RU14292U1 - DEVICE FOR VERIFICATION OF HIGH VOLTAGE MEASURING VOLTAGE TRANSFORMERS - Google Patents

Abstract

A device for checking high-voltage measuring voltage transformers, containing a high-voltage capacitive voltage divider, consisting of a measuring and two shielding circuits, a switch for short-circuiting part of the capacitors, a circuit for comparing the metrological characteristics of the voltage transformer being verified with the characteristics of standard measuring instruments, which is made in the form of a current comparator, which consists of two adjustable arms, one of which is connected to the low-voltage output of the high-voltage capacitive voltage divider, another through an additional capacitor and inductive voltage divider - to the secondary winding of the voltage transformer being verified, and the middle point - to the grounded terminal of the high voltage measuring voltage transformer, and a high voltage source to which the high voltage capacitive voltage divider and the primary winding of the calibrated are connected voltage transformer, characterized in that a circuit for comparing the metrological characteristics of the voltage transformer being verified with the characteristics of standard measuring instruments, it is presented in the form of a multi-decade current comparator, one shoulder of which is made of one-decade and connected to the low-voltage output of a high-voltage capacitive voltage divider, the middle point is connected to the grounded terminal of the voltage transformer being verified, and the second shoulder of the current comparator is made of multi-decade and connected via a composite air capacitor to the secondary winding of the voltage transformer being verified, and the capacitor consists of three nominees

Description

Device for checking high voltage measuring voltage transformers

The utility model relates to electrical engineering and is intended for the verification of high voltage measuring voltage transformers at the place of their operation at operating voltage at real load.

A device for checking high-voltage measuring voltage transformers (prototype) 1, comprising a high-voltage capacitive voltage divider, consisting of a measuring and two shielding equipotential circuits in the form of series-connected capacitors with two terminals on a common axis and screens to them, a switch for short-circuiting part of the capacitors, an inductive voltage divider, which is connected to the output of the verified high-voltage measuring voltage transformer, an additional ductive voltage divider, current comparator, which consists of two adjustable arms, one of which is connected to the low-voltage output of the high-voltage

GOIR 35/02

capacitive voltage divider, another through an additional capacitor - to the output of the inductive voltage divider, and the middle point - to the grounded terminal of the high voltage measuring voltage transformer, and a high voltage source to which the high voltage capacitive voltage divider and the verified voltage transformer are connected 1.

The disadvantage of the prototype described in 1 is as follows. Balancing the circuit and determining the conversion coefficients of the capacitive voltage divider P, P2, Pb is performed using a current comparator and an inductive voltage divider, while the readout

P, Pr and Pr is produced by an inductive voltage divider. it

requires the use of expensive inductive voltage dividers in the device with a wide range of input voltages, which greatly complicates the device.

The objective of the utility model is a constructive simplification of the circuit of the device for checking high-voltage measuring voltage transformers.

To achieve this goal, in a device for checking high-voltage measuring voltage transformers, containing a high-voltage capacitive voltage divider, consisting of a measuring and two shielded lean circuits, a switch for short-circuiting part of the capacitors, a circuit for comparing the metrological characteristics of the voltage transformer being verified with the characteristics of standard measuring instruments, which is made in the form of a current comparator, which consists of two adjustable arms, one of which is connected to the low voltage terminal of the high voltage capacitive voltage divider, the other through an additional capacitor and inductive voltage divider to the secondary winding of the voltage transformer being verified, and the middle point to the grounded terminal of the high voltage voltage measuring transformer, and the high voltage source to which the high voltage capacitive voltage divider is connected and primary winding of the verified voltage transformer, a circuit for comparing the metrological characteristics of the verified transform A voltage protector with the characteristics of standard measuring instruments is presented in the form of a multi-decade current comparator, one arm of which is made of one-decade and connected to the low-voltage terminal of a high-voltage capacitive voltage divider, the middle point is connected to the grounded terminal of a voltage transformer being verified, and the second shoulder of the current comparator is multi-decade and connected via a composite air capacitor to the secondary winding of the voltage transformer being verified, and the composite capacitor it consists of three nominally equal capacitors connected in series-parallel circuit, while in the process of determining the conversion coefficient of a capacitive voltage divider in the form of a series-connected closable part and an output capacitor, the capacitors are connected in series, and in the process of determining the conversion coefficients of capacitive voltage dividers in the form of a series-connected high-voltage shoulder, the closable part and the output capacitor or in the form of series-connected high-voltage About the shoulder and the output capacitor, the capacitors are connected in parallel.

