SU995023A1 - Symmetrical component meter - Google Patents

Description

The invention relates to electrical measuring equipment, namely, devices for measuring voltages and currents of forward and reverse sequences of a three-phase electrical network.

A device is known for isolating symmetric components of the direct and reverse sequences of a three-phase network, which consists of active-inductive arms, connected directly to the phases of the network fl. The disadvantage of this device is the error due to the higher harmonics of the network.

The closest in technical essence to the invention is a device for measuring symmetric components of a three-phase electrical network, which consists of two channels containing series-connected transformers, filters of symmetric components, selective converters including a selective amplifier, rectifier and combiner, and A switch, a divider and frequency converters in voltage 12.

A disadvantage of this device is the low accuracy of converting the fundamental harmonic HffK of the symmetric component into a constant voltage, which is determined by the temperature and time instability of the samples of the selective amplifiers. Therefore, the selective converter contains the main converter path, the correction path, the chopper, the scale converter.

10 and pulse shaper. The operation of the selective transducer is based on the synphasicity of the measured and reference signals, which is in the absence of a phase shift in the transducer, which is powered from the same signal source that feeds the pulse shaper.

However, the phase shift angle of the three-component voltage component at the high-pass filter of the symmetric components varies widely (from 0 to 360, and the filter output signal of the symmetric components is polyharmonic, and the higher harmonics often exceed the levels of the symmetric components All this leads to the fact that at the input of the comparison path the signals of the first harmonics of the symmetric components of the symmetrical components from the filter output and the reference voltage from the output of the large-scale converter receive a shift They are not necessary to ensure the operation of the selective converter in the normal mode, but at any other angle (from -1G to 4GG. There is no phase shift compensation compared to the comparison signal in the reference path, which leads to the appearance of a voltage the path amplifier. The comparison is rectified by a synchronous detector, and through a low-pass filter is applied to the adder, as a result of which the stabilization mode of the entire device is violated. In this case, the selective converter stops functioning or works with a large error. The aim of the invention is to improve the accuracy. The goal is achieved by the fact that the symmetric component meter, which contains a symmetric filter component and a selective converter, consists of the measuring path, the comparison path of the chopper, the scale converter and the pulse shaper, the source of the three-phase voltage is connected to the filter inputs symmetrical output components are connected to the inputs of the measurement path and the comparison path, the output of which is connected to another input of the measurement track, the output of which is through an interrupter and the scale converter is connected to another input of the comparison path, and the output of the pulse shaped body is connected to the second one. the input of the chopper and the third input of the comparison path, connected in series by a circular phase shifter, a selective amplifier, and a phase conjugate unit of 1C / 2. multiplier, filter, low pass, comparator and executive unit; the first input of the circular phase shifter is connected to one of the network phases, the second input is connected to the output of the executive unit, the output of the filter of the symmetric components is connected to the second input of the multiplier, and the output of the selective amplifier is connected to the input of the pulse former. The drawing shows a block diagram of the device. The symmetrical component meter consists of a symmetrical component filter 1 and a selective device consisting of the main measuring path 2, interrupter 3, three-phase voltage source 4, comparison path 5, scale converter 6, circular phase shifter 7, selective amplifier 8, phase shifter unit 9 on / 2, submultiplier 10, generator 11 pulses, executive unit 12, low-pass filter 13 and comparator 14. The main measuring path 2 consists of series-connected selectively Amplifier 15, amplitude detector 16 and adder 17, and the comparison path 5 contains a series-connected subtractor 18, a band-pass amplifier 19, a synchronous detector 20 and a low-pass filter 21. The meter works as follows. The output signal of the filter 1 is amplified in the main measuring path 2 by a selective amplifier 15 tuned to the main harmonic of the three-phase voltage, and rectified by an amplitude detector 16, then fed to the first input of the adder 17, to the second input of the adder 17, which is also different the input of the main measurement path 2, a signal is output from the low pass filter 21, which is also the output of the comparison path 5. The totalizer signal from the output of the adder 17 is fed to the input of the chopper 3, which is controlled by the signal from the output of the formate 11 pulses. The meander from the output of the chopper 3 is divided by the large-scale converter b to K times, where K is the nominal value of the gain of the main measuring path 2. The output signal of the large-scale converter 6. goes to the first input of the subtractor 18, which is the third input of the comparison path 5, to the second the input of the subtracting device (the first input of the comparison path 5 receives a convertible signal from the output of the filter 1 of symmetric components. Due to the presence in the comparison 5 path of the selective amplifier 19 signal; If the transmission coefficient of the main path is equal to the nominal value of K, then the differential voltage of the first harmonic at the output of the readout device 18 is absent. When the transfer ratio of the main path 2 from the nominal value at the output of the detractor 18 and, therefore, at the output of the path5 in comparison with Vits, the differential voltage supplied to the second input of the adder 17, which compensates for the voltage increment of the main path 2. To operate the selective conversion circuit the driver needs the frequency and phase shift of the output voltage of the formative 11 to coincide with the frequency and phase shift of the first harmonic of the converted signal, the equal frequency of the signal is fed to the filter 1 directly, and to the shaper 11 through the phase divider 7 and the selective amplifier 8 from one and the other the same source 4 three-phase voltage

