CN111665415A - Cross-voltage-class same-tower four-circuit-line fault line selection method and device - Google Patents

Cross-voltage-class same-tower four-circuit-line fault line selection method and device Download PDF

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CN111665415A
CN111665415A CN202010440898.XA CN202010440898A CN111665415A CN 111665415 A CN111665415 A CN 111665415A CN 202010440898 A CN202010440898 A CN 202010440898A CN 111665415 A CN111665415 A CN 111665415A
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line
fault
loop
impedance
matrix
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郭培育
许滢
王永锋
陈清
赵欣
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Nanjing Guodian Nanzi New Energy Engineering Technology Co ltd
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Nanjing Guodian Nanzi New Energy Engineering Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/58—Testing of lines, cables or conductors

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Abstract

The invention discloses a cross-voltage-class same-tower four-circuit line fault line selection method and a device, which comprises the following processes: obtaining a line model impedance matrix; carrying out phase-mode transformation processing on the line model impedance matrix Z to obtain mutually independent current and voltage moduli; and analyzing the relation between the independent current moduli to judge fault line selection. The invention realizes the fault line selection judgment of the same-tower four-circuit transmission line across voltage grades.

Description

Cross-voltage-class same-tower four-circuit-line fault line selection method and device
Technical Field
The invention belongs to the technical field of fault judgment, and particularly relates to a cross-voltage-class same-tower four-circuit-line fault line selection method and device.
Background
The same-tower multi-circuit line has narrow power transmission corridor, can improve the land utilization rate and the power transmission capacity, has greater cost advantage and is widely applied to a power system. With the development of power grid technology, a same-pole double-circuit system has a certain scale, and recently, a four-circuit system with different voltage levels, namely a four-circuit system consisting of 2 same-pole double-circuit lines with different voltage levels, has the main characteristics of line-to-line mutual inductance, numerous fault types and complex relay protection calculation and configuration. When a power transmission line has a fault, how to identify a fault line (fault line selection) in time at the first time is a problem to be solved urgently at present.
At present, many researches on the same-tower four-circuit lines with the same voltage grade are conducted at home and abroad, and the researches mainly focus on fault line selection, phase selection, fault analysis, fault distance measurement, relay protection and the like. However, the research on the same-tower four-circuit line of the cross-voltage grade is less, the fault analysis, the short-circuit current calculation, the fault distance measurement and the like are mainly focused, and the line selection principle of the cross-voltage same-tower four-circuit line is not researched.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a cross-voltage-grade same-tower four-circuit line fault line selection method and device, which are used for judging fault line selection of a cross-voltage-grade same-tower four-circuit power transmission line.
In order to solve the technical problem, the invention provides a cross-voltage-class same-tower four-circuit line fault line selection method, which is characterized by comprising the following steps of:
obtaining a line model impedance matrix;
carrying out phase-mode transformation processing on the line model impedance matrix Z to obtain mutually independent current and voltage moduli;
and analyzing the relation between the independent current moduli to judge fault line selection.
Further, the line model impedance matrix is:
Figure BDA0002504096480000021
wherein, the self-impedance of the I and II return lines is zl1And the mutual impedance between phases is zm1(ii) a The self-impedance of the III and IV loops is zl2And the mutual impedance between phases is zm2(ii) a The mutual impedance between the I and II return lines is zp1(ii) a The mutual impedance between the lines of the III and IV loops is zp2(ii) a The mutual impedance between the I loop, the III loop and the II loop and the IV loop is equal to each other and is zq1(ii) a The mutual impedance between the I loop, the IV loop and the II loop and the III loop is equal to zq2。
Further, the performing a phase-mode transformation process on the line model impedance matrix Z includes:
because two double-circuit lines with the same voltage level exist in the four circuit lines on the same tower, the two circuit lines with the same voltage level are subjected to line-to-line decoupling, and a double-circuit line decoupling matrix P is obtained through derivation1Comprises the following steps:
Figure BDA0002504096480000031
after the two double-circuit lines with the same voltage level are respectively decoupled, a matrix P is utilized1And deriving a matrix suitable for decoupling each loop of the four loops on the same tower:
Figure BDA0002504096480000032
the matrix is transformed as follows:
Z1＝P-1ZP (4)
after matrix transformation, an impedance matrix Z is obtained1Is composed of
Figure BDA0002504096480000033
Wherein: a is11＝Zl1+2Zm1+3Zp1；a12＝Zl1+2Zm1-3Zp1；a21＝Zl2+2Zm2+3Zp2；a22＝Zl2+2Zm2-3Zp2；b1＝Zl1-Zm1；b2＝Zl2-Zm2；
The impedance matrix Z obtained by the transformation of the above equation (5)1It can be seen that the off-diagonal elements of the line moduli 2, 3, 5, 6, 8, 9, 11, 12 are all zero except for the ground moduli 1, 4, 7, 10, indicating that these eight line moduli are completely decoupled from each other and independent of each other;
and (3) jointly solving the formula (1) and the formula (4), and deducing the voltage and current moduli as follows:
Figure BDA0002504096480000041
wherein:
Figure BDA0002504096480000042
Figure BDA0002504096480000043
Figure BDA0002504096480000044
Figure BDA0002504096480000045
Figure BDA0002504096480000046
representing 12 voltage moduli obtained after phase-mode conversion;
Figure BDA0002504096480000047
the 12 current moduli obtained after phase-mode conversion are shown.
