is that, through the measurement-unit-specific and operating-variable-dependent correction based on the measurement-unit-specific and operating-variable-dependent correction instruction, any systematic errors of the measurement unit that depend on one or more operating variables of the system can be corrected or "calculated out." The resulting measurement accuracy can thus be increased. Alternatively, the use of less accurate measurement units can be considered if the measurement-unit-specific correction allows already specified accuracy limits to be met even with the less accurate measurement units; this can reduce costs.

[0008] It is also advantageously possible to form dependent measured values, for example total values, using the corrected measured values, and to do so with an accuracy that is sufficient for many applications due to the correction carried out according to the invention, but would not be sufficient without the correction and would require the use of better or more precise measuring units or additional measuring units (e.g. B. Total current sensors) would be necessary.

[0009] The measuring unit(s) are preferably analog measuring units that generate analog output signals, such as analog measuring sensors or analog measuring transducers.

[0010] According to the invention, the measuring unit-specific correction instruction is determined on the basis of at least one error curve or set of error curves measured for the respective measuring unit, which quantify an error caused by the measuring unit in the output signal - preferably over the entire working or measuring range of the measuring unit - as a function of one or more operating variables of the system.

[0011] By correcting using the correction instruction, the error of the measuring unit is preferably compensated or at least reduced.

[0012] The correction instruction contains a function or family of functions that is inverse or complementary to the measured error curve or family of error curves or is formed by at least one such inverse or complementary function or family of functions.

[0013] The function can be a one-dimensional function in the case of a dependence on only one operating variable and a two- or multi-dimensional function in the case of a dependence on two or more operating variables.

[0014] The error curve is preferably determined using a reference measuring instrument that has a better accuracy class than the measuring unit for which the correction instruction is to be determined.

[0015] In a variant considered advantageous, the measuring unit(s), or at least one of the measuring units, is an analog current transformer that detects a current to be measured and outputs a smaller, preferably proportional, current as an output signal. If the current to be measured is sinusoidal, the smaller current is preferably also sinusoidal and, barring any converter errors, in phase with the current to be measured.

[0016] Another variant considered advantageous provides that the measuring unit(s), or at least one of the measuring units, is an analog current sensor that detects a current to be measured and outputs a voltage, preferably a voltage proportional to the current, as an output signal. If the current to be measured is sinusoidal, the voltage is preferably also sinusoidal and, barring sensor errors, in phase with the current to be measured.

[0017] In yet another variant considered advantageous, the measuring unit(s), or at least one of the measuring units, is an analog voltage sensor that detects a voltage to be measured and outputs a smaller voltage as an output signal, preferably a voltage proportional to the voltage to be measured. If the voltage to be measured is sinusoidal, the smaller voltage is preferably also sinusoidal and, barring sensor errors, in phase with the voltage to be measured.

[0018] The measuring device is thus preferably designed to process an analog output signal of an analog measuring unit and generates the measured value with the analog output signal.

[0019] The arrangement forms a protection or measuring device for connection to an analog measuring unit of a high-voltage system (voltage from 50 kV), a medium-voltage system (voltage between 1 kV and 50 kV), or a low-voltage system (voltage between 100 V and 1 kV), or preferably also includes such a protection or measuring device. In this case, the corrected measured value describes an electrical operating state of the high-voltage, medium-voltage, or low-voltage system.

[0020] The measuring unit is preferably a current transformer which comprises a coil, in particular an iron-free or iron-containing coil, and generates an analog current signal as an analog output signal.

[0021] It is also advantageous if the measuring unit is a voltage converter which comprises a transformer, a capacitive voltage divider and / or an ohmic voltage divider and generates an analog voltage signal as an analog output signal.

[0022] The correction instruction assigned to each measuring unit is preferably stored in a memory of the arrangement.

[0023] With regard to the input of the correction instruction, it is considered advantageous if the arrangement comprises an input device that accepts the input of the correction instruction as such or at least the input of one or more correction parameters with which the correction instruction can be formed. The correction parameters can, for example, be correction factors for a plurality of reference current or reference current-voltage values; the correction device can then perform an interpolation for current or voltage values lying between the reference current or reference voltage values in order to determine the correction factors actually to be applied.

[0024] The input device preferably comprises a manual device for manually entering correction instructions and / or correction parameters. Alternatively or additionally, a scanning device is preferably provided, which enables the entire correction instruction or at least one or more correction parameters to be read in, with which the correction instruction can be formed—for example, by the aforementioned interpolation or by determining a correction function based on the correction parameters.

