CN104950226A - Double-circuit non-homonymous phase interline grounding fault identification method based on position relative coefficient direction features - Google Patents

Abstract

The invention discloses a double-circuit non-homonymous phase interline grounding fault identification method based on position relative coefficient direction features. The method comprises the following steps that centralized parameter modeling is adopted; the zero sequence current of a second circuit of double same-pole parallel circuits is calculated; the zero sequence compensation current of a first circuit of the double same-pole parallel circuits is calculated; the fault phase voltage in the protection and adjusting range part of the first circuit of the double same-pole parallel circuits is calculated; the position relative coefficient in the protection and adjusting range part of the first circuit of the double same-pole parallel circuits is calculated; then, the position relative coefficient direction features of the non-homonymous phase interline grounding fault point and the protection and adjusting range part of the first circuit of the double same-pole parallel circuits are used for realizing the accurate identification of the double-circuit non-homonymous phase interline grounding fault; the identification result is not influenced by factors such as interline zero sequence mutual inductance, transition resistance, load current and electric power system operation mode, and the method is applicable to the same-pole parallel double-circuit single-end electric quantity backup protection.

Description

The non-same famous prime minister's cross-line ground fault recognition method of position-based relative coefficient directivity characteristics double-circuit line

Technical field

The present invention relates to Relay Protection Technology in Power System field, specifically relate to the non-same famous prime minister's cross-line ground fault recognition method of a kind of position-based relative coefficient directivity characteristics double-circuit line.

Background technology

Analyses for double circuits on same tower has that floor area is few, cost is low, connects operation of power networks reliable and stable, has become a kind of common transmission line of electricity connected mode of electric system.Zero-sequence mutual inductance is there is between analyses for double circuits on same tower line; zero-sequence mutual inductance has an impact to zero-utility theory; and then generation additional impedance; the additional impedance caused because of zero-sequence mutual inductance can cause protector measuring to fault impedance be greater than physical fault impedance; when causing close protection seting scope place generation earth fault in analyses for double circuits on same tower protected location; there is misoperation in protection, unfavorable to power network safety operation.

Even if analyses for double circuits on same tower occur through the direct earth fault of shaft tower, soil resistivity lower ground district's transition resistance also near 10 Ω; The local transition resistance higher in resistivity can reach 30 Ω, or even higher.The non-vanishing fault impedance that protective device is calculated of transition resistance, except comprising the fault impedance component of reaction true fault distance, further comprises the additional impedance produced because of transition resistance.The additional impedance that transition resistance produces is resistance sense or easily causes impedance ground distance protection tripping or steady-state in capacitance-resistance.False protection or tripping, can bring great loss to safe operation of power system, even likely can threaten the stability of electric system.

Acting characteristic round edge circle of existing analyses for double circuits on same tower ground distance protection is through true origin; because true origin is positioned on acting characteristic round edge circle; during protection forward outlet earth fault there is dead band in protection; and along with transition resistance and load current increase, protection forward outlet dead band is larger.Because true origin is positioned on acting characteristic round edge circle, there is the possibility of malfunction in protection in the other direction outlet earth fault, and transition resistance is larger, protection easier misoperation during protection opposite direction outlet earth fault.

Owing to there is very strong zero-sequence mutual inductance between analyses for double circuits on same tower line; existing ground distance protection cannot obtain the zero-sequence current on another loop line road; the impact of zero-sequence mutual inductance between line cannot be eliminated in algorithm model; by the impact of zero-sequence mutual inductance between line; when tradition ground distance protection is applied to analyses for double circuits on same tower, its protection domain will expand greatly; at protection seting scope place usually there is steady-state in fault; make easily misoperation to occur during protection external area error; easily cause the large transfer of trend, cause large area blackout and occur.

Summary of the invention

The object of the invention is to the deficiency overcoming prior art existence, there is provided a kind of position-based relative coefficient directivity characteristics double-circuit line non-same famous prime minister's cross-line ground fault recognition method, the method takes into account the impact of zero-sequence mutual inductance between line, the position relative coefficient directivity characteristics at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road is utilized to realize the accurate differentiation of the non-same famous prime minister's cross-line earth fault of double-circuit line, differentiate result not by zero-sequence mutual inductance between line, transition resistance, the impact of the factor such as load current and power system operation mode, be applicable to the back-up protection of analyses for double circuits on same tower single-end electrical quantity.

