CN1239345A - Design method of carrier-filter joint circuit for power transmission line and its joint filter circuit - Google Patents

Abstract

A joint filter circuit for carrier of power transmission line is designed based on line resistor Ri, coupling capacitor Cc, the stray capacitance of Cc's low-voltage end to ground Cx and the equivalent resistor of carrier equipment RL. Said circuit features that the reactive elements constitute a simplest ladder-shaped biterminal network, whose output port is a serially-connected capacitor C directly connected to input of carrier equipment. The impedance converter is directly inserted in the network. The number ratio of low-pass reactive elements to high-pass ones is 0.25-0.5.

Description

The method for designing of carrier-filter joint circuit for power transmission line and filter joint circuit

The invention belongs to the bonding apparatus field between power line carrier and the high voltage transmission line, be specifically related to a kind of method for designing and filter joint circuit of carrier-filter joint circuit for power transmission line.

At present; electric line carrier communication is the important means that carrier communication and relay protection signal transmission are carried out in electric power system; filter joint is the interface equipment that connects power line carrier and link to each other with high voltage transmission line by coupling capacitor; to realize the impedance matching between high voltage transmission line and the power line carrier; the return loss that makes the high voltage transmission line hf channel is enough big and effective attenuation is as far as possible little; and the forceful electric power between realization high voltage transmission line and the power line carrier equipment is isolated assurance power line carrier equipment and operating personnel's safety.In addition, also want to stop 50Hz current interference that may occur in the power line carrier equipment inlet loop and the adverse effect that overcomes coupling capacitor low-voltage terminal stray capacitance.The filter joint of superior performance embodies from following several respects: 1, return loss big (decay of communication signal is just little); 2, the capacity of required coupling capacitor little (can reduce cost); 3, channel wide (to hold more signalling channel); 4, can overcome the adverse effect of coupling capacitor low-voltage terminal stray capacitance; 5, can stop 50Hz disturbance current in the carrier terminal equipment inlet loop.

Filter joint is made up of reactance component and impedance transformer, and the effect of reactance component in circuit is different, is used for stoping the reactance component of high-frequency current circulation to be called the low pass element, is used for stoping the reactance component of low-frequency current circulation to be called high pass components.Promptly in circuit and arm inductance and series arm electric capacity be called high pass components, and arm electric capacity and series arm inductance are called the low pass element.Present filter joint circuit is not generally considered the influence of the stray capacitance over the ground of coupling capacitor low-voltage terminal, do not consider the interference of 50Hz power current in the carrier terminal equipment loop, its filter joint circuit has has only high pass components, and the high and low logical parts number proportioning that has is unreasonable.Making the low pass parts number and the ratio of high pass components number is K; then has only high pass components circuit K=0 (as shown in Figure 7); the irrational circuit of high low pass parts number proportioning (K=0.7 as shown in Figure 8); the circuit design that the K value is not good enough all can not make return loss reach maximization in passband; therefore signal attenuation is bigger in use; frequency band is narrower; the capacity of required coupling capacitor is big; do not consider simultaneously the adverse effect of coupling capacitor low-voltage terminal stray capacitance yet; can not stop the 50Hz disturbance current in the carrier terminal equipment inlet loop; reduced the reliability of relay protection device, made the poor-performing of filter joint, cost is higher.

The purpose of this invention is to provide a kind of by change height switch on anti-element the proportioning and the element order of connection and optimize return loss, widening frequency band that component parameters obtains to increase filter joint, reduce required coupling capacitor capacity and can overcome the adverse effect of stray capacitance and can prevent that the 50Hz low frequency from harassing the method for designing and the filter joint circuit thereof of the carrier-filter joint circuit for power transmission line of current interference.

