CN100549709C - The computing method and the device of circulation in the Y/ △ transformer triangle winding - Google Patents

Abstract

The invention discloses the computing method and the device of circulation in a kind of Y/ △ transformer triangle winding, belong to the power system main equipment technical field of relay protection.Method comprises: winding resistance and the leakage inductance of obtaining Y/ △ transformer both sides; Obtain the residual voltage of Y side or the three-phase winding voltage of measurement Y side; Obtain the zero-sequence current of Y side or the three-phase winding current of measurement Y side; Utilize winding resistance, leakage inductance, three-phase winding current and the three phase winding induced potentials of both sides, list the three-phase winding voltage equation of both sides respectively; According to the relation between each parameter to all equation computings, cancellation wherein in △ side winding all parameters that can not obtain the circulation draw circulation.Device comprises acquisition module, voltage computing module and circulation computing module.The present invention can calculate the circulation in the △ side winding when transformer △ side winding does not make Current Transformer, thereby can calculate the equivalent instantaneous inductor of each phase of transformer, and then differentiates the excitation surge current of transformer.

Description

Calculation Method and Device of Circulating Current in Delta Winding of Y/△ Transformer

technical field

The invention relates to the technical field of relay protection for main equipment in a power system, in particular to a calculation method and device for circulating current in a delta winding of a Y/△ transformer.

Background technique

Power transformers in the form of Y/△ wiring are widely used in power systems. Since one side of the primary and secondary windings is connected into △, it can ensure that the phase potential is close to a sine wave and avoid distortion of the phase potential waveform. However, there is a phase difference between the line currents on both sides of the Y/△ transformer. In order to make the differential current in the normal operation of the transformer differential protection zero, it is necessary to convert the current on one side of the transformer to the other side to eliminate the phase difference between them. For the existing Y→△ current compensation method and △→Y current compensation method, due to the influence of the circulating current in the △ winding, the differential current obtained after the transformation cannot reflect the real change of the excitation current of the phase, so that the second harmonic based on this The wave excitation inrush current criterion has the disadvantage of being unreliable.

The existing technology uses the winding current to calculate the differential current. The differential current can eliminate the influence of the circulating current and can truly reflect the change of the excitation inrush current of the transformer. The identification criterion of the excitation inrush current based on the equivalent instantaneous inductance developed thereby can reliably identify the inrush current of the transformer. Exciting inrush current. The excitation inrush current criterion based on the equivalent instantaneous inductance needs to obtain the winding currents on each side of the transformer. For power transformers with a voltage level of 500kV and above, a three-phase transformer form consisting of a single-phase transformer is usually used. The △ side winding (ie, the delta winding) The winding current transformer can be configured to measure the winding current; however, for power transformers with a voltage level of 220kV and below, see Figure 1, usually in the form of three-phase three-column, the winding current transformer cannot be configured in the △ side winding, so that it cannot be measured The winding current on the △ side includes _ia , _ib , _ic and the circulating current _ip , so the application of the inrush current criterion based on the equivalent instantaneous inductance is limited.

Contents of the invention

In order to obtain the circulating current in the delta winding of the Y/△ transformer without using a current transformer, the present invention provides a calculation method and device for the circulating current in the delta winding of the Y/△ transformer. Described technical scheme is as follows:

A calculation method for circulating current in a Y/△transformer delta winding, said method comprising:

Obtain the winding resistance and leakage inductance of the Y side and the △ side of the Y/△ transformer;

Obtaining the zero-sequence voltage on the Y side or measuring the three-phase winding voltage on the Y side;

Obtaining the zero-sequence current on the Y side or measuring the three-phase winding current on the Y side;

Using the winding resistance, leakage inductance, three-phase winding current and three-phase winding induced potential of the Y side, the equations of the three-phase winding voltage on the Y side are respectively listed, and the equation of each phase winding voltage on the Y side is: :

The phase winding voltage = winding resistance * the phase winding current + leakage inductance * the first order derivative of the phase winding current to time + the phase winding induced potential;

All parameters in the equation are parameters on the Y side;

Using the winding resistance, leakage inductance, three-phase winding current and three-phase winding induced potential on the △ side, the equations of the three-phase winding voltage on the △ side are respectively listed, and the equation of each phase winding voltage on the △ side is: :

The phase winding voltage = winding resistance * the phase winding current + leakage inductance * the first order derivative of the phase winding current to time + the phase winding induced potential;

