SU1647417A1 - Device for touch voltage and step voltage measurements - Google Patents

Abstract

The invention relates to a technique for measuring and monitoring parameters of earthing switches when operating in electrical networks. The purpose of the invention is to increase the accuracy of measuring the voltage of touch and pitch. The controlled object is connected via terminals 4, 5 and attenuator 6 to the amplitude voltmeter inputs 7, 8, periodically whipped by using button 9. Polarity determining unit 10 with inputs 10.1-10.4 and outputs 10.5-10.8 using electronic switches 12 13 and the electronic polarity switch 14 switches the indicating device 15 to the amplitude voltmeter outputs 7, 8 and the polarity indication of the half-wave input voltage. The 1t button sets the polarity determination unit 10 to the initial state. 4 il.

Description

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The invention relates to a measurement technique, namely, devices for measuring the voltage of touch and pitch in industrial premises with electrical equipment with a voltage of up to 1 kV, in particular, at livestock breeding complexes.

The purpose of the invention is to improve the measurement accuracy,

1 shows a diagram of the device; Fig. 2 is a schematic diagram of the polarity determination unit of the first half-voltage-voltage of touch and pitch from the start; Fig. 3 and A show diagrams of the distribution of potentials at the control object.

The device for measuring the voltage of touch and pitch (Fig. 1) contains a full-wave switch 1 with a control unit and terminals 2, 3 connections, as well as a pulse voltmeter separated from the switch, containing an input terminal 4, 5, an input signal attenuator 6, amplitude voltmeters positive 7 and negative 8 polarities, the inputs of which are connected to the output of the attenuator 6, the dual reset button 9 of the amplitude voltmeters 7 and 8, the polarity block 10 first from the beginning of the half-wave voltage closure neither the touch and the pitch, inputs 10.1 and 10.2 of which are connected respectively to the outputs of amplitude voltmeters 7, 8, button 11 connected to inputs 10.3 and 10.4 of the polarity determination unit 10 for setting it to its initial state, controlled from outputs 10.5 and 10.6 of the unit 10 electronic switches 12, 13, the signal inputs of which are connected to the outputs of the amplitude voltmeters 7, 8, and the outputs are combined and connected to the input of the electronic polarity switch 14, the output of which is connected to the indicating device 15 connected to the outputs 10.7 and 10.8 of the block 10 defined neither polarity elements 16, 17 of the indication of the presence or absence of metal communication between the neutral conductor of the network and the metal structures of the production room (not shown).

The polarity determination unit 10 (Fig. 2) contains an adder on the operational amplifier 18 and resistors 19,20,21, differentiating the positive polarity circuit formed by the capacitor 22 and the input resistance of the composite transistor 23,24, a negative polarity differential circuit 25 and the input impedance of the two-stage amplifier on

transistors 26, 27, RS-flip-flop on logic elements 28.1 and 28.2. RS flip-flop on logic elements 28.3 and 28.4, transistor switches 29,30,31,32, dual button 11.1,11.2 to set the polarity detection unit to its original state.

The essence of the operation of the device is based on taking into account the occurrence of a reversal of the phase of touch voltage and consists in

next.

On modern livestock farms and farms, in accordance with the applied milking technology, watering, cleaning of the premises, various

metal structures laid in the ground or connected with it (water supply, metal fencing of stalls, manure conveyors, etc.), which in essence are extensive horizontal grounding conductors. In order to improve electrical safety, all metal structures must be reliably connected by conductors between themselves and the neutral wire of the network. Such a connection significantly reduces the voltage of touch and pitch by reducing the potential on the metal structures and leveling the potentials in industrial premises. However, in practice, metal communication between zero

network wiring and metal constructions of industrial premises are often absent. In such cases, the occurrence of the polarity of the first from the beginning of the closure of the half-wave voltage of the touch and pitch (phase reversal) arises. An overview of the cause of the phase reversal in the simplest example (see FIG. 3), when two parallel horizontal stretched 33, 34 are laid in the production area, the first of which is metallicly connected to the neutral conductor of the network, and the second is not connected to it . In a single-phase short circuit, the first grounding current flows into the field

which is the second earthing, the electrical potential of which is equal to the potential on the surface of the earth. Fig. 3 shows the potential distribution for the case described.

