JP3550679B2

JP3550679B2 - Substation failure section determination device

Info

Publication number: JP3550679B2
Application number: JP18163099A
Authority: JP
Inventors: 敏晴山田
Original assignee: Takaoka Electric Mfg Co Ltd
Current assignee: Takaoka Electric Mfg Co Ltd
Priority date: 1999-06-28
Filing date: 1999-06-28
Publication date: 2004-08-04
Anticipated expiration: 2019-06-28
Also published as: JP2001016767A

Description

【０００１】
【発明の属する技術分野】
本発明は、送電用変電所の内部で地絡または短絡事故が発生した際に、故障区間を自動的に検出することができる変電所の故障区間判定装置に関する。
【０００２】
【従来の技術】
２重母線方式の送電用変電所の故障区間を検出する装置は、例えば、特開平２−２２３３３４号公報に記載されている。図１２は従来の変電所故障区間検出システムの一例を示したものである。
図１２において、１は第１の母線（以下、甲母線とする。）、２は第２の母線（以下、乙母線とする。）、５，６は第１および第２の変圧器バンク（以下、バンクとする。）、１０，１１は第１および第２の負荷線路である。各バンク５，６および各負荷線路１０，１１は、甲母線１と乙母線２の中央にある人形部と呼ばれる部分からそれぞれの甲母線側断路器３ａ〜６ａ、および乙母線側断路器３ｂ〜６ｂによって、甲母線１および乙母線２の両方に接続できる構造となっているが、通常は甲母線側断路器３ａ〜６ａあるいは乙母線側断路器３ｂ〜６ｂのいずれか一方を閉じ、他方を開くことによって、甲母線１あるいは乙母線２のいずれかに選択的に接続されている。図１２はその標準的な接続を示し、甲母線１は第１のバンク５から給電され、乙母線２は第２のバンク６から給電されるようになっている。また、第１の負荷線路１０は甲母線１に接続され、第２の負荷線路１１は乙母線２に接続されている。
【０００３】
３ｃ〜６ｃはバンク５，６の人形部および負荷線路１０，１１の人形部の甲母線側断路器３ａ〜６ａの近傍にそれぞれ取り付けた光ＣＴであり、各人形部から甲母線１へ出入する電流を検出するための電流センサである。同様に、３ｄ〜６ｄはバンク５，６の人形部および負荷線路１０，１１の人形部の乙母線側断路器３ｂ〜６ｂの近傍にそれぞれ取り付けた光ＣＴであり、各人形部から乙母線２へ出入りする電流を検出するための電流センサである。また、７は甲母線１の計器用変圧器、８は乙母線２の計器用変圧器である。９は光ＣＴ３ｃ〜６ｃおよび光ＣＴ３ｄ〜６ｄの出力信号を伝達する光ファイバケーブルである。
【０００４】
３ｇ〜６ｇは光ＣＴ３ｃ〜６ｃで検出した電流に応動する方向継電器であり、甲母線１の母線電圧を基準に各人形部の甲母線１側を通過する事故電流の方向を判別する。３ｈ〜６ｈは光ＣＴ３ｄ〜６ｄで検出した電流に応動する方向継電器であり、乙母線２の母線電圧を基準に各人形部の乙母線２側を通過する事故電流の方向を判別する。
このように２つの母線１，２に複数のバンク５，６と複数の負荷線路１０，１１とを接続した変電所の各バンク側人形部および各線路側人形部の母線断路器３ａ〜６ａ，３ｂ〜６ｂの近傍に、光ＣＴ３ｃ〜６ｃ，３ｄ〜６ｄを取り付けるとともに、光ＣＴ３ｃ〜６ｃ，３ｄ〜６ｄからの事故電流の方向を検出できる方向継電器３ｇ〜６ｇ，３ｈ〜６ｈを設け、母線事故発生時の事故電流を光ＣＴ３ｃ〜６ｃ，３ｄ〜６ｄによって検出し、その電流から方向継電器３ｇ〜６ｇ，３ｈ〜６ｈによって事故電流の流れる方向を判別し、その結果を判定部１６に入力して事故が発生した区間を自動的に検出していた。
【０００５】
ここで、上記従来の故障区間判定装置において、光ＣＴ３ｃ〜６ｃ，３ｄ〜６ｄからの事故電流の流れる方向を判別するための方向継電器３ｇ〜６ｇ，３ｈ〜６ｈについて説明する。
従来の故障区間判定装置の方向継電器３ｇ〜６ｇ，３ｈ〜６ｈとしては、短絡電流の方向判別には短絡方向継電器を、地絡電流の方向判別には地絡方向継電器をそれぞれ用いていた。
【０００６】
