JP2022000610A - Voltage measuring device - Google Patents

Abstract

To provide a voltage measuring device capable of accurately measuring voltage in a high-voltage distribution system and the like.SOLUTION: A measurement IF circuit A is built in a connector K1 of a high voltage device side X or cable K. As a result, the distance (length) from a capacitor voltage divider C to a terminal load is made extremely short, and the adjustment of the capacitance due to the influence of impedance of the cable K is made unnecessary or minimized.SELECTED DRAWING: Figure 1

Description

The present invention relates to an improvement of a device for measuring a voltage of a high voltage distribution line by using a capacitor type instrument transformer.

As an instrument transformer used for voltage measurement of a power transmission and distribution system, a capacitor type instrument transformer (PD) using voltage division by capacitance has been conventionally known. Capacitor-type instrument transformers take advantage of their small size, light weight, and low cost compared to winding-type instrument transformers (PTs), and have been used in many power transmission and distribution system voltage measuring devices in recent years. The PD can step down a high voltage to a voltage that is easy to use in a control circuit and operate a voltmeter or the like.

The basic configuration of the PD is described in Non-Patent Document 1 below, and the connection diagram of the capacitor voltage divider is configured as shown in FIG. As shown in FIG. 4, the PD is installed between the high-voltage distribution system and the ground, and consists of capacitors C ₁ and C ₂ that divide the high voltage and a terminal load (voltmeter, etc.) 1 connected in parallel to the capacitor C _2. Has been done. Note that Z in FIG. 4 indicates the impedance of the terminal load 1.

When measuring the voltage of a high-voltage distribution system, the transformer D for a capacitor type instrument is installed on a high-voltage side device such as a switch, and the terminal load 1 is, for example, a low-voltage side such as a slave station constituting a distribution line automation system. Often prepared for equipment.

Hitachi Review 1954 Separate Volume 7 Transmission and Transformation Special Issue Page 107 Coupling Capacitor Type Instrument Transformer [2] Principle of PD

However, the voltage transformer D for a capacitor type instrument used in this way is affected by the impedance of the cable (wiring) between the high-voltage side device and the low-voltage side device, and the voltage value measured by the low-voltage side device is determined. There is a problem that an error occurs with the actual system voltage value.

That is, when the impedance Z of the terminal load 1 is infinite, the relationship between the _{terminal voltage E 2} and the system voltage E _{1 shown in FIG. 4 is (E 2} / E ₁ ) = C ₁ / (C ₁ + C ₂ ). Therefore, ideal voltage conversion can be performed, but since the impedance Z of the terminal load 1 has a constant value, a minute current corresponding to it flows. This causes a voltage drop in the cable (wiring), which inevitably causes an error between the measured value and the actual voltage value.

Further, when accuracy is required for the measured value as in a voltage sensor, it is necessary to adjust the capacitance for each device so that the difference between the measured value and the actual voltage value is within the tolerance.

As a method for solving such a problem, as shown in FIG. 2 (PD circuit explanatory diagram) of Non-Patent Document 1, a resonance reactor is provided to reduce the above error, or in FIG. 5 of the present application. As shown, in the capacitor C _{2 , a method is known in which the capacitor C 22} for adjusting the capacitance is adjusted in parallel with C ₂₁ so as to be within a predetermined (desired) accuracy.

However, as described above, when the capacitor type instrument transformer D is installed in the high-voltage side equipment and the termination load is prepared in the low-voltage side equipment, is the cable (wiring) between the two installed in the equipment installation form (on a pillar?) Depending on whether it is in the ground, etc.), its length will also differ greatly.

In addition, since the cable (wiring) becomes long and easily affected by ambient noise, there is a concern that accurate measurement cannot be performed due to the high impedance of the terminal load.

Therefore, in the present invention, even when a capacitor-type voltage transformer is installed in the high-voltage side device, the terminal load is installed in the low-voltage side device, and the two are connected by a cable (wiring), the measurement is performed in the low-voltage side device. It provides a voltage measuring device in which the voltage value does not cause an error with the actual system voltage value.

According to the first aspect of the present invention, a measurement IF circuit is provided in a high-voltage side device provided with a voltage transformer for measuring the voltage of a high-voltage distribution system, and a voltage value measured in the low-voltage side device through the measurement IF circuit is obtained. It is characterized by digital transmission.

The invention according to claim 2 is characterized in that the measurement IF circuit according to claim 1 is incorporated in a high-voltage side device.

The invention according to claim 3 is characterized in that the measurement IF circuit according to claim 1 is built in a connector in a high-voltage side device.

The invention according to claim 4 is characterized in that the measurement IF circuit according to claim 1 is incorporated in a cable connector connected to a high-voltage side device.

The invention according to claim 5 is characterized in that the digital signal is differentially transmitted by the measurement IF circuit according to claim 1 to 4.

According to the first to fourth aspects of the invention, the distance (length) to the terminal load can be made extremely short, so that the adjustment of the capacitance according to the cable can be unnecessary or minimized.

In addition, since the measurement IF circuit is installed in the high-voltage side equipment, the sensor signal from the capacitor type instrument transformer (PD) can be digitized and passed instead of being passed in analog, so noise in the cable can be passed. It is possible to suppress the influence as much as possible.