The potential distribution of y on the earth’s surface around a circular horizontal earthing with a circular cross section along the y axis is described by the well-known expression

h

1k.3.-p, - „, w2u

P

where p is the soil resistivity: I is the length of the earth conductor;

1k.z. short-circuit current flowing from the earth conductor.

In general, the contact voltage is equal to the potential difference of the metal structure to which the person or animal touches and the plate that simulates the feet of a person or the hoof of an animal (the plate is located 0.8 m from the metalwork). As can be seen in FIG. 3, when measuring the voltage of the contact between the grounding 33 () and any point on the surface of the earth in which the plate 35 is located (p3}, the voltage of the contact

Unp1-3 p - {b 0.

In this case, the polarity of the first from the beginning of the short circuit of the half-wave of the touch voltage is always positive, since

When measuring the voltage of contact between the grounding 34 (pi) and point

36 (p h)

Unp2-3 pl 0

Consequently, the polarity of the first from the start of the closing of the half-wave of the touch voltage is also positive, so

as (pi rz

However, when measuring voltage between grounding 34 and point 35

U pr2-3 P2 - RZ O

and, therefore, the polarity of the first from the start of the closing of the half-wave of the contact voltage is negative, since pi 0. those. a reversal (tilting) of the touch voltage phase is observed.

Let us consider a picture of the distribution of potentials on the earth's surface near two extended horizontal ground gels. metallic bonded to each other. As can be seen from Fig. 4, the polarity of the first from the beginning of the closure of the half-wave of the touch voltage is always positive, since

p rz, pi rz. p rz, pi rz. Consequently, in this case there is no reverse (overturning) of the touch voltage phase. Thus, the first from the start of the closing, the half-wave voltage of the touch has a negative polarity only in the case when the metal structures do not have a metallic bond between them. Therefore, the short circuit should be made by a half-half-cycle switch, and the voltage of the touch and pitch should be measured in the second half period

regardless of their values and sign, which is implemented in the device.

The device works as follows.

After connecting the full-wave switch 1 with the control unit via terminals and 3 respectively to phase F and the zero wire of network 0, an artificial short circuit of two half-periods of the mains voltage occurs, and to terminals 4 and 5 connected respectively to the plate imitating a human foot or The animal's hooves, and the metal structures of the production room, are applied to the voltage of a touch or pitch. Next, the attenuator 6 voltage, touch or step voltage, is fed to the amplitude voltmeter inputs 7, 8, the readings of which

0 is reset by the reset button 9 before the measurement is started. If there is a metal wire between the neutral wire of the network and the metal structures of the production room, the first half of the touch and pitch waveform has a positive polarity in accordance with the accepted setting of the control unit of the thyristor switch and is remembered as amplitude

0 voltmeter 7 positive polarity. When the metal is absent, the first from the beginning of the closure, the half-wave voltage of the touch has a negative polarity and is remembered by the amplitude

5 voltmeter 8 negative polarity.

From the output of the amplitude voltmeter 7

or 3 voltage goes to input 10.1

or 10.2 polarization determination unit 10

the first from the beginning of the closure of the half-wave on the touch and step springs. Before the measurements are started, the block 10 is reset to its original state by the button 11.1, 11.2, while the elements 16, 17 of the indication of the presence or absence of metal communication, connected

5, respectively, to outputs 10.7, 10.8 of block 10, are canceled, and electronic keys 12 and 13 are closed. At the time of the appearance at the output of one of the voltmeters 7 or 8 voltage, respectively, of positive or negative polarity (determined by the presence or absence of metal communication), the control signal of the electronic key 12 or 13 is generated at the output of the polarity detection unit 10, depending on

5 polarity of the first from the beginning of the closure of the half-wave voltage of touch and pitch. At the same time, the display element 16 or 17 is ignited, indicating the polarity of the first half-wave voltage of the touch and pitch from the beginning of the circuit, and

consequently, the presence or absence of metal connection between the neutral conductor of the network and metal structures that may be touched by people or animals. The electronic key 12 or 13, opened by the control signal from the polarity determination unit 10 and the electronic polarity switch 14, receives the second half-wave voltage of the touch to the indicating device 15. This ensures the measurement of the touch voltage and the step voltage in the second half period regardless of their values and sign. Thereby, the errors of measuring the voltage of touch and pitch are excluded both from the free (aperiodic) components and from the magnetization of the steel elements of the phase-zero circuit, as a result of which the total measurement error does not exceed 5%.