Further, the analyzing the relationship between the independent current moduli to perform fault line selection judgment includes:
the current modulus characteristic after the phase-mode conversion is researched, and the relation rule between the fault component current and the modulus is as follows:
Figure BDA0002504096480000051
definition K1，K2，K3，K4Four parameters:
Figure BDA0002504096480000052
Figure BDA0002504096480000053
Figure BDA0002504096480000054
Figure BDA0002504096480000055
① when only K is present1Is greater than true, and K2＞、K3＞、K4If no, the current modulus I is indicated2And I3At least one value is far greater than zero, and only the I return line is judged to have a fault;
② when only K is present2Is greater than true, and K1＞、K3＞、K4If no, the current modulus I is indicated5And I6At least one value is far greater than zero, and only the II return line is judged to have a fault;
③ when only K is present3Is greater than true, and K1＞、K2＞、K4If no, the current modulus I is indicated8And I9At least one value is far greater than zero, and only the III return line is judged to have a fault;
④ when only K is present4Is greater than true, and K1＞、K2＞、K3When the two are not satisfied, the modulus current I is indicated11And I12At least one value is far greater than zero, and only the IV loop is judged to have a fault;
⑤ if K1＞、K2＞、K3＞、K4If more than two are satisfied at the same time, then judgeA cross-line fault is determined to occur;
⑥ if formula K1＞、K2＞、K3＞、K4If not, judging that the four circuit lines on the same tower are in a normal operation state;
among these, the threshold value is used.
Further, for the dynamic threshold, the calculation formula is:
＝40％×max{K1,K2,K3,K4} (12)。
correspondingly, the invention also provides a cross-voltage-class same-tower four-circuit line fault line selection device, which is characterized by comprising an impedance matrix acquisition module, a phase-mode conversion module and a fault line selection judgment module, wherein:
the impedance matrix obtaining module is used for obtaining a line model impedance matrix;
the phase-mode transformation module is used for carrying out phase-mode transformation processing on the line model impedance matrix Z to obtain mutually independent current and voltage moduli;
and the fault line selection judgment module is used for analyzing the relation between the independent current moduli to judge fault line selection.
Further, the line model impedance matrix is:
Figure BDA0002504096480000071
wherein, the self-impedance of the I and II return lines is zl1And the mutual impedance between phases is zm1(ii) a The self-impedance of the III and IV loops is zl2And the mutual impedance between phases is zm2(ii) a The mutual impedance between the I and II return lines is zp1(ii) a The mutual impedance between the lines of the III and IV loops is zp2(ii) a The mutual impedance between the I loop, the III loop and the II loop and the IV loop is equal to each other and is zq1(ii) a The mutual impedance between the I loop, the IV loop and the II loop and the III loop is equal to zq2。
Further, in the phase-to-analog conversion module, the performing phase-to-analog conversion processing on the line model impedance matrix Z includes:
because of four times of the same towerTwo double-circuit lines with the same voltage level exist in the line, so that the two double-circuit lines with the same voltage level are subjected to line-to-line decoupling, and a double-circuit line decoupling matrix P is obtained through derivation1Comprises the following steps:
Figure BDA0002504096480000072
after the two double-circuit lines with the same voltage level are respectively decoupled, a matrix P is utilized1And deriving a matrix suitable for decoupling each loop of the four loops on the same tower:
Figure BDA0002504096480000081
the matrix is transformed as follows:
Z1＝P-1ZP (4)
after matrix transformation, an impedance matrix Z is obtained1Is composed of
Figure BDA0002504096480000082
Wherein: a is11＝Zl1+2Zm1+3Zp1；a12＝Zl1+2Zm1-3Zp1；a21＝Zl2+2Zm2+3Zp2；a22＝Zl2+2Zm2-3Zp2；b1＝Zl1-Zm1；b2＝Zl2-Zm2；
The impedance matrix Z obtained by the transformation of the above equation (5)1It can be seen that the off-diagonal elements of the line moduli 2, 3, 5, 6, 8, 9, 11, 12 are all zero except for the ground moduli 1, 4, 7, 10, indicating that these eight line moduli are completely decoupled from each other and independent of each other;
and (3) jointly solving the formula (1) and the formula (4), and deducing the voltage and current moduli as follows:
Figure BDA0002504096480000083
wherein:
Figure BDA0002504096480000091
Figure BDA0002504096480000092
Figure BDA0002504096480000093
Figure BDA0002504096480000094
Figure BDA0002504096480000095
representing 12 voltage moduli obtained after phase-mode conversion;
Figure BDA0002504096480000096
the 12 current moduli obtained after phase-mode conversion are shown.
