JP2001099883A - Method for locating fault on transmission line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance location accuracy of a fault section or fault point on a transmission line. SOLUTION: A fault section or fault point on a transmission line is located by formulating a transmission circuit according to Kirchhoff's first and second laws using the telemetric data of a generator and a load in order to grasp the system state prevailing before fault, adding the formula of measurements of means for detection the current and voltage of the transmission line at the time of fault, decreasing the number of variables by specifying a sound line through matrix operation and then solving simultaneous equations including the fault current and the fault point as variables.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention specifies an accident section and an accident point when an accident occurs in a transmission line due to various causes such as wind and rain, ice and snow, lightning, contact with trees and flying objects, and bird and animal damage. The present invention relates to a method for locating a fault on a transmission line.

[0002]

2. Description of the Related Art Conventionally, as a method of locating a fault in a transmission line, an impedance type based on Kirchhoff's second law has been mainly used, but a matrix in which Kirchhoff's first and second laws are applied to a power transmission circuit. Some arithmetic forms have been put to practical use. The latter method captures as much information as possible about the accident, formulates it using Kirchhoff's law, derives the equation for the electric wire circuit and the equation at the point of the accident, and solves this using the Newton-Raphson method. It is considered that the orientation accuracy is higher than the former method when the number of accident lines is large.

[0003]

However, in the above-mentioned conventional configuration, the location accuracy of the accident section and the location of the accident is not always sufficient, and it has been desired to further improve the location accuracy. The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the location accuracy of an accident section and an accident point.

[0004]

According to the first aspect of the present invention, a power transmission circuit is configured by Kirchhoff's first system using a generator and telemeter information of the load in order to grasp a system state before an accident. And formulas of the measured values of the voltage detection means and the current detection means at the time of an accident are added to the formula, and the variables are reduced by specifying a healthy line by a matrix operation. This makes it possible to exclude variables relating to a healthy line in which no accident has occurred from the simultaneous equations, thereby increasing the redundancy of the simultaneous equations and increasing the amount of information available for the number of variables. Also, by increasing the redundancy in this way, it is possible to suppress elements including errors. As a result, it was possible to improve the accuracy of locating the faulty section and the faulty point of the transmission line.

[0005] Further, by providing the configuration according to the second aspect, the behavior of the voltage / current non-measurement end during an accident is obtained from the telemeter information of the generator and the load before the accident and the power flow calculation result. Circuit, applying Kirchhoff's first law to each node of the power transmission circuit, the generator was simulated with a series circuit of a three-phase power supply and reactance with constant internal induced voltage, and the load The power transmission circuit is formulated by simulating the load with a constant current characteristic that does not change. That is, in formulating the power transmission circuit, as described above, by applying Kirchhoff's first law by simulating the generator and load connected to the transmission line, it is not always necessary to connect the generator and load at the connection point. Without directly measuring the current and voltage, the accident section and the accident point can be specified, and the installation load of the device can be reduced.

Further, by providing the configuration of the third aspect, each transmission line is simulated with a mutual impedance proportional to the length of the line and a ground capacitance simulated with a π-type circuit, whereby Formulate. by this,
A simple and accurate formulation of the transmission line is possible.

In addition, by providing the configuration according to the fourth aspect, the circuit equations of the sections between the connection points of the transmission line are connected by Kirchhoff's first law, and the circuit equations of the voltage detection means and the current detection means are connected to this. A measurement formula is added to create a matrix operation formula in which the left side is a variable matrix and the right side is a constant matrix, and the left side variable matrix is used in at least later processing by defining a new variable. For the components, the power transmission circuit is formulated by transforming the components into a linear matrix consisting only of constants. Therefore, by creating a matrix by separating the variable part and the constant part, the subsequent matrix operation can be easily performed.

Further, by providing the configuration according to claim 5, the fault point current _if
Is formulated in advance so as to be a matrix having only the variables k and _if as constants. In the event of an accident, a constant vector is obtained by calculating the measured values of the voltage detecting means and the current detecting means and the constant matrix on the right side. And solve the resulting complex system of equations. In other words, what can be processed before the accident is processed in advance, the processing required to identify the accident section and the accident point when the accident occurs can be reduced, and the accident section and the accident point can be quickly identified. Can be.

