CN103760402A - Three-phase voltage transformer based on D_dot principle and three-phase influence voltage compensating method - Google Patents

Abstract

The invention provides a three-phase voltage transformer based on a D_dot principle and a three-phase influence voltage compensating method. The three-phase voltage transformer comprises an annular electrode I, an annular electrode II, an insulating support and a grounding capacitor. The insulating support comprises a semicircular support body I, a semicircular support body II and a supporting arm. The supporting arm is arranged on the side wall of the semicircular support body I and the side wall of the semicircular support body II, and the semicircular support body I and the semicircular support body II are concentrically arranged to form a through hole used for allowing a measured conductor to penetrate through. The annular electrode I and the annular electrode II are concentrically arranged and are embedded into the semicircular support body I and the semicircular support body II respectively. The annular electrode I and the annular electrode II are in series connection with the grounding capacitor and the ground through wires. The three-phase voltage transformer has the advantages of being small in size, simple in structure, good in insulating property, safe to measure and the like. The three-phase influence voltage compensating method analyzes the mutual influence among three phase lines in the measuring process, so that a measured value close to the real situation is obtained.

Description

Threephase potential transformer and three-phase based on D_dot principle affect voltage compensating method

Technical field

The present invention relates to electrical equipment technical field, relating in particular to a kind of threephase potential transformer and three-phase based on D_dot principle affects voltage compensating method.

Background technology

Traditional voltage transformer (VT) comprises: electromagnetic potential transformer, capacitance type potential transformer and electronic sensor, etc.Wherein electromagnetic potential transformer exists insulation difficulty to produce greatly and easily the problems such as ferroresonance, wherein capacitance type potential transformer is owing to being with many energy-storage travelling wave tubes, transient response characteristic is poor, need to install damping unit additional to improve transient response characteristic at secondary circuit, there is the problems such as measuring error is large in electronic sensor wherein.

Therefore, voltage sensor based on D_dot principle (is called for short: D_dot sensor) owing to adopting electric charge induction principle to realize, measure, but not energy transmission, therefore can realize noncontacting measurement, while being applied in the transformer station of voltage levels, can so that secondary side almost without any electric current, export, when realizing secondary side safety detection, assurance does not impact primary side, and because whole sensor does not exist inductive device, avoided the threat of the ferroresonance of sensor generation, etc.

Concrete, voltage sensor based on D_dot principle specifically adopts electric charge induction principle, by measuring the output voltage in the ground connection build-out resistor being connected with potential electrode, measure near the electric displacement vector conductor being directly proportional to this output voltage integration amount, thereby obtain the time domain waveform of conductor voltage, because its output voltage is directly proportional to electric displacement vector time differential, thus be called based on

the voltage sensor of principle.

But, current D_dot sensor construction ubiquity complex structure, the insulativity problem such as have much room for improvement.

Summary of the invention

In view of this, the invention provides a kind of threephase potential transformer and three-phase based on D_dot principle and affect voltage compensating method, wherein threephase potential transformer have that volume is little, simple in structure, the feature such as good insulation preformance and measurement safety, when wherein three-phase affects voltage compensating method to measurement, influencing each other between three-phase line made analysis, with this, obtains the measured value that approaches truth.

The invention provides a kind of threephase potential transformer based on D_dot principle, comprise: ring electrode I, ring electrode II, insulating support, direct earth capacitance, described insulating support comprises: semicircle bracket I, semicircle bracket I I and sway brace, described sway brace is arranged on described semicircle bracket I, on the sidewall of semicircle bracket I I, and described semicircle bracket I, semicircle bracket I I with one heart setting is formed for the through hole passing for measured conductor, described ring electrode I, ring electrode II arranges with one heart, and be embedded in respectively in described semicircle bracket I and semicircle bracket I I, described ring electrode I, ring electrode II by wire and described direct earth capacitance and connect, described oscillograph and described direct earth capacitance are in parallel.

Further, described ring electrode I, ring electrode II are the metallic aluminium ring that shape is identical.