When determining the polarity of the first from the start of the closing of the half-wave of the contact voltage, the unit 10 (Fig. 2) works as follows.

If the first from the beginning of the closing the half-wave of the contact voltage has a positive polarity (in the presence of metal communication), then the voltage is applied to the input 10.1 of the adder on the operational amplifier 18, from the output of which the ventilation voltage is supplied to the positive polarity differentiating circuit, the transistors 23, 24 open and the RS flip-flop on elements 28.1 and 28.2 goes to the second steady state, at the output of element 28.2 a logical 1 signal appears that opens transistor switches 30, 31. When opened And the transistor switch 31 ignites the metalwork indication indication element 16 (Fig. 1) connected to the output 10.7. An open transistor 30 blocks the input of a two-stage amplifier at transistors 26, 27, while the second negative half-voltage touch voltage does not change the first (initial) state of the RS flip-flop on elements 28.3 and 28.4. At the output of the element 28.4 there is a logical O signal, therefore, the transistor switch 32 is closed, and the element 17 for the absence of metal communication, connected to the output 10.8, is canceled. At output 10.5 of element 28.1 there is a logical O signal, and at output 10.6 of element 28.3 there is a signal of logical 1, while the electronic key 12, the control input of which is connected to output 10.5, is open, and the electronic key 13, the control input of which is connected exit 10.6, closed.

If the first from the beginning of the closure, the half-wave voltage of the touch has a negative polarity (no metal connection), then the voltage is applied to

the input 10.2 of the adder on the operational amplifier 18, from the output of which the inverted voltage is fed to the differentiating circuit of the negative polarity of the capacitor 25, while

the transistors 26, 27 open and the RS flip-flop on elements 28.3, 28.4 goes to the second steady state, the output of element 28.4 is a logical 1 signal, which opens the transistor

keys 29 and 32. When opening key 32, element 17 of the absence of metal communication is switched on, connected to output 10.8. The open transistor 29 blocks the input of the composite transistor 23, 24, with

By this, the second negative half-wave voltage of the touch does not change the first (initial) state of the RS flip-flop on the logic elements 28.1 and 28.2. At the output of the element 28.2 there is a logical O signal, therefore, the transistor switch 31 is closed and the element 17 for the indication of the presence of metal communication is extinguished. At output 10.5 of element 28.1 there is a logical 1 signal, and at output 10.6 of element 28.3 a logical O signal, while the electronic key 12, the control input of which is connected to output 10.5, is closed, and the electronic key 13, the control input of which is connected to output 10.6 , open.

The fact that the device has the ability to detect the absence of metal communication between the neutral wire of the network and the metal structures of the production room allows to establish one of the main reasons

reduction of electrical safety due to violation of the rules and regulations of electrical installation, which leads to an increase in touch voltage by 5-10 times.

45

Claims (1)

Invention Formula A device for measuring the voltage of touch and pitch, containing a double-wavelength switch with a control unit and terminals for connecting to the test object, a pulse voltmeter with terminals for connecting to the test object, and showing a device that it has an attenuator, a polarity detection unit, two display elements, two electronic keys, an electronic polarity switch, a dual reset button, a dual button, and a pulse voltmeter contains an amplitude A positive voltmeter of positive polarity and an amplitude voltmeter of negative polarity, the first inputs of which are connected to the output of an attenuator, the input of which is connected to terminals for connecting a test object, the reset inputs of amplitude voltmeters of negative and positive polarity through a dual reset button connected to a common wire, and their the outputs are connected to the first inputs of the polarity determination unit and the inputs of the elec Ш 19 0 key switches, the control inputs of which are connected to the first outputs of the polarity determination unit, the second outputs of which are connected to the inputs of the corresponding indication element, the second inputs of the polarity determination unit are connected via a double button to the common wire, the outputs of the electronic switches are combined and connected via an electronic polarity switch with the input of the indicating device FIG. 2 31 Fig.Z Fy