SU1149341A1 - Protective de-energization device - Google Patents

Abstract

A SAFETY SHUTDOWN DEVICE containing a leakage current sensor connected in series and an amplifier associated with an actuator, characterized in that, in order to increase reliability by suppressing short pulses of interference, a single-vibrator element with an inverse mounting input and a threshold converter are introduced into it, the input of which is connected to the output of the amplifier, and the output - to the triggering and inverse setting inputs of the one-shot and the first input of the element And, the second input of which is connected to the inverse output m monostable, the output of AND gate is connected to the actuator body. (L 4; oo 4

Description

The invention relates to electrical engineering and can be applied to protect against earth leakage currents. A device for protective tripping is known, comprising a load current sensor, a unit responsive to the rate of change of the load current, a leakage current sensor, a maximum leakage current unit, an integrator, a threshold unit, a switching unit, a coupling capacitor and a unit responsive to an increment of leakage current 1. However The device has insufficient performance, as the signal delay occurs in the integrator. A device for protective disconnection is also known. It contains a zero-sequence current sensor connected in series, an actuator mounted on a two-winding relay, one of the windings of which is connected to a rectifier and the other to a constant voltage source through a series-connected dynistor and a capacitor the point of the latter is connected via a diode with a voltage divider connected in parallel with the source of the constant voltage 2. However, the known device has a low noise immunity. ivost, since the sequence of interference pulses can cause false triggering. The purpose of the invention is to increase reliability by suppressing short pulses of interference. The goal is achieved by introducing an AND element, a one-shot with an inverse mounting input and a threshold converter, the input of which is connected to the output of the amplifier, and the output - to a device for protective disconnection containing a leakage current sensor connected in series and an amplifier connected to an actuator. to the triggering and inverse installation inputs of the one-shot and the first input of the element And, the second input of which is connected to the inverse output of the single-vibration, while the output of the element And is connected to the performer Nome body. FIG. 1 shows a diagram of the proposed device; in fig. 2 - time diagrams that show his work. The device (Fig. 1) contains a leakage current sensor 1, an amplifier 2, a threshold converter 3 of a two-pole signal into a unipolar signal, a one-shot 4 with an inverse mounting input, element 5, an executive element 6. A leakage current sensor 1, an amplifier 2 and a threshold converter 3 bipolar signals in unipolar are connected in a consequently. The output of the threshold converter 3 is connected to the triggering and inverse setting input of the one-vibrator 4, as well as the first input of the element 5, the second input of the element I connected to the inverse output of the one-vibrator, and the output of the element AND connected to the actuator 6. The leakage current sensor serves as a zero-sequence current transformer , the amplifier can be performed on t () anzistors or on a microcircuit. The bipolar-to-unipolar signal threshold converter 3 at the transistor and zener diodes is powered by a unipolar power source and does not require high stability of the supply voltage, since the thresholds here are determined by the voltages of the zener diodes. Using a simple power source makes such a converter more reliable than a converter at a two-threshold comparator. A one-shot with a setup input is performed on logic chips. Element And can be performed on diodes, transistors or logic chips. The executive body can serve as a relay, thyristor or triac key. The device works as follows. A voltage proportional to the leakage current to earth is fed from the leakage current sensor 1 to the amplifier 2. If a leak occurs from the contact of a person with current-carrying parts, the voltage at the output of the amplifier Uyc. has the form of a network voltage (fig. 2a). For this case, the voltage at the output of the amplifier exceeds the thresholds of Unir for the threshold converter 3 of the two-pole signal to unipolar from the moment tj is touched until the moment t2 and from the moment is- In this time interval, the UHC voltage appears on the output of the threshold converter (Fig. 26), which gives permission for the operation of the one-shot 4 through the inverse installation input and at the same time starts it via the trigger input. The single-oscillator generates prohibitive pulses, S, whose duration to achieve speed is chosen an order of magnitude less than the period of the mains voltage (Fig. 2c). After the end of the inhibit pulse at the output of the element AND, the MIS voltage (Fig. 2d) appears, which causes the actuator to operate. Interference to the device for protective tripping occurs when the load is switched in the protection zone and is a sequence of two-pole short leakage pulses Uy, the duration of which does not exceed several tens of microseconds, but the number can reach several hundreds due to unstable discharges in the contact switch of the load switch at the time of shutdown (Fig. 2d). The amplitude of the interference pulses can significantly exceed the level of the useful signal, so a sequence of short Unn pulses appears at the output of the threshold converter of the bipolar signal into the unipolar signal (Fig. 2f). These pulses trigger the one-shot, however, the inhibit pulse does not have time to form to the end, because the short triggering pulses, when finished, transfer the one-shot, to the initial state on the setup input. Thus, the one-shot in this case works like

inverter. FIG. 2g shows the voltage form at its output of an ultrasonic signal. Since the inputs of the element I receive signals that are inverted relative to each other, there is zero voltage at its output.

Thus, the proposed device provides the suppression of all short pulses of interference, which significantly increases the reliability of the device during its operation.

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Claims (1)

DEVICE FOR PROTECTIVE CIRCUIT BREAKING, containing in series a leakage current sensor and an amplifier connected to an actuator, characterized in that, in order to increase reliability by suppressing short interference pulses, an I element is introduced into it, a one-shot with an inverse installation input and a threshold converter, the input of which is connected to the output of the amplifier, and the output to the triggering and inverse installation inputs of the one-shot and the first input of the And element, the second input of which is connected to the inverse output of one vibrator, the output of AND gate is connected to the actuator body. SU „„ 1149341>