Further, in the fault line selection judging module, the analyzing the relationship between the independent current moduli to perform fault line selection judgment includes:
the current modulus characteristic after the phase-mode conversion is researched, and the relation rule between the fault component current and the modulus is as follows:
Figure BDA0002504096480000097
definition K1，K2，K3，K4Four parameters:
Figure BDA0002504096480000101
Figure BDA0002504096480000102
Figure BDA0002504096480000103
Figure BDA0002504096480000104
① when only K is present1Is greater than true, and K2＞、K3＞、K4If no, the current modulus I is indicated2And I3At least one value is far greater than zero, and only the I return line is judged to have a fault;
② when only K is present2Is greater than true, and K1＞、K3＞、K4If no, the current modulus I is indicated5And I6At least one value is far greater than zero, and only the II return line is judged to have a fault;
③ when only K is present3Is greater than true, and K1＞、K2＞、K4If no, the current modulus I is indicated8And I9At least one value is far greater than zero, and only the III return line is judged to have a fault;
④ when only K is present4Is greater than true, and K1＞、K2＞、K3When the two are not satisfied, the modulus current I is indicated11And I12At least one value is far greater than zero, and only the IV loop is judged to have a fault;
⑤ if K1＞、K2＞、K3＞、K4If more than two conditions are satisfied at the same time, judging that the cross-line fault occurs;
⑥ if formula K1＞、K2＞、K3＞、K4If not, judging that the four circuit lines on the same tower are in a normal operation state;
among these, the threshold value is used.
Further, for the dynamic threshold, the calculation formula is:
＝40％×max{K1,K2,K3,K4} (12)。
compared with the prior art, the invention has the following beneficial effects: the invention can realize the fault line selection of the same-tower four-circuit transmission line with the voltage grade, and provides a solution for solving the problem of the fault line selection of the line model.
Drawings
FIG. 1 is a same tower four-circuit line model across voltage classes;
FIG. 2 is a diagram showing the relationship between the three-phase self-impedance and the inter-phase impedance of the loop I (II);
FIG. 3 is the relationship between the three-phase self-impedance and the inter-phase impedance of the III (IV) loop;
FIG. 4 is a same tower four loop impedance model across voltage levels;
FIG. 5 is a propagation law of moduli on phases;
FIG. 6 is a PSCAD/EMTDC simulation model for four loops of the same tower across voltage;
fig. 7 is a PSCAD power transmission line tower model.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The noun explains:
(1) four circuit lines on the same tower: the four power transmission lines are simultaneously erected on the same tower.
(2) The voltage class is crossed: the voltage grades of all the loops on the same line tower are different, for example, the voltage grades of the loops I and II are 220kV, and the voltage grades of the loops III and IV are 500 kV.
(3) Phase-mode conversion: the phasors of the current and voltage are converted into mutually independent moduli through matrix change.
(4) Fault line selection: also called fault line identification, a certain transmission line (phase) with a fault is selected.
(5) PSCAD/EMTDC simulation: and building a power transmission line model through a PSCAD/EMTDC software platform, and testing the accuracy of the fault line selection method provided by the invention when various faults occur in the power transmission line model.
The invention conception in the invention is as follows: the same-tower four-circuit transmission line with the voltage-crossing grade is taken as a research object, and the ground mode component and the mutually independent line mode component which are kept electrically coupled are obtained through the double-circuit decoupling matrix in the time domain. By analyzing the relation between the induction line module component and the phase current of each loop, the four-loop fault line selection method suitable for the voltage-crossing grade is provided.
The invention relates to a cross-voltage-level same-tower four-circuit line fault line selection method, which is shown in fig. 1 and comprises the following steps:
step 1, obtaining a line model impedance matrix;
the research object of the invention is a system structure of four transmission lines on the same tower with different voltage levels (cross voltage), wherein two of the four transmission lines share a bus, and as shown in fig. 1, M, N and P, Q are sequentially I, II, III and IV transmission lines from top to bottom, wherein: eM、ENA power supply at two ends of a loop M, N is provided for I and II, and the voltage grade is 220 kV; zsm and Zsn are power supply impedances of M, N ends respectively; eP、EQA power supply at two ends of the III and IV loop P, Q, and the voltage grade is 500 kV; zsp and Zsq are power supply impedances at P, Q ends respectively.
In the circuit model shown in FIG. 1, assuming uniform transposition in single loops of four loops I, II, III and IV, as shown in FIG. 2, the self-impedance of the loops I and II is zl1And the mutual impedance between phases is zm1(ii) a The impedance matrixes in the I loop and the II loop are zs 1; as shown in FIG. 3, the self-impedance of the III and IV loops is zl2And the mutual impedance between phases is zm2(ii) a The internal impedance matrixes of the III and IV loops are zs 2;
as shown in FIG. 4, the impedance model of the same tower four-circuit line considering the impedance between the circuit lines, i and ii, the mutual impedance between the circuit lines is zp1(ii) a The mutual impedance between the lines of the III and IV loops is zp2(ii) a The mutual impedance between the I loop, the III loop and the II loop and the IV loop is equal to each other and is zq1(ii) a The mutual impedance between the I loop, the IV loop and the II loop and the III loop is equal to zq2。
As can be seen from fig. 2, the self-impedance and the inter-line mutual impedance of the respective loops are not completely equal. The relationship among the voltage, the current and the impedance is as follows:
Figure BDA0002504096480000131
wherein:
Figure BDA0002504096480000132
Figure BDA0002504096480000133
the phase A voltage magnitude values of the loops I, II, III and IV are shown;
Figure BDA0002504096480000134
Figure BDA0002504096480000135
representing phase B voltage magnitude values of loops I, II, III and IV;
Figure BDA0002504096480000136
representing phase C voltage magnitude values of loops I, II, III and IV;
Figure BDA0002504096480000137
Figure BDA0002504096480000138
the phase A voltage magnitude values of the loops I, II, III and IV are shown;
Figure BDA0002504096480000139
Figure BDA00025040964800001310
representing phase B voltage magnitude values of loops I, II, III and IV;
Figure BDA00025040964800001311
shows the loop C of I, II, III, IVPhase voltage phasor values;
Figure BDA00025040964800001312
representing an impedance matrix formed by the self impedance of the four lines on the same tower and the impedance among the lines;
the impedance matrixes formed by three-phase self impedance and interphase impedance in the I and II loop wires are the same and are both
Figure BDA00025040964800001313
The three-phase self-impedance in the III and IV loops and the impedance matrix formed by the inter-phase impedance are the same and are both
Figure BDA00025040964800001314
Figure BDA0002504096480000141
An impedance matrix formed by impedance between the I and II loop lines is represented;
Figure BDA0002504096480000142
representing an impedance matrix formed by impedance between III and IV loop lines;
Figure BDA0002504096480000143
an impedance matrix formed by loop line impedances of I, III (II, IV);
Figure BDA0002504096480000144
and (3) an impedance matrix formed by loop line impedances of I, IV (II, III).
