SU1239616A1 - Device for measuring power - Google Patents

Abstract

The invention relates to electrical engineering and can be used in power supply automation devices and relay protection. The purpose of the invention is to show measurement accuracy. The device contains a multiplier 3, a differentiator 4, a zero-body 5, shapers 7 and 8 pulses and cells 9 and 10 of the sample and storage. Introduction to the device of voltage and current converters 1 and 2, respectively, of inverter 6 and adder 11 reduces the impact on the measurement accuracy of the phase errors of the differentiator 4 and null-op 5, which in turn differs from storage and storage cells 9 and 10 from the true moment of the extremum of the input signal. 2 Il. W to with co O) a

Description

eleven

The invention relates to the field of electrical engineering and can be used in automatic power supply and relay protection devices.

The purpose of the invention is to improve the measurement accuracy.

On f ig ig. 1 shows a block diagram of the proposed device; in fig. 2 time diagrams of his work.

The device contains scale converters 1 and 2 voltage, respectively, multiplier 3, differentiator 4, null organ 5, inverter 6, form 7 and 8 pulses, cells 9 and 10 of sampling and storage, adder 11.

The inputs of the multiplier 3 are connected to the outputs of the large-scale converters 1 and 2, and the output is connected to the input of the differentiator 4 and the inputs of the cells 9 and 10 of the sample and storage, the outputs of which are connected to the inputs of the adder-11, and the control inputs through the drivers 7 and 8 pulses to the outputs of the inverter 6 and the zero-organ 5. The input of the zero-organ 5 is connected to the sup- port of the differentiator 4, and the output to the input of the inverter 6. The output of the adder 11 is the output of the device, and the inputs of the scale converters 1 and 2 are the inputs of the device.

The device works as follows.

The voltage at the output of the multiplier 3 (Fig. 2b) can be described

by formula

Ua, j K UIcoSCfu-Ulco5 (2a) tfq) yf, y

where and is the effective value of the voltage (Fig. 2q); I - the effective value of current

(Fig. 28); - phase shift between current and

stress;

0 - angular frequency of the network; K - coefficient of proportionality.

The maximum value of this voltage

 aymcix

(2)

is reached at cos (2 ω t + P) -1 The minimum value of this voltage

t a4m; n "ulco5Cpu-Ul (3)

is reached at cos (2 el t + (c) -1.,

five

0 5 o

five

Q

,

0

five

162

SUMMING (2) and (3), GET b, 2KU co5Cp ,. Teach the gea that UI cos

those. active power we get

biaxially, the sum of the positive and negative amplitudes of the output voltage: an analog multiplier is proportional to the measured active power.

In accordance with the described algorithm, the voltage from the output of multiplier 3 is supplied to the information inputs of two cells 9 and 10 of sampling and storage. Cells 9 and 10 also have a control input; when a narrow negative control pulse is received on it, the voltage stored at the information input is memorized. To generate control pulses at the moments when the output voltage of the multiplier 3 reaches its maximum and minimum values, differentiator 4 is applied. The voltage at its output, (Fig. 2) d is shifted by 90 relative to U. and does not contain a constant component. From the output voltage of the differentiator with the help of a null-organ of which the integral comparator can be applied, square UHQ pulses (Fig. 2) are formed from the fronts of which, using the driver 7, control pulses are generated and A.c 1 (Fig. 2g) for 10 sampling and storage cells. The voltage is inverted by the inverter 6 and from the voltage fronts at the output of the inverter 6 U (Fig. 2e), the control pulses Uau2 (Fig. 2j) for the sample and storage cell 9 are generated by the shaper 8. The inverter 6 allows the use of the cells 9 and 10 sampling and storage with identical control circuits. The stored voltages from the outputs of the cells 9 and 10 of the sample and storage (Fig. 2ts, k) are fed to the inputs of the adder 11 whose output voltage (Fig. 2L) is proportional to the measured active power.

Another mode of operation of the device is also possible, in which the adder 11 performs the subtraction of voltages from the outputs of the sample and hold cells 9 and 10. In this case

1 output acg "k-1 aup,; n 2Ki1 2K5,

those. total (apparent c) power is measured.

The proposed device is more precisely known at practically the same speed by reducing the influence on the measurement accuracy of the phase errors of the differentiator 1 and the zero of the organ 5, expressed in difference between the moment of activation of the sampling and storage cells 9 and 10 from the true moment of the extremum of the input signal. In the proposed device, in the temporal neighborhood of the moment of extremum of the output signal of the multiplier 3, its changes are small, while in the known device when building a voltage proportional to the current of the circuit under study at: the moment of the voltage extremum of the circuit under study, the rate of increase of the voltage The sampled signal can be large, which leads to a large effect of the phase errors of the differentiator and the zero-organ on the measurement result.

one

2

VNIIPI Order 3390/44 Circulation 728 Subscription

Random polygons pr-tie, Uzhgorod, st. Project, 4

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l 2 25

2396164

F, formula of invention

A device for measuring the power of large-scale current and voltage transducers, whose inputs are device inputs, a multiplier, two sampling and storage cells, a zero-organ and a differentiator, the output of which is connected to the zero-organ input, and with the inputs of the sample and storage cells, differing in that, in order to improve the measurement accuracy, an adder, an inverter and two pulse makers, the outputs of which are connected to the control inputs of the corresponding sample and storage cells, are connected to the outputs with corresponding etstvuyuschimi adder inputs, whose output is the output device, the inputs connected to the outputs of multiplier scale converters current and voltage, and the output - to the input of a differentiator, pulse shaping inputs connected to the output zero-body directly and through an inverter, respectively.

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Claims (1)

Claim Device for measuring power _; containing large-scale current and voltage converters, the inputs of which are device inputs, a ♦ multiplier, two sampling and storage cells, a zero-organ and a differentiator, the output of which is connected to the input of a zero-organ, and the input - with the inputs of the sampling and storage cells, different the fact that, in order to improve the measurement accuracy, an adder, an inverter and two pulse shapers are introduced into it, the outputs of which are connected to the control inputs of the corresponding sampling and storage cells, connected by the outputs to the corresponding inputs of the adder, One of which is the output of the device, the inputs being the voltage extremum moment of the circuit under study, the rise rate of the gated signal can be large, which leads to a large influence of the phase errors of the differentiator and multiplier connected to the outputs of the scaled current and voltage converters, and the output to the input of the differentiator , the inputs of the pulse shapers are connected to the output of the null-ohr · null-organ to the result of the measurement directly and through an inverter