RU1798739C - Device for detecting emergency operation of three-phase power networks with insulated neutral - Google Patents

Abstract

Usage: relates to test equipment and can be used for non-contact determination of the emergency state of a three-phase electrical network associated with the presence of overvoltage in one of the phases, or with the absence of current flow in the phase. Summary of the invention: the device contains three sensors magnetic field, four phase-shifting units, two threshold amplifiers, an amplification unit, six two-input logic elements I. pulse shaper, information display unit, three-phase rectifier. 3 ill.

Description

The invention relates to the field of measurement technology and can be used to detect the presence of an emergency condition associated with either overvoltage or the absence of current flow in one of the phases in a three-phase electric network with isolated neutral.

The aim of the invention is:

- increasing the electrical safety of personnel during operation and maintenance of the device;

- improving the reliability of power supply to consumers of a three-phase network and eliminating the influence of the device on indicators of the quality of electricity, as well as technology for using the device.

On Fig, 1 shows a structural electrical diagram of the device; figure 2 explains the principle of operation of the device when one of the phases is broken; Fig. 3 explains the principle of operation of the device during overload in one of the phases.

In FIG. 1 shows a device for detecting the presence of emergency operation in

three-phase electrical networks with insulated neutral.

The device includes a first 1, a second 2; third 3 magnetic field sensors, first 4 and second 5 phase-shifting units, first 6 and second 7 threshold amplifiers, amplifier unit 8, third phase-shifting unit 9, first 10, second 11, third 12, fourth 13, fifth 14. sixth 15 two-two the common logic elements AND, the fourth phase-shifting unit 16, the pulse shaper 17, the information display unit 18, and the three-phase rectifier 19.

The scheme works as follows.

The signals from the magnetic field sensors D1, D2, and D3, which are proportional to the current changes in phases A, B, and C, are fed to the corresponding inputs of the amplification unit 8. From the output of the amplification unit, the signals are fed to the input of a three-phase rectifier 19, where they are nonlinearly superposition and rectifier opinion. From the output of the three-phase rectifier, the signal enters the inputs of the threshold amplifiers 6 and 7. From the output of the first threshold amplifier 6, the signal enters

(L

G

xj yu

oo m s u

to the first inputs of the two-input logic elements And 10, 11, 12. The signal from the output of the second threshold amplifier 7 is fed to the first inputs of the fourth, fifth and sixth two-input logic elements And 13, 14, 15. At the second inputs of the third and sixth logic elements And 12 and 15 receives a signal from the pulse shaper 17; to the second inputs of the second and fifth 11 and 14 and the first and fourth 10 and 13 of the logic elements 1/1, the signal from the pulse shaper 17 enters through the phase-shifting blocks 16 and 9, respectively, and the phase-shifting circuits shift the input pulses by T / 3 each.

The input of the pulse former 17 receives signals from the sensors D1, D2 and D3, and the signal D1, passing through the first phase-shifting unit 4, receives a phase shift of 240 °, and the signal from the sensor D2, passing through the second phase-shifting unit 5, receives a shift in 120 ° phase. Thus, the signals from the sensors D1, D2 and D3 are fed to the input of the pulse shaper 17 in-phase.

At the output of the pulse shaper 17, a pulse appears every time a signal passes through zero at a positive derivative; therefore, the output pulse frequency of block 17 will be 50 Hz. In this way, the operation of the logical part of the device is synchronized with the three-phase network.

In the event of a break in any of the phases, a signal is generated in the form of a pulse at the output of threshold amplifier 6. This signal is supplied to the first inputs of the first, second and third two-input logic elements 1/110, 11, 12, to the second inputs of which are received:

- to the third logical element 12 — a pulse from a pulse shaper 17;

- to the second logical element 11 — a pulse with a shift by T / 3 from the fourth phase-shifting block 16;

- to the first logical element TO - a pulse with a shift of 2T / 3 from the third phase-shifting unit 9.

The signal at the output of the first, second, and third logic elements 10, 11, and 12 will take place when there is a signal from the threshold amplifier 6 and an etrobing pulse corresponding to a certain phase from the pulse shaper 17. So, when phase C is interrupted, the signal goes across the logic output element 12 - the operation of the device in this situation is illustrated in Fig. 2.

In the event of an overload in one of the phases, a signal in the form of a pulse is generated at the output of the threshold amplifier 7. This signal is fed to the first inputs of the fourth, fifth and sixth logic elements 13, 14 and 15. To the second inputs of these

gate elements receive gating pulses with phase shifts described in a breakage situation. The signal about phase A overload will be generated by the fourth logical element And 13, when phase B is overloaded - at the output of the fifth logical element 14, when phase C is overloaded - at the output of the sixth logical element 15 - the principle of operation of the device during overload in phase C is explained in FIG. .Z.

Claims (1)

5 The selection of thresholds for threshold amplifiers 6 and 7 is carried out according to the maximum and minimum acceptable voltage changes in phases A, B and C. 0 A device for determining the presence of an emergency mode in three-phase electrical networks with an isolated neutral containing an information display unit, which, in order to 5 to increase the level of electrical safety and reliability of power supply, three magnetic field sensors, four phase-shifting units, two threshold amplifiers, six two-input logic elements 1L, a pulse shaper, an amplification unit and a three-phase rectifier are introduced into it, and the outputs of the first and second magnetic field sensors are connected accordingly, with the inputs of the first and second phase-shifting blocks and the first and second inputs of the amplifier block, the third input of which is connected to the output of the third magnetic field sensor, to the outputs the first and second phase-shifting blocks and the input of the pulse generator, the output of which is connected to the first inputs of the third and sixth two-input logic elements And and the input of the fourth phase-shifting block, the output of which is connected to the first inputs5 of the second and fifth two-input logic elements And and the input of the third phase shifting unit, the output of which is connected to the first waters of the first and fourth two-input logic elements 1/1, 0 the second inputs of the first, second and third two-input logic gates And are connected to the output of the first threshold amplifier, the input of which is connected to the output of the three-phase rectifier and to the input of the second threshold amplifier, the output of which is connected to the second inputs of the fourth, fifth and sixth two-input logic elements And, the inputs of the three-phase rectifier are connected to the corresponding outputs of the amplification unit, the inputs of the unit display information connected magnetic field is rigidly fixed to with the outputs of the corresponding two-in-equal distance from the phase wire logical elements And, sensors. L AND % and 4 AT 4 L t9 -J cpue.j