CN105510733A - Parameter measurement method for high-voltage and ultra-high-voltage direct-current transmission lines - Google Patents

Abstract

The embodiments of the invention disclose a parameter measurement method for high-voltage and ultra-high-voltage direct-current transmission lines. According to the method, a direct-current transmission line model having distributed-parameter characteristics is constructed. Meanwhile, the expression of the impedance per unit length and the admittance per unit length, corresponding to the direct-current transmission line model, is established, wherein the earth resistance is involved. During the resolving process of a mathematical model, a homogeneous differential equation between the voltage and the current of the line in the boundary condition is solved to obtain a two-port power transmission line equation, wherein a telegraph equation is involved. After that, assisted by the open-circuit measurement means and the short-circuit measurement means at the end of the transmission line, the open-circuit impedance and the short-circuit impedance at the sending terminal of the transmission line are respectively measured. Furthermore, the distribution parameters of the direct-current transmission line are solved out and a computational formula for the earth resistance per unit length is given. According to the technical scheme of the invention, initial measurement data are acquired through constructing the transmission line model. Meanwhile, the two-port power transmission line equation is solved accurately. Therefore, the precise distribution parameters of the direct-current transmission line can be obtained.

Description

The measurement method of parameters of a kind of high pressure, extra high voltage direct current transmission line

Technical field

The present invention relates to HVDC (High Voltage Direct Current) transmission line correlative technology field, particularly relate to the measurement method of parameters of a kind of high pressure, extra high voltage direct current transmission line.

Background technology

HVDC transmission line is typical long range distribution parametric circuit.In operation, because harmonic resonance phenomenon may be there is in circuit, so need to be grasped outside the direct current resistance of transmission line of electricity, distributed capacitance and the distributed inductance of transmission line of electricity also should be grasped.In addition, the measurement parameter of transmission line of electricity is the authentic data source of system load flow stability Calculation, and wherein accurate model of power transmission system plays outstanding importance in circuit parameter measurement.

In prior art, the method obtaining transmission line parameter is off-line measurement.But the short-circuit impedance of circuit is regarded as equivalent impedance of concentrating pi-network by the method simply, and the half of open-circuit impedance inverse is used as equivalent shunt admittance of concentrating pi-network.If the length of circuit is within 100km, its error still can accept, but along with line length increase, error will enlarge markedly.In order to obtain the measurement parameter of long distance line, also have by the multinomial Tailor progression of hyperbolic function in telegraph equation is similar to.

But the approximate of any finite term Tailor progression all can bring truncation error, and this truncation error increases along with the increase of line length, so along with line length increase, transmission line parameter error also can increase.

Summary of the invention

The measurement method of parameters of a kind of high pressure, extra high voltage direct current transmission line is provided in the embodiment of the present invention, of the prior art for long distance transmission line of electricity to solve, the problem that measuring error is large.

In order to solve the problems of the technologies described above, the embodiment of the invention discloses following technical scheme:

A measurement method of parameters for high pressure, extra high voltage direct current transmission line, comprising:

Build the DC power transmission line model with characteristics of distributed parameters, set up the expression formula of the unit length impedance corresponding with described DC power transmission line model and admittance, wherein, relate to ground resistance;

According to described DC power transmission line model, described unit length impedance and described unit length admittance, calculate the voltage increment equation in described DC power transmission line and current increment equation respectively;

According to described voltage increment equation and described current increment equation, calculate the homogeneous difference equation of the voltage and current in described DC power transmission line respectively;

According to described DC power transmission line sending end and the voltage of receiving end, the boundary condition of electric current, the homogeneous difference equation of described voltage and current is solved, draw the two-port transmission line of electricity equation corresponding with described DC power transmission line length wherein, relate to telegraph equation;

Applying different measuring voltages by measuring power supply in the sending end of described DC power transmission line, measuring open-circuit impedance and the short-circuit impedance of described DC power transmission line respectively;

According to described two-port transmission line of electricity equation, described open-circuit impedance and described short-circuit impedance, calculate the distribution parameter of described DC power transmission line.

Preferably, described structure has the DC power transmission line model of characteristics of distributed parameters, comprising:

Structure has the single direct current transmission line parameter model under the earth echo plex mode of characteristics of distributed parameters or builds the bipolar direct current transmission line model with characteristics of distributed parameters.

Preferably, the expression formula of the unit length impedance that described foundation is corresponding with described DC power transmission line model and admittance, comprising:

Set up the conductor impedance z=r+r of the unit length corresponding with described single direct current transmission line parameter model _g+ j ω l and wire admittance y=g+j ω c ₀, or set up self-impedance z=r+j ω l and the self-admittance y=g+j ω c of the monopolar line corresponding with described bipolar direct current transmission line model ₀;

Wherein, r is the resistance of circuit unit length, r _gfor the ground resistance of unit length, g is the conductance over the ground of unit length, and l is the self-induction of circuit unit length, c ₀for the ground capacitance of unit length, ω is system angle frequency.

