CN101726716A - Method for measuring error of voltage transformer by nomography - Google Patents

Abstract

The invention belongs to the detection technology of electric equipment, and relates to a method for measuring the error of a voltage transformer with a graph algorithm. The method comprises the following steps in turn: a. generating rectangular coordinates by computer software, the rectangular coordinates take the angular difference δ of the voltage transformer as the abscissa, and the ratio difference f as the ordinate; b. on the coordinate axis according to the power factor

, the parameters of ratio difference f ₀ and angle difference δ ₀ measured under no-load conditions, set the no-load error point A of the voltage transformer; according to the power factor

, the ratio difference f _n1.0 and angle difference δ _n1.0 measured under the condition of rated load S _n , set the error point B of the voltage transformer; c. take A as the center of the circle, and take the percentage n% of the AB line segment as the radius Draw a circle; take the vector AB as the starting side and point A as the starting point, and rotate

Angle, draw a line equal to AB; the intersection point is the error point P of the voltage transformer; vertical projection is made on the ordinate and abscissa of the error point P respectively, and the ratio difference f _P and the angle difference δ _P of the voltage transformer are obtained. The invention can quickly and accurately detect the actual error of the voltage transformer on the operating site.

Description

The method of measuring error of voltage transformer by nomography

Technical field

The invention belongs to the detection technique of power equipment, relate to a kind of method of measuring error of voltage transformer by nomography.

Background technology

The load that voltage transformer (VT) connect (mainly being electric energy meter) is very big to the error characteristics influence of voltage transformer (VT).Electric energy meter type, quantity and the power factor that voltage transformer (VT) inserts is often to change.As the used voltage transformer (VT) of electricity power enterprise's online electric power meter, rated capacity is pacified near hectovolt, the load that is connected to becomes and has only several electric multi-functional electric energy meters now from tens induction type electric energy meters (forward and reverse meritorious, idle) in past, and capacity has only several volt-ampere.These multifunctional meters are rotated continually along with the update of table meter again, import table meter and homemade table meter, and induction type and electronic type, type is various, and load capacity and power factor value differ greatly.Induction type active electric energy meter and internal phase angle are that 90 ° reactive energy-meter power factor is 0.2-0.3, and 60 ° of idle tables of internal phase angle are 0.4,0.5.Homemade multifunctional meter 0.5,0.6.Introduce according to DL/T448-2000 " electric power meter technical management rules ", have near 1 or even capacitive, make that so the actual secondary power factor of voltage transformer (VT) is complicated and changeable.Also there are these problems in the use that power supply enterprise, client are used for the voltage transformer (VT) of trade settlement.Although " technical management rules " regulations " power factor of specified secondary power factor of voltage transformer (VT) and actual secondary load is approaching " can not accomplish that in actual motion meter is frequent to be changed mutual inductor along with showing, and will waste great amount of manpower and material resources like this.

The present type field voltage transformer error tester that uses, can only draw the error of the respective point under the perfect condition, the voltage transformer (VT) of on-the-spot operation has only 25% to be near the test point of " voltage transformer (VT) rules " regulation simultaneously, major part is to move outside the test point of rules regulations, be difficult to convenient, measure operating voltage transformer error accurately.Therefore, the present voltage transformer (VT) on-the-spot test method of using, it is qualified to judge whether substantially for the secondary load of on-the-spot voltage transformer (VT) reality and the error under the power factor condition, and can not test and calculate the error amount under its actual condition exactly.

Summary of the invention

Technical matters to be solved by this invention is, a kind of method of the measuring error of voltage transformer by nomography that can be quickly and accurately the actual error of moving on-the-spot voltage transformer (VT) be detected is provided.