[0025] The scanning device is preferably suitable for reading QR codes containing the correction instruction or at least one or more correction parameters. The QR codes are preferably also applied to at least the measuring units connected to the measuring device.

[0026] The correction instruction or at least one or more correction parameters and / or the corresponding QR code are preferably provided on a sensor nameplate and a routine test report. The QR code can be read using a suitable reader, e.g., a smartphone, and made available to a configuration tool of the measuring device / protection device via a suitable app. The configuration tool itself can perform a semi-automatic assignment to the correct parameters for the respective phase in the device.

[0027] The correction instruction assigned to the individual measuring unit preferably provides for the correction of the measured value generated by the measuring device, taking into account the magnitude, the effective value and / or the phase of the respective measured value generated by the measuring device.

[0028] The correction instruction assigned to the individual measuring unit preferably also provides for the correction of the measured value of the measuring device taking into account at least one environmental parameter, in particular the respective ambient temperature of the measuring unit.

[0029] In a first particularly preferred embodiment, it is provided that the output signal is an analog voltage signal, the measured value generated by the measuring device is a voltage measured value, in particular a corrected amplitude or effective value, and the corrected measured value is a corrected voltage measured value, in particular a corrected amplitude or effective value, which the correction unit forms according to Uk = f Um where Uk denotes the corrected voltage measurement value and Um denotes the voltage measurement value generated by the measuring device and f(Um) is a function which is at least also dependent on the voltage measurement value Um generated by the measuring device.

[0030] It is considered advantageous if: Uk = Um X + 1 C 1 where X is a value or function dependent on an operating variable of the system, for example the voltage measurement value generated by the measuring device, and C1 is a constant, preferably measuring unit-specific correction value, for example according to the standard IEC61869-11.

[0031] It is considered particularly advantageous if: X = a 1 Um and thus Uk = Um a 1 Um + 1 C 1 where a1 is a unit-specific constant.

[0032] It is also advantageous if the temperature T of the system is taken into account, preferably according to: Uk = Um X + 1 C 1 ⋅ K 1 T where K1(T) is a correction factor depending on the temperature T.

[0033] In a second particularly preferred embodiment, it is provided that the output signal is an analog voltage signal, the measured value generated by the measuring device is a phase measured value and the corrected measured value is a corrected phase measured value which the correction unit forms according to φuk = f U , φm where φuk denotes the corrected phase measurement value and φum denotes the phase measurement value generated by the measuring device and f(U) is a function which is at least also dependent on the level of the analog voltage signal, in particular the amplitude or effective value of the analog voltage signal.

[0034] It is considered advantageous if: φuk = φum + a 2 ⋅ K 2 T U + φ 1 where a2 is a measurement unit-specific constant, K2(T) is a temperature-dependent correction factor, U is an amplitude or effective value of the analog voltage signal and φ1 is a constant, preferably measurement unit-specific phase correction value, for example according to the IEC61869-11 standard.

[0035] In a third particularly preferred embodiment, it is provided that the output signal is an analog current signal, the measured value generated by the measuring device is a current measured value and the corrected measured value is a corrected current measured value which the correction unit forms according to Ik = f Im where Ik denotes the corrected current measurement value and Im the current measurement value generated by the measuring device and f(Im) is a function which is at least also dependent on the current measurement value Im generated by the measuring device.

[0036] It is considered advantageous if: Ik = Im X + 1 C 3 where X is a function dependent on an operating variable of the system, for example the current measurement value Im generated by the measuring device, and C3 is a constant, preferably measuring unit-specific correction value, for example according to the standard IEC61869-11.

[0037] It is considered particularly advantageous if: X = a 3 Im ⋅ In and thus Ik = Im a 3 Im ⋅ In + 1 C 3 where a3 is a measuring unit-specific constant and In is the rated current of the measuring unit.

[0038] It is also advantageous if the temperature T of the system is taken into account, preferably according to: Ik = Im a 3 Im ⋅ In + 1 C ⋅ K 2 T where K2(T) is a temperature-dependent correction factor.

[0039] In a fourth particularly preferred embodiment, it is provided that the output signal is an analog current signal, the measured value generated by the measuring device is a phase measured value and the corrected measured value is a corrected phase measured value which the correction unit forms according to φik = f I , φim where φik denotes the corrected phase measurement value and φim denotes the phase measurement value generated by the measuring device and f(I) is a function which is at least also dependent on the level of the analog current signal, in particular the amplitude or effective value of the analog current signal.