compensation of the phase shift between the first harmonics of the signals from the output of the filter 1 and from the output of the large-scale converter 6 is performed by changing the initial phase angle of the signal at the output of the phase shifter 7 and, respectively, at the outputs of the selective amplifier 8 and the phase-shifting block 9, as well as at the input of the driver 11 pulses. This is achieved in that the result of multiplying the input signal of the former 11, turned by Ha tr / 2 by the phase shifter 9, and the output signal of the filter 1 in the form of a constant voltage through the low pass filter 13, the 11 mutator 14 and the executive unit 12 is fed to the control phase shifter input 7.

If the first harmonic vectors

multiplied signals are shifted by

1C / 2, then at the output of the multiplier 10

just a component of avna zero

C-K O Oj K UjSWio-tU ei C ()

-K tsi4eh 5 (: in: | a) "- so5 (). .СОБХ11 "Part-1); (1)

about output voltage over multiplier

K is the multiplier conversion factor;

„..

and. tI ,, U, and are the corresponding instantaneous and effective values of the multiplied stresses. The variable-component of the output signal of the transponder is suppressed by the low-pass filter 13. Thus, at the input of the comparator, the voltage is absent and the execution unit 12, controlled by the phase shifter 7, is not included in operation. In this case, the signal at the input of the driver 11 is in phase with the output signal of the filter 1.

When a phase shift occurs between the first harmonics of the signal to be converted and the signal from the output of the former 11, a constant voltage appears at the output of the filter 13 connected to the multiplier 10.

Ugj ,, x i «(- &)) 51i (ЛL 4 1) dt ° fV. (t uf) co5i (2uL -.-) Za -CU1U ,, (1)

where and

output voltage

1 filter 13,

LU is the phase angle between the vectors of the first harmonics of the voltage being converted and the voltage Hai of the output of the driver 11.

A constant voltage from the filter 13 is supplied to a comparator 14, which operates according to the level and sign of this voltage, and starts the execution unit 12, the signal of which acts on the phase shifter 7 so as to compensate for the phase shift angle.

Thus, additionally introducing into the meter the symmedaric components of the phase shifter 7, the selective amplifier 8, the phase-shifting unit 9 by 2, the low-pass filter 13, the comparator 14 and the executive unit 12 makes it possible to accurately wipe out the symmetrical components. :: In addition, it makes it possible to “measure the phase angle of the meidau by the measured signal from the output of filter 1 and any of the voltages of the source 4 of the three-phase voltage, for which from the output of the infrasor tshro phaser as a signal proportional to the angle of phase shift between the probe and reference voltage, sufficient to lead to the measuring instrument, pro-, graduated in degrees. This allows refusing the manufacture of additional phase-metering devices, makes the device based on the proposed device more universal and increases the efficiency of its use.

Improving the accuracy of measuring symmetric components and building devices with enhanced functionality based on the proposed technical solution contributes to improving the quality of electricity and, as a consequence, reducing the economic damage caused by the receiver of electrical energy and the poor quality of the latter.

The economic effect from the introduction of devices on the basis of the proposed technical solution, when fully meeting the needs of the national economy, will be about 10 million rubles. Due to the use of the proposed technical solution in the device 43204, the latter has the following advantages as compared with the known device F 433C, produced for measuring indicators of the quality of electric power: 10

5 times less accurate than 3

dimensions and weight, higher manufacturability, and also equipped with a digital display.

Claims (2)

Invention Formula A symmetric component meter containing a symmetric component filter and a selective converter consisting of a measuring path, a comparison path, a chopper, a scale converter and a pulse former, the source of the three-phase voltage is connected to the filter inputs of the first components whose output is connected to the inputs of the measurement path and the comparison path, the output of which is connected to another input of the measurement path, the output of which is connected through an interrupter and a scale converter another input of the truck, that comparison, a shaper output pulses coupled to a second input the interrupter and the third inlet of the comparison path, characterized in that, in order to improve the accuracy, a series-connected circular phase disconnect is introduced into it, selective amplifier, phase rotation 1NY block on TE / G, multiplier, low pass filter, comparator and / execution unit, the first input of the circular phase shifter is connected to one of the network phases, the second input is connected to the output of the execution unit, the output of the filter / balanced The co-generators are connected to the second input of the primultiplier, and the output of the selective force (the bodies are connected to the input of the former: pulses. Sources of information taken into account during the examination 1. Fabricator V.L. Filter-symmetric components, SEI, 1962, p. 100-106, 2. USSR author's certificate №517860, class, G 01 R 29/16, 1976,