KR20100039089A - Evaluation system and method to obtain ratio error and displacement error of current transformer - Google Patents

Abstract

PURPOSE: An evaluation system and a method to obtain ratio error and a displacement error of a current transformer are provided to improve the reliability by measuring a factor related to a ration error and a phase error of a current transformer. CONSTITUTION: A current transformer(30) to be measured supplies an identical current to a current supplied to a primary side of a reference current transformer. A current comparator(40) compares a secondary current of the reference current transformer and the current transformer to be measured and outputs a ratio error and a phase error. Load of the reference current transformer are serially connected to the secondary side of the reference current transformer.

Description

Evaluation system and method to obtain ratio error and displacement error of current transformer

The present invention relates to a method for evaluating the error and phase error of the current transformer, and more particularly, the factors (G _m , B _m , R ₂ , X ₂ ) affecting the error and phase error of the current transformer are independent. The present invention relates to a system for evaluating non-error and phase error of a current transformer capable of accurately evaluating a current transformer under measurement.

Current transformers (CTs) are used to accurately measure large currents. In order to accurately measure large currents, companies producing transformers or calibration laboratories use a current comparator to compare currents of the reference current transformer and the current transformer to be measured to determine or correct the characteristics of the current transformer. Evaluate.

The method of evaluating the current transformer is measured by comparing the secondary current of the current transformer to be measured with the secondary current of the reference current transformer which can ignore errors. In order for this evaluation method to have accuracy and reliability, it is necessary to accurately evaluate the error of the reference current transformer and to know the result of the evaluation. In addition, in order to evaluate the reference current transformer, it is necessary to evaluate the reference current transformer using an ultra-precision reference current transformer having an error of 0.005% or less, which is more accurate than the reference current transformer.

The conventional method of evaluating a current transformer has a problem that the process is complicated and that the current transformer can be absolutely dependent on the performance of the reference current transformer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a system for evaluating the error and phase error of a current transformer that does not depend on the performance of a reference current transformer, and a method of evaluating the same.

It is still another object of the present invention to evaluate the non-error and phase error of the current transformer and the evaluation system of the current transformer in which the measurement is simple and easy, and the current transformer can be easily evaluated in the field without having to move the current transformer to a standard engine. To provide a method.

An object of the present invention as described above includes a current transformer and a current transformer to be applied to the primary side the same current applied to the primary side of the reference current transformer and the reference current transformer,

A current comparator for comparing the secondary current of the reference current transformer and the current transformer to be measured and outputting a non-error and a phase error is provided.

On the secondary side of the reference current transformer, the burden for the reference current transformer is connected in series.

The secondary side of the current transformer to be measured is achievable by an evaluation system for the non-error and phase error of the current transformer, characterized in that a load for the current transformer to be measured is connected in series.

In addition, it is preferable to use a variable load for the current transformer to be measured.

인 것을 사용한다.In addition, the burden for the current transformer to be measured is resistance R, and the inductance component L of the resistance R is

I use that.

An object of the present invention as described above is a method for evaluating the error and phase error of the current transformer under measurement,

Measuring an excitation conductance and an excitation susceptance of the current transformer to be measured;

Measuring each component of the secondary leakage inductance of the current transformer to be measured; And

And obtaining a non-error and a phase error based on the excitation conductance, the excitation susceptance, and the secondary leakage inductance.

The error and the phase error can also be achieved by the method of evaluating the error and phase error of the current transformer, characterized in that based on Equations 10 and 11.

[Equation 10]

[Equation 11]

(Where G _m is the excitation conductance of the current transformer under measurement, B _m is the excitation susceptance of the current transformer under measurement, R ₂ is the secondary leakage resistance of the current transformer under measurement, and X ₂ is the secondary leakage of the current transformer under measurement). Reactance, R _b is the secondary burden resistance of the current transformer to be measured, X _b is

In this case, the secondary burden of the current transformer to be measured uses a variable resistor capable of ignoring the inductance component of the resistance, and the excitation and excitation susceptance measurement steps maintain a constant secondary current of the current transformer to be measured. By varying the variable resistance, the functional relationship between the error of the current transformer and the phase error of the current transformer according to the variable resistance can be obtained, and the excitation conductance and the excitation susceptance can be obtained based on the function relationship. have.

의 관계에 있는 것을 사용한다.At this time, the variable resistor has an inductance component L of the variable resistor with respect to the resistance value R of the variable resistor.

Use the one in relation to

In addition, in each component measurement step of the secondary leakage impedance of the current transformer to be measured, the leakage reactance of the secondary leakage impedance is ignored, the primary terminal of the current transformer to be measured is shorted, and then the resistance of the secondary terminal is measured. The resistance component of the secondary leakage impedance can be measured.

