JPH10124155A - Primary voltage detecting method for transformer, and its apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect primary side voltage lowering and a system voltage lowering phenomenon without the arrangement of PT, etc., on the transformer primary side by calculating the primary side voltage of a transformer through the use of a winding impedance, etc., corresponding to the detected secondary side voltage of the transformer, the current and the tap position signal. SOLUTION: Voltage V2 detected in the secondary side of the transformer, current I2 and the position signal from a tap change-over controller are respectively inputted to a bank primary voltage arithmetic part 12. The winding ratio at every tap position and the table of the impedance are previously prepared in a constant selecting part 21 inside the arithmetic part 12 and the inputted tap position signal refers to the table so as to select the winding wire ratio Nr and the winding wire impedance Zr corresponding to the position signal. A V1 -arithmetic circuit 27 obtains the primary side voltage V1 of the transformer through the use of the arithmetic equation by an arithmetic result which is corrected by a gain correction processing part 26 and the constants.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a primary voltage from a secondary voltage, current, etc. of a transformer in a substation or the like having no voltage detector on the primary side of the transformer.

[0002]

2. Description of the Related Art An electric power system is configured as shown in FIG. In order to maintain the voltage stability of this system, appropriate control of the phase adjustment equipment C and the tap of the transformer should be performed by catching the voltage drop phenomenon as shown in “4” → “8” in FIG. There is a need to do.

[0003] Conventionally, the detection of a voltage drop in a system is performed by taking in the primary voltage of a distribution substation detected by a PT (instrument transformer) or a PD (voltage detector).

[0004]

However, there are cases where no PT or PD is installed on the primary side of a transformer in a distribution substation. In such a substation, only the voltage on the secondary side of the transformer can be taken in. However, as shown in FIG. 5C, the voltage on the secondary side of the transformer is maintained constant by the voltage regulating relay 4, so that the secondary The voltage drop on the primary side of the transformer cannot be accurately determined only by the side voltage.

[0005] The present invention has been made in view of such a conventional problem, and an object of the present invention is to reduce the voltage drop on the primary side even if no PT or PD is installed on the primary side of the transformer. An object of the present invention is to provide a method and a device capable of detecting a system voltage drop phenomenon.

[0006]

According to a first aspect of the present invention, a secondary side voltage, a secondary side current and a tap position of a transformer having a tap switching device are detected, and a winding impedance and a winding impedance corresponding to the tap position are detected. The constant of the line ratio is stored in advance, and the following equation is obtained by using the detected secondary voltage V ₂ , current I _2, and winding position impedance Z _T corresponding to the tap position signal and the constant of the winding ratio _NT of the transformer. it is obtained to detect the primary voltage V ₁ of the transformer from the calculation.

[0007]

(Equation 2)

A second invention is directed to a device for detecting a secondary voltage, a secondary current, and a tap position of a transformer having a tap switching device, a winding impedance and a winding ratio constant corresponding to a tap position signal. In advance, and a constant selection unit that selects a constant corresponding to the detected tap position signal,
The detected analog voltage value / current value is converted into a digital signal, and the converted voltage / current digital value V ₂ , I ₂
The used a first arithmetic unit that are computing the V _{² 2,} I _{2 2} and V ₂ · I ₂ sinθ Based calculated value and the winding impedance constant determined by the calculation unit, the turn ratio constant a second calculator for calculating a primary voltage V ₁ of the transformer, in which a voltage drop detector for detecting a primary voltage drop in the transformer from the voltages V ₁ obtained by this calculation.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a configuration of a bank primary side voltage drop detection device according to a first embodiment. In FIG. 1, reference numeral 11 denotes a bank primary voltage drop width calculating means, which comprises a bank primary voltage calculator 12 and a voltage drop detector 13 which calculates the drop of the primary voltage by a voltage level judgment or a least square method.

As shown in FIG. 2, in this apparatus, the bank primary voltage V ₁ of the distribution substation is controlled by the bank secondary voltage V ₂ , the bank secondary current I _2, and the impedance depending on the tap position of the bank transformer TR. A high-precision operation is performed on the basis of Z _T and the winding ratio of each tap by the following operation algorithm, and the rate of change ΔV ₁ / ΔT of the voltage V ₁ is determined to detect a voltage drop on the primary side of the bank.

FIG. 3 shows an arithmetic circuit of the bank primary voltage calculation unit and an equivalent circuit of the bank transformer TR and a voltage vector. In the figure, N ₁ and N ₂ are primary and secondary windings of a transformer, V _2X is a secondary side induced voltage, Z _T is a winding impedance depending on a tap position of the transformer, and L is a load. The primary voltage from the equivalent circuit V ₁ and the secondary voltage V _2, relationship between the current I ₂ is represented by equation (1).

[0012]

(Equation 3)

[0013]

(Equation 4)

[0014]

(Equation 5)

However, * 1. For the values indicated by the double underline in the expressions (2) and (3), a setting table is prepared in advance, and a value corresponding to the tap position is selected from the setting table.

* 2. _{^{V 2 2, I 2 2,}} V 2 · I 2 cosθ, V
_{Since 2} · I ₂ · sin θ is affected by frequency fluctuation, gain correction is performed.

