SU769457A1 - Device for measuring the ratio of two electric values - Google Patents

Description

one

I The invention relates to the field of electrical measuring equipment i and can be used to create ycov. for detecting short-circuit locations on power lines.5

Devices are known for measuring the ratio of two electrical quantities, comprising two reference storage capacitors included in the circuit of the compared electrical quantities.

charged to voltages proportional to these values; analog-to-digital voltage converter in the form of a capacitor and a switch included in the storage circuit of the terminal 15

the capacitor and producing the discrete discharge of the storage capacitor to aaziamioro level, and the pulse counter, count the number of discharge cycles of the storage capacitor, which is 20

is a function of the ratio of monitored electrical quantities.

In these devices, the number of pulses recorded by the counter is the lo-tariff function of the ratio of

roll values In order to obtain a linear dependence of the meter readings on the fixed electrical quantities and increase the accuracy of the known device of this type, the voltage converter is equipped with a DcnoMioraTejibHoro voltage capacitor level control element, the output circuits of which are included in the circuit between the auxiliary capacitor and the circuit capacitor. increasing the voltage on the auxiliary capacitor to a value proportional to the voltage value on the second storage capacitor. In addition, to improve operating accuracy, the converter is supplemented with a source of stabilized voltage l

With this design, the device is complicated by the introduction of additional stabilized sources of shaking, a device for controlling the voltage level, and, in addition, it can be performed only with the use of an analog-to-digital aerator unit as a reference unit. In a number of cases, when performing relay protection devices and determining distances to short circuit sites, simpler report blocks 1 are used, based on the measurement of the time interval. Such devices also contain reference memory capacitors, included in the circuit of controlled values, the elements of dividing and fixing the ratios of these quantities. In them, the ratio of the indicated values is measured by the charge time of the capacitor in the integrating PC-ape connected to the capacitor, the voltage on which is proportional to the line current, to the level of the comparable voltage on the second reference capacitor proportional to the voltage between the damaged phases of the line. The live time in these devices is also related to the ratio of the monitored values to the logarithmic dependence. In order to obtain a linear dependence of the charge time of a capacitor of an RC circuit on the ratio of monitored values in a known device G21 containing a voltage transformer, a trans-reactor, rectifying bridges, a comparison circuit and a zero indicator, an additional zero indicator is used. from the side of the current circuits is connected to the resistance divider, and the main null indicator from the side of the current peaks is connected to the divider-dif-divider. of the fermenting circuit of the comparison circuit, connected to the top of the current circuit bridge through the closing contact of the additional-null indicator. In ETSZh1, to measure the time var in the linear part of the characteristic, the capacitor charge is used not to the full voltage on the reference memory capacitor, to its part defined by the divider. The disadvantage of the device is the low accuracy of operation, the deviation from the linearity of the output characteristic is 20% even when the capacitor is charged up to 0.5 of the supply voltage. In order to eliminate this drawback, increase the accuracy of work, improve the linearity of the output characteristic when performing the fixation of the ratio of the controlled electrical (values with ps dell time block | A reference device containing the source of direct and alternating current, the starting relay with output disconnecting and closing contacts is a current transformer, the primary winding of which is connected to the power line under investigation, and the external coil is shunted by a load voltage and a primary rectifier, a voltage transformer , the primary winding of which is connected by a test transmission line and the secondary winding of which is connected, the second rectifier, the null organ, the time reference block, is executed Solo relay, first memory capacitor, resistors, - a second memory capacitor, a charge capacitor and a diode are inserted, the second and second memory capacitors are connected to the output terminals of the first and second rectifiers, respectively, through the corresponding closing contacts of the starting relay, the second capacitor the memory of the hpc are series-connected C0 (respectively: the closing contact of the starting relay and the first resistor are connected to the first input of the zero-body, the charging capacitor and the diode are turned on | through the first resistor parallel to the repetition of the memory capacitor, the first capacitor of the memory is connected to the second input of the nullorgan through the corresponding closing contact of the starting relay, between which the second resistor is connected and one of the buses of the direct current source; contact of the starting relay; And the coil is connected to the bus of the source of direct current, and one pin is a temporary reference unit (Connected to one of the buses of the source of alternating current, the second is chic The corresponding starting contact of the start relay and the opening contact of the executive relay are connected in series with another output of the temporary reference block, and the transistor equivalent of a two-base diode is used as the zero-organ .An diagram of the device consists of current transformers 1 and voltage 2, rectifying bridges 3, 4, load resistor S.sanoMHHaicnupfx (capacitors b, 7, charge capacitor I

jcaTOpa 8, charge resistor 9, discharge resistor 10, diode 11, output contacts of the starting relay 1217, transistor equivalent of a two-base diode at transistors 18, 19, executive relay 20 with the output contact 21, time reference block 22, starting device 23. The circuit works as follows. When the starting relay 23 is triggered, its contacts 12, 13 connect storage capacitors 6, 7, respectively, to the output terminals of the rectifying bridges connected to the secondary windings of current transformers 1 and voltage 2. Condenser 6 C p is charged to a voltage

K .. 1, Proportional to the current line 1, and the capacitor 7 - to the voltage,

proportional voltage ling M. After a time delay,

required for charging the indicated capacitors, the contacts are triggered. At the initial moment after nej .. switching contacts 14, 15 the potential of the base of the transistor 18 is higher than the potential of the emitter, while the transistors Ts8, 19 are closed. These tranonsts are provided, provided that:

U

,

R

(one)

eight

ten,

s: t /.

where: w - voltage on kondeyu-a

torus 8, i ,. surge voltage

resistor 10. Voltage 1 /. got tired of it utoa8

life:

.)

(2)

8Cg

where: C, CQ - respectively

bo

capacitors 6 and 8, G - constant time

p yes capacitor 8,

6-s

6 8

Voltage is defined by:

69457

6 | G t

 T)

where: G - constant time circuit times52

p yes capacitor 7;

 ..,

and

Substituted the values of Q and

C8

from (2), (3) in a) the condition of unlocking transistors 18, 19 can be represented as:

that

At t, but

G. -of

(7)

At wc 2, 1 within t T, the deviation of this dependence from linear does not exceed 2%, i.e.

Jk BUT.

(eight)

l

Thus, the proposed device provides an increase in the accuracy and linearity of measurement of the ratio of counter / wired values. At the same time, it is characterized by simplicity of execution and can be used when using simple temporary reference blocks.

Claims (1)

1. USSR author's certificate Ni 420967, cl. G 01 R 31 / O8. 2, USSR author's certificate ., cells, N. 1: 02 N c / s, 05.05.69, (prototype).