RU2212758C2 - Passive-active method for current input in three- phase power mains - Google Patents

Abstract

FIELD: electrical engineering; signal transmission over three-phase power mains. SUBSTANCE: proposed method enables signal transmission over three-phase power grid without its treatment by high-frequency traps. Generator circuit using passive-active method for current input into three-phase power mains has transformer, power mains, inductance coil, bridge diodes, switch, and resistors. EFFECT: reduced power requirement of generator. 1 cl, 3 dwg

Description

 The invention relates to the field of electrical engineering and can find application in organizing communication channels using three-phase electrical networks (0.4-35 kV) (network) without processing them with high-frequency chokes. Achievable technical result is a reduction in power consumption in a generator that implements the claimed method.

 It is known "Device for transmitting signals over a three-phase power line", which implements the known method (Patent SU 1107750 A, H 04 B 3/54, 1982). A disadvantage of the known device is the absence in the circuit of the signal key (key) of limiting resistance, which should limit the current through the key when it is closed, if for some reason it was not turned off at a given point in time, while the device burns out before it fails circuit breakers.

 There is also known a passive-active method of generating a signal current, adopted as a prototype, which is implemented in a passive-active type generator (Tsagareishvili S. A., Gutin K.I. K.V. Science and technology in industry, Moscow, 2 (5), 2001, p.55, 56).

 The known generator has a limiting resistor, but there is a drawback - high power consumption from the network.

 Implementation of the proposed method significantly reduces power consumption from the network.

A passive-active method of inputting signal currents into a three-phase electric network 2 (Fig. 1), according to which a signal current i _o (t), which is a beating of oscillations, flows at a time interval t, where 0≤t≤T _о . The waveform of the signal current i _o (t) is shown in Fig.2.

где 2I_m - амплитудное значение биений тока сигнала i₀(t); ω₁ = 2πf₁; ω₂ = 2πf₂; f₁ = f₀-F; f₂ = f₀+F; f₀ - частота сигнала, T₀ = 1/f₀ - период f₀; F = 50 Гц - частота напряжения в сети. Ток i₀(t) протекает по цепи: низковольтная обмотка трансформатора 10/0,4 кВ (трансформатор) фазы А - катушка индуктивности (катушка), при этом на пассивном участке времени t, где 0≤t≤T_o/4, накапливают электромагнитную энергию в катушке W_L
W_L = I²(f₀)•L,
где L - величина индуктивности катушки;
I(f₀) - действующее значение тока сигнала i₀(t).

where 2I _m is the amplitude value of the beats of the signal current i ₀ (t); ω ₁ = 2πf ₁ ; ω ₂ = 2πf ₂ ; f ₁ = f ₀ -F; f ₂ = f ₀ + F; f ₀ - signal frequency, T ₀ = 1 / f ₀ - period f ₀ ; F = 50 Hz - voltage frequency in the network. Current i ₀ (t) flows through the circuit: the low-voltage winding of the transformer 10 / 0.4 kV (transformer) of phase A is an inductor (coil), while accumulating in the passive time section t, where 0≤t≤T _o / 4, electromagnetic energy in the coil W _L
W _L = I ² (f ₀ ) • L,
where L is the magnitude of the inductance of the coil;
I (f ₀ ) is the effective value of the signal current i ₀ (t).

где L - величина индуктивности катушки;
С - величина емкости конденсатора;
L_тр - величина индуктивностей обмоток фаз А, В, С трансформатора.In the active section of time t, where T _o / 4≤t≤T _o create free oscillations of the current i ₀ (t) in the oscillatory circuit: low-voltage winding of the phase A transformer - coil - capacitor - low-voltage winding of the phase C transformer, and the oscillating circuit is set to resonance on the frequency of the signal f ₀

where L is the magnitude of the inductance of the coil;
C is the value of the capacitance of the capacitor;
L _Tr - the magnitude of the inductances of the windings of the phases A, B, C of the transformer.

и обратной

последовательностей:
два тока

- на частоте f₁,
два тока

- на частоте f₂,
причем действующие значения токов симметричных составляющих равны

где I(f₁) и I(f₂) - действующие значения токов симметричных составляющих;
I(f₀) - действующее значение тока сигнала.In the calculations, 2L _{tr are} neglected, because 2L _tr << L. Receive in the network four currents of symmetrical components [1] direct

and reverse

sequences:
two currents

- at a frequency f ₁ ,
two currents

- at a frequency f ₂ ,
moreover, the current values of the currents of symmetrical components are equal

where I (f ₁ ) and I (f ₂ ) are the current values of the currents of symmetrical components;
I (f ₀ ) is the effective value of the signal current.

