SU600653A1 - Voltage relay - Google Patents

Description

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The invention relates to the field of relay protection and automation of power systems.

High-speed relays are known that are based on the principle of comparing a rectified value with a reference voltage. These devices contain a rectifier and, as a reacting organ, a threshold organ or ilul organ 1.

It is known a voltage or current relay containing a measuring transformer with a rectifier on the secondary side, the diagonal of which is connected via a charging circuit to a measuring capacitor, a discharge circuit, an executive element whose controlled inputs are connected in parallel to a measuring capacitor, a stabilized intani source, to the outputs which is connected pulse-potential converter 2.

This relay is the closest to the described invention to the technical essence and the achieved result.

Its disadvantages are that the voltage on the measuring capacitor depends on the capacitance and resistance of the leakage of the measuring capacitor, which changes with temperature, as well as the greater consumption of the measuring signal and control of the average signal value.

The aim of the invention is to provide speed and accuracy of measurement by analyzing the effects of capacitance instability and leakage resistance of the measuring capacitor.

This is achieved by the fact that in the proposed charging voltage relay circuit is made in the form of a quadrant, and the actuating element is made on interrogating and switching transistor, connected in series, the collector of the opposite transistor is connected to the input of the above-mentioned pulse-emitter converter, the emitter switch. the output of the said wiring of the receiver and with the negative pole of the said stabilized power source, and its base is connected via resistors to the negative The virtual output of the rectifier is the positive pole of a stabilized Pitapp voltage source connected through a discharge circuit to one of the plates of the pointing measuring capacitor.

FIG. Figure 1 shows the IRP of the proposed voltage relay; on phpg. 2 - graphs of the patterns between different points of the circuit; in fig. 3 is a plot of the current flowing through the charging resistor from the nanowire of the rectifier output of the measuring signal.

CoDtrAtE: Measurement Transformer 1 with PRESSER 2 on the secondary side; stabilized source 13 pita-ni, built on the zener diodes 4, 5 and the ballast resistor 6; measuring capacitor 7; charge day, made in the form of a quadrant, consisting of a resistor 8, connected in series with a resistor 9, a shunting zener diode 10; a discharge circuit in the form of a resistor 11; An additional element 12, performed on interrogating 13 and switching 14 transistors connected in series. The collector of the polling transistor is connected to the input of the pulse-potential converter 15. The emitter of the switching transistor 14 is connected to the positive terminal of the rectifier 2 and to the negative pole of the stabilized source 3 of the papapi. The base of the switching transistor 14 is connected via a resistor 16 to a negative output of the rectifier, through a resistor 17 to the positive pole of the power supply 3, and through a protective diode 18 to the emitter. The stabilized power source 3 is fed through a discharge circuit to one of the plates of the measuring capacitor 7.

Pulse-potential converter 15 includes a one-shot 19 and a time-potential converter, built on a capacitor 20, a diode 21, a Zener diode 22 and resistors 23 and 24.

Relay and marriage works as follows.

If there is no signal at the input of the voltage relay, i.e., on the Primary winding of the measuring transformer 1, which corresponds to the interval from O to / i in FIG. 2, the switching transistor 14 is permanently opened by the current to the base through the resistor 17; the voltage t / a-in between the collector and the emitter is approximately zero (see Fig. 2). The discharge current through the resistor 11 and the measuring capacitor 7 goes to the base of the polling transistor 13. The voltage on the capacitor 7 is constant and close to zero, the polling transistor 13 is constantly open and the voltage on the collector of the transistor 13 is constant and negative.

When a signal appears on the primary winding of the transformer 1 (from a current source or voltage) that is insufficient to operate the relay (ti-tz interval), the output of the rectifier 2 is the voltage t / a-e. The switching transistor 14 is locked with the current from the rectifier 2 through the resistor 16 and is opened briefly when the input signal is close to zero. Therefore, the voltage f / a-B most of the half-period is positive and only briefly zero. During the locked state of the transistor 14, no current flows into the base of the transistor 13 and it is locked; voltage is zero. In the measuring capacitor 7, the charge current across the charge circuit and the discharge current ltd discharge dn-syN resistor I.

As long as the input signal is not enough for the voltage relay to operate, the average current charge for the half period is less than the average value of the discharge current through the resistor I. Therefore, the voltage t / a-r on the capacitor 7 to the end of the half period becomes greater than zero. When the switching transistor 14 opens at the end of the half cycle, since the voltage on the capacitor 7 is positive, the interrogating transistor 13 opens and the capacitor 7 discharges along the base-emitter circuit of the transistor 13 to the collector-emitter of the transistor 14 to almost zero. An impulse drops below zero. This is how a pulse voltage survey is performed on a capacitor. The cycle is repeated during each ioloperiod if the input signal is insufficient to trigger the measuring organ.

When a signal appears on the input that is sufficient to activate the relay (the interval to the right / 2 in Fig. 2), the average current value

charge per half period is greater than the average value of the discharge current. At the end of the half period, the voltage L / a-r on the capacitor 7 is negative and when the switching transistor 14 opens briefly at the end of the half period, the polling transistor 13 remains locked. In this case, the measuring capacitor during the pulse polling is not discharged to zero. Voltage b / d e remains zero. Output voltage

the one-shot 19 is zero or pulses to zero (interval from O to t), while the voltage U is, & at its input, negatively or impulsively drops below zero, while Condeisagore 20 does not have time to charge up to the voltage of the Nrobot Zener diode 22, since this requires a time longer than the half-period of the measuring signal. And only when the voltage of the one-vibrator output is negative more than a half-period of the measuring signal (time interval to the right of r), the output voltage of the relay appears, i.e., it triggers (time tz). The time of operation of the voltage relay since the occurrence of a signal sufficient

for actuation, does not exceed 1.25 measurement signal period, since if the relay fails, at the end of each half-period, the measurement capacitor 7 is discharged to zero.

A change in the capacitance and leakage resistance of the measuring capacitor 7 does not introduce an error in the measurements, since at the moment of the relay and actuator response at the time of the survey the voltage across the capacitor 7 is almost

equal to zero, i.e., the zero voltage level is monitored and the measuring capacitor.

Energy consumption is reduced due to the fact that there is no need for a large pressure source and the output of the rectifier. This is due to the fact that the discharge current of the capacitor across the resistor 11 flows continuously and the oscillation voltage on the measuring capacitor is 10 times less with the same charge current than when the capacitor discharges only at the end of the half period; And the greater the multiplicity of the voltage at the output of the rectifier to the amplitude of the voltage on the measuring capacitor, the closer the average current of the charging circuit is to the required one (when the capacitor is short-circuited).

Due to the zener diode 10 and the resistor 9, the charging current varies with the output voltage of the rectifier, as shown in FIG. 3, which is an approximation of a parabola. therefore

/з(/)1.-b((1)

and the average current of charge per half period is equal to

g / 2g / 2

4. СР at fз (About d (Y (And df 66

 a-bef

where i / ab is the effective value of voltage

straightener; T is the period of change of the charge current; t is the time of operation of the voltage relay. In this way, the effective value of the measuring signal (current or voltage) is controlled while maintaining speed.

The scheme is simple and convenient when creating multistage sewn.

Claims (2)

1. USSR author's certificate No. 307458, cl. H 02 H 3/40, 1971. 2. A. P. Greivulis et al. Semiconductor current and voltage relays. M., “Energie, 1970, fig. 37.  : 7 oopopppp. Ud-e lgtgpg IITEJIZJI one J