JP3656966B2 - Fault location system - Google Patents

Description

【０００５】
【発明が解決しようとする課題】
（３）式を用いて故障点を標定するには、各端子の電流値Ｉ_aR，Ｉ_bR，Ｉ_cRが既知である必要がある。しかしＣＴがない又は端末装置が設置されていない等の理由で電流値が取込めない端子があると標定できず、またその端子に流れる電流を用いず標定しても標定誤差が生じる欠点があった。
本発明は上記事情に鑑みてなされたものであり、電流データを入力できない端子があっても高精度に故障点を標定できる故障点標定装置を提供することを目的としている。
【０００６】
【課題を解決するための手段】
本発明の故障点標定装置は、多端子送電線の各端子から伝送される電圧，電流データを用いて送電線の事故点を標定する故障点標定装置において、前記多端子送電線はＡ，Ｂ，Ｃ，Ｍの４端子とし、前記Ａ，Ｂ端子の各線路の接続位置を第1の分岐点Ｊ１とすると共に、前記分岐点Ｊ１とＣ端子とは第２の分岐点Ｊ２を介して接続し、かつ前記第２の分岐点Ｊ２にはデータを測定する手段を有しないＭ端子を接続した系統構成を被監視系統とし、前記データを測定する手段を有しないＭ端子の事故前電流を推定する非測定データ推定手段と、Ａ端子から見た分岐点Ｊ１とＪ２の各電圧をＶ _Ｊ１Ａ ，Ｖ _Ｊ２Ａ ，Ｂ端子から見た分岐点Ｊ 1 の電圧をＶ _Ｊ１Ｂ ，Ｃ端子から見た分岐点Ｊ１とＪ２の各電圧をＶ _Ｊ１Ｃ ，Ｖ _Ｊ２Ｃ としたとき、下記の式により各分岐点の電圧Ｖ _Ｊ１Ａ ，Ｖ _Ｊ２Ａ ，Ｖ _Ｊ１Ｂ ，Ｖ _Ｊ１Ｃ ，Ｖ _Ｊ２Ｃ を算出する分岐点電圧算出手段と、前記非測定データ推定手段が推定した事故前電流と各端子で測定された電圧，電流データと前記各分岐点電圧とを用いて事故点を標定する標定演算手段とを備え、前記標定演算手段は第１の分岐点についてはそれを挟むＡ，Ｂ２端子からみた電圧値が等しいか否かを判断する第1の判断手段と、前記第１の判断結果が等しければ第２の分岐点についてそれを挟むＡ，Ｃ２端子からみた電圧値が等しいか否かを判断する第２の判断手段と、前記第１の判断手段の判断結果が等しくなければ前記第１の分岐点についてそれを挟むＡ，Ｃ２端子からみた電圧値が等しいか否かを判断する第３の判断手段と、前記第３の判断手段の判断結果が等しくなければ前記第1の分岐点についてそれを挟むＢ，Ｃ２端子からみた電圧値が等しいか否かを判断する第４の判断手段を有する事故発生区間を判断する手段と、前記事故発生区間の両端を用いて２端子扱いとして最終的な事故点を特定する手段とを備えた。
記

【０００７】
【実施例】
以下図面を参照して実施例を説明するが、それに先立って図１を用いて本願発明のシステム構成を３端子系統を例として説明する。図１において、電気所１,２には端末装置４,５が設置されており、データ入力部６,７からそれぞれの端子の電圧,電流データを入力し、送信部８,９及び伝送路１０,１１を介して中央判定装置１２へ伝送する。１３は受信部であって各端末装置４,５の送信部８,９に接続される。１４は標定部であり各端子１,２からのデータを用いて電気所３を流れる電流を求め、故障点を標定する。なお、電気所３には端末装置が設置されていないため、電気量の入力はできない。
【０００８】
そして中央判定装置１２にある標定部１４では、（３）式より事故点までの距離を求めるが、（３）式においてＩ_bRのデータは電気所３に端末装置がないため、直接知ることはできない。そこで電気所１，２の電流データから間接的に算出して求める。この場合、Ａ相１線地絡の場合はＢ端電流の各相電流は図２のベクトル図より（４）式となる。
【数２】

【０００９】
一方、Ｉ_bSはＡ端及びＣ端のＳ相電流の和となり、Ｉ_bTはＡ端及びＣ端のＴ相電流の和となるから、（５）式となる。（４），（５）式を（３）式へ代入して（６）式を得る。なお、（６）式は事故点までの距離である。
【数３】