Preferably, described according to described DC power transmission line sending end and the voltage of receiving end, the boundary condition of electric current, the homogeneous difference equation of described voltage and the homogeneous difference equation of institute's electric current are solved, comprising:

According to the sending end voltage of described single DC power transmission line sending end electric current by terminal voltage with receiving end electric current the homogeneous difference equation of voltage of described single DC power transmission line and the homogeneous difference equation of electric current are solved, draws the two-port transmission line of electricity equation corresponding with described single direct current transmission line length D $\left[\begin{array}{c}{\stackrel{\·}{U}}_s\\ {\stackrel{\·}{I}}_s\end{array}\right]=\left[\begin{array}{cc}\cosh \mathrm{\γ}D& z_c\sinh \mathrm{\γ}D\\ \frac{\sinh \mathrm{\γ}D}{z_c}& \cosh \mathrm{\γ}D\end{array}\right]\left[\begin{array}{c}{\stackrel{\·}{U}}_r\\ {\stackrel{\·}{I}}_r\end{array}\right];$

Wherein, z _cbe characteristic impedance, γ is propagation coefficient.

Preferably, described by measure power supply apply different measuring voltages in the sending end of described DC power transmission line, measure open-circuit impedance and the short-circuit impedance of described transmission line of electricity respectively, comprising:

Voltage is applied in sending end by measuring power supply make the receiving end shorted to earth of single DC power transmission line, measure the short-circuit impedance Z of described single transmission line of electricity in sending end _s;

Voltage is applied in sending end by measuring power supply make the receiving end of described single DC power transmission line unsettled, measure the open-circuit impedance Z of described single transmission line of electricity in sending end _o.

Preferably, described by measure power supply apply different measuring voltages in the sending end of described DC power transmission line, measure open-circuit impedance and the short-circuit impedance of described transmission line of electricity respectively, comprising:

By in parallel for the sending end of the positive pole circuit of bipolar direct current transmission line and negative pole circuit, between described bipolar direct current transmission line and current conversion station earthing device, applying residual voltage by measuring power supply, measuring the zero sequence open-circuit impedance Z under described bipolar direct current transmission line receiving end open-circuit condition respectively _o0and the zero sequence short-circuit impedance Z under short circuit condition _s0;

Between the sending end positive pole and negative pole of described bipolar direct current transmission line, apply positive sequence voltage by described measurement power supply, measure the positive sequence open-circuit impedance Z under described bipolar direct current transmission line receiving end open-circuit condition respectively _o1and the positive sequence short-circuit impedance Z under short circuit condition _s1.

Preferably, described distribution parameter comprises resistance, the over the ground conductance of monopolar D. C transmission line of electricity unit length, self-induction and ground capacitance, and the mutual inductance of unit length and coupling capacitance between bipolar direct current transmission line.

Preferably, described measurement method of parameters also comprises:

The frequency setting described measurement power supply is respectively first frequency f _s-Δ f and second frequency f _sby interpolation calculation ,+Δ f, show that the frequency of described measurement power supply is f _spositive order parameter and Zero sequence parameter, wherein, f _sfor work frequency, Δ f > 0.

Preferably, described measurement method of parameters also comprises:

Change the frequency of described measurement power supply, obtain the change curve of the resistance of monopolar D. C transmission line of electricity unit length and the frequency change of the corresponding described measurement power supply of self-induction.

Preferably, the frequency range of described measurement power supply is 30-2000Hz.

From above technical scheme, a kind of high pressure that the embodiment of the present invention provides, the measurement method of parameters of extra high voltage direct current transmission line, build the DC power transmission line model with characteristics of distributed parameters, set up the expression formula of the unit length impedance corresponding with described DC power transmission line model and admittance, wherein, ground resistance is related to; In the resolving of mathematical model, by setting up the corresponding two-port transmission line of electricity equation of described DC power transmission line length, wherein, described two-port transmission line of electricity equation relates to telegraph equation, then the metering system by DC power transmission line terminal open circuit and short circuit is aided with, measure open-circuit impedance and the short-circuit impedance of DC power transmission line sending end respectively, and then solve the distribution parameter of described DC power transmission line, and give the computing formula of unit length ground resistance especially.The embodiment of the present invention obtains initial measurement data by constructed two-port transmission line of electricity equation and model of power transmission system; simultaneously by carrying out the calculation procedures such as Exact Solution to two-port transmission line of electricity equation; obtain the accurate distribution parameter of described DC power transmission line; so the measurement method of parameters that the embodiment of the present invention provides, accurate DC power transmission line parameter can be provided for protection seting, line fault location, RTDS/EMTDC emulation.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, for those of ordinary skills, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.