With the configuration according to the sixth aspect of the present invention, in the matrix in which only the fault point currents _if and k · _if are used as variables, it is assumed that the fault has occurred at the center of the section. determined point current i _f, is less than the set value for identifying whether healthy line, in a matrix that only the variable by determining the line between healthy line the fault point current i _f and k · i _f Fault point current _if of the relevant line
_Let i _f = 0, and thus k · i _f = 0, solve the resulting complex system of equations. That is, the fault point current flowing when it is assumed that an accident has occurred on a certain line is determined, and whether the line is a sound line depends on whether the obtained fault point current value is appropriate as the fault point current. Therefore, it can be easily and easily determined whether or not the line is sound. Approximately 95% of transmission line accidents are accidents involving three or less lines. Therefore, by determining a healthy line as described above, the number of variables can be greatly reduced. Accident sections and accident points can be specified with high accuracy. Further, a solution can be obtained with high accuracy even in the case of a small ground fault where the fault point current is small.

Further, with the configuration according to the seventh aspect, in the matrix having only the fault point currents _if and k · _if as variables, the number of equations of the complex simultaneous equations is larger than the number of variables. Is satisfied, the relative position k is obtained by directly solving a matrix having only the fault point currents _if and k · _if as variables by diagonalization of the matrix, and the number of the equations is smaller than the number of variables. If, the relative position k is obtained by the Newton-Raphson method.
In other words, if there is room for the number of equations in the complex system of equations, directly solve the equation to obtain an accurate solution with simple processing, and if there is no room, use the Newton-Raphson method to calculate the accuracy as much as possible. The aim is to improve the localization accuracy of the accident section and the accident point as much as possible according to the situation.

In addition, by providing the configuration according to claim 8, the relative position k of the accident point is obtained for each section between the connection points of the transmission line, and the obtained value is set in a range of 0 to 1.0. At some point, the section is identified as an accident section. Therefore,
By calculating the relative position k of the accident point for each section between the transmission line connection points, the accident section can be accurately specified.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a three-terminal system configuration of a three-phase AC two-circuit transmission line will be described. Hereinafter, the basic concept of the equivalent circuit will be sequentially described. 1. Basic formula for fault location The basic theory of fault location is to formulate the accident phenomenon using Kirchhoff's first and second laws, and to calculate the location of the fault and the resistance at the fault from this nonlinear equation. In order to make this theory applicable to a wide range of fields, we have made some efforts to express and solve the matrix.

A description will now be given of a three-terminal system configuration of the three-phase AC two-circuit transmission line shown in FIG. A section from a connection point of a transmission line to a connection point is called a section, and FIG. 1 is assumed to be configured with three sections. When an accident such as a short circuit or ground fault occurs over the length of the transmission line, the accident section and accident point are calculated. The generator and load are connected to the bus of the substation, but not to the branch point of the transmission line. In this example, bus 1 of section 1
PT as voltage detection means
(Transformer) and CT (current transformer) as current detecting means. Remote generator output metering device WG,
The measurement information of the substation load weighing device WL is input to the arithmetic processing device by a telemeter. In this fault location theory,
Simultaneous accidents at multiple points are not taken into account (both ends can be solved, but multiple point accidents are very few), and one point in any section is used. If an accident occurs near the branch point, it may not be possible to determine the accident section. Therefore, it is assumed that there is an accident in each section, and the position of the accident point is determined.

1.1 Kirchhoff's Equation in Accident Section FIG. 2 shows one section for each phase. Since an accident occurs over Line 1 1L and Line 2 2L, the phase is set to No. 1 to No. 6 is displayed. The suffixes S and R are attached to the voltage and current of the transmission / reception terminal of the transmission line. k is the distance to the accident point and is shown as a relative position by the ratio of the total length being 1;
It is. In the expansion of the following expression, convert the vector to lowercase bold (2
In the case of a circuit transmission line, a 6th-order vector) and a matrix are represented by bold capital letters (6x6th, 3x3rd order). However, in the text of the specification text and a part of the formulas, even vectors or matrices are represented by ordinary characters for convenience of description. h _S is S side phase currents of the fault point, h _R is R-side phase currents of the fault point, v _f is the phase voltage of the fault point, i _f the phase currents of the fault point, r (1) ~r (6) the respective phases of the fault point resistance, i _t is the tower foot current, u _t the potential of the steel tower, z _t is the tower foot impedance, Z is the mutual impedance of the transmission line, y is the earth capacitance of each line . Formulating the relationship between the voltage and current in the fault section based on these specifications gives (1) to (8). Wherein each variable v, i, h, in the u _t is a complex number, k, r
Is a real number.