【００１０】
次に端末装置及び中央判定装置の構成、及び内部処理について説明する。図３は端末装置の機能を示したものであり、データ入力手段１００は電圧，電流データを入力してサンプリングし、その瞬時値をアナログ／ディジタル変換する。データ記憶手段１０１はデータを一定時間分だけ記憶し、まとめて送信手段１０３へ送っている。送信手段１０３は、電流，電圧データと事故検出手段１０２から送られた事故発生フラグを、中央判定装置へ送信する。図４は事故検出手段の例である。データ入力処理手段１０４は電圧又は電流データを入力し、事故検出手段１０５はΔＶ又はΔＩが一定値以上になったときに事故発生と判定する。
【００１１】
図５は中央判定装置の機能を示したものである。自端電圧,電流データ入力手段２０１により、自端電圧,電流データを入力し、データ保存手段２０２により保存する。事故検出手段２０３は、系統に事故があったことを検出する手段で、端末装置の事故検出手段と同様に、図４のように構成できる。
電圧,電流データ受信手段２０４は、他端子の端末装置から電圧,電流データを受信する。負荷電流演算手段２０５は、端末装置の設置されていない端子に流れる負荷電流を、演算により求める手段で２０１,２０４により入力したデータを用いて（４）式，（５）式のようにして求める。事故点標定手段２０６における標定は、前記（６）式のアルゴリズムに従い、次式により求める。なお、以下に示す（７）式はＡ端子と分岐点間のＲ相１線地絡事故の場合（Ａ端からの距離）を示し、（８）式はＣ端と分岐点間のＲ相１線地絡事故の場合（Ｃ端からの距離）を示している。
【００１２】
【数４】

【００１３】
図６は参考例の構成図である。本例は中央判定装置１７を電気所１にて設置して、端末装置と機能を兼用した点が図１と異なる。この場合の中央判定装置１７は、自端の電圧，電流データを入力するデータ入力部６と端末装置５からの電圧，電流データを受信する受信部１５と、標定部１６とからなる。なお、事故点標点のアルゴリズムは図１の場合と同一である。
【００１４】
図８は本実施例の故障点標定装置を電力系統に適用したシステム構成図であり、４端子系統を例として示し説明する。なお、図９は故障点標定装置１９が実施する手段の流れ図である。図８において、電気所Ａ，Ｂ，Ｃはデータを測定する端子、電気所Ｍはデータを測定しない端子（非測定端子）、Ｊ_１，Ｊ_２，は分岐点１_Ａ,１_Ｂ,１_Ｃ,１_Ｄは各区間の線路長、Ｚ_Ａ，Ｚ_Ｂ，Ｚ_Ｃ，Ｚ_Ｄは各区間の単位長当りのインピーダンス、１８は伝送装置、１９は故障点標定装置（中央判定装置）、１９ａ，１９ｂ，１９ｃはそれぞれ故障点標定装置１９の受信回路，演算回路，表示回路である。故障点標定の対象区間の各端子Ａ〜Ｃの電圧，電流データは夫々の伝送装置１８を介して故障点標定装置１９の受信回路１９ａに入力され、このデータを用いて演算回路１９ｂが標定演算を行ない、表示回路１９ｃに出力する。
【００１５】
次に図９を用いて本実施例の標定処理を説明する。図９において、２１は非測定データ推定手段、２２は分岐点電圧算出手段、２３は事故区間判定手段、２４は標定演算手段、２５は出力手段である。手段２１はＡ〜Ｃ端子の測定データを用いてＭ端子のデータを推定し、手段２２は各端子のデータを使ってＡ〜Ｃ端子から見た分岐点Ｊ₁ ，Ｊ₂ の電圧を算出する。手段２３は手段２２が算出した分岐点電圧を比較して事故の有無，事故区間の判定を行ない、事故が検出されたとき手段２４で事故点の標定演算を行ない、結果を手段２５が表示回路に出力する。以下に各手段の詳細を説明する。
【００１６】
送電線に事故がない平常時はＭ端子の負荷電流＊Ｉ_M は（９）式で求められるので、非測定データ推定手段２１は（１０）式のようにＮサイクル前の値をＭ端子の事故前電流として推定する。
【数５】

