SU1725311A1 - Three-phase current relay - Google Patents

Abstract

The invention relates to the field of electrical engineering, in particular to devices for relay protection of electrical installations. The purpose of the invention is to increase speed. The goal is achieved by the fact that the device claimed The device contains a current sensor 1 (DT), which consists of current transformers 2 (CT), diode rectifying bridges 3, resistor k, the first comparator 5, the second comparator b. novibrators 7 and 8, the logic circuit And 9. TT2 installed in the grooves of the controlled network. The secondary windings of CT 2 are connected to the outputs of diode rectifying bridges 3 and their outputs are interconnected in series. Resistor k is set to. Output DT 1 and connected in parallel from diode rectifying bridges 3- The inputs of the first comparator 5 and the second comparator 6 are connected to the output of the DT 1, and the outputs of the one-oscillator 7 and 8 are connected to the OUTPUT of the first comparator 1 and 8, and the outputs of the second comparator 6 and one-shot 7 and 8 are connected to the inputs of the logic circuit And 9 Relay triggers when the amplitude of the short circuit current exceeds the current settings of k / to LED SD

Description

17253П

the first and second comparators, if the time interval between the trigger times of the comparators does not exceed the difference in pulse durations generated: at the outputs of the corresponding single-oscillators triggered by the output signal of the first comparator. 3 il.

The invention relates to low-voltage electrical apparatus, namely, AC semiconductor relays, in particular, being part of the overcurrent release of circuit breakers.

A three-phase alternating current relay is known, which is also the closest to the claimed device техническойlj by its technical essence.

The known device contains a current sensor, made in the form of current transformers installed in the network phases, the first terminals of diode rectifying bridges are connected to the secondary windings, and a resistor is connected in parallel to the circuit from the series-connected second pins of the diode rectifier-bridges is the output of the current sensor to which the input of the first comparator is connected.

A disadvantage of the known device is the low speed, since its current setting should exceed the amplitude of the starting current in the network, the multiplicity of which to the amplitude of the rated current can exceed 10-15 (for example, if the network is powered by powerful transformers or asynchronous motors). The consequence of this is the deterioration of the protective characteristics of the circuit breakers in which the devices are used.

The purpose of the invention is to increase speed.

The goal is achieved by the fact that in a three-phase alternating current relay containing a current sensor, made in the form of current transformers installed in the phases of the network, to which the windings are connected, the first terminals of the diode rectifier bridges are parallel to the circuit from series-connected second pins of diode rectifying bridges included

50

0 5

five

a resistor, one of the terminals of which is the output of the current sensor to which the input of the first comparator is connected, due to the additional input of the element I, two single-oscillators and the second comparator, the latter connected between the output of the current sensor and the first input of the element And, the inputs of the first and second single-oscillators connected to the output of the first comparator, and the outputs to the second and third inputs of the element I, respectively, while the duration of the pulses of the first and second single-oscillators is proportional to the difference between the settings atyvani first and second comparators and obratnoproportsio- onal maximum possible speeds m swells inrush current and short circuit in the network Correspondingly venno-1.

It is due to the fact that the second comparator is introduced into the relay, two single-vibrators and the element I, which are respectively connected with each other and with the other elements of the circuit, and with the corresponding durations of the pulses of the single-vibrators, an increase in speed is achieved;

Fig, 1 shows the functionality of a three-phase alternating current relay; Fig. 2 shows current and voltage timing diagrams explaining the operation of the relay during a short circuit in the network; in fig. Figure 3 shows the timing diagrams of the current and voltage, explaining the operation of the relay when the inrush current flows in the network.

The three-phase alternating current relay (Fig. 1) contains a current sensor I, made in the form of current transformers 2 installed in the network phases (ia, ifc ic phase currents of the network flowing in the primary windings of the current transformers 2), to the secondary windings of which inputs are connected first conclusions) diode.

25

bridges 3, in parallel with a circuit of series-connected outputs (second pins) of diode rectifying bridges 3, a resistor k is turned on. one of the terminals of which is an output. current sensor 1, to which the inputs of comparators 5 and 6 are connected, the output of comparator 5 is connected to the inputs of one-shot 7 and 8, and the outputs of switch 6 and one-shot 7 and 8 are connected to the inputs of element 9, the output of which is a relay output .