Will Zs1，Zs2，Zp1，Zp2，Zq1，Zq2Substituting into the same tower four loop impedance matrix Z to obtain:
Figure BDA0002504096480000145
step 2, carrying out phase-mode conversion processing on the impedance matrix Z of the line model in the formula (2) to obtain mutually independent current and voltage moduli so as to further research the electrical quantity relation of the line model;
as can be seen from the line model impedance matrix Z in the formula (2), the matrix is a non-diagonal matrix, which indicates that electromagnetic coupling exists between the four lines on the same tower. In order to facilitate the study of the line model, it is necessary to eliminate the mutual inductance influence between the loops, and it is desirable to obtain voltage and current moduli independent of each other.
Firstly, performing phase-to-phase decoupling on the impedance matrix Z of each loop, and obtaining a decoupling matrix through calculation as follows:
Figure BDA0002504096480000151
because two double-circuit lines with the same voltage level exist in the four circuit lines on the same tower, the two circuit lines with the same voltage level are subjected to line-to-line decoupling, and a double-circuit line decoupling matrix P is obtained through derivation1Comprises the following steps:
Figure BDA0002504096480000152
after the two double-circuit lines with the same voltage level are respectively decoupled, a matrix P is utilized1And deriving a matrix suitable for decoupling each loop of the four loops on the same tower:
Figure BDA0002504096480000153
the matrix is transformed as follows:
Z1＝P-1ZP (4)
after matrix transformation, an impedance matrix Z is obtained1Is composed of
Figure BDA0002504096480000161
Wherein: a is11＝Zl1+2Zm1+3Zp1；a12＝Zl1+2Zm1-3Zp1；a21＝Zl2+2Zm2+3Zp2；a22＝Zl2+2Zm2-3Zp2；b1＝Zl1-Zm1；b2＝Zl2-Zm2；
The impedance matrix Z obtained by the transformation of the above equation (5)1It can be seen that the off-diagonal elements of the line moduli 2, 3, 5, 6, 8, 9, 11, 12 are all zero except for the ground moduli 1, 4, 7, 10, indicating that these eight line moduli are completely decoupled from each other and independent of each other. Therefore, the present invention only selects the above eight linear moduli to study, and the ground moduli 1, 4, 7, and 10 will not be further analyzed.
And (3) jointly solving the formula (1) and the formula (4), and deducing the voltage and current moduli as follows:
Figure BDA0002504096480000162
wherein:
Figure BDA0002504096480000163
Figure BDA0002504096480000164
Figure BDA0002504096480000165
Figure BDA0002504096480000171
Figure BDA0002504096480000172
represents 1 obtained after phase-mode conversion2 voltage moduli;
Figure BDA0002504096480000173
representing 12 current moduli obtained after phase-mode conversion;
the other symbols have the same meanings as in formula (1).
Step 3, analyzing the relation between the independent current moduli obtained by the phase-mode transformation, summarizing the internal relation, and laying a foundation for further constructing fault line selection criteria;
the current modulus characteristic after the phase-mode conversion is researched, and the relation rule between the fault component current and the modulus is as follows:
Figure BDA0002504096480000174
the propagation law of each modulus in each phase current is shown in fig. 5:
(1) modulus of current
Figure BDA0002504096480000175
And
Figure BDA0002504096480000176
only spread on three phases of the I loop, when the I loop is in normal operation,
Figure BDA0002504096480000177
therefore, the temperature of the molten metal is controlled,
Figure BDA0002504096480000178
I2and I3Are all close to zero; when the I return line fails, the fault detection circuit detects that the fault occurs,
Figure BDA0002504096480000179
at least one current value being substantially greater than zero, such that the modulus I2And I3At least one value is much greater than zero.
(2) Modulus of current
Figure BDA0002504096480000181
And
Figure BDA0002504096480000182
only spread on three phases of the II loop; when the loop II is in normal operation,
Figure BDA0002504096480000183
then
Figure BDA0002504096480000184
And
Figure BDA0002504096480000185
are all close to zero; when the loop II fails, the fault is detected,
Figure BDA0002504096480000186
at least one current value being much greater than zero, such that the modulus
Figure BDA0002504096480000187
And
Figure BDA0002504096480000188
at least one value is much greater than zero.