In FIG. 1 schematically shows a device for checking high voltage measuring voltage transformers; in FIG. 2 schematically shows a measurement circuit of Pz at operating voltage.

A device for checking high-voltage measuring voltage transformers contains a current comparator 1, consisting of a one-decade

common-mode winding of the left shoulder 2 and multi-decade common-mode winding of the right shoulder 3, quadrature winding 4, indicator winding 5, used to connect the indicator 6, switches 7, 8 for measuring the number of turns of the common-mode windings of the current comparator, switches 9, 10, 11 for measuring the number of turns quadrature winding of the current comparator, resistors 12, 13, 14 in the circuit of the quadrature winding 4 of the current comparator; a composite air condenser 15, consisting of three equal equal high-voltage capacitors 16, 17, 18, a variable capacitor 19, switches 20, 21 for switching capacitors from parallel to serial; verifiable high voltage measuring voltage transformer 22 with a load in the secondary circuit 23; a high-voltage capacitive voltage divider 24, consisting of a high-voltage arm 25, a stepwise short-circuit part of the capacitors 26 and an output arm (capacitor) 27, switches 28, 29, 30.

In this case, the high-voltage capacitive voltage divider 24 consists of series-connected and nominally equal high-voltage capacitors with very low losses and a small dependence of the capacitance of the capacitors on the applied voltage.

A device for checking high-voltage measuring voltage transformers operates as follows.

The amplitude of the circuit is balanced by changing the shoulder ratio of the in-phase windings 2, 3 of the current comparator 1 by means of switches 7, 8. By phase, balancing by changing the number of turns of the quadrature winding 4 using switches 9, 10, 11.

If the magnetic flux in the heart of the current comparator 1 is equal to zero, which is indicated by the zero reading of the zero indicator 6, the complex transformation coefficient of the voltage transformer being verified is equal to the complex set k (, 5tg) "2 where Ui and U2 are the primary and secondary voltage of the measuring transformer, respectively voltage 22; Ci5 - capacity in the winding circuit 3 of the current comparator; С24 - equivalent capacitance of a measuring capacitive voltage divider; P2 - the number of turns of the winding 2 of the current comparator; Pz - the number of turns of the winding 3 of the current comparator; - the angle of shift between the primary and secondary voltage of the voltage transformer 22. When balancing the circuit by changing the number of turns of the windings of the shoulders of the current shedder, a separate readout of the components of the ex transformation coefficient of the verified transformer 22 is easily ensured. Transformation coefficient (K) is: j 15 3 C) 24 2 Angular the inferiority of the voltage transformer under test 22 is expressed by the expression: 1 P, (P) with P,. (3) 3 where (- circular frequency;

3 - the number of turns of the first decade of the winding 3 of the current comparator;

4 - the number of turns of the winding 4 of the current comparator.

The error in the ratio of capacitances C is and € 24 in expression (2) is eliminated by short-circuiting the capacitance 26 of the measuring capacitive voltage divider. The application of this method in a circuit with vector addition of currents in the current comparator 1 is possible if the potentials of points A and B are equal, which is ensured by calibrating the low-voltage part of the circuit, which is performed in the following sequence.

The switch 30 is set to position “1, the switches 28, 29 to position“ 2. The shoulder ratio of the current comparator 1 is set to unity, while the angular error switches 9, 10, 11 are set to zero. The switches 20, 21 of the composite air capacitor is in position "1 (that is, the capacitors 16, 17, 18 are connected in parallel, while the equivalent capacitance of the capacitors 16, 17, 18 is nominally equal to the capacitance of the output arm of the capacitive voltage divider). Then, the capacitance of the capacitor 19 is adjusted so that the null pointer 6 indicates zero.