In the acquiring phase error and phase error, the extension uncertainty of the error may be 100 × 10 ^−6, and the expansion uncertainty of the phase error may be in the range of 128 × 10 ⁻⁶ .

Therefore, according to the evaluation system of the non-error and phase error of the current transformer according to the present invention and the evaluation method thereof, the factors related to the non-error and the phase error of the current transformer are independently measured, and thus do not depend on the performance of the reference current transformer. No, there is an advantage that the reliability is further increased.

In addition, since the evaluation method is simple, it is easy to evaluate in the field using the current transformer, the cost required for the evaluation is reduced, and the calibration period can be shortened.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to describing the present invention, if it is determined that the detailed description of related known functions and configurations may unnecessarily obscure the subject matter of the present invention, the description thereof will be omitted.

<Theory>

Prior to describing the evaluation system and the method of evaluating the error and phase error of the current transformer according to the present invention, the theoretical background of the error and phase error of the current transformer will be described.

The current transformer is an instrument transformer in which the current ratio is inversely proportional to the turns ratio and the phase of the secondary current is almost " 0 " compared to the phase of the primary current. The error and phase errors of these current transformers are specified not to exceed a certain value when the secondary load at the rated frequency is in the range of the rated load. FIG. 1 shows an equivalent circuit of a current transformer in case of a secondary burden Z _b . In FIG. 1, Z _m is the excitation impedance (Z _m = R _m + jX _m ), Z ₁ is the primary leakage impedance (Z ₁ = R ₁ + jX ₁ ), and Z ₂ is 2 Secondary leakage impedance (Z ₂ = R ₂ + jX ₂ ). And Z _b is the impedance of external burden (Z _b = R _b + jX _b ). In addition, I _p is the actual primary current, I _s is the ideal secondary current of the current transformer with no leakage and infinite excitation impedance, and I _b represents the actual secondary current when there is a secondary burden. I _m is the excitation current.

As mentioned above, the ratio of the current of the current transformer having no leakage current and infinite excitation impedance (Z _m ) is inversely proportional to the turns ratio, and thus may be represented by Equation 1.

In this case, N ₁ is the number of turns of the primary side of the current transformer, and N ₂ is the number of turns of the secondary side of the current transformer. And N is the rated winding ratio (or rated conversion ratio) of the current transformer.

The current vectors of the primary current I _p and the actual secondary current I _b flowing in the secondary burden of the current transformer may be represented by complex vectors as shown in [Equation 2] and [Equation 3], respectively.

와

는 각각 전류벡터 I_p와I_b의 크기이고,

와

는 각각 전류벡터 I_p와I_b의 위상이다. At this time,

Wow

Are the magnitudes of the current vectors I _p and I _b ,

Wow

Are the phases of the current vectors I _p and I _b , respectively.

The complex ratio of the primary current to the secondary current flowing through the secondary load of the current transformer is expressed by Equation 4 below.

는 전류변성기에 2차부담이 없는 경우의 전류변성기의 1차전류와 2차전류의 위상차이, 즉 위상오차(

)이다. 위상오차(

)는 2차전류의 위상이 1차전류의 위상보다 앞서는 경우 정(lead)이고, 2차전류의 위상이 1차전류의 위상보다 뒤지는 경우 부(lag)이다. RCF_b는 2차부담이 있을 때의 비 보정인자(Ratio Correction Factor)로 전류변성기의 실제 변환비(N_a)를 정격변환비(N)로 나눈 것으로서, 비오차(α_b)가 "0"인 이상적인 전류변성기의 비 보정인자(RCF_b)는 "1"이다. 비 보정인자(RCF_b)와 비오차(α_b)의 관계는 다음의 [수학식 5]와 같다.At this time,

Is the phase difference between the primary current and the secondary current of the current transformer when there is no secondary load in the current transformer.

)to be. Phase error

) Is positive when the phase of the secondary current is ahead of the phase of the primary current, and negative when the phase of the secondary current is behind the phase of the primary current. RCF _b is the ratio correction factor when there is a secondary burden, and the actual conversion ratio N _a of the current transformer is divided by the rated conversion ratio N, and the error ratio α _b is "0". The ratio correcting factor (RCF _b ) of the ideal current transformer is " 1 &quot;. The relationship between the non-correction factor (RCF _b ) and the error (α _b ) is shown in Equation 5 below.

, 즉

는 10^-3이하로 작은 값이다. 따라서, [수학식 4] 중

의 급수전개에서 2차항 이상과 α_bβ_b는 10^-6보다 작으므로 무시할 수 있는바, [수학식 4]는 [수학식 6]과 같이 나타낼 수 있다.In general, the current transformer uses a phase difference within 0.1%,

, In other words

Is a value less than 10 ⁻³ . Therefore, in [Equation 4]

Since the quadratic term and α _b β _b are smaller than 10 ⁻⁶ in the series of expansions, Equation 4 may be expressed as Equation 6.