The method for designing of this carrier-filter joint circuit for power transmission line the steps include:

1) according to given line side resistance R i, coupling capacitor Cc, the coupling capacitor low-voltage terminal equivalent resistance R of stray capacitance Cx and carrier equipment over the ground _LActual parameter, make R _LOn power P ₂The value approximation signal source maximum power Pmax that may confess as far as possible, promptly return loss is big as far as possible, the pass of return loss and power is:

A _P＝0.5Ln〔Pmax/(Pmax－P ₂)〕

2) according to baud decay integration theorem, the pass of deriving between return loss and the frequency is: ${\∫}_0^{\∞}(A_P/f^2)\mathrm{df}={2\mathrm{\π}}^2\[\mathrm{Ri}\×\mathrm{Cc}-\mathrm{\Σ}(1/Z_j)\]$

Then to desirable A shown in Figure 10 _PThe theoretical boundary of the maximum return loss in the characteristic between frequency band f1～f2 is:

A _Pmax＝2π ²f ₁f ₂〔Ri×Cc－∑(1/Z _j)〕/(f ₂－f ₁)

3) according to increasing f ₁～f ₂Return loss A in the frequency range _P, 0～f must draw up as far as possible ₁The low-frequency current of low-frequency range and the f that draws up in right amount ₂The rule of the high-frequency current of～∞ high band is selected the plurality purpose high pass components low-frequency current of drawing up for use, selects the fewer purpose low pass element high-frequency current of drawing up for use;

4) high pass components and low pass element are connected into the simplest trapezoidal reactance two-port network, the series arm capacitor C of network egress links to each other with the arrival end of carrier equipment, the inlet of network links to each other with line side coupling capacitor Cc, and the carrier equipment that the network terminal connect is used equivalent resistance R _LExpression, impedance transformer is inserted in the inside of two-port network;

5), make at f with the ratio K of preferred low pass element of optimization and high pass components with optimize and revise the parameter of circuit element repeatedly ₁～f ₂The component parameters of the filter circuit in the frequency range can compensate the influence of stray capacitance over the ground of coupling capacitance low-voltage terminal, makes return loss A _PMinimum value maximization, make A _PApproach return loss maximum limit A as much as possible _Pmax

6) draw final circuit structure, component value and circuit characteristic.

She Ji filter joint circuit according to the method described above, it is between coupling capacitor and carrier equipment, form by reactance component and an impedance transformer, it is characterized in that forming the simplest trapezoidal reactance two-port network by reactance component, network egress is the series arm capacitor C, and it directly links to each other with the arrival end of carrier equipment, and impedance transformer T is plugged on network internal, wherein the ratio K of the number of low pass reactance component and high pass reactance component is between 0.25～0.5, i.e. 0.25≤K≤0.5.

The present invention has the following advantages:

1. use its performance of circuit of the method for designing design of this filter joint circuit to be better than conventional filter joint, return loss has improved 15%;

2. because when the design filter joint circuit, coupling capacitance and stray capacitance are considered as circuit element, by the reasonable setting of K value and the optimization of circuit parameter, can overcome the adverse effect (stray capacitance that present maximum can overcome reaches 1500pF) of coupling capacitor low-voltage terminal stray capacitance, make product meet GB7329-98 " power line carrier bonding apparatus " national standard and require (at present, IEC481-74 " power carrier bonding apparatus " standard is not considered the influence of stray capacitance);

3. by the reasonable setting of K value, make filter joint can have a series arm capacitor C to exist connecing power line carrier equipment one side, can prevent effectively that 50Hz and so on low frequency from harassing the interference of electric current.

Embodiments of the invention are referring to following each figure

Fig. 1～Fig. 3 is the present invention's 5 reactance component circuit theory diagrams

Fig. 4, Fig. 5 are the present invention's 3 reactance component circuit theory diagrams

Fig. 6 is the product structure circuit diagram of Fig. 2 of the present invention

Fig. 7 has only the circuit theory diagrams of high pass reactance component for existing product

Fig. 8 is the existing product irrational circuit theory diagrams of anti-parts number proportioning of just switching on

Among the figure:

The coupling capacitor low-voltage terminal is stray capacitance over the ground for Cc---coupling capacitor Cx---

L ₁～L ₁₃---inductance C---is every low frequency component electric capacity

C ₁～C ₃---electric capacity T---impedance transformer

J---carrier terminal equipment Q---disconnecting link

F---lightning arrester RL---carrier equipment equiva lent impedance

Ri---line side equiva lent impedance JL---filter joint

The line side impedance is 300,400, and the cable side impedance is 75,100, selects the inductance tap according to the impedance of line side and cable side.