в электрическую сеть среднего напряжения 10 кВ. Индексы при токах

обозначают соответственно: 1 - прямую АВС, 2 - обратную АСВ последовательности чередования фаз. Векторные диаграммы токов

приведены на фиг.3.Transform currents

into an electric network of medium voltage 10 kV. Current Indices

designate accordingly: 1 - direct ABC, 2 - reverse ACB phase sequence. Vector current diagrams

are shown in figure 3.

The generator circuit with a passive-active method of inputting signal currents into a three-phase electric network (generator) is shown in figure 1, where:
1 - transformer
2 - network
3 - inductor (coil),
4 - capacitor
5 - 5 ₁ , 5 ₂ , 5 ₃ , 5 ₄ - respectively, the first, second, third, fourth diodes of the bridge 5,
6 - the first resistor,
7 - key
8, 9, 10, 11 - resistors - respectively, the second, third, fourth, fifth.

 The GENERATOR works as follows.

1. Consider the operation of the generator, made according to the scheme as in the adopted prototype. The capacitor of the prototype 4 ₁ (Fig. 1) (shown by a dotted line) is included between phases AB. We assume that the potential of phase A is higher than the potential of phase B. When t = 0, the capacitor 4 ₁ is charged, as shown in Fig. 1. In the interim 0≤t≤T _0/4 switch is closed. Two currents flow through the key: 1) the charge current t ₃ (t) is the electromagnetic energy of the coil; 2) the discharge current i _p (t) of the capacitor 4 ₁ to the resistor 6. (The resistance values of the diodes and the key are neglected due to their smallness compared to the resistance value of the resistor 6). The discharge current i _p (t) flows along the circuit: “plus” of the capacitor 4 ₁ - diode 5 ₁ - resistor 6 - key - diode 5 ₃ - “minus” of the capacitor 4 ₁ . The effective value of the voltage applied to the capacitor 4 ₁ is U = 380 B. The energy stored by the capacitor 4 ₁ for one period T ₀ is
W _C = U ² C, (5)
where W _C is the energy of the electric field accumulated by the capacitor 4 ₁ for one period T ₀ ;
U = 380 V - the effective value of the line voltage in the network;
C is the value of the capacitor 4 ₁ .

где

- амплитудное значение;
t - время разряда конденсатора, τ = R•C;
e - основание натурального логарифма;
R - величина сопротивления резистора 6.When the current i _p (t) of the discharge of the capacitor 4 ₁ flows, the voltage across it U _s (t) decreases exponentially

Where

- amplitude value;
t is the discharge time of the capacitor, τ = R • C;
e is the base of the natural logarithm;
R is the resistance value of the resistor 6.

The energy dissipated in the resistance R during the entire transient process is equal to the energy stored in the electric field before switching, i.e. in the time interval t, where T ₀ / 4≤t≤T ₀ .

Transition considered complete after a period of time
t ≅ (3 ÷ 4) τ.
To calculate the power losses in the prototype, specific initial data is taken, for example, taken from the calculation of a generator whose circuit is similar to the prototype's scheme (Gutin K.I., Tsagareishvili S.A. Harmonic oscillation generator for transmitting information in rural electric networks. Technical Bulletin on Electrification of Agriculture, Issue 1 (53). VIESH, M., 1985, pp. 6-16),
where f ₀ = 833 Hz is the signal current frequency i ₀ (t);
Q _to = 20 - quality factor of the coil;
Q _kk = 20 - quality factor of the oscillatory circuit;
R = 8 Ohm - the resistance value of the resistor 6;
C = 8 • 10 ^-6 F - the value of the capacitor 4 ₁ ;
L = 4.57 • 10 ^-3 H - the magnitude of the inductance of the coil.

Определим промежуток времени t_разр(τ) разряда конденсатора 4₁ за промежуток времени 4τ:
4τ = 4RC = 4•8•8•10^-6 = 2,56•10^-4 с (8)
Сравнивая выражения (7) и (8), можно утверждать, что конденсатор 4₁ полностью разрядится на резистор 6.Define the time t _bit (C) adopted for the discharge of the capacitor 4 ₁

We define the time interval t _bit (τ) of the discharge of the capacitor 4 ₁ for the time interval 4τ:
4τ = 4RC = 4 • 8 • 8 • 10 ^-6 = 2.56 • 10 ^-4 s (8)
Comparing expressions (7) and (8), it can be argued that the capacitor 4 _{1 is} completely discharged to the resistor 6.

