JPH0798352A - Fault zone selecting method - Google Patents

Abstract

PURPOSE:To correctly select a fault zone when a simple fault occurs by obtaining the difference or the like of the voltage at the branch point of a multi-terminal single-circuit power transmission line. CONSTITUTION:The voltage Vb2,1 at the branch point b2 at either terminal of an (n)-terminal single-circuit power transmission line is calculated from a terminal T1. The voltage Vb2,2 at the branch point b2 is calculated from a terminal T2, and the difference DELTA1,2 between the voltage Vb2,1 and the voltage Vb2,2 is obtained. The voltage Vbn-1,n-1 at the branch point bn-1 is calculated from a terminal Tn, and the difference DELTAn-1 with the voltage Vbn-1,n-1 is obtained. If difference DELTA1,2 difference DELTAn-1, it is judged that no fault exists in zones bn-T1, b2-T2. The (n)-terminal single-circuit power transmission line is converted into an (n-1)-terminal single-circuit system. These procedures are repeated to finally convert it into a three-terminal single-circuit containing a fault zone, and a two-terminal single-circuit containing a fault zone is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a failure section when a failure occurs at one point of an n (n ≧ 3) terminal single-line power transmission line,
It relates to a method of selecting based on the voltage and current measured at each terminal. Here, the "fault" may be either a short circuit or a ground fault, and the line related to the fault is 1
It may be one of lines, two lines, three lines, or a combination thereof. The “single-line power transmission line” may be set as a single line from the beginning, or one of the parallel two-line power transmission lines may be out of order and may be operated as a single line.

[0002]

2. Description of the Related Art When a failure occurs in a power system, it is an important task from the viewpoint of preventing the spread of failure to find the failure point and make necessary repairs. In a transmission line without a fault locator (also called a fault locator) installed,
Since a line inspection is required to search for a failure point, a great deal of labor and cost will be spent. This is especially the case for long-distance power lines and those with complex terrain.

For this reason, a fault point locating device has been installed for some time. As a fault location method, conventionally,
A surge reception method that detects the surge voltage generated at the fault point at both ends of the transmission line and determines the fault point from the difference in the arrival time at both ends of the surge, or sends a pulse to the transmission line when the fault occurs and measures the reflection time of the pulse Therefore, a pulse radar system that determines the failure point has been adopted.

These systems have considerably high orientation accuracy if the generated surge or reflected pulse can be received correctly. However, if the line has a branch or the line impedance changes, a large orientation error occurs due to reflection or the like. It also has the drawback that it cannot be orientated.
On the other hand, recently, a fault locator using a digital relay technology based on a microcomputer and having a principle different from the above method has been developed.

This fault point locator focuses on the distance measuring ability of a distance relay, which is a protection relay for a power transmission line, and uses an AC input such as an instrument transformer (PT) and a current transformer (CT). The failure point is located by applying a predetermined arithmetic expression.

[0006]

A failure point locating device to which this microcomputer is applied is such that the voltage at the device installation point
This is a method of performing the orientation calculation based only on the current, and in a multi-terminal single-line power transmission line having many branches, there is a drawback that the fault section cannot be correctly selected for a fault exceeding the branch point.

Therefore, the present invention provides a simple fault in a fault point locating device for locating a fault point based on the voltage and current by installing PT or CT at each terminal of a general n-terminal single-line power transmission line. It is an object of the present invention to provide a failure section selection method that can correctly select a failure section when an error occurs.

[0008]

According to the method of the present invention, for a branch point at either end of a series of branch points of an n-terminal single-line transmission line, two terminals connected to the branch point are connected to the branch point. The voltage at the branch point is calculated in consideration of the voltage drop in the section up to the branch point, the absolute value of the difference between the calculated two voltages at the branch point is calculated, and the same applies to the branch point at the other end. The absolute value of the calculated difference between the two voltages at the branch point is calculated, the absolute values of the differences calculated in the procedure are compared, and the branch point corresponding to the smaller difference is It is determined that there is no failure in the section from the two terminals connected to the branch point to the branch point, and the branch point is defined as a terminal having the sum of the voltage and the current of the two terminals connected to the branch point (n -1) Convert the terminal to a single line system, and -1) for terminal single line transmission line,
By repeating the above procedure, conversion to a 3-terminal single-line power transmission line is performed, and the branch in consideration of the voltage drop in the section from the 3-terminal to the branch point with reference to the branch point of the 3-terminal single-line power transmission line. The voltage at each point is calculated, and the difference between the two voltages of the calculated three voltages at the branch point is calculated to obtain the absolute value of the difference. The absolute values of the three differences are compared, and the smallest difference is calculated. 2 terminals corresponding to
The branch point is converted into a two-terminal single-line system between the branch point and a terminal other than the two terminals, as a terminal having a sum of the voltage and a current of two terminals connected to the branch point,
This is a method in which a single terminal line is regarded as a faulty section.

