CN103760402B - Voltage compensating method is affected based on the threephase potential transformer of D_dot principle and three-phase - Google Patents

Abstract

The invention provides a kind of threephase potential transformer based on D_dot principle and three-phase affects voltage compensating method, wherein threephase potential transformer comprises ring electrode I, ring electrode II, insulating support and direct earth capacitance, insulating support comprises semicircle bracket I, semicircle bracket I I and sway brace, sway brace is arranged on semicircle bracket I, on the sidewall of semicircle bracket I I, and semicircle bracket I, semicircle bracket I I arranges the through hole formed for passing for measured conductor with one heart, ring electrode I, ring electrode II is arranged with one heart, and be embedded in semicircle bracket I and semicircle bracket I I respectively, ring electrode I, ring electrode II by wire and direct earth capacitance and connect, it is little that threephase potential transformer of the present invention has volume, structure is simple, the features such as good insulation preformance and measurement safety, three-phase of the present invention affects voltage compensating method and makes analysis to influencing each other when measuring between three-phase line, the measured value close to truth is obtained with this.

Description

Three-phase voltage transformer based on D _ dot principle and three-phase influence voltage compensation method

Technical Field

The invention relates to the technical field of power equipment, in particular to a three-phase voltage transformer based on a D _ dot principle and a three-phase influence voltage compensation method.

Background

A conventional voltage transformer includes: electromagnetic voltage transformers, capacitive voltage transformers, electronic sensors, and the like. The electromagnetic voltage transformer has the problems of high insulation difficulty, easy generation of ferromagnetic resonance and the like, the capacitor voltage transformer is poor in transient response characteristic due to the fact that the capacitor voltage transformer is provided with a plurality of energy storage elements, a damping device needs to be additionally arranged on a secondary circuit to improve the transient response characteristic, and the electronic sensor has the problems of large measurement error and the like.

Therefore, the voltage sensor based on the D _ dot principle (called as D _ dot sensor for short) adopts the charge induction principle to realize measurement instead of energy transmission, so that non-contact measurement can be realized, when the voltage sensor is applied to a transformer substation with a high voltage level, the secondary side hardly outputs any current, the secondary side safety detection is realized, meanwhile, the primary side is not influenced, and the threat of ferromagnetic resonance generated by the sensor is avoided because the whole sensor does not have inductive devices.

Specifically, the voltage sensor based on the D _ dot principle adopts the charge induction principle and measures the grounding connected with the measuring electrodeThe output voltage at the resistor is matched to measure the electric displacement vector near the conductor in proportion to the integral quantity of the output voltage, so as to obtain the time domain waveform of the conductor voltageA voltage sensor of the principle.

However, the existing D _ dot sensor structure generally has the problems of complex structure, insulation property to be improved, and the like.

Disclosure of Invention

In view of the above, the invention provides a three-phase voltage transformer based on the D _ dot principle and a three-phase influence voltage compensation method, wherein the three-phase voltage transformer has the characteristics of small volume, simple structure, good insulation performance, safe measurement and the like, and the three-phase influence voltage compensation method analyzes the mutual influence among three-phase lines during measurement so as to obtain a measured value close to a real situation.

The invention provides a three-phase voltage transformer based on a D _ dot principle, which comprises: annular electrode I, annular electrode II, insulating support, ground capacitance, insulating support includes: the device comprises a semicircular support I, a semicircular support II and a supporting arm, wherein the supporting arm is arranged on the side walls of the semicircular support I and the semicircular support II, the semicircular support I and the semicircular support II are concentrically arranged to form a through hole for a tested conductor to pass through, the annular electrode I and the annular electrode II are concentrically arranged and are respectively embedded in the semicircular support I and the semicircular support II, the annular electrode I and the annular electrode II are connected in series with the ground capacitor and the ground through wires, and the oscilloscope is connected in parallel with the ground capacitor.

Further, the annular electrode I and the annular electrode II are metal aluminum rings with the same shape.

Further, the inner diameter of the annular electrode I and the annular electrode II is between 60 and 70mm, and the outer diameter of the annular electrode I and the annular electrode II is between 70 and 80 mm.

Further, still include: the setting is in be used for adjusting on the support arm semicircle support II's adjust knob, fastening screw's elasticity degree is adjustable, and when the screw was loose, semicircle support II can reciprocate, screws the screw when reaching suitable position.

Further, the adjustment distance between the semicircular brackets I, II ranges from 0 to 50 mm.