For completing above-mentioned purpose, the present invention adopts following technical scheme:

The non-same famous prime minister's cross-line ground fault recognition method of position-based relative coefficient directivity characteristics double-circuit line, is characterized in that, comprise following sequential steps:

(1) protector measuring analyses for double circuits on same tower I returns the faulted phase voltage of route protection installation place faulted phase current and zero-sequence current wherein, φ is fault phase; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase;

(2) protective device calculates the zero-sequence current on analyses for double circuits on same tower II loop line road

Wherein, $r_1={\sin }^{-1}\left(\frac{a_3{b}_1}{\sqrt{{\left(a_3{b}_1\right)}^2+{\left(a_1{b}_3\right)}^2}}\right);r_2={\sin }^{-1}\left(\frac{a_1{b}_2-a_2{b}_1}{\sqrt{{\left(a_3{b}_1\right)}^2+{\left(a_1{b}_3\right)}^2}}\right);a_1=\mathrm{Re}\left(\frac{{\stackrel{\·}{U}}_{I\mathrm{\φ}}}{Z_{I1}}\right);b_1=\mathrm{Im}\left(\frac{{\stackrel{\·}{U}}_{I\mathrm{\φ}}}{Z_{I1}}\right);$ $a_2=\mathrm{Re}({\stackrel{\·}{I}}_{I\mathrm{\φ}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\·}{I}}_{I0});b_2=Im({\stackrel{\·}{I}}_{I\mathrm{\φ}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\·}{I}}_{I0});a_3=b_3=\left|\frac{Z_m}{3Z_{I1}}{\stackrel{\·}{I}}_{I0}\right|;\mathrm{\β}=Arg\left(\frac{Z_m}{3Z_{I1}}{\stackrel{\·}{I}}_{I0}\right);$ Z _mfor the zero-sequence mutual inductance between analyses for double circuits on same tower I loop line road and analyses for double circuits on same tower II loop line road; Z _i0for the zero sequence impedance on analyses for double circuits on same tower I loop line road; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase; for real part; for imaginary part; for real part; for imaginary part; for amplitude; for phase angle; for arcsin function value; for arcsin function value; J is complex operator;

(3) protective device calculates the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road

$\mathrm{\Δ}\stackrel{\·}{I}={\stackrel{\·}{I}}_{I\mathrm{\φ}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\·}{I}}_{I0}+\frac{Z_m}{3Z_{I1}}{\stackrel{\·}{I}}_{II0}$

(4) protective device calculates analyses for double circuits on same tower I loop line road protection seting scope place l _setthe faulted phase voltage of point

$\stackrel{\·}{U}\left(l_{set}\right)={\stackrel{\·}{U}}_{I\mathrm{\φ}}-\frac{l_{set}}{l}{Z}_{I1}\mathrm{\Δ}\stackrel{\·}{I}$

Wherein, l is that analyses for double circuits on same tower I returns line length; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; for the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road; l _setfor analyses for double circuits on same tower I loop line road protection seting scope, get 0.85 times of analyses for double circuits on same tower I and return line length;

(5) protective device calculates the position relative coefficient at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road $p=\frac{\frac{\mathrm{Re}\left({\stackrel{\·}{U}}_{I\mathrm{\φ}}\right)\mathrm{Im}\left(\frac{Z_{I1}}{l}\mathrm{\Δ}\stackrel{\·}{I}\right)-\mathrm{Im}\left({\stackrel{\·}{U}}_{I\mathrm{\φ}}\right)\mathrm{Re}\left(\frac{Z_{I1}}{l}\mathrm{\Δ}\stackrel{\·}{I}\right)}{\mathrm{Im}\left(\frac{Z_{I1}}{l}\mathrm{\Δ}\stackrel{\·}{I}\right)\mathrm{Re}({\stackrel{\·}{I}}_{I0}+{\stackrel{\·}{I}}_{II0})-\mathrm{Re}\left(\frac{Z_{I1}}{l}\mathrm{\Δ}\stackrel{\·}{I}\right)\mathrm{Im}({\stackrel{\·}{I}}_{I0}+{\stackrel{\·}{I}}_{II0})}({\stackrel{\·}{I}}_{I0}+{\stackrel{\·}{I}}_{II0})-\stackrel{\·}{U}\left(l_{set}\right)}{\frac{Z_{I1}}{l}\mathrm{\Δ}\stackrel{\·}{I}};$