[0009]

The operation will be described with reference to FIG. FIG. 1 shows an n-terminal single-line power transmission line to which the present invention is applied. In any section, simple failure (type of failure (ground fault, short circuit, failure phase, etc.) does not matter) It is assumed that a failure that occurs at a point) has occurred.

The sign of each terminal is T₁, T₂, T₃, ...
T_nAnd the current flowing from each terminal is I₁, I₂，
I₃, ..., I_n, The voltage of each terminal is V₁, V₂, V₃，
...., V _nAnd Current I_i(i = 1, ..., N), voltage V_i
(i = 1, ..., n) is the vector of phase current and phase voltage,
It is expressed as follows.

[0011]

[Equation 1]

Here, a, b and c represent phases. Each element is a complex number with magnitude and phase. The branch point is b ₂ ,
b _3, ····, and b _n-1, the distance between the branch point and the terminal _{d 1, d 2, d 3} , ····, and _{d 2n-4, d 2n-} 3. Line impedance matrix Z _i (i =
1, ..., 2n-3)

[0013]

[Equation 2]

It is represented by. Each element is a complex number having a magnitude and a phase, s represents self and m represents each other. Also, the inner product of complex vectors is represented by <,>. For example,

[0015]

[Equation 3]

[0016] with respect to the current I, voltage V expressed by the inner product of complex vectors, <V, I> = I a * V a + I b * V b + I c * V c
(* Is a complex conjugate). Also, the absolute value of the vector is evaluated by the Euclidean norm, and the Euclidean norm is represented by ‖ ‖.

‖V‖ = √ <V, V> In the n-terminal single-line power transmission line of FIG. 1, first, the voltage at the branch point at either end, for example, the branch point b ₂ is calculated from the terminal T ₁ . If this is _written as V _b2,1 (the subscript means the voltage at the branch point b ₂ calculated from the terminal T ₁ ), then V _b2,1 = V ₁ −d ₁ Z ₁ I ₁ . Next, the voltage at the branch point b ₂ is calculated from the terminal T ₂ . Writing this with _V b2,2, the _{V b2,2 = V 2 -d 2 Z} 2 I 2.

The difference between the voltages is calculated, and this is written as Δ _1,2 . Δ _1,2 = ‖V _b2,1 −V _b2,2 ‖ Further, the voltage at the branch point at the other end and the branch point b _n-1 is applied to the terminal T.
Calculate from _n-1 . Writing this and _{V bn-1, n-1} , the _{V bn-1, n-1} = V n-1 -d 2n-4 Z 2n-4 I n-1.

Next, branch point b_n-1Voltage of terminal T_nFrom total
Calculate This is V_{bn-1, n}And write V_{bn-1, n}= V_n-1-D_2n-3Z_2n-3I_n Becomes The difference between the voltages is calculated, and this is_{n-1, n}And calligraphy
Ku. Δ_{n-1, n}= ‖V_{bn-1, n-1}-V_{bn-1, n}‖ Here, the differences calculated in the above procedure are compared. If Δ_1,2<Δ_{n-1, n} Then, section b₂~ T₁, Section b₂~ T₂For both
Judge that there is no failure. Then, the branch point b
₂The voltage V_b2,1Or V_b2,2(There are no breakdowns, so both voltages
(Which should be equal), the (n-1) end
Converts to a child single line system (see Fig. 2). At this time,
Branch point b₂Current I flowing into_b2Is the original terminal T₁Flow
Current I₁And terminal T₂Current I flowing through₂Is the sum of
From I_b2= I₁＋ I₂ Is. If Δ_1,2> Δ_{n-1, n} Then, section b_n-1~ T_n-1, Section b_n-1~ T_nYes
It is judged that there is no failure even if there is a gap. And the branch point
b_n-1The voltage V_{bn-1, n-1}Or V_{bn-1, n}With terminals having
Then, conversion to (n-1) terminal single line system is performed (Fig. 3
reference). Branch point b _n-1Current I flowing into_bn-1Is the original
Terminal T_n-1Current I flowing through_n-1And terminal T_nCurrent flowing through
I_nSum of I_bn-1= I_n-1＋ I_n Is. If Δ_1,2= Δ_{n-1, n} If so, branch point b₂To terminal or branch point b_n-1The edge
Do either operation to make it a child. Which to operate
You just have to promise in advance.