【００１７】
次に、分岐点電圧算出手段２２はＡ端子から見た分岐点Ｊ₁ とＪ₂ の電圧＊Ｖ_J1A ，＊Ｖ_J2A 、Ｂ端子から見た分岐点Ｊ₁ の電圧＊Ｖ_J1B 、Ｃ端子から見た分岐点Ｊ₁ とＪ₂ の電圧＊Ｖ_J1C ，＊Ｖ_J2C を（１１）式で算出する。
【数６】

【００１８】
事故区間判定手段２３で行なう処理を図１０に示す。図１０は本発明の事故区間判定手段の処理フローチャートであり、上記（１１）式をもとに図１０を用いて事故判定をする。
（イ）先ずステップ３１ではＶ_J1A とＶ_JIB とが等しいか否かを判断し、これが等しければステップ３２へ移ってＶ_J2C とＶ_J2A とが等しいか否かを判断する。ステップ３２でＶ_J2C とＶ_J2A とが等しければステップ３３で事故なしまたは外部事故と判定する。
（ロ）ステップ３２においてＶ_J2C とＶ_J2A とが等しくなければ、ステップ３４へ移って分岐点ｊ₁ とＣ端間の事故と判定する。
（ハ）ステップ３１においてＶ_J1A とＶ_JIB とが等しくなければ、ステップ３５へ移ってステップ３５にてＶ_J1A とＶ_J1C とが等しいか否かを判定する。ステップ３５においてＶ_J1A とＶ_J1C とが等しければ、ステップ３６にて分岐点ｊ₁ とＢ端間の事故と判定する。
（ニ）ステップ３５においてＶ_J1A とＶ_J1C とが等しくなければステップ３７へ移ってＶ_JIB とＶ_J1C とが等しいか否かを判定する。ステップ３７においてＶ_JIB とＶ_J1C とが等しければ、ステップ３８にて分岐点ｊ₁ とＡ端間の事故と判定する。なお、ステップ３７においてＶ_JIB とＶ_J1C とが等しくなければ終了する。
【００１９】
事故点がいずれの区間においても最終的には２端子扱いと等価となり、事故区間両端の電圧，電流を使って、事故点の残り電圧が等しいという条件を利用する基本式で標定を行なうことができる。標定演算手段２４は次のように標定演算を行なう。
【数７】

【００２０】
出力手段２５は事故点までの距離を表示回路に出力する。以上によりデータを測定しない端子があっても精度よく標定を行なうことができる。
以上説明したように、本発明によれば測定端子のデータを用いて非測定端子の事故前電流を推定し、この推定値でデータを補正するようにしたので、データの非測定端子があっても精度よく故障点標定を行なうことができる。
【００２１】
【発明の効果】
以上説明したように、本発明によれば電流データの取込めない端子があっても、他の端子の電流データを用いて演算する構成としたので、事故点標定が可能となる。
【図面の簡単な説明】
【図１】本発明による故障点標定装置のシステム構成図。
【図２】Ａ相１線地絡の場合におけるＢ端電流の各相電流のベクトル図。
【図３】端末装置の機能を説明する図。
【図４】事故検出手段の機能を説明する図。
【図５】中央判定装置の機能を説明する図。
【図６】参考例の構成図。
【図７】故障点標定の原理を説明する電力系統図。
【図８】本発明による故障点標定装置の実施の形態を示す図。
【図９】図８の処理内容を示すフローチャート図。
【図１０】事故区間判定手段の処理内容を示すフローチャート。
【符号の説明】
１，２，３ 電気所
４，５ 端末装置
６，７ データ入力部
８，９ 送信部
１０，１１ 伝送路
１２，１７ 中央判定装置
１３ 受信部
１４ 標定部
１８ 伝送装置
１９ 故障点標定装置[0001]
[Industrial application fields]
The present invention relates to a failure point locating device for locating an accident point using the amount of electricity at each terminal of a transmission line of a multi-terminal transmission line.
[0002]
[Prior art]
The fault location using the voltage and current of each terminal of a multi-terminal transmission line with 3 or more terminals to determine the distance to the accident point is the remaining voltage at the accident point calculated from the voltage and current data of the terminals on both sides of the accident point. (For example, Japanese Patent Laid-Open No. 58-208676).
[0003]
This will be described with reference to the power system diagram of FIG. FIG. 7 shows a three-terminal system in which three electrical stations A _SS , B _SS , C _SS are connected at branch point J by line lengths l _a , l _b , and l _c , and at point F between A and J. The case where an R-phase 1-wire ground fault occurs is shown. In this case, the R-phase voltage at each electric station is * V _aR , * V _bR , * V _cR , the current is * I _aR , * I _bR , * I _cR , and the line impedance per unit length is * Z _a , * Z _b, * when the Z _c, the fault point voltage V _FR of the R phase, when a quantity of electricity substation a _SS, the equation (1). In addition, * mark is a vector quantity (hereinafter the same).
[0004]
[Expression 1]