(3) Modulus of current
Figure BDA0002504096480000189
And
Figure BDA00025040964800001810
only spread over three phases of the iii loop, when the iii loop is operating normally,
Figure BDA00025040964800001811
then
Figure BDA00025040964800001812
And
Figure BDA00025040964800001813
are all close to zero; when the III loop fails, the fault is detected,
Figure BDA00025040964800001814
at least one current value being much greater than zero, such that the modulus
Figure BDA00025040964800001815
And
Figure BDA00025040964800001816
at least one value is much greater than zero.
(4) Modulus of current
Figure BDA00025040964800001817
And
Figure BDA00025040964800001818
propagating only on three phases of the iv loop. When the IV return wire is in normal operation,
Figure BDA00025040964800001819
then
Figure BDA00025040964800001820
And
Figure BDA00025040964800001821
are all close to zero; when the IV return line fails, the current transformer is connected with the current transformer,
Figure BDA00025040964800001822
at least one current value being much greater than zero, such that the modulus
Figure BDA00025040964800001823
And
Figure BDA00025040964800001824
at least one value is much greater than zero.
And 4, further researching according to the summarized rule, constructing a line selection criterion, and finishing fault judgment.
Definition K1，K2，K3，K4Four parameters:
Figure BDA00025040964800001825
Figure BDA00025040964800001826
Figure BDA00025040964800001827
Figure BDA00025040964800001828
the influence of factors such as mutual inductance between the loops of the same tower four loops, maximum unbalanced current and the like is comprehensively considered, and the setting value of fault line selection is set as a dynamic threshold value.
＝40％×max{K1,K2,K3,K4} (12)
Based on different fault loops, K1，K2，K3，K4The values are different. The proposed fault line selection criterion suitable for the same-tower four-circuit transmission line is as follows:
① when only K is present1Is greater than true, and K2＞、K3＞、K4If no, the current modulus I is indicated2And I3At least one value is far greater than zero, and only the I return line can be judged to have a fault;
② when only K is present2Is greater than true, and K1＞、K3＞、K4If no, the current modulus I is indicated5And I6At least one value is far greater than zero, and only the II return line can be judged to have a fault;
③ when only K is present3Is greater than true, and K1＞、K2＞、K4If no, the current modulus I is indicated8And I9At least one value is far greater than zero, and only the III return line can be judged to have a fault;
④ when only K is present4Is greater than true, and K1＞、K2＞、K3When the two are not satisfied, the modulus current I is indicated11And I12At least one value is far greater than zero, and only the IV loop can be judged to have a fault;
⑤ if K1＞、K2＞、K3＞、K4If more than two conditions are satisfied at the same time, the cross-line fault can be judged to occur;
⑥ if formula K1＞、K2＞、K3＞、K4If not, the same tower four-circuit line can be judged to be in a normal operation state.
Examples
And (3) building a cross-voltage-level same-tower four-circuit transmission line simulation model as shown in fig. 1 through a PSCAD/EMTDC platform, and carrying out simulation analysis on various fault type states. The system parameters are as follows: the voltage grades of the I loop and the II loop are 220kV, the voltage grades of the III loop and the IV loop are 500kV, and the total length of the line is 100 km. The positive sequence impedance of the M-end power supply is j48 omega, and the zero sequence impedance is j96 omega; the positive sequence impedance of the N-end power supply is j16 omega, and the zero sequence impedance is j32 omega; the positive sequence impedance of the P-end power supply is j60 omega, and the zero sequence impedance is j96 omega; the positive sequence impedance of the Q-end power supply is j20 omega, and the zero sequence impedance is j32 omega. The phase change mode of the power transmission line is that the phase change is carried out in each loop, and the phase change is not carried out between different loops. The PSCAD simulation model and the tower structure are shown in the attached figures 6 and 7, wherein C1-C3 are first loop lines; C4-C6 are second return wires; C7-C9 are third return wires; C10-C12 are fourth loops. And the conducting wire of the tower is simulated by using a Chukrar model of the PSCAD.
Specific parameters of unit line impedance are shown in table 1, and the impedance part of the power supply uses a lumped parameter model.
TABLE 1 Cross-voltage class four-circuit line impedance parameter of same tower
Figure BDA0002504096480000201
The total number of the fault types of the four-circuit transmission line on the same tower is more than 8000, and a large number of analysis and calculation are carried out in the text, which is limited to space, and only results of several typical faults are listed. Faults can be categorized into two categories according to the number of return lines in which the fault occurs: single loop fault, cross-line fault, wherein:
the single-loop fault comprises a single-phase earth fault, a two-phase interphase (earth) fault and a three-phase interphase (earth) fault, and the probability of the single-phase earth fault is higher according to the actual probability of the fault, for example, the i loop A phase of the single-phase earth fault is represented by I AG. However, the inter-phase fault causes more damage to the system, and particularly in a high-voltage class system, simulation studies are also performed on fault types such as iab (inter-phase fault occurs in phase a and phase B of loop i), iabg (inter-phase ground fault occurs in phase a and phase B of loop i), and the like.