(Equation 1) When the expressions (1) to (6) are expressed in a matrix with common variables, the expression (9) is obtained.

(Equation 2) A new variable k · _if is set as a variable so as not to put a variable in an element of the matrix relating to i _S and i _R.
Formula (9) is further diagonalized to formula (10).

(Equation 3) In equation (10), the current at both ends of the transmission line is the voltage at both ends v _S , v _R
It can be seen that this can be expressed as a function of the fault point current _if . F
_4, later using an expression portion of F ₅ as an expression for fault section.

1.2 Simulating the generator and load In the case of the two-end measurement method, i _S , i _R , v _S , v
_{Although R} is known and simultaneous equations can be solved, it is necessary to further increase the equation in the case of single-ended measurement. The generator and load are formulated in an equivalent circuit using the telemeter values or estimated values before the accident, and Kirchhoff's first law is applied to each node.

[0016] (1) pre-load flow diagram 1 the generator output and the load values respectively W _G, given by W _L, when the voltage of the measuring end, current is applied, the node voltage of the remote terminal power flow Can be obtained by Moreover, finding the voltage and W _G, from W _L, an equivalent circuit of the load and generator as follows.

(2) Equivalent Circuit of Generator The generator is connected to a three-phase symmetric internal induced voltage e as shown in FIG.
_When expressed by _G and the series impedance z _G , the relationship between the generator terminal voltage v _G and the phase current i _G is as shown in Expression (11).

(Equation 4)The internal induced voltage e in equation (11)_GAnd impedance z_GIs
Set to satisfy the following two points.・ The generator output before the accident is W_GThat.・ The fault current in the near-end accident of the generator
Actance (x_d'').
Generally, the terminal voltage before the accident is_GOThen the internal induced voltage e
_GOIs e_GO= V_GO+ Jx_d'' ・ (W_G ^*/ V_GO ^*) (12) where * represents conjugate. The next transient reactance of the generator is
Y = 1 / jx because it is not related to the driving condition_d'' i_G= Y_Ge_GO-Y_Gv_G= I_GO-Y_Gv_G ………… (13) Incorporate the second term in equation (13) into a constant matrix
Can be. The first term is a fixed component determined by the generator output
Set in advance. In the expansion of the following equation, i_GOTo i _GRead
Express it instead.

(3) Equivalent Circuit of Load The load voltage characteristics are generally classified into constant impedance characteristics, constant current characteristics, and constant power characteristics. According to the results of a nationwide survey, it is known that the ratio of the constant power characteristic of 60% and the constant impedance characteristic of 40% is close to the actual measurement, and here the constant current characteristic is adopted. Assuming that the load before the accident is W _L and the voltage is v _LO , the load current i _L is represented by i _L = (W _L / v _LO ) ^* (14)

1.3 Integration of Each Section Matrix The matrix is integrated using the three-terminal transmission line of FIG. 1 as an example.
Formulate the relationship between voltage and current for the entire system. (B) the F ₄ and F ₅ of the second law (10) of the Kirchhoff is applied to each section (1
5) This is the F- _2nd part of the equation. (B) Kirchhoff's first law Except for node 1 which is the measuring end, applying Kirchhoff's first law to the other nodes gives the formula of F- _1st . I _G and i _L on the right side are obtained from the equations in the previous section, and are variable portions that change depending on the operation state. (C) Voltage equation The transmission line is connected at the branch point of the transmission line or the bus at the substation. On the other hand, in this case, the voltage between both ends of the transmission line is treated as an individual variable for each section, so an equation for section connection is required.
That is the F- _VEQ part of equation (15). (D) Formulas of PT and CT measurement values In FIG. 1, the voltage of the bus is measured by PT, and the current of the transmission line is measured by CT. The accident situation is specified based on the measured values.