[0005]
[Problems to be solved by the invention]
In order to determine the failure point using the equation (3), the current values I _aR , I _bR , and I _{cR of} each terminal need to be known. However, if there is a terminal that cannot capture the current value due to reasons such as no CT or no terminal device installed, it cannot be standardized, and even if standardization is performed without using the current flowing through the terminal, there is a drawback that a standardization error occurs. It was.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a failure point locating device capable of locating a failure point with high accuracy even if there is a terminal that cannot input current data.
[0006]
[Means for Solving the Problems]
The failure point locating device according to the present invention is a failure point locating device for locating an accident point of a transmission line using voltage and current data transmitted from each terminal of the multi-terminal transmission line. , C and M, the connection position of each line of the A and B terminals is a first branch point J1, and the branch point J1 and the C terminal are connected via a second branch point J2. In addition, a system configuration in which an M terminal having no means for measuring data is connected to the second branch point J2 is a monitored system, and the pre-accident current of the M terminal having no means for measuring the data is estimated. Non-measurement data estimation means, and the voltages at the branch points J1 and J2 viewed from the A terminal are V _J1A and V _J2A , and the voltage at the branch point J 1 viewed from the B terminal is the branch point viewed from the V _J1B and C terminals When each voltage of J1 and J2 is V _J1C and V _J2C , The branch point voltage calculation means for calculating the voltages V _J1A , V _J2A , V _J1B , V _J1C , V _J2C at each branch point, the pre-accident current estimated by the non-measurement data estimation means, and each terminal And an orientation calculation means for locating an accident point using the voltage and current data and each branch point voltage, and the orientation calculation means has a voltage value viewed from the A and B2 terminals sandwiching the first branch point. First determination means for determining whether or not the two are equal, and if the first determination result is equal, the first determination means determines whether or not the voltage values seen from the A and C2 terminals sandwiching the second branch point are equal. If the determination result of the second determination means and the determination result of the first determination means are not equal, the third determination means for determining whether or not the voltage values seen from the A and C2 terminals sandwiching the first branch point are equal. And the third determining means Means for determining the accident section to have a fourth determining means for determining whether the voltage equal value as seen from B, C2 terminals sandwiching the for the first branching point must be equal determination result, the And means for identifying the final accident point as a two-terminal treatment using both ends of the accident occurrence section.
Record

[0007]
【Example】
The embodiment will be described below with reference to the drawings . Prior to that, the system configuration of the present invention will be described using a three-terminal system as an example with reference to FIG. In FIG. 1, terminal devices 4 and 5 are installed at electric stations 1 and 2, and voltage and current data of respective terminals are input from data input units 6 and 7, and transmission units 8 and 9 and transmission line 10 are input. , 11 to the central determination device 12. A receiving unit 13 is connected to the transmitting units 8 and 9 of the terminal devices 4 and 5. Reference numeral 14 denotes an orientation unit which obtains a current flowing through the electric station 3 using data from the terminals 1 and 2 and locates a failure point. In addition, since the terminal device is not installed in the electric station 3, the amount of electricity cannot be input.
[0008]
Then, the orientation unit 14 in the central determination device 12 calculates the distance to the accident point from the equation (3). However, in the equation (3), the data of I _bR does not have a terminal device at the electric station 3, so that it can be directly known. Can not. Therefore, it is obtained by indirectly calculating from the current data of the electric stations 1 and 2. In this case, in the case of an A-phase 1-wire ground fault, each phase current of the B-end current is expressed by equation (4) from the vector diagram of FIG.
[Expression 2]

[0009]
On the other hand, I _bS is the sum of the S-phase currents at the A and C ends, and I _bT is the sum of the T-phase currents at the A and C ends. Substituting Equations (4) and (5) into Equation (3) to obtain Equation (6). Equation (6) is the distance to the accident point.
[Equation 3]

