RU2111610C1 - Device for transmitting data signals over overhead three-phase power transmission line - Google Patents

Abstract

FIELD: electrical engineering; telemechanics systems where power transmission line is used as communication channel without using high-frequency traps. SUBSTANCE: power transmission lines rated 0.38, 10, 35 kV are used for the purpose. Device has four air-core inductance coils 1-3, 14, eight resistors 11,19,21,23-25, 33,56, six capacitors 10, 15-18,34, eleven diodes 4-9, 26,28,32,35, four thyristors 12, 29-31, data source 13, DC voltage supply 20, and switch 22. EFFECT: improved reliability under overcurrent conditions and provision for automatic recovery of device serviceability. 1 dwg

Description

 The invention relates to the field of electrical engineering and can find application in organizing communication channels using power lines (0.38-10-35) kV.

 Of the known devices, the closest in technical essence to the invention is a device for transmitting signals through wires of a three-phase power line, which is taken as a prototype. Despite the improvement of the spectral composition of the generated current, which increases the efficiency, the known device has low reliability due to its failure during overcurrents.

 The invention solves the problem of increasing the reliability of the device during overcurrents, with the achievement of the technical result - the ability to restore the device in case of overcurrents.

 The drawing shows a functional diagram of the proposed device.

 The device for transmitting information signals through wires of a three-phase power line contains the first 1, second 2, third 3 inductors, first 4, second 5, third 6, fourth 7, fifth 8, sixth 9 diodes, fourth capacitor 10, first resistor 11, first thyristor 12, information source 13, fourth inductor 14, first 15, second 16, third 17, fifth 18 capacitors, sixth resistor 19, constant voltage power supply 20, second resistor 21, key 22, third 23, fourth 24, fifth 25 resistors eighth 26, ninth 27, tenth 28 diodes , second 29, third 30, fourth 31 thyristors, seventh diode, 32, seventh resistor 33, sixth capacitor 34, eleventh diode 35, eighth resistor 36.

 A device for transmitting information signals through wires of a three-phase power line operates as follows.

 Normal mode

 In the absence of control pulses at the output of the information source 13, the fourth capacitor 10 is charged to the value of the rectified voltage (charge polarity) of the fourth capacitor 10 is shown in the drawing).

где
C_Σ - емкость последовательно соединенных конденсаторов 15, 17 и 18; L₁₄ - индуктивность катушки индуктивности 14.In the presence of control pulses at the output of the information source 13, which follow with the signal frequency f _o (the time interval is considered, the phase A potential is higher than the phase C potential), three currents i ₁ , i ₂ , i ₃ will flow through the first thyristor 12 where i ₁ is the discharge current of the capacitor 10 to the resistor 19, i ₂ is the charge current of the capacitor 18, which flows along the circuit: the plus of the capacitor 15 is the diode 4 - thyristor 29 is the capacitor 18 is the inductor 14 is the thyristor 12 is diode 9 - "minus" of the capacitor 17 - "plus" of the capacitor 17 - "minus" of the capacitor 15 (circuit 1). The resonant frequency of circuit 1 is determined from the expression

Where
C _Σ is the capacitance of series-connected capacitors 15, 17 and 18; L ₁₄ - inductance of the inductor 14.

С₁₀R₁₉ << T₀,
где
f₀ - частота тока сигнала; T₀=1/f₀; f₁ - резонансная частота контура 1; C₁₀ - емкость конденсатора 10; R₁₁ - сопротивление резистора 11; R₁₉ - сопротивление резистора 19.Moreover, it is necessary to fulfill the conditions
f ₁ >> f ₀ ;

C ₁₀ R ₁₉ << T ₀ ,
Where
f ₀ - signal current frequency; T ₀ = 1 / f ₀ ; f ₁ is the resonant frequency of circuit 1; C ₁₀ is the capacitance of the capacitor 10; R ₁₁ is the resistance of the resistor 11; R ₁₉ is the resistance of the resistor 19.