As described above, (n-1) terminal single line
If it is converted to (n-1) terminal single line
For, repeat the above procedure. And finally 2
Converting up to a single-line power transmission line,
The case where the three-terminal single line is converted will be described. Figure 4
Is a circuit diagram showing a three-terminal single-line power transmission line in the process of conversion.
Each terminal b_j-1, T_j, B_{j + 1}, Branch point b_j,each
The current flowing from the terminal is I_j-1′, I_j, I _{j + 1}',each
The terminal voltage is V_j-1′, V_j, V_{j + 1}’ here
The dash (') symbols attached to voltage and current are
Terminal T_jOther terminals b_j-1, B_{j + 1}Is not necessarily
Original terminal T_j-1, T_{j + 1}Because it does not match
Terminal T_j-1, T_{j + 1}To distinguish it from the voltage and current
Of.

Since the sections judged to have no failure are converted one after another, a failure should have occurred in any section of this three-terminal circuit. The voltage at the branch point b _j is calculated from the terminal b _j-1 and the terminal T _j . These voltages, and _{V bj, j-1 = V} j-1 '-d 2j-3 Z 2j-3 I j-1' V bj, j = V j -d 2j-2 Z 2j-2 I j Become.

The difference between the voltages is calculated, and this is written as Δ _{j, j-1} . Δ _{j, j-1} = ‖V _{bj, j-1} −V _{bj, j} ‖ Further, the voltage at the branch point b _j is calculated from the terminal b _{j + 1} and the terminal T _j . These voltages are V _{bj, j} = V _j -d _2j-2 Z _2j-2 I _j V _{bj, j + 1} = V _{j + 1'-} d _2j-3 Z _2j-3 I _{j + 1} ' The voltage difference Δ _{j, j + 1} is Δ _{j, j + 1} = ‖V _{bj, j + 1} −V _{bj, j} ‖.

Furthermore, the terminal b_j-1Voltage seen from V
_{bj, j-1}And terminal b_{j + 1}Voltage seen from V _{bj, j + 1j}Difference from
Δ_{j-1, j + 1}Take Δ_{j-1, j + 1}= ‖V_{bj, j-1}-V_{bj, j + 1}‖If the faulty section is b_j-1b_jBe in between
Then, Δ_{j, j-1}> 0 Δ_{j-1, j + 1}> 0 holds, whereas Δ_{j, j + 1}Is 0. Ie Δ_{j, j-1}> Δ_{j, j + 1} Δ_{j-1, j + 1}> Δ_{j, j + 1} Holds. Therefore, from the above inequality, the interval T_jb_j
And section b_jb_{j + 1}Is normal and section b_j-1b_jIs out of order
I know that

If the faulty section is between b _{j and} T _j , Δ _{j, j-1} > 0 Δ _{j, j + 1} > 0 holds, whereas Δ _{j-1, j +1} is 0. That is, Δ _{j, j-1} > Δ _{j-1, j + 1} Δ _{j, j + 1} > Δ _{j-1, j + 1} . Therefore, from the above inequality, the interval b _j-1 b
_j and the section b _j b j _{+ 1} is normal, it can be seen that the segment b _j T _j is faulty.

If the faulty section is b _j b _{j + 1}
If Δ _{j-1, j + 1} > 0 Δ _{j, j + 1} > 0 holds, Δ _{j-1, j} is 0. That is, Δ _{j, j + 1} > Δ _{j-1, j} Δ _{j-1, j + 1} > Δ _{j-1, j} holds. Therefore, from the above inequality, the interval b _j-1 b
It can be seen that _j and the section b _j T _j are normal, and the section b _j b _{j + 1} is out of order.