The condition of work of filter joint as shown in Figure 9, Cc is a high-tension coupling condenser among the figure, Ri is the power line wave impedance, R _LBe the inlet impedance of carrier equipment, Cx is the stray capacitance over the ground of coupling capacitor low-voltage terminal.Designing requirement to filter joint is at given Ri, Cc, Cx and R _LSituation under, improve the impedance matching between power line and the carrier equipment as far as possible, promptly should make R _LThe power P that obtains ₂Value big as far as possible.The maximum power that makes power line side dummy source E and Ri provide is Pmax, then return loss A _PWith Pmax and P ₂The pass be: A _P=0.5Ln (Pmax/ (Pmax-P ₂))=Ln|1/ ρ (j ω) | in (how) (1) formula | ρ (j ω) | be reflection coefficient, if frequency variable j ω is exploited to multiple change frequency domain S, claim that then ρ (S) is a reflective function, the form that it can be write as factor is as follows: ρ (S)=K ((S-Z ₁) (S-Z ₂) ... (S-Z _K) ... )/((S-q ₁) (S-q ₂) ... (S-q _K) ...) Z wherein _KBe the zero point of ρ (S), q _kBe the limit of ρ (S), K is a constant.

Can find out P when mating fully by formula (1) ₂=Pmax, A _P→ ∞, ρ=0, P when complete mismatch ₂=0, A _P=0, ρ=1.Therefore, can rephrase under these conditions, make A the designing requirement of filter joint _PValue big as far as possible.

By baud (Bode) decay integration theorem, the A of circuit in the derived graph _PValue will be subjected to following restriction: ${\∫}_0^{\∞}(A_P/f^2)\mathrm{df}={2\mathrm{\π}}^2\[\mathrm{Ri}\×\mathrm{Cc}-\mathrm{\Σ}(1/Z_j)\]------\left(2\right)$ Z in the formula _jIt is the zero point of ρ (s) on the S RHP.Formula (2) shows on the positive frequency axle, A _PArea under a curve has a restriction, and in order to make full use of the restricted area of this piece, the ideal characterisitics of filter joint should be as shown in figure 10, at passband f ₁To f ₂Interval A _PThe value maximum is designated as A _Pmax, the A that band is outer _PValue is zero, can obtain by formula (2):

A _Pmax＝2π ²f ₁?f ₂〔Ri×Cc－∑(1/Z _j)〕/(f ₂－f ₁) (3)

Certainly this specific character is impossible physics realization among the figure, can only approach it as much as possible, and more complicated when the circuit of filter joint, the method for designing of employing is more advanced, and the degree of approaching will be better.The denominator that also notes that integrand in the formula (2) in addition contains weighted factor f ²So, the frequency lower of healing, the weight of its area is bigger, though this just points out us 0～f ₁And f ₂The A at～∞ place _PValue all should be forced down, but more should put forth effort to make the A of zero-frequency and vicinity thereof _PBe worth forr a short time as far as possible, forcing down low-frequency band external signal ratio in other words, to force down the high frequency band external signal more important.By (3) formula as can be seen, A _PmaxValue except that being subjected to Ri, Cc restriction, also and Z _jRelevant, Z _jExistence always make A _PmaxReduce Z _jValue heal more little.When not having Cx, ρ (s) can not contain Z _j, thereby have bigger return loss A _PmaxValue.But as long as coupling capacitor exists, Cx just exists, and when Cx, ρ (s) must contain the root Z of RHP _jThereby, make A _PmaxReduce, Cx more more.