Wherein, l is that analyses for double circuits on same tower I returns line length; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase; for real part; for imaginary part; for real part; for imaginary part; for real part; for imaginary part; l _setfor analyses for double circuits on same tower I loop line road protection seting scope, get 0.85 times of analyses for double circuits on same tower I and return line length; for the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road;

(6) protective device judges whether the position relative coefficient p < 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road sets up, if set up, then judge that non-same famous prime minister's cross-line earth fault is positioned within the protection seting scope of analyses for double circuits on same tower I loop line road, send action trip signal;

(7) protective device judges whether the position relative coefficient p > 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road sets up; if set up; then judge that non-same famous prime minister's cross-line earth fault is positioned at outside the protection seting scope of analyses for double circuits on same tower I loop line road, send block signal.

Feature of the present invention and technological achievement:

The inventive method only uses single-ended single back line electric parameters, does not need to introduce another loop line road electric parameters, differentiates result not by the impact of power system operation mode, still has very high fault distinguishing accuracy when larger change occurs power system operation mode.The inventive method only uses single-ended single back line electric parameters, does not need to introduce another loop line road electric parameters, and Protection secondary circuit is separate does not go here and there mutually, strengthens fault distinguishing result accuracy.The inventive method takes into account the impact of zero-sequence mutual inductance between line, to eliminate between line zero-sequence mutual inductance to the impact of fault distinguishing result.The inventive method adopts lumped parameter modeling; the position relative coefficient directivity characteristics at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road is utilized to realize the accurate differentiation of the non-same famous prime minister's cross-line earth fault of double-circuit line; differentiate result not by the impact of the factors such as zero-sequence mutual inductance, transition resistance, load current and power system operation mode between line, be applicable to the back-up protection of analyses for double circuits on same tower single-end electrical quantity.

Accompanying drawing explanation

Fig. 1 is application analyses for double circuits on same tower transmission system schematic diagram of the present invention.

Embodiment

Fig. 1 is application analyses for double circuits on same tower transmission system schematic diagram of the present invention.In Fig. 1, PT is voltage transformer (VT), and CT is current transformer, and m, n are the two ends bus numbering of analyses for double circuits on same tower.Protector measuring analyses for double circuits on same tower I returns the faulted phase voltage of route protection installation place faulted phase current and zero-sequence current wherein, φ is fault phase; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase.

Protective device calculates the zero-sequence current on analyses for double circuits on same tower II loop line road

Wherein, $r_1={\sin }^{-1}\left(\frac{a_3{b}_1}{\sqrt{{\left(a_3{b}_1\right)}^2+{\left(a_1{b}_3\right)}^2}}\right);r_2={\sin }^{-1}\left(\frac{a_1{b}_2-a_2{b}_1}{\sqrt{{\left(a_3{b}_1\right)}^2+{\left(a_1{b}_3\right)}^2}}\right);a_1=\mathrm{Re}\left(\frac{{\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}}{Z_{I1}}\right);b_1=\mathrm{Im}\left(\frac{{\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}}{Z_{I1}}\right);$ $a_2=\mathrm{Re}({\stackrel{\&CenterDot;}{I}}_{I\mathrm{\&phi;}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0});b_2=Im({\stackrel{\&CenterDot;}{I}}_{I\mathrm{\&phi;}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0});a_3=b_3=\left|\frac{Z_m}{3Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}\right|;\mathrm{\&beta;}=Arg\left(\frac{Z_m}{3Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}\right);$ Z _mfor the zero-sequence mutual inductance between analyses for double circuits on same tower I loop line road and analyses for double circuits on same tower II loop line road; Z _i0for the zero sequence impedance on analyses for double circuits on same tower I loop line road; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase; for real part; for imaginary part; for real part; for imaginary part; for amplitude; for phase angle; for arcsin function value; for arcsin function value; J is complex operator; R1, r2 are intermediate variable, without actual physics meaning.

