RU2303329C1 - GENERATOR FOR INJECTING CURRENT SIGNALS INTO THREE-PHASED LOW 380V VOLTAGE LINE AT 50 Hz FREQUENCY - Google Patents

Abstract

FIELD: electric engineering, possible use during organization of communication channels using three-phased electric supply lines at 380V without processing by high frequency rejecters.

SUBSTANCE: invention is realized due to optimal selection of working frequency range with consideration of lengths of 380V lines, and also consideration of absence of harmonic interferences of 50 Hz frequency in selected frequency range.

EFFECT: 100 times increased transfer speed of current signals.

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Description

The invention relates to the field of electrical engineering and can be used in low-voltage lines 380 V for the formation of a communication channel at frequencies in the range (13-23) kHz, which is part of the security tele-alarm system of objects, which can be summer cottages, garages, retail outlets, etc. .d., where there is no telephone and radio communications with air traffic control.

A known generator of a passive-active type, which is designed to transmit current signals along the lines of (0.38-10-35) kV. The frequency range is selected taking into account the line lengths (10-35) kV.

Currently, the maximum current signal transmission rate that can be achieved in this frequency range (500-3000) Hz is 50 Bit / s, which is a drawback [l.1 p. 66].

A passive type generator is also known [l.1 p.108]. This generator is taken as a PROTOTYPE. The disadvantages of the PROTOTYPE are the same as for the ANALOGUE - low current signal transmission rate.

In a grounded generator for inputting current signals into a low-voltage line of 380 V, the signal transmission speed is increased by 100 times, and the channel itself is formed only by low-voltage lines of 380 V.

Distinctive features of the prototype.

1. In the claimed generator "input current signals" into the low voltage line 380 V "there is a blocking filter configured for a cutoff frequency of 300 Hz, which reduces the value of the sixth harmonic of a frequency of 50 Hz, so that the current at a frequency of 300 Hz through a closed key is zero, because attenuation at this frequency will be infinitely large.

2. The prototype cannot operate at frequencies above 3000 Hz without the installation of chokes due to the occurrence of wave processes due to the long line lengths of 10-35 kV.

3. For the operation of the inventive generator selected the optimal operating frequency range:

13 · 10 ³ Hz≤f ₀ ≤23 · 10 ³ Hz,

while the operating frequency band ΔF is equal to:

ΔF = 10 kHz,

which in turn made it possible to increase the signal transmission rate in the claimed generator in comparison with the prototype 100 times.

The drawing shows a diagram of a generator of current signals of a passive type (generator), which implements the claimed technical solution,

Where:

1. Three-phase two-half-wave rectifier bridge (bridge), which consists of diodes D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ .

2. The first resistor, R ₁ is its resistance.

3. The second resistor, R ₂ is its resistance.

4. The third resistor, R ₃ is its resistance.

5. The first capacitor, C ₁ - its capacity.

6. The second capacitor, C ₂ - its capacity.

7. The third capacitor, C ₃ - its capacity.

8. Managed key (key).

9. Barrier filter.

GENERATOR WORK

FIRST STATE OF THE GENERATOR

The blocking filter 9 is not connected to the output of the bridge 1 (points 1-2) and the pulses controlling its operation are not supplied to the information input of the key 8, while between any phases A, B, C they have a linear voltage U (t) _input current value which is equal to 380 V.

Where:

*) U (t) _in - input line voltage between any phases A, B, C

- амплитуда входного линейного напряжения;*)

- the amplitude of the input line voltage;

*) Ω = 2πF is the angular frequency;

*) F = 50 Hz - industrial voltage frequency U (t) _input

At the bridge output (points 1-2) they have a rectified voltage, which after expansion in the Fourier series has the form [l.1 p. 69]

Where:

- постоянная составляющая выпрямленного напряжения.

- the constant component of the rectified voltage.

