CN101535818A - Method and arrangement for measuring the voltage on a conductor - Google Patents

Abstract

The invention relates, inter alia, to a method for measuring the voltage (UE) on a conductor (30) by means of a measuring arrangement (10) having a capacitive divider (20) coupled to the conductor and a measuring device (70), wherein, in the method, the voltage (UA) at the low-voltage terminal (U20) of the capacitive divider, the high-voltage terminal (020) of which is connected to the conductor, is measured with the formation of a low-voltage measurement value (UA1, UA2) and a measurement value (ik) indicating the voltage on the conductor is formed with the low-voltage measurement value, wherein in order to form the measurement value, the measured low-voltage measurement value is corrected by means of a correction element (110) having an inverse transfer function (Gcorr) with respect to the transfer function (G) of the measurement arrangement. The invention provides for determining a time constant (Tl) of the transfer function of the measurement arrangement on the basis of the voltage at the low-voltage terminal for two different load states (Zl, Z2) at the low-voltage terminal, and for determining the inverse transfer function taking account of said time constant.

Description

Method and device for measuring voltage on a conductor

technical field

The invention relates to a method according to the features of the preamble of claim 1 .

Background technique

Particularly in medium-voltage technology, very cheap capacitive splitters which can be used as so-called primary transformers compared to inductive voltage transformers can be realized by using bushing capacitors or ring electrodes in the support insulators. compressor. Such capacitive voltage dividers are currently used, for example, for voltage testing. Due to the high tolerances of the capacitances, however, measurement errors of up to 25% must be taken into account in the case of capacitive voltage dividers, if no suitable measured value correction is carried out. This form of transformer is generally unsuitable for voltage measurements if not corrected, since the measurement error typically must be less than 5% for measurement applications.

In order for capacitive voltage dividers to also be used for measuring tasks, voltage divider compensation or measured value correction is required. A measuring method with a capacitive voltage divider and suitable measured value correction is disclosed in German Patent Application Laid-Open DE 10346356 A1. In this known method, the voltage on the line is measured by means of a measuring device having a capacitive voltage divider coupled to the line and a measuring device. The voltage is first measured at the low voltage terminal of a capacitive voltage divider whose high voltage terminal is connected to said lead to form a low voltage measurement. The measured low-pressure measured value is corrected with a correction unit having an inverse transfer function of the transfer function of the measuring device. Taking into account the corrected low-voltage measured value, a measured value indicating the voltage on the line is then formed.

Contents of the invention

The technical problem to be solved by the invention is to further develop a method of the described kind in such a way that it can be carried out particularly simply.

According to the invention, the above-mentioned technical problem is solved by a method according to the characterizing parts of claim 1 . Preferred embodiments of the method according to the invention are given in the dependent claims.

According to the invention, for two different load states at the low-voltage terminal, the time constant of the transfer function of the measuring device is determined using the voltage at the low-voltage terminal, and taking this time constant into account, the inverse transfer function is determined.

The main advantage of the method according to the invention is that in this method phase angle compensation or phase angle correction can be carried out without additional measurement of the primary voltage actually applied across the capacitive voltage divider, so that even during operation of the measuring device The phase angle compensation can be carried out very simply and, in particular, also arbitrarily repeatable during operation of the measuring device. In this way, for example, the phase angle correction determined by the inverse transfer function can be monitored regularly or continuously and adapted to new conditions in the event of possible drift phenomena in the measuring device.

With this method, for example, the voltage on a phase line of a power line can be measured.

)；也就是该工作方式使得可以在形成测量值时使用所述低压值、时间常数和幅值分压比，由此可以根据幅值和相位进行测量值校正。Preferably, the amplitude voltage divider ratio of the capacitive voltage divider (

); that is, this mode of operation makes it possible to use the low-pressure value, the time constant and the amplitude divider ratio when forming the measured value, so that the measured value can be corrected as a function of the amplitude and phase.

The divided voltage value is preferably determined by measuring the voltage at the high-voltage terminal to form a high-voltage measured value and using the ratio between the high-voltage measured value and the low-voltage measured value as the divided voltage value. The determination of the partial pressure value can be performed, for example, once and determined when the measuring device is installed.

By using a first-order high-pass filter as the inverse transfer function, a phase angle correction can be performed particularly simply and thus advantageously.