Следует учесть, что основная нагрузка по передаче сигналов приходится на генератор, установленный на диспетчерском пункте (ДП), который ведет циклический опрос состояния электрооборудования установленного на 1, 2, 3... контролируемых пунктах (КП). Принимают условие, что длительность передачи информации с КП в два раза больше, чем длительность запроса с ДП, тогда с учетом (10) мощность потерь в генераторе ДП - P_п(ДП) будет равна

2. Рассмотрим работу генератора, реализующего заявленный способ, т.е. когда конденсатор 4 включен между фазами А и С, при условии, что потенциал фазы А выше потенциала фазы В, т.е. открыты диоды моста 5₁ и 5₃. Выше было отмечено, что при работе генератора, кроме тока разряда i_p(t), протекает ток i₃(t) заряда электромагнитной энергией катушки, который протекает в промежутке времени t, где 0≤t≤T₀/4.Determine the power loss P _p due to the discharge of the capacitor 4 ₁ to the resistor 6 during continuous operation of the generator
P _p = U ² C • f ₀ = 380 ² • 8 • 10 ^-6 • 833 = 960 W (9)
Considering that the generator only works when transmitting the characters "1", while transmitting the characters "0" it does not work and that the number of signals "1" and "0" is the same in the message, the power of transmission of the characters "1" is P _p ( 1 ") is equal to

It should be noted that the main load for signal transmission falls on the generator installed at the control room (DP), which conducts a cyclic survey of the state of electrical equipment installed at 1, 2, 3 ... controlled points (KP). Accept the condition that the duration of the transmission of information from the CP is twice as long as the duration of the request from the DP, then taking into account (10) the power of losses in the DP generator - P _p (DP) will be equal to

2. Consider the operation of a generator that implements the claimed method, ie when the capacitor 4 is connected between phases A and C, provided that the potential of phase A is higher than the potential of phase B, i.e. open diodes of the bridge 5 ₁ and 5 ₃ . Above it was noted that when the generator, except the discharge current i _p (t), current flows i ₃ (t) of charge energy of the electromagnetic coil, which flows in time interval t, where 0≤t≤T _0/4.

- амплитудное значение; L = 4,57•10^-3 Гн; f_o = 833 Гц. Следует отметить, что этот ток будет равен амплитудному значению тока биений i₀(t) (фиг.2), согласно выражению (1), т.е. 2I_m

где t - время заряда катушки;
e - основание натурального логарифма.The charge current of coil i ₃ (t) flows along the circuit: low-voltage winding of phase A transformer - coil 3 - diode 5 ₁ - resistor 6 - key - diode 5 ₃ - low-voltage winding of phase transformer B. Let us determine the maximum value of this current at t = T ₀ /4; U = 380 V, R = 8 Ohm,

- amplitude value; L = 4.57 • 10 ^-3 H; f _o = 833 Hz. It should be noted that this current will be equal to the amplitude value of the beat current i ₀ (t) (Fig. 2), according to expression (1), i.e. 2I _m

where t is the charge time of the coil;
e is the base of the natural logarithm.

Выражение (13) получено при условии, что ток сигнала i₀(t) в промежутке времени t, где 0≤t≤T₀/4 нарастает не по экспоненте (12), а по синусоиде, т. к. это допущение хорошо согласуется с экспериментом.Determine the effective value of the current I (f ₀ ) of the signal during continuous operation of the generator

Equation (13) obtained under the condition that the current signal i ₀ (t) in time interval t, where ₀ 0≤t≤T / 4 will not increase exponentially (12) and sinusoid, t. K. This assumption is consistent with experiment.

В момент времени t=T₀/4 ключ размыкают и за счет накопленной энергии в катушке (индуктивностью обмоток трансформатора пренебрегают в связи с их малостью по сравнению с индуктивностью катушки) в колебательном контуре возникнут свободные колебания i_{0 свобод}(t)

где L - индуктивность катушки;
R_к = R_кк - сопротивление резонансного контура;
С - емкость конденсатора 4;
U_m - амплитудное напряжение заряда конденсатора в момент времени размыкания ключа t=T₀/4;

L - индуктивность катушки;
e - основание натурального логарифма.We define I (f ₁ ), I (f ₂ ) - the current values of the currents of the symmetrical components - from (4) taking into account (13):

At time t = T _0/4 switch is opened and due to the stored energy in the coil (inductance transformer windings are neglected due to their smallness in comparison with the inductance of the coil) in the resonant circuit oscillations arise free _freedoms i ₀ (t)

where L is the inductance of the coil;
R _to = R _kk is the resistance of the resonant circuit;
C is the capacitance of the capacitor 4;
U _m - the amplitude voltage of the charge of the capacitor at the time of opening the key t = T _0/4 ;

L is the inductance of the coil;
e is the base of the natural logarithm.

