RU2248002C2 - Device for calibrating instrument voltage transformer - Google Patents

Abstract

FIELD: instrument engineering.

SUBSTANCE: device has high-voltage sound frequency signal generator, dc double-rowed potentiometer, high- and low-voltage compensation measurement units which are brought into circuits of primary and secondary windings of instrument voltage transformer to be calibrated. Measurement units have diodes and capacitors for working voltages. Dc dividers and sources are connected through galvanometers.

EFFECT: widened test voltage range.

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Description

The invention relates to electrical engineering and is intended for calibration of measuring voltage transformers in an extended frequency range.

A device for checking measuring voltage transformers containing a source of high voltage, high voltage and low voltage capacitors in the primary and secondary windings of the verified measuring voltage transformer, electromagnetic current comparator and zero indicator [1].

The disadvantage of this device lies in the difficulty of operating high-voltage gas-filled capacitors used in the device, as well as in the impossibility of determining the transformation coefficient of the calibrated measuring voltage transformer in a wide frequency range.

A device (prototype) is known for checking measuring voltage transformers, comprising a high voltage source, a capacitive voltage divider, an inductive voltage divider, an electromagnetic current comparator and a zero indicator [2].

The disadvantage of this device (prototype) is the inability to determine the transformation coefficient of the verified measuring voltage transformer in an extended frequency range.

The problem to which the invention is directed is to develop a technical solution that provides the ability to determine the transformation coefficient of the voltage measuring transformer being verified in an extended frequency range.

This problem is solved as a result of the fact that a high-voltage audio signal generator, a two-row DC potentiometer, a high-voltage voltage transducer are introduced into the device for calibrating measuring voltage transformers containing a high voltage source, a capacitive voltage divider, an inductive voltage divider, an electromagnetic current comparator and a zero indicator low-voltage compensation measuring units in the circuit of the primary and secondary windings of the verified voltage measuring transformer, which s contain diodes and capacitors on the operating voltage, which are connected through the galvanometer dividers DC voltage and DC voltage sources. The output arm of the DC voltage divider of the high voltage compensation measuring unit is connected to the terminals of the first row of the double-row DC potentiometer, the output arm of the DC voltage divider of the high voltage compensation measuring unit is connected to the terminals of the second row of the two-row DC potentiometer. Verifiable measuring voltage transformer is connected to a high-voltage generator of sound frequency signals.

The ability to verify voltage measuring transformers in an extended frequency range is ensured by the fact that the device uses compensation measuring units designed for the primary and secondary voltage of the voltage measuring transformer being verified.

The drawing shows a diagram of a device for checking measuring voltage transformers.

A device for checking measuring voltage transformers contains a high-voltage audio signal generator 1, a calibrated voltage measuring transformer 2, a capacitive voltage divider 3, an inductive voltage divider 4, an electromagnetic current comparator 5, a zero indicator 6, a high-voltage 7 and a low-voltage 8 compensation measuring units and a double-row potentiometer DC 9. The high-voltage compensation measuring unit contains a diode 10, a capacitor 11, a galvanometer 12, a constant divider voltage 13, consisting of a high voltage arm 14 and an output (low voltage) arm 15 and a constant voltage source 16. The low voltage compensation measuring unit comprises a diode 17, a capacitor 18, a galvanometer 19, a DC voltage divider 20, consisting of a high voltage arm 21 and an output (low voltage) ) of the arm 22 and a constant voltage source 23. The output arm 15 of the DC divider 13 is connected to the terminals of the first 24 row of a double row DC potentiometer 9, and the output arm 22 of the DC divider about voltage 20 is connected to the terminals of the second 25 row of a double row potentiometer DC 9.

The operation of the device for checking measuring voltage transformers is as follows.