Method of the present invention may further comprise the steps successively:

A. generate rectangular coordinate by computer software, this rectangular coordinate is a horizontal ordinate with the angular difference δ (angular error) of voltage transformer (VT), and ratio f (proportional error) is an ordinate; Initial point " 0 " top be-U ,-f (%), the below is U, f (%), initial point " 0 " left be-jU ,-δ, right-hand be jU, δ, lights in the ratio mark of setting from former on the longitudinal axis, the initial point top marks ratio 0-0.3, marks ratio+0.3-0 below the initial point; On transverse axis with ratio be 0.29 length do angular difference 10 ' length, the unit of obtaining head is the angular difference scale on this basis; Described U is a voltage;

B. on coordinate axis, press power factor (PF)

The ratio f that records under the idle condition ₀, angular difference δ ₀Parameter, fix voltage transformer (VT) no-load error point A; By power factor

Nominal load S _nThe ratio f that records under the condition _N1.0, angular difference δ _N1.0Parameter, fix the error point B of voltage transformer (VT); Connect A, B 2 points, then in power factor

Under the condition, 0～100% rated load S _nThe margin of error be distributed on the vectorial AB;

C. being the center of circle with A, is that radius is drawn circle with number percent n% (0～100%) AB line segment, and this locus circle is n%S _nThe error profile track; With vectorial AB has been initial line, is starting point with the A point, (when load characteristic is perception) or counterclockwise (when load characteristic is capacitive) rotation in the clockwise direction

(power factor angle) angle is drawn and the isometric line of AB, promptly obtains power factor (PF)

The error profile track of (m=0～1.0).Can obtain at n%S by the intersection point of locus circle with this isometric line _n, power factor (PF)

Voltage transformer error point P under the condition; Make vertical projection to ordinate and horizontal ordinate respectively at error point P, can obtain at n%S _n, power factor (PF) Voltage transformer (VT) ratio f under the condition _PWith angular difference δ _P

Method of the present invention is through verification experimental verification, and it is authentic and valid that its testing result is compared with the testing result that the traditional detection method that adopts the prior art rules obtains, and has proved the accuracy of its detection.And compare with classic method, method of the present invention only needs no-load point error and fully loaded, power factor when detecting be two groups of data of 1 time error, can calculate the error of other points, testing process is simple, convenient, fast, can reduce the test duration effectively, reduce the danger prestige danger that may exist in the test; Can reduce in the measuring process other factors again to the interference of error, more accurate than conventional test methodologies; Conventional test methodologies is because of being subjected to the restriction of equipment such as load box, a lot of test points can't be measured error with the instrument simulation, the most outstanding is exactly on-the-spot actual error situation, the inventive method can utilize two conventional error points easily to calculate the error point that conventional test methodologies can't be measured, and guarantees the accuracy of error.

Description of drawings

Fig. 1 is the angular difference of voltage transformer (VT) and the vector analysis synoptic diagram of ratio;

Fig. 2 is the synoptic diagram that angular difference converts;

Fig. 3 is that synoptic diagram is formed in the pressure drop of transformer;

Fig. 4 is the analysis principle figure of no-load transformer error;

Fig. 5 is that transformer has the analysis principle figure that carries error;

Fig. 6 is the principle analysis figure of nomography;

Fig. 7 is the analysis principle figure that nomography is applied to actual measurement;

Fig. 8 is the rectangular coordinate synoptic diagram of the embodiment of the invention.

Embodiment

As shown in Figure 8, embodiment of the invention process following steps:

A. generate rectangular coordinate by computer software, this rectangular coordinate is a horizontal ordinate with the angular difference δ (angular error) of voltage transformer (VT), and ratio f (proportional error) is an ordinate; Initial point " 0 " top be-U ,-f (%), the below is U, f (%), initial point " 0 " left be-jU ,-δ, right-hand be jU, δ, lights in the ratio mark of setting from former on the longitudinal axis, the initial point top marks ratio 0-0.3, marks ratio+0.3-0 below the initial point; On transverse axis with ratio be 0.29 length do angular difference 10 ' length, the unit of obtaining head is the angular difference scale on this basis; Described U is a voltage;