In addition, the, secondary current (I _s) of the current transformer, as shown in Fig. 1 because it is the sum of the currents (I _b) flowing in the excitation current (I _m) and the secondary pressure as shown in [Equation 7].

And the voltage drop between the terminal a and the terminal b is the same. It can be expressed as shown in [Equation 8].

[Equation 1], [Equation 7] and [Equation 8] summarize the primary current (I _p ) with respect to the secondary current (I _b ) flowing through the secondary burden (Z _b ) of the current transformer. The relationship is shown in Equation 9 below.

When the secondary transformer (Z _b ) is present in the current transformer, the error (α _b ) and the phase error (β _b ) of the current transformer are compared between the real part and the imaginary part of Equations 6 and 9 These relations are as shown in [Equation 10] and [Equation 11], respectively.

,

이다.At this time, in [Equation 10] and [Equation 11], G _m is the excitation conductance, B _m is the excitation susceptance, respectively

,

to be.

Since the secondary burden (Z _b ) connected to the secondary side of the current transformer is easily measurable, measuring the G _m , B _m , R ₂ , and X ₂ , respectively, results in the amplification error (α _b ) and the phase error ( β _b ) can be evaluated.

Rain and Phase Error Evaluation System

2 is a configuration diagram of a system for evaluating the error and phase error of the current transformer according to the present invention. The system for estimating the non-error and phase error of the current transformer includes a current transformer 30, a large current generator 10, a reference current transformer 20, and a load 21 and 31 connected to each current transformer to be evaluated. Comparator 40 and the like.

The current transformer 30 and the reference current transformer 20 are connected in series, and the same current is applied to the primary sides of the current transformers 20 and 30 by the large current generator 10. The load is connected to the secondary side of the reference current transformer 20 and the secondary side of the current transformer 30 to be measured. In the present specification, the loads connected to the reference current transformer 20 and the current transformer 30 to be measured are referred to as a load 21 for the reference current transformer and a load 31 for the current transformer to be measured, respectively.

The secondary currents of the current transformer 30 and the reference current transformer 20 are evaluated by the current comparator 40 for the non-error and phase error of the current transformer 30 to be measured.

)할 수 있는 표준정밀저항을 사용한다. The burden 31 for the current transformer to be measured must be variable in order to measure the excitation conductance G _m and the excitation susceptance B _m . The load 31 for the current transformer to be measured uses an impedance having a resistance and an inductive reactance, and more preferably ignores the inductance component of the inductive reactance (

Use standard precision resistors.

The load 21 for the reference current transformer may use a fixed or variable impedance, and any value may be used.

<Evaluation of Rain and Phase Errors>

3 is a flowchart illustrating a method of evaluating the error and phase error of the current transformer according to the present invention. As described above, the non-error and phase error of the current transformer 30 to be evaluated for the non-error and phase error are excitation conductance (G _m ), excitation susceptance (B _m ), and secondary leakage resistance (R). ₂ ) and by measuring the secondary leakage reactance (X ₂ ), respectively. The method for evaluating the non-error and phase error of the current transformer according to the present invention is large, measuring the excitation conductance (G _m ) and excitation susceptance (B _m ) of the current transformer 30 to be measured (S100) and the measured object Measuring the secondary leakage impedance (R ₂ , X ₂ ) of the current transformer 30 (S200) and the step of estimating the non-error and phase error based on these four factors (S300).

(Measuring method of G _m and B _m )

의 관계에 있는 경우가 있다. 따라서, 피측정전류변성기용 부담(Z_b)은 Z_b=R_b의 관계를 갖는다.First, when there is a burden 31 for the current transformer to be measured, the step S100 of measuring the excitation conductance G _m and the excitation susceptance B _m will be described. In this step, a variable impedance is used as the load 31 for the current transformer to be measured, and more preferably, a standard precision resistor capable of disregarding the inductance component of the resistance (that is, X _b = 0) can be used. As an example of ignoring the inductance component of the resistance, as mentioned above, the relationship between the resistance component of the impedance and the inductance component

You may be in a relationship. Therefore, the burden Z _b for the current transformer to be measured has a relationship of Z _b = R _b .

At this time, if the secondary current I _b of the current transformer 30 to be measured is constant, the excitation conductance G _m , the excitation susceptance B _m , the secondary leakage resistance R ₂ , and the secondary leakage Reactance (X ₂ ) is constant. Therefore, Equation 10 and Equation 11 described above may be represented by Equation 12 and Equation 13 below.