* 3. Since φ> 85 °, the calculation is simplified by setting φ = 90 °. → Z _T cos φ = 0 As shown in FIG. 4, the bank primary voltage calculation unit 12 includes a constant selection unit 21 for selecting a value corresponding to the tap position from the above-described settling table * 1, and a secondary side voltage V ₂ , an analog filter AF ₁ for extracting the basic value of the secondary current I ₂ , a converter A / D ₁ for converting the analog basic value voltage to a digital voltage, and an analog filter AF ₂ for extracting the basic value of the secondary current I _2.
When a transducer A / D ₂ for converting the analog base value current into a digital current, the voltage V ₂ than the converter A / D _1, and the frequency calculating unit 22 for determining the frequency for the above ※ 2 gain correction , arithmetic unit 2 for obtaining the V ₂ ² from the voltage V ₂
3, an arithmetic unit 24 for obtaining V ₂ · I ₂ sin θ from the voltage V ₁ and the current V _{2 of} the converters A / D ₁ and A / D ₂ , and the current I ₂
An arithmetic unit 25 for obtaining the I ₂ ² from these arithmetic unit 23-2
5, a gain correction processing unit 26 that corrects the calculation result from the calculation unit 22 with the frequency from the calculation unit 22, and V _{1 of the} equations (2) and (3) based on the corrected calculation result and the constant from the constant selection unit 21.
And a V ₁ arithmetic circuit 27. seeking.

As the configuration of the voltage drop detection unit, a configuration for determining the rate of change of voltage drop ΔV ₁ / ΔT using the least square method or the like, or a configuration for determining the level of the detected value itself can be considered.

Note that the gain of the signal input to each of the arithmetic units 23 to 25 fluctuates as the frequency fluctuates. The gain correction processing unit 26 corrects the calculation results of the calculation units 23 to 25 based on the input frequency obtained by the frequency calculation unit 22.

Next, the operation will be described.

The voltage V ₂ and current I ₂ detected on the secondary side of the transformer shown in FIG. 2 and the position signal from the tap switching control device (not shown) are input to the bank primary voltage calculator 12. Is done. In the constant selection unit 21 in the arithmetic unit 12, a table of the winding ratio and the impedance for each tap position is prepared in advance, and the input tap position signal refers to this table by referring to the constant corresponding to the position signal. to select the N _T and Z _T.

On the other hand, the voltage V ₂ is the analog filter AF ₁ ,
Via the converter A / D ₁ is input to the frequency calculating unit 22, V ₂ ² calculating unit 23 and the V ₂ · I ₂ sinθ calculation unit 24.
The current I ₂ passes through AF ₂ and A / D ₂ , and the I ₂ ²
And V ₂ · I ₂ sin θ, and the respective calculations are performed.

The output of the arithmetic unit 22 to 25 arithmetic processing based on the three expressions at V ₁ calculation unit 27 after the gain correction by the gain correction processing unit 26 has been issued.

[0024]

Since the present invention is configured as described above, the primary voltage can be accurately obtained from the transformer secondary side information and the transformer tap position.
There is no need to provide such a device, leading to cost reduction.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram according to a first embodiment.

FIG. 2 is a schematic explanatory diagram of voltage drop detection.

FIG. 3 is a transformer equivalent circuit and its voltage and current vector diagrams.

FIG. 4 is a block diagram of a bank primary voltage calculation.

FIG. 5 is a schematic explanatory diagram of voltage control and system voltage.

[Explanation of symbols]

11 ... Bank primary voltage drop width calculating means 12 ... Bank primary voltage calculating portion 13 ... voltage detection unit 15 to 17 ... voltage reduction width comparator 21 ... constant selecting section 22 ... frequency calculating unit 23 ... V ₂ ² calculating unit 24 ... V ₂ · I ₂ sinθ computing unit 25 ... I ₂ ² calculating unit 26 ... gain correction processing unit 27 ... V ₁ arithmetic unit

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Motomaru Nakazawa, 1-3-1, Uchisaiwai-cho, Chiyoda-ku, Tokyo Tokyo Electric Power Co., Inc. (72) Takahiro Nobata 1-3-1, Uchisaiwai-cho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Kenji Kubota 1-1-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Yuichi Nakao 1-1-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Inside Electric Power Company (72) Inventor Yoshitaka Sakai 2-1-117 Osaki, Shinagawa-ku, Tokyo Inside the Meidensha Corporation (72) Inventor Toshiro Fujimoto 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Inside the Meidensha Corporation

Claims (2)

[Claims] 1. A secondary voltage, a secondary current, and a tap position of a transformer having a tap switching device are detected, and a winding impedance and a winding ratio constant corresponding to the tap position are stored in advance and stored in the transformer. the detected secondary voltage V _2, the current I ₂ and the winding impedance corresponding to the tap position signal Z _T, using a constant winding ratio N _T detected primary voltage V ₁ of the said transformer from the following equation calculation A primary voltage detection method for a transformer. (Equation 1) 2. A device for detecting a secondary voltage, a secondary current, and a tap position of a transformer having a tap switching device, and a winding impedance and a winding ratio constant corresponding to a tap position signal are stored in advance. A constant selection unit that selects a constant corresponding to the detected tap position signal; and converts the detected analog voltage value and current value into a digital signal, and converts the converted voltage and current digital values V ₂ , a first calculator for calculating the original to V _{² 2,} I _{2 2} and V ₂ · I ₂ sinθ a I _2, the winding impedance constant computed value obtained by the calculation unit, the winding Hitei number characterized by comprising a second calculator for calculating a primary voltage V ₁ of the transformer with a voltage drop detector for detecting a primary voltage drop rate of the transformer than V ₁ obtained by this calculation Primary voltage detector for transformers