B. on coordinate axis, press power factor (PF)

The ratio f that records under the idle condition ₀, angular difference δ ₀Parameter, fix voltage transformer (VT) no-load error point A; By power factor

Nominal load S _nThe ratio f that records under the condition _N1.0, angular difference δ _N1.0Parameter, fix the error point B of voltage transformer (VT); Connect A, B 2 points, then in power factor

Under the condition, 0～100% rated load S _nThe margin of error be distributed on the vectorial AB;

C. being the center of circle with A, is that radius is drawn circle with number percent n% (0～100%) AB line segment, and this locus circle is n%S _nThe error profile track; With vectorial AB has been initial line, is starting point with the A point, (when load characteristic is perception) or counterclockwise (when load characteristic is capacitive) rotation in the clockwise direction (power factor angle) angle is drawn and the isometric line of AB, promptly obtains power factor (PF) The error profile track of (m=0～1.0).Can obtain at n%S by the intersection point of locus circle with this isometric line _n, power factor (PF)

Voltage transformer error point P under the condition; Make vertical projection to ordinate and horizontal ordinate respectively at error point P, can obtain at n%S _n, power factor (PF)

Voltage transformer (VT) ratio f under the condition _PWith angular difference δ _P

Below the principle of the inventive method is done following analysis:

One. utilize the theoretical derivation and the analysis of the on-the-spot calculating voltage transformer error of nomography

1.1 the notion of proportional error (ratio) and phase angle error (angular difference)

Fig. 1: tested voltage transformer (VT) output voltage U _x ^﹠amp;With the standard potential transformer output voltage U ₀ ^﹠amp;Differ a Δ U ^﹠amp;Amount, Δ U ^﹠amp;Can resolve into and output voltage U ₀ ^﹠amp;Δ U in the same way _f ^﹠amp;Quadrature Δ U with it _δ ^﹠amp;Two component of voltages.

Ratio

Angular difference

Ratio f and angular difference δ are relative errors, though δ represents that with minute (') it is the another kind of representation of relative error.

Suppose Δ U ^﹠amp;=1.4V

So

In the angular difference formula

Be that magnitude of voltage with quadrature component is converted into radian, as Fig. 2:

With with U ₀ ^﹠amp;Isometric line segment cuts a round part, one fan-shaped, mathematical knowledge is told us, and the angle corresponding with the isometric arc of radius is 1 radian, promptly 57.3 °, just 3438 ', we can know from sector diagram, the initial segment (very little) of camber line, and we can regard it as straight line, and it is vertical with radius, according to this theory, the corresponding length of camber line can replace the Δ U than small component _δ ^﹠amp;Length.This also is

Can multiply by 3438 ' theoretical foundation.

Along with Δ U _δ ^﹠amp;Increase, the error of δ value also will increase during formula calculates.Therefore, Δ U _δ ^﹠amp;Need the relational expression ability that δ calculates in small range accurate.In general the δ value be no more than 120 ' could be comparatively correct.

The error when 1.2 voltage transformer (VT) is unloaded

Error when voltage transformer (VT) is unloaded is to utilize nomography to calculate first parameter of carrying time error is arranged, and from the principle of voltage transformer (VT), we know that one time winding is connected to U ₁ ^﹠amp;Voltage, Secondary Winding just has U ₁ ^﹠amp;The secondary voltage of/N (multiplying power).But because excitatory loss.Secondary voltage is than desirable U ₁ ^﹠amp;/ N is little, in order to remedy this loss, often adopts the compensation way that increases the number of turn in Secondary Winding, and surpasses excitation loss.When so voltage transformer (VT) is unloaded ratio show slightly on the occasion of.But angular difference generally is a negative value, and this also is the feature of turn compensation.