The schematic flow sheet of a kind of high pressure that Fig. 1 provides for the embodiment of the present invention, the measurement method of parameters method of extra high voltage direct current transmission line;

A kind of single direct current transmission line parameter model schematic had under the earth echo plex mode of characteristics of distributed parameters that Fig. 2 provides for the embodiment of the present invention;

A kind of bipolar direct current transmission line model schematic with characteristics of distributed parameters that Fig. 3 provides for the embodiment of the present invention;

The zero sequence open-circuit impedance instrumentation plan of the bipolar direct current transmission line that Fig. 4 provides for the embodiment of the present invention;

The zero sequence short-circuit impedance instrumentation plan of the bipolar direct current transmission line that Fig. 5 provides for the embodiment of the present invention;

The positive sequence open-circuit impedance instrumentation plan of the bipolar direct current transmission line that Fig. 6 provides for the embodiment of the present invention;

The positive sequence short-circuit impedance instrumentation plan of the bipolar direct current transmission line that Fig. 7 provides for the embodiment of the present invention.

Embodiment

Technical scheme in the present invention is understood better in order to make those skilled in the art person, below in conjunction with the accompanying drawing in the embodiment of the present invention, technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, should belong to the scope of protection of the invention.

See Fig. 1, the schematic flow sheet of the measurement method of parameters method of a kind of high pressure that the embodiment of the present invention provides, extra high voltage direct current transmission line, specifically comprises the following steps:

Step S101: build the DC power transmission line model with characteristics of distributed parameters, sets up the expression formula of the unit length impedance corresponding with described DC power transmission line model and admittance, wherein, relates to ground resistance.

DC power transmission line is returned for solid conductor the earth, as shown in Figure 2, structure has the single direct current transmission line parameter model under the earth echo plex mode of characteristics of distributed parameters, and sets up the conductor impedance z=r+r corresponding with described single direct current transmission line parameter model _g+ j ω l and wire admittance y=g+j ω c ₀.

For bipolar direct current transmission line, as shown in Figure 3, be bipolar direct current transmission line model.Because bipolar direct current transmission line is symmetrical about shaft tower, so the self-impedance z=r+j ω l of two monopolar lines and self-admittance y=g+j ω c ₀identical.Meanwhile, also there is coupling capacitance c between bipolar line _mwith mutual inductance m, if the current imbalance in described bipolar direct current transmission line, then there is part out-of-balance current by ground resistance r _greturn.

Step S102: according to described DC power transmission line model, described unit length impedance and described unit length admittance, calculate the voltage increment equation in described DC power transmission line and current increment equation respectively.

Return DC power transmission line for solid conductor the earth, voltage and current Incremental Equation along the line is respectively $\frac{d\stackrel{\·}{U}}{dx}=(r+r_g+j\mathrm{\ω}l)\stackrel{\·}{I}=z\stackrel{\·}{I},\frac{d\stackrel{\·}{I}}{dx}=(g+j\mathrm{\ω}c)\stackrel{\·}{U}=y\stackrel{\·}{U}.$

For bipolar direct current transmission line, positive pole (under be designated as p) and negative pole (under the voltage increment equation be designated as on n) transmission line of electricity be respectively: $\frac{d{\stackrel{\·}{U}}_p}{dx}=z{\stackrel{\·}{I}}_p+j\mathrm{\ω}m{\stackrel{\·}{I}}_n+r_g({\stackrel{\·}{I}}_p+{\stackrel{\·}{I}}_n),\frac{d{\stackrel{\·}{U}}_n}{dx}=z{\stackrel{\·}{I}}_n+j\mathrm{\ω}m{\stackrel{\·}{I}}_p+r_g({\stackrel{\·}{I}}_p+{\stackrel{\·}{I}}_n),$

Current increment equation is respectively $\frac{d{\stackrel{\·}{I}}_p}{dx}=y{\stackrel{\·}{U}}_p+{\mathrm{j\ωc}}_m({\stackrel{\·}{U}}_p-{\stackrel{\·}{U}}_n),\frac{d{\stackrel{\·}{I}}_n}{dx}=y{\stackrel{\·}{U}}_n+{\mathrm{j\ωc}}_m({\stackrel{\·}{U}}_n-{\stackrel{\·}{U}}_p).$

Step S103: according to described voltage increment equation and described current increment equation, calculate the homogeneous difference equation of the voltage and current in described DC power transmission line respectively.

Step S104: according to described DC power transmission line sending end and the voltage of receiving end, the boundary condition of electric current, the homogeneous difference equation of described voltage and current is solved, draw the two-port transmission line of electricity equation corresponding with described DC power transmission line length, wherein, relate to telegraph equation.

For described DC power transmission line, described given described DC power transmission line sending end and receiving end boundary condition with under (subscript ' s ' represents sending end, and subscript ' r ' represents receiving end), the homogeneous solution of difference equation of described voltage and current constitutes the two-port transmission line of electricity equation that length is D:

$\left[\begin{array}{c}{\stackrel{\·}{U}}_s\\ {\stackrel{\·}{I}}_s\end{array}\right]=\left[\begin{array}{cc}\cosh \mathrm{\γ}D& z_c\sinh \mathrm{\γ}D\\ \frac{\sinh \mathrm{\γ}D}{z_c}& \cosh \mathrm{\γ}D\end{array}\right]\left[\begin{array}{c}{\stackrel{\·}{U}}_r\\ {\stackrel{\·}{I}}_r\end{array}\right]$

Wherein, z _cbe characteristic impedance, γ is propagation coefficient.

