SU1665453A1 - Device for identification of phase of three phase circuit having reduced resistivity of insulation - Google Patents

Abstract

The invention relates to the field of electrical engineering and is intended for use in insulation resistance monitoring devices, as well as to protect a person from electric shock when touched to one of the phases of an electrical network with an insulated neutral and electrical contact with the ground. The aim of the invention is to increase the sensitivity of the device. With normal and symmetrical insulation resistance of the network phases, the neutral bias voltage is small and the phase voltage shift angles are close to each other. At that, pictransformers 1, 2, 3 trigger triggers 4, 5, 6 at equal intervals of time and after converting them to voltage by blocks 7, 8, 9, mini-selector 10 does not select the greatest voltage. In case of failure of the insulation resistance of one of the phases, the shear angle of the voltage of this and the lagging phase increases relative to the other shear angles of the phase voltages. In this case, the mini selector 10 selects the faulty phase and includes one of the corresponding executive bodies 11–13. 2 Il.

Description

ABOUT

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The invention relates to electrical engineering and is intended for use in insulation resistance monitoring devices, as well as to protect a person from electric shock when touched to one of the phases of an electrical network with an insulated neutral and electrical contact with the ground.

The aim of the invention is to increase the sensitivity of the device.

Figure 1 shows the structural scheme of the proposed device for the determination, no phase with reduced resistance.

isolation in a three-phase network; FIG. 2 shows a functional scheme of a variant of the max-selector.

The device contains connected to each phase of the electrical network and the earth peak transformers 1-3, the output of each of which is connected to the trigger input R + S - triggers 4-6 of its phase and to the reset input j of the trigger triggers 4-6. The output of each of the flip-flops 4-6 is connected to a functional transducer 7-9 of the time interval-voltage type, the outputs of which are connected to the Ymax-selector unit with output phases 11-13 at the output.

In accordance with FIG. 2, a power selector unit 10 contains analog to digital converters 14-16, to the outputs of which memory registers 17-19 are connected. Digital comparators 20-22 are connected to the outputs of each pair of these registers, To the direct output of the comparator of its phase and to the inverse output of the comparator of the advanced phase of the device are connected elements And 23-25, the outputs of which are connected to the control inputs of the respective actuators.

The device works as follows.

With normal and symmetrical resistances of the insulation1 of the phases of the electrical network, the bias voltage of its neutral is small, the shear angles of the phase voltages of the network relative to the earth are close to one another. Peak transformers 1-3 trigger triggers 4-5 at time intervals close to a third of the alternating current period. Elements 7-9 generate voltages that are proportional to the specified intervals and are close in value, as a result of which unit 10 of the high selector does not select the largest of the voltages and does not generate the corresponding output signal.

With a decrease in the insulation resistance of one of the phases, in particular due to the contact of a person with contact with the ground, the angle of stress shift of this and the lagging phase

increases with respect to the other two phase shift shear angles. Peak transformers 1–3 start one of the triggers 4–6 for a time longer than the others, as a result of which the voltage at the output of the corresponding driver 7–9 exceeds the output voltages of the two other drivers.

Functional output signals

0 converters 7-9, proportional to the angles of displacement of the mains phase voltages relative to ground, in analog-digital converters 14-16 (Fig.2) are converted into a digital code and stored in registers

5 17-19 memories. After updating the contents of each memory register 17-19 in digital comparators 20-22, a pairwise comparison of the digital codes of the signals of its own and lagging device phases is performed. If a

If the difference between the codes exceeds the fixed threshold, then, depending on the sign of this difference, the output signal at the forward or inverse output of the comparator 20-22 is obtained. At the two entrances of one of the elements And 23-25

5, single signals are present if the voltage of the shaper of a given phase exceeds not less than a fixed value of the voltage of the output signals of the shapers of the remaining phases of the device.

0 Single output of this item

And will trigger the executive

phase element corresponding to the network phase

with reduced insulation resistance.

Depending on the purpose of the proposed device, the actuator short-circuits to the ground phase with a reduced insulation resistance or turns on the signaling of this phase for a short time.

Technical and economic efficiency

0 of the invention consists in the high efficiency of human protection devices against electric shock in networks with insulated neutral and signaling a decrease in the insulation resistance of the phases, which

5 is due to the high sensitivity of determining the phase with reduced insulation resistance by comparing the phase angle of the voltage of the electrical network to the ground.

0

Claims (1)

Invention Formula A device for determining the phase with reduced insulation resistance in a three-phase network, containing 5 executive elements and sensors for measuring phase voltages according to the number of phases of the network, each of which has terminals for connecting to the phase of the network and ground, the output of each sensor measuring the phase voltage connected to the installation input of the corresponding a trigger, characterized in that, in order to increase the sensitivity, three functional time interval-type converters — voltage and a max-selector — are added, the outputs of which are connected to the corresponding actuators, and the first, the second, third inputs are connected via corresponding functional converters of the time interval - voltage type with the trigger outputs, the Reset inputs of which are connected to the output of the corresponding phase voltage measurement sensor of the lagging phase. 1