By formula (2) as can be seen, make 0～f ₁The A of low-frequency range _PBe worth little, i.e. P ₂Value little, can adopt high pass components to finish, make f ₂The A of～∞ high band _PBe worth for a short time, can adopt the low pass element.Owing to force down the A of low-frequency range _PValue is than forcing down the more important of high band, so the number of high pass components should be more than the number of low pass element.

Circuit embodiments is as follows:

Embodiment 1:

Present embodiment is illustrated in figure 1 as 5 reactance component circuit theory diagrams, and annexation is from left to right: series arm low pass inductance L ₁, and arm high pass inductance L ₂, series arm high pass capacitor C ₁, and arm high pass inductance L ₃, impedance transformer T, series arm high pass capacitor C.This circuit has four high pass reactance components, a low pass reactance component, and the ratio K=0.25 of low pass reactance component and the number of high pass reactance component reaches the adverse effect that overcomes coupling capacitor low-voltage terminal stray capacitance by the parameter of optimizing element, increases A _PValue.

Embodiment 2:

Present embodiment such as Fig. 2, Figure 6 shows that 5 reactance component circuit theory diagrams, annexation is from left to right: and arm high pass inductance L ₄, series arm low pass inductance L ₅, series arm high pass capacitor C ₂, and arm high pass inductance L ₆, impedance transformer T, series arm high pass capacitor C.Fig. 6 is product structure figure, is applicable to that the line side impedance is that 300 Ω, 400 Ω and cable side impedance are 75 Ω, two kinds of situations of 100 Ω.Other is identical with embodiment 1.

Embodiment 3:

Present embodiment is illustrated in figure 3 as 5 reactance component circuit theory diagrams, and annexation is from left to right: and arm high pass inductance L ₇, series arm high pass capacitor C ₃, and arm high pass inductance L ₈, series arm low pass inductance L ₉, impedance transformer T, series arm capacitor C.Other is identical with embodiment 1.

Embodiment 4:

Present embodiment is illustrated in figure 4 as 3 reactance component circuit theory diagrams, and annexation is from left to right: series arm low pass inductance L ₁₀, and arm high pass inductance L ₁₁, impedance transformer T, series arm capacitor C.This circuit has 2 high pass reactance components, a low pass reactance component, and the ratio K=0.5 of low pass reactance component and the number of high pass reactance component reaches the adverse effect that overcomes coupling capacitor low-voltage terminal stray capacitance by the parameter of optimizing element, increases A _PValue.

Embodiment 5:

Present embodiment is illustrated in figure 5 as 3 reactance component circuit theory diagrams, and annexation is from left to right: and arm high pass inductance L ₁₂, series arm low pass inductance L ₁₃, impedance transformer T, series arm capacitor C.Other is identical with embodiment 4.

Filter joint on the 220kV power-line carrier channel adopts circuit as shown in Figure 2, and the main capacitance Cc of coupling capacitor is that 3300pF, low-voltage terminal stray capacitance Cx are 200pF, this filter joint circuit inductance L ₄Be 0.89mH, inductance L ₅Be 0.1mH, capacitor C ₂Be 2300pF, inductance L ₆For the no-load voltage ratio of 1.2mH, impedance transformer T is that 574/75 Ω, series arm capacitor C are 38997pF, reference carrier frequency is 68～500kHz.Original JL-400-B5 type filter joint, as shown in Figure 7, its operating frequency is 72～500kHz, narrow 4kHz.Impedance transformer high-frequency signal when being 20mA by power current just begins to distort.When power current reaches 500mA, the impedance transformer of filter joint will take place saturated, and carrier terminal equipment can not be worked, and filter joint circuit disclosed by the invention adds to 260V at power-frequency voltage, power current is zero, and the high-frequency signal attenuation does not take place increases phenomenon.Therefore by the proportioning and the increase series arm capacitor C of change K value, promptly overcome the adverse effect of low-voltage terminal stray capacitance, solved the problem that stops power current to disturb again.