Therefore, in this step (S100) of measuring the excitation conductance (G _m ) and the excitation susceptance (B _m ), firstly, the secondary current of the current transformer 30 to be measured in the non-error and phase error evaluation system of the current transformer is measured. While keeping I _b ) constant, the resistance R _b , which is the burden 31 for the current transformer to be measured, is changed (S110). In this case, equations (12) and (13) for the non-error and phase error are expressed as a function of the resistance R _{b which} is the load 31 for the current transformer to be measured. At this time, the slope of each function is -G _m and B _m , respectively. Therefore, while maintaining the secondary current I _b of the current transformer 30 under measurement and changing the resistance R _b of the load 31 for the current transformer under measurement, Equations 12 and 13 Values for the non-error (α _b1 ) and the phase error (β _b1 ) expressed as a function of] are obtained (S120). Excitation conductance (G _m ) and excitation susceptance (B _m ) can be obtained from the value (S130). The values for the aberration (α _b1 ) and the phase error (β _b1 ) obtained at this time are only numerical values at the stage for obtaining the woman conductance (G _m ) and the excitation susceptance (B _m ). According to the evaluation method according to the evaluation method, the error (α _b ) and the phase error (β _b ) of the current transformer 30 to be ultimately determined are different values.

The excitation conductance (G _m ) and excitation susceptance (B _m ) obtained in this way are values independent of the error of the reference current transformer 20, and thus, the error (α _b ) and phase error ( Since the evaluation method of β _b ) does not depend on the performance of the reference current transformer 20, the reliability is increased.

(Measurement method of R ₂ and X ₂ )

Next, in step S200 of measuring each component R ₂ and X ₂ of the secondary leakage impedance of the current transformer 30 to be measured, more preferably, the secondary leakage resistance of the current transformer 30 to be measured ( The steps of measuring R ₂ ) are explained. The secondary leakage resistance R ₂ of the current transformer 30 under measurement is obtained by shorting the primary terminal and measuring the resistance of the secondary terminal. Measurements can be made using a multimeter.

이다. 여기서, X_tot은 다음의 [수학식 14]와 같다.On the other hand, since the primary leakage impedance Z ₁ and the secondary leakage impedance Z ₂ of the current transformer 30 to be measured are difficult to measure, respectively, the total leakage impedance Z _tot is measured. The total leakage impedance (Z _tot ) is obtained by shorting the primary terminal and measuring the input impedance of the secondary terminal. In this case, the overall impedance is

to be. Here, X _tot is represented by the following [Equation 14].

At this time, L ₁ and L ₂ are the primary leakage inductance and the secondary leakage inductance, respectively, and N is the rated conversion ratio. At this time, if the secondary winding of the current transformer 30 is wound close to the coil in a single layer, the secondary leakage inductance L ₂ of the current transformer is very small compared to the primary leakage inductance L ₁ , and thus secondary leakage. The reactance (X ₂ ) can be ignored. Therefore, it is only necessary to measure the secondary leakage resistance R ₂ of the current transformer 30 to be measured.

Excitation conductance (G _m ), excitation susceptance (B _m ) and secondary leakage resistance (R ₂ ) of the current transformer (30) of the current transformer (30) obtained in each step described above can be expressed as 10] and (11), the error (α _b ) and the phase error (β _b ) of the current transformer 30 to be measured can be obtained (S300).

Hereinafter, an embodiment according to an evaluation method of the current transformer non-error and phase error according to the present invention will be described.

(First embodiment)

In the present embodiment, the primary current I _p of the current transformer 30 to be measured is 30 to 1500 [A], the secondary current I _b is 5 [A], and the burden for the current transformer to be measured 31 The standard precision resistance value of Z _b ) was used in the range of 0.01 to 1 [kV].

To obtain a woman transconductance (G _m) and women susceptance woman transconductance (G _m) and women susceptance (B _m) by the measurement step (S100) of (B _m) of the measured current transformer (30). When the secondary current I _b of the current transformer 30 to be measured at the tap having the current ratio of the current transformer 30 to 100A / 5A is 0.5 [A] and 5 [A], respectively, The error error α _b1 and the phase error β _b1 are the same as the graphs shown in FIGS. 4 and 5. 4 and Fig solid line in the 5 graph when the secondary current (I _b) of the measurement current transformer (30) of 5 [A], the dotted line is the secondary current of the measured current transformer 30 (I _b ) Is 0.5 [A].

If the secondary current I _b of the current transformer 30 to be measured is kept constant at 0.5 [A] and measured while changing the standard precision resistance which is the secondary burden 31 (Z _b ), the slope of FIG. The corresponding excitation conductance G _m is 1.07 × 10 ⁻³ [S], and the excitation susceptance B _m corresponding to the slope of FIG. 5 obtains a value corresponding to 1.39 × 10 ⁻³ [S]. In addition, when the secondary current I _b of the current transformer to be measured is 5 [A] and measured while changing the standard precision resistance of the secondary burden Z _b , the excitation conductance G corresponding to the slope of FIG. 4 is measured. _m ) is 0.99 × 10 ⁻³ [S] and the excitation susceptance B _m corresponding to the slope of FIG. 5 obtains 0.90 × 10 ⁻³ [S].