All parameters in the equation are parameters of the Δ side;

According to the relationship between the circulating current in the winding on the △ side and the current of the three-phase winding, the relationship between the voltages of the three-phase winding on the △ side, the relationship between the current of the three-phase winding on the Y side and the zero-sequence current, the The relationship between the three-phase winding voltage on the Y side and the zero-sequence voltage, and the conversion relationship between each parameter on the Y side and the corresponding parameter on the △ side, for all the three-phase winding voltages The equations are operated to eliminate all unobtainable parameters in all the equations except the circulating current in the winding on the △ side to obtain the circulating current in the winding on the △ side.

The relationship between the circulating current in the winding on the △ side and the three-phase winding current is: the sum of the three-phase winding currents is equal to three times the circulating current in the winding;

The relationship between the voltages of the three-phase windings on the △ side is: the sum of the voltages of the three-phase windings is zero;

The relationship between the Y-side three-phase winding current and the zero-sequence current is: the sum of the three-phase winding currents is equal to three times the zero-sequence current;

The relationship between the Y-side three-phase winding voltage and the zero-sequence voltage is: the sum of the three-phase winding voltages is equal to three times the zero-sequence voltage;

The conversion relationship between each parameter on the Y side and the corresponding parameter on the △ side is:

When converting the △ side parameters to the Y side:

△ side voltage parameter converted to Y side = △ side voltage parameter * transformer ratio;

△ side current parameter converted to Y side = △ side current parameter/transformer ratio;

The △ side winding resistance parameter converted to the Y side = the △ side winding resistance parameter * the square of the transformation ratio of the transformer;

The △ side leakage inductance parameter converted to the Y side = the △ side leakage inductance parameter * the square of the transformation ratio of the transformer;

When the parameters on the Y side are converted to the △ side:

Y-side voltage parameter converted to △ side = Y-side voltage parameter/transformer ratio;

The Y-side current parameter converted to the △ side = the Y-side current parameter * transformer ratio;

The Y-side winding resistance parameter converted to the △ side = the Y-side winding resistance parameter/the square of the transformation ratio of the transformer;

The Y-side leakage inductance parameter converted to the △ side = the Y-side leakage inductance parameter/the square of the transformation ratio of the transformer.

The step of calculating the circulating current in the winding on the △ side specifically includes:

Converting the values of all parameters on the △ side to the values on the Y side according to the transformation ratio relationship of the transformer, or converting the values of all parameters on the Y side to the values on the △ side;

The equations of the three-phase winding voltages on the Y side and the △ side are respectively summed and then subtracted to obtain a differential equation;

Solving the differential equation and performing discrete operations according to a fixed sampling interval to obtain the circulating current in the winding on the Δ side.

When the neutral point on the Y side is grounded, the three-phase winding voltage on the Y side is a voltage to ground;

When the neutral point on the Y side is not grounded, the voltage of the three-phase winding on the Y side is the voltage to the neutral point.

A calculation device for circulating current in a Y/△transformer delta winding, said device comprising:

The obtaining module is used to obtain the winding resistance and leakage inductance of the Y side and the △ side of the Y/△ transformer, obtain the zero-sequence voltage of the Y side or measure the three-phase winding voltage of the Y side, and obtain the Zero-sequence current or measure the three-phase winding current on the Y side;

The voltage calculation module is used to use the winding resistance and leakage inductance of the Y side obtained by the acquisition module, and use the three-phase winding current and the three-phase winding induced potential of the Y side to list the Y side according to the following formula The equation of each phase winding voltage in the three-phase winding voltage:

The phase winding voltage = winding resistance * the phase winding current + leakage inductance * the first order derivative of the phase winding current to time + the phase winding induced potential;

All parameters in the equation are parameters on the Y side;

And using the winding resistance and leakage inductance of the △ side acquired by the acquisition module, and using the three-phase winding current and the three-phase winding induced potential on the △ side, respectively list the equations of the three-phase winding voltage on the △ side, The equations of each phase winding voltage in the three-phase winding voltage on the △ side are respectively listed according to the following formula:

The phase winding voltage = winding resistance * the phase winding current + leakage inductance * the first order derivative of the phase winding current to time + the phase winding induced potential;

All parameters in the equation are parameters of the Δ side;

The circulating current calculation module is used to calculate the relationship between the circulating current in the winding on the △ side and the current of the three-phase winding, the relationship between the voltages of the three-phase winding on the △ side, the current of the three-phase winding on the Y side and the zero-sequence current The relationship between the three-phase winding voltage on the Y side and the zero-sequence voltage, and the conversion relationship between each parameter on the Y side and the corresponding parameter on the △ side, for the All the three-phase winding voltage equations listed in the above-mentioned voltage calculation module are calculated, and all unobtainable parameters except the circulating current in the winding on the △ side are eliminated in all the equations, and the winding on the △ side is obtained. circulation.

