KR100724094B1 - Evaluation method of linearity of error and phase angle error of voltage transformer comparative measurement system using capacitance - Google Patents

Abstract

The present invention relates to a method for evaluating linearity of non-error and phase angle error of a voltage transformer (VT) comparative measurement system using a capacitive burden. To this end, the same voltage is supplied to the primary side of the reference voltage transformer 40 and the voltage transformer 50 under measurement, and a voltage is formed between the secondary side of the reference voltage transformer 40 and the secondary side of the voltage transformer 50 under measurement. In the comparative measurement system of a voltage transformer in which a transformer comparison measuring device 60 is connected, and a capacitive load (Z _b ) 65 is connected in parallel to a secondary side of the voltage transformer 50 to be measured, the capacitance load X The linearity of the error error RE _b and the phase angle error Γ _b is evaluated by comparing the experimental values of the error and phase angle errors measured by varying _b ) with the theoretical values calculated from a predetermined equation.

Voltage transformer, comparator, phase angle error, non-error, linearity, primary side, secondary side

Description

Evaluation method of linearity of ratio error and phase angle error of voltage transformer comparison measurement system using capacitor burden}

1 is an equivalent circuit diagram of a voltage transformer at zero load,

2 is an equivalent circuit diagram of a voltage transformer when there is a burden Z _b ;

3 is a schematic diagram of a voltage transformer comparison measurement system;

In Figure 4a, 4b ● and □ are experimental results of measuring the variation of the error while changing the capacitance by using the conventional voltage transformer comparison measuring equipment of Company A and Company B, the straight line according to the present invention [ It is the result drawn using (12).

5a and 5b are the experimental results of measuring the change of the phase angle error while changing the capacitance load by using the conventional voltage transformer comparison measuring apparatus of Company A and Company B, the straight line according to the present invention It is the result drawn using [Equation 13].

<Description of main parts of drawing>

10: AC power supply,

20: primary side,

30: secondary side,

32: leakage output impedance of voltage transformer,

35: burden impedance,

40: reference voltage transformer,

50: voltage transformer to be measured,

60: voltage transformer comparison measuring device,

65: capacitive burden.

The present invention relates to a voltage transformer (VT), and more particularly, to a method for evaluating linearity of error and phase angle error of a voltage transformer comparative measurement system using a capacitive burden.

In general, an industry or a calibration laboratory that produces a voltage transformer uses a voltage transformer comparator (error measurement device) to evaluate or calibrate the characteristics of the voltage transformer. The error and phase of the voltage transformer to be measured are measured. Measure the phase angle error. The voltage transformer to be measured is divided into five classes, class 0.1, class 0.2, class 0.5, class 1, and class 3, depending on the class of error, and the allowable error is about ± 0.1% and ± 0.2, respectively. %, ± 0.5%, ± 1% and ± 3% or so.

The voltage transformer comparator shall be able to accurately measure the error to the aforementioned range. On the other hand, the voltage transformer comparator can measure the error of the voltage transformer under measurement with a small range of error relatively accurately.However, if the error measuring scale is slightly misaligned when measuring the voltage transformer under measurement with a large range of errors, Measurement is difficult and requires calibration. To this end, it is very important to evaluate whether the small-range error measurement value measured by the voltage transformer comparator maintains linearity even over a wide range, which is an important core technique of measuring device calibration.

Actual voltage transformers have leakage inductance and winding resistance on the primary and secondary sides, resulting in voltage drop and errors due to magnetization current and iron loss. The industry or calibration test institute producing voltage transformers uses the voltage transformer comparison measuring device (error measurement device) to evaluate or calibrate the characteristics of the voltage transformers. (phase angle error) is measured.

However, the conventional voltage transformer comparison measuring system is large and heavy and difficult to transport, and is frequently used for quality control and calibration testing of the product. Therefore, the device is transported to a calibration laboratory for evaluation (calibration). Is almost impossible.

For this reason, there is an urgent need for a method of evaluating a voltage transformer measuring device in the field by developing a mobile standard and bringing it to a business in order to evaluate an industrial voltage transformer comparison measuring system.