The invention also provides a three-phase influence voltage compensation method based on the D _ dot principle, which comprises the following steps of:

one phase voltage V of three-phase voltage₁The three-phase voltage transformer based on the D _ dot principle is connected;

measuring the voltage V at two ends of the grounding capacitor of the three-phase voltage transformer by adopting an oscilloscope_out；

The formula is adopted:

${\stackrel{\·}{V}}_{\mathrm{out}}=\stackrel{\·}{Z}*\left[\begin{array}{cccc}1& 1& 1& 1\end{array}\right]*{\left[\begin{array}{cccc}{\stackrel{\·}{Z}}_a& 0& 0& -{\stackrel{\·}{Z}}_d\\ {\stackrel{\·}{Z}}_a+r& -{\stackrel{\·}{Z}}_b-r& -r& r\\ \stackrel{\·}{Z}& \stackrel{\·}{Z}+r& {\stackrel{\·}{Z}}_c+\stackrel{\·}{Z}+r& \stackrel{\·}{Z}\\ -\stackrel{\·}{Z}-r& -\stackrel{\·}{Z}& -\stackrel{\·}{Z}& -{\stackrel{\·}{Z}}_d-\stackrel{\·}{Z}-r\end{array}\right]}^{-1}*\left\{\begin{array}{c}{\stackrel{\·}{V}}_1\\ 0\\ 0\\ 0\end{array}\right\}$

calculating V₁;

Wherein,andare respectively a capacitor C₁₄And C₁₅，Is C₂₅And C₃₅The value of the parallel connection is,is C₂₄And C₃₄R is the resistance on the coaxial wire connecting the electrodes,is C_m,C_p,R₀,R_p,C₀A composite parameter of composition wherein C_ijCapacitance representing the i-wire and the j-electrode, C_mTo ground capacitance, R_PAnd C_PRespectively a resistance, a capacitance, R introduced for a measuring probe introduced when the oscilloscope is connected_oAnd C₀Respectively a resistor and a capacitor which are introduced by the access oscilloscope.

The invention has the beneficial effects that:

the three-phase voltage transformer based on the D _ dot principle mainly comprises a small number of components such as an annular electrode, an insulating support and a grounding capacitor, has the characteristics of small volume, simple structure and the like, particularly can reduce the highest electric field intensity by the annular electrode so as to achieve the purpose of improving the insulation level, has good dynamic range and transient characteristics, and simultaneously ensures the measurement safety.

Meanwhile, the invention analyzes the mutual influence among the three-phase lines during measurement, thereby providing a compensation method, correcting the measurement result of the oscilloscope to obtain a measurement value close to the real condition, and being capable of more accurately reflecting the voltage waveform change condition on the cable.

Drawings

The invention is further described below with reference to the following figures and examples:

FIG. 1 is a schematic diagram of the D _ dot sensor principle.

Fig. 2 is a schematic structural diagram of a three-phase voltage transformer based on the D _ dot principle.

Fig. 3 is a detection diagram of a three-phase voltage transformer based on the D _ dot principle.

FIG. 4 is a diagram of the D _ dot sensor measurement equivalent circuit without considering the influence of the neighbors.

FIG. 5 is a diagram of the D _ dot sensor measurement equivalent circuit when the influence of the neighbors is taken into account.

FIG. 6 is a diagram of an equivalent circuit of a D _ dot sensor measurement for a certain phase taking into account the influence of neighboring phases.

FIG. 7 is a diagram of a test apparatus.

The specific implementation mode is as follows:

as shown in FIG. 1, it is a schematic diagram of a D _ dot sensor, which is the simplest D _ dot sensor formed by enclosing a metal conductor 1 having high conductivity in an insulator 2, whereinTo measure the electric field strength of the point, a closed gaussian surface 4 is made on the surface of the metal conductor, and the gaussian surface is used to obtain:

(equation 1).

In the formula (1), q is the induced charge in the closed Gaussian surface 4, namely on the metal conductor 1, A_eqIs equivalent of a sensorThe area, which is related to the shape structure of the metal conductor 1 in the sensor and the angle of the gaussian surface with the vector direction of the electric field strength.

When the metal conductor 1 is connected with the grounding matching resistor R through the cable 3, the charges in the metal conductor 1 move to form currentAnd produces a voltage drop across the ground matching resistor R:

$V_0={\mathrm{\ϵ}}_0{A}_{\mathrm{eq}}R\frac{d}{\mathrm{dt}}\stackrel{\→}{E}$ (equation 2).