The cross-line faults mainly comprise double-circuit cross-line faults, three-circuit cross-line faults and four-circuit cross-line faults, and most of the fault types of the four-circuit lines on the same pole are cross-line faults, which account for 80% of all faults, so that simulation research on typical faults such as IA II BCG (phase A, phase B and phase C of a circuit line generate line-to-line ground faults), IB III CG (phase B and phase C of a circuit line generate line-to-line ground faults) and the like is only listed.
In order to study the influence of various factors on the line selection scheme, tables 2 to 3 are partial simulation data when the factors such as transition resistance, fault position and the like of the cross-voltage-level four-circuit line fault line selection of the same tower are respectively changed.
Table 2 shows the simulation results for transition resistances of 0 Ω and 100 Ω, respectively, for various typical types of faults occurring 30km from the M, P end.
TABLE 2 simulation results of faults when transition resistance changes
Figure BDA0002504096480000211
Table 3 shows the simulation results when the fault location is 20km and 60km away from the M, P end, respectively.
TABLE 3 simulation results of faults when the location of the fault changes
Figure BDA0002504096480000212
As can be seen from the simulation results in tables 2 and 3, the line selection scheme can identify the fault line in the case of other types of faults besides the three-phase symmetric fault, and is not affected by the transition resistance and the fault position.
To summarize:
(1) carrying out electrical analysis on the complex cross-voltage-level power transmission line, and providing a new phase-mode transformation matrix to realize the conversion from electromagnetic coupling electrical phasors to independent moduli;
(2) analyzing the relation between the independent current moduli obtained by the phase-mode transformation, summarizing the internal relation, and laying a foundation for further constructing fault line selection criteria;
(3) according to the relation between the independent current moduli, a new fault line selection method is creatively provided.
Through a large number of simulation researches, the obtained line selection scheme can accurately identify single-loop faults, same-name-phase overline faults and non-same-name-phase overline faults and is not influenced by transition resistance, fault positions and the operation mode of a system.
Examples
Correspondingly, the invention also provides a cross-voltage-class same-tower four-circuit line fault line selection device, which is characterized by comprising an impedance matrix acquisition module, a phase-mode conversion module and a fault line selection judgment module, wherein:
the impedance matrix obtaining module is used for obtaining a line model impedance matrix;
the phase-mode transformation module is used for carrying out phase-mode transformation processing on the line model impedance matrix Z to obtain mutually independent current and voltage moduli;
and the fault line selection judgment module is used for analyzing the relation between the independent current moduli to judge fault line selection.
Further, the line model impedance matrix is:
Figure BDA0002504096480000231
wherein, the self-impedance of the I and II return lines is zl1And the mutual impedance between phases is zm1(ii) a The self-impedance of the III and IV loops is zl2And the mutual impedance between phases is zm2(ii) a The mutual impedance between the I and II return lines is zp1(ii) a The mutual impedance between the lines of the III and IV loops is zp2(ii) a The mutual impedance between the I loop, the III loop and the II loop and the IV loop is equal to each other and is zq1(ii) a The mutual impedance between the I loop, the IV loop and the II loop and the III loop is equal to zq2。
Further, in the phase-to-analog conversion module, the performing phase-to-analog conversion processing on the line model impedance matrix Z includes:
because two double-circuit lines with the same voltage level exist in the four circuit lines on the same tower, the two circuit lines with the same voltage level are subjected to line-to-line decoupling, and a double-circuit line decoupling matrix P is obtained through derivation1Comprises the following steps:
Figure BDA0002504096480000232
after the two double-circuit lines with the same voltage level are respectively decoupled, a matrix P is utilized1And deriving a matrix suitable for decoupling each loop of the four loops on the same tower:
Figure BDA0002504096480000241
the matrix is transformed as follows:
Z1＝P-1ZP (4)
after matrix transformation, an impedance matrix Z is obtained1Is composed of
Figure BDA0002504096480000242
Wherein: a is11＝Zl1+2Zm1+3Zp1；a12＝Zl1+2Zm1-3Zp1；a21＝Zl2+2Zm2+3Zp2；a22＝Zl2+2Zm2-3Zp2；b1＝Zl1-Zm1；b2＝Zl2-Zm2；
The impedance matrix Z obtained by the transformation of the above equation (5)1It can be seen that the off-diagonal elements of the line moduli 2, 3, 5, 6, 8, 9, 11, 12 are all zero except for the ground moduli 1, 4, 7, 10, indicating that these eight line moduli are completely decoupled from each other and independent of each other. Therefore, the present invention only selects the above eight linear moduli to study, and the ground moduli 1, 4, 7, and 10 will not be further analyzed.
And (3) jointly solving the formula (1) and the formula (4), and deducing the voltage and current moduli as follows:
Figure BDA0002504096480000243
wherein:
Figure BDA0002504096480000251
Figure BDA0002504096480000252
Figure BDA0002504096480000253
Figure BDA0002504096480000254
Figure BDA0002504096480000255
representing 12 voltage moduli obtained after phase-mode conversion;
Figure BDA0002504096480000256
the 12 current moduli obtained after phase-mode conversion are shown.
