SU1339681A1 - Apparatus for correcting an error of single-stage instrument transformer - Google Patents

Abstract

The invention relates to electrical engineering — a relay circuit and can be used with current and voltage measuring transformers, both in alternating current and in direct current. The device is equipped with three adders 5, 8, 10, two differentiators 4 and 9, a testing unit 11 and a fault indication unit 12. The test unit is given signals proportional to the primary and secondary current and voltage, and at its output, signals on the state of the measuring transformer, a discrete fault signal, and parameter values indicated by indicating devices are received. 1 il. OO with with at 00

Description

The invention is concerned with electrical engineering, R in particular, with relay protection, and can be used with current and voltage measuring transformers in both direct and non-current current systems.

The purpose of the invention is to increase the reliability with | | of the operation and to ensure the possibility of using it for the measuring current transformer and for the voltage transformer, in particular for current.

The drawing shows a block diagram of the measuring transformer with correction. The device contains the first resistor 1 included in the secondary circuit of the transformer (T) alongside with its load 2, the second resistor 3 connected directly to the secondary winding of the transformer, differentiator 4, adder 5, integrator 6, nonlinear functional converter 7, adder 8, differentiator 9 , adder 10, block 1 I testing and block 12 of indication of malfunction and parameters otk. yuneny. The scale of the pyioniHc blocks, the functions of which can be iio.-iHsiTf) are not shown, but the coefficients are indicated on the inputs of the adders. Resistor 2 denotes a full co2p (), the load (impedance) of the measuring transformer. It is assumed that all bogies have a grounded point, which is the 5th pole of their input and | and, 1 input.

The system) () implements the system of equations: (IB / dl ---. (IJ. + IR -fLidi-./dtlW.S: B. {U ..dt + Rv | i9dt + Lvi .;) 11 (l / C) dB / dt + f (B); ii-- llt / Wi-f ivW.VW ,; I - iiRi-f L | di, / dt-t- WiSdB / dt where II, I; instantaneous the values of the nervous and secondary voltage T; i, 2 are the instantaneous values of the primary and secondary currents T;

RI RL resistances of the primary and secondary windings T; L | L. inductance dissipation of the primary and secondary windings T. Wi. V- - the number of turns of the primary and

secondary windings; 1. The length of the average largest si; 1Ovoy magnetic field in the core T;

S is the cross section of the ferromagnetic core T;

B - induction in the core; H - tension in se) dec1P1ke; С is the constant of the approximation of the hysteresis magnetic xapaK ie the core;

f (B) is a static (ignoring i-stere: iiica) magnetic characteristic of the core; 1pea. ibHoe irem.

From these equations, the formulas of the mash-ngab coefficients are taken.

The device works as follows. The voltage proportional to the secondary current of the instrument transformer, from resistor 1, is fed to the input of differentiator 4. The output signal of differentiator 4 with L2 / W2S coefficient, secondary current signal from resistor 1 with coefficient, and secondary voltage signal from resistor 3 with coefficient 1 / W2S is connected to the inputs of the adder 5, the output of which receives a voltage proportional to the derivative of the induction in the core of the transformer with respect to time.

This signal is fed to the input of the integrator 6 and further to the input of the nonlinear functional converter 7, at the output of which there is a signal f (B), which with the coefficient t / W | enters the input of the adder 8. The two other inputs of the adder receive the signals of the induction derivative with the coefficient V2 / W | and secondary voltage with a factor l / C {t / W |). At the output of the adder 7, a signal is obtained proportional to the primary current of the transformer, which is then differentiated in the differentiator 9 and differentiated with the coefficient LI, is fed to the input of the adder 10, the other two inputs of which receive the signals of the induction derivative with the coefficient WiS and primary

Q current with a coefficient Ri. A primary voltage signal is formed at the output of em.m. mater.

So get true, with the correction of the pogrenisti, introduced by the core of the measure; | ndogo transformer,

5 values of the primary current (at the output of the adder 8) n the primary voltage (at the output of the adder 10). Since the mathematical description equation is compiled for instantaneous values of voltages and currents, it does not depend on their change.

0 in time and remains valid for any kind of temporal dependencies. Therefore, the device is applicable (1 for measuring DC voltages and currents.

In test block 1, to the input of which the spine:. : ia: i T signals of primary and secondary TOKiiii and voltages are carried out under the ausp; norpeniHOCTn, measurement of the transformation ratio and the ratio of the power supplied to the primary circuit and transmitted to the secondary circuit. When Q. Yunipip of these parameters is from the original g1 in the process), a discrete fault signal is generated — with a sufficiently large number of deviations, and the indicated parameters themselves are indicated by using instruments or other / m

5 points are registered.

Use before. A1 AE | () HS) devices with iKiBijiuiueT Hope / "testing unit: - Nost1 systems, using n, lh: Err: current and voltage transformers, and eliminates the need for periodic testing of instrument transformers with equipment disconnection, unloading personnel. In addition, the use of the proposed device extends the possibilities of using ferromagnetic single-stage measuring current and voltage transformers up to their use in DC systems for measuring currents and voltages. This opens up new possibilities for measuring, protecting and automating DC systems.

Claims (1)

Apparatus of the Invention A device for error correction of a single-stage measuring transformer containing a first resistor connected in a secondary circuit of a current transformer in series with a load, a second resistor connected in parallel with the secondary winding of a current transformer, differentiator whose input is connected to a common point of the first resistor and the load, the adder, the inputs of which are connected to the common connection point of the first resistor and the load, to the output of the differentiator and to the moving terminal of the second resist ora, you- 0 5 five the adder stroke is connected to the integrator, the output of which is connected to the ne, 1 linear converter, differs in 11 (sss.ch so that, in order to ensure the reliability of the fundamental and to use the device for transforming the direct current, it is complemented by 1 is equipped with second and third adders, a second differentiator, test blocks and an indication of the malfunction and disconnection parameters, while the inputs of the second sum.mmator are connected to the output of the first summator, the output of the nonlinear converter, to o The connection point of the first resistor and the load, the output of the second adder is connected to the input of the second differentiator, the output of which is connected to the input of the third adder, the inputs of which are also connected to the output of the second adder and the output of the first adder, the output of the third adder serves as the output of the device the test block inputs are connected to the movable output of the second resistor, to the inputs of the nerve, second and third SM.mators, to the outputs of the second and third adders, the output of the test block is connected to the input of the block fault indication and shutdown parameters.