[0040] It is considered advantageous if: φik = φim + a 4 Im ⋅ In + φ 4 where a4 is a measuring unit-specific constant, In is the rated current of the measuring unit and φ4 is a constant phase correction value, for example according to the IEC61869-11 standard.

[0041] With regard to the advantages of the method according to the invention and with regard to advantageous embodiments of the method according to the invention, reference is made to the above statements in connection with the arrangement according to the invention and its advantageous embodiments.

[0042] The invention is explained in more detail below using exemplary embodiments; by way of example, Fig. 1-12 example error curves of measuring units as well as correction instructions in the form of correction functions for measured value correction and Fig. 13-16 embodiments of arrangements for arrangements according to the invention.

[0043] In the figures, the same reference symbols are always used for identical or comparable components.

[0044] Measuring units such as transducers or measuring sensors have a specific error curve for amplitude and phase position, which fluctuates within the scope of manufacturing tolerances but is generally very stable for each individual sensor.

[0045] The Figure 1 shows an example of a typical error curve for the phase error Fφ of the phase angle φ (error depending on the current level I) of a current sensor with a primary rated current of 300A Class 1 ext. 200%, including the permissible accuracy limits, which are marked with the reference symbols GGR(1). The error curves vary depending on the sensor type / supplier and must be adjusted accordingly in the application using modified / different correction formulas.

[0046] It is recommended to use predefined formulas in measuring devices, allowing the necessary variables (factors / power and offset values) to be individually configured. To this end, the factors / power and offset values used in the formulas could be individually determined during the manufacturing process and added to the routine test report, so that they can then be entered into the measuring device during commissioning.

[0047] Alternatively, various correction curves can be predefined and selected during commissioning (comparable to inverse time overcurrent curves). The additional effort required to enter a few parameters into the measuring device during commissioning is minimal compared to the costs for higher-quality transformers / sensors, separate systems for protection and measurement, their installation, and operation. This is complemented by a reduction in the number of different current sensors available to switchgear manufacturers and sensor manufacturers.

[0048] The determination of possible functions can be done, for example, using a spreadsheet program (e.g., Excel). Here, the respective value of the correction function is preferably subtracted from the original measured value (for phase correction) or multiplied by the original measured value (for amplitude correction) to obtain an improved result. 1. Ways to correct the phase error:

[0049] The Figure 2 shows a typical course of the phase angle error Fφ over the operating current range for current transformers used in medium and high voltage systems. Figure 2 shows the curve for low currents I in more detail.

[0050] A significant increase in the phase error Fφ is clearly visible at lower currents. The phase deviation is relatively constant in the middle / upper measuring range. The deviation from the zero value can be used as a constant phase correction value in the protection / measuring device. Thus, the sensor can already achieve an accuracy of class 0.5 with a correction value of -33'; see accuracy limits GGR(0.5) for class 0.5 in Figure 3 .

[0051] For the next accuracy class 0.5S, the use of a constant correction value is no longer sufficient (see accuracy limits GGR(0.5S) for class 0.5S in Figure 4 ), since the error does not increase linearly with decreasing operating currents, but rather disproportionately. Therefore, the correction value has almost no effect here.

[0052] Therefore, dynamic correction of the deviation should preferably be performed as a function of the operating current, so that deviations of varying magnitudes can also be corrected. Depending on the complexity and the performance of the measuring system, a mathematical (even non-linear) equation can be found that corrects the original measured value. This equation can also be used only for a partial measuring range (in the above example, 0-150 A), since in the higher current range, the error approaches zero due to a constant correction value.

[0053] If the CPU performance of the measuring system is lower, a linear equation can be applied, which also achieves an improvement.

[0054] The correction function can and should ideally represent the mathematical description of the error curve or be identical with it, as for example the Figure 5 shows; in Figure 5The correction function "FCO1" is almost identical to the error curve Fφ. In the measuring device, the current-dependent offset (i.e., the corresponding value of the correction function "FCO1") is then subtracted from the measured phase position, depending on the operating current. The result is the adjusted, corrected phase position Fφ' with a phase error approaching 0' (see Figure 5 ). In the Figure 5 In addition to the function FCO1, the phase error Fφ and the operating current-dependent adjusted or corrected phase error Fφ', the accuracy limits GGR(0.1) for class 0.1 ext 200 are shown.