Accordingly, the present invention has been made in view of the above-described conventional problems, and a first object of the present invention is to transfer a small, light weight precision capacitance load to an industry so that a voltage transformer comparison measuring device can easily evaluate a measuring device in the field. It is to provide a linearity measuring device of.

The object of the present invention as described above, the same voltage is supplied to the primary side of the reference voltage transformer 40 and the voltage transformer under measurement 50,

A voltage transformer comparison measuring device 60 is connected between the secondary side of the reference voltage transformer 40 and the secondary side of the voltage transformer 50 under measurement,

In the comparative measurement system of the voltage transformer in which the capacitance side (Z _b ) 65 is connected in parallel to the secondary side of the voltage transformer 50 under measurement,

While changing the capacitive burden (X _b ) from the following equation, the rain error (RE _b ) is calculated,

Here, RE ₀ is a zero-load non-error, X ₀ is a constant as a reactance component of the leakage output impedance of the electrical transformer, characterized in that the linearity evaluation of the error of the voltage transformer comparative measurement system using a capacitance. Can be achieved by

The capacitive value of the burden can be 0.001 kPa to 1.1 kPa.

In addition, the voltage on the secondary side may be 30V to 120V.

As another embodiment of the present invention, the same voltage is supplied to the primary side of the reference voltage transformer 40 and the voltage transformer 50 under measurement,

A voltage transformer comparison measuring device 60 is connected between the secondary side of the reference voltage transformer 40 and the secondary side of the voltage transformer 50 to be measured.

In the comparative measurement system of the voltage transformer in which the capacitance side (Z _b ) 65 is connected in parallel to the secondary side of the voltage transformer 50 under measurement,

The phase angle error (Γ _b ) is calculated by varying the capacitive burden (X _b ) from the following equation,

Here, Γ ₀ is the phase angle error at zero load, and R ₀ is the linearity of the phase angle error of the voltage transformer comparative measurement system using a capacitive burden, characterized in that R ₀ is a constant as a resistance component of the leakage output impedance of the voltage transformer. The objective can also be achieved by the evaluation method.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings.

Hereinafter, an operation principle and a configuration of a method for evaluating the linearity of the error and phase angle error of the voltage transformer comparator measurement system using the capacitive burden according to the present invention will be described in detail with reference to the accompanying drawings.

First, the theoretical background of the burden effect of the error and phase angle error of the voltage transformer according to the present invention will be described below. 1 is an equivalent circuit diagram of a voltage transformer at zero load. In Fig. 1, Z _o is the leakage output impedance of the secondary side of the voltage transformer at zero load, and the complex ratios of the voltage vectors of the secondary side Vs and the primary side Vp of the voltage transformer are as follows.

Here, as the phase angle difference defined by Γ ₀ ≡Γ _s -Γ _p , the difference in phase angle between the primary side voltage vectors with respect to the secondary side rotated by 180 °, and N is the rated conversion ratio or winding ratio of the voltage transformer. RCF ₀ is the non-correction factor at zero load and is the actual ratio conversion factor of the voltage transformer. The relationship between the RCF and the RE is as follows.

2 is an equivalent circuit diagram of a voltage transformer when there is an external burden Z _b . As shown in FIG. 2, the complex ratio of the voltage vector of the primary side V _{p to the} secondary side V _b of the voltage transformer can be written as follows.

Here, Γ _b is the difference in phase angle of the primary voltage vector with respect to the secondary when there is an external burden (Z _b ) and RCF _b is an uncorrected factor when there is an external burden (Z _b ). In FIG. 2, since the current flowing through Z ₀ and Z _b is the same, it can be written as follows.

Then, Equation 4 can be rewritten as follows.

Therefore, [Equation 5] can be written as follows using [Equation 1] and [Equation 3].

In Equation 6, since Γ _b and Γ ₀ are about 10 ^-4 in size, more than the secondary term is ignored in the expansion of e ^-jΓb and e ^-jΓ0 . The leakage output impedance Z ₀ of the voltage transformer of Equation 6 can be written as follows.

In FIG. 2, the effect of the external load on the error and the phase angle error of the voltage transformer when the capacitor is connected as the external load will be described. The impedance (Z _b ) of the burden consisting of the capacitance connected to the secondary side of the voltage transformer can be said that R _b and X _b are connected in parallel.