Further, the internal diameter of described ring electrode I, ring electrode II is between 60 to 70mm, and external diameter is between 70 to 80mm.

Further, also comprise: be arranged on described sway brace for regulating the adjusting knob of described semicircle bracket I I, the tightness of trip bolt is adjustable, and in the time of screw pine, semicircle bracket I I can move up and down, and when reaching correct position, screw is screwed.

Further, the adjustable range scope between described semicircle bracket I, II is between 0 to 50mm.

The present invention also provides a kind of three-phase based on D_dot principle to affect voltage compensating method, comprises the steps:

By a wherein phase voltage V of three-phase voltage ₁access the threephase potential transformer based on D_dot principle as above;

The voltage V at the direct earth capacitance two ends of threephase potential transformer described in employing oscilloscope measurement _out;

Adopt formula:

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

Calculate V ₁;

Wherein,

with

be respectively capacitor C ₁₄and C ₁₅,

for C ₂₅with C ₃₅value in parallel,

for C ₂₄with C ₃₄shunt capacitance, the resistance on the concentric conductor that r is connecting electrode,

for C _m, C _p, R ₀, R _p, C ₀the comprehensive parameters forming, wherein C _ijthe electric capacity that represents i electric wire and j electrode, C _mfor direct earth capacitance, R _pand C _presistance, electric capacity that the measuring sonde of introducing while being respectively access oscillograph is introduced, R _oand C ₀be respectively resistance, electric capacity that access oscillograph is introduced.

Beneficial effect of the present invention:

Threephase potential transformer based on D_dot principle of the present invention mainly consists of a few parts such as ring electrode, insulating support and direct earth capacitancies, it has the characteristics such as volume is little, simple in structure, especially the electrode of annular can reduce maximum electric field intensity to reach the object that improves dielectric level, there is good dynamic range and transient state feature, guarantee to measure security simultaneously.

Meanwhile, the present invention's influencing each other between three-phase line when measuring performs an analysis, and proposes thus a kind of compensation method, and oscilloscope measurement result is revised, and obtains the measured value that approaches truth, can reflect comparatively exactly voltage waveform situation of change on cable.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described:

Fig. 1 is D_dot Fundamentals of Sensors schematic diagram.

Fig. 2 is the structural representation of the threephase potential transformer based on D_dot principle.

Fig. 3 is the detection sketch of the threephase potential transformer based on D_dot principle.

Fig. 4 does not consider adjacent D_dot sensor measurement equivalent circuit diagram while affecting mutually.

Fig. 5 considers adjacent D_dot sensor measurement equivalent circuit diagram while affecting mutually.

Fig. 6 considers adjacent a certain phase D_dot sensor measurement equivalent circuit diagram while affecting mutually.

Fig. 7 is test unit figure.

Embodiment:

As shown in Figure 1, be the principle schematic of D_dot sensor, it is enclosed the metallic conductor 1 with high conductivity in insulator 2 and forms the simplest D_dot sensor, wherein

for the electric field intensity of measured point, on metallic conductor surface, do a closed Gauss surface 4, and use Gauss theorem to obtain to it:

(formula 1).

Q is in closed Gauss surface 4 to be the induced charge on metallic conductor 1 in formula (1), A _eqfor the equivalent area of sensor, it is relevant with the shape and structure of metallic conductor in sensor 1 and the angle of Gauss surface and electric field vector direction.

After metallic conductor 1 is connected with ground connection build-out resistor R by cable 3, in metallic conductor 1, electric charge moves formation electric current

and on ground connection build-out resistor R, produce pressure drop:

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

Therefore, D_dot sensor output V ₀electric field intensity with measured point

derivative to the time is linear, so this D_dot sensor can be for electric field measurement.

Because the measurement of D_dot sensor is to be coupled and to be detected tested voltage by electric charge, itself and CVT (the Capacitor Voltage Transformer measuring by energy transmission realization, capacitance type potential transformer) difference, it can realize noncontacting measurement, therefore while being applied in the transformer station of voltage levels, can so that secondary side almost without any electric current, export, when realizing secondary side safety detection, assurance does not impact primary side, and because whole sensor does not exist inductive device, avoided the threat of the ferroresonance of sensor generation.