[0055] The corresponding correction function FCO1 for the correction according to Figure 5 is based on a (subtractive) dynamic correction value cdyn(i), which is subtracted from the measured phase value for correction and is preferably calculated according to: cdyn i = 200 i + 0 , 015 ⋅ i − 15 ′ − φ 0 cor where cdyn(i) denotes the dynamic correction value to be subtracted from the measured phase value, i denotes the operating current, -15' denotes a constant part of the correction, and φ0cor denotes the standard correction value according to IEC 61869-10. The constant part of -15'-φ0cor can also be combined into a single parameter.

[0056] With this correction, resulting accuracies can be achieved that reach the highest accuracy class 0.1 ext 200.

[0057] Alternatively or additionally, the inverse of the current level can be used to determine the correction function, such as the Figure 6 with the correction function FCO2. The resulting corrected phase error Fφ' and the accuracy limits GGR(0.2) for class 0.2 ext 200 are shown in the Figure 6 also marked.

[0058] The corresponding correction function FCO2 for the correction according to Figure 6is based on a (subtractive) dynamic correction value cdyn(i), which is subtracted from the measured phase value for correction and is preferably calculated according to: cdyn i = 300 / i − φ 0 cor

[0059] Even a simplified linear correction can lead to an improvement in the lower measuring range, as exemplified by the Figure 7 Here, however, the influence should only be up to a defined current threshold (visible at the bend area of the lines in Figure 7 ); for higher current values, only the standard correction value is preferably used. Figure 7 shows an example of a corresponding correction function FCO3. The resulting adjusted or corrected phase error Fφ' and the accuracy limits GGR(0.5S) for class 0.5S are shown in the Figure 7 also marked.

[0060] The corresponding correction function FCO3 for the correction according to Figure 7is based on a (subtractive) dynamic correction value cdyn(i), which is subtracted from the measured phase value for correction and is preferably calculated according to: cdyn i = 5.5 ⋅ i − 120 ′ − φ 0 cor

[0061] The correction function FCO3 is preferably used for operating currents <25A, for larger currents the following applies: cdyn i = − φ 0 cor 2. Ways to correct the amplitude error:

[0062] In Figure 8 A significant increase in the amplitude error FA is evident at lower currents I; the saturation of transformers / sensors is not considered here. The amplitude deviation is relatively constant in the middle / upper measuring range. Only with the onset of the sensor's saturation range does the error increase rapidly again. The deviation from the zero value can be used as a constant amplitude correction value in the protection / measuring device. Thus, the sensor can already achieve an accuracy of class 0.2 ext 200 with a correction value of 0.998. This shows the Figure 9, in which the uncorrected amplitude error FA and the corrected amplitude error FA' are plotted.

[0063] Here, too, a dynamic correction of the deviation can be performed depending on the operating current, so that deviations of varying magnitudes can be corrected. Depending on the effort and the performance of the measuring system, a mathematical (even non-linear) equation can be found that corrects the original measured value. This equation can also be used only for a partial measuring range (in this example, up to 200 A), since in the medium / higher current range the error approaches zero due to a constant correction value. If the measuring system has lower CPU performance, a linear equation can be applied, which also achieves an improvement.

[0064] Ideally, the correction function should also represent the mathematical description of the error curve for amplitude correction, or be identical to it. For amplitude correction, the respective measured value is preferably multiplied by a correction factor cdyn, in contrast to phase correction, where – as described above – a variable offset is preferably added / subtracted as the correction value cdyn.

[0065] With a current-dependent correction, a corrected amplitude error FA' can be achieved, as described in the Figure 10 is shown as an example. The Figure 10 is based on a correction by multiplying with a correction factor cdyn calculated according to: cdyn i = 3 ⋅ 10 − 9 ⋅ i 2.1 − 9 ⋅ 10 6 , 1 ⋅ i + 1 , 005

[0066] An amplitude correction factor (CFI) is not required separately here and is preferably included proportionally in the constant value of 1.0005. This allows for resulting accuracies that reach the highest accuracy class of 0.1 ext 200.

[0067] The Figure 11 shows, in a second example, a correction of the amplitude error by a logarithmic adjustment. With such an amplitude correction, a corrected amplitude error FA' can be achieved, as shown in Figure 11. Figure 11 is based on a correction by multiplying with a correction factor cdyn calculated according to: cdyn i = − 1 , 1 ⋅ 10 − 3 ⋅ ln i + 1 , 0045

[0068] The amplitude correction factor CFI is not required separately here and is preferably included proportionally in the constant value 1.0045.