According to formula

As seen, the secondary voltage after the compensation is converted primary voltage, is equivalent to primary voltage and has reduced by a Δ U on mathematics ₁ ^﹠amp;Voltage.(in 10/0.1 voltage transformer (VT), second compensation is equivalent to 100 volts of single compensations for 1 volt).

According to compensation principle, make Fig. 3.Bucking voltage Δ U ₁ ^﹠amp;, reduce exciting curent I at a winding ₀ ^﹠amp;', I ₀ ^﹠amp;' at R ₁Last minimizing loss of voltage U _OR ^﹠amp;, at X ₁Last minimizing loss of voltage U _OX ^﹠amp;, synthetic pressure drop U ₀ ^﹠amp;'.In figure (four), the error when we can calculate the voltage transformer (VT) zero load:

f ₀＝f _OR+f _OX；δ ₀＝δ _OR+δ _OX。

1.3 the error analysis during the voltage transformer (VT) bringing onto load

Error during the voltage transformer (VT) bringing onto load can be thought no-load error and the stack of the error when carrying is arranged.

After the error analysis of making light condition, we have the error analysis of carrying.

As Fig. 5, R ₂And X ₂Internal impedance for the voltage transformer secondary winding.It and the U when unloaded ₀ ^﹠amp;' difference, U ₀ ^﹠amp;' be increment, be consumption here.Load is S ₁,

The time load current at internal impedance R ₂And X ₂Last generation voltage drop U _2R ^﹠amp;And U _2X ^﹠amp;, synthetic pressure drop is U ₀₂ ^﹠amp;

In nomography, if power factor is constant, S increases or reduces, then U _2R ^﹠amp;, U _2X ^﹠amp;Synthetic pressure drop U ₀₂ ^﹠amp;Then correspondingly increase pro rata or reduce.If load S is constant, power factor is changed to 0.9,0.8,0.7,0.6,0.5 from 1.0 ..., all values are constant but phase place moves 25.8 ° respectively clockwise, and 36.9 °, 45.6 °, 53 ° and 60 ° ...Like this, we just can obtain the voltage transformer error distribution vector figure after load variations and the power factor change.Vector magnitude changes and phase angle change is distributed in the area of a circle (seeing figure (seven)).

1.4 the formation of nomography and making

As Fig. 6: with no-load voltage U ₀ ^﹠amp;' and U ₀₂ ^﹠amp;Stack make U ^﹠amp;' vector.

Make rectangular coordinate.Initial point " 0 " top be-U ,-f (%), the below is U, f (%), initial point " 0,, left be-jU ,-δ, right-hand be jU, δ, lights by the preset proportion mark from former on the longitudinal axis, the initial point top marks ratio 0-+0.3, marks ratio-0.3-0 below the initial point.On transverse axis with ratio be 0.29 length do angular difference 10 ' length, do cutting such as 10 branches such as grade then, the unit of getting head is angular difference 1 ' scale.From former light mark-10 of turning left ', mark+10 of turning right '.

We know the front

So pressure drop Δ U _f ^﹠amp;Be the function of ratio f, that is to say that ratio is the proportional quantities of pressure drop;

Angular difference also is the proportional quantities of pressure drop.The ratio f of mutual inductor and angular difference δ can form the plural error γ=f+j0.0291 δ of mutual inductor

When voltage transformer secondary voltage is 100V, $\mathrm{\&Delta;U}=\sqrt{{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="H2009102631411E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}^2+{\left(0.0291\mathrm{\&delta;}\right)}^2}---\left(V\right)$

So in coordinate diagram, initial point and error point promptly are similar to voltage drop Δ U with line than angular difference value perpendicular line intersection point ^﹠amp;

When doing the voltage transformer (VT) test, measure its no-load error f earlier ₀And δ ₀, be assumed to be 0.2 and-1 '.Measure again at nominal load S _nWith

Error f under the condition _N1.0And δ _N1.0, be assumed to be-0.3 and-5 '.