As shown in Figures 2 and 3, the threephase potential transformer based on D_dot principle provided by the invention comprises: ring electrode I1, ring electrode II2, insulating support and direct earth capacitance 4.

Wherein, insulating support comprises: semicircle bracket I 31, semicircle bracket I I32 and sway brace 33, sway brace 33 is arranged on the sidewall of semicircle bracket I 31 and semicircle bracket I I32, and semicircle bracket I 31, semicircle bracket I I32 with one heart setting are formed for the through hole passing for measured conductor 6, and the size of this through hole is between 12 to 16mm.

Wherein, on sway brace 33, be provided with for regulating the adjusting knob of semicircle bracket I I position, and the adjustable range scope between semicircle bracket I, II is between 0 to 50mm.Concrete, adjusting knob can be trip bolt, and its tightness is adjustable, and in the time of screw pine, semicircle bracket I I can move up and down, and when reaching correct position, screw is screwed.

Wherein, ring electrode I1, ring electrode II2 arrange with one heart, and are embedded in respectively in semicircle bracket I 31 and semicircle bracket I I32, ring electrode I1, ring electrode II2 by wire (for example: concentric conductor) with direct earth capacitance 4 with connect.

Wherein, ring electrode I1, ring electrode II2 are the metallic aluminium ring that shape is identical.

Wherein, the internal diameter of ring electrode I1, ring electrode II2 is between 60 to 70mm, and external diameter is between 70 to 80mm.

The dead ring of making for insulating material between ring electrode I1, II2 and conductor 6 in Fig. 3, for for example clamping tight and fixed conductor 6(: copper rod), the A in Fig. 3 in addition _eqfor voltage on electric wire.

In addition, during measurement, as shown in Figure 3, oscillograph 5 is in parallel with direct earth capacitance 4, can survey the voltage of threephase potential transformer output.

The present embodiment, mainly by a few parts such as ring electrode, insulating support and direct earth capacitancies, formed, it has the characteristics such as volume is little, simple in structure, especially the electrode of annular can reduce maximum electric field intensity to reach the object that improves dielectric level, there is good dynamic range and transient state feature, guarantee to measure security simultaneously.

By the voltage access oscillograph of the 4 two ends outputs of direct earth capacitance in Fig. 3, Observable output voltage waveforms.As shown in Figure 3, the output voltage of voltage transformer (VT) top electrode can be expressed as simultaneously:

$V_{\mathrm{out}}=\frac{C_1}{{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2}{V}_{\mathrm{pow}}$ (formula 3)

C wherein ₁for the electric capacity between upper and lower two electrodes shown in Fig. 3 (being electrode I, electrode II), C ₂for output capacitor shown in Fig. 3 (being direct earth capacitance).

The present invention's influencing each other between three-phase line when measuring performs an analysis, and proposes thus a kind of compensation method, and oscilloscope measurement result is revised, and obtains the measured value that approaches truth, reflects comparatively exactly voltage waveform situation of change on cable.

Idiographic flow is as follows:

If the impact of the measurement mechanism such as resistance, oscillograph, can obtain output voltage U on consideration concentric conductor _o(s):

$U_o\left(s\right)=\frac{Z_2\left(s\right)}{Z_1\left(s\right)+Z_2\left(s\right)}{U}_i\left(s\right)=\frac{\frac{{\mathrm{<figure-callout\; id="1"\; label="Z\; sc"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">Z</figure-callout>}}_{\mathrm{sc}}}{1+Z_{\mathrm{sc}}{C}_{m}s}}{\frac{s^2{R}_1{R}_2{C}_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_2+s(R_1{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+R_2{C}_2)+1}{s^2{C}_1{C}_2(R_1+R_2)+s({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2)}}{U}_i\left(s\right)$