The circulation calculation module specifically includes:

A conversion unit, configured to convert the values of all parameters on the △ side to the values on the Y side according to the ratio relationship of the transformer, or convert the values of all parameters on the Y side to the values on the △ side ;

The equation solving unit is used to sum and subtract the three-phase winding voltage equations on the Y side and the Δ side listed in the voltage calculation module to obtain a differential equation, and solve the differential equation;

The discrete unit is configured to perform discrete operations on the equations solved by the equation solving unit according to a fixed sampling interval, so as to obtain the circulating current in the winding on the Δ side.

The above technical scheme has the following beneficial effects:

By obtaining the winding resistance and leakage inductance on both sides of the Y/△ transformer, measure the three-phase winding current and three-phase winding voltage on the Y side, list the equations of the three-phase winding voltage on both sides, use the transformer principle to understand the differential equation and perform discrete operations , the circulating current in the △ side winding can be calculated, which solves the problem in the prior art that the △ side winding of the Y/△ transformer cannot measure the circulating current of the △ side winding without using a current transformer, so that the equivalent instantaneous inductance of each phase of the transformer can be calculated , and then identify the inrush current of the transformer.

Description of drawings

Fig. 1 is the schematic diagram of Y/△ connection transformer in the prior art;

Fig. 2 is the flowchart of the calculation method of circulating current in the delta winding of Y/△ transformer that the embodiment of the present invention provides;

Fig. 3 is the structural diagram of the calculating device of circulating current in the delta winding of Y/△ transformer that the embodiment of the present invention provides;

4 is a schematic diagram of the comparison between the calculated circulating current and the actually measured circulating current when the neutral point on the Y side of the transformer is not grounded and the Y side of the transformer is switched on with no load in an embodiment of the present invention;

5 is a schematic diagram of the comparison of transformer equivalent instantaneous inductance calculated from the calculated circulating current and the actually measured circulating current when the neutral point of the Y side of the transformer is not grounded and the Y side of the transformer is closed with no load in the embodiment of the present invention;

6 is a schematic diagram of the comparison between the calculated circulating current and the actually measured circulating current when the neutral point on the Y side of the transformer is grounded and the Y side of the transformer is switched on with no load in an embodiment of the present invention;

7 is a schematic diagram of the comparison of the equivalent instantaneous inductance of the transformer calculated from the calculated circulating current and the actually measured circulating current when the neutral point of the Y side of the transformer is grounded and the Y side of the transformer is closed with no load in the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

In the embodiment of the present invention, by obtaining the winding resistance and leakage inductance on the Y side and the △ side of the Y/△ transformer, the current transformer and the voltage transformer are used to measure the three-phase winding current and the three-phase winding voltage on the Y side respectively. According to the Y side and △ The equation of the three-phase winding voltage on the side, establishes the relationship between the winding current of the △ side winding and the voltage and current of the winding on the Y side, and deduces the circulating current of the winding on the △ side through differential and discrete calculations, thus solving the Y/△ side winding in the prior art The transformer delta side winding cannot measure the circulating current of the delta side winding without using a current transformer.

The Y/△ transformer in Fig. 1 is not equipped with a current transformer on the △ side, or it is configured but not used as an example. Referring to Fig. 2, the embodiment of the present invention provides a Y/△ transformer delta winding. The calculation method specifically includes the following steps:

Step 101: Obtain the winding resistance r ₁ and leakage inductance L ₁ of the Y side of the Y/Δ transformer, and the winding resistance r ₂ and leakage inductance L ₂ of the Δ side.