Substituting [Equation 7] and [Equation 8] into [Equation 6] and rewriting it as follows.

Next, when the equation (9) is developed to take only the real part and there is an external burden (Z _b ), the non-correction factor (RCF _b ) is as follows.

At this time, the magnitude of Γ ₀ of the voltage transformer is about 10 ⁻⁴ . As the external load on the secondary side of the voltage transformer, select a mica standard capacitor with a rating of 1.1 kV, 1 kV, 0.1 kV, 0.01 kV, 0.001 kV. Since X _b = 1 / (2π · 60 · C) of the mica capacitors, it corresponds to 2.41 ㏀, 2.65 ㏀, 26.52 ㏀, 265.3 ㏀, 2.68 각각, respectively, and the loss coefficients of all capacitors are smaller than 10 ⁻⁴ , R _b is 24 kV or more. Therefore, since R _o / R _b , Γ ₀ X _O / R _b , and Γ ₀ R _O / X _b in [Equation 10] are small enough to be negligible within 10 ^-6 , the burden with capacitance is selected. do. Therefore, Equation 10 can be simply written as follows.

Using Equation 2, Equation 11 is converted into an equation for error, as follows.

On the other hand, when the equation (9) is developed and divided into imaginary parts and there is an external burden Z _b , the phase angle error Γ _b can be simply written as follows.

In Equation 13, Γ ₀ R _o / R _b , X _O / R _b , X _O ² / X _b R _b , X ₀ R ₀ / X _b ² , Γ ₀ X _o ² / X _b ² is Γ ₀ Compared with, it is less than 10 ^-6 times and can be ignored.

Here, since RE ₀ , R ₀ , Γ ₀ , and X ₀ are constants, the phase angle error (Γ) when there is a burden of error (RE _b ) and [Equation 13] when the burden of Equation 12 is applied. _b ) is inversely proportional to the value of the burden (ie, ˜1 / X _b ). That is, the linear error RE _b and the phase angle error Γ _b may be linear functions proportional to 1 / X _b . Therefore, when calculated as a function of 1 / X _b ratio error (RE _b) obtained going to change the value of the phase 1 / X _b in the angle error (Γ _b) for each formula 12] and [Equation 13] The linearity of the error (RE _b ) and the phase angle error (Γ _b ) can be evaluated.

3 is a configuration diagram of a voltage transformer comparison measurement system. As shown in FIG. 3, the same voltage is supplied to the primary side of the reference voltage transformer 40 and the voltage transformer under test 50. The secondary voltages of the two voltage transformers 40 and 50 are compared using the voltage transformer comparison measuring device 60. Here, the voltage transformer comparison measuring device 60 measures the error (RE _b ) and the phase angle error (Γ _b ), and compares the voltages of the secondary voltages of the two voltage transformers 40 and 50 with the error (RE _b ). The phase angle error (Γ _b ) is balanced to measure the error (RE _b ) and the phase angle error (Γ _b ) of the voltage transformer 50 under measurement.

In the voltage transformer comparator 60 owned by a domestic company, the variation ratio (RE _b ) of the voltage transformer to be measured was measured while changing the burden value (Z _b , 65) composed of the capacitive group. At this time, the measured voltage transformer 50 used was Model 2262 of Yokogawa, Japan, and was measured while maintaining the primary voltage at 3,300V and the secondary voltage at 110V.

In Figure 4a, 4b ● and □ are experimental results of measuring the variation of the error while changing the capacitance by using the conventional voltage transformer comparison measuring equipment of Company A and Company B, the straight line according to the present invention [ It is the result drawn using (12).

In FIG. 4, the models of the reference voltage transformer and the comparative measurement device of the company A are Knopp WP-14000-4 and Knopp KVTs, respectively. The company's reference voltage transformers and comparators are Tettex 4823 and Tettex 2767.