Thus, the D _ dot sensor output V₀Electric field intensity with the point to be measuredThe derivative with respect to time is linear, so the D _ dot sensor can be used for electric field measurement.

Because the measurement of the D _ dot sensor is to detect the measured voltage through charge coupling, which is different from a CVT (capacitor voltage transformer) that realizes measurement through energy transfer, it can realize contactless measurement, so when it is applied in a transformer substation with high voltage level, it can make the secondary side have almost no current output, and when the secondary side safety detection is realized, it is ensured that the primary side is not affected, and because the whole sensor has no inductive device, the threat of ferromagnetic resonance generated by the sensor is avoided.

As shown in fig. 2 and 3, the three-phase voltage transformer based on the D _ dot principle provided by the present invention includes: ring electrode I1, ring electrode II2, insulating support and grounded capacitor 4.

Wherein, insulating support includes: semicircular bracket I31, semicircular bracket II32 and support arm 33, support arm 33 set up on the lateral wall of semicircular bracket I31 and semicircular bracket II32, and semicircular bracket I31, semicircular bracket II32 set up the through-hole that forms to be used for supplying to be surveyed conductor 6 to pass with one heart, and the size of this through-hole is between 12 to 16 mm.

Wherein, an adjusting knob for adjusting the position of the semicircular bracket II is arranged on the supporting arm 33, and the adjusting distance range between the semicircular brackets I, II is between 0 and 50 mm. Specifically, adjust knob can be fastening screw, and its elasticity degree is adjustable, and when the screw pine, semicircle support II can reciprocate, screws the screw when reaching suitable position.

The ring electrode I1 and the ring electrode II2 are concentrically arranged and are respectively embedded in the semicircular bracket I31 and the semicircular bracket II32, and the ring electrode I1 and the ring electrode II2 are connected with the grounding capacitor 4 and the ground in series through leads (such as coaxial leads).

Wherein, the ring electrode I1 and the ring electrode II2 are metal aluminum rings with the same shape.

Wherein the inner diameters of the ring electrode I1 and the ring electrode II2 are between 60 and 70mm, and the outer diameters are between 70 and 80 mm.

In FIG. 3, an insulating ring made of insulating material is arranged between the ring electrodes I1 and II2 and the conductor 6 for clamping and fixing the conductor 6 (for example, a copper bar), and in addition, A in FIG. 3_eqIs the voltage on the wire.

In addition, during measurement, as shown in fig. 3, an oscilloscope 5 is connected in parallel with the grounding capacitor 4, so that the voltage output by the three-phase voltage transformer can be measured.

The embodiment mainly comprises a few components such as an annular electrode, an insulating support and a grounding capacitor, has the characteristics of small volume, simple structure and the like, particularly can reduce the highest electric field intensity of the annular electrode so as to achieve the purpose of improving the insulating level, has good dynamic range and transient characteristics, and simultaneously ensures the measurement safety.

The voltage output from the two ends of the grounding capacitor 4 in the figure 3 is connected into an oscilloscope, and the output voltage waveform can be observed. Meanwhile, as can be seen from fig. 3, the output voltage of the upper electrode of the voltage transformer can be represented as:

$V_{\mathrm{out}}=\frac{C_1}{C_1+C_2}{V}_{\mathrm{pow}}$ (formula 3)

Wherein C is₁Is the capacitance between the upper and lower electrodes (i.e. electrode I, electrode II) shown in FIG. 3, C₂The output terminal capacitance (i.e., the ground capacitance) shown in fig. 3.

The invention analyzes the mutual influence among three-phase lines during measurement, thereby providing a compensation method, which corrects the measurement result of an oscilloscope, obtains a measurement value close to the real condition and more accurately reflects the voltage waveform change condition on a cable.