где
R_Σ - активное сопротивление контура 2; L_Σ - индуктивность контура 2; τ - время открытого состояния тиристора.Current i ₃ flowing along the circuit: phase A - inductor 1 - diode 4 - thyristor 29 - resistor 11 - inductor 14 - thyristor 12 - diode 9 - inductor 3 - phase C (circuit 2), at the moment of closing of the thyristor 12 determined from the expression

Where
R _Σ is the active resistance of circuit 2; L _Σ is the inductance of circuit 2; τ is the open time of the thyristor.

The thyristor 12 closes at the end of the charge of the capacitor 18 with the current i ₂ (the charge polarity of the capacitor 18 is shown in the drawing).

где
L_1,3 - индуктивность катушек индуктивности 1 и 3; C_15,17 - емкость конденсаторов 15 и 17 (индуктивностью обмоток питающего трансформатора пренебрегаем).After the thyristor 12 is closed, the charging of the capacitors 15 and 17 with the current i ₀ along the circuit (circuit 3) begins: phase A - capacitor 15 - capacitor 17 - phase C. The circuit elements are selected from the condition

Where
L _1,3 - inductance of inductors 1 and 3; C _15.17 - capacitance of capacitors 15 and 17 (neglect the inductance of the windings of the supply transformer).

The current i _{0 of the} recharging of the capacitors 15 and 17 is the signal current, which is introduced into the three-phase electric network.

где
ω₁= 2π(f₀-F); ω₂= 2π(f₀+F); , F = 50 Гц - частота напряжения трехфазной линии электропередачи.The analytical expression of the current i ₀ has the form

Where
ω ₁ = 2π (f ₀ -F); ω ₂ = 2π (f ₀ + F); , F = 50 Hz - voltage frequency of a three-phase power line.

Thus, two currents are introduced into the three-phase power line at frequencies f ₁ = f ₀ -F and f ₂ = f ₀ + F
After closing the thyristor 12, the capacitors 18 are discharged to the resistor 11, and the capacitor 10 is charged by the current flowing through the circuit: phase A - inductor 1 - diode 4 - thyristor 29 - resistor 11 - inductor 14 - capacitor 10 - resistor 19 - diode 9 - inductor 3 - phase C.

 After the discharge of the capacitor 18 to the resistor 11 and the charge of the capacitor 10, the switching part of the circuit becomes stable. Similarly, other oscillatory circuits of the claimed device work.

As follows from the description of the operation of the device in normal mode, the thyristors 29, 30, 31 should open synchronously, respectively, with the diodes 4, 5, 6. This is achieved as follows. The control electrodes of the thyristors 29, 30, 31 are supplied with the voltage for unlocking the thyristors from a constant voltage power supply 20. For the considered time interval, the direct control current required to unlock the thyristor 29 flows through the circuit: "plus" of the constant voltage power supply 20 - resistor 21 - resistor 23 - diode 26 - thyristor control electrode 29 - thyristor cathode 29 - minus the constant voltage power source 20. When the thyristor 12 is opened for a time τ, the capacitor 34 is charged (the polarity of the capacitor 34 is azan in the drawing) along the chain: a first terminal of the resistor 11 - the "plus" capacitor 34 - "minus" capacitor 34 - diode 35 - resistor 36 - the second terminal of the resistor 11. In this condition operate
τ ≪ C ₃₄ R ₃₆ ,
Where
C ₃₄ is the capacitance of the capacitor 34; R ₃₆ is the resistance of the resistor 36.

Thus, the capacitor 34 during the open state of the thyristor 12 is charged to a value of U _norms. . In this case, the condition
U _norms ≈0.25 U _threshold ,
Where
U _norms - voltage across the capacitor 34 during normal operation of the circuit; U _threshold is the threshold voltage of the switch 22 applied by the capacitor 34 to the control input of the key 22 in the circuit: “plus” capacitor 34 - diode 32 - control input of the key 22 - resistor 33 - “minus” of the capacitor 34.

 Emergency mode.