Step S105: applying different measuring voltages by measuring power supply in the sending end of described DC power transmission line, measuring open-circuit impedance and the short-circuit impedance of described DC power transmission line respectively.

Applying different measuring voltages by measuring power supply in the sending end of described DC power transmission line, measuring the open-circuit impedance under described DC power transmission line receiving end open-circuit condition and the short-circuit impedance under short circuit condition respectively.

For bipolar direct current transmission line, described measuring voltage comprises residual voltage and positive sequence voltage.

Step S106: according to described two-port transmission line of electricity equation, described open-circuit impedance and described short-circuit impedance, calculate the distribution parameter of described DC power transmission line.

Under the condition of described DC power transmission line receiving end open circuit, to described two-port transmission line of electricity equation solution, just can obtain described open-circuit impedance and z _cwith the open-circuit impedance formula of γ.

Under the condition of described DC power transmission line by terminal shortcircuit, to described two-port transmission line of electricity equation solution, just can obtain described short-circuit impedance and z _cwith the short-circuit impedance equation of γ.

According to described open-circuit impedance formula, short-circuit impedance formula, and the expression formula of the unit length impedance of setting up in step S101 and admittance, carry out the computing of getting real part or imaginary part, the distribution parameter of described DC power transmission line can be drawn.

By above-mentioned implementation step, the embodiment of the present invention obtains initial measurement data by constructed two-port transmission line of electricity equation and model of power transmission system, the calculation procedures such as Exact Solution are carried out to described two-port transmission line of electricity equation simultaneously, just can obtain the distribution parameter of described DC power transmission line.

Below in conjunction with the single DC power transmission line of the earth echo plex mode and bipolar direct current transmission line, one progressive explanation is done to the invention process.

Embodiment one

As shown in Figure 2, the single direct current transmission line parameter model had under the earth echo plex mode of characteristics of distributed parameters is built.

According to described single direct current transmission line parameter model, the impedance obtaining unit length is z=r+r _g+ j ω l, wherein includes ground resistance r _g, the admittance of unit length is y=g+j ω c ₀.

Wherein, r is the resistance of circuit unit length, r _gfor the ground resistance of unit length, g is the conductance over the ground of unit length, and l is the self-induction of circuit unit length, c ₀for the ground capacitance of unit length, ω is system angle frequency.

According to impedance and the admittance of described unit length, show that the voltage and current Incremental Equation of transmission line of electricity is respectively:

$\frac{d\stackrel{\·}{U}}{dx}=(r+r_g+j\mathrm{\ω}l)\stackrel{\·}{I}=z\stackrel{\·}{I}---\left(1\right)$

$\frac{d\stackrel{\·}{I}}{dx}=(g+{\mathrm{j\ωc}}_0)\stackrel{\·}{U}=y\stackrel{\·}{U}---\left(2\right)$

And then the homogeneous difference equation of the voltage and current drawn in described DC power transmission line is:

$\frac{d^2\stackrel{\·}{U}}{{\mathrm{dx}}^2}=zy\stackrel{\·}{U}---\left(3\right)$

$\frac{d^2\stackrel{\·}{I}}{{\mathrm{dx}}^2}=zy\stackrel{\·}{I}---\left(4\right)$

Given described single DC power transmission line sending end and receiving end boundary condition with under (subscript ' s ' represents sending end, and subscript ' r ' represents receiving end), (3) formula and (4) formula be deconstructed into the two-port transmission line of electricity equation that length is D:

$\left[\begin{array}{c}{\stackrel{\·}{U}}_s\\ {\stackrel{\·}{I}}_s\end{array}\right]=\left[\begin{array}{cc}\cosh \mathrm{\γ}D& z_c\sinh \mathrm{\γ}D\\ \frac{\sinh \mathrm{\γ}D}{z_c}& \cosh \mathrm{\γ}D\end{array}\right]\left[\begin{array}{c}{\stackrel{\·}{U}}_r\\ {\stackrel{\·}{I}}_r\end{array}\right]---\left(5\right)$

Wherein, $z_c=\sqrt{z/y}---\left(6\right)$

$\mathrm{\γ}=\sqrt{zy}=\mathrm{\α}+j\mathrm{\β}---\left(7\right)$

In (6) formula and (7) formula, z _cbe characteristic impedance, γ is propagation coefficient.

