RU2039412C1 - Device for receiving signals in three-phase supply line - Google Patents

Abstract

FIELD: electric engineering. SUBSTANCE: device has power transformer 1, first and second voltage filters 2 and 3 for symmetrical constituents, first and second low-pass filters 4 and 5, phase detector 6, mixer 7, low-pass filter 8, heterodyne 9, first and second filters 10 and 11 for currents of symmetrical constituents, third and fourth low-pass filters 12 and 13, phase detector 14, transmitter 15, first, second and third communication transformers 16, 17 and 18. EFFECT: decreased power consumption. 1 dwg

Description

 The invention relates to communication technology and may find application in receiving television signals in three-phase electrical networks of 0.38-10-35 kV.

 It is known "Device for transmitting and receiving voltage signals through a three-phase power line" (a.c.SSSR N 1107750), the disadvantage of which is low noise immunity.

раз, по сравнению с вышеупомянутым, известное устройство имеет недостаток, заключающийся в большой потребляемой мощности.It is known "Device for receiving signals in a three-phase power line", adopted as a prototype. Despite the increased noise immunity in

times, compared with the above, the known device has the disadvantage of large power consumption.

 The aim of the invention is to reduce power consumption. This goal is achieved by the fact that in a known device containing a network transformer, the low-voltage windings of which are connected to the inputs of the first and second voltage filters of symmetrical components, the outputs of each of which are connected respectively to the inputs of the first and second narrow-band filters, the outputs of each of which are respectively connected to the first and the second inputs of the first balanced phase detector, the output of which is connected to the first input of the mixer, the output of which is connected to the input of the low-pass filter from, a local oscillator, including the third and fourth narrow-band filters, the outputs of each of which are respectively connected to the first and second inputs of the second balanced phase detector, the output of which is connected to the second input of the mixer, the transmitter, the first, second, third communication transformers, the first the second filters currents of symmetrical components, and the transmitter outputs are respectively connected through the primary windings of the first, second, third communication transformers to the low-voltage windings of the network transf rmator, the first conclusions of the secondary windings of the first, second, third communication transformers are combined, the second conclusions of each of them are respectively connected to the inputs of the first and second filters of the currents of symmetrical components, the outputs of each of which are respectively connected to the inputs of the third and fourth narrow-band filters.

 The drawing shows a functional diagram of the proposed device.

 The device comprises a network transformer 1, the low-voltage windings of which are connected to the inputs of the first 2 and second 3 voltage filters of symmetrical components, the outputs of each of which are connected respectively to the inputs of the first 4 and second 5 narrow-band filters, the outputs of each of which are respectively connected to the first and second inputs of the first balanced phase detector 6, the output of which is connected to the first input of the mixer 7, the output of which is connected to the input of the low-pass filter 8, local oscillator 9, including the third 12 and fourth 13 th narrow-band filters, the outputs of each of which are respectively connected to the first and second inputs of the second balanced phase detector 14, the output of which is connected to the second input of the mixer 7, transmitter 15, first 16, second 17, third 18, communication transformers, first 10, second 11 filters of currents of symmetrical components, and the outputs of the transmitter 15 are respectively connected through the primary windings of the first 16, second 17, third 18 communication transformers and low-voltage windings of the network transformer 1, the first conclusions of the secondary windings the first 16, second 17, third 18 communication transformers are combined, the second terminals of each of them are respectively connected to the inputs of the first 10 and second 11 current filters of the symmetrical components, the outputs of which are respectively connected to the inputs of the third 12 and fourth 13 narrow-band filters.

The device operates as follows: on the low-voltage windings of the network transformer 1, the voltage of the negative sequence signal U ₂ (f ₁ ) at the frequency f ₁ and the voltage of the direct sequence U ₁ (f ₂ ) at the frequency f _{2 are formed} , and f ₁ -f ₂ 2F. The first filter of the symmetric components of the reverse sequence 2 is tuned to the frequency f ₁ , the second filter of the symmetric components of the direct sequence 3 is tuned to the frequency f ₂ . From the outputs of the first and second filters of symmetrical components 2 and 3, the voltages go to the inputs of the first and second narrow-band filters 4 and 5.

The passbands of these filters are selected from the condition Δ F≅F Hz. This is necessary so that no more than one harmonic component of the industrial frequency falls into the filter passband, which is an interference for signal reception. From the outputs of the first and second narrow-band filters 4 and 5, voltage frequencies f ₁ and f ₂ are applied to the inputs of the first balanced phase detector 6.