[0010]
Next, the configuration of the terminal device and the central determination device and the internal processing will be described. FIG. 3 shows the function of the terminal device. The data input means 100 inputs voltage and current data, samples them, and converts the instantaneous values from analog to digital. The data storage unit 101 stores data for a predetermined time and sends it to the transmission unit 103 collectively. The transmission unit 103 transmits the current / voltage data and the accident occurrence flag sent from the accident detection unit 102 to the central determination device. FIG. 4 shows an example of the accident detection means. The data input processing means 104 inputs voltage or current data, and the accident detection means 105 determines that an accident has occurred when ΔV or ΔI exceeds a certain value.
[0011]
FIG. 5 shows the function of the central determination device. The local voltage / current data input means 201 inputs the local voltage / current data, and the data storage means 202 stores the data. The accident detection means 203 is a means for detecting that an accident has occurred in the system, and can be configured as shown in FIG. 4 in the same manner as the accident detection means of the terminal device.
The voltage / current data receiving means 204 receives voltage / current data from the terminal device at the other terminal. The load current calculation means 205 obtains the load current flowing through the terminal where the terminal device is not installed by means of the calculation using the data input by 201 and 204 as shown in the equations (4) and (5). . The orientation in the accident point location means 206 is obtained by the following equation according to the algorithm of the above equation (6). The following equation (7) shows the case of an R-phase 1-wire ground fault between the A terminal and the branch point (distance from the A end), and equation (8) shows the R phase between the C end and the branch point. for 1-line ground fault that indicates the (distance from C-terminal).
[0012]
[Expression 4]

[0013]
FIG. 6 is a block diagram of a reference example. This example is different from FIG. 1 in that a central determination device 17 is installed at the electric station 1 and functions as a terminal device. The central determination device 17 in this case includes a data input unit 6 for inputting voltage and current data at its own end, a receiving unit 15 for receiving voltage and current data from the terminal device 5, and an orientation unit 16. The algorithm for the accident point mark is the same as in FIG.
[0014]
FIG. 8 is a system configuration diagram in which the failure point locating device of this embodiment is applied to an electric power system. A four-terminal system will be described as an example. Incidentally, FIG. 9 is a flow diagram of means for performing the fault point locating system 19. In FIG. 8, electric stations A, B, and C are terminals that measure data, electric stations M are terminals that do not measure data (non-measuring terminals), and J ₁ and J ₂ are branch points 1 _A , 1 _B , and 1 _C. , 1 _D is the line length of each section, Z _A , Z _B , Z _C , Z _D are impedances per unit length of each section, 18 is a transmission device, 19 is a fault location device (central determination device), 19a, Reference numerals 19b and 19c denote a receiving circuit, an arithmetic circuit, and a display circuit of the failure point locator 19, respectively. The voltage and current data of the terminals A to C in the target section of the fault location are input to the receiving circuit 19a of the fault location device 19 via the respective transmission devices 18, and the arithmetic circuit 19b uses the data to perform the location calculation. And output to the display circuit 19c.
[0015]
Next, the orientation process of the present embodiment will be described with reference to FIG. In FIG. 9, 21 is a non-measurement data estimation means, 22 is a branch point voltage calculation means, 23 is an accident section determination means, 24 is an orientation calculation means, and 25 is an output means. The means 21 estimates the data of the M terminal using the measurement data of the A to C terminals, and the means 22 calculates the voltages at the branch points J ₁ and J ₂ viewed from the A to C terminals using the data of each terminal. . The means 23 compares the branch point voltage calculated by the means 22 to determine the presence or absence of an accident and the section of the accident. When an accident is detected, the means 24 performs the fault point location calculation, and the result is displayed on the display circuit 25. Output to. Details of each means will be described below.
[0016]
Since normal time no accident in the transmission line is the load current * I _M of the M-terminal obtained in (9), the non-measured data estimating means 21 the previous value of N cycles of M terminals as (10) Estimated as current before accident.
[Equation 5]

[0017]
Then, the branch point voltage calculation unit 22, the voltage of the branch point J ₁ and J ₂ as viewed from the A terminal * V _J1A, * V _J2A, the voltage of the branch point J ₁ as seen from the B terminal * V _J1B, from the C terminal The voltages * V _J1C and * V _J2C at the viewed branch points J ₁ and J ₂ are calculated by the equation (11).
[Formula 6]