Winding resistance and leakage inductance are fixed parameters of the transformer, which can usually be calculated from the parameters marked on the transformer nameplate. Due to the transformation ratio of the transformer, for the convenience of calculation, the parameters on the △ side in this embodiment are converted to the parameters on the Y side according to the transformation ratio relationship, that is, the winding resistance r ₂ and leakage inductance L ₂ in this step and the parameters involved in the following steps The parameters on the △ side are converted to the parameters on the Y side. The specific conversion relationship is:

△ side voltage parameter converted to Y side = △ side voltage parameter * transformer ratio;

△ side current parameter converted to Y side = △ side current parameter/transformer ratio;

The △ side winding resistance parameter converted to the Y side = the △ side winding resistance parameter * the square of the transformation ratio of the transformer;

The leakage inductance parameter of the △ side after converted to the Y side = the leakage inductance parameter of the △ side * the square of the transformation ratio of the transformer.

Step 102: Configure voltage transformers on the Y side, measure the three-phase winding voltages u _A , u _B , u _C on the Y side; or obtain the zero-sequence voltage u ₀ on the Y side, u ₀ can be calculated from the three-phase winding voltages, namely Based on the measured three-phase winding voltage, the zero-sequence voltage u ₀ is further calculated.

Step 103: Configure a current transformer on the Y side, and measure the three-phase winding currents i _A , i _B , and i _C on the Y side. ; Or obtain the zero-sequence current i ₀ on the Y side; when the neutral point on the Y side is grounded, i ₀ can be measured by the neutral point current transformer or calculated from the winding current; when the neutral point on the Y side is not grounded, i ₀ is zero.

Step 104: Set the induced potentials of the three-phase windings on the Y side as e _A , e _B , e _C , the induced potentials of the three-phase windings on the △ side as e _a , e _b , e _c , and the currents of the three-phase windings on the △ side as i _a , i _b , i _c , the circulating current in the winding is i _p , and the three-phase winding voltages on the △ side are u _ac , u _ba , u _cb , then the equation of the three-phase winding voltage on the Y side is listed:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

And list the equations of the three-phase winding voltage on the △ side:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; ac</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; b</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; cb</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; e</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Step 105: According to the principle of the transformer, the following relationship can be obtained:

u _A +u _B +u _C =3u ₀ , i _A +i _B +i _C =3i ₀ , u _ac +u _ba +u _cb =0, i _a +i _b +i _c =3i _p ;

e _A = e _a , e _B = e _b , e _C = e _c ;

The equations of the three-phase winding voltages on the Y side and the △ side are respectively summed and then subtracted, that is, subtract the sum of the three equations in (2) from the sum of the three equations in (1), and use the above relationship to eliminate the For all unobtainable parameters except the circulation ip (i.e. e _A , e _a , e _B , e _b , e _C and e _c and ia , _{i b ,} and i _c ), the following equations are obtained:

${\mathrm{<figure-callout\; id="0"\; label="u"\; filenames="C20071011882600152.png,C20071011882600162.png"\; state="\{\{state\}\}">u</figure-callout>}}_0=r_1{\mathrm{<figure-callout\; id="0"\; label="i"\; filenames="C20071011882600152.png,C20071011882600162.png"\; state="\{\{state\}\}">i</figure-callout>}}_0+L_1\frac{{\mathrm{di}}_0}{\mathrm{dt}}-r_2{i}_p-L_2\frac{{\mathrm{di}}_p}{\mathrm{dt}},$ Right now: $\frac{{\mathrm{di}}_p}{\mathrm{dt}}+\frac{r_2}{L_2}{i}_p=\frac{1}{L_2}(r_1{\mathrm{<figure-callout\; id="0"\; label="i"\; filenames="C20071011882600152.png,C20071011882600162.png"\; state="\{\{state\}\}">i</figure-callout>}}_0+L_1\frac{{\mathrm{di}}_0}{\mathrm{dt}}-u_0)---\left(3\right)$

Step 106: Solve the differential equation (3), and obtain the circulating current i _p in the △ side winding as:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; t</span>}}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="u"\; filenames="C20071011882600152.png,C20071011882600162.png"\; state="\{\{state\}\}">u</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; ]</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; t</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Step 107: Discretize the formula (4) to obtain the calculation formula of the circulating current i _p in the △ side winding:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span>}\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; [</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Among them, k is the calculation point, and △T is the sampling interval; the value of k can be different according to the needs, such as taking 24 points or 48 points in a power frequency cycle (20ms), and so on.

There is no fixed sequence for the above steps 101 to 103, and it doesn't matter which step is performed first.