Protective device calculates the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road

$\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}={\stackrel{\&CenterDot;}{I}}_{I\mathrm{\&phi;}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}+\frac{Z_m}{3Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{II0}$

Protective device calculates analyses for double circuits on same tower I loop line road protection seting scope place l _setthe faulted phase voltage of point

$\stackrel{\&CenterDot;}{U}\left(l_{set}\right)={\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}-\frac{l_{set}}{l}{Z}_{I1}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}$

Wherein, l is that analyses for double circuits on same tower I returns line length; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; for the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road; l _setfor analyses for double circuits on same tower I loop line road protection seting scope, get 0.85 times of analyses for double circuits on same tower I and return line length.

Protective device calculates the position relative coefficient at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road $p=\frac{\frac{\mathrm{Re}\left({\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}\right)\mathrm{Im}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)-\mathrm{Im}\left({\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}\right)\mathrm{Re}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)}{\mathrm{Im}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)\mathrm{Re}({\stackrel{\&CenterDot;}{I}}_{I0}+{\stackrel{\&CenterDot;}{I}}_{II0})-\mathrm{Re}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)\mathrm{Im}({\stackrel{\&CenterDot;}{I}}_{I0}+{\stackrel{\&CenterDot;}{I}}_{II0})}({\stackrel{\&CenterDot;}{I}}_{I0}+{\stackrel{\&CenterDot;}{I}}_{II0})-\stackrel{\&CenterDot;}{U}\left(l_{set}\right)}{\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}};$

Wherein, l is that analyses for double circuits on same tower I returns line length; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase; for real part; for imaginary part; for real part; for imaginary part; for real part; for imaginary part; l _setfor analyses for double circuits on same tower I loop line road protection seting scope, get 0.85 times of analyses for double circuits on same tower I and return line length; for the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road.

If not be positioned within the protection seting scope of analyses for double circuits on same tower I loop line road with famous prime minister's cross-line earth fault, then the position relative coefficient p < 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road.If not be positioned at outside the protection seting scope of analyses for double circuits on same tower I loop line road with famous prime minister's cross-line earth fault, then the position relative coefficient p > 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road.According to this directivity characteristics of position relative coefficient, the non-same famous prime minister's cross-line earth fault identical criterion of a kind of double-circuit line is proposed as follows:

(1) protective device judges whether the position relative coefficient p < 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road sets up; if set up; then judge that non-same famous prime minister's cross-line earth fault is positioned within the protection seting scope of analyses for double circuits on same tower I loop line road, send action trip signal.

(2) protective device judges whether the position relative coefficient p > 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road sets up; if set up; then judge that non-same famous prime minister's cross-line earth fault is positioned at outside the protection seting scope of analyses for double circuits on same tower I loop line road, send block signal.

The inventive method only uses single-ended single back line electric parameters, does not need to introduce another loop line road electric parameters, differentiates result not by the impact of power system operation mode, still has very high fault distinguishing accuracy when larger change occurs power system operation mode.The inventive method only uses single-ended single back line electric parameters, does not need to introduce another loop line road electric parameters, and Protection secondary circuit is separate does not go here and there mutually, strengthens fault distinguishing result accuracy.The inventive method takes into account the impact of zero-sequence mutual inductance between line, to eliminate between line zero-sequence mutual inductance to the impact of fault distinguishing result.The inventive method adopts lumped parameter modeling; the position relative coefficient directivity characteristics at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road is utilized to realize the accurate differentiation of the non-same famous prime minister's cross-line earth fault of double-circuit line; differentiate result not by the impact of the factors such as zero-sequence mutual inductance, transition resistance, load current and power system operation mode between line, be applicable to the back-up protection of analyses for double circuits on same tower single-end electrical quantity.

The foregoing is only preferred embodiment of the present invention; but protection scope of the present invention is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the present invention discloses, the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.

Claims (1)

1. the non-same famous prime minister's cross-line ground fault recognition method of position-based relative coefficient directivity characteristics double-circuit line, is characterized in that, comprise following sequential steps:

(1) protective device protector measuring analyses for double circuits on same tower I returns the faulted phase voltage of route protection installation place faulted phase current and zero-sequence current wherein, φ is fault phase; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase.