The specific process is as follows:

if the influence of the measuring device such as the resistor and the oscilloscope on the coaxial conductor is considered, the output voltage U can be obtained_o(s)：

$U_o\left(s\right)=\frac{Z_2\left(s\right)}{Z_1\left(s\right)+Z_2\left(s\right)}{U}_i\left(s\right)=\frac{\frac{Z_{\mathrm{sc}}}{1+Z_{\mathrm{sc}}{C}_{m}s}}{\frac{s^2{R}_1{R}_2{C}_1{C}_2+s(R_1{C}_1+R_2{C}_2)+1}{s^2{C}_1{C}_2(R_1+R_2)+s(C_1+C_2)}}{U}_i\left(s\right)$

Namely: $U_o\left(s\right)=Z_{\mathrm{sc}}\·\frac{s^2{C}_1{C}_2(R_1+R_2)+s(C_1+C_2)}{(1+Z_{\mathrm{sc}}{C}_{m}s)(s^2{R}_1{R}_2{C}_1{C}_2+s(R_1{C}_1+R_2{C}_2)+1)}{U}_i\left(s\right)$ (formula 4)

As shown in FIG. 4, wherein C₁、C₂A capacitor formed by upper and lower semicircular metal rings and a lead wire, R₁、R₂Resistance on coaxial conductors for connecting upper and lower semi-circular metal rings, C_mIs the capacitance between the voltage transformer and ground, and is also the measuring capacitance for measuring the output voltage, Z_scFor measuring the equivalent impedance of the oscilloscope, it is compared with C_mAnd are used in parallel for measurement.

If the influence of the other two phases on the three-phase line on the voltage transformer is considered, a measurement circuit diagram 5 can be obtained.

A, B, C cable lines are numbered 1,2,3, the electrodes of each layer are numbered 4,5,6,7,8,9, respectively, V in the circuit₁、V₂、V₃Respectively the actual voltage on the cable of each phase, C_ijThe capacitance of the i cable and the j electrode is shown, for example: c₁₄Capacitance representing No. 1 cable and No. 4 electrode, C_mFor capacitive elements at the output voltage of the sensor measurement, R_PAnd C_PRespectively a resistance and a capacitance R introduced by a 10-time probe (a measuring probe which expands 10-time waveform is connected when the oscilloscope is connected)_oAnd C₀And the mutual capacitance between the adjacent phase line and the electrode of the sensor on the phase is considered and analyzed, and the measurement result of the oscilloscope is corrected to compensate and obtain a voltage waveform close to the real condition.

Mutual capacitance of each electrode and each conductor in the circuit is an inherent parameter, the mutual capacitance can be obtained by performing finite element analysis and solving on an electric field, and oscilloscope parameters of a measuring device are known, so that the measuring result of the voltage transformer can be finally corrected, and the result is close to the real condition by compensating the measured value.

In the experiment, a model is constructed by using electromagnetic field analysis software, mutual capacitance between each electrode and a conductor is solved, and an equivalent circuit of the model is shown in fig. 5.

If A phase line is taken (corresponding voltage is V)₁) For analysis (let B, C be 0 for two-phase input voltage source), the equivalent circuit shown in fig. 6 has the following relationship:

$\left[\begin{array}{cccc}{\stackrel{\·}{Z}}_a& 0& 0& -{\stackrel{\·}{Z}}_d\\ {\stackrel{\·}{Z}}_a+r& -{\stackrel{\·}{Z}}_b-r& -r& r\\ \stackrel{\·}{Z}& \stackrel{\·}{Z}+r& {\stackrel{\·}{Z}}_c+\stackrel{\·}{Z}+r& \stackrel{\·}{Z}\\ -\stackrel{\·}{Z}-r& -\stackrel{\·}{Z}& -\stackrel{\·}{Z}& -{\stackrel{\·}{Z}}_d-\stackrel{\·}{Z}-r\end{array}\right]\left\{\begin{array}{c}{\stackrel{\·}{I}}_1\\ {\stackrel{\·}{I}}_2\\ {\stackrel{\·}{I}}_3\\ -{\stackrel{\·}{I}}_4\end{array}\right\}=\left\{\begin{array}{c}{\stackrel{\·}{V}}_1\\ 0\\ 0\\ 0\end{array}\right\}$ (formula 5)

$V_{\mathrm{out}}=Z^{\·}({I^{\·}}_1+{I^{\·}}_2+{I^{\·}}_3-{I^{\·}}_4)$ (formula 6)

Namely:

$\begin{array}{c}{\stackrel{\·}{V}}_{\mathrm{out}}=\left[\begin{array}{cccc}\stackrel{\·}{Z}& \stackrel{\·}{Z}& \stackrel{\·}{Z}& \stackrel{\·}{Z}\end{array}\right]*\left[\begin{array}{c}{\stackrel{\·}{I}}_1\\ {\stackrel{\·}{I}}_2\\ {\stackrel{\·}{I}}_3\\ {-\stackrel{\·}{I}}_4\end{array}\right]\\ =\stackrel{\·}{Z}*\left[\begin{array}{cccc}1& 1& 1& 1\end{array}\right]*{\left[\begin{array}{cccc}{\stackrel{\·}{Z}}_a& 0& 0& -{\stackrel{\·}{Z}}_d\\ {\stackrel{\·}{Z}}_a+r& -{\stackrel{\·}{Z}}_b-r& -r& r\\ \stackrel{\·}{Z}& \stackrel{\·}{Z}+r& {\stackrel{\·}{Z}}_c+\stackrel{\·}{Z}+r& \stackrel{\·}{Z}\\ -\stackrel{\·}{Z}-r& -\stackrel{\·}{Z}& -\stackrel{\·}{Z}& -{\stackrel{\·}{Z}}_d-\stackrel{\·}{Z}-r\end{array}\right]}^{-1}*\left\{\begin{array}{c}{\stackrel{\·}{V}}_1\\ 0\\ 0\\ 0\end{array}\right\}\end{array}$

(formula 7)

In the formulaAndrespectively, the capacitor C in FIG. 5₁₄And C₁₅，Is C₂₅And C₃₅The value of the parallel connection is,is C₂₄And C₃₄The parallel capacitance of (a) is,is C_m,C_p,R₀,R_p,C₀The formed composite parameter.

From this it can be seen that V_outAnd V₁There is a fixed relationship, which can be expressed in the form of a transfer function, withr is related, if these parameters are known, V is known₁And V_outThe relationship (2) of (c).

For simplifying the equation, if the three-phase line is symmetrical in positionIn the order diagramThen

$\begin{array}{c}{\stackrel{\·}{V}}_{\mathrm{out}}=\stackrel{\·}{Z}*\left[\begin{array}{cccc}1& 1& 1& 1\end{array}\right]*{\left[\begin{array}{cccc}{\stackrel{\·}{Z}}_a& 0& 0& -{\stackrel{\·}{Z}}_c\\ {\stackrel{\·}{Z}}_a+r& -{\stackrel{\·}{Z}}_a-r& -r& r\\ \stackrel{\·}{Z}& \stackrel{\·}{Z}+r& {\stackrel{\·}{Z}}_c+\stackrel{\·}{Z}+r& \stackrel{\·}{Z}\\ -\stackrel{\·}{Z}-r& -\stackrel{\·}{Z}& -\stackrel{\·}{Z}& -{\stackrel{\·}{Z}}_c-\stackrel{\·}{Z}-r\end{array}\right]}^{-1}\\ ={\stackrel{\·}{V}}_1\·\frac{1}{(\frac{{\stackrel{\·}{Z}}_a}{{\stackrel{\·}{Z}}_c}+1)(\frac{r}{2\stackrel{\·}{Z}}+1)}\end{array}*\left\{\begin{array}{c}{\stackrel{\·}{V}}_1\\ 0\\ 0\\ 0\end{array}\right\}$

(formula 8)

From the above analysis, the invention provides a three-phase influence voltage compensation method based on the D _ dot principle, which comprises the following steps:

step 1, one phase voltage V of three-phase voltage is used₁And the three-phase voltage transformer based on the D _ dot principle is connected.

Step 2, measuring the voltage V at two ends of the grounding capacitor of the three-phase voltage transformer by adopting an oscilloscope_out。

Step 3, calculating V by adopting a formula (7) or (8)₁I.e. the voltage of the measured phase.

The following example illustrates this process:

as shown in fig. 7, the test apparatus is composed of three voltage sensors mounted on a three-phase electric wire and a ground and overhead line lightning arrester. Wherein, the distance between the three horizontally arranged wires and the ground is 10 meters, the voltage amplitude on the cable conductor is about 5.78KV, the frequency is 50Hz, and each phase is A, B and C from left to right.

In simulation test, an X1000 high-voltage probe is used for measuring voltage values and phases on a three-phase line, and a measurement result V₁As shown in table 1.

Table one:

through multiple times of simulation and test, the capacitance C formed by the wire and the electrodes (including the comprehensive parameters of the electrode I, the electrode II and the capacitance of the three wires, which can be obtained through the Thevenin theorem) is obtained₁₀Capacitance C obtained by withstand voltage test of sensor manufacturer_1M(i.e., the ground capacitance) satisfies the following relationship:

C_1M=0.17C₁₀(formula 8)

At this time, the output voltage of the three-phase voltage transformer is displayed on an oscilloscope as follows:

table two:

v by equation 7₁And V_outCalculating the voltage V on the electrode₁The voltage value and phase offset of' is as follows:

table three:

comparing the data obtained in Table one with Table three, the sensor output V is calculated according to the above method_outCorresponding V₁', and the actual value V₁Compared with the prior art, the voltage value has small difference with the phase offset, and the measurement precision of the sensor is improved. Therefore, the change condition of the voltage waveform on the cable line can be accurately reflected.