The scheme is assembled in accordance with the drawing. At the first measurement stage, the transformation coefficient of the measuring voltage transformer 2 is determined at a frequency of 50 Hz and the following operations are performed. From the high-voltage generator of audio signals 1, a voltage equal to the rated primary voltage of the voltage measuring transformer under test 2 with a frequency of 50 Hz is supplied to the circuit. The transformation coefficient of the measuring voltage transformer 2 is determined using a capacitive voltage divider 3, inductive voltage divider 4, electromagnetic current comparator 5 and zero indicator 6 [2]. Then, the primary and secondary voltages of the voltage measuring transformer 2 are measured using compensation measuring units 8. The voltage from the primary and secondary windings U1 and U2 of the voltage measuring transformer 2 is supplied to the capacitors 11, 18 through diodes 10, 17, by introducing a compensating voltage from the DC voltage sources 16, 23, a zero (minimum) current value is reached through galvanometers 12, 19. The compensating voltage is measured using a two-row constant current potentiometer 9 and a DC voltage dividers 13, 20. The division factors of dividers DC voltage 13, 20 are chosen so that the readout of the first 24 and second 25 rows of DIP DC potentiometer 9 provide the required measurement accuracy.

The transformation coefficient of the measuring voltage transformer 2 at a frequency of 50 Hz is equal to:

U1 and U2 - respectively, the primary and secondary voltage of the measuring voltage transformer 2;

U ₁₆ and U ₂₃ - compensation voltage supplied, respectively, from sources of constant voltage 16, 23;

U _24-1 and U _25-1 - readings of the first 24 and second 25, respectively, of a two-row DC potentiometer 9;

K _2-1 - transformation coefficient of the measuring voltage transformer 2 at a frequency of 50 Hz;

n ₁₃ and n ₂₀ are the division factors, respectively, of the DC voltage dividers 13, 20.

At the second measurement stage, the transformation coefficient of the voltage measuring transformer 2 is determined at a frequency above 50 Hz and the following operations are performed. The measuring circuit formed by the capacitive voltage divider 3, the inductive voltage divider 4, the electromagnetic current comparator 5 and the zero indicator 6 are switched off. A voltage equal to the rated primary voltage of the voltage measuring transformer 2 with a frequency of over 50 Hz is supplied to the circuit from the high-voltage generator. The transformation coefficient of the voltage measuring transformer 2 is determined using compensating measuring blocks 7, 8.

The transformation coefficient of the measuring voltage transformer 2 at a frequency of over 50 Hz is equal to:

Where:

U _24-2 and U _25-2 - readings, respectively, of the first 24 and second 25 two-row DC potentiometer 9;

To _2-2 - the transformation coefficient of the measuring voltage transformer 2 at a frequency of over 50 Hz.

Solving equation (1) and equation (2) together, after simple intermediate transformations we get:

Thus, the proposed technical solution allows to determine with high accuracy and in an extended frequency range the transformation coefficient of voltage measuring transformers, which is ensured by the use of compensation measuring units in the circuit.

Sources of information

1. Tavdgiridze L.N. A mobile laboratory for testing measuring instruments for high voltage industrial frequencies up to 300 V and 100 kV DC // Measuring Equipment, 1981, No. 2, p. 68-70.

2. Patent RU 2086996 C1, G 01 R 35/02, 08/10/97. (Nefediev D.I.).

Claims (1)

A device for checking measuring voltage transformers containing a high voltage source, a capacitive voltage divider, an inductive voltage divider, an electromagnetic current comparator and a zero indicator, characterized in that a high-voltage audio signal generator, a two-row DC potentiometer, a high-voltage and low-voltage compensation measuring devices are introduced into the device blocks in the circuit of the primary and secondary windings of the voltage measuring transformer being verified, which clamp diodes and capacitors for operating voltages, to which DC dividers and DC voltage sources are connected through galvanometers, the output arm of the DC voltage divider of the high-voltage compensation measuring unit is connected to the terminals of the first row of the double-row DC potentiometer, the output arm of the DC voltage divider of the low-voltage compensation measuring unit is connected to the terminals of the second row of a two-row DC potentiometer, and the verified The measuring voltage transformer is connected to a high-voltage generator of sound frequency signals.