4A and 4B, the capacitance value of the burden is in the range of 0.001 ㎌ to 1.1 ㎌ (corresponding to 1 / X _b = 3.7 x 10 ^-7 Ω ^-1 to 4.2 x 10 ^-4 Ω ^-1 ). It can be seen that the difference between the experimental values (• and □) and the theoretical value (straight line) of the error coincide within 0.0005% (see graphs inserted in FIGS. 4A and 4B).

Another graph inserted in the graph of FIGS. 4A and 4B will be described. ΔRE _b = experimental value—theoretical value, and the theoretical value is calculated and displayed by [Equation 12]. Therefore, the linearity of the error is maintained very well within 0.0005%, so that the correction of the error is not necessary.

5a and 5b are the experimental results of measuring the change in the phase angle error while changing the capacitance load by using the conventional voltage transformer comparison measuring apparatus of Company A and Company B, the straight line according to the present invention It is the result drawn using [Equation 13].

As shown in Fig. 5, the load is phased in the range of the capacitance value from 0.001 ㎌ to 1.1 ㎌ (corresponding to 1 / X _b = 3.7 x 10 ^-7 Ω ^-1 to 4.2 x 10 ^-4 Ω ^-1 ). It can be seen that the difference between the experimental values? And? Of each error and the theoretical value (straight line) coincide within 0.00001 (see graphs inserted in FIGS. 5A and 5B).

Another graph inserted in the graph of FIGS. 5A and 5B will be described. ΔPAE _b = experimental value—theoretical value, and the theoretical value is calculated and displayed by [Equation 13]. Therefore, the linearity of the phase angle error is maintained very well within 0.00001, so that the correction of the phase angle error is not necessary.

In conclusion, it is possible to evaluate the linearity of the error and phase angle error of the voltage transformer comparator using the burden composed of the capacitance on the secondary side of the voltage transformer under measurement. That is, the present invention may be a new method of evaluating linearity by comparing the theoretical values obtained from the burden effects obtained in [Equation 12] and [Equation 13] with experimental results.

According to the method for evaluating the linearity of the error and phase angle error of the voltage transformer comparative measurement system using the capacitive burden according to the present invention described above, there is an advantage that the capacitive burden is light and easy to move.

In addition, according to the present invention, there is a versatility that can be commonly applied to all voltage transformers having various rating conversion ratios. Therefore, it will be well suited for evaluating and calibrating industrial voltage transformer comparative measuring devices later.

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 fall within the spirit of the invention.

Claims (6)

The same voltage is supplied to the primary side of the reference voltage transformer 40 and the voltage transformer 50 under measurement, A voltage transformer comparison measuring device 60 is connected between the secondary side of the reference voltage transformer 40 and the secondary side of the voltage transformer 50 under measurement, In the comparative measurement system of the voltage transformer in which the capacitance side (Z _b ) 65 is connected in parallel to the secondary side of the voltage transformer 50 under measurement, While changing the capacitive burden (X _b ) from the following equation, the rain error (RE _b ) is calculated,

Here, RE ₀ is the zero-error non-error, X ₀ is a constant as a reactance component of the leakage output impedance of the voltage transformer, The capacitive value of the burden is 0.001 ㎌ ~ 1.1 ㎌, and The voltage on the secondary side is 30 V ~ 120 V characterized in that the linearity evaluation of the error of the voltage transformer comparative measurement system using the capacitive burden. delete delete The same voltage is supplied to the primary side of the reference voltage transformer 40 and the voltage transformer 50 under measurement, A voltage transformer comparison measuring device 60 is connected between the secondary side of the reference voltage transformer 40 and the secondary side of the voltage transformer 50 under measurement, In the comparative measurement system of the voltage transformer in which the capacitance side (Z _b ) 65 is connected in parallel to the secondary side of the voltage transformer 50 under measurement, The phase angle error (Γ _b ) is calculated by varying the capacitive burden (X _b ) from the following equation,

Here, Γ ₀ is the phase angle error at zero load, R ₀ is a constant as a resistance component of the leakage output impedance of the voltage transformer, The capacitive value of the burden is 0.001 ㎌ ~ 1.1 ㎌, and The voltage of the secondary side having the fixed number of windings is 30 V ~ 120 V, the linearity evaluation method of the phase angle error of the voltage transformer comparison measurement system using a capacitive burden. delete delete

Images