That is: $U_o\left(s\right)=Z_{\mathrm{sc}}\&CenterDot;\frac{s^2{C}_1{C}_2(R_1+R_2)+s({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2)}{(1+Z_{\mathrm{sc}}{C}_{m}s)(s^2{R}_1{R}_2{C}_1{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_2+s(R_1{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000460243510000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+R_2{C}_2)+1)}{U}_i\left(s\right)$ (formula 4)

As Fig. 4, C wherein ₁, C ₂for the electric capacity of upper lower half circle becket and wire, R ₁, R ₂for connecting the resistance on the concentric conductor of upper lower half circle becket, C _mfor the electric capacity between voltage transformer (VT) and ground, be also for measuring the measurement electric capacity of output voltage, Z simultaneously _scfor measuring, use oscillographic equiva lent impedance, it and C _min parallel for measuring.

If consider again the impact of other two relative voltage transformer (VT) on three-phase line, can obtain metering circuit Fig. 5.

It is 1,2,3 that A, B, C cable are numbered, and each layer of electrode is numbered respectively 4,5,6,7,8,9, the V in circuit ₁, V ₂, V ₃be respectively the virtual voltage on each phase cable, C _ijthe electric capacity that represents i cable and j electrode, for example: C ₁₄the electric capacity that represents No. 1 cable and No. 4 electrodes, C _mfor the capacity cell on output voltage in sensor measurement, R _pand C _pbe respectively resistance, electric capacity that 10 times of probes (having connected the measuring sonde that expands 10 times of waveforms during access oscillograph) are introduced, R _oand C ₀be respectively resistance, electric capacity that access oscillograph is introduced, consider thus the mutual capacitance between the electrode of adjacent phase circuit and this phase upper sensor, and this is performed an analysis, by revising oscilloscope measurement result, can compensate, acquisition approaches the voltage waveform of truth.

In foregoing circuit, the mutual capacitance of each electrode and conductor is intrinsic parameter, can solve and obtain by electric field being carried out to finite element analysis, and measurement mechanism oscillograph parameter is known, therefore finally can revise the measurement result of voltage transformer (VT), and make result approach truth by compensation measurement.

In experiment, we utilize electromagnetic software to build model, solve the mutual capacitance between each electrode and conductor, and its equivalent electrical circuit as shown in Figure 5.

If (corresponding voltage is V to get A phase circuit ₁) analyze (making B, C two-phase input voltage source is 0), its equivalent electrical circuit, as accompanying drawing 6, will have following relation:

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

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

That is:

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

(formula 7)

In formula with

be respectively the capacitor C in Fig. 5 ₁₄and C ₁₅,

for C ₂₅with C ₃₅value in parallel,

for C ₂₄with C ₃₄shunt capacitance,

for C _m, C _p, R ₀, R _p, C ₀the comprehensive parameters forming.

Can find out V thus _outwith V ₁there is fixing relation, can be expressed as the form of transport function, this transport function with

r is relevant, if known these parameters, known V ₁with V _outrelation.

For formula is simplified, if three-phase line position is symmetrical, even in figure so

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

(formula 8)

By above analysis, the invention provides a kind of three-phase based on D_dot principle affects voltage compensating method, and it comprises the steps:

Step 1, by a wherein phase voltage V of three-phase voltage ₁access the threephase potential transformer based on D_dot principle as above.

The voltage V at the direct earth capacitance two ends of threephase potential transformer described in step 2, employing oscilloscope measurement _out.

Step 3, employing formula (7) or (8) calculate V ₁, i.e. the voltage of the phase of surveying.

Lift an example below, this process described:

As shown in Figure 7 in test unit, by being arranged on three voltage sensors on three-phase wire and the lightning protection of ground and pole line, form.Wherein the electric wire of three horizontal positioned has 10 meters far away apart from ground, the about 5.78KV of voltage magnitude on cable conductor, and frequency 50Hz, every phase is respectively A, B, C from left to right.

In l-G simulation test, we use X1000 high-voltage probe to measure magnitude of voltage and the phase place on three-phase line, measurement result V ₁as shown in table 1.