By the receiving end shorted to earth of described single DC power transmission line, namely and apply voltage in sending end by measuring power supply then at the short-circuit impedance Z of sending end measuring circuit _sfor:

$Z_S={\stackrel{\·}{U}}_s/{\stackrel{\·}{I}}_s=z_c\tanh \mathrm{\γ}D---\left(8\right)$

By unsettled for the receiving end of described single DC power transmission line, namely and apply voltage in sending end by described measurement power supply then can measure the open-circuit impedance Z of circuit _ofor

$Z_O={\stackrel{\·}{U}}_s/{\stackrel{\·}{I}}_s=z_c\coth \mathrm{\γ}D---\left(9\right)$

By (8) formula and (9) formula, the characteristic impedance z of described single DC power transmission line can be extrapolated _cbe respectively with propagation coefficient γ:

$z_c=\sqrt{Z_S{Z}_O}---\left(10\right)$

$\mathrm{\γ}=\frac{{\coth }^{-1}\sqrt{Z_O/Z_S}}{D}---\left(11\right)$

Fortran is carried out to (6) formula and (7) formula simultaneously, draws:

z＝z _cγ(12)

y＝γ/z _c(13)

According to (10)-(13) formula, to the impedance z=r+r of described unit length _gthe admittance y=g+j ω c of+j ω l and described unit length ₀in carry out the calculating of getting real part and imaginary part, just can derive distribution parameter r, g, l and c of described single DC power transmission line ₀, wherein, r _gcan be obtained by measurement.

Embodiment two

As shown in Figure 3, the bipolar direct current transmission line parameter model with characteristics of distributed parameters is built.

According to described bipolar direct current transmission line parameter model, and bipolar direct current transmission line is symmetrical about shaft tower, draws self-impedance z=r+j ω l and the self-admittance y=g+j ω c of two monopolar lines ₀identical, also there is coupling capacitance c between described bipolar direct current transmission line _mwith mutual inductance m, and if the current imbalance in bipolar line, then there is part out-of-balance current by ground resistance r _greturn.

According to described bipolar direct current transmission line parameter model, can draw positive pole (under be designated as p) and negative pole (under the voltage increment equation be designated as on n) transmission line of electricity be respectively:

$\frac{d{\stackrel{\·}{U}}_p}{dx}=z{\stackrel{\·}{I}}_p+j\mathrm{\ω}m{\stackrel{\·}{I}}_n+r_g({\stackrel{\·}{I}}_p+{\stackrel{\·}{I}}_n)---\left(14\right)$

$\frac{d{\stackrel{\·}{U}}_n}{dx}=z{\stackrel{\·}{I}}_n+j\mathrm{\ω}m{\stackrel{\·}{I}}_p+r_g({\stackrel{\·}{I}}_p+{\stackrel{\·}{I}}_n)---\left(15\right)$

Meanwhile, the current increment equation on positive pole and negative pole transmission line of electricity is respectively:

$\frac{d{\stackrel{\·}{I}}_p}{dx}=y{\stackrel{\·}{U}}_p+{\mathrm{j\ωc}}_m({\stackrel{\·}{U}}_p-{\stackrel{\·}{U}}_n)---\left(16\right)$

$\frac{d{\stackrel{\·}{I}}_n}{dx}=y{\stackrel{\·}{U}}_n+{\mathrm{j\ωc}}_m({\stackrel{\·}{U}}_n-{\stackrel{\·}{U}}_p)---\left(17\right)$

Carry out applying the differential equation under residual voltage condition and parameter measurement to described bipolar direct current transmission line, specifically comprise:

Step S201: as shown in Figure 4, by parallel for the sending end of positive pole and negative pole circuit, and applies residual voltage by measuring power supply between circuit and current conversion station earthing device measure described bipolar direct current transmission line receiving end open-circuit condition under open-circuit impedance Z _o0.

Step S202: as shown in Figure 5, by parallel for the sending end of positive pole and negative pole circuit, and applies residual voltage by measuring power supply between circuit and current conversion station earthing device measure described bipolar direct current transmission line receiving end receiving end shorted to earth short-circuit impedance Z under condition _s0.

According to step S201 and step S202, show that positive pole and the corresponding residual voltage of negative pole and current differential equation are respectively:

$\frac{d({\stackrel{\·}{U}}_p+{\stackrel{\·}{U}}_n)}{dx}=(z+2r_g+j\mathrm{\ω}m)({\stackrel{\·}{I}}_p+{\stackrel{\·}{I}}_n)---\left(18\right)$

$\frac{d({\stackrel{\·}{I}}_p+{\stackrel{\·}{I}}_n)}{dx}=y({\stackrel{\·}{U}}_p+{\stackrel{\·}{U}}_n)---\left(19\right)$

Due to and so (18) formula and (19) formula can be rewritten as:

$\frac{d\stackrel{\·}{U}}{dx}=(z+2r_g+j\mathrm{\ω}m)(\stackrel{\·}{I}/2)---\left(20\right)$

$\frac{d(\stackrel{\·}{I}/2)}{dx}=y\stackrel{\·}{U}---\left(21\right)$

(20) formula and (21) formula are similar to (1) formula and (2) formula, therefore zero sequence characteristic impedance z in form _{c, 0}with propagation coefficient γ ₀be respectively:

$z_{c,0}=\sqrt{\frac{z+2r_g+j\mathrm{\ω}m}{y}}=\sqrt{Z_{S0}{Z}_{O0}}---\left(22\right)$

${\mathrm{\γ}}_0=\sqrt{(z+2r_g+j\mathrm{\ω}m)y}=\frac{{\coth }^{-1}\sqrt{Z_{O0}/Z_{S0}}}{D}---\left(23\right)$

So the Zero sequence parameter of the unit length of described bipolar direct current transmission line is:

z ₀＝z _c,0.γ ₀＝z+2r _g+jωm＝r+2r _g+jω(l+m)(24)

y ₀＝γ ₀/z _c,0＝y＝g+jωc ₀(25)

Carry out applying the differential equation under positive sequence voltage condition and parameter measurement to described bipolar direct current transmission line, specifically comprise:

Step S301: as shown in Figure 6, applies positive sequence voltage by measuring power supply between the positive pole and negative pole of described bipolar direct current transmission line sending end when measuring described bipolar direct current transmission line receiving end open circuit positive sequence open-circuit impedance Z _o1.