(Equation 5) (15) portion of the formula F _PCT it, one end, the both ends measured to correspond with the measured value variable. Right side of the constant matrices are pre-calculated for each transmission line to be applied, the column vector b _W Substituting the measured value. b _W = _{[i G, i L, v PT} , i CT1, i CT2 ] ^T ............ (16)

1.4 Diagonalization of Integrated Matrix When equation (15) is diagonalized, equation (17) is obtained. Finally, it is desired to obtain the position k of the fault point and the fault point resistances r _{1 to} r _6. The procedure for reducing the state variables and making the equation compact will be described sequentially. Although the matrix D _f representing the fault point current i _F in the equation (17) is calculated once by diagonalization in the equation (15), one target is selected according to a virtual fault section.

(Equation 6) (17) D _f , D which newly defines the off-diagonalized row equation
_When expressed in a _B matrix, the expression (18) is obtained.

(Equation 7) 1.5 Creation of simultaneous equations Although the basic equations related to fault location have been reduced,
What remains is a compact (18) showing the relationship between k and _if.
It became an expression. (18) When the variables of the equation and the number of the equations are shown in the example of FIG. 1, regarding the number of the variables, the complex number _if is 6 and the real number k is 1, which is a total of 13; about,
There are a total of twelve complex number equations. Therefore, (18)
K cannot be determined only by the equation.

2. Solution of simultaneous equations Equation (18) contains all information on the system state before the accident and the measuring end during the accident, and solves the simultaneous equations to find the position k of the accident point. 2.1 Both-ends measurement method In the two-ends measurement method in which measurement information of the transformer PT and the like can be obtained at a plurality of connection points, solve k from equation (18) when the number of equations has a margin compared to the number of variables. Is easy. (1
Equation (8) is unitized, and as shown in equation (19), k · _if and _if are represented by constants on the right side, and k is obtained from the ratio. In addition, right side D _B
Is preset in a fixed matrix, and a column vector b _k is calculated by an operation with input data at the time of an accident. That is,

(Equation 8) k _(i) = (k · _{if (i)} ) / _{if (i)} = b _{k (1 + 6)} / b _{k (i)} k is obtained for each line, and the average value k _av of the accident point is calculated. Position.

(Equation 9) 2.2 Df at one end measuring system (1) solution (18) is, D _K as the matrix after diagonalized the left half in the matrix with the degree of (6 × 12) (20), _DBK . _{1 · i f + kD K i} f = D BK · b W ............... (20) (( in 20), "1" indicates a unit matrix) further when the right-hand side constant term and b _K (21) An expression is obtained.

(Equation 10) Here, assuming that the accident point is at the center of the section, that is, _if = (1 + kD _K ) ⁻¹ b _k (22), the accident point current _{if is obtained by} setting k = 0.5.
The value of _if obtained in this way is equal to a set threshold value (for example,
For less wire than 1/2) of the maximum value of i _f, it is determined that the sound line fault has not occurred to the line, the line (n) regarding i _{f (n)} and k · i f _{(n )} Is deleted from the variable.

(1-1) When the difference between the number of complex simultaneous equations and the number of variables is large. For example, if lines # 4 to # 6 are sound lines, equation (21) becomes equation (23). Becomes

[Equation 11] The diagonalization of the k · _if portion on the left side gives equation (24). At this time, the right side constant vector b _Ku is given by _if and k · _if
And k of the #n line is obtained from the equation (25). k _(n) = k · _{if (n)} / _{if (n)} = b _{Ku (n)} / b _{Ku (n + 3)} (25) When k _(n) obtained in this way is 0 to When it is in the range of 1.0, the section is specified as an accident section. Further, the average value k _av of k is obtained from equation (26). k _av = (1/3) Note .SIGMA.k _(n) ............... (26), when the number of accidents ruling is small (23) of the variable is less than 6, the sequence of elements of k · i _f A row having a large value is selected, the number of formulas is made equal to the number of variables, and diagonalization is performed to improve the k _(n) orientation accuracy.