Table one:

By Multi simulation running and test, we obtain on electric wire and between electrode, (comprise the comprehensive parameters of electrode I, electrode II and three wire capacitance, can try to achieve by Thevenin's theorem) capacitor C forming ₁₀the capacitor C obtaining with sensor manufacturer withstand voltage test _1Mwhen (being direct earth capacitance) meets following the relation:

C _1M=0.17C ₁₀(formula 8)

Now, threephase potential transformer output voltage shows below on oscillograph:

Table two:

By the V of formula 7 ₁with V _outrelation, calculate the voltage V on electrode ₁' magnitude of voltage and phase pushing figure, as follows:

Table three:

Contrast table one is known with the data that table three obtains, as stated above, and calculating sensor output V _outcorresponding V ₁', with actual value V ₁compare, magnitude of voltage and phase pushing figure differ very little, have improved the measuring accuracy of sensor.Can reflect comparatively exactly the situation of change of voltage waveform on cable thus.

The present invention, by improving D_dot sensor construction and considering to analyze adjacent phase electric field and the impact of measurement mechanism on metering circuit on three-phase line, a kind of compensation method is proposed thus, oscilloscope measurement result is revised, obtain thus approaching the numerical value of truth, be conducive to floating voltage variation and fault diagnosis and on-line monitoring and the over-voltage waveform that captures high frequency in relay protection system, to line voltage, measurement is significant.

Finally explanation is, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement technical scheme of the present invention, and not departing from aim and the scope of technical solution of the present invention, it all should be encompassed in the middle of claim scope of the present invention.

Claims (6)

1. the threephase potential transformer based on D_dot principle, it is characterized in that: comprising: ring electrode I, ring electrode II, insulating support and direct earth capacitance, described insulating support comprises: semicircle bracket I, semicircle bracket I I and sway brace, described sway brace is arranged on described semicircle bracket I, on the sidewall of semicircle bracket I I, and described semicircle bracket I, semicircle bracket I I with one heart setting is formed for the through hole passing for measured conductor, described ring electrode I, ring electrode II arranges with one heart, and be embedded in respectively in described semicircle bracket I and semicircle bracket I I, described ring electrode I, ring electrode II by wire and described direct earth capacitance and connect.

2. the threephase potential transformer based on D_dot principle as claimed in claim 1, is characterized in that: described ring electrode I, ring electrode II are the metallic aluminium ring that shape is identical.

3. the threephase potential transformer based on D_dot principle as claimed in claim 2, is characterized in that: the internal diameter of described ring electrode I, ring electrode II is between 60 to 70mm, and external diameter is between 70 to 80mm.

4. the threephase potential transformer based on D_dot principle as claimed in claim 1, is characterized in that: also comprise: be arranged on described sway brace for regulating the adjusting knob of described semicircle bracket I I position.

5. the threephase potential transformer based on D_dot principle as claimed in claim 4, is characterized in that: the adjustable range scope between described semicircle bracket I, II is between 0 to 50mm.

6. the three-phase based on D_dot principle affects a voltage compensating method, it is characterized in that: comprise the steps:

By a wherein phase voltage V of three-phase voltage ₁the threephase potential transformer based on D_dot principle of access as described in any one in claim 1 to 5;

The voltage V at the direct earth capacitance two ends of threephase potential transformer described in employing oscilloscope measurement _out;

Adopt formula:

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

Calculate V ₁;

Wherein,

with

be respectively capacitor C ₁₄and C ₁₅,

for C ₂₅with C ₃₅value in parallel, for C ₂₄with C ₃₄shunt capacitance, the resistance on the concentric conductor that r is connecting electrode,

for C _m, C _p, R ₀, R _p, C ₀the comprehensive parameters forming, wherein C _ijthe electric capacity that represents i electric wire and j electrode, C _mfor direct earth capacitance, R _pand C _presistance, electric capacity that the measuring sonde of introducing while being respectively access oscillograph is introduced, R _oand C ₀be respectively resistance, electric capacity that access oscillograph is introduced.

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