Preferably, the inverse transfer function is formed according to the following formula with the determined time constant:

${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; Korr</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T\; K\; T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span><figure-callout\; id="1"\; label="T\; K\; T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}{{}_{}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}$

Here, T1 denotes a determined time constant, Tk denotes a further freely selectable time constant and K denotes a conversion factor of the measuring device.

Preferably, the freely selectable time constant is selected such that it corresponds to the time constant at the current input of the measuring device. In this way, the time constant of the measuring device can also be included in the phase angle correction.

For example, one of two electrical load states can be formed by the internal resistance of a measuring device used to measure the voltage on the low voltage terminals.

The other of the two electrical load states can be formed, for example, by connecting an additional electrical component in addition to the internal resistance of the measuring device. An additional resistor or an additional voltage source is preferably connected as an additional electrical component. Additional electrical components can preferably be electrically connected in series or in parallel with the internal resistance of the measuring device.

With regard to the simple and cost-effective construction of the measuring device when using an additional resistor, it is preferred to connect the additional resistor between the low-voltage terminal and the internal resistance.

The time constant T1 of the transfer function of the measuring device is determined simply and thus advantageously, for example according to the following formula:

表示对于两种不同的电气负载状态在低压端子上的电压的相位的相位差。Among them, R _K1 represents the internal resistance of the measuring device, R _K2 represents the sum of the internal resistance of the measuring device and the resistance of the connected resistor,

Indicates the phase difference of the phases of the voltages on the low voltage terminals for two different electrical load states.

Furthermore, the invention relates to a measuring device for measuring voltage on a conductor, having a capacitive voltage divider whose high-voltage terminal is connected to the conductor, and a measuring device for measuring to form a low-voltage measurement and use this low-voltage measurement to form a measurement of the voltage on the conductor, wherein the measured low-voltage measurement is corrected with an inverse transfer function of the transfer function of the measuring device to form the measurement unit correction.

Such a measuring device is likewise disclosed in German patent application publication DE 10346356 A1.

The technical problem underlying the invention with respect to such a measuring device is to expand the measuring device so that a particularly simple correction of the measured values is possible.

According to the present invention, this technical problem is solved as follows: the measuring device is constructed in such a way that it is suitable for measuring the time constant of the transfer function of the measuring device for two different load states on the low-voltage terminal by means of the voltage on the low-voltage terminal, and considering such An inverse transfer function is formed subject to a defined time constant.

With regard to the advantages of the measuring device according to the invention and preferred embodiments of the measuring device according to the invention, see the above-mentioned embodiments regarding the method according to the invention.

The measuring device preferably has a switchable electrical component which, in the switched-on state, forms the other of the two electrical load states.

The measuring device is preferably designed with an evaluation device for switching the load state and for forming an inverse transfer function.

The switchable electrical components can, for example, form part of the measuring device and be controlled by the evaluating device in order to switch the load state.

As an alternative, the additional electrical components can also form part of a separate calibration device connected to the measuring device and be controlled by the evaluation device in order to switch the load state.

The measuring device preferably has a voltage measuring device for measuring the voltage at the high-voltage terminal, so that the amplitude-dividing ratio of the capacitive voltage divider can also be determined while taking into account the low-voltage measured value. The voltage measured values of the voltage at the high-voltage terminals are preferably fed into an evaluation device for further processing.

Furthermore, the invention relates to a measuring device for a measuring device for measuring voltage on a conductor, wherein the measuring device is suitable for measuring the voltage at the low-voltage terminal of a capacitive voltage divider to form a low-voltage measurement and to use The low-voltage measured value forms a measured value which indicates the voltage on the line, wherein the measuring device corrects the measured low-voltage measured value with a correction unit having an inverse transfer function of the transfer function of the measuring device for forming the measured value.

Such a measuring device is likewise disclosed in German patent application publication DE 10346356 A1.

With respect to such a measuring device, the technical problem to be solved by the present invention is to further expand the measuring device so that a measured value correction can be carried out particularly simply.

According to the invention this technical problem is solved as follows: the measuring device is suitable for measuring the time constant of the transfer function of the measuring device for two different load states on the low-voltage terminal by means of the voltage on the low-voltage terminal, and taking into account the time constant determined in this way The inverse transfer function is formed under its own conditions.

For the advantages of the measuring device according to the invention and for preferred embodiments of the measuring device according to the invention, see the above-mentioned embodiments for the method according to the invention.

