CN101593964A - The method for longitudinal zero-sequence power direction protection of double-circuit lines on the same pole - Google Patents

Abstract

The invention discloses a kind of method for longitudinal zero-sequence power direction protection that is used for double-circuit lines on the same pole; comprise this side zero sequence power direction criterion and offside zero sequence power direction criterion; this side zero sequence power direction criterion is that formula (I), offside zero sequence power direction criterion are formula (II), in the formula, and 3I _0M, 3I _0NBe this loop line M, N side zero-sequence current, 3I _0M', 3I _0N' be another loop line M, N side zero-sequence current, 3U _M0, 3U _N0Bus residual voltage for protection installation place M, N side; Arg represents the back measured phase angle mutually; K is the zero-sequence mutual inductance influence coefficient; more than the output of two criterion AND gates; more than satisfying simultaneously during two formulas; be earth fault to have occurred in the decidable protection zone, the action of longitudinal zero-sequence power direction protection criterion.

Description

The method for longitudinal zero-sequence power direction protection of double-circuit lines on the same pole

Technical field

The invention belongs to electricity field, be specifically related to a kind of method for longitudinal zero-sequence power direction protection of suitable double-circuit lines on the same pole.

Background technology

Double-circuit lines on the same pole because have that electric outgoing line corridor is narrow, transmission capacity is big, small investment, instant effect, can improve advantages such as power supply reliability, operation maintenance are simple, requirement such as can adapt to well that modern power systems is reliable, economy, transmission line capability are big has obtained using widely at present.Electrical link is not only arranged between double-circuit lines on the same pole; also there is the magnetic contact; exist bigger zero-sequence mutual inductance influence between the double-circuit lines on the same pole circuit; when a loop line wherein breaks down; also there is fault current to flow through in another loop line; the electric current and voltage of two loop lines interacts by mutual inductance; make residual voltage on the bus not only depend on the electric current of this line; also be subjected to the influence of another loop line electric current; this makes the protection problem of double-circuit lines on the same pole become complicated, the guard method that can not apply mechanically single back transmission line simply.

Because the influence of double loop zero-sequence mutual inductance can be flow through zero-sequence current in another loop line, the bus zero sequence residual voltage of protection installation place depended on the zero-sequence current in two loop lines when double-circuit line on same pole took place by the asymmetric ground connection of single loop line; When cross-line earth fault takes place, zero-sequence current is all arranged in two loop lines, the size and Orientation of zero-sequence current not only depends on fault type and system's zero-sequence impedance parameter, and is subjected to the influence of zero-sequence mutual inductance between two loop lines, the inconsistent phenomenon of zero-sequence current direction with single line down also might occur.The protection of vertical connection zero sequence direction is the most extensive and effectively one of the protection fast of present domestic use, plays an important role when faults such as developing fault, high resistance ground.Up to the present; the zero sequence power direction protection criterion of traditional double-circuit lines on the same pole is that the zero sequence power direction protection that will be used for single loop line is applied directly to double loop; and double loop is not done as a whole the configuration; when fault takes place; mutual inductance meeting between double loop causes electric current and voltage interaction between double loop; might cause the erroneous judgement or the tripping of zero sequence power direction protection criterion, zero sequence power direction protection criterion loses directivity.

Summary of the invention

At the deficiencies in the prior art, the technical problem to be solved in the present invention proposes a kind of method for longitudinal zero-sequence power direction protection of double-circuit lines on the same pole, to be applicable to the zero sequence power direction protection on double-circuit lines on the same pole road.

For solving the problems of the technologies described above, the present invention has adopted a kind of method for longitudinal zero-sequence power direction protection of double-circuit lines on the same pole, and this method comprises the steps:

(a) this side zero sequence power direction criterion part and offside zero sequence power direction criterion are set

This side zero sequence power direction criterion is:

In the formula, 3I _0MBe this loop line M side zero-sequence current, 3I ' _0MBe another loop line M side zero-sequence current, 3U _M0Be the bus residual voltage of protection installation place M side, Arg represent to the back measure phase angle mutually, K is the zero-sequence mutual inductance influence coefficient;

Offside zero sequence power direction criterion is:

In the formula, 3I _0NBe this loop line N side zero-sequence current, 3I ' _0NBe another loop line N side zero-sequence current, 3U _N0Be the bus residual voltage of protection installation place N side, Arg represent to the back measure phase angle mutually, K is the zero-sequence mutual inductance influence coefficient;

(b) decision making according to criterion

When satisfying (1) formula with (2) formula simultaneously, promptly in the decidable protection zone earth fault has appearred, the action of zero sequence power direction protection criterion; If only satisfy (1) formula or only satisfy (2) formula, then be judged to another loop line earth fault or external area error, protection is failure to actuate.

