SU1399850A1 - Arrangement for protecting man against electric shocks in mains with insulated neutral - Google Patents

Abstract

The invention relates to the field of electrical engineering and is intended to protect a person from breaking the isolation of a network with an isolated neutral. The purpose of the invention is to increase reliable performance. When a single-phase earth fault occurs, the number of phase currents increases dramatically, and this change is greater on the damaged phase. The increments of the phase currents are compared with each other on the Greater Amplifiers 10-15. After passing the signals through the single vibrators 16-21, where they are delayed and limited in duration to ensure excellent stability, they are fed to elements 2I 22-24 and ZI 25-27. Thus, only in the channel of the damaged phase simultaneously 1 will be collected at the inputs of the GD element, which triggers and outputs a signal to the corresponding switching element, thereby shorting the faulty phase to the substation grounding circuit. This device possesses high reliability of operation in conditions of substantial asymmetry of the network load and significant resistivity of the earth. 2 hp f-ly, 3 ill. S (l

Description

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The invention relates to electrical engineering, in particular, to devices for protecting a person from electric shock when the high-voltage insulation of a network phase with an insulated neutral is disturbed.

The aim of the invention is to increase the reliability of operation.

FIG. 1 shows the functional scheme of the device; in fig. 2 and 3 - electrical circuit diagram of the device.

A device for protecting a person from electric shock in a network with an insulated neutral contains sensors 1-3 of the phase current increments, which are current transformers, the primary windings of which are included in the corresponding phases of the network with an isolated neutral, hangers 4-6, assembled along a full-wave bridge a circuit with a smoothing capacitor, the inputs of which are connected to the secondary windings of current transformers 1 and 3, and the capacity value of the smoothing capacitors should be selected from the condition of 95% smoothing rectified signal, differentiating links 7-9, the inputs of which are connected to the outputs of rectifiers 4-6 of the corresponding phases, and the capacitance of the capacitors of differentiating links should be 3-4 times

less capacitance smoothing condensate35

tori, six operational amplifiers (comparators) 10–15, connected in pairs along direct inputs connected respectively to the outputs of differentiating links 7–9, and the reverse inputs of a pair of operational amplifiers 10 and 11 are connected to the outputs of links 9 and 8, respectively, the inverse inputs of a pair of operational amplifiers 12 and 13 are connected to the outputs of the 45 7 and 9 links, respectively, and the inverse inputs of a pair of operational amplifiers 14 and 15 are connected to the outputs of the 7 and 8 links, respectively, six 16-21 single-oscillators with a delay of the output pulse, Each time series connected by itself is connected to an RC circuit between which an inverter is connected, and in parallel with the resistance R of each RC circuit a diode is connected in the opposite direction to the charge current of the capacitor, whose inputs are connected to the outputs of the respective operational amplifiers 10-15 ,

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five

0 5 5

three elements 2I 22-24, the inputs are connected to the outputs of the corresponding 16-21 one-vibrators, three elements ZI 25-27, the first inputs of which are connected to the outputs of the corresponding elements 2I 22-24, and the second and third inputs - respectively to the outputs of the operational amplifiers 10 -15; three switching elements 28-30, which short circuit the faulty phase to earth, the inputs of which are connected to the outputs of the corresponding ZI elements 25-27.

The device works as follows.

At the moment to, single-phase ground fault (033), for example, phase A sharply increases the amplitudes of the line phase currents, and l 1 ((1). Sensors 1-3 respond to this by increasing the output signals in the ratio & U, U , j, uU, MJ,. The voltages of the signals at the outputs of the rectifiers 4-6 also increase, moreover (in Figs. 2 and 3, U, Uj, Ug are the voltages on the capacitors,,., respectively). The increase in the output voltages The signals of the rectifiers 4-6 cause the appearance of signals at the outputs of the differentiating links 7-9, with the voltage of the signals being in the ratio,, (in FIG. 2 and 3 are the voltages U, Ug, and, are the voltages on the resistors RA, respectively.) The signals generated by links 7–9 are fed to the corresponding inputs of the operational amplifiers (comparators) 10–15, which compare them. The operational amplifier ( SU) in this scheme works as follows:

at the output of the op amp will be

with, at the output of the OU will be Oh, where and. - signal voltage on the forward

OU input;

and - the voltage of the signal at the inverse of the OU.