In rectangular plots, decide it respectively and be A point and B point.Connect A, B 2 points, vectorial U _AB ^﹠amp;Be the secondary voltage margin of error.It is unloaded over-compensation voltage U _0A ^﹠amp;Be S with load _n, power factor is 1 o'clock voltage transformer (VT) internal drop U _0B ^﹠amp;These two vectors are synthetic.

With the f that records ₀=+0.2, δ ₀=-1; f _N1.0=-0.35, δ _N1.0=-5.2 ' error parameter is made

S _n100%～S _nThe ratio of each corresponding point, angular difference contrast figure in 10% scope.

As Fig. 7, step:

1. make rectangular coordinate by preceding method;

2. on coordinate axis, press f ₀, δ ₀Parameter fix voltage transformer (VT) no-load error point A, press f _N1.0, δ _N1.0Parameter fix voltage transformer (VT) load S _nError point B during with power factor 1.0;

3. connect the AB voltage drop vector plot in the voltage transformer secondary winding that draws, vectorial AB is divided into 10 equal portions, mark 10% ~ 100%S _nEach point is the center of circle with A, is that radius is drawn circular arc with each number percent line segment.

4. being initial line with vectorial AB, is starting point with the A point, in the clockwise direction 25.8 °, and 36.8 °, 45.6 °, 53 °, 60 °, 66 °, 72 ° of pictures and the isometric line of AB, promptly

Be 0.9,0.8,0.7,0.6,0.5,0.4,0.3 pressure drop vector;

5. press voltage transformer (VT) actual load number percent and actual power factor, on corresponding power factor vector, determine the actual load point of voltage transformer (VT);

6. from load point to f axle, δ axial projection, can find your needed ratio, angular difference;

We can know from figure seven, and this voltage transformer (VT) all errors in 0～100% rated load, 0～1.0 power factor scope are distributed in the area of a circle of figure seven.We can calculate the actual motion error of this voltage transformer (VT) under arbitrary operating mode very easily.For example voltage transformer (VT) connects 90 ° of reactive energy-meters of internal phase angle, and load is 20%S _n, power factor is 0.3 o'clock, and can find out than difference respectively on f axle, δ axle from figure be+0.15, and the angular difference value is+2.2 ', and for example voltage transformer (VT) connects multi-function wrist-instrument, and load is 50%S _n, power factor is 0.9 o'clock, and can obtain it from figure is-0.08 than difference, and the angular difference value is 1.2 '.

1.5 the actual verification of nomography

When adopting said method that a transformer at scene is measured: can only measure the error f under nominal load S, power factor 0.8 condition under the field condition ₁₀₀And δ ₁₀₀And the error f under 25% nominal load S, power factor 0.8 condition ₂₅And δ ₂₅, and can't measure its no-load error.In order to draw no-load error f ₀And δ ₀, at this moment, can sum up the no-load error formula according to the principle of above argumentation, carry out no-load error with this formula and calculate, carry out nomography again.Formula is as follows:

$f_0=f_{100}-\frac{f_{100}-f_{25}}{75}\&CenterDot;(100-0)$

${\mathrm{\&delta;}}_0={\mathrm{\&delta;}}_{100}-\frac{{\mathrm{\&delta;}}_{100}-{\mathrm{\&delta;}}_{25}}{75}\&CenterDot;(100-0)$

Above-mentioned formula may extend to the ratio angular difference that calculates under the specified secondary load of arbitrary n%, as shown in the formula:

$f_n=f_{100}-\frac{f_{100}-f_{25}}{75}\&CenterDot;(100-n)$

${\mathrm{\&delta;}}_n={\mathrm{\&delta;}}_{100}-\frac{{\mathrm{\&delta;}}_{100}-{\mathrm{\&delta;}}_{25}}{75}\&CenterDot;(100-n)$