Step S302: as shown in Figure 7, applies positive sequence voltage by measuring power supply between the positive pole and negative pole of described bipolar direct current transmission line sending end when measuring described bipolar direct current transmission line by terminal shortcircuit positive sequence short-circuit impedance Z _s1.

According to step S201 and step S202, show that positive pole and the corresponding positive sequence voltage of negative pole and current increment equation are respectively:

$\frac{d({\stackrel{\·}{U}}_p-{\stackrel{\·}{U}}_n)}{dx}=(z-j\mathrm{\ω}m)({\stackrel{\·}{I}}_p-{\stackrel{\·}{I}}_n)---\left(26\right)$

$\frac{d({\stackrel{\·}{I}}_p-{\stackrel{\·}{I}}_n)}{dx}=(y+2{\mathrm{j\ωc}}_m)({\stackrel{\·}{U}}_p-{\stackrel{\·}{U}}_n)---\left(27\right)$

Due to and so (26) formula and (27) formula can be rewritten as:

$\frac{d\stackrel{\·}{U}}{dx}=(z-j\mathrm{\ω}m)\stackrel{\·}{I}---\left(28\right)$

$\frac{d\stackrel{\·}{I}}{dx}=(y+2{\mathrm{j\ωc}}_m)\stackrel{\·}{U}---\left(29\right)$

(28) formula and (29) formula are similar to (1) formula and (2) formula, therefore positive sequence characteristic impedance z in form _{c, 1}with propagation coefficient γ ₁be respectively:

$z_{c,1}=\sqrt{\frac{z-j\mathrm{\ω}m}{y+2{\mathrm{j\ωc}}_m}}=\sqrt{Z_{S1}{Z}_{O1}}---\left(30\right)$

${\mathrm{\γ}}_1=\sqrt{\[(z-j\mathrm{\ω}m)(y+2{\mathrm{j\ωc}}_m)}=\frac{{\coth }^{-1}\sqrt{Z_{O1}/Z_{S1}}}{D}---\left(31\right)$

So the positive order parameter of the unit length of described bipolar direct current transmission line is:

z ₁＝z _c,1.γ ₁＝z-jωm＝r+jω(l-m)(32)

y ₁＝γ ₁/z _c,1＝y+2jωc _m＝g+jω(c ₀+2c _m)(33)

At the positive order parameter z of the unit length of the described bipolar direct current transmission line of acquisition ₁, y ₁with Zero sequence parameter z ₀, y ₀after, just can derive the distribution parameter of described bipolar direct current transmission line, specifically comprise:

The resistance r of the one pole transmission line of electricity unit length in described bipolar direct current transmission line and over the ground conductance g are respectively:

r＝Re(z ₁)(34)

g＝Re(y ₁)(35)

Ground resistance have in bipolar line zero-sequence current by time work, the ground resistance r of its unit length _gfor:

$r_g=\frac{\mathrm{Re}\left(z_0\right)-r}{2}---\left(36\right)$

The self-induction l of the one pole transmission line of electricity unit length in described bipolar direct current transmission line and ground capacitance c ₀be respectively:

$l=\frac{\mathrm{Im}\left(z_0+z_1\right)}{2\mathrm{\ω}}---\left(37\right)$

$c_0=\frac{Im\left(y_0\right)}{2\mathrm{\ω}}---\left(38\right)$

The mutual inductance m of unit length and coupling capacitance c between bipolar line in described bipolar direct current transmission line _mbe respectively:

$m=\frac{\mathrm{Im}\left(z_0-z_1\right)}{2\mathrm{\ω}}---\left(39\right)$

$c_m=\frac{\mathrm{Im}\left(y_1-y_0\right)}{2\mathrm{\ω}}---\left(40\right)$

(34)-(38) formula is all under a certain specified measurement frequency, measure zero sequence impedance Z by described measurement power supply _o0, Z _s0with positive sequence impedance Z _o1, Z _s1calculate.

But, the AC resistance of one pole transmission line of electricity with there is kelvin effect, namely with frequency dependence.According to Carson formula, even if ground resistivity remains unchanged, the self-induction of monopolar line also with frequency dependence, wherein, described one pole transmission line of electricity comprises the circuit in described single DC power transmission line and the negative or positive electrode transmission line of electricity in described bipolar direct current transmission line.

