SU1659886A1 - Device for measuring ratio of actual alternate current value to its nominal value - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used in the measuring bodies of relay protection. The purpose of the invention is to simplify the device. The device contains an intermediate measuring transducer 1, a counter 3, a register 4, a computing unit 5, a pulse generator 6, an element 7. The introduction of the converter control element 2 1, a counter 10, elements 8 and 9 simplifies an intermediate measuring converter, which can Converters with non-linear characteristics are used. 2 Il.

Description

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about

The invention relates to electrical measuring equipment and can be used in the measuring bodies of relay protection.

The purpose of the invention is to simplify the device.

FIG. 1 shows a block diagram of the device; in fig. 2 - time diagrams that show his work.

The device contains an intermediate measuring transducer 1, the current input of which is the input of the device, and the control input is connected to the output of the control element 2 of the intermediate measuring transducer. The outputs of the counter 3 are connected through the serially connected buffer register 4 and the computing unit 5 to the outputs of the device. The output of the generator 6 pulses connected to the first input of the first element And 7, the output of which is connected to the counting input of the counter 3, the reset input of the counter 3 is connected to the output of the element 8. The synchronization input register 4 is connected to the output of the element 9, the first input of which is connected to the output the converter 1, the first input of the element And 8 and the counting input of the additional two-bit binary counter 10; the first direct output of the counter 10 is connected to the first input of the element 2 and the second inputs of the elements 7 and 9, the first inverse output of the second output e And 8, the second direct output Q by the second input of the element 2, The current input of the converter 1 is connected to the input of the device.

Intermediate measuring transducer 1 can be made as a saturable current transformer, made on a core with a rectangular hysteresis loop and containing an additional winding, which is the control input of transducer 1.

The operation of the device is based on the fact that the measured current acts on the intermediate measuring transducer 1, determines the instant of the instantaneous value I of the measured current through zero and the instant of equality of the module of the instantaneous value 111 of the measured current of the reference value, count the number of pulses during the time interval, limit these moments, and convert this number to the desired value of the ratio, and to determine the moment of equality of the modulus of the instantaneous value And the measured current of the reference value The non-Zeta transducer 1 is affected by the bias signal s and the transition moment is determined

zero of the function U (i, s), for which the condition and (1Et, s) 0 are satisfied.

The timing diagrams of FIG. 2 are for the special case where the function

U (i, s) Krs, -uch-, where K is a coefficient, and

s6 (o, s}.

According to this function, the control signal s converter 1 is used in

0 as a reverse bias when negative values, proportional to instantaneous values of the measured current, are shifted by a constant value s towards positive values, and positive values are shifted towards negative values.

The simultaneous action on the converter 1 of the measured alternating current i and the displacement s is shown in FIG. 2 in

0 as equivalent input signals, the effect of which on converter 1 is identical to the simultaneous action of measured current i and offset 3 at s 0 and s S.

5 FIG. 2 shows: input signal 11

(measured alternating current I); equivalent input 12 at s 0 (equivalent unbiased input signal); equivalent input 13 at s s

0 (equivalent input signal when bias is present); an equivalent input signal 14 when the offset value s changes at the junction of the equivalent input signal through zero; point 15 defining

5 moment of zero crossing of the equivalent input signal 12 at s 0; point 16, determining the time of zero crossing of the equivalent input signal 13 at s S; pulses 17, counted by the counter

0 3; status change 18 counter 3.

The device works as follows.

In the initial state, the two-digit binary counter 10 is in the state

5 00. There is no offset at the control input of converter 1.

When the equivalent value passes through zero at point 5, a signal is generated at the output of converter 1, passing

0 through the AND element 8 to the reset input of the counter 3 and directly to the counting input of the counter 10, as a result of which the counter 3 is zeroed and the counter 10 is set to state 01.

five

The arrival of a combination of signals 01 from the direct outputs of the counter 10 to the inputs of the element 2 causes a negative bias signal to appear at the control input of the converter 1. At the same time

the pulses from the output of the generator 6 begin to flow to the counting input of the counter 3.

As the instantaneous value of the measured current and correspondingly equivalent input signal 14 further changes over zero (point 16), the output of converter 1 generates a signal coming from element 9 to the synchronization input of buffer register 4, overwriting the contents of counter 3 into it. After that, the signal from the output of converter 1 changes the state of counter 10, and a combination of 10m signals is installed on its direct outputs. In this case, the pulse counting by the counter 3 is stopped, and the bias signal at the control input of the converter 1 disappears.

As the instantaneous value of the measured current changes sinusoidally, this instantaneous value again passes through zero. At the output of converter 1, a next signal is formed, which flushes counter 3 and sets counter 10 to state 11, allowing counting of pulses and a corresponding change in the contents of counter 3 and ensuring that element 2 outputs a signal shifting the input signal of converter 1 in the direction opposite to the direction of its instantaneous change. values, i.e. in the positive area.

As the instantaneous value of the measured current and correspondingly equivalent input signal further changes through zero again, a signal is generated at the output of converter 1, which ensures that the new contents of counter 3 are written to buffer register 4 and the counter 10 is switched to state 00, where counter 3 stops and the circuit returns to its original state.

Computing unit 5 continuously

converts the number of pulses counted by counter 3 stored in buffer register 4 into the desired value of the ratio of the value of the alternating current to its nominal value.

Claims (1)

Invention Formula A device for measuring the ratio of an ac current to a nominal value, comprising an intermediate transmitter, a counter. the outputs of which are connected to the outputs of the device through a serially connected buffer register and computing unit, the first input of the first element I is connected to the output of the pulse generator, and the output to the counter input of the counter, characterized in that, in order to simplify the device, an element of the control of an intermediate measuring converter, an additional counter, is introduced into it, the second and third elements And, the control input of the intermediate measuring converter is connected to the output of the control element of the intermediate measuring converter, the first and the second the inputs of which are connected to the first and second direct outputs of the additional counter, the counting input of which is connected to the output of the intermediate measuring converter and the first inputs of the second and the third element And, the first inverse output to the second input of the second element And, the first direct output to the second inputs of the first and third elements And, the output of the second element And connected to the reset input counter, and the output of the third element And with the synchronization input of the buffer register. 7 X // / v . 2