(3)
Это следует из принципа работы передатчика пассивно-активного типа, который установлен на контролируемом пункте.Let the output voltage of the first narrow-band filter 4 have the signal voltage
U ₁ (t) U _m1 cos˙ (ω ₁ t + φ ₁ ) (1)
From the output of the second narrow-band filter 5 we have a signal voltage
U ₂ (t) U _m2 cos˙ (ω ₂ t + φ ₂ ) (2) where φ ₁ = φ ₂

(3)
This follows from the principle of operation of a passive-active type transmitter, which is installed at a controlled point.

cos

t +

-U

cos

t +

=2U_mcosΩtsinω_ot
U_m действующее значение напряжений биений, которое покажет обычный прибор переменного напряжения, равное половине максимума огибающей биений. Причем выполняется условие
U₁= U₂

, где U₁ и U₂ действующие значения напряжений сигналов согласно (1) и (2).Due to the fact that the power source of such transmitters is a three-phase electric network, the voltage frequency of which is F, a signal voltage of two frequencies f ₁ and f _{2 is} generated in the line, separated by an amount of Ω2π2F Hz, i.e. beats form. Phase voltage equals
U ₄ (t) = U

cos

t +

-U

cos

t +

= 2U _m cosΩtsinω _o t
U _{m is the} effective value of the beating stresses, which will be shown by a conventional device of alternating voltage, equal to half the maximum of the envelope of the beats. Moreover, the condition
U ₁ = U ₂

, where U ₁ and U ₂ are the actual voltage values of the signals according to (1) and (2).

At t 0. The transmitter at the transmission point to the gearbox (not shown) does not work. At the receiving point there are no voltage signals U ₁ (t) and U ₂ (t) described by expressions (1) and (2).

When t> 0. The transmitter at the point of transmission starts to work. At the receiving point, voltages U ₁ (t) and U ₂ (t) appear.

cosφ_c, (4) где U_m1, U_m2 амплитудные значения напряжений сигнала на входах первого балансного фазового детектора 6; K_д коэффициент передачи амплитудного детектора.The signal voltage U ₁ (t) and U ₂ (t) are supplied to the first and second inputs of the first balanced phase detector 6, from the output of which the signal voltage U _c (t) is supplied to the first input of the mixer 7, and
U _c (t)

cosφ _c , (4) where U _m1 , U _{m2 are the} amplitude values of the signal voltages at the inputs of the first balanced phase detector 6; K _{d the} gain of the amplitude detector.

(6) Причем выполняется условие
f₁ f_c F
f₂ f_c + F, (7) где f_c частота коммутации ключа передатчика, установленного в пункте передачи на КП; F частота промышленного напряжения.φ _c = (ω ₁ -ω ₂ ) + φ ₁ -φ ₂ (5) where

(6) Moreover, the condition
f ₁ f _c F
f ₂ f _c + F, (7) where f _c is the switching frequency of the transmitter key installed at the transmission point to the CP; F frequency of industrial voltage.

Taking into account expressions (3) and (6), expression (5) takes the form
φ _c = 2π (f ₁ -f ₂ ) + φ ₁ -φ ₂ = -Ωt (8) where Ω = 2π f _c F; f ₁ -f ₂ -2F i.e. equal to twice the value of the circular frequency of the industrial voltage.

Напряжение сигнала U_c(t) поступает на первый вход смесителя 7.Taking into account (7), expression (4) takes the form:
U _c (t) A _c ˙ cosΩ t, (9) where A _c

The signal voltage U _c (t) is supplied to the first input of the mixer 7.

 The voltage of the local oscillator 9, which is supplied to the second input of the mixer 7, is formed as follows.

When the transmitter 15 is operating, primary currents I ₁ (f ₃ ) at a frequency f ₃ and a direct sequence I ₂ (f ₄ ) at a frequency f ₄ flow through the primary windings of the first 16, second 17, third 18 communication transformers. These currents are transformed through the secondary windings of communication transformers 16, 17, 18 and fed to the inputs of the first 10 and second 11 current filters, symmetrical components of the reverse and forward sequences, respectively. The first current filter of the symmetrical components 10 is tuned to a frequency f ₃ , the second to a frequency f ₄ . From the outputs of the first and second filters, the currents of symmetrical components 10 and 11 supply voltage to the inputs of the third and fourth narrow-band filters 12 and 13. The pass bands of these filters are selected from the condition ΔF≅ F. This is necessary so that no more than one harmonic component of the industrial frequency F, which is an interference signal. From the output of narrow-band filters 12 and 13, voltage frequencies f ₃ and f ₄ are supplied to the first and second inputs of the second balanced phase detector 14.