Furthermore, the invention relates to a calibration device for a measuring device. According to the invention, the calibrating device has control terminals for connection to a measuring device, the calibrating device has voltage measuring terminals suitable for connection to a capacitive voltage divider, the calibrating device has a control terminal connected to the voltage measuring terminals and is suitable for connecting to an external measuring device. The output terminal of the device, the switching element which is opened or closed according to the control signal on the control terminal is connected to the control terminal, and together with the switching element can be connected between the voltage terminal and the output terminal. Components are used to transition load states.

Description of drawings

The present invention will be further described below in conjunction with embodiment; Here, accompanying drawing is exemplary:

FIG. 1 shows a first embodiment of a measuring device according to the invention and an embodiment of a measuring device according to the invention and an embodiment of a calibration device according to the invention,

FIG. 2 shows an equivalent circuit diagram of a measuring device for a first switching state of the calibration device according to FIG. 1 ,

FIG. 3 shows an equivalent circuit diagram of a measuring device for a second switching state of the calibration device according to FIG. 1 ,

FIG. 4 shows an embodiment of a digital filter for an analysis device of the measuring device according to FIG. 1 ,

FIG. 5 shows a second embodiment of the measuring device according to the invention and an embodiment of the measuring device according to the invention and an embodiment of the calibration device according to the invention, and

FIG. 6 shows an equivalent circuit diagram of the switching states of the correction device according to FIG. 5 .

In FIGS. 1 to 6 , for the sake of clarity, the same reference numerals are used for identical or similar elements.

Detailed ways

A first exemplary embodiment of a measuring device 10 is shown in FIG. 1 . Measuring device 10 has a capacitive voltage divider 20 which is formed by a high-voltage capacitor C _o and a low-voltage capacitor C _U1 . One of the two terminals of the high voltage capacitor C _o forms the high voltage terminal O20 of the capacitive voltage divider 20 ; the other of the two terminals of the high voltage capacitor C _o forms the low voltage terminal U20 of the capacitive voltage divider 20 . The low-voltage terminal U20 of the capacitive voltage divider 20 is also connected to one terminal of the low-voltage capacitor C _U1 , the other terminal of the low-voltage capacitor C _U1 being grounded or connected to another potential, for example.

The high-voltage terminal O20 of the capacitive voltage divider 20 is connected to a phase conductor 30 of a power supply line, not further shown, so that the line voltage U _E on the phase conductor 30 can be measured.

The low voltage terminal U20 of the capacitive voltage divider 20 is connected to one end of a coaxial cable 40 which electrically forms a capacitor C _U2 ; this capacitor C _U2 is electrically connected in parallel with the low voltage capacitor C _U1 .

The calibration device 50 is connected to the other end of the coaxial cable 40 , specifically by means of its voltage measurement terminal M50 . An additional electrical component 60 is connected to the voltage measurement terminal M50 , wherein the electrical component 60 can be, for example, a resistor R _Z . Electrical component 60 is also connected to output terminal A50 of calibration device 50 .

In addition, switching element 65 of calibration device 50 can be seen in FIG. 1 , the switching terminal of which is connected to voltage measurement terminal M50 and output terminal A50 , and the control terminal of which is connected to control terminal S50 of calibration device 50 .

After the calibration device 50 there is a measuring device 70 which can be formed, for example, by a field device or a protective device. The measuring device 70 has a resistor R _K1 , after which an inductive transformer 80 , an A/D converter 90 and an evaluation device 100 are connected _. Evaluation device 100 can be formed, for example, by a programmable microprocessor device, in which one or more digital filters are implemented or can be implemented.

Measuring device 10 can be driven, for example, as follows:

The switching element 65 of the calibration device 50 is successively placed in the following switching states by the evaluation device 100:

switch status Switching element 65 Z1 closure Z2 disconnect

An equivalent circuit diagram is thus formed for the two switching states Z1 and Z2, as shown in FIGS. 2 and 3; FIG. An equivalent circuit diagram of a case where the switching element 65 is turned off. R _K2 represents the resistance sum of resistors R _Z and R _K1 according to the following formula

R _K2 ＝R _Z +R _K1 .