[0069] The Figure 12shows, in a third example, a correction of the amplitude error by a linear adjustment in the lower measuring range. With such an amplitude correction, a corrected amplitude error FA' can be achieved, as shown in the Figure 12 is shown as an example. The Figure 12 is based on a correction by multiplying with a correction factor cdyn calculated according to: cdyn i = − 0.000015 ⋅ i + 1 , 00245

[0070] The linear correction is only suitable for an operating current of 0-250 A. For larger currents, only the standard correction factor CFI is applied; this is Figure 12 already taken into account. For switching the correction between linear and fixed starting at 250 A, a hysteresis of + / - 10 A should be considered to avoid constant switching.

[0071] The Figure 13shows an embodiment of a technical system 10 in which a measuring unit 20, for example in the form of a current transformer, is connected to a phase conductor L1 of a three-phase electrical power supply line. The measuring unit detects the current I1 in the phase conductor L1 and generates an analog current signal I1' as an output signal on the output side, which is smaller in magnitude than the current I1 in the phase conductor. The analog current signal I1' reaches a measuring device 30, which outputs a current measurement value Im1, which, for example, quantifies the magnitude or amplitude of the analog current signal I1' and thus at least indirectly the magnitude or amplitude of the current I1 in the phase conductor L1. A downstream correction unit 40 uses the current measurement value to form a corrected current measurement value Ik1 according to Ik 1 = f Im 1 = Im 1 X 1 + 1 C 3 where Ik1 denotes the corrected current measurement value and Im1 denotes the current measurement value generated by the measuring device 30. X1 is a function dependent on the current measurement value Im1, which is stored in the correction unit 40 and has been generated and stored for the measuring unit 20 based on previous calibration measurements.

[0072] It is considered particularly advantageous if: X 1 = a 3 Im 1 ⋅ In and thus Ik 1 = Im a 3 Im 1 ⋅ In + 1 C 3 where a3 is an individual constant, in this case determined individually for the measuring unit 20, In is the rated current of the measuring unit 20 and C3 is an individual constant, in this case determined for the measuring unit 20, for example according to the standard IEC61869-11.

[0073] In the variant described, a correction is made which depends on a single influencing variable, namely the respective current measured value Im1.

[0074] In addition, the temperature T of the system 10 can also be taken into account, preferably according to: Ik 1 = Im 1 a 3 Im 1 ⋅ In + 1 C 3 ⋅ K 20 T where K20(T) is a correction factor dependent on the temperature T, which describes the temperature-related error of the measuring unit 20.

[0075] In the latter variant, a correction is performed that depends on two influencing variables, namely the respective current measured value Im and the respective temperature T. The respective temperature T is preferably measured via a separate sensor that is connected to the correction unit 40 but is not shown further for reasons of clarity.

[0076] Similarly, for the other two phase conductors L2 and L3, additional measuring units 21 and 22, additional measuring devices 31 and 32, and additional correction units 41 and 42 can generate additional output signals I2', I3', additional measured values Im2 and Im3, and additional corrected measured values Ik2 and Ik3. A summator 50 can sum the corrected measured values Ik1, Ik2, and Ik3 and generate a total value Is, which quantifies a total current in the three-phase power supply line. A separate summation current transformer for measuring the summation current can thus be eliminated.

[0077] The Figure 14 shows an embodiment of a technical system 10, in which the measuring devices 30, 31 and 32 generate current-related phase measurement values φim1, φim2 and φim3 and the correction units 40, 41 and 42 form corrected phase measurement values φik1, φik2 and φik3. The correction unit 40 forms the corrected phase measurement value φik1 preferably according to φik 1 = f I 1 , φm 1 where f(I1) is a function dependent on the level of the analog current signal I1, in particular the amplitude or effective value of the analog current signal.

[0078] It is considered advantageous if: φik 1 = φim 1 + a 4 Im 1 ⋅ In + φ 4 where a4 is an individual constant, here related to the measuring unit 20, In is the rated current of the measuring unit 20 and φ4 is a constant, individual phase correction value, here related to the measuring unit 20, for example according to the standard IEC61869-11.

[0079] The Figure 15 shows an embodiment of a technical system 10 in which measuring units 20U, 21U and 22U form analog voltage signals U1', U2' and U3', which describe the conductor voltages on the phase conductors L1, L2 and L3 or are at least approximately proportional to them.