- напряжение шестой гармоники частоты 50 Гц,

- voltage of the sixth harmonic of a frequency of 50 Hz,

- напряжение двенадцатой гармоники частоты 50 Гц,

- voltage of the twelfth harmonic of a frequency of 50 Hz,

Where:

Um (300 Hz) = 30 V, Um (600 Hz) = 7 V

respectively, the voltage amplitudes U (t) _{300 Hz} and U (t) _{600 Hz} .

Analysis of the amplitudes of the harmonics of the frequency of 50 Hz shows that for the correct operation of the generator it is necessary to fulfill the inequalities:

To fulfill this condition, it is enough to reduce the amplitude of the voltage of the sixth harmonic of a frequency of 50 Hz using a blocking filter 9.

SECOND STATE OF THE GENERATOR SCHEME

Connect to the output of the bridge 1 a blocking Filter 9, which is formed by resistors 2, 3, 4, respectively having resistance R ₁ , R ₂ , R ₃ , and capacitors 5, 6, 7, respectively, having capacitances C ₁ , C ₂ , C ₃ . Using a blocking filter 9, which is tuned to the cutoff frequency F _cf. = 300 Hz, reduce the magnitude of the amplitude of the sixth harmonic of a frequency of 50 Hz. The blocking filter 9 consists of two parallel connected T-shaped RC filters of high and low frequencies [l.2]. The high-pass filter is formed by capacitors 6, 7 and resistor 4. The low-pass filter is formed by resistors 2, 3 and capacitor 5.

With the right choice of parameters of the elements of the blocking filter, they achieve the fact that at a given cutoff frequency, in our case, F _cf. = 300 Hz, currents of a frequency of 300 Hz at the outputs of both T-shaped filters will be equal in magnitude and opposite in sign, as a result of which the current at a frequency F _cf. = 300 Hz, through the closed key 8, it will be zero, because attenuation at this frequency will be infinitely large.

Thus, after the installation of the barrier filter 9, condition (3) is fulfilled.

THIRD STATE OF THE GENERATOR DIAGRAM

Consider the operation of the generator when the pulses controlling its operation come to the information input of key 8, and the condition is satisfied:

where: U _exercise. - the necessary amplitude of the control video pulses, sufficient to close the key.

Next, the process of turning on, turning off the key is repeated.

When the key is switched with a frequency f ₀ , a current is introduced into the 380 V line, which, taking into account (4) and (5), is a sequence of video pulses with an amplitude U _p = 512 V.

Given (4) and (5), the sequence of video pulses of the current that flows through the resistors 2 and 3 of the blocking filter 9, when switching the key with a frequency f ₀ , has the form:

Next, the process is repeated.

Where: R = R ₁ + R ₂ - the value of the load resistance of the generator.

R ₁ and R ₂ are the resistances of resistors 2 and 3.

- период последовательности видеоимпульсов тока i(t).

is the period of the sequence of video pulses of current i (t).

We expand (6) in a Fourier series [l.3]

In this expansion, we are only interested in the SIGNAL CURRENT i _o (t) with frequency ω _о , i.e. first harmonic of expansion i (t)

- амплитуда токовых сигналов.Where:

- the amplitude of the current signals.

ω _o = 2πf ₀ is the angular frequency.

SELECTION OF THE RANGE OF OPERATING FREQUENCIES f ₀

It is known that the main obstacles in the transmission of signals over power lines in the tonal frequency range are the odd harmonics of the frequency F = 50 Hz of the supply voltage, which decrease with increasing number of harmonics. At a frequency above 13 kHz, the harmonic voltage is comparable with fluctuation noise, which is much smaller in magnitude than the harmonics of the frequency F = 50 Hz [l.1 p. 44].

PROTOTYPE cannot operate at frequencies above 3000 Hz without the installation of chokes due to the occurrence of wave processes due to the long line lengths of 10-35 kV.