(2) protective device calculates the zero-sequence current on analyses for double circuits on same tower II loop line road

Wherein, $r_1={\sin }^{-1}\left(\frac{a_3{b}_1}{\sqrt{{\left(a_3{b}_1\right)}^2+{\left(a_1{b}_3\right)}^2}}\right);r_2={\sin }^{-1}\left(\frac{a_1{b}_2-a_2{b}_1}{\sqrt{{\left(a_3{b}_1\right)}^2+{\left(a_1{b}_3\right)}^2}}\right);a_1=\mathrm{Re}\left(\frac{{\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}}{Z_{I1}}\right);b_1=\mathrm{Im}\left(\frac{{\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}}{Z_{I1}}\right);$ $a_2=\mathrm{Re}\left({\stackrel{\&CenterDot;}{I}}_{I\mathrm{\&phi;}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}\right);b_2=\mathrm{Im}\left({\stackrel{\&CenterDot;}{I}}_{I\mathrm{\&phi;}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}\right);a_3=b_3=\left|\frac{Z_m}{3Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}\right|;\mathrm{\&beta;}=Arg\left(\frac{Z_m}{3Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}\right);$ Z _mfor the zero-sequence mutual inductance between analyses for double circuits on same tower I loop line road and analyses for double circuits on same tower II loop line road; Z _i0for the zero sequence impedance on analyses for double circuits on same tower I loop line road; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase; for real part; for imaginary part; for real part; for imaginary part; for amplitude; for phase angle; for arcsin function value; for arcsin function value; J is complex operator.

(3) protective device calculates the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road

$\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}={\stackrel{\&CenterDot;}{I}}_{I\mathrm{\&phi;}}+\frac{Z_{I0}-Z_{I1}}{Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{I0}+\frac{Z_m}{3Z_{I1}}{\stackrel{\&CenterDot;}{I}}_{II0}$

(4) protective device calculates analyses for double circuits on same tower I loop line road protection seting scope place l _setthe faulted phase voltage of point

$\stackrel{\&CenterDot;}{U}\left(l_{set}\right)={\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}-\frac{l_{set}}{l}{Z}_{I1}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}$

Wherein, l is that analyses for double circuits on same tower I returns line length; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; for the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road; l _setfor analyses for double circuits on same tower I loop line road protection seting scope, get 0.85 times of analyses for double circuits on same tower I and return line length;

(5) protective device calculates the position relative coefficient at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road $p=\frac{\frac{\mathrm{Re}\left({\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}\right)lm\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)-\mathrm{Im}\left({\stackrel{\&CenterDot;}{U}}_{I\mathrm{\&phi;}}\right)\mathrm{Re}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)}{\mathrm{Im}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)\mathrm{Re}({\stackrel{\&CenterDot;}{I}}_{I0}+{\stackrel{\&CenterDot;}{I}}_{II0})-\mathrm{Re}\left(\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}\right)\mathrm{Im}({\stackrel{\&CenterDot;}{I}}_{I0}+{\stackrel{\&CenterDot;}{I}}_{II0})}({\stackrel{\&CenterDot;}{I}}_{I0}+{\stackrel{\&CenterDot;}{I}}_{II0})-\stackrel{\&CenterDot;}{U}\left(l_{set}\right)}{\frac{Z_{I1}}{l}\mathrm{\&Delta;}\stackrel{\&CenterDot;}{I}};$

Wherein, l is that analyses for double circuits on same tower I returns line length; Z _i1for the positive sequence impedance on analyses for double circuits on same tower I loop line road; φ=I loop line road A phase, I loop line road B phase, I loop line road C phase; for real part; for imaginary part; for real part; for imaginary part; for real part; for imaginary part; l _setfor analyses for double circuits on same tower I loop line road protection seting scope, get 0.85 times of analyses for double circuits on same tower I and return line length; for the zero sequence compensation electric current on analyses for double circuits on same tower I loop line road;

(6) protective device judges whether the position relative coefficient p < 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road sets up, if set up, then judge that non-same famous prime minister's cross-line earth fault is positioned within the protection seting scope of analyses for double circuits on same tower I loop line road, send action trip signal;

(7) protective device judges whether the position relative coefficient p > 0 at non-same famous prime minister's cross-line earth fault and protection seting scope place, analyses for double circuits on same tower I loop line road sets up; if set up; then judge that non-same famous prime minister's cross-line earth fault is positioned at outside the protection seting scope of analyses for double circuits on same tower I loop line road, send block signal.