SU1575137A1 - Apparatus for disclosing asymmetry of electric quantities system - Google Patents

Abstract

The invention relates to electrical engineering and can be used in protection against asymmetric modes. The aim of the invention is to improve the speed of the device. The goal is achieved by introducing a maximum signal element 2, a signal minimum memory element 3, a scale converter 4, and a control pulse generator 7 into the device. which are fixed by the memory elements of maximum 2 and minimum of 3 signals and are compared by element of comparison 5 at a fixed moment of time determined by control pulse generator 7. 3 Il.

Description

The invention relates to electrical engineering, in particular, to relay protection of electrical systems, and can be used in protection devices against asymmetric modes.

The purpose of the invention is to increase the speed of the device.

FIG. 1 shows a functional diagram of the device; in fig. 2 - functional diagram of the control pulse generator; in fig. 3 - time diagrams of voltages, which are used for the operation of the device.

The device (Fig. 1) contains a three-phase rectifier 1, connected by an output to the main inputs of the memory elements maximum 2 and minimum 3, signal, scale converter

4 connected by the input to the output of the memory element of the maximum of signal 2, and output to one input of the element of comparison 5 connected by another input to the output of the memory element of the minimum of signal 3, element 6, connected by one input to the output of the element of comparison 5, and the other input to output the generator of control pulses 7 and the pulse extender 8 connected by the input to the output element And 6.

The minimum signal storage element 3 can be performed, for example, in the form of an adder 9 connected via an output through the maximum signal storage element 10 to one input of the adder 11, to another, whose input,

SP

J

SP

with

as well as adder 9, a reference voltage is applied.

The generator of control pulses 7 can be performed, for example, in the form of an auto-generator of pulses 12, a differentiator 13 and diodes 14 and 15 (Fig. 2)

The device works as follows

The storage elements of the maximum of signal 2 and 10 remember the maximum (Instantaneous value of the input signal for the period between two pulses arriving at the control inputs of these elements from the first output of the control pulse generator

A signal Y- is output from the output of the three-phase rectifier 1 (FIG 3) to the input of the memory element storing the signal 2. Therefore, the signal at the output of element 2 is equal to the maximum instantaneous value of the signal at the output of the three-phase rectifier 1 at a given time Y max (Y,).

A signal from the output of the adder 9 is fed to the input of the memory element of the maximum signal 10. A signal from the output of the three-phase rectifier 1 is fed to the inverting input of this adder, and a reference signal is sent to the non-inverting input.

Yof7 signal. Therefore, the output signal

L0f7

adder 9 is equal to the difference of the reference signal and the signal from the output of rectifier 1, Y9 Yon-Y ,.

Therefore, the maximum memory element of the signal 10, remembers the maximum instantaneous value of the difference Yon-Y

Y10 max

(Yo9- Y,).

The signal from the output of the memory element 10 is applied to the inverting input of the adder 11, to the non-inverting input of which the reference signal Yen is also fed. Therefore, the signal at the output of the adder 1I is equal to

Y

Yon - max

(YOO-Y,)

or, which is the same, is equal to the minimum instantaneous value of the signal at the output of the rectifier 1

Y „min (Y.,).

The scaler 4 changes the signal level

X4. max (Y,

where K is a proportionality factor less than one.

begs

Thus, one input of Comparative Element 5 is given a signal proportional to the maximum instantaneous value of the signal at the output of rectifier 1, and another input - a signal equal to the minimum instantaneous value of the signal Y1 for the same period of time, Comparison Element 5 is activated, if the signal at one input there is more signal on the second, i.e.

To Max

(Y,)

 min

V

or

begs

min (Y 1)

- - 7G7-T v. L.

max (Y

0

five

0

five

O

five

0

five

The signal from the output of the comparison element 5 is fed to one input of the element AND 6. The second input of this element is supplied with a pulse signal from another output of the control pulse generator 7, which allows the signal from the output of the comparison element 5 to be transmitted to the expander 8. a pulse signal at this generator output 7 appears immediately before the signal appears at its first output, which provides a comparison of the signals at the inputs of the comparison element 5, memorized by elements 2 and 10 during the time between two pulses applied to their control inputs, which causes these elements to be reset.

Thus, this device responds to the ratio of the minimum for a given time instantaneous value of the signal at the output of the three-phase rectifier to the maximum instantaneous value of the same signal.

FIG. The diagrams for the three-phase symmetric system of monitored values and the bottom are given below: - the three-phase rectifier 1 (Y) signal output frames with two semi-single rectifier, and FIG. 36 - the same diagrams, but for the asymmetrical mode.

In the Asymmetric mode, the input values are generally not equal in magnitude and shifted by different angles. Therefore, the ratio of the minimum instantaneous value of the signal at the output of the rectifier is min (Y t; to the maximum instantaneous value — max (Y) is less than in the symmetric mode. By choosing the value of the coefficient of proportionality K for the scaler 4, the device is adjusted so that in the mode it does not work, but acts only when asymmetry occurs.

There is no smoothing filter in the device and its response time is determined practically only by the period of the pulse signals at the output of the control pulse generator.

With a two-half-period execution of the rectifier, the period following these signals can be taken to be equal to half the period of the controlled values.

Claims (1)

Invention Formula A device for detecting asymmetry of a system of electrical quantities, containing a three-phase rectifier, an element of comparison, an element AND, as well as a pulse expander, characterized in that, in order to increase . speed, a signal maximum memory element, a signal minimum memory element, a scale converter and a control pulse generator, with IQ of this three-phase rectifier output is connected to the main inputs of the maximum and minimum memory elements, the control inputs of which are connected to the generator output of control pulses, the output of the maximum signal memory element is connected via a scale converter to one input of the comparison element, to the other input of which is connected output 20 of the minimum signal storage element, the output of the comparison element is connected to one input of the AND element connected by a second input to another output of the control pulse generator, 25 and the output of the AND element is connected to the input of the pulse expander. 1 FIG. 2 „X H  "with РЪ I one j