Described zero-sequence mutual inductance influence coefficient value is $K=\frac{{3Z}_M}{Z_0},$ In the formula, Z ₀Be the zero sequence impedance of circuit, ZM is mutual impedance between the double loop line.

The zero-sequence mutual inductance influence coefficient value of the method for longitudinal zero-sequence power direction protection that is applicable to double-circuit lines on the same pole that the present invention proposes is $K=\frac{{3Z}_M}{Z_0},$ In the formula, Z ₀Be the zero sequence impedance of circuit, Z _MBe mutual impedance between the double loop line.

Compare with the method for longitudinal zero-sequence power direction protection of existing parallel lines on same tower double back transmission line, longitudinal zero-sequence power direction protection criterion of the present invention has following characteristics:

1, longitudinal zero-sequence power direction protection criterion of the present invention disposes double loop with an integral body; optical fiber communication by communication and circuit two ends electric parameters between line; the zero-sequence current of zero-sequence current, residual voltage and another loop line of protection circuit offside is introduced in the protective device; carry out the differentiation of double loop internal fault and external fault, thereby improved the accuracy that the longitudinal zero-sequence power direction protection criterion is differentiated.

2, longitudinal zero-sequence power direction protection criterion of the present invention has been considered the influence of the zero-sequence mutual inductance between double loop; introduced the zero-sequence current of another loop line; improved the accuracy that longitudinal zero-sequence power direction protection criterion when cross line fault occurring between double loop is judged, and the double-circuit line on same pole longitudinal zero-sequence power direction protection criterion of present employing single back line longitudinal zero-sequence power direction protection criterion is judged easily when different name phase cross-line earth fault occurring between double loop by accident.

3, the longitudinal zero-sequence power direction protection criterion of the present invention internal and external fault of identification protecting circuit correctly can also correctly be discerned simultaneously which line down of double-circuit line.

Description of drawings

System schematic when Fig. 1 is applied to normally move double loop inside I line-to-ground fault for longitudinal zero-sequence power direction protection criterion of the present invention;

System schematic when Fig. 2 is applied to normally move the inner IBIIC of generation of double loop cross-line earth fault for longitudinal zero-sequence power direction protection criterion of the present invention.

Embodiment

Among Fig. 1, when the inner I loop line of double-circuit lines on the same pole generation single phase ground fault, this moment, M side bus residual voltage was

${\stackrel{\·}{U}}_{M0}={\stackrel{\·}{U}}_0+\mathrm{\α}{\stackrel{\·}{I}}_{01}{Z}_0---\left(3\right)$

In the formula:

Be M side bus residual voltage,

Be the M side zero-sequence current of circuit I,

Be earth point residual voltage, Z ₀Be the circuit zero sequence impedance, α is that the short dot distance accounts for the ratio of length completely; N side bus residual voltage is

${\stackrel{\·}{U}}_{N0}={\stackrel{\·}{U}}_0+(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}{Z}_0---\left(4\right)$

The zero-sequence current that II loop line both sides are flow through is

${\stackrel{\·}{I}}_{03}=-{\stackrel{\·}{I}}_{04}=\mathrm{\α}{\stackrel{\·}{I}}_{01}-(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}---\left(5\right)$

Therefore, for loop line I, consider that the zero sequence impedance angle of the longitudinal zero-sequence power direction protection criterion of zero sequence mutual impedance influence between loop line II line is

The longitudinal zero-sequence power direction protection criterion at 1,2 places action among the loop line I.For loop line II, consider that the zero sequence impedance angle of the longitudinal zero-sequence power direction protection criterion of zero sequence mutual impedance influence between loop line I line be (when near M side generation earth fault)

Because the criterion of the longitudinal zero-sequence power direction protection criterion of loop line II can not satisfy simultaneously, the longitudinal zero-sequence power direction protection criterion at 3,4 places is failure to actuate among the loop line II.