где
I_пер - действующее значение тока перегрузки; E₀ - среднее значение выпрямленного напряжения, прикладываемого между катодом и анодом тиристора 12; R_Σ - суммарное активное сопротивление элементов цепи, по которым протекает ток перегрузки I_пер. Такая ситуация может быть, когда в цепи управления тиристора 1 возникают помехи, величина которых перемешивает порог отпирания этого тиристора. Природа появления помех известна. Это в основном радиопомехи, вызванные грозовыми явлениями, которые распространяются по проводам линий электропередачи и вызывают ток перегрузки I_пер. Этот ток без специальной защиты устройства вызовет перегорание плавких вставок, включенных последовательно в фазы A, B и C. При этом устройство автоматически восстанавливает свою работоспособность следующим образом.If for some reason the thyristor 12 did not close after time τ and remained in a conducting state, then an overload current will go through it

Where
I _per - the effective value of the overload current; E ₀ is the average value of the rectified voltage applied between the cathode and the anode of the thyristor 12; R _Σ is the total active resistance of the circuit elements through which the overload current I _per . This situation may occur when interference occurs in the control circuit of thyristor 1, the value of which mixes the threshold for unlocking this thyristor. The nature of the interference is known. This is mainly radio interference caused by thunderstorms that propagate along the wires of power lines and cause an overload current I _per . This current, without special protection of the device, will cause burnout of the fusible inserts connected in series in phases A, B and C. In this case, the device automatically restores its operability as follows.

When thyristor 12 is opened for a time longer than τ, the entire rectified voltage E ₀ will be applied to the first resistor 11 (voltage drops in the inductor 14 and thyristor 12 are neglected). The capacitor 34 starts charging in the limit to the value of E ₀ . This potential is applied to the control input of key 22.

When the charge of the capacitor 34 reaches a value higher than U ₀ (threshold voltage of operation of the key 22), it closes. Moreover, the condition
U _threshold ≈0.75 U ₀ .

When the key 22 is activated, the triggering circuits of the thyristors 29, 30, 31 are shunted, which will cause them to close with the supply voltage and interrupt the overload current I _per through the thyristor 12.

 The capacitor 34 will begin to discharge in a circuit: the plus of the capacitor 34 — the diode 32 — the control input of the key 22 — the resistor 33 — the plus of the capacitor 34.

When the charge of the capacitor 34 is lower than the value U _{0, the} key 22 will open and the circuit will go into working condition.

 The choice of values of the capacitance of the capacitor 34 and the resistance of the resistor 33 get the necessary recovery time of the claimed device.

 Achieving the goal set by the invention is to increase the reliability is achieved by automatically restoring the health of the claimed device from an emergency.

Claims (1)

 A device for transmitting information signals through wires of a three-phase power line, comprising a first, second and third inductor, the first terminals of which are connected to the wires of the three-phase power line, and the second terminals are connected to the first terminals of the first, second and third capacitors, respectively, the second terminals of which are combined, and to the anodes of the first, second and third diodes, which are connected respectively to the cathodes of the fourth, fifth and sixth diodes, the anodes of which are combined and connected to the cathode ne the first thyristor and the first output of the information source, the second output of which is connected to the control terminal of the first thyristor, the anode of which is connected to the first output of the fourth capacitor, as well as the first resistor, characterized in that the second, third, fourth, fifth, sixth, seventh and eighth are introduced resistors, DC power supply, key, seventh, eighth, ninth, tenth and eleventh diodes, as well as fifth and sixth capacitors, second, third and fourth thyristors and fourth inductance coil, the first output to is connected to the anode of the first thyristor, and the second terminal is connected to the first terminals of the first resistor and fifth capacitor, the second terminals of which are connected to the first terminal of the sixth capacitor, the cathodes of the second, third and fourth thyristors, the negative terminal of the DC power supply, the anode of the seventh diode and the input a key whose output is connected to the first terminals of the second, third, fourth and fifth resistors, the second terminal of the second resistor is connected to the positive terminal of the power supply, constant voltage ii, the second terminals of the third, fourth and fifth resistors are connected respectively to the anodes of the eighth, ninth and tenth diodes, the cathodes of which are connected respectively to the control terminals of the second, third and fourth thyristors, the anodes of which are connected respectively to the cathodes of the first, second and third diodes, the second terminal the fourth capacitor is connected through the sixth resistor to the cathode of the first thyristor, the second terminal of the sixth capacitor is connected to the anode of the eleventh diode and the first terminal of the seventh resistor, the second the output of which is connected to the control input of the key and the cathode of the seventh diode, the cathode of the eleventh diode is connected through the eighth resistor to the first output of the first resistor.