F in the formula _n---the ratio difference of the specified secondary load of n%

δ _n---the angular difference value of the specified secondary load of n%

f ₁₀₀---the ratio difference of specified secondary load

f ₂₅---the ratio difference of 25% specified secondary load

δ ₁₀₀---the angular difference value of specified secondary load

δ ₂₅---the angular difference value of 25% specified secondary load

Formula Parsing: ask the error of the specified secondary load of n%, with the error amount during 100% specified secondary load in the table, the margin of error when deducting (100-n) obtains.Unit number percent load residual quantity is

The unit residual quantity multiply by (100-n) and is the residual quantity that deducts.As ask the error f of 3% nominal load ₁₀₀(δ ₁₀₀) error deducts

Promptly deduct the error that 97% error residual quantity can obtain 3% nominal load.

To a model is JDZ-10, and rated load is 80VA, and class of accuracy is that 0.5 grade voltage transformer (VT) has carried out error testing in the laboratory with traditional method of testing and nomography respectively.Record its no-load error f ₀=0.410, δ ₀=2.4 '; 100% rated load (80VA), power factor are 1.0 error f _N1.0=-0.169, δ _N1.0=6.8 '.Measurement result sees Table one.

Table one nomography and conventional test methodologies are the contrast of each test point error under 0.8 condition in power factor

The error of calculating out by table one or two kind of method contrasts as can be known: the error information that nomography is calculated out is authentic and valid; And it is two groups of data of 1 time error that nomography only needs no-load point error and fully loaded, power factor, can calculate the error of other points, and the method utilization is simple, convenient, fast, can reduce the test duration effectively, reduces the danger prestige danger that may exist in the test; Can reduce in the measuring process other factors again to the interference of error, more accurate than conventional test methodologies; Conventional test methodologies is because of being subjected to the restriction of equipment such as load box, a lot of test points can't be measured error with the instrument simulation, the most outstanding is exactly on-the-spot actual error situation, nomography but can utilize two conventional error points easily to calculate the error point that conventional test methodologies can't be measured, and guarantees the accuracy of error.

Claims (1)

1. the method for a measuring error of voltage transformer by nomography, it is characterized in that: this method may further comprise the steps successively,

A. generate rectangular coordinate by computer software, this rectangular coordinate is a horizontal ordinate with the angular difference δ of voltage transformer (VT), and ratio f is an ordinate; Initial point " 0 " top be-U ,-f, the below is U, f, initial point " 0 " left be-jU ,-δ, right-hand be jU, δ, lights in the ratio mark of setting from former on the longitudinal axis, the initial point top marks ratio 0-0.3, marks ratio+0.3-0 below the initial point; On transverse axis with ratio be 0.29 length do angular difference 10 ' length, the unit of obtaining head is the angular difference scale on this basis; Described U is a voltage;

B. on coordinate axis, press power factor (PF)

The ratio f that records under the idle condition ₀, angular difference δ ₀Parameter, fix voltage transformer (VT) no-load error point A; By power factor Nominal load S _nThe ratio f that records under the condition _N1.0, angular difference δ _N1.0Parameter, fix the error point B of voltage transformer (VT); Connect A, B 2 points, then in power factor

Under the condition, 0～100% rated load S _nThe margin of error be distributed on the vectorial AB;

C. being the center of circle with A, is that radius is drawn circle with the AB line segment of number percent n%, and this locus circle is n%S _nThe error profile track; With vectorial AB has been initial line, is starting point with the A point, rotates in the clockwise direction or counterclockwise Angle is drawn and the isometric line of AB, promptly obtains power factor (PF) The error profile track; By the intersection point of locus circle, obtain at n%S with this isometric line _n, power factor (PF)

Voltage transformer error point P under the condition; Make vertical projection to ordinate and horizontal ordinate respectively at error point P, can obtain at n%S _n, power factor (PF)

Voltage transformer (VT) ratio f under the condition _PWith angular difference δ _P

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