Hereinafter, the section in which a failure has occurred is represented by b _j-1 b _j.
In between (this does not lose generality). If the failure section is known, the branch point b _{j is set} to the voltage V _{bj, j} or V _{bj, j + 1} (both voltages should be the same because there is no failure) and the current I _j +.
A terminal having I _{j + 1} ′ is converted into a two-terminal single-line system between the terminal and the terminal b _j−1 (see FIG. 5). As described above, according to the present invention, an n (n ≧ 4) terminal single line can be converted into a three terminal single line including a failure section. After converting to a three-terminal single line, it can be converted to a two-terminal single line consisting of a failure section.

Next, a known method for calculating a fault point in a two-terminal single-line system will be briefly described. FIG. 6 is a two-terminal single-line circuit diagram, which is the same as the two-terminal single-line circuit diagram of FIG. 5 (however, the reference numerals have been rewritten to simple ones).
Hereinafter, description will be given with reference to FIG. Connect each terminal to T ₁ , T ₂ ,
The currents flowing from the terminals are I ₁ and I ₂ , and the voltages at the terminals are V ₁ and V ₂ . It is assumed that there is a failure at a distance x from the terminal T _1, the line impedance matrix per unit length of the line is Z, the voltage at the failure point is V _f , and the current flowing out from the failure point is I _f .

The following two expressions are established. _If the inner product of V _f = V ₁ -xZI _{1 If} = I ₁ + I ₂ V _f , _If is taken, the following formula is obtained. _{<V f, I f> =} <V 1 -xZI 1, I 1 + I 2> = <V 1, I 1 + I 2> -x <ZI 1, I 1 + I 2> This inner product is generated by fault point Although it shows the apparent power, the impedance at the failure point is considered to be a resistance component, so the inner product <V _f , I _f > on the left side is a real number. Therefore, taking the imaginary part, 0 = Im <V _f , _If > = Im <V ₁ , I ₁ + I ₂ > -xIm <ZI ₁ , I ₁ +
I ₂ >, and x = Im <V ₁ , I ₁ + I ₂ > / Im <ZI ₁ , I ₁ +
I ₂ > is obtained. However, Im represents the imaginary part of a complex number. In this way, the distance x to the failure point is obtained.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for selecting a failure section according to the present invention will be described below with reference to the accompanying drawings.
It will be described in detail based on. In addition, as shown in FIGS.
The same symbols are used for common ones. Figure 7 is general
4-terminal single-line power transmission line, and fault section selection according to the present invention
It is a figure which shows the fault locator applied to the selection method,
The 4-terminal single-line power transmission line L has a power transmission end T. ₁Place the power supply on the side
Then, loads (not shown) are applied to the power receiving end B, the power receiving end C, and the power receiving end D.
Power supply may be used).

At the power transmission end T ₁ of the 4-terminal single-line power transmission line L, a current transformer (collectively referred to as CT ₁ ) for measuring the currents of the phases a, b and c of the line and a power transmission end T ₁ are connected. Transformer PT that is connected to the bus bar and detects a-phase, b-phase, and c-phase voltages
₁ is connected. Also, at the receiving ends T ₂ , T ₃ , T ₄ , CT ₂ , CT ₃ , CT ₄ and receiving ends T ₂ , T ₃ , T _{4 for} measuring the currents of the a-phase, b-phase and c-phase of the line, respectively.
, PT ₂ , PT ₃ and PT ₄ for detecting the voltages of the a-phase, b-phase and c-phase, respectively.

Each of the power receiving terminals T ₂ , T ₃ and T ₄ has CT ₂ ,
Terminal stations 2, 3 and 4 are provided for sampling and digitally converting the detection outputs of CT ₃ , CT ₄ and PT ₂ , PT ₃ , PT ₄ and transmitting them to the fault locator 1. As shown in FIG. 8, the terminal stations 2, 3 and 4 each have an auxiliary transformer 21 for converting the read voltage / current of each phase into a voltage signal of a predetermined level, and the voltage signal converted by the auxiliary transformer 21 by a predetermined electrical angle ( A sample hold circuit 22 for sampling every 30 degrees, an A / D converter 23, and a communication device 24 for modulating voltage and current data and transmitting the data to the fault locator 1 are provided.