Among Fig. 2, when the inner generation of double loop IBIIC cross-line earth fault, the algebraical sum of the residual voltage that the bus residual voltage of M side and N side produces when being IB generation single-phase earthing and IIC generation single phase ground fault.The bus residual voltage that IE produces when single-phase earthing takes place is respectively

${\stackrel{\·}{U}}_{M0}^{\′}={\stackrel{\·}{U}}_{01}+\mathrm{\α}{\stackrel{\·}{I}}_{01}^{\′}{Z}_0$ ${\stackrel{\·}{U}}_{N0}^{\′}={\stackrel{\′}{U}}_{01}+(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}^{\′}{Z}_0$

The zero-sequence current that flows through in II loop line both sides is

${\stackrel{\·}{I}}_{03}^{\′}=-{\stackrel{\·}{I}}_{04}^{\′}=\mathrm{\α}{\stackrel{\·}{I}}_{01}^{\′}-(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}^{\′}$

The bus residual voltage that IIC produces when single phase ground fault takes place is respectively

${\stackrel{\·}{U}}_{M0}^{\′\′}={\stackrel{\·}{U}}_{02}+\mathrm{\α}{\stackrel{\·}{I}}_{03}^{\′\′}{Z}_0$ ${\stackrel{\·}{U}}_{N0}^{\′\′}={\stackrel{\·}{U}}_{02}+(1-\mathrm{\α}){\stackrel{\·}{I}}_{04}^{\′\′}{Z}_0$

The zero-sequence current that flows through in I loop line both sides is

${\stackrel{\·}{I}}_{01}^{\′\′}=-{\stackrel{\·}{I}}_{02}^{\′\′}=\mathrm{\α}{\stackrel{\·}{I}}_{03}^{\′\′}-(1-\mathrm{\α}){\stackrel{\·}{I}}_{04}^{\′\′}$

Therefore, when the inner generation of double loop IBIIC cross-line earth fault, M side bus residual voltage is

${\stackrel{\·}{U}}_{M0}={\stackrel{\·}{U}}_0+\mathrm{\α}({\stackrel{\·}{I}}_{01}^{\′}+{\stackrel{\·}{I}}_{03}^{\′\′})Z_0$

N side bus residual voltage is ${\stackrel{\·}{U}}_{N0}={\stackrel{\·}{U}}_0+(1-\mathrm{\α})({\stackrel{\·}{I}}_{02}^{\′}+{\stackrel{\·}{I}}_{04}^{\′\′})Z_0$

In the formula,

Be the total residual voltage phasor in fault point.The zero-sequence current that 1 effluent is crossed in the I loop line is

${\stackrel{\·}{I}}_{01}={\stackrel{\·}{I}}_{01}^{\′}+{\stackrel{\·}{I}}_{01}^{\′\′}={\stackrel{\·}{I}}_{01}^{\′}+\mathrm{\α}{\stackrel{\·}{I}}_{03}^{\′\′}-(1-\mathrm{\α}){\stackrel{\·}{I}}_{04}^{\′\′}$

The zero-sequence current that 2 effluents are crossed in the I loop line is

${\stackrel{\·}{I}}_{02}={\stackrel{\·}{I}}_{02}^{\′}+{\stackrel{\·}{I}}_{02}^{\′\′}={\stackrel{\·}{I}}_{02}^{\′}-\mathrm{\α}{\stackrel{\·}{I}}_{03}^{\′\′}+(1-\mathrm{\α}){\stackrel{\·}{I}}_{04}^{\′\′}$

The zero-sequence current that 3 effluents are crossed in the II loop line is

${\stackrel{\·}{I}}_{03}={\stackrel{\·}{I}}_{03}^{\′}+{\stackrel{\·}{I}}_{03}^{\′\′}=\mathrm{\α}{\stackrel{\·}{I}}_{01}^{\′}+{\stackrel{\·}{I}}_{03}^{\′\′}-(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}^{\′}$

The zero-sequence current that 4 effluents are crossed in the II loop line is

${\stackrel{\·}{I}}_{04}={\stackrel{\·}{I}}_{04}^{\′}+{\stackrel{\·}{I}}_{04}^{\′\′}={\stackrel{\·}{I}}_{04}^{\′\′}-\mathrm{\α}{\stackrel{\·}{I}}_{01}^{\′}+(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}^{\′}$

The bus residual voltage of M and N side is represented with the actual measurement zero-sequence current of circuit, after deriving, can be got

${\stackrel{\·}{U}}_{M0}={\stackrel{\·}{U}}_0+\mathrm{\α}{\stackrel{\·}{I}}_{01}{Z}_0+\mathrm{\α}(1-\mathrm{\α})({\stackrel{\·}{I}}_{03}+{\stackrel{\·}{I}}_{04})Z_0$

${\stackrel{\·}{U}}_{M0}={\stackrel{\·}{U}}_0+\mathrm{\α}{\stackrel{\·}{I}}_{03}{Z}_0+\mathrm{\α}(1-\mathrm{\α})({\stackrel{\·}{I}}_{01}+{\stackrel{\·}{I}}_{02})Z_0$