Claims (7)

1. the method for designing of a carrier-filter joint circuit for power transmission line the steps include:

1) according to given line side resistance R i, coupling capacitor Cc, the coupling capacitor low-voltage terminal equivalent resistance R of stray capacitance Cx and carrier equipment over the ground _LActual parameter, make R _LOn power P ₂The value approximation signal source maximum power Pmax that may confess as far as possible, promptly return loss is big as far as possible, the pass of return loss and power is:

A _P＝0.5Ln(Pmax/(Pmax－P ₂)〕

2) according to baud decay integration theorem, the pass of deriving between return loss and the frequency is: ${\∫}_0^{\∞}{(A}_P/f^2)\mathrm{df}=2{\mathrm{\π}}^2\[\mathrm{Ri}\×\mathrm{Cc}-\mathrm{\Σ}(1/\mathrm{Zj})\]$

Then to desirable A _PThe theoretical boundary of the maximum return loss between the frequency band f1～f2 of characteristic is:

A _Pmax＝2π ²f ₁?f ₂〔Ri×Cc－∑(1/Z _j)〕/(f ₂－f ₁)

3) according to increasing f ₁～f ₂Return loss A in the frequency range _P, 0～f must draw up as far as possible ₁The low-frequency current of low-frequency range and the f that draws up in right amount ₂The rule of the high-frequency current of～∞ high band is selected the plurality purpose high pass components low-frequency current of drawing up for use, selects the fewer purpose low pass element high-frequency current of drawing up for use;

4) high pass components and low pass element are connected into the simplest trapezoidal reactance two-port network, the series arm capacitor C of network egress links to each other with the arrival end of carrier equipment, the inlet of network links to each other with line side coupling capacitor Cc, and the carrier equipment that the network terminal connect is used equivalent resistance R _LExpression, impedance transformer is inserted in the inside of two-port network;

5), make at f with the ratio K of preferred low pass element of optimization and high pass components with optimize and revise the parameter of circuit element repeatedly ₁～f ₂The component parameters of the filter circuit in the frequency range can compensate the influence of stray capacitance over the ground of coupling capacitance low-pressure end, makes return loss A _PMinimum value maximization, make A _PApproach return loss maximum limit A as much as possible _Pmax

6) draw final circuit structure, component value and circuit characteristic.

One kind in accordance with the method for claim 1 and the design filter joint circuit, it is between coupling capacitor and carrier equipment, form by reactance component and an impedance transformer, it is characterized in that forming the simplest trapezoidal reactance two-port network by reactance component, network egress is the series arm capacitor C, it directly links to each other with the arrival end of carrier equipment, impedance transformer T is plugged on network internal, wherein the ratio K of the number of low pass reactance component and high pass reactance component is between 0.25～0.5, i.e. 0.25≤K≤0.5.

3. filter joint circuit according to claim 2 is characterized in that the annexation of reactance component and impedance transformer T is from left to right: series arm low pass inductance L ₁, and arm high pass inductance L ₂, series arm high pass capacitor C ₁, and arm high pass inductance L ₃, impedance transformer T, series arm high pass capacitor C.

4. filter joint circuit according to claim 2 is characterized in that the annexation of reactance component and impedance transformer T is from left to right: and arm high pass inductance L ₄, series arm low pass inductance L ₅, series arm high pass capacitor C ₂, and arm high pass inductance L ₆, impedance transformer T, series arm high pass capacitor C.

5. filter joint circuit according to claim 2 is characterized in that the annexation of reactance component and impedance transformer T is from left to right: and arm high pass inductance L ₇, series arm high pass capacitor C ₃, and arm high pass inductance L ₈, series arm low pass inductance L ₉, impedance transformer T, series arm high pass capacitor C.

6. filter joint circuit according to claim 2 is characterized in that the annexation of reactance component and impedance transformer T is from left to right: series arm low pass inductance L ₁₀, and arm high pass inductance L ₁₁, impedance transformer T, series arm capacitor C.

7. filter joint circuit according to claim 2 is characterized in that the annexation of reactance component and impedance transformer T is from left to right: and arm high pass inductance L ₁₂, series arm low pass inductance L ₁₃, impedance transformer T, series arm capacitor C.

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