According to the invention, by improving the structure of the D _ dot sensor and considering the influence of analyzing the adjacent electric field on the three-phase line and the measuring device on the measuring circuit, a compensation method is provided, the measuring result of the oscilloscope is corrected, so that a numerical value close to the real situation is obtained, the follow-up voltage change and fault diagnosis in the relay protection system are facilitated, the on-line monitoring and the capture of the high-frequency overvoltage waveform are facilitated, and the method has great significance for the voltage measurement of the power grid.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims (5)

1. The utility model provides a three-phase voltage transformer based on D _ dot principle which characterized in that: the method comprises the following steps: annular electrode I, annular electrode II, insulating support and ground connection capacitance, insulating support includes: the device comprises a semicircular support I, a semicircular support II and a support arm, wherein the support arm is arranged on the side wall of the semicircular support I and the side wall of the semicircular support II, the semicircular support I and the semicircular support II are concentrically arranged to form a through hole for a tested conductor to pass through, the annular electrode I and the annular electrode II are concentrically arranged and are respectively embedded in the semicircular support I and the semicircular support II, and the annular electrode I and the annular electrode II are connected with the grounding capacitor and the ground in series through a lead;

further comprising: and the adjusting knob is arranged on the supporting arm and is used for adjusting the position of the semicircular bracket II.

2. A three-phase voltage transformer based on the D _ dot principle according to claim 1, characterized in that: the annular electrode I and the annular electrode II are metal aluminum rings with the same shape.

3. A three-phase voltage transformer based on the D _ dot principle according to claim 2, characterized in that: the inner diameters of the annular electrode I and the annular electrode II are between 60 and 70mm, and the outer diameters of the annular electrode I and the annular electrode II are between 70 and 80 mm.

4. A three-phase voltage transformer based on the D _ dot principle according to claim 1, characterized in that: the adjustment distance between the semi-circular brackets I, II ranges between 0 and 50 mm.

5. A three-phase influence voltage compensation method based on a D _ dot principle is characterized by comprising the following steps: the method comprises the following steps:

one phase voltage V of three-phase voltage₁Accessing a three-phase voltage transformer based on the D _ dot principle according to any one of claims 1 to 4;

measuring the voltage V at two ends of the grounding capacitor of the three-phase voltage transformer by adopting an oscilloscope_out；

The formula is adopted:

${\stackrel{\·}{V}}_{out}=\stackrel{\·}{Z}*\left[\begin{array}{cccc}1& 1& 1& 1\end{array}\right]*{\left[\begin{array}{cccc}{\stackrel{\·}{Z}}_a& 0& 0& -{\stackrel{\·}{Z}}_d\\ {\stackrel{\·}{Z}}_a+r& -{\stackrel{\·}{Z}}_b-r& -r& r\\ \stackrel{\·}{Z}& \stackrel{\·}{Z}+r& {\stackrel{\·}{Z}}_c+\stackrel{\·}{Z}+r& \stackrel{\·}{Z}\\ -\stackrel{\·}{Z}-r& -\stackrel{\·}{Z}& -\stackrel{\·}{Z}& -{\stackrel{\·}{Z}}_d-\stackrel{\·}{Z}-r\end{array}\right]}^{-1}*\left\{\begin{array}{c}{\stackrel{\·}{V}}_1\\ 0\\ 0\\ 0\end{array}\right\}$

calculating V₁；

Wherein,andare respectively a capacitor C₁₄And C₁₅，Is C₂₅And C₃₅The value of the parallel connection is,is C₂₄And C₃₄R is the resistance on the coaxial wire connecting the electrodes,is C_m,C_p,R₀,R_p,C₀A composite parameter of composition wherein C_ijCapacitance representing i-wire and j-electrode，C_mTo ground capacitance, R_PAnd C_PRespectively a resistance, a capacitance, R introduced for a measuring probe introduced when the oscilloscope is connected_oAnd C₀Respectively a resistor and a capacitor which are introduced by the access oscilloscope.