In this way, the current ratio of the current transformer 30 to be measured was also measured in the case of taps of 30A / 5A, 500A / 5A, 750A / 5A, 1500A / 5A, and the secondary of the current transformer 30 to be measured using multimedia. Leakage resistance (R ₂ ) was measured (S200). The results are as shown in the following [Table 1].

Current ratio (A / A) Secondary Current (%) Women's Admittance (S) Secondary leakage resistance R ₂ (Ω) G _m (× 10 ^-3 ) B _m (× 10 ^-3 ) 30/5 10 1.27 1.38 0.25 100 0.95 0.78 0.25 100/5 10 1.12 1.38 0.25 100 1.02 0.85 0.25 500/5 10 1.10 1.43 0.25 100 0.94 0.80 0.25 750/5 10 1.04 1.32 0.25 100 0.94 0.83 0.25 1500/5 10 1.01 1.38 0.25 100 0.94 0.87 0.25

Based on the values of each component of the excitation admittance as a result of [Table 1], the secondary leakage resistance value, and [Equation 10] and [Equation 11], the burden (31: Z _b ) for the current transformer to be measured is 0. The error (α _o ) and the phase error (β _o ) of the case (R _b = 0, X _b = 0) were calculated (S300). The results are shown in the following [Table 2], and also compared with the results according to the evaluation method of the rain error and phase error according to the present invention, also shown with the results measured by the Canadian National Standards Institute (NRC) .

Current ratio (A / A) Secondary Current (%) Result of the Invention NRC measurements Difference α _o (%) β _o (crad) α _o (%) β _o (crad) Δα _o (%) Δβ _o (crad) 30/5 10 -0.0322 0.0348 -0.0200 0.0400 0.0122 0.0052 100 -0.0242 0.0197 -0.0200 0.0200 0.0042 0.0003 100/5 10 -0.0285 0.0350 -0.0200 0.0500 0.0085 0.0150 100 -0.0259 0.0215 -0.0200 0.0200 0.0059 -0.0015 500/5 10 -0.0279 0.0363 -0.0500 0.0600 -0.0221 0.0237 100 -0.0238 0.0202 -0.0200 0.0300 0.0038 0.0098 750/5 10 -0.0262 0.0334 -0.0500 0.0600 -0.0238 0.0266 100 -0.0239 0.0209 -0.0200 0.0200 0.0039 -0.0009 1500/5 10 -0.0255 0.0348 -0.0500 0.0600 -0.0245 0.0252 100 -0.0239 0.0219 -0.0200 0.0200 0.0039 -0.0019

The result according to the present invention is 0.0038 to 0.0245% for the difference (α _o ) and 0.0003 to 0.0266crad for the phase error (β _o ). For all ranges of current, the error (α _o ) and the phase error (β _o ) can be confirmed to coincide within each expansion uncertainty.

At this time, the expansion uncertainty (when k = 2) of the error for the current transformer 30 under measurement according to the present invention is 100 × 10 ^{−6 in} the case of the error (α _o ) including the parameter modeling error, and the phase The error β _o is 128 × 10 ⁻⁶ [rad]. And, Canada (in the case of k = 2) national standards bodies expand uncertainty of measurement error in the case of the error ratio is 200 × 10 ^-6 case of (α _o), the phase error ^{_{(β o) 200 × 10 -6}} [ rad]. Where k is the effective degree of freedom and the extended uncertainty is defined as the product of the effective degree of freedom and the combined uncertainty.

(Second Embodiment)

In this embodiment, the primary current I _p of the current transformer 30 to be measured is 5 to 5000 [A], the secondary current I _b is 1 [A], and the burden for the current transformer to be measured 31 The standard precision resistance value of Z _b ) was 0.1 to 10 [Ω].

According to each current ratio, the values of the excitation admittance components (G _m , B _m ) and the secondary leakage resistance (R ₂ ) measured by the above-described evaluation methods (S100, S200) are shown in the following [Table 3]. As shown in

