SU476633A1 - Safety shutdown device - Google Patents

Description

one

The invention relates to the field of electrical engineering, in particular, to protective disconnecting devices (AEDs) designed to ensure the safety of service personnel during the breakdown of network insulation and human contact with live parts of electrical installations.

Protective disconnection devices are known that disconnect electrical installations from a power source in the event of a breakdown of the insulation and human contact with live parts of an electrical installation.

Such devices respond to the rate of change of the amplitude of the periodic signal. These devices contain a capacitor amplitude measurement unit and a reacting organ, to the input of which an additional measurement unit is included opposite to the measurement unit, both of which contain readout and thickening units for the voltage accumulated over half the period.

A disadvantage of the known device is that when damage occurs at certain points in time, an additional deceleration is introduced into the operation of the device, corresponding to an industrial current frequency of 20 msec. In addition, after the device is triggered, it can be reactivated by the absence of conditions that correspond to emergency mode in a controlled network.

The proposed device differs from the known ones in order to increase reliability

a comparison unit, made in the form of a time selection element connected to the secondary winding of a matching transformer, connected to an element of the duration of the comparison and connected to

two keys, the outputs of which are associated with the actuator, are connected to a reset unit containing a reset duration element connected to the capacitor selection elements for resetting, the outputs of which

connected to the reset key; the common point of these keys is connected to the common point of the capacitors, which in turn is connected to the midpoint of the matching transformer, and the other ends of the keys are connected via diodes to the secondary terminals of the transformer and other inputs are connected to these terminals capacitor selection elements for reset. This inclusion of elements provides

The fact that the device makes a gradual comparison of each previous and subsequent half-wave voltage at the output of the sensor and when they change, resulting from a breakdown of the isolation or contact of a person, disables the installation, not allowing dangerous current to flow through the human body. FIG. I given the scheme of the proposed device; on fng. 2 is a timing diagram illustrating the operation of the device. The protective disconnecting device contains a voltage sensor 1, a matching transformer 2 with a midpoint on the secondary winding, diodes 3, 4, capacitors 5, 6, reset unit 7, reset keys 8, 9, selection elements 10, 11 of a capacitor for reset ( ), reset duration element 12, comparison unit 13, comparison duration element 14, comparison keys 15, 16, comparison time selection element 17, actuating element 18. Transformer 2 performs matching of the signal from sensor 1 to device units and provides get s two voltages in phase opposition. Capacitors 5 and 6, using rectifying diodes 3 and 4, store the amplitude values of the positive and negative half-wave signals for later comparison. The keys 15 and 16 connect the capacitors 5 and 6 to the actuator 18, which compares the levels of pressure on them. Keys 8 and 9 alternately reset the already-compared voltage level. The capacitor selection circuits 10 and 11 control the reset keys 8 and 9. Element 17 selects a comparison time instant. Element 14 defines the duration of the comparison time and controls the keys 15 and 16. Element 12 gives a command to reset the voltage. During normal network operation, the positive and negative half-waves of the voltage are equal and the storage capacitors 5 and 6 are charged to the same level. Therefore, when these capacitors are connected to the actuator 18 at the output, its voltage is zero. If a person touches one of the mains phases or closes the phase on the body, there is an instantaneous change in the sensor signal (in Fig. 2, time point tj), i.e. the increase or decrease in the amplitude value of the half-waves. The capacitor charged from the first modified half-wave gets a higher or lower voltage level compared to the voltage across the capacitor charged by the previous half-wave. The connection in this case of storage capacitors to the actuator 18 leads to the appearance of a disconnect signal at its output. Consider the functional operation of the elements of the proposed device. At time ti for a positive half wave and ti; for negative, the comparison time element circuit 17, which, at a time interval At, when the storage capacitors 5 and 6 are charged to the amplitude value of the corresponding half-waves, feeds an impulse to the duration element 14, is started. and the storage capacitors 5 and 6 are connected to the outputs of the actuator 18. When the voltages on the storage capacitors are equal, the voltage at the output of the actuator is zero. If the inequality is at the output of the actuating element 18, a signal appears. The duration of the comparison Ati is specified by element 14. At the end of the comparison, at time t4, the keys 15 and 16 disconnect the capacitors from the actuator. At the same time, element 14 commands the element 12, which commands the capacitor selection elements 10 and 11 to reset the voltage from the capacitors. The voltage is reset from a capacitor charged by the previous half-wave. Elements 10 and 11 are also controlled by half-waves of controlled voltage. When simultaneously commanding the element 12 and the secondary winding of the matching transformer 2 at one of the coincidence circuits 10 or 11, the switch 8 or 9 switches on and drops the voltage from one of the capacitors. The allowed discharge time At2 is determined by the element of the reset unit 12. The invention includes a protective disconnect device comprising a voltage sensor connected to a matching transformer, the secondary winding of which has a midpoint, an amplitude memory capacitor unit, a comparison unit, a reset unit and an actuator characterized by in order to increase reliability, the comparison unit, made in the form of a comparison time transformer element connected to the secondary winding connected to an element of the duration of the comparison and connected to two keys whose outputs are connected to the actuator, connected to a reset unit containing the element of the duration of the reset connected to the capacitor selection elements for resetting, the outputs of which are connected to the reset keys and the common point of these keys the common point of the capacitors, which in turn is connected with the middle point of the matching transformer, and the other ends of the keys are connected via diodes to the secondary terminals of the said transformer, connected to these pins and other input elements for selection of capacitors is reset.

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