At this time, the voltages U _E and U _A in the analysis device 100 can be calculated according to the equivalent circuit diagram:

a) Switching state Z1 (switching element 65 closed):

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="E.\; u\; A"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">E.</figure-callout></span><figure-callout\; id="1"\; label="E.\; u\; A"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">\; </figure-callout>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$

b) Switching state Z2 (switching element 65 is off):

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="E.\; u\; A"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">E.</figure-callout></span><figure-callout\; id="2"\; label="E.\; u\; A"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">\; </figure-callout>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="T"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="T"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Wherein for the parameters V, T ₁ , T2 and C _U the following holds true:

$\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}}$

T ₁ ＝R _K1 ·(C _O +C _U )

T ₂ ＝R _K2 ·(C _O +C _U )

C _U ＝C _U1 +C _U2

Assuming that the input voltage _U remains constant during the compensation process, the following formula holds:

$\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="u\; A"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; id="2"\; label="u\; A"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="T"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}$

由下式计算：The sudden change in angle when the load resistance R _K1 and R _K2 is changed

Calculated by the following formula:

The following quadratic equation is obtained by deformation:

其中： $T_2=\frac{R_{K2}}{R_{K1}}\&CenterDot;T_1$

in: ${\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">T</figure-callout>}}_2=\frac{R_{K2}}{{\mathrm{<figure-callout\; id="1"\; label="R\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">R</figure-callout>}}_K}\&Center\; Dot;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout>}}_1$

From this, the following formula for calculating the desired time constant T1 results:

或者可以通过利用对于该解的估计值的或然性测试，或者可以通过对于另一对校准电阻R_K列出公式来进行。在两种情况下得出的解是正确的解。The apparent solution derived from this solution

Either by a probability test using an estimate for the solution, or by formulating a formula for another pair of calibration resistors R _K . The resulting solution is the correct one in both cases.

The amplitude divider ratio V of the capacitive voltage divider 20 together with the coaxial cable 40 can be determined by comparative measurements. For this purpose, the current voltage amplitude U _E on the phase conductor 30 is read out by a display device of an additional voltage measuring device present at least temporarily in the measuring device 10 and not shown in FIG. Reference values at additional measured value inputs of evaluation device 100 , which are not shown in the figure, are entered into evaluation device 100 manually, for example. This entry can be made once and for example when the measuring device is installed for the first time.

In order to correct the measured voltage values denoted by the reference symbol U _A1 for the switching state _Z1 in FIG. It is shown as an example in FIG. 4 . The function of the digital filter 110 is to correct the transfer function G of the measuring device 10 determined via the capacitive voltage divider 20, the coaxial cable 40, the calibration device 50 and the internal resistance R _K1 and to use the low-voltage measured values U _A1 and U _A2 A corrected measured value i(k) is formed at the output of the A/D converter 90 . For this purpose, an inverse correction transfer function G _korr with respect to the transfer function G to be corrected is used in the evaluation device 100 .

Since the inverse correction transfer function G _korr is represented by π-units with infinite amplification for frequency f=0, it is appropriate to arrange the inverse correction transfer function with an additional pole (Polstelle); in this way the offset problem ( Offset problem). The resulting corrected transfer function forms, for example, a first-order high-pass filter with another freely selectable characteristic time constant. This time constant is suitably set such that it corresponds to the characteristic time constant of current input M70 of measuring device 70 . The following equation shows the resulting corrected transfer function:

${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; Korr</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T\; K\; T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span><figure-callout\; id="1"\; label="T\; K\; T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}{{}_{}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}$

T _K stands for a freely selectable time constant and K stands for the conversion factor of the measuring device. K corresponds to the quotient of the voltage U _E on the phase line 30 and the voltage U _A at the low-voltage terminal U20 of the uncompensated capacitive voltage divider, and is thus ideally equal in value to the amplitude divider ratio V=C _O /(C _O +C _U ). If another element of the measuring device causes an amplification error, this is likewise corrected by the factor K; in this case K and V are no longer the same.

The corrected transfer function can be determined in the z-region using the bilinear transformation as follows:

${\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; T</span>}}\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; \&Right\; Arrow;</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{\mathrm{<span\; class="notranslate">\; the\; tan</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&pi;</span>}\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}$

The digital filter 110 thus has the following transfer function in the z region:

$\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; b</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}$

In order to calculate the correlation coefficient of the corrected transfer function, the following formula is obtained:

${\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span><figure-callout\; id="1"\; label="T\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}$

$b_0=\frac{\frac{T_1}{T_K}-k\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="T\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout>}}_K}{1+k\&CenterDot;T_K}$ in: $k=\frac{1}{T_K\&Center\; Dot;\mathrm{the\; tan}\left(\frac{1}{2\&CenterDot;T_K\&CenterDot;f_A}\right)}$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="b"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">b</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="T\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">T</figure-callout></span><figure-callout\; id="1"\; label="T\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}$

f _a here denotes the sampling frequency used.

