CN203858279U - Three-phase voltage mutual inductor based on D_dot principle - Google Patents

Abstract

The utility model provides a three-phase voltage mutual inductor based on the D_dot principle. The three-phase voltage mutual inductor comprises an annular electrode I, an annular electrode II, an insulating support and a grounding capacitor. The insulating support comprises a semicircular support I, a semicircular support II and a supporting arm. The supporting arm is arranged on the side walls of the semicircular support I and the semicircular support II, and the semicircular support I and the semicircular support II are concentrically arranged so that a through hole used for penetration of the tested conductor is formed. The annular electrode I and the annular electrode II are concentrically arranged and 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 grounding capacitor and ground via conductive wires. The three-phase voltage mutual inductor has characteristics of being small in volume, simple in structure, great in insulating performance, safe in measurement, etc.

Description

Based on the threephase potential transformer of D_dot principle

Technical field

The utility model relates to electrical equipment technical field, relates in particular to a kind of threephase potential transformer based on D_dot principle.

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 (being called for short: D_dot sensor) based on D_dot principle is measured owing to adopting electric charge induction principle to realize, but not energy transmission, therefore can realize noncontacting measurement, while being applied in the transformer station of voltage levels, can make secondary side almost export without any electric current, when realizing secondary side safety detection, ensure primary side not impact, and because whole sensor does not exist inductive device, avoid 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, therefore be called based on D_dot the voltage sensor of principle.

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

Utility model content

In view of this, the utility model provides a kind of threephase potential transformer based on D_dot principle, has that volume is little, simple in structure, a feature such as good insulation preformance and measurement safety.

The utility model 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 parallel connection.

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 when screw pine, semicircle bracket I I can move up and down, and in the time reaching correct position, screw is screwed.

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

The beneficial effects of the utility model:

Threephase potential transformer based on D_dot principle of the present utility model is mainly made up 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, ensure to measure security simultaneously.

Brief description of the drawings

Below in conjunction with drawings and Examples, the utility model is 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, do a closed Gauss surface 4 on metallic conductor surface, 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, and therefore 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 that realizes measurement by energy transmission, capacitance type potential transformer) difference, it can realize noncontacting measurement, therefore while being applied in the transformer station of voltage levels, can make secondary side almost export without any electric current, when realizing secondary side safety detection, ensure primary side not impact, and because whole sensor does not exist inductive device, avoid the threat of the ferroresonance of sensor generation.

As shown in Figures 2 and 3, the threephase potential transformer based on D_dot principle that the utility model provides 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 the adjusting knob for regulating semicircle bracket I I position, and 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 when screw pine, semicircle bracket I I can move up and down, and in the time 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) and 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, when 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 formed by 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, ensure 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:

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

Wherein C 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 utility model 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):

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

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

As Fig. 4, wherein C 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 the measurement electric capacity for measuring output voltage simultaneously, Z _scuse oscillographic equiva lent impedance for measuring, 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 _ijrepresent the electric capacity of i cable and j electrode, for example: C ₁₄represent the electric capacity of 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 when access oscillograph) are introduced, R _oand C ₀be respectively resistance, electric capacity that access oscillograph is introduced, consider thus the mutual capacitance between adjacent phase circuit and the electrode of this phase upper sensor, and this is performed an analysis, by revising oscilloscope measurement result, can compensate, obtain the voltage waveform that approaches 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:

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

$V_{\mathrm{out}}\stackrel{.}{Z}({\stackrel{.}{I}}_1+{\stackrel{.}{I}}_2+{\stackrel{.}{I}}_3-{\stackrel{.}{I}}_4)$ (formula 6)

That is:

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

(formula 7)

In 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 thus V _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 symmetry, even in figure so

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

(formula 8)

By above analysis, the utility model provides a kind of three-phase based on D_dot principle to affect 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, form by being arranged on three voltage sensors on three-phase wire and the lightning protection of ground and pole line.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 the capacitor C forming when (comprising the comprehensive parameters of electrode I, electrode II and three wire capacitance, can try to achieve by Thevenin's theorem) on electric wire and between electrode 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 ₁magnitude 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 thus the situation of change of voltage waveform on cable.

The utility model, 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 the technical solution of the utility model to be described, although the utility model 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 the technical solution of the utility model, and not departing from aim and the scope of technical solutions of the utility model, it all should be encompassed in the middle of claim scope of the present utility model.

Claims (5)

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, the voltage access oscillograph of described direct earth capacitance two ends output.

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.