[л.1 стр.26], при этом должно выполняться условие:It is known that 380 V lines have an average length of l = 3 km at a wave propagation speed in overhead lines

[l.1 p. 26], while the condition must be met:

*) Define, taking into account (9), the upper boundary of the frequency range of the operating frequencies f ₀

Where:

среднестатистическое значение скорости распространения волны по линиям 380 В,

the average value of the wave propagation velocity along the lines of 380 V,

- длина волны,

- wavelength

*) l = 3 km - the average line length of 380 V,

*) f ₀ - operating frequency in the communication channel.

Thus, we accept for work in low voltage lines 380 V the frequency range:

*) From (10) and (11) we determine the band of working frequencies ΔF (f ₀ ):

*) Let us determine the minimum duration of the radio pulse τ _u in this band, taking into account (12):

Note:

When choosing the duration of the radio pulse from (13), 90% of the pulse energy is received, which falls into the passband of the receiver.

We determine the maximum transmission rate of current signals in the lines of 380 V, taking into account (13)

*) Let’s determine how many times the current signal transmission rate is increased in the STATED TECHNICAL PROPOSAL, taking into account the fact that in the prototype the maximum current signal transmission rate is 50 Bit / s

IMPLEMENTATION OF THE PENDED TECHNICAL PROPOSAL

исходя из Т.У.*) Set the amplitude of current signals

based on T.U.

*) The resistance value R is determined taking into account (8)

Due to the fact that R ₁ and R ₂ are the resistances of resistors 2 and 3, which are in the shoulders of the T-shaped bridge of the low-pass filter, we accept

SELECTION OF FILTER FILTER ELEMENTS

*) For the low-pass filter we have [l.2]:

*) For the High Pass Filter, we have [L.2]:

*) We equate (19) and (20)

where: Ω _cf. = 2πF _cf. - angular cutoff frequency.

*) We determine from (21) the value of the capacitance C _{1 of the} capacitor 5

where: F _cf. = 300 Hz

R - get in (16)

*) The resistance of resistor 4 is:

*) Capacitors of capacitors 6 and 7 are equal to:

Thus, we have proved the fulfillment of the purpose of the invention, namely, the signal transmission speed is increased by 100 times compared with the prototype.

LITERATURE

1. Gutin K.I. Improving the efficiency of information transfer in rural electric networks with a voltage of 10 kV. Thesis for the degree of Ph.D. VIESH, Moscow, 1987

2. Atabekov G.I. Theoretical Foundations of Electrical Engineering, Moscow, "Energy", 1966, pp. 171-172.

3. Bronstein I.N., Senedyaev K.A. Handbook of higher mathematics for engineers and students of technical colleges, Moscow, Gostekhizdat, 1961, pp. 544-555.

Claims (1)

A generator for inputting current signals to a three-phase low voltage line 380 V, frequency 50 Hz, containing phases A, B, C, a three-phase rectifier bridge assembled on diodes D ₁ , D ₂ , D ₃ , D ₄ , D ₅ , D ₆ , at the cathodes of the diodes D ₁ , D ₂ , D _{3 are} combined and connected to the first output of the first resistor, the anodes of the diodes D ₄ , D ₅ , D _{6 are} combined and connected to the fixed terminal of the control key contact, the cathode of the diode D ₄ and the anode of the diode D _{1 are} connected to phase A, the cathode of the diode D ₅ and the anode of the diode D ₂ are connected to the phase B, the cathode of diode D ₆ and the anode of diode _D3 are connected to the C phase, wherein the fact that the first, second, third capacitors are introduced, the second, third resistors, the second terminal of the first resistor is connected to the first plate of the first capacitor and to the first terminal of the second resistor, the second terminal of which is connected to the first plate of the third capacitor and the movable contact of the controlled key, fixed contact which is connected to the first terminal of the third resistor and the second lining of the first capacitor, the second terminal of the third resistor is connected to the second lining of the third capacitor and the first lining of the second ndensatora, the second plate of which is connected to the first terminal of the first resistor.