FIG. 5 shows a second exemplary embodiment of a measuring device 10 in which a voltage source 200 is used as an additional electrical component 60 . FIG. 6 shows an equivalent circuit diagram formed.

The input voltage U _E can be calculated using the following formula:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}$

Assuming that the resistance R is known and that the voltage U _K takes two different known voltage values U _K1 and U _K2 in the two switching states Z1 and Z2 respectively, the following formulas can be listed for the two switching states Z1 and Z2:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; E.</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="u\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; id="1"\; label="u\; K"\; filenames="A200680056258E00153.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; j\&omega;R</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="u\; K"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">u</figure-callout></span><figure-callout\; id="2"\; label="u\; K"\; filenames="A200680056258E00141.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}$

It is assumed here that the input voltage U _E is constant for both switching states. The equations shown are solved using the same method as already discussed above in connection with FIGS. 1 to 4 , so that the inverse correction transfer function G _korr is determined in the evaluation device 100 and can be further used.

Claims (29)

1. A method for measuring a voltage (U _E ) on a lead (30) by means of a measuring device (10) having a capacitive voltage divider (20) coupled to said lead and a measuring device (70 ), where, in the method, - measuring the voltage (U A ) on the low voltage terminal (U20) of said capacitive voltage divider _, the high voltage terminal (O20) of which is connected to said conductor, to form a low voltage measurement (U _A1 , U _A2 ), and - using said low voltage measurement to form a measurement (ik) giving the voltage on said conductor, wherein - in order to form said measured value, the measured low pressure measured value is corrected by means of a correction unit (110) having an inverse transfer function (G _Korr ) with respect to the transfer function (G) of the measuring device, It is characterized in that, determining the time constant (T1) of the transfer function of the measuring device for two different load states (Z1, Z2) on the low-voltage terminal by means of the voltage on the low-voltage terminal, and - Determining said inverse transfer function taking this time constant into account. 2. The method as claimed in claim 1, characterized in that the voltage on a phase line of the transmission line is measured. 3. The method as claimed in claim 1, characterized in that a first-order high-pass filter is used as the inverse transfer function. 4. The method according to any one of the preceding claims, characterized in that the inverse transfer function is formed according to the following formula using the time constant: ${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; Korr</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}}}$ Here, T1 denotes the time constant, Tk denotes a further freely selectable time constant and K denotes the conversion factor of the measuring device. 5. The method as claimed in claim 4, characterized in that the freely selectable time constant is selected such that it corresponds to the time constant at the current input of the measuring device. 6. Method according to any one of the preceding claims, characterized in that one of the two electrical load states is formed by the internal resistance (R _K1 ) of a measuring device for measuring the voltage at the low-voltage terminals. 7. The method according to claim 6, characterized in that the other of the two electrical load states is formed by additionally connecting an additional electrical component (60) in addition to the internal resistance of the measuring device. 8. The method as claimed in claim 7, characterized in that an additional resistance (Rz) or an additional voltage (U _K ) is additionally connected as an additional electrical component. 9. A method according to claim 7 or 8, characterized in that the additional electrical component is electrically connected in series or in parallel with the internal resistance. 10. The method according to any one of claims 7-9, characterized in that the additional resistance is connected between the low voltage terminal and the internal resistance. 11. The method according to claim 10, characterized in that the time constant T1 of the transfer function of the measuring device is determined according to the following formula:

Wherein, R _K1 represents the internal resistance of the measuring device, R _K2 represents the sum of the internal resistance of the measuring device and the resistance of the connected resistor,