[0018]
The processing performed by the accident section determination means 23 is shown in FIG. FIG. 10 is a process flowchart of the accident section determination means of the present invention. The accident is determined using FIG. 10 based on the above equation (11).
(A) First, in step 31, it is determined whether V _J1A and V _JIB are equal. If they are equal, the process _proceeds to step 32 to determine whether V _J2C and V _J2A are equal. If V _J2C and V _J2A are equal in step 32, it is determined in step 33 that there is no accident or an external accident.
(Ii) if not equal to the V _J2C and V _J2A In step 32, it is determined that the accident between the branch point j ₁ and C terminal proceeds to step 34.
(C) If V _J1A and V _JIB are not equal in step 31, the _{process proceeds} to step 35 and it is determined in step 35 whether V _J1A and V _J1C are equal. Being equal and V _J1A and V _J1C In step 35, it is determined that the accident between the branch point j ₁ and B end at step 36.
(D) If V _J1A and V _J1C are not equal in step 35, the _{process proceeds} to step 37 to determine whether V _JIB and V _J1C are equal. If V _JIB and V _J1C are equal in step 37, it is determined in step 38 that there is an accident between the branch point j ₁ and the A end. Note that if V _JIB and V _J1C are not equal in step 37, the process ends.
[0019]
In any section, the fault point will eventually be equivalent to a two-terminal treatment, and the voltage and current at both ends of the fault section will be used to standardize using the basic equation that uses the condition that the remaining voltage at the fault point is equal. it can. The orientation calculation means 24 performs the orientation calculation as follows.
[Expression 7]

[0020]
The output means 25 outputs the distance to the accident point to the display circuit. Thus, even if there is a terminal that does not measure data, the orientation can be performed with high accuracy.
As described above, according to the present invention, the pre-accident current of the non-measurement terminal is estimated using the data of the measurement terminal, and the data is corrected with this estimated value. Also, fault location can be performed with high accuracy.
[0021]
【The invention's effect】
As described above, according to the present invention , even if there is a terminal from which current data cannot be captured, the calculation is performed using the current data of the other terminals, so that it is possible to determine the accident point.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a fault location apparatus according to the present invention.
FIG. 2 is a vector diagram of each phase current of a B-end current in the case of an A-phase 1-wire ground fault .
FIG. 3 is a diagram illustrating functions of a terminal device.
FIG. 4 is a diagram for explaining the function of accident detection means.
FIG. 5 is a diagram for explaining functions of a central determination device.
FIG. 6 is a configuration diagram of a reference example.
FIG. 7 is a power system diagram illustrating the principle of fault location.
FIG. 8 is a diagram showing an embodiment of a fault location apparatus according to the present invention.
FIG. 9 is a flowchart showing the processing content of FIG . 8 ;
FIG. 10 is a flowchart showing processing contents of an accident section determination unit.
[Explanation of symbols]
1, 2, 3 Electricity station 4, 5 Terminal device 6, 7 Data input unit 8, 9 Transmission unit 10, 11 Transmission path 12, 17 Central determination device 13 Reception unit 14 Location unit 18 Transmission unit 19 Failure point location device

Claims (1)

In the failure point locating device for locating the fault point of the transmission line using the voltage and current data transmitted from each terminal of the multi-terminal transmission line, the multi-terminal transmission line has four terminals A, B, C, and M, The connection position of each line of the A and B terminals is a first branch point J1, the branch point J1 and the C terminal are connected via a second branch point J2, and the second branch point A non-measurement data estimation means for estimating the pre-accident current of the M terminal, which has a system configuration in which an M terminal having no means for measuring data is connected to J2 as a monitored system, and does not have the means for measuring the data; The voltages at the branch points J1 and J2 viewed from the terminals are V _J1A and V _J2A , the voltage at the branch point J 1 viewed from the B terminal is V _J1B , and the voltages at the branch points J1 and J2 viewed from the C terminal are V _J1C. , V _J2C , the voltage V at each branch point is _J1A , V _J2A , V _J1B , V _J1C , V _J2C calculating branch point voltage calculating means, pre-accident current estimated by the non-measurement data estimating means, voltage measured at each terminal, current data, and each branch An orientation calculation means for locating the accident point using the point voltage, and the orientation calculation means determines whether or not the first branch point has the same voltage value seen from the A and B2 terminals sandwiching it. If the first determination result is equal to the first determination means, the second determination means for determining whether or not the voltage values seen from the A and C2 terminals sandwiching the second branch point are equal to each other. If the judgment results of the judgment means are not equal, the third judgment means for judging whether the voltage values seen from the A and C2 terminals sandwiching the first branch point are equal, and the third judgment means If judgment result is not equal Means for determining a serial first accident section to have a fourth determining means for determining whether the voltage equal value as seen from B, C2 terminals sandwiching the bifurcation point, both ends of the accident section And a means for identifying a final accident point as a two-terminal treatment.
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