[0080] The measuring devices 30, 31 and 32 generate voltage-related phase measurement values φum1, φum2 and φum3 based on the line voltages of the phase conductors L1, L2 and L3, and the correction units 40, 41 and 42 form corrected voltage-related phase measurement values φuk1, φuk2 and φuk3.

[0081] The correction unit 40 forms the corrected phase measurement value φuk1 preferably according to φuk 1 = f U 1 , φm 1 where φu1k denotes the corrected voltage-related phase measurement value and φum1 denotes the phase measurement value generated by the measuring device 30 and f(U1) is a function which is at least also dependent on the level of the analog voltage signal U1', in particular the amplitude or effective value of the analog voltage signal U1'.

[0082] It is considered advantageous if: φuk 1 = φum 1 + a 2 + K 2 T U + φ 1 where a2 is a constant determined individually for the measuring unit 20U, K2(T) is a temperature-dependent correction factor individual for the measuring unit 20U, U is an amplitude or effective value of the analog voltage signal U1', and φ1 is a constant phase correction value determined individually for the measuring unit 20U, for example according to the standard IEC61869-11.

[0083] The Figure 16 shows an embodiment of a technical system 10 in which measuring units 20U, 21U and 22U form analog voltage signals U1', U2' and U3', which describe the conductor voltages on the phase conductors L1, L2 and L3 or are at least approximately proportional to them.

[0084] The measuring devices 30, 31 and 32 generate voltage-related amplitude measured values Um1, Um2 and Um3 for the conductor voltages of the phase conductors L1, L2 and L3 and the correction units 40, 41 and 42 form corrected voltage-related amplitude measured values Uk1, Uk2 and Uk3.

[0085] The correction unit 40 forms the corrected amplitude measurement value Uk1 preferably according to Uk 1 = f Um 1 where Uk1 denotes the corrected voltage measurement value and Um1 denotes the voltage measurement value generated by the measuring device 30 and f(Um) is a function which is at least also dependent on the voltage measurement value Um1 generated by the measuring device 30.

[0086] It is considered advantageous if: Uk 1 = Um 1 X 1 + 1 C 1 where X1 is a function which is dependent on an operating variable of the system 10, for example the voltage measurement value Um1 generated by the measuring device 30, and which is individually determined for the measuring unit 20, and C1 is a constant correction value which is individually determined for the measuring unit 20, for example in accordance with the standard IEC61869-11.

[0087] It is considered particularly advantageous if: X 1 = a 1 Um 1 and thus Uk 1 = Um 1 a 1 Um 1 + 1 C 1 where a1 is a constant determined individually for the measuring unit U20.

[0088] In the variant described, a correction is made that depends on a single influencing variable, namely the respective voltage measurement value Um.

[0089] In addition, the temperature T of the system 10 can also be taken into account, preferably according to: Uk 1 = Um 1 X 1 + 1 C 1 ⋅ K 1 T where K1(T) is a temperature-dependent correction factor determined individually for the measuring unit U20.

[0090] In the latter variant, a correction is performed that depends on two influencing variables, namely the respective voltage measurement value Um1 and the respective temperature T. The respective temperature T is preferably measured via a separate sensor that is connected to the correction unit 40 but is not shown further for reasons of clarity.

[0091] The Figures 13 to 16The measuring devices 30, 31 and 32 shown and the correction units are preferably integrated in a protection or measuring device which serves to protect and / or monitor the power supply line or the three phase conductors L1, L2 and L3 of the technical installation 10.

[0092] The above in connection with the Figures 1 to 16 The variants described may have one, several or all of the properties summarized below: Cost savings through the use of transformers / sensors with a lower accuracy class than would otherwise be necessary. Cost reduction (purchase, installation, maintenance) by eliminating the need for a summation current transformer for measurement; the summation current can only be calculated from phase current values. Cost savings through the use of measuring units for multiple functions (protection and measurement) in a single device, made possible by the improved quality of the measured values due to the correction. Reduced transformer / sensor diversity, thus lower inventory requirements, easier retrofitting of measuring functions in existing systems. Mathematical representation and recording of typical error curves for the amplitude and phase position of current and voltage measured values. Based on the error curves, a compensation curve / line is calculated, which is used to post-process the measured values in real time. Instead of a "correction formula," corrections could also be used for individually defined values, such asCurrent values can be entered as correction parameters, for example, manually or by scanning. The correction parameters can then be interpolated within the measuring device itself between the defined entered correction parameters to generate intermediate values.