Indicates the phase difference of the phases of the voltages on the low voltage terminals for two different electrical load states. 12. The method according to any one of the preceding claims, characterized in that, - determining the amplitude divider ratio (V) of said capacitive voltage divider, and - taking into account said low pressure measurement, said time constant and said amplitude divider ratio (V) when forming said measurement. 13. A method according to claim 12, characterized by forming the high voltage measurement by measuring the voltage on the high voltage terminal and using the ratio between the high voltage measurement and the low voltage measurement as the amplitude divider ratio (V) , to determine the amplitude divider ratio (V). 14. A measuring device (10) for measuring voltage on a conductor (30), comprising: - a capacitive voltage divider (20), the high voltage terminal (O20) of which is connected to said wire, and - Measuring means (70) which measure the voltage on the low voltage terminal (U20) of said capacitive voltage divider to form a low voltage measurement (U _A1 , U _A2 ) and use this low voltage measurement to form a given wire The measured value (i(k)) of the voltage of , wherein, to form said measured value, the measured low voltage measured value is corrected with an inverse transfer function (G _Korr ) with respect to the transfer function (G) of the measuring device unit (110) correction, It is characterized in that, - determining the time constant (T1) of the transfer function of the measuring device for two different load states (Z1, Z2) on the low-voltage terminal by means of the voltage on the low-voltage terminal, and - Determination of the inverse transfer function taking into account the time constant determined in this way. 15. Measuring device according to claim 14, characterized in that one of two electrical load states is formed by the internal resistance of the measuring device. 16. Measuring device according to claim 15, characterized in that the measuring device has a switchable electrical component which, in the switched-on state, forms the other of the two electrical load states. 17. The measuring device as claimed in claim 1, characterized in that the measuring device has an evaluation device (100) for switching the load state and for forming the inverse transfer function. 18. The measuring device according to any one of claims 16 or 17, characterized in that the switchable electrical component forms an integral part of the measuring device and is controlled by the analyzing device in order to switch the load status. 19. The measuring device according to any one of claims 16 or 17, characterized in that additional electrical components form part of a separate calibrating device (50) connected to the measuring device and are determined by the analysis Device control to transition the load state. 20. Measuring device according to any one of claims 16 or 19, characterized in that the additional electrical component is formed by an additional resistor or an additional voltage source. 21. Measuring device according to any one of claims 16 or 20, characterized in that the additional electrical component can be electrically connected in series or in parallel with the internal resistance of the measuring device. 22. Measuring device according to any one of claims 16 or 21, characterized in that the switchable electrical component is formed by an additional resistor which can be connected between the low-voltage terminal and the internal resistor between. 23. The measuring device as claimed in claim 1, characterized in that the measuring device has a voltage measuring device for measuring the voltage at the high-voltage terminal. 24. A measuring device (70) for a measuring device for measuring voltage on a wire according to any one of claims 14-23, wherein the measuring device is adapted to measure a capacitive voltage divider to form a low-voltage measurement and to use said low-voltage measurement to form a measurement of the voltage on the conductor, wherein for forming said measurement said measuring device utilizes a The correction unit of the inverse transfer function of the transfer function corrects the measured low pressure measurement, It is characterized in that, The measuring device is suitable for determining the time constant of the transfer function of the measuring device for two different load states on the low-voltage terminal by means of the voltage at the low-voltage terminal and for determining the inverse transfer function. 25. The measuring device as claimed in claim 24, characterized in that the measuring device has an evaluation device for converting the load state and forming an inverse transfer function. 26. The measuring device according to any one of claims 24-25, characterized in that one of the two electrical load states is formed by the internal resistance of the measuring device. 27. The measuring device according to claim 26, characterized in that, - the measuring device has a switchable electrical component which, in the switched-on state, forms the other of the two electrical load states, and - the switchable electrical component is controlled by the analysis device to switch the load state. 28. The measuring device according to any one of claims 25-27, characterized in that, - the evaluation device has a control terminal for connection to a switchable electrical component which, in the switched-on state, forms the other of the two electrical load states, and - the switchable electrical component is controlled by the analysis device to switch the load state. 29. A calibration device (50) for a measuring device according to any one of claims 14-23, characterized in that - said calibration device has control terminals (S50) for connection to said measuring device, - said calibration device has a voltage measurement terminal (M50) suitable for connection to a capacitive voltage divider, - said calibration device has an output terminal (A50) connected to said voltage measurement terminal and adapted to be connected to an external measuring device, - a switching element (65) connected to said control terminal which is opened or closed according to a control signal at the control terminal, and A switchable electrical component (Rz) for switching the load state can be connected between the voltage terminal and the output terminal together with the switching element.

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