(12)
Напряжения U₁(г) и U₂(г) поступают на первый и второй входы второго балансного фазового детектора 14, с выхода которого напряжение гетеродина 9 U_г(t) поступает на второй вход смесителя 7, причем
U_г(t)

cosφ_г, (13) где U_m1(г); U_m2(г) амплитудные значения напряжений на входах второго балансного фазового детектора 14.Let the output of the third narrow-band filter 12 have a voltage
U ₁ (g) (t) U _m1 (g) cos [ω ₁ (g) t + φ ₁ (g)] (10)
From the output of the fourth narrow-band filter 13 we have a voltage
U ₂ (g) (t) U _m2 (g) cos [ω ₂ (g) t + φ ₂ (g)] (11)
By analogs with (3), we have
φ ₁ (g) = φ ₂ (g)

(12)
Voltages U ₁ (g) and U ₂ (g) are supplied to the first and second inputs of the second balanced phase detector 14, from the output of which the local oscillator voltage 9 U _g (t) is supplied to the second input of the mixer 7, and
U _g (t)

cosφ _g , (13) where U _m1 (g); U _m2 (g) the amplitude values of the voltages at the inputs of the second balanced phase detector 14.

(15)
При этом выполняется условие
f₃ f_г-F; f₄ f_г+F где f_г частота коммутации ключа передатчика 15.φ _g = (ω ₃ -ω ₄ ) t + φ ₁ (g) -φ ₂ (g) (14) where

(fifteen)
In this case, the condition
f ₃ f _g -F; f ₄ f _g + F where f _{g the} switching frequency of the transmitter key 15.

Напряжение гетеродина согласно (13) поступает на второй вход смесителя 7.Taking into account expressions (12) and (15), expression (14) takes the form
φ _g = 2π (f ₃ -f ₄ ) t + φ ₁ (g) -φ ₂ (g) = - Ωt (16) where Ω = 2π˙ 2F f ₃ -f ₄ -2F
In view of (16), expression (13) takes the form:
U _g (t) A _g ˙cosΩ t (17) where A _g

The local oscillator voltage according to (13) is supplied to the second input of the mixer 7.

From the analysis of expressions (9) and (17), an important conclusion follows that the voltage at the output of the balanced phase detector does not have frequency components f ₁ , f ₂ , f ₃ and f ₄ , therefore, two voltages are supplied to the first and second inputs of mixer 7 with equal frequencies and phases.

cos2Ωt +

(18) где m < 1 постоянный коэффициент, зависящий от амплитуды гетеродина; S_o крутизна характеристики нелинейного элемента умножителя 7.The voltage at the output of the mixer U _cm (t) (multiplier) will be equal to
U _cm (t) = A _c S _o cosΩt +

cos2Ωt +

(18) where m <1 is a constant coefficient depending on the amplitude of the local oscillator; S _{o the} steepness of the characteristics of the nonlinear element of the multiplier 7.

(19)
Для выделения постоянного напряжения U_o напряжение с выхода смесителя 7 поступает на фильтр нижних частот 8, который отфильтровывает напряжения с частотами Ω и 2 ΩAn analysis of expression (18) shows that the first and second terms are voltages having frequencies Ω and 2Ω; The last term is a constant voltage
U _o

(19)
To select a constant voltage U _{o, the} voltage from the output of the mixer 7 is supplied to a low-pass filter 8, which filters out voltages with frequencies Ω and 2 Ω

Claims (1)

 A device for receiving signals in a three-phase power transmission line, comprising a network transformer, the low-voltage windings of which are connected to the inputs of the first and second voltage filters of symmetrical components, the outputs of each of which are connected respectively to the inputs of the first and second narrow-band filters, the outputs of which are respectively connected to the first and second inputs balanced phase detector, the output of which is connected to the first input of the mixer, the output of which is connected to the input of the low-pass filter, hetero a dyn, containing the third and fourth narrow-band filters, the outputs of each of which are respectively connected to the first and second inputs of the second balanced phase detector, the output of which is connected to the second output of the mixer, and a transmitter, characterized in that, in order to reduce power consumption, they are introduced into the local oscillator the first, second and third communication transformers, the first and second filters of the currents of symmetrical components, and the outputs of the transmitter are respectively connected through the primary windings of the first, second and third trans communication formors to low-voltage windings of a network transformer, the first outputs of the secondary windings of the first, second and third communication transformers are combined, the second outputs of the secondary windings of the first, second and third communication transformers are connected to the inputs of the first and second filters of the currents of symmetrical components, the outputs of which are respectively connected to the inputs of the third and fourth narrowband filters.