Elements can be implemented on the basis of typical principal 15 hemes, for example, given in source 2JV

Relay three-phase AC operates as follows. When an overload current flows in any of the 20 phases of the network, the voltage across the resistor k of the current sensor 1 appears proportional to the maximum of the phase shackles. The operation of the comparator 5 occurs when the maximum of the phase currents 14 (current 1 in Figures 1 and 3) exceeds the response setpoint.

Frequency ratio of the setpoint to the amplitude of the set nominal. , - the mains current is approximately equal to 2. The operation of the comparator 6 occurs when the maximum of the phase currents 12 is exceeded, the response setpoint. The current ratio of a setpoint of 1% to the amplitude of a steady-state rated mains current is approximately equal to 3. Thus, the following relation is used in the circuit, in setpoints

& i G40

G,.

When triggered by a comparator 5 in.

time instant tr (see figs. 2 and 3) at its output a voltage U, of a high level appears abruptly. When the comparator 6 is triggered (at time t-j in Fig. 2 and t in Fig. 3), a high level voltage U appears in its output at a jump. The leading edge of the voltage U is started up by the single-oscillators 7 and 8. This leads to the appearance at the output of a single-vibration 7 of a high-level voltage pulse Us having a duration b, and to the appearance at the output. : 55 one-shot 8-pulse low voltage U4, having a duration Cj ..

These pulse durations of the one-shot 7 and 8, if we take a constant increase rate of V4 of the maximum phase current, i in the time interval between the times of the comparators 5 and 6, must satisfy the following inequalities:

I2-Ii - ... V

B nvn

five

five

0

-

0

- 0

Where

one

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V.,

i- "

12-Ii

V.

the maximum possible rate of increase of the starting current in the network, in the time interval (,), per FHz. 3; the maximum possible rate of increase of short circuit current in the network in the time interval (C-t)., FIG. 2..

A high-level relay U5 triggered signal appears at the output of the And 9 element while simultaneously present on all three inputs of the element. And 9 voltages, high level. The condition for the operation of the relay is to satisfy the inequalities

 . ; v ::.:; .

-. v. ::;: ..:

where Im is the amplitude of the current i.

This condition is satisfied only when a short circuit current flows in the network, i.e. when the operation of the comparator 6 occurs during the action of the pulse of the selector 7, but already at the end of the time of action of the pulse of the one-shot 8 (in the time interval in Fig. 2). Blocking the operation of the relay for the duration of the action of the pulse of the one-shot 8 is used to increase the noise immunity of the relay.

When the inrush current flows in the network, the following inequalities are fulfilled:

iw. -; ..; -.

v - vnrn;

in this case, the operation of the element 9 and the relay does not occur, since the comparator 6 is triggered after the end of the action of the pulse of the one-vibrator 8 (see voltage diagrams U2 and and in Fig. 3).

This principle can also be used to create a high-speed single-phase AC relay (in this case, current sensor 1 replaces three times the number of current transformers 2 and diode rectifying bridges 3 using a single quantity) and when creating a high-speed direct current relay. case, instead of the AC sensor 1, a DC sensor is used).

Thus, compared with the RZ prototype, the claimed device has a faster response — the relay is triggered after the network current i increases to a value r, which is about 5 times less than the amplitude of the starting current, which is the trigger setting of the prototype relay.

Claims (1)

Invention Formula Three-phase alternating current relay containing a current sensor, made in the form of current transformers, by the number of phases of the network, to the secondary windings the first pins of the diode rectifying bridges are connected, a resistor is connected in parallel from the second pins of the diode rectifying bridges connected in series, one of which is the output of the current sensor to which the input of the first comparator is connected, characterized in that, in order to improve speed, an And element is additionally introduced, two single vibrators and a second comparator, the latter is connected between the output of the current sensor and the first input of an And element, the inputs of the first and second single vibrators are connected to the output of the first comparator, and outputs the second and third inputs of the And element, respectively, while the pulse durations of the first and second single-oscillators are proportional to the difference in the settings of the second and first comparators and inversely proportional to the maximum possible rates of rise of starting current and short circuit current in the network, respectively.