According to the fifth aspect of the present invention, the noise resistance performance of the cable can be improved by differentially transmitting the digital signal by the measurement IF circuit.

It is a block diagram which shows the voltage measuring apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the voltage measuring apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the voltage measuring apparatus which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the conventional voltage measuring apparatus. It is a block diagram which shows the other conventional voltage measuring instruments.

Examples of the present invention will be described with reference to FIG. In FIG. 1, E is a capacitor-type voltage transformer (PD) installed in a high-voltage side device X such as a switch installed in a high-voltage distribution system, and is a first capacitor C ₁ and a second capacitor C. It is composed of a capacitor C composed of _two.

A is a measurement IF circuit installed in the high-voltage side device, and A1 shows a protection circuit filter for protecting the circuit from surge voltage and removing noise. The ADC is an A / D converter that digitally converts an analog voltage value divided (stepped down) by the capacitor voltage divider C, and A2 indicates a connection interface (serial interface).

A3 is a protection circuit that protects the measurement IF circuit A from overvoltage and overcurrent, and A4 indicates a high-voltage device-side connector for connecting an external device to the measurement IF circuit A.

Y indicates a low-voltage device side device, and Y1 indicates a low-voltage device side connector. K is a cable connecting between the high-voltage side device X and the low-voltage side device Y, and includes a first connector K1 connected to the high-voltage side device X and a second connector K2 connected to the low-voltage side device Y. Has been done.

When measuring the voltage value of the high-voltage distribution system in the voltage measuring device configured in this way, the voltage signal stepped down by the capacitor voltage divider C is passed through the protection circuit filter A1 of the measurement IF circuit A to the A / D converter. It is converted from an analog signal to a digital signal by the ADC.

The digitally converted voltage signal is transmitted to the low voltage side device Y via the cable K, so that the voltage signal is measured in the low voltage side device Y.

In the voltage measuring device shown in FIG. 1, the length between the capacitor voltage divider C and the measuring IF circuit A as the terminal load can be extremely shortened. Therefore, it is possible to minimize the influence of the measured voltage value on the impedance of the cable K, and unlike the case of FIG. 5, it is not necessary to adjust the capacitance according to the cable K, or Only the error of the voltage dividing capacitors C ₁ and C _{2 needs to be adjusted.}

That is, as compared with the case of FIG. 5, it is possible to realize accurate voltage measurement without requiring _{adjustment of the adjusting capacitors C 22} and C _3.

FIG. 2 shows the configuration of the voltage measuring device according to the second embodiment of the present invention. The configuration of FIG. 2 that differs from the configuration of FIG. 1 is that the measurement IF circuit A is installed in the connector A4 of the high-voltage side device X. By installing the connector A4, the measurement IF circuit A can be removed together with the connector A4 by removing the connector A4 from the high-voltage side device X.

FIG. 3 shows the configuration of the voltage measuring device according to the third embodiment of the present invention. In the configuration of FIG. 3, which is different from the configurations of FIGS. 1 and 2, the measurement IF circuit A is installed in the first connector K1 of the cable K. Therefore, the measurement IF circuit A can be removed together with the first connector K1 by removing the cable K from the high-voltage side device X.

In the voltage measuring devices shown in FIGS. 1 to 3, the measurement IF circuit A cancels the noise even if noise is added to the cable K by differentially transmitting the digital signal to the low-voltage side device. It is possible to improve the noise resistance performance and reduce the malfunction of the device.

As described above, according to the voltage measuring device of the present invention, the voltage of the high voltage distribution system can be accurately measured without being affected by the impedance of the cable (wiring) to the device on the low voltage side.

Further, it is possible to reduce the need to add or remove a capacitor for adjusting the capacitance to the capacitor type instrument transformer (PD).

The configuration of the measurement IF circuit A shown in FIGS. 1 to 3 is an example, and is not limited to the configuration as long as it has a function of converting a voltage value from an analog value to a digital value. .. Further, it is natural that the configuration of the low-voltage side device is not limited to the configuration shown in FIGS. 1 to 3.

The present invention is mainly used for a device for measuring the voltage of a high voltage distribution system.

A Measurement IF circuit A1 Protection circuit and filter A2 Connection interface A3 Protection circuit A4 High voltage equipment side connector ADC A / D converter C Capacitor voltage divider C ₁ First capacitor C ₂ Second capacitor C _{22 For} capacitance adjustment Capacitors D, E Capacitor type instrument transformer X High-voltage side equipment Y Low-voltage side equipment K cable K1 1st connector K2 2nd connector

Claims (5)

A measurement IF circuit is provided in a high-voltage side device equipped with an instrument transformer for measuring the voltage of the high-voltage distribution system, and the voltage value measured to the low-voltage side device is digitally transmitted through the measurement IF circuit. A voltage measuring device characterized by that. The voltage measuring device according to claim 1, wherein the measuring IF circuit is built in the high voltage side device. The voltage measuring device according to claim 1, wherein the measuring IF circuit is built in a connector in the high voltage side device. The voltage measuring device according to claim 1, wherein the measuring IF circuit is built in a cable connector connected to the high voltage side device. The voltage measuring device according to any one of claims 1 to 4, wherein the measuring IF circuit is configured to transmit a digital signal differentially.

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