[0093] Although the invention has been illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. List of reference symbols

[0094] 10 technical system 20 measuring unit 20 U measuring unit 21 measuring unit 21 U measuring unit 22 measuring unit 22 U measuring unit 30 measuring device 31 measuring device 32 measuring device 40 correction unit 41 correction unit 42 correction unit 50 summing unit FAAmplitude error FA'corrected amplitude error I1Current I2Current I3Current I1'Current signal / output signal I2'Current signal / output signal I3'Current signal / output signal Ik1Corrected current measured value Ik2Corrected current measured value Ik3Corrected current measured value Im1Current measured value Im2Current measured value Im3Current measured value IsTotal value L1Phase conductor L2Phase conductor L3Phase conductor TTemperature U1'Voltage signal / output signal U2'Voltage signal / output signal U3'Voltage signal / output signal Uk1Corrected voltage-related amplitude measured value Uk2Corrected voltage-related amplitude measured value Uk3Corrected voltage-related amplitude measured value Um1Voltage-related amplitude measured value Um2Voltage-related amplitude measured value Um3Voltage-related amplitude measured value φik1Corrected current-related phase measurement value φik2 corrected current-related phase measurement value φik1 corrected current-related phase measurement value φim1 current-related phase measurement value φim2 current-related phase measurement valueφim3 current-related phase measurement value φuk1 corrected voltage-related phase measurement value φuk2 corrected voltage-related phase measurement value φuk3 corrected voltage-related phase measurement value φum1 voltage-related phase measurement value φum2 voltage-related phase measurement value φum3 voltage-related phase measurement value

Claims

1. Arrangement comprising a measuring device (30, 31, 32) which is suitable for measuring an output signal (I1', I2', I3', U1', U2', U3'), delivered by a measuring unit (20, 21, 22, 20U, 21U, 22U), that describes an operating variable of a technical installation (10) and for producing a measured value (Im1, Im2, Im3, φim1, φim2, φim3, Um1, Um2, Um3, φum1, φum2, φum3), - wherein the arrangement forms a protection or measuring device for connection to an analogue measuring unit (20, 21, 22, 20U, 21U, 22U) of a high-voltage, medium-voltage or low-voltage system or at least also includes such a protection or measuring device, - wherein the arrangement comprises a correction unit (40, 41, 42) which is configured to correct the measured value produced by the measuring device (30, 31, 32) in accordance with a correction instruction associated with each individual measuring unit and to produce a corrected measured value (Ik1, Ik2, Ik3, φik1, φik2, φik3, Uk1, Uk2, Uk3, φuk1, φuk2, φuk3), wherein the corrected measured value describes an electrical state of the high-voltage, medium-voltage or low-voltage system, - wherein the correction instruction specific to the measuring units depends on the measured value produced by the measuring device (30, 31, 32), - and wherein the correction instruction specific to the measuring units has been determined on the basis of an error curve or a family of error curves, measured for the measuring unit (20, 21, 22, 20U, 21U, 22U), that quantifies an error produced by the measuring unit (20, 21, 22, 20U, 21U, 22U) in the output signal (I1', I2', I3', U1', U2', U3') according to operating variables, and - correction of the measured value produced by the measuring device (30, 31, 32) by means of the correction instruction compensates for or at least reduces the error produced by the measuring unit (20, 21, 22, 20U, 21U, 22U), characterized in that - the correction instruction contains a function or family of functions that is inverse or complementary with respect to the measured error curve or family of error curves, or said correction function is formed by such an inverse or complementary function or family of functions, the correction instruction also depending on the level of another operating variable of the technical installation (10).

2. Arrangement according to one of the preceding claims, characterized in that the measuring unit (20, 21, 22) is a current transformer which includes a coil, in particular an ironless or iron-core coil, and produces an analogue current signal as analogue output signal (I1', I2', I3').

3. Arrangement according to either of the preceding claims, characterized in that the measuring unit (20U, 21U, 22U) is a voltage transformer which includes a transformer, a capacitive voltage divider and / or a resistive voltage divider and produces an analogue voltage signal as analogue output signal (U1', U2', U3').

4. Arrangement according to one of the preceding claims, characterized in that the arrangement comprises an input device which inputs the correction instruction or at least inputs one or more correction parameters that can be used to form the correction instruction.

5. Arrangement according to Claim 4, characterized in that the input device includes a scanning device which reads in the correction instruction or at least reads in one or more correction parameters that can be used to form the correction instruction.