Current ratio (A / A) Secondary Current (%) Women's Admittance (S) Secondary leakage resistance R ₂ (Ω) G _m (× 10 ^-6 ) B _m (× 10 ^-6 )   5/1 5 1.39 -1.30 3.25 10 1.33 -1.25 3.25 20 1.17 -1.28 3.25 50 1.22 -1.37 3.25 100 1.35 -1.16 3.25   10/1 5 0.88 -1.10 3.25 10 0.98 -0.75 3.25 20 0.87 -0.81 3.25 50 0.85 -0.79 3.25 100 0.96 -0.72 3.25   100/1 5 0.64 -1.06 3.20 10 0.72 -0.93 3.20 20 0.64 -0.84 3.20 50 0.66 -0.91 3.20 100 0.75 -0.92 3.20   1000/1 5 0.76 -0.17 3.20 10 0.77 0.09 3.20 20 0.72 0.03 3.20 50 0.77 0.01 3.20 100 0.86 0.39 3.20   5000/1 5 0.67 -0.47 3.15 10 0.66 -0.31 3.15 20 0.60 -0.40 3.15 50 0.57 -0.39 3.15 100 0.65 -0.38 3.15

Based on the values of the excitation admittance components (G _m and B _m ), the secondary winding resistance (R ₂ ), and [Equation 10] and [Equation 11], which are the results of Table 3, _b ) and the phase error β _b were calculated (S300). In this case, the aberration (α _b ) and the phase error (β _b ) are cases in which the burden for the current transformer (31: Z _b ) exists, and the value thereof is R _b = 0.2 [Ω], and X _b = 0. The error (α _b ) and the phase error (β _b ) according to the present embodiment are as shown in the following [Table 4], and the evaluation of the error (α _b ) and the phase error (β _b ) according to the present invention. For comparison with the results of the method, the results obtained by the Canadian National Standards Institute (NRC) are also shown.

Current value (A / A) Secondary Current (%) Result of the Invention NRC measurements Difference α _b (%) β _b (crad) α _b (%) β _b (crad) Δα _b (%) Δβ _b (crad)   5/1 5 -0.0005 -0.0004 -0.0004 -0.0006 0.0001 -0.0002 10 -0.0005 -0.0004 -0.0006 -0.0007 -0.0002 -0.0003 20 -0.0004 -0.0004 -0.0007 -0.0008 -0.0003 -0.0003 50 -0.0004 -0.0005 -0.0007 -0.0009 -0.0003 -0.0004 100 -0.0005 -0.0004 -0.0007 -0.0010 -0.0002 -0.0006   10/1 5 -0.0003 -0.0004 -0.0005 0.0007 -0.0002 0.0011 10 -0.0003 -0.0003 -0.0005 0.0007 -0.0002 0.0010 20 -0.0003 -0.0003 -0.0005 0.0006 -0.0002 0.0009 50 -0.0003 -0.0003 -0.0005 0.0006 -0.0002 0.0009 100 -0.0003 -0.0002 -0.0005 0.0006 -0.0002 0.0009   100/1 5 -0.0002 -0.0004 -0.0003 0.0010 -0.0001 0.0013 10 -0.0002 -0.0003 -0.0003 0.0010 -0.0001 0.0013 20 -0.0002 -0.0003 -0.0003 0.0010 -0.0001 0.0013 50 -0.0002 -0.0003 -0.0003 0.0009 -0.0001 0.0012 100 -0.0003 -0.0003 -0.0003 0.0009 0.0000 0.0012   1000/1 5 -0.0003 -0.0001 0.0002 0.0006 0.0005 0.0007 10 -0.0003 0.0000 0.0002 0.0006 0.0005 0.0006 20 -0.0002 0.0000 0.0002 0.0005 0.0005 0.0005 50 -0.0003 0.0000 0.0002 0.0005 0.0005 0.0005 100 -0.0003 0.0001 0.0001 0.0005 0.0004 0.0004   5000/1 5 -0.0002 -0.0002 0.0027 0.0005 0.0029 0.0007 10 -0.0002 -0.0001 0.0025 0.0006 0.0027 0.0007 20 -0.0002 -0.0001 0.0022 0.0007 0.0024 0.0008 50 -0.0002 -0.0001 0.0017 0.0008 0.0019 0.0009 100 -0.0002 -0.0001 0.0015 0.0007 0.0017 0.0008

The result according to the present invention is 0.0000 to 0.0029% for the difference (α _b ) and 0.0000 to 0.0013 crad for the phase error (β _b ). In addition, similarly to the first embodiment described above, it can be seen that for all current ranges, the error error α _b and the phase error β _b coincide within each expansion uncertainty.

At this time, the expansion uncertainty (when k = 2) of the error for the current transformer 30 under measurement according to the present invention is 20 × 10 ^{−6 in} the case of the error (α _b ) including the parameter modeling error, and the phase The error β _b is 20 × 10 ⁻⁶ [rad]. And, Canadian National (in the case of k = 2) standards body, expand the uncertainty of the measurement error in the case of 20 × 10 ^-6, and the phase error (β _b) For a non-error ^{_{(α b) 20 × 10 -6}} [ rad].

(Third Embodiment)

In this embodiment, the primary current I _p of the current transformer 30 to be measured is 5 to 5000 [A], the secondary current I _b is 5 [A], and the burden for the current transformer to be measured 31 The standard precision resistance value of Z _b ) was used in the range of 0.01 to 1 [kV].