The fault locator 1 is, for example, the power transmission end T ₁
As shown in FIG. 9, the auxiliary transformer 11 for converting the read voltage / current of each phase into a voltage signal of a predetermined level, and the voltage signal converted by the auxiliary transformer 11 for a predetermined electric angle ( Sample hold circuit 12 for sampling every 30 degrees, A / D converter 13, A / D
A RAM 15 for storing the digital value converted by the D converter 13, a fault detection program, a fault section selection program, and a ROM 1 for storing a fault point locating program.
4, CPU 16 for performing fault detection calculation, fault section selection calculation, fault point location calculation, section length d ₁ , ..., D ₅ ,
A keyboard 19 for setting impedance Z _{i and the} like per unit length of each section of the 4-terminal single-line power transmission line L, and a display device 20 for displaying information such as a failure section calculated by the CPU 16 are provided. .

The above-mentioned failure detection calculation is well known, and for example,
For example, one of the phase currents or the magnitude of the zero phase current is the reference value.
Judgment is made based on whether or not The fault segment selection calculation is
As described above, here, 4 terminal single line power transmission is used.
The line L will be briefly described again. 4 terminals
One branch point of the single-line power transmission line L, for example, branch point b₂Based on
The branch point b₂2 terminal T connected to ₁, T₂
To the branch point b₂Considering the voltage drop in the section up to
Voltage at the branch point V_b2,1= V₁-D₁Z₁I₁ V_b2,2= V₂-D₂Z₂I₂ And calculate the voltage difference Δ_1,2Ask for.

Δ _1,2 = ‖V _b2,1 −V _b2,2 ‖ Further, the voltage at the branch point b ₃ is calculated from the terminals T ₃ and T ₄ . These voltages are V _b3,3 = V ₃ −d ₄ Z ₄ I ₃ V _b3,4 = V ₄ −d ₅ Z ₅ I ₄ , and the voltage difference Δ _3,4 is Δ _3,4 = ‖V _b3,3 −V _b3,4 ‖.

Here, the CPU 16 compares the differences calculated by the above procedure. Now, assuming that Δ _1,2 <Δ _3,4 , the branch point b from the two terminals T ₁ , T _2
It can be judged that there is no failure in the section up to ₂ and branch point b
₂ is _used as a terminal having the voltage V ₂ ′ V ₂ ′ = V _b2,1 or V _b2,2 for conversion into a three-terminal single line system. At this time, the current I ₂ ′ flowing into the branch point b ₂ is I ₂ ′ = I ₁ + I ₂ .

Next, the branch point b of this three-terminal single-line power transmission line
₃ based on the three-terminal b _2, T _3, T ₄ the branch point b ₃ in consideration of the voltage drop section between the branch point b ₃ from
The respective voltages are calculated. These voltages, the _{V b3,2 = V 2 '-d 3} Z 3 I 2' V b3,3 = V 3 -d 4 Z 4 I 3 V b3,4 = V 4 -d 5 Z 5 I 4 Become. The difference between these voltages is calculated.

Δ_3,2= ‖V_b3,2-V_b3,3‖ Δ_3,4= ‖V_b3,3-V_b3,4‖ Δ_2,4= ‖V_b3,2-V_b3,4‖ Then, compare the absolute values of the three differences, and select the smallest difference
Ask. That is, for example, Δ _3,4If so, terminal T₃~ Branch
Point b₃~ Terminal T_FourYou can judge that there is no failure in between
Wear. Therefore, terminal b₂~ Branch point b₃Breakdown in the section
I understand that there is.

The fault point locating calculation is as described above.
Terminal b₂~ Branch point b₃In the fault section of₂of
Voltage V₂′, Current I₂′, Branch point b₃Voltage V₃′, Electric
Flow I ₃′, Impedance Z per unit length₃, Section length
d₃The position of the fault point is calculated according to the following equation based on
It is arithmetic. x = Im <V₂′, I₂′ + I₃′> / Im <Z
I₂′, I₂′ + I₃′ ＞ In this way, know the failure section and determine the distance to the failure point.
You can ask.

The calculation result of the CPU 16 is the I / O device 18
To the display device 20, and the display device 20 displays the failure section and the position of the failure point.

[0040]

As described above, according to the present invention, when a failure occurs at one point, the n-terminal single line is identified as the failure section based on the voltage or current obtained at each end of the n-terminal single-line transmission line. After converting to a three-terminal single line, including a three-terminal single line, it can be converted to a two-terminal single line consisting of a faulty section.

Therefore, it becomes possible to specify the faulty section, and it is possible to search for the faulty point with a small amount of labor.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an n-terminal single-line power transmission line for explaining the principle of the present invention.