${\stackrel{\·}{U}}_{N0}{=\stackrel{\·}{U}}_0+(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}{Z}_0+\mathrm{\α}(1-\mathrm{\α})({\stackrel{\·}{I}}_{03}+{\stackrel{\·}{I}}_{04})Z_0$

${\stackrel{\·}{U}}_{N0}={\stackrel{\·}{U}}_0+(1-\mathrm{\α}){\stackrel{\·}{I}}_{04}{Z}_0+\mathrm{\α}(1-\mathrm{\α})({\stackrel{\·}{I}}_{01}+{\stackrel{\·}{I}}_{02})Z_0$

Can be got by above four formulas, the bus residual voltage of M and N side falls

$\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{MN}0}=\mathrm{\α}({\stackrel{\·}{I}}_{01}+{\stackrel{\·}{I}}_{03})Z_0-(1-\mathrm{\α})({\stackrel{\·}{I}}_{02}+{\stackrel{\·}{I}}_{04})Z_0$

And the bus residual voltage of M and N side falls also and can be expressed as

$\mathrm{\Δ}{\stackrel{\·}{U}}_{\mathrm{MN}0}=\mathrm{\α}{\stackrel{\·}{I}}_{01}(Z_0-Z_m)-(1-\mathrm{\α}){\stackrel{\·}{I}}_{02}(Z_0-Z_m)=\mathrm{\α}{\stackrel{\·}{I}}_{03}(Z_0-Z_m)-(1-\mathrm{\α}){\stackrel{\·}{I}}_{04}(Z_0-Z_m)$

Can get by above two formulas, ${\stackrel{\·}{I}}_{02}+{\stackrel{\·}{I}}_{04}=\frac{\mathrm{\α}}{1-\mathrm{\α}}({\stackrel{\·}{I}}_{01}+{\stackrel{\·}{I}}_{03})$

So the bus residual voltage of M and N side can be expressed as

${\stackrel{\·}{U}}_{M0}={\stackrel{\·}{U}}_0+\mathrm{\α}{Z}_0({\stackrel{\·}{I}}_{01}+{\stackrel{\·}{I}}_{03})$

${\stackrel{\·}{U}}_{N0}={\stackrel{\·}{U}}_0+(1-\mathrm{\α})Z_0({\stackrel{\·}{I}}_{02}+{\stackrel{\·}{I}}_{04})$

Therefore, for loop line I, consider that the zero sequence impedance angle of the longitudinal zero-sequence power direction protection criterion of zero sequence mutual impedance influence between loop line II line is

The longitudinal zero-sequence power direction protection criterion at 1,2 places action among the loop line I;

For loop line II, consider that the zero sequence impedance angle of the longitudinal zero-sequence power direction protection criterion of zero sequence mutual impedance influence between loop line I line be (when near M side generation earth fault)

Because the criterion of the longitudinal zero-sequence power direction protection criterion of loop line II also can satisfy simultaneously, the longitudinal zero-sequence power direction protection criterion at 3,4 places is also moved among the loop line II.

Claims (2)

1, a kind of method for longitudinal zero-sequence power direction protection of double-circuit lines on the same pole is characterized in that, this method comprises the steps:

(a) this side zero sequence power direction criterion part and offside zero sequence power direction criterion are set

This side zero sequence power direction criterion is:

In the formula, 3I _0MBe this loop line M side zero-sequence current, 3I ' _0MBe another loop line M side zero-sequence current, 3U _M0Be the bus residual voltage of protection installation place M side, Arg represent to the back measure phase angle mutually, K is the zero-sequence mutual inductance influence coefficient;

Offside zero sequence power direction criterion is:

In the formula, 3I _0NBe this loop line N side zero-sequence current, 3I ' _0NBe another loop line N side zero-sequence current, 3U _N0Be the bus residual voltage of protection installation place N side, Arg represent to the back measure phase angle mutually, K is the zero-sequence mutual inductance influence coefficient;

(b) decision making according to criterion

When satisfying (1) formula with (2) formula simultaneously, promptly in the decidable protection zone earth fault has appearred, the action of zero sequence power direction protection criterion; If only satisfy (1) formula or only satisfy (2) formula, then be judged to another loop line earth fault or external area error, protection is failure to actuate.

2, the zero sequence power direction guard method of double-circuit lines on the same pole as claimed in claim 1 is characterized in that, described zero-sequence mutual inductance influence coefficient value is $K=\frac{3Z_M}{Z_0},$ In the formula, Z ₀Be the zero sequence impedance of circuit, Z _MBe mutual impedance between the double loop line.

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