Referring to Fig. 3, the embodiment of the present invention also provides a calculation device for the circulating current in the delta winding of the Y/△ transformer, which specifically includes:

(1) Obtaining module, for obtaining the winding resistance and the leakage inductance of the Y side and the Δ side of the Y/△ transformer, obtaining the zero-sequence voltage of the Y side or measuring the three-phase winding voltage of the Y side, obtaining the zero-sequence current on the Y side or measure the three-phase winding current on the Y side;

(2) Voltage calculation module, used to utilize the winding resistance and leakage inductance of the Y side obtained by the acquisition module, and utilize the three-phase winding current and the three-phase winding induced potential of the Y side to list the three-phase winding voltage of the Y side respectively equation; and use the winding resistance and leakage inductance of the △ side obtained by the acquisition module, and the three-phase winding current and the three-phase winding induced potential on the △ side to list the equations of the three-phase winding voltage on the △ side;

(3) The circulating current calculation module is used to calculate the relationship between the circulating current in the winding on the △ side and the three-phase winding current, the relationship between the voltages of the three-phase winding on the △ side, the relationship between the three-phase winding current and the zero-sequence current on the Y side, The relationship between the three-phase winding voltage on the Y side and the zero-sequence voltage, and the ratio relationship between each parameter on the Y side and the corresponding parameter on the △ side are calculated for all three-phase winding voltage equations listed in the voltage calculation module , eliminate all unobtainable parameters in all equations except the circulating current in the △ side winding, and obtain the circulating current in the △ side winding.

Wherein, the voltage calculation module may specifically include:

1) The Y-side voltage calculation unit is used to list the equation of the winding voltage of each phase on the Y-side according to the following formula:

The phase winding voltage = winding resistance * the phase winding current + leakage inductance * the first order derivative of the phase winding current to time + the phase winding induced potential; all parameters in this equation are parameters on the Y side;

2) The voltage calculation unit on the △ side, which is used to list the equation of the winding voltage of each phase on the △ side according to the following formula:

The phase winding voltage = winding resistance * the phase winding current + leakage inductance * the first order derivative of the phase winding current to time + the phase winding induced potential; all parameters in this equation are parameters on the △ side.

Among them, the circulation calculation module may specifically include:

1) The conversion unit is used to convert the values of all parameters on the △ side to the values on the Y side according to the transformation ratio relationship of the transformer, or to convert the values of all parameters on the Y side to the values on the △ side;

2) The equation solving unit is used to sum and subtract the voltage equations of the three-phase windings on the Y side and the △ side listed in the voltage calculation module to obtain a differential equation, and solve the differential equation;

3) The discrete unit is used to perform discrete operations on the equations solved by the equation solving unit according to a fixed sampling interval to obtain the circulating current in the winding on the △ side.

In this embodiment, when the neutral point on the Y side is grounded (switch K is closed), the three-phase winding voltage on the Y side is the ground voltage; when the neutral point on the Y side is not grounded (switch K is off), the voltage on the Y side The three-phase winding voltage is the voltage to the neutral point. In addition, in this embodiment, the method of converting the value of the parameter on the △ side to the value on the Y side according to the transformation ratio relationship of the transformer can also be replaced by: converting the value of the parameter on the Y side to the value on the △ side according to the transformation ratio relationship of the transformer way, that is, the parameters on the Y side are converted to the △ side according to the following relationship:

Y-side voltage parameter converted to △ side = Y-side voltage parameter/transformer ratio;

The Y-side current parameter converted to the △ side = the Y-side current parameter * transformer ratio;

The Y-side winding resistance parameter converted to the △ side = the Y-side winding resistance parameter/the square of the transformation ratio of the transformer;

The Y-side leakage inductance parameter converted to the △ side = the Y-side leakage inductance parameter/the square of the transformation ratio of the transformer;

Accordingly, the listed voltage equations and calculation methods remain unchanged.