(1-2) The number and variation of complex simultaneous equations
When the difference from the number is small, the number of lines that can be
When the difference between the number of expressions and the number of variables is small, Newton
Find relative position k by repeated calculation of Rafson method
You. More specifically, it cannot be determined that the line is healthy, and an accident occurs.
I for each of the lines that may be_fAnd ki_fWhen
Are independent variables, and each expression is k, i _{f (n)}About
Apply the Newton-Raphson method in the form of partial differentiation
The amount of correction Δk of k is smaller than the allowable value by iterative calculation
When it becomes, the calculation is terminated and k is obtained. Like that
When k obtained in the above is in the range of 0 to 1.0, the section is
Identify the accident section. (1-3) When the Number of Healthy Lines is Zero In this case, as described above, the solution is obtained only by Expression (18).
It is not possible to add
Solve. Specifically, the formula of the accident point branch,
Tower leg current i at the fault point from the CT measurement value at the end_tTo

(Equation 12) And by substituting into equation (7), the equation can be added. In this equation, Y _SUM is the total value of the ground charge capacity viewed from the CT installation point. Thereafter, the simultaneous equations are calculated by the Newton-Raphson method repeatedly to calculate the relative position k.
Ask for. When k thus obtained is in the range of 0 to 1.0, the section is specified as an accident section.

(2) Orientation Accuracy The accuracy of the solution by the equations (23) to (26) is the
From solving Newton-Raphson method for simultaneous equations
The two-terminal two-circuit transmission line shown in Fig. 2
An example is described. Constant current load i at the non-measurement end_LIs connected
And the left side D _K, Right side D_BKThe matrix is (27)
It can be represented by an equation.

(Equation 13) In this equation, D is defined by the following equation. Assuming that the mutual impedance between the six lines in the two-line transmission line is Z, Z ⁻¹ is divided into four to be A _{1 to} A ₄ .

[Equation 14] Here, D≡A ₁₂ ⁻¹ (A ₁ + A ₂ + A ₃ + A ₄ ) is defined as (29). Normally, the transmission lines are symmetrically arranged at Line 1 and Line 2, and A ₁ = A ₄ , A ₂ = A ₃ , A ₁₂ = A ₃₄ (30) is established. Since there is a relationship of Expression (30), D in Expression (29) is a unit matrix as in Expression (31). D = A ₁₂ ⁻¹ (2A ₁₂ ) = 2.1 (31) (“1” on the right-hand side of the equation (31) is a unit matrix) 27) Substituting equation (32)
An expression is obtained.

(Equation 15) When the # 4 to # 6 lines are sound lines as in the example of Expression (23), k _(n) = (k · _{if (n)} ) / for the accident lines (n) of # 1 to # 3. _{if (n)} = ( _{2iCT2 (n)} -iL _(n) ) / ( _{iCT1 (n)} + _{iCT2 (n)} -iL _(n) ) (33) K) is obtained from the equation. It can be seen that equation (33) is not affected by the mutual impedance Z of the transmission line. That is, if there is at least one healthy line in each of the A phase, the B phase, and the C phase, k is determined from the equation (33), and is not affected by the mutual impedance of the transmission line. When the equations (32) are summed and the zero-phase CT currents are I ₀₁ and I ₀₂ , the equation (34) is obtained. k = 2I ₀₂ / (I ₀₁ + I ₀₂ ) (34) where

(Equation 16) Thus, a simple equation that is not affected by the load current i _L is obtained. That is, in the case of a one-line ground fault (1φG), the load current is not affected. In general, since the mutual impedance Z and the load current i _L of the transmission line are not always easy to specify accurately and cause an error, as described above, the relative position k of the accident point can be specified without being affected by them. It can be seen that the positioning accuracy of the relative position k is high.

3. Example of simulation calculation A program was created to verify the practicality of the solution described above, and a 154 kV two-circuit two-terminal transmission line (101.5 k
A simulation was calculated for m). A 240 MW generator and a 300 A NGR (transformer neutral point grounding resistor) were connected to the receiving end, and the fault current was determined by EMTP, a general-purpose circuit analysis program. Table 1 shows the simulation results.

[Table 1] In Table 1, "conventional type" is indicated by the conventional Newton-Raphson method, where k = 0.
5, For one-line ground fault (1φG) with Rf = 500Ω,
The orientation error was 20.6%, which was poor for practical use.
On the other hand, when the present invention shown as "new type" in Table 1 is applied, the accuracy is increased by an order of magnitude to -2.6%. This tendency is the same for 2φG (two-line ground fault) and 3φG (three-line ground fault). The ground fault of 500Ω is Vo of about 30% at 154 kV, and it can be seen that the sensitivity is very high when the present invention is applied.