According to each current ratio, the values of the excitation admittance components (G _m , B _m ) and the secondary leakage resistance (R ₂ ) measured by the evaluation methods (S100, S200) described above are shown in [Table 5]. As shown in

Current ratio (A / A) Secondary Current (%) Women's Admittance (S) Secondary leakage resistance R ₂ (Ω) G _m (× 10 ^-6 ) B _m (× 10 ^-6 )   5/5 5 12.53 -7.81 0.50 10 13.50 -8.55 0.50 20 13.40 -9.44 0.50 50 14.20 -10.14 0.50 100 15.03 -9.30 0.50   10/5 5 5.38 4.74 0.70 10 5.97 4.36 0.70 20 5.92 4.16 0.70 50 6.01 4.04 0.70 100 6.14 5.45 0.70   50/5 5 4.31 3.97 0.46 10 4.08 4.38 0.46 20 4.52 4.45 0.46 50 4.79 4.72 0.46 100 5.22 5.43 0.46   100/5 5 2.40 1.62 0.11 10 2.19 1.40 0.11 20 2.28 1.72 0.11 50 2.17 1.63 0.11 100 2.27 2.13 0.11   500/5 5 2.65 1.46 0.10 10 2.43 1.60 0.10 20 1.74 1.52 0.10 50 2.40 1.72 0.10 100 2.12 1.81 0.10   1000/5 5 4.79 4.45 0.45 10 4.17 3.64 0.45 20 4.36 4.37 0.45 50 4.74 4.01 0.45 100 4.96 4.35 0.45   5000/5 5 1.39 0.72 0.65 10 1.54 0.78 0.65 20 1.05 0.81 0.65 50 1.05 0.90 0.65 100 1.43 1.31 0.65

Based on the values of the excitation admittance components (G _m , B _m ), the second leakage resistance (R ₂ ), and [Equation 10] and [Equation 11], which are the results of Table 5, _b ) and the phase error β _b were calculated (S300). In this case, the burden 31 for the current transformer to be measured exists, and the value thereof is R _b = 0.2 [kV] and X _b == 0. The results of the aberration (α _b ) and the phase error (β _b ) are as shown in the following [Table 6], and according to the evaluation method of the aberration (α _b ) and the phase error (β _b ) according to the present invention. For comparison with the results, the results obtained by the Canadian National Standards Institute (NRC) are also shown.

Current value (A / A) Secondary Current (%) Result of the Invention NRC measurements Difference α _b (%) β _b (crad) α _b (%) β _b (crad) Δα _b (%) Δβ _b (crad)   5/5 5 -0.0009 -0.0005 -0.0003 -0.0012 0.0006 -0.0007 10 -0.0009 -0.0006 -0.0003 -0.0013 0.0006 -0.0007 20 -0.0009 -0.0007 -0.0004 -0.0013 0.0005 -0.0006 50 -0.0010 -0.0007 -0.0004 -0.0014 0.0006 -0.0007 100 -0.0011 -0.0007 -0.0004 -0.0015 0.0007 -0.0008   10/5 5 -0.0005 0.0004 -0.0002 -0.0001 0.0003 -0.0003 10 -0.0005 0.0004 -0.0002 0.0000 0.0003 -0.0004 20 -0.0005 0.0004 -0.0003 0.0000 0.0002 -0.0004 50 -0.0005 0.0004 -0.0003 0.0000 0.0002 -0.0004 100 -0.0006 0.0005 -0.0003 0.0000 0.0003 -0.0005   50/5 5 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000 10 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000 20 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000 50 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000 100 -0.0003 0.0004 -0.0002 0.0003 0.0001 -0.0001   100/5 5 -0.0001 0.0000 -0.0001 0.0003 0.0000 0.0003 10 -0.0001 0.0000 -0.0001 0.0003 0.0000 0.0003 20 -0.0001 0.0001 -0.0001 0.0003 0.0000 0.0002 50 -0.0001 0.0001 -0.0001 0.0003 0.0000 0.0002 100 -0.0001 0.0001 -0.0001 0.0003 0.0000 0.0002   500/5 5 -0.0001 0.0000 -0.0002 0.0003 -0.0001 0.0003 10 -0.0001 0.0000 -0.0002 0.0003 -0.0001 0.0003 20 -0.0001 0.0000 -0.0002 0.0003 -0.0001 0.0003 50 -0.0001 0.0001 -0.0002 0.0003 -0.0001 0.0002 100 -0.0001 0.0001 -0.0002 0.0003 -0.0001 0.0002   1000/5 5 -0.0003 0.0003 -0.0001 0.0003 0.0002 0.0000 10 -0.0003 0.0002 -0.0002 0.0003 0.0001 0.0001 20 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000 50 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000 100 -0.0003 0.0003 -0.0002 0.0003 0.0001 0.0000   5000/5 5 -0.0001 0.0001 -0.0001 -0.0001 0.0000 -0.0002 10 -0.0001 0.0001 -0.0001 -0.0001 0.0000 -0.0002 20 -0.0001 0.0001 -0.0001 -0.0001 0.0000 -0.0002 50 -0.0001 0.0001 -0.0001 0.0000 0.0000 -0.0001 100 -0.0001 0.0001 -0.0001 0.0000 0.0000 -0.0001