So by changing the frequency of described measurement power supply, the resistance and the change curve of self-induction in 30-2000Hz frequency range that obtain monopolar D. C transmission line of electricity unit length can be measured one by one, certainly, is not limited to described frequency range.

Further, obtain described bipolar direct current transmission line, the parameter under AC power frequency frequency in order to measure, and don't close on power frequency line influence voltage and faradic interference as being subject to, the present embodiment selects the frequency f near power frequency _s-Δ f and f _smeasure respectively under+Δ f, then obtain the distribution parameter under work frequency by the mode of interpolation.Meanwhile, at selection survey frequency f _s-Δ f and f _sduring+Δ f, the natural resonance frequency avoiding described DC power transmission line be noted.

The present embodiment additionally provides and is applied in south electric network Pu'er-overseas Chinese hometown ± 800kVUHVDC transmission line of electricity by the measurement method of parameters of above-mentioned bipolar direct current transmission line, carries out parameter measurements checking.

Described UHVDC transmission line of electricity total length 1441km, the radius of 6 split conductors is 450mm, and the model of single split conductor is LGJ-630/45 and radius is 18.6mm.Minor increment between bipolar line is 22m, and steel tower over the ground average height is 33.5m, and sag is 16m.

Environment temperature during parameter measurement to described UHVDC transmission line of electricity is 14.2 DEG C, and humidity is 53.2%.The maximum induced voltage of monopolar line under receiving end shorted to earth and open-circuit condition is 300V.In order to avoid the impact of line-frequency induction signal, the flat rate of 40Hz and 60Hz during measurement, is selected to measure zero sequence impedance Z respectively _o0, Z _s0with positive sequence impedance Z _o1, Z _s1.

Table one be into the positive order parameter of 50Hz unit length that obtains of interpolation calculation and Zero sequence parameter.

Table one:

Table two, every distribution parameter of described UHVDC transmission line of electricity unit length under 50Hz frequency, and described every distribution parameter parameter calculates according to the result of table one.

Table two:

Parameter	Unit	Measured value	Calculated value
				Resistance, r	mΩ/km	7.37	7.38
Inductance, l	mH/km	1.2356	1.2358
				Ground capacitance, c0	μF/km	0.0101	0.00132
Mutual inductance, m	mH/km	0.4456	0.4429
				Coupling capacitance, cm	μF/km	0.0019	0.0018

The calculated value of table two is the design loads obtained according to geometry and the size of circuit.By relatively finding, measurement result and design load are identical.Actual result during difference between the two mainly uses ground resistivity in designing and calculating and measures is inconsistent to be caused, and the line-to-ground height change of reality is larger.The line crossing in such as some location is between two hilltops, and its result is exactly measure the ground capacitance obtained to be less than calculated value.

In sum, the present embodiment proposes the HVDC (High Voltage Direct Current) transmission line distributed parameter model of improvement, and gives Computation distribution resistance, self-inductance, ground capacitance, the analytic expression of bipolar line mutual inductance, coupling capacitance.Namely above-mentioned portion parameter can be obtained by the open-circuit impedance under the positive sequence of measuring circuit and zero sequence condition, short-circuit impedance.

Simultaneously; the reliable measuring accuracy of the embodiment of the present invention passes through field demonstration; and compare with the calculated results, both are highly consistent, prove that the embodiment of the present invention can provide accurate transmission line parameter for protection seting, line fault location, RTDS/EMTDC emulation.In addition, embodiment of the present invention Theories and methods also establishes theoretical foundation for IEEEP1893 project of standard development " DC power transmission line and ground electrode circuit parameter directive/guide ".

It should be noted that, in this article, the such as relational terms of " first " and " second " etc. and so on is only used for an entity or operation to separate with another entity or operational zone, and not necessarily requires or imply the relation that there is any this reality between these entities or operation or sequentially.And, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thus make to comprise the process of a series of key element, method, article or equipment and not only comprise those key elements, but also comprise other key elements clearly do not listed, or also comprise by the intrinsic key element of this process, method, article or equipment.When not more restrictions, the key element limited by statement " comprising ... ", and be not precluded within process, method, article or the equipment comprising described key element and also there is other identical element.

The above is only the specific embodiment of the present invention, those skilled in the art is understood or realizes the present invention.To be apparent to one skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein can without departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.

Claims (10)

1. a measurement method of parameters for high pressure, extra high voltage direct current transmission line, is characterized in that, comprising:

Build the DC power transmission line model with characteristics of distributed parameters, set up the expression formula of the unit length impedance corresponding with described DC power transmission line model and admittance, wherein, relate to ground resistance;

According to described DC power transmission line model, described unit length impedance and described unit length admittance, calculate the voltage increment equation in described DC power transmission line and current increment equation respectively;

According to described voltage increment equation and described current increment equation, calculate the homogeneous difference equation of the voltage and current in described DC power transmission line respectively;

According to described DC power transmission line sending end and the voltage of receiving end, the boundary condition of electric current, the homogeneous difference equation of described voltage and current is solved, draw the two-port transmission line of electricity equation corresponding with described DC power transmission line length, wherein, relate to telegraph equation;

Applying different measuring voltages by measuring power supply in the sending end of described DC power transmission line, measuring open-circuit impedance and the short-circuit impedance of described DC power transmission line respectively;

According to described two-port transmission line of electricity equation, described open-circuit impedance and described short-circuit impedance, calculate the distribution parameter of described DC power transmission line.

