SU1608594A1 - Apparatus for measuring coefficient of asymmetry in three-phase mains - Google Patents

Abstract

The invention relates to electrical engineering and can be used in the power industry for continuous control of voltage quality in three-phase networks of a three-wire line. The purpose of the invention is to increase the reliability and simplify the device. The device contains direct 1 and reverse 2 sequence filters, null organs 3,4, electronic controlled keys 6-8, triggers 11-13, comparison unit 15, analog-digital converter 16, recorder 17, terminals 18-20 for connecting the test voltage wives An electronic key 9, a null organ 5, a trigger 14 and an integrator 10 are entered into the device. 2 Il.

Description

1

The invention relates to electrical engineering and can be used in the power industry for continuous control of voltage quality in three-phase networks of a three-wire line.

The purpose of the invention is to increase the reliability and simplify the circuit design of the device.

Figure 1 presents the block diagram of the device; Fig. 2 is a diagram for explaining the operation of the device.

The device contains direct 1 and reverse 2 sequence filters, null-bodies 3-5, electronic keys 6-9, integrator 10, triggers 11-14, controls, block 15 comparing analog-to-digital converter 16, register 17, terminals 18-20 to connect the test voltage

In the device, terminals 18-20 for connecting the test signal are connected to filters of direct 1 and reverse 2 sequences. The output of the filter 1 is a direct sequence through the first null organ 3 and the first electron switch 6 is connected to the single input of the first control trigger 11 and the zero input of the second control trigger 12, as well as to the input of the comparison circuit 15, the second input to which is connected to the reference voltage source wives, The output of the negative-sequence filter 2 through the second null authority 4 and the third electronic switch 8 is connected to the zero input of the fourth control trigger 14, and also to the second input of the analog-digital converter 16, the output of which is connected to the register 17, the output of the first control trigger 11 is connected to the input of the first electronic switch 6, the output of the second control trigger 12 is connected via the second electronic switch 7, the integrator 10 and the third zero-organ 5 to the control input of the analog-digital converter 16, as well as to the single inputs the third 13 and fourth 14 control triggers, the output of a third of its control trigger 13 is connected. to the second input of the third electronic key 8, the output of the fourth control trigger 1 is connected to the second input of the integrator 10 via the fourth electronic key 9, the second input of which is grounded. In addition, the output of the second control trigger 12 is connected to the Iulevo input of the third trigger 13.

ten

0

five

P

0

0

five

five

management Terminal The measurement is connected to the zero input of the first control trigger 11. The output of the comparison circuit 15 is connected to the single input of the second control trigger 12, the second input of the second electronic key 7 is connected to the reference source, voltage U ,,.

It is known that the coefficient of asymmetry can be defined as follows:

and.

TO

is

5 where and „and C

 ™. 100%

Ui

"Mate

,100%,

2 max

respectively, the effective and amplitude values of the negative sequence voltage; the effective and amplitude values of the voltage of the direct sequence,

The operation of the device is based on the fact that the voltage of the direct sequence reaches the level U per inter and

 Max

time shaft

and"

Ul

Ma icc

((fig, 2) sinQ t,

Over the same interval of the reverse t, the negative sequence voltage will reach the level of y2MoiKcSi COt,

Looking at these stresses, we get the asymmetry coefficient

five ,

and U aTc sInUt U aKc I,

Choosing the reference level of voltage, we get

ms

TO

4 max

and

NA

100% -, 100% and%,

- i / ycKt: c Un

Thus, to determine the asymmetry factor, it is necessary to measure the time t for which the voltage of the direct sequence reaches the reference level B, and after the same time interval measure the instantaneous value of the voltage of the negative sequence. This value will be numerically equal to the asymmetry factor in percent.

The device works as follows

In the initial state, the control triggers 11-14 are in the zero state, with the electronic keys 6-9 closed-g. When you click the Measurement button, the first trigger 11 controls

51

single state

set to

and opens the first electronic key 6. A pulse at the output of the null body 3 at time tj will pass through the first electronic key 6 and set the first control trigger 11 to the zero state, and the second control trigger 12 to. single In this case, the first electronic key 6 is closed, and the second electronic key 7 connects the integrator 10 to the source of the reference voltage U. The voltage on the integrator 10 (Fig. 2) begins to increase linearly.

At time t, when the voltage of the direct sequence and (t) reaches the level U, the comparison circuit 15 will operate and with its impulse return the second control trigger 12 to the zero state. In this case, the second electronic key 7 will disconnect the integrator 10 from the source U. On the integrator 10, a voltage U «at proportional to time is detected. After disconnecting the electron rag 7 from the source U. the voltage and will be stored on the integrator 10 of the craze, the falling edge of the trigger 12 of the control the third trigger 13 of the control is transferred to one state. At the same time, the third electronic key 8 opens. At the instant tj of the transition of the negative sequence voltage across the zero value, the second zero-body 4 is triggered. Its output impulse through the third electronic key 8 sets the fourth control trigger 14 to one state. In this case, the input of the integrator 10 is through the fourth electrolyte. switch 9 is connected to potential / ground. The voltage across the integrator 10 will begin to decrease linearly. This voltage reaches the zero level at the moment of Bp (iMeHH, i.e. by that time (when the instantaneous value of the negative sequence voltage is equal to the unbalance factor. This triggers the third zero-body 5 and starts the analog-to-digital converter 16 on the conversion of the instantaneous value of the voltage at the output of the negative sequence filter 2 into a digital code. A code proportional to: asymmetry coefficient, fixed register 17,

ten

five

five

20

The maximum measurement time (with equal initial phases) does not exceed

Claims (1)

one and a half periods of the signal under study. Invention Formula A device for measuring the asymmetry coefficient in three-phase networks, containing direct and reverse sequence filters, two null organs, three electronic keys, a comparison unit, an analog-to-digital converter, a register, and three triggers, and my and reverse sequences are combined and are the inputs of the device, the output of the direct sequence voltage filter 15 is connected to the input of the first null organ and the first input of the comparator unit, the second input of which is connected to the reference voltage terminal And the output is connected to the zero input of the second trigger, the output of the negative sequence voltage filter is connected to the information input of the analog-digital converter, the output of which is connected to the register input, and the outputs of the first and third triggers are connected to the control inputs of the first and third electronic keys, characterized in that, in order to increase reliability and simplify, the device additionally contains a fourth electronic key, a third null-body, a fourth trigger and an integrator, with the output of the first zero-op through the first key is connected to the eleventh input of the second trigger and to the zero input of the first trigger, the unit input of which is connected to the Measurement terminal, the output of the second trigger is connected to the single input of the third trigger and the control input of the second electronic key, through which the reference voltage terminal is connected to the first input of the integrator, the output of which, through the third null-organ is connected to the control input of the analog-digital converter, zero inputs of the third and fourth triggers, 0 filter output nap negative sequence voltage through the serially connected second zero-body and the third switch is connected to the single input of the fourth flip-flop, whose output is connected to the control input of the fourth electronic switch through which a second input terminal of the integrator is connected to ground. 0 five 0 five and. () i ti ij tv IG