6. Arrangement according to one of the preceding claims, characterized in that the correction instruction associated with each individual measuring unit provides for correction of the measured value produced by the measuring device (30, 31, 32) in consideration of the absolute value, the root mean square value and / or the phase of the respective measured value produced by the measuring device (30, 31, 32).

7. Arrangement according to one of the preceding claims, characterized in that the output signal (U1', U2', U3') is an analogue voltage signal, the measured value produced by the measuring device (30, 31, 32) is a voltage measured value, in particular a corrected amplitude value or root mean square value, and the corrected measured value is a corrected voltage measured value, in particular a corrected amplitude value or root mean square value, that the correction unit (40, 41, 42) forms in accordance with Uk = f Um where Uk denotes the corrected voltage measured value and Um denotes the voltage measured value produced by the measuring device (30, 31, 32) and f(Um) is a function that is at least also dependent on the voltage measured value produced by the measuring device (30, 31, 32).

8. Arrangement according to one of the preceding claims, characterized in that the output signal (U1', U2', U3') is an analogue voltage signal, the measured value produced by the measuring device (30, 31, 32) is a phase measured value and the corrected measured value is a corrected phase measured value that the correction unit (40, 41, 42) forms in accordance with φk = f U , φm where φk denotes the corrected phase measured value and φm denotes the phase measured value produced by the measuring device (30, 31, 32) and f(U) is a function that is at least also dependent on the level of the analogue voltage signal, in particular the amplitude value or root mean square value of the analogue voltage signal.

9. Arrangement according to one of the preceding claims, characterized in that the output signal (I1', I2', I3') is an analogue current signal, the measured value produced by the measuring device (30, 31, 32) is a current measured value and the corrected measured value is a corrected current measured value that the correction unit (40, 41, 42) forms in accordance with Ik = f Im where Ik denotes the corrected current measured value and Im denotes the current measured value produced by the measuring device (30, 31, 32) and f(Im) is a function that is at least also dependent on the current measured value produced by the measuring device (30, 31, 32).

10. Arrangement according to one of the preceding claims, characterized in that the output signal (I1', I2', I3') is an analogue current signal, the measured value produced by the measuring device (30, 31, 32) is a phase measured value and the corrected measured value is a corrected phase measured value that the correction unit (40, 41, 42) forms in accordance with φk = f I , φm where φk denotes the corrected phase measured value and φm denotes the phase measured value produced by the measuring device (30, 31, 32) and f(I) is a function that is at least also dependent on the level of the analogue current signal, in particular the amplitude value or root mean square value of the analogue current signal.

11. Arrangement according to one of the preceding claims, characterized in that the correction instruction associated with each individual measuring unit provides for correction of the measured value of the measuring device (30, 31, 32) in consideration of an environmental parameter, in particular the respective ambient temperature of the measuring unit (20, 21, 22, 20U, 21U, 22U).

12. Method for operating an arrangement comprising a measuring device (30, 31, 32) that measures an output signal (I1', I2', I3', U1', U2', U3'), delivered by a measuring unit (20, 21, 22, 20U, 21U, 22U), that describes an operating variable of a technical installation (10), and produces a measured value, - wherein the arrangement forms a protection or measuring device for connection to an analogue measuring unit (20, 21, 22, 20U, 21U, 22U) of a high-voltage, medium-voltage or low-voltage system or at least also includes such a protection or measuring device, - and wherein the measured value produced by the measuring device (30, 31, 32) is corrected in accordance with a correction instruction associated with each individual measuring unit and a corrected measured value is produced, the measure of correction in accordance with the correction instruction specific to the measuring units depending on the measured value produced by the measuring device (30, 31, 32), wherein the corrected measured value describes an electrical state of the high-voltage, medium-voltage or low-voltage system, - and wherein the correction instruction specific to the measuring units has been determined on the basis of an error curve or a family of error curves, measured for the measuring unit (20, 21, 22, 20U, 21U, 22U), that quantifies an error produced by the measuring unit (20, 21, 22, 20U, 21U, 22U) in the output signal (I1', I2', I3', U1', U2', U3') according to operating variables, and - correction of the measured value produced by the measuring device (30, 31, 32) by means of the correction instruction compensates for or at least reduces the error produced by the measuring unit (20, 21, 22, 20U, 21U, 22U), characterized in that - the correction instruction contains a function or family of functions that is inverse or complementary with respect to the measured error curve or family of error curves, or said correction function is formed by such an inverse or complementary function or family of functions, the correction instruction also depending on the level of another operating variable of the technical installation (10).