Then the following operations are performed. Set the switches 29, 30 to position "2, and the switch 28 to position" 1. Balance the circuit by changing the number of turns of the right multi-decade

shoulder of the current comparator and record readings P: G C l-C C l-C C} C

25 26 25 27 26 27

With Co (

25 26P

Then, the switch 30 is moved to position "3. After balancing the circuit, the readings of the decade switches of the right shoulder of the current comparator are recorded. After this, a new equality is compiled:

Co)

Next, the switches 28, 30 are put in position "2, and the switch 29 is in position" 1. The ratio of the shoulders of the current comparator 1 is adjusted until the circuit is balanced, which corresponds to the new equality: С А-С fC

26 27

C O (

Solving together vfazhany (4, 5, 6) we find the transformation coefficient K by the obtained values:

j A A (1-P3)

(P2-A) Rz

It was experimentally established that the capacitances of capacitors of the type FGTI used in the circuit depend on the applied voltage in the following way: from zero to 60 V, the error due to the applied voltage is negative. From 60 V to 200 V, the error is zero. From 200 V to 500 V, the error is negative. Moreover, the capacity of the air condenser 15 practically does not depend on the applied voltage.

Therefore, if the operating voltage across the capacitors of the measuring capacitive voltage divider is outside the zero-fault zone, it is necessary to perform additional balancing of the current comparator before determining the coefficients A and Pi. For this, a circuit is constructed in accordance with FIG. 2. A voltage equal to the operating voltage at the output capacitor 27 is supplied to the circuit from the power supply 31. The arms of the current comparator are balanced with the help of the capacitor 19 at voltages corresponding to the voltage drop across the capacitor 27 when Pi and A are determined, which increases the accuracy of their measurement.

To measure Pb, a circuit is assembled in accordance with FIG. 3. The voltage from the power source 31 is applied to the circuit. If C26 and Ci are N series-connected capacitors, and the current comparator arms were balanced at a secondary voltage of U2 100 V, then the voltage supplied to the capacitive voltage divider C2b, Cz should be N100 V In this case, the operating voltage across the capacitors is equal to the balancing voltage. This leads to the exclusion of the error due to the dependence of the capacitance of the capacitors on the applied voltage when determining Pb. If the senior decade is not included in the countdown of the current comparator, then the composite pinched capacitor 15 is switched from parallel to serial connection using switches 20, 21. In this case, the capacitance of the composite air capacitor is reduced by 9 times,

which allows to increase the accuracy of the determination of Rz.

The proposed solution allows sushi to significantly simplify and reduce the cost of a device for checking high-voltage measuring voltage transformers. This is achieved by replacing a very complex and expensive; its inductive voltage divider with a wide measuring range, with a current comparator, one arm of which is multi-decade, and a composite air capacitor with the ability to switch the components of its capacitors from parallel to serial.

Author D.I. Nefedyev

1. Nefediev D.I. A device for checking high-voltage measuring voltage transformers // RF Patent No. 2086996. Publ. in B.I., No. 22, 08/10/97.

Literature

Claims (1)

A device for checking high-voltage measuring voltage transformers, containing a high-voltage capacitive voltage divider, consisting of a measuring and two shielding circuits, a switch for short-circuiting part of the capacitors, a circuit for comparing the metrological characteristics of the voltage transformer being verified with the characteristics of standard measuring instruments, which is made in the form of a current comparator, which consists of two adjustable arms, one of which is connected to the low-voltage output of the high-voltage capacitive voltage divider, another through an additional capacitor and inductive voltage divider - to the secondary winding of the voltage transformer being verified, and the middle point - to the grounded terminal of the high voltage measuring voltage transformer, and a high voltage source to which the high voltage capacitive voltage divider and the primary winding of the calibrated are connected voltage transformer, characterized in that a circuit for comparing the metrological characteristics of the voltage transformer being verified with the characteristics of standard measuring instruments, it is presented in the form of a multi-decade current comparator, one shoulder of which is made of one-decade and connected to the low-voltage output of a high-voltage capacitive voltage divider, the middle point is connected to the grounded terminal of the voltage transformer being verified, and the second shoulder of the current comparator is multi-decade and connected via a composite air capacitor to the secondary winding of the voltage transformer being verified, and the capacitor consists of three nominees equal to high-voltage capacitors connected in series-parallel circuit, while in the process of determining the conversion coefficient of a capacitive voltage divider in the form of a series-connected output capacitor and a closable part, the capacitors are connected in series, and in the process of determining the conversion coefficients of capacitive voltage dividers in the form of a series-connected high voltage arm , a lockable part and an output capacitor, or in the form of series-connected high the voltage arm and the output capacitor are capacitors connected in parallel.