At the moment tojj 033 of the phase A, according to (I), the signals 1 in the vehicle are at the outputs of OU 10 and 11, the outputs of OU 12 and 14 are O, the output of OU 13 is either 1 or O, the output of OU 15 lnbo O, or 1, depending on the ratio of the voltage values Ug, U. From the outputs of the OU 10 and 11, the signals 1 are fed to the second and third inputs of the ZI element 25 and to the inputs of the single vibrators (OB) 16 and 17, which are equipped with

This is at the output of O and temporarily unresponsive I. After a delay of G, on the gateways OV 16 and 17 there will be ONE single signals with a duration T. The delay of the occurrence of r and the limitation of the duration of the output signal Cj are necessary to ensure noise immunity. From the outputs OV 16 and 17, the single signal 39

399850

of the inputs of which are connected to the output of the corresponding time delay element, the outputs of which are connected to the inputs of the corresponding switching elements with leads for connection between the phase conductors of the network and ground, characterized in that, in order to increase the reliability of the pa

The first and second entrances of the bots arrive at it, it is equipped with six operating elements 2I 22 and from its output to the first entrance e, the cement of ZI 25. Then at time t + s, all three inputs of the corresponding phase A of the element of ZI 25 will be gathered I. the second input of the ZI element 26 corresponding to phase B, and at the second input of the element ZI 27 corresponding to phase C, in this case, O will be constant. Therefore, at the moment tp - T, only at the output of the element ZI 25 the outputs of the elements ZI 26 and 27 will be O. From the output of the element ZI 25 1 enters the input of the element 28 switching phases A, which srabatshaet zakorachi- and 25 respectively of the first and second ukavaet faulty phase A circuit grounding at the substation, and the switching elements 29 and 30 do not work. Thus, when a phase A is shorted to earth, the device reliably works, in the case of natural asymmetry of the voltages (currents) in the network, the device does not work, since in this case condition (1) does not fulfill. When other phases are shorted to earth, the device works in a similar way. The proposed device has a higher reliability of operation in conditions of significant asymmetry of the network load and a significant electrical resistance, therefore, it increases the electrical safety of people.

Claims (1)

Invention Formula It is complete in the form of two mono vibrators connected in series and element 2 I; the inputs of the mono vibrators are connected to the outputs of the corresponding OP1. A device for protecting a person from electric shock in a network with an insulated neutral, containing sensors for controlling increment - n Zionns: amplifiers, and the output of an element of a variable parameter in each phase circuit 2I is connected to the first input of the corresponding wire, ZI logic elements, one zi element. Amplifiers connected in pairs via gated inputs connected to the outputs of the corresponding sensors of the monitored parameter, the inverse inputs of the first phase of the operational amplifiers are connected to the outputs of the second and third specified increment sensors, respectively, the inverse inputs of the second pair of operational amplifiers are connected to the outputs of the first and second the second specified sensors increment, and the inverse inputs of the third pair of operational amplifiers are connected to the outputs These incremental sensors, the outputs of each pair of operational amplifiers are connected to two other inputs of the corresponding GI logic elements and to the inputs of the corresponding time delay elements, while the sensors of the monitored parameter are configured as phase current sensors. 2, the device according to claim 1, which is each such that the increment sensors of the monitored parameter are made in the form of a series-connected current transformer, rectifier, smoothing capacitor, and differentiating Even. thirty 3, The device according to claim 1, about tl, which is that each g of the time delay elements is made in the form of two single-vibrators connected in series and element 2 I, the inputs of the single vibrators are connected to the outputs of the respective op-amps, and the output of element 2I is connected with the first entrance Zionns: amplifiers, and in 2I connected to the first input zi element. A & C  ij L; QiQQ 0uz, Z W