At the same time, it is believed that the oscillatory circuit is tuned to the frequency f ₀ , i.e. the frequency of free oscillations, the frequency of the signal f _freedoms equal to the frequency of the signal f ₀ .

В рассматриваемом случае

т.е. R_к<<48 Ом.Free vibrations will occur when the condition:

In the case under consideration

those. R _to << 48 Ohms.

 At time t = 0, the key is closed and the generator operation process considered above is repeated.

 Consider the question of the discharge of the capacitor 4 to the resistance R 6.

We believe that in the time interval t, where 0≤t≤T _o / 4, as in claim 1, the potential of phase A is higher than the potential of phase B, i.e. open diodes 5 ₁ and 5 ₃ and the capacitor 4 has charges, as shown in figure 1 (indicated by a dotted line).

 In this case, there are two paths for the capacitor discharge current 4 i (C).

Way 1: "plus" of the capacitor - diode 5 ₁ - resistor 6 - key - diode 5 ₃ - low-voltage winding of the phase transformer B - low-voltage winding of the phase transformer C - "minus" the capacitor.

The active resistance of this circuit R _{(path 1)} is equal to
R _(path1) = R = 8 ohms. (16)
Way 2: "plus" of the capacitor - coil - low-voltage winding of the phase A transformer - low-voltage winding of the phase C transformer - "minus" of the capacitor 4.

The active resistance of this circuit R _{(path 2)} is equal to R _K , i.e.

При этом активными сопротивлениями индуктивностей обмоток трансформатора пренебрегают.

In this case, the active resistances of the inductances of the transformer windings are neglected.

 Resistors 8, 9, 10, 11 are installed to eliminate overvoltages in the transformer and coil windings when switching the key, this was another drawback in the analog and prototype.

Определим мощность потерь R_потерь(ДП)₃ в заявленном генераторе с учетом (11) и (18)

Полученный результат (19) позволяет сделать вывод, что цель, поставленная изобретением, достигнута.Comparing expressions (16) and (17), it can be argued that in the generator the power consumption spent on the discharge of the capacitance through the resistance R 6 is reduced by a factor of K:

Define the power loss R _loss (DP) ₃ in the inventive generator taking into account (11) and (18)

The obtained result (19) allows us to conclude that the goal set by the invention has been achieved.

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 CTN. VIESH. - M., 1987, p. 65, expressions (3.49) and (3.50).

Claims (1)

A passive-active method of introducing currents into a three-phase electric network, according to which a current i ₀ (t) flows in a section of time t, where 0≤t≤T ₀ , which is a beat of oscillations

along the chain: low-voltage winding of the transformer phase A - inductor, wherein the passive portion of the time t, where ₀ 0≤t≤T / 4, the electromagnetic energy accumulated in inductor W _L = I ² (f ₀₎ • L,
characterized in that in the active region of time t, where T ₀ / 4≤t≤T ₀ create free oscillations of the current i ₀ (t) in the oscillatory circuit: low-voltage winding of the phase A transformer - inductor - capacitor - low-voltage winding of the phase C transformer, wherein the oscillatory circuit is tuned into resonance at the signal frequency f ₀ , where

receive four currents of symmetrical components in a low voltage electrical network, two at a frequency

two in frequency

moreover, the current values of the currents of symmetrical components are equal

transform currents

into the medium voltage electrical network,
where 2Im is the amplitude value of the current beat i ₀ (t);
I (f ₀ ) is the effective current value i ₀ (t);
I (f ₁ ) and I (f ₂ ) - the action of the value of the currents of symmetrical components at frequencies f ₁ and f ₂ ; ω ₁ = 2πf ₁ ; ω ₂ = 2πf ₂ ;
F = 50 Hz - voltage frequency in a three-phase electric network;
f ₀ - current frequency i ₀ (t);
W _L - the value of the accumulated electromagnetic energy in the coil for one period T ₀ = 1 / f ₀ ;
L + 2L _Tr - the value of the inductance in the oscillatory circuit;
L _Tr - the magnitude of the inductance of the low-voltage windings of the phases A, B, C of the transformer, in the calculations are neglected due to their smallness;
L is the inductance value of the inductor;
C is the value of the capacitance of the capacitor;
current indices

denote, respectively, 1-direct ABC, 2-reverse ACB phase sequence.

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