The result according to the present invention is 0.0000 to 0.0007 for the difference (α _b ) and 0.0000 to 0.0008 crad for the phase error (β _b ). In addition, similarly to the second embodiment described above, it can be confirmed that for all current ranges, the error (α _b ) and the phase error (β _b ) coincide within each of the extended uncertainties.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will cover such modifications and variations as long as they fall within the spirit of the invention.

The following drawings, which are attached in this specification, illustrate the preferred embodiments of the present invention, and together with the detailed description thereof, serve to further understand the technical spirit of the present invention, and therefore, the present invention is limited only to the matters described in the drawings. It should not be interpreted.

1 is an equivalent circuit diagram when there is a secondary burden on a current transformer;

2 is a configuration diagram of a system for estimating non-error and phase error of a current transformer according to the present invention;

3 is a flowchart according to a method for evaluating non-error and phase error of a current transformer according to the present invention;

FIG. 4 is a graph showing a relationship between non-errors according to secondary burdens of secondary currents I _b of the current transformer to be measured according to the first embodiment of the present invention.

FIG. 5 is a graph showing a relationship between phase errors according to secondary burdens of secondary currents I _b of the current transformer to be measured according to the first embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: large current generator

20: reference current transformer

21: Burden for reference current transformer

30: current transformer to be measured

31: Burden for current transformer to be measured

40: current comparator

Claims (8)

A reference current transformer and a current transformer to be supplied with the same current as that applied to the primary side of the reference current transformer to the primary side, A current comparator for comparing the secondary currents of the reference current transformer and the current transformer to be measured and outputting a non-error and a phase error, The burden for the reference current transformer is connected in series to the secondary side of the reference current transformer, And a secondary error of the current transformer, in which a load for the current transformer under measurement is connected in series. The method of claim 1, The system for evaluating the non-error and phase error of the current transformer, characterized in that the burden for the current transformer to be measured is variable. The method according to claim 1 or 2, The burden for the current transformer to be measured is the resistance (R), The inductance component L of the resistor R is

A method for evaluating the non-error and phase error of the current transformer, characterized in that. As a method of evaluating the error and phase error of the current transformer under measurement, Measuring an excitation conductance and an excitation susceptance of the current transformer to be measured; Measuring each component of the secondary leakage inductance of the current transformer to be measured; And And obtaining a non-error and a phase error based on the excitation conductance, the excitation susceptance, and the secondary leakage inductance. The error and the phase error is an evaluation method of the error and the phase error of the current transformer, characterized in that based on [Equation 10] and [Equation 11]. [Equation 10]

[Equation 11]

(Where G _m is the excitation conductance of the current transformer under measurement, B _m is the excitation susceptance of the current transformer under measurement, R ₂ is the secondary leakage resistance of the current transformer under measurement, and X ₂ is the secondary leakage of the current transformer under measurement). Reactance, R _b is the secondary load resistance of the current transformer under measurement, X _b is the secondary load of the current transformer under measurement) The method of claim 4, wherein The secondary burden of the current transformer to be measured uses a variable resistor that can ignore the inductance component of the resistance, and The excitation conductance and excitation susceptance measurement step, The secondary current of the current transformer to be measured is kept constant, and the respective functional relations of the non-error of the current transformer and the phase error of the current transformer according to the variable resistance are obtained while changing the variable resistance. And estimating the excitation conductance and the excitation susceptance on the basis of the functional relationship. The method of claim 5, The variable resistance is, The inductance component L of the variable resistor is equal to the resistance value R of the variable resistor.

A method for evaluating the non-error and phase error of the current transformer, characterized in that the relationship between. The method according to claim 4 or 5, In each component measurement step of the secondary leakage impedance of the current transformer to be measured, Ignore the leakage reactance of the secondary leakage impedance, And measuring the resistance component of the secondary leakage impedance by shorting the primary terminal of the current transformer to be measured and measuring the resistance of the secondary terminal. The method of claim 4, wherein In the step of acquiring the non-error and phase error, The uncertainty of expansion of the error is 100 × 10 ⁻⁶ , And the uncertainty of expansion of the phase error is 128 × 10 ⁻⁶ .

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