Further, in the fault line selection judging module, the analyzing the relationship between the independent current moduli to perform fault line selection judgment includes:
the current modulus characteristic after the phase-mode conversion is researched, and the relation rule between the fault component current and the modulus is as follows:
Figure BDA0002504096480000257
definition K1，K2，K3，K4Four parameters:
Figure BDA0002504096480000261
Figure BDA0002504096480000262
Figure BDA0002504096480000263
Figure BDA0002504096480000264
① when only K is present1Is greater than true, and K2＞、K3＞、K4If no, the current modulus I is indicated2And I3At least one value is far greater than zero, and only the I return line is judged to have a fault;
② when only K is present2Is greater than true, and K1＞、K3＞、K4If no, the current modulus I is indicated5And I6At least one value is far greater than zero, and only the II return line is judged to have a fault;
③ when only K is present3Is greater than true, and K1＞、K2＞、K4If no, the current modulus I is indicated8And I9At least one value is far greater than zero, and only the III return line is judged to have a fault;
④ when only K is present4Is greater than true, and K1＞、K2＞、K3When the two are not satisfied, the modulus current I is indicated11And I12At least one value is far greater than zero, and only the IV loop is judged to have a fault;
⑤ if K1＞、K2＞、K3＞、K4If more than two conditions are satisfied at the same time, judging that the cross-line fault occurs;
⑥ if formula K1＞、K2＞、K3＞、K4If not, judging that the four circuit lines on the same tower are in a normal operation state;
among these, the threshold value is used.
Further, for the dynamic threshold, the calculation formula is:
＝40％×max{K1,K2,K3,K4} (12)。
as will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A cross-voltage-class same-tower four-circuit line fault line selection method is characterized by comprising the following steps:
obtaining a line model impedance matrix;
carrying out phase-mode transformation processing on the line model impedance matrix Z to obtain mutually independent current and voltage moduli;
and analyzing the relation between the independent current moduli to judge fault line selection.
2. The method of claim 1, wherein the line model impedance matrix is:
Figure FDA0002504096470000011
wherein, the self-impedance of the I and II return lines is zl1And the mutual impedance between phases is zm1(ii) a The self-impedance of the III and IV loops is zl2And the mutual impedance between phases is zm2(ii) a The mutual impedance between the I and II return lines is zp1(ii) a The mutual impedance between the lines of the III and IV loops is zp2(ii) a The mutual impedance between the I loop, the III loop and the II loop and the IV loop is equal to each other and is zq1(ii) a The mutual impedance between the I loop, the IV loop and the II loop and the III loop is equal to zq2。
3. The method as claimed in claim 2, wherein the performing of the phase-mode transformation on the line model impedance matrix Z comprises:
because two double-circuit lines with the same voltage level exist in the four circuit lines on the same tower, the two circuit lines with the same voltage level are subjected to line-to-line decoupling, and a double-circuit line decoupling matrix P is obtained through derivation1Comprises the following steps:
Figure FDA0002504096470000021
after the two double-circuit lines with the same voltage level are respectively decoupled, a matrix P is utilized1And deriving a matrix suitable for decoupling each loop of the four loops on the same tower:
Figure FDA0002504096470000022
the matrix is transformed as follows:
Z1＝P-1ZP (4)
after matrix transformation, an impedance matrix Z is obtained1Is composed of
Figure FDA0002504096470000023
Wherein: a is11＝Zl1+2Zm1+3Zp1；a12＝Zl1+2Zm1-3Zp1；a21＝Zl2+2Zm2+3Zp2；a22＝Zl2+2Zm2-3Zp2；b1＝Zl1-Zm1；b2＝Zl2-Zm2；
The impedance matrix Z obtained by the transformation of the above equation (5)1It can be seen that the off-diagonal elements of the line moduli 2, 3, 5, 6, 8, 9, 11, 12 are all zero except for the ground moduli 1, 4, 7, 10, indicating that these eight line moduli are completely decoupled from each other and independent of each other;
and (3) jointly solving the formula (1) and the formula (4), and deducing the voltage and current moduli as follows:
Figure FDA0002504096470000031
wherein:
Figure FDA0002504096470000032
Figure FDA0002504096470000033
Figure FDA0002504096470000034
Figure FDA0002504096470000035
Figure FDA0002504096470000036
representing 12 voltage moduli obtained after phase-mode conversion;
Figure FDA0002504096470000037
the 12 current moduli obtained after phase-mode conversion are shown.
4. The method as claimed in claim 3, wherein the analyzing the relationship between the independent current moduli for fault line selection judgment comprises:
the current modulus characteristic after the phase-mode conversion is researched, and the relation rule between the fault component current and the modulus is as follows:
Figure FDA0002504096470000041
definition K1，K2，K3，K4Four parameters:
Figure FDA0002504096470000042
Figure FDA0002504096470000043
Figure FDA0002504096470000044
Figure FDA0002504096470000045
① when only K is present1Is greater than true, and K2＞、K3＞、K4If no, the current modulus I is indicated2And I3At least one value is far greater than zero, and only the I return line is judged to have a fault;
② when only K is present2Is greater than true, and K1＞、K3＞、K4If no, the current modulus I is indicated5And I6At least one value is far greater than zero, and only the II return line is judged to have a fault;
③ when only K is present3Is greater than true, and K1＞、K2＞、K4If no, the current modulus I is indicated8And I9At least one value is far greater than zero, and only the III return line is judged to have a fault;
④ when only K is present4Is greater than true, and K1＞、K2＞、K3When the two are not satisfied, the modulus current I is indicated11And I12At least one value is far greater than zero, and only the IV loop is judged to have a fault;
⑤ if K1＞、K2＞、K3＞、K4If more than two conditions are satisfied at the same time, judging that the cross-line fault occurs;
⑥ if formula K1＞、K2＞、K3＞、K4If not, judging that the four circuit lines on the same tower are in a normal operation state;
among these, the threshold value is used.