2. the measurement method of parameters of high pressure according to claim 1, extra high voltage direct current transmission line, is characterized in that, described structure has the DC power transmission line model of characteristics of distributed parameters, comprising:

Structure has the single direct current transmission line parameter model under the earth echo plex mode of characteristics of distributed parameters or builds the bipolar direct current transmission line model with characteristics of distributed parameters.

3. the measurement method of parameters of high pressure according to claim 2, extra high voltage direct current transmission line, is characterized in that, the impedance of unit length that described foundation is corresponding with described DC power transmission line model and the expression formula of admittance, comprising:

Set up the conductor impedance z=r+r corresponding with described single direct current transmission line parameter model _g+ j ω l and wire admittance y=g+j ω c ₀, or set up self-impedance z=r+j ω l and the self-admittance y=g+j ω c of the monopolar line corresponding with described bipolar direct current transmission line model ₀;

Wherein, r is the resistance of circuit unit length, r _gfor the ground resistance of unit length, g is the conductance over the ground of unit length, and l is the self-induction of circuit unit length, c ₀for the ground capacitance of unit length, ω is system angle frequency.

4. the measurement method of parameters of high pressure according to claim 3, extra high voltage direct current transmission line, it is characterized in that, described according to described DC power transmission line sending end and the voltage of receiving end, the boundary condition of electric current, the homogeneous difference equation of described voltage and the homogeneous difference equation of institute's electric current are solved, comprising:

According to the sending end voltage of described single DC power transmission line sending end electric current by terminal voltage with receiving end electric current the homogeneous difference equation of voltage of described single DC power transmission line and the homogeneous difference equation of electric current are solved, draws the two-port transmission line of electricity equation corresponding with described single direct current transmission line length D

Wherein, z _cbe characteristic impedance, γ is propagation coefficient.

5. the measurement method of parameters of high pressure according to claim 1, extra high voltage direct current transmission line, it is characterized in that, described by measure power supply apply different measuring voltages in the sending end of described DC power transmission line, measure open-circuit impedance and the short-circuit impedance of described transmission line of electricity respectively, comprising:

Voltage is applied in sending end by measuring power supply make the receiving end shorted to earth of single DC power transmission line, measure the short-circuit impedance Z of described single transmission line of electricity in sending end _s;

Voltage is applied in sending end by measuring power supply make the receiving end of described single DC power transmission line unsettled, measure the open-circuit impedance Z of described single transmission line of electricity in sending end _o.

6. the measurement method of parameters of high pressure according to claim 1, extra high voltage direct current transmission line, it is characterized in that, described by measure power supply apply different measuring voltages in the sending end of described DC power transmission line, measure open-circuit impedance and the short-circuit impedance of described transmission line of electricity respectively, comprising:

By in parallel for the sending end of the positive pole circuit of bipolar direct current transmission line and negative pole circuit, between described bipolar direct current transmission line and current conversion station earthing device, applying residual voltage by measuring power supply, measuring the zero sequence open-circuit impedance Z under described bipolar direct current transmission line receiving end open-circuit condition respectively _o0and the zero sequence short-circuit impedance Z under short circuit condition _s0;

Between the sending end positive pole and negative pole of described bipolar direct current transmission line, apply positive sequence voltage by described measurement power supply, measure the positive sequence open-circuit impedance Z under described bipolar direct current transmission line receiving end open-circuit condition respectively _o1and the positive sequence short-circuit impedance Z under short circuit condition _s1.

7. the measurement method of parameters of high pressure according to claim 1, extra high voltage direct current transmission line, is characterized in that,

Described distribution parameter comprises resistance, the over the ground conductance of monopolar D. C transmission line of electricity unit length, self-induction and ground capacitance, and the mutual inductance of unit length and coupling capacitance between bipolar direct current transmission line.

8. the measurement method of parameters of high pressure according to claim 6, extra high voltage direct current transmission line, is characterized in that, described measurement method of parameters also comprises:

The frequency setting described measurement power supply is respectively first frequency f _s-Δ f and second frequency f _sby interpolation calculation ,+Δ f, show that the frequency of described measurement power supply is f _spositive order parameter and Zero sequence parameter, wherein, f _sfor work frequency, Δ f > 0.

9. the high pressure according to claim 3 or 4, the measurement method of parameters of extra high voltage direct current transmission line, is characterized in that, described measurement method of parameters also comprises:

Change the frequency of described measurement power supply, obtain the change curve of the resistance of described monopolar line and the frequency change of the corresponding described measurement power supply of self-induction.

10. the measurement method of parameters of high pressure according to claim 9, extra high voltage direct current transmission line, is characterized in that, the frequency range of described measurement power supply is 30-2000Hz.