4. Failure Point Locating Apparatus By causing the processing unit OP shown in FIG. 1 to execute the processing of the transmission line failure point locating method described above, a transmission line failure point locating apparatus can be configured. Formulation of the power transmission circuit is performed such that the relative position of the fault point is k, and the fault point current _if and only k · _if are variables, and the matrix of the above formula (20) or (21) is obtained. It is stored in advance in a storage means such as a memory provided in the arithmetic processing unit OP, and in the event of an accident, a constant vector is created from an operation of the PT measurement value and the CT measurement value with the constant matrix on the right-hand side. By solving the complex simultaneous equations, an accident section and an accident point are specified. The process of solving the complex system of equations is as described in equation (22) and thereafter.

[Other Embodiments] Hereinafter, other embodiments of the present invention will be listed. In the above embodiment, the case where the present invention is applied to a three-terminal system configuration of a three-phase AC two-circuit transmission line is illustrated.
Obviously, it can be applied to various other system configurations. In the above embodiment, k =
Although 0.5 is substituted into Expression (22), the value of k at this time may be a value around 0.5.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a power system according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit of an accident section of a two-circuit transmission line according to an embodiment of the present invention.

FIG. 3 is an equivalent circuit of the generator according to the embodiment of the present invention.

[Explanation of symbols]

CT Current detecting means _if Current of fault point k Relative position of fault point PT Voltage detecting means y _i Capacitance to ground Z Mutual impedance

Claims (8)

[Claims] 1. A power transmission circuit is formulated by Kirchhoff's first and second laws using a generator and telemeter information of the load in order to grasp the state of the system before the accident. The equations of the measured values of the current detection means and the voltage detection means are added, the variables are reduced by specifying a healthy line by a matrix operation, and the fault section and the fault section are solved by solving a simultaneous equation using the fault point current and the fault point as variables. A method for locating a fault on a transmission line to identify the location of an accident. 2. The behavior of a voltage / current non-measurement end during an accident is simulated by an equivalent circuit obtained from telemeter information of the generator and the load before the accident and a power flow calculation result, and is applied to each node of the power transmission circuit. Applying Kirchhoff's first law, the generator is simulated by a series circuit of a three-phase power supply and a reactance in which the internally induced voltage is constant, and the load is simulated by a constant current characteristic load whose current does not change during an accident. The method of claim 1, wherein the power transmission circuit is formulated. 3. The transmission system according to claim 1, wherein each power transmission line is formulated by simulating each transmission line with a mutual impedance proportional to the line length and a ground capacitance simulated by a π-type circuit. Fault location method for electric wires. 4. A circuit equation of each section between connection points of a transmission line is connected according to Kirchhoff's first law, and the equations of the measured values of the voltage detecting means and the current detecting means are added thereto. Create a matrix operation expression with a matrix and the right side as a constant matrix, and define a new variable for the variable matrix on the left side, and at least components used only in later processing are linear matrices whose elements are only constants. The transmission line fault locating method according to any one of claims 1 to 3, wherein the power transmission circuit is formulated by deforming the power transmission circuit into a fault. 5. The power transmission circuit is preliminarily formulated so as to form a matrix having only the fault point current _if and k · _if as variables, with the relative position of the fault point as k. Create a constant vector from the calculation of the measured value of the current detection means and the constant matrix on the right side,
5. The method according to claim 4, wherein the fault section and the fault point are specified by solving a complex simultaneous equation obtained by the calculation. 6. In a matrix using only the fault point currents _if and k · _if as variables, the fault point current _if is determined assuming that an accident has occurred at the center of the section, and whether or not the fault line is sound is determined. If less than the set value for identifying the fault point current i _f of the line corresponding in matrix that only the variable by determining the line between healthy line the fault point current i _f and k · i _f i _f 6. The fault locating method for a transmission line according to claim 5, wherein the fault section and the fault point are specified by solving complex simultaneous equations obtained by setting = 0. 7. In a matrix having only the fault point currents _if and k · _if as variables, when the number of equations of the complex simultaneous equations is larger than the number of variables, the fault point currents _if and The relative position k is obtained by directly solving a matrix having only k · _if as a variable by diagonalization of the matrix. When the number of the equations is smaller than the number of variables, the relative position k is calculated by the Newton-Raphson method. 7. The method according to claim 5, wherein the position k is determined. 8. A relative position k of an accident point is calculated for each section between connection points of transmission lines, and when the calculated value is in a range of 0 to 1.0, the section is identified as an accident section. The fault locating method for a transmission line according to claim 1.