5. The method of claim 4, wherein the calculation formula for the dynamic threshold is as follows:
＝40％×max{K1,K2,K3,K4} (12)。
6. the utility model provides a cross voltage level four return line fault line selection devices on same tower which characterized by includes impedance matrix acquisition module, looks mode conversion module and fault line selection judgement module, wherein:
the impedance matrix obtaining module is used for obtaining a line model impedance matrix;
the phase-mode transformation module is used for carrying out phase-mode transformation processing on the line model impedance matrix Z to obtain mutually independent current and voltage moduli;
and the fault line selection judgment module is used for analyzing the relation between the independent current moduli to judge fault line selection.
7. The device of claim 6, wherein the line model impedance matrix is:
Figure FDA0002504096470000061
wherein, the self-impedance of the I and II return lines is zl1And the mutual impedance between phases is zm1(ii) a The self-impedance of the III and IV loops is zl2And the mutual impedance between phases is zm2(ii) a The mutual impedance between the I and II return lines is zp1(ii) a The mutual impedance between the lines of the III and IV loops is zp2(ii) a The mutual impedance between the I loop, the III loop and the II loop and the IV loop is equal to each other and is zq1(ii) a The mutual impedance between the I loop, the IV loop and the II loop and the III loop is equal to zq2。
8. The device of claim 7, wherein in the phase-to-analog conversion module, the phase-to-analog conversion processing is performed on the line model impedance matrix Z, and the processing comprises:
because two double-circuit lines with the same voltage level exist in the four circuit lines on the same tower, the two circuit lines with the same voltage level are subjected to line-to-line decoupling, and a double-circuit line decoupling matrix P is obtained through derivation1Comprises the following steps:
Figure FDA0002504096470000062
after the two double-circuit lines with the same voltage level are respectively decoupled, a matrix P is utilized1And deriving a matrix suitable for decoupling each loop of the four loops on the same tower:
Figure FDA0002504096470000071
the matrix is transformed as follows:
Z1＝P-1ZP (4)
after matrix transformation, an impedance matrix Z is obtained1Is composed of
Figure FDA0002504096470000072
Wherein: a is11＝Zl1+2Zm1+3Zp1；a12＝Zl1+2Zm1-3Zp1；a21＝Zl2+2Zm2+3Zp2；a22＝Zl2+2Zm2-3Zp2；b1＝Zl1-Zm1；b2＝Zl2-Zm2；
The impedance matrix Z obtained by the transformation of the above equation (5)1It can be seen that the off-diagonal elements of the line moduli 2, 3, 5, 6, 8, 9, 11, 12 are all zero except for the ground moduli 1, 4, 7, 10, indicating that these eight line moduli are completely decoupled from each other and independent of each other;
and (3) jointly solving the formula (1) and the formula (4), and deducing the voltage and current moduli as follows:
Figure FDA0002504096470000073
wherein:
Figure FDA0002504096470000081
Figure FDA0002504096470000082
Figure FDA0002504096470000083
Figure FDA0002504096470000084
Figure FDA0002504096470000085
representing 12 voltage moduli obtained after phase-mode conversion;
Figure FDA0002504096470000086
the 12 current moduli obtained after phase-mode conversion are shown.
9. The device of claim 8, wherein in the fault line selection determining module, the analyzing the relationship between the independent current moduli to determine the fault line selection comprises:
the current modulus characteristic after the phase-mode conversion is researched, and the relation rule between the fault component current and the modulus is as follows:
Figure FDA0002504096470000087
definition K1，K2，K3，K4Four parameters:
Figure FDA0002504096470000091
Figure FDA0002504096470000092
Figure FDA0002504096470000093
Figure FDA0002504096470000094
① when only K is present1Is greater than true, and K2＞、K3＞、K4If no, the current modulus I is indicated2And I3At least one value is far greater than zero, and only the I return line is judged to have a fault;
② when only K is present2Is greater than true, and K1＞、K3＞、K4If no, the current modulus I is indicated5And I6At least one value is far greater than zero, and only the II return line is judged to have a fault;
③ when only K is present3Is greater than true, and K1＞、K2＞、K4If no, the current modulus I is indicated8And I9At least one value is far greater than zero, and only the III return line is judged to have a fault;
④ when only K is present4Is greater than true, and K1＞、K2＞、K3When the two are not satisfied, the modulus current I is indicated11And I12At least one value is far greater than zero, and only the IV loop is judged to have a fault;
⑤ if K1＞、K2＞、K3＞、K4If more than two conditions are satisfied at the same time, judging that the cross-line fault occurs;
⑥ if formula K1＞、K2＞、K3＞、K4If not, judging that the four circuit lines on the same tower are in a normal operation state;
among these, the threshold value is used.
10. The device of claim 9, wherein the dynamic threshold is calculated by the following formula:
＝40％×max{K1,K2,K3,K4} (12)。
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