In order to verify the accuracy of the above technical solution, the circulating current in the △ side winding is calculated according to the above method and the circulating current in the △ side winding is actually measured with a current transformer under the same sampling conditions for the same transformer, and compared , and then use the calculated circulating current in the △ side winding and the actually measured circulating current in the △ side winding to calculate the three-phase equivalent instantaneous inductance respectively, and compare them to get Figure 4, Figure 5, Figure 6 and Figure 7. Among them, Figure 4 and Figure 5 are respectively the current-time graph and the three-phase equivalent instantaneous inductance-time graph obtained when the neutral point of the Y side of the transformer is not grounded and the Y side is closed with no load, and Figure 6 and Figure 7 are respectively the transformer The current-time curve diagram and the three-phase equivalent instantaneous inductance-time curve diagram obtained when the neutral point of the Y side is grounded and the Y side is closed with no load. It can be seen from Fig. 4 to Fig. 7 that regardless of whether the neutral point is grounded or not, the circulation current calculated by the technical solution described in the embodiment of the present invention is very close to the actual measured circulation current, and the calculated circulation current can reflect the actual circulation current The change characteristics of the three-phase equivalent instantaneous inductance obtained by the calculated circulation operation and the three-phase equivalent instantaneous inductance obtained by the measured circulation operation are very close, and the three-phase equivalent instantaneous inductance obtained by the calculated circulation operation can reflect the actual The variation characteristics of the three-phase equivalent instantaneous inductance.

In the embodiment of the present invention, by obtaining the winding resistance and leakage inductance on both sides of the Y/△ transformer, measuring the three-phase winding current and the three-phase winding voltage on the Y side, listing the equations of the three-phase winding voltage on both sides, and using the transformer principle to understand the differential equation And carry out discrete operation, can calculate the circulating current in the △ side winding, solve the problem in the prior art that the △ side winding of the Y/△ transformer cannot measure the circulating current of the △ side winding without using a current transformer, so that the current of each phase of the transformer can be calculated Equivalent instantaneous inductance, and then determine the excitation inrush current of the transformer. In addition, the technical solutions described in the embodiments of the present invention have no limitation on the voltage level of the transformer, that is, the voltage level of 500kV and above, or the voltage level of 220kV and below are applicable, and it has nothing to do with the grounding method of the Y-side winding of the transformer. applicability.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (6)

1. computing method of circulation in the Y/ △ transformer triangle winding is characterized in that described method comprises:

Obtain the Y side of Y/ △ transformer and the winding resistance and the leakage inductance of △ side;

Obtain the residual voltage of described Y side or measure the three-phase winding voltage of described Y side;

Obtain the zero-sequence current of described Y side or measure the three-phase winding current of described Y side;

Utilize winding resistance, leakage inductance and three-phase winding current and the three phase winding induced potentials of described Y side, list the equation of the three-phase winding voltage of described Y side respectively, wherein, the equation of every phase winding voltage of described Y side is:

This this phase winding electric current of phase winding electric current+leakage inductance * of this phase winding voltage=winding resistance * is to first order derivative+this phase winding induced potential of time;

All parameters in this equation are the parameter of described Y side;

Utilize winding resistance, leakage inductance and three-phase winding current and the three phase winding induced potentials of described △ side, list the equation of the three-phase winding voltage of described △ side respectively, wherein, the equation of every phase winding voltage of described △ side is:

This this phase winding electric current of phase winding electric current+leakage inductance * of this phase winding voltage=winding resistance * is to first order derivative+this phase winding induced potential of time;

All parameters in this equation are the parameter of described △ side;

Relation according to circulation in the winding of described △ side and three-phase winding current, relation between the described △ side three-phase winding voltage, relation between described Y side three-phase winding current and the described zero-sequence current, relation between described Y side three-phase winding voltage and the described residual voltage, and the relation of the conversion between the parameter of each parameter of described Y side and corresponding described △ side, described all three-phase winding voltage equations are carried out computing, in described all equations of cancellation in described △ side winding all parameters that can not obtain the circulation, draw the circulation in the winding of described △ side.

2. the computing method of circulation is characterized in that in the Y/ △ transformer triangle winding according to claim 1,

The pass of circulation and three-phase winding current is in the winding of described △ side: described three-phase winding current sum equals the circulation in three times the described winding;

Pass between the described △ side three-phase winding voltage is: described three-phase winding voltage sum is zero;

Pass between described Y side three-phase winding current and the described zero-sequence current is: the described zero-sequence current that described three-phase winding current sum equals three times;

Pass between described Y side three-phase winding voltage and the described residual voltage is: the described residual voltage that described three-phase winding voltage sum equals three times;

Conversion between each parameter of described Y side and the parameter of corresponding described △ side is closed:

When △ side parameter is converted the Y side:

Convert the △ side voltage parameter=△ side voltage parameter * transformer voltage ratio of Y rear flank;

Convert the △ side current parameters=△ side current parameters/transformer voltage ratio of Y rear flank;

Convert the Y rear flank △ side winding resistance parameter=△ side winding resistance parameter * transformer voltage ratio square;

Convert the Y rear flank △ side leakage inductance parameters=△ side leakage inductance parameters * transformer voltage ratio square;

When Y side parameter is converted the △ side:

Convert the Y side voltage parameter=Y side voltage parameter/transformer voltage ratio of △ rear flank;

Convert the Y side current parameters=Y side current parameters * transformer voltage ratio of △ rear flank;

Convert the △ rear flank Y side winding resistance parameter=Y side winding resistance parameter/transformer voltage ratio square;

Convert the △ rear flank Y side leakage inductance parameters=Y side leakage inductance parameters/transformer voltage ratio square.

3. the computing method of circulation is characterized in that in the Y/ △ transformer triangle winding according to claim 1, and the step that calculates the circulation in the winding of described △ side specifically comprises:

According to the no-load voltage ratio of described transformer relation, the value of described all parameters of △ side is converted the value of described Y side, perhaps the value of described all parameters of Y side is converted the value of described △ side;

The equation of the three-phase winding voltage of described Y side and △ side sued for peace respectively to subtract each other again obtain a differential equation;

Separate the described differential equation and obtain circulation in the winding of described △ side according to the computing of dispersing of fixing sampling interval.

4. the computing method of circulation is characterized in that in the Y/ △ transformer triangle winding according to claim 1,

When the neutral ground of described Y side, the three-phase winding voltage of described Y side is a voltage-to-ground;

When the isolated neutral of described Y side, the three-phase winding voltage of described Y side is a voltage to neutral.

5. the calculation element of circulation in the Y/ △ transformer triangle winding is characterized in that described device comprises:

Acquisition module is used to obtain the Y side of Y/ △ transformer and the winding resistance and the leakage inductance of △ side, obtains the residual voltage of described Y side or measures the three-phase winding voltage of described Y side, obtains the zero-sequence current of described Y side or measures the three-phase winding current of described Y side;

The voltage computing module, be used to utilize the winding resistance and the leakage inductance of the Y side that described acquisition module obtains, and the three-phase winding current and the three phase winding induced potentials that utilize described Y side, list the equation of every phase winding voltage in the three-phase winding voltage of described Y side respectively according to following formula:

This this phase winding electric current of phase winding electric current+leakage inductance * of this phase winding voltage=winding resistance * is to first order derivative+this phase winding induced potential of time;

All parameters in this equation are the parameter of described Y side;

And utilize the winding resistance and the leakage inductance of the △ side that described acquisition module obtains, and the three-phase winding current and the three phase winding induced potentials that utilize described △ side, list the equation of every phase winding voltage in the three-phase winding voltage of described △ side respectively according to following formula:

This this phase winding electric current of phase winding electric current+leakage inductance * of this phase winding voltage=winding resistance * is to first order derivative+this phase winding induced potential of time;

All parameters in this equation are the parameter of described △ side;

The circulation computing module, be used for relation according to the winding circulation and the three-phase winding current of described △ side, relation between the described △ side three-phase winding voltage, relation between described Y side three-phase winding current and the described zero-sequence current, relation between described Y side three-phase winding voltage and the described residual voltage, and the relation of the conversion between the parameter of each parameter of described Y side and corresponding described △ side, all three-phase winding voltage equations that described voltage calculating module column is gone out carry out computing, all parameters that can not obtain the circulation in described all equations of cancellation in the winding of described △ side draw the circulation in the winding of described △ side.

6. the calculation element of circulation in the Y/ △ transformer triangle winding according to claim 5 is characterized in that described circulation computing module specifically comprises:

The conversion unit is used for according to the no-load voltage ratio of described transformer relation, and the value of described all parameters of △ side is converted the value of described Y side, perhaps the value of described all parameters of Y side is converted the value of described △ side;

The unit of solving an equation, being used for sues for peace respectively to subtract each other to the three-phase winding voltage equation that described voltage calculates Y side that module column goes out and △ side again obtains a differential equation, and separates the described differential equation;

The computing of dispersing of discrete unit, the equation after being used for according to fixing sampling interval the described unit of solving an equation being separated obtains the circulation in the winding of described △ side.

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