FIG. 2 is a circuit diagram after conversion in the case of conversion to an (n-1) terminal single-line system in which the branch point b ₂ at the end of the n-terminal single-line power transmission line is used as a reference. Is.

FIG. 3 is a branch point b _n-1 at the other end of the n-terminal single-line power transmission line.
FIG. 6 is a circuit diagram after conversion in the case of converting to a (n-1) terminal single line system with the branch point as a terminal on the basis of FIG.

FIG. 4 is a circuit diagram showing a three-terminal single-line power transmission line in the middle of conversion.

FIG. 5 is a circuit diagram after conversion in the case of conversion into a two-terminal single-line system using a branch point b _j of the three-terminal single-line power transmission line as a terminal.

6 is a two-terminal single-line circuit diagram similar to the two-terminal single-line circuit of FIG. 5 (however, the reference numerals have been rewritten to simple ones).

FIG. 7 is a diagram showing a layout of a four-terminal single-line power transmission line and a fault locator.

FIG. 8 is a block diagram of an internal configuration of a terminal station.

FIG. 9 is a block diagram of the internal configuration of a fault locator.

[Explanation of symbols]

1 Fault Locator 2, 3, 4 Terminal Station 16 CPU L 4 Terminal Single Line Power Transmission Line T ₁ Power Transmission Terminal T ₂ ~ T ₄ Power Reception Terminal

Claims (2)

[Claims] 1. When locating a failure point based on the voltage and current of each terminal of an n (n ≧ 4) terminal single-line power transmission line, each failure section when a failure occurs at one point is A method of selecting based on the voltage and current measured at a terminal, characterized by employing the following steps (a) to (f). (a) Considering the voltage drop in the section from the two terminals connected to the branch point to the branch point with reference to the branch point at either end of the series of branch points of the n-terminal single-line power transmission line The calculated voltage at the branch point is calculated, and the absolute value of the difference between the calculated two voltages at the branch point is calculated. (b) Of the series of branch points of the n-terminal single-line power transmission line, the branch point at the other end is used as a reference to connect to the branch point 2
The voltage at the branch point is calculated in consideration of the voltage drop in the section from the terminal to the branch point, and the absolute value of the difference between the calculated two voltages at the branch point is obtained. (c) Compare the absolute values of the differences calculated in steps (a) and (b) above, and for the branch point corresponding to the smaller difference,
The branch point is regarded as a terminal having a voltage calculated in consideration of a voltage drop in a section from the two terminals connected to the branch point to the branch point and a sum current of the two terminals connected to the branch point (n− 1) Convert to a single-line terminal system. (d) Regarding the (n-1) terminal single line power transmission line,
By repeating steps (a) to (c), conversion up to a 3-terminal single-line transmission line is performed. (e) Based on the branch point of the 3-terminal single-line power transmission line, 3
The voltage at the relevant branch point is calculated in consideration of the voltage drop in the section from the terminal to the relevant branch point, and the difference between the two voltages among the three voltages at the relevant branch point is calculated, and the absolute value of the difference is calculated. Ask for. (f) The absolute values of the three differences calculated in the procedure (e) above are compared, the two terminals corresponding to the smallest difference are determined, and the branch point is divided into the sections from the two terminals to the branch point. It is regarded as a terminal having a voltage calculated in consideration of a voltage drop and a sum current of two terminals connected to the branch point, and is converted into a two-terminal single-line system with terminals other than the two terminals. 2. A failure occurs at one point of a three-terminal single-line power transmission line.
The failure section in the case of₁, T₂, T₃Measured by
A method of selecting based on the applied voltage and current,
Failure characterized by adopting the following procedures (a) and (b)
Section selection method. (a) Based on the branch point b of the three-terminal single-line power transmission line,
3 terminal T₁, T₂, T ₃To the branch point b
Calculate the voltage at the branch point b in consideration of the voltage drop
Of the calculated three voltages at the branch point b,
The difference between the two voltages is calculated, and the absolute value of the difference is obtained. (b) Compare the three differences calculated in step (a) above,
2 terminal T corresponding to the smallest difference_i, T_jDecide
The branch point b is connected to the two terminals T_i, T_jTo branch point b
The voltage calculated in consideration of the voltage drop in the section
2-terminal T connected to the branch point_i, T_jEnd with sum current of
Considered as child b and other terminal T_k2 between (k ≠ i, j)
Convert to terminal single line system.