なお、図７は短絡方向継電器および地絡方向継電器の動作特性の一例を示したものである。短絡方向継電器ＲＹは、同図（ａ）に示すように、線間電圧Ｖを基準に相電流Ｉの位相差が所定範囲内の時に動作する継電器であり、３相短絡および２相短絡に応動できるように、例えば、９０°進み接続方式の場合には、Ａ相電流はＢＣ線間電圧を基準に、Ｂ相電流はＣＡ線間電圧を基準に、Ｃ相電流はＡＢ線間電圧を基準に位相差判定を行い、それら３相毎の位相差判定のＯＲ条件で動作信号を出力する構成とし、継電器設置点から見た短絡電流の方向、即ち、短絡事故発生点の方向を判別する継電器である。
同様に、地絡方向継電器ＲＹは、同図（ｂ）に示すように、零相電圧Ｖｏを基準に零相電流Ｉｏの位相差が所定範囲内の時に動作する継電器であり、継電器設置点から見た地絡電流の方向、即ち、地絡発生点の方向を判別する継電器である。
【０００７】
【発明が解決しようとする課題】
次に、上記従来の変電所故障区間判定装置を直接接地方式の変電所に適用する場合の問題点について説明する。
直接接地方式の変電所では、各受電線の送電端にある電源変圧器および各バンク変圧器の中性点が直接接地されているため、零相インピーダンスが小さく、そのため、地絡電流は短絡電流と同程度の非常に大きな事故電流となるが、零相電圧は殆ど発生しない。
したがって、零相電圧を基準に地絡電流の方向判別を行う地絡方向継電器では、基準となる零相電圧が十分に得られないことから地絡電流の方向判別が困難となる。即ち、従来の変電所故障区間判定装置は、直接接地方式の変電所における地絡時の故障区間判定が困難となる問題がある。
【０００８】
この問題に対応するため、地絡電流が短絡電流と同程度の非常に大きな電流になることを利用して、地絡電流の方向判別も短絡電流の方向判別と同様に前述の短絡方向継電器で行うことが考えられるが、直接接地方式の変電所の母線の地絡事故では、地絡相だけでなく、直接接地されたバンク変圧器中性点を通して地絡の発生していない健全相にも地絡電流が分流して流れるため、短絡方向継電器の健全相側の位相差判定が不要動作する問題がある。
【０００９】
以下に、直接接地方式の変電所において地絡が発生した場合の地絡相および健全相に流れる地絡電流と、その地絡電流に対する短絡方向継電器の応動について説明する。
図８は、直接接地系統にＡ相１線地絡が発生した場合を例に、地絡電流Ｉｇの流れる方向を示したものである。同図に示すように、直接接地系統では電源変圧器ＴＲ１およびバンク変圧器ＴＲ２の中性点Ｅ１，Ｅ２が共に直接接地されているため、地絡電流Ｉｇは電源変圧器ＴＲ１の中性点Ｅ１とバンク変圧器ＴＲ２の中性点Ｅ２に向かって分流して流れ、それぞれの中性点Ｅ１，Ｅ２から系統に流入する。この分流比は地絡点Ｐから見た電源側の零相インピーダンスとバンク側を見た零相インピーダンスの逆比となる。
【００１０】
バンク変圧器ＴＲ２の中性点Ｅ２から系統に流入した地絡電流の分流分Ｉｇ２は、更にバンク変圧器ＴＲ２の各相コイルに１／３ずつ分流し、地絡点Ｐよりバンク変圧器ＴＲ２側の地絡相電流Ｉａ２と地絡の発生していない健全相の相電流であるＢ相電流ＩｂおよびＣ相電流Ｉｃ（以下、健全相電流Ｉｂ，Ｉｃとする。）となる。地絡相電流Ｉａ２は地絡点Ｐまで流れ、健全相電流Ｉｂ，Ｉｃは、電源変圧器ＴＲ１のｂ相，ｃ相のコイルを通り、電源変圧器ＴＲ１の中性点Ｅ１から流入してくるもう一方の地絡電流Ｉｇの分流分Ｉｇ１と合成されて、地絡点Ｐより電源変圧器ＴＲ１側の地絡相電流Ｉａ１となり、電源変圧器ＴＲ１のａ相コイルを経由して地絡点Ｐまで流れる。
【００１１】
このような直接接地系統の１線地絡電流Ｉｇは、対称座標法によって（１）式のように求めることができる。
Ｉｇ＝３Ｅａ／（Ｚ_０＋Ｚ_１＋Ｚ_２）・・・・・・・・（１）
但し、Ｅａ＝地絡発生前の地絡点の対地電圧
Ｚ_０＝地絡点から見た系統全体の零相インピーダンス
Ｚ_１＝地絡点から見た系統全体の正相インピーダンス
Ｚ_２＝地絡点から見た系統全体の逆相インピーダンス
【００１２】
また、図９は直接接地系統の零相回路である。同図より、地絡点Ｐから見た系統全体の零相インピーダンスＺ_０は、地絡点Ｐから電源変圧器ＴＲ１側の零相インピーダンスＺ_０１および地絡点Ｐからバンク変圧器ＴＲ２側の零相インピーダンスＺ_０２の並列回路であるため、（２）式のように表すことができる。
Ｚ_０＝Ｚ_０１・Ｚ_０２／（Ｚ_０１＋Ｚ_０２）・・・・（２）
但し、Ｚ_０１＝地絡点Ｐから電源変圧器ＴＲ１側の零相インピーダンス
Ｚ_０２＝地絡点Ｐからバンク変圧器ＴＲ２側の零相インピーダンス
【００１３】
更に、地絡点Ｐから電源変圧器ＴＲ１側の零相インピーダンスＺ_０１および地絡点Ｐからバンク変圧器ＴＲ２側の零相インピーダンスＺ_０２は（３）式および（４）式となる。
Ｚ_０１＝Ｚ_Ｌ０１＋ｊＸ_ｔ１・・・（３）
Ｚ_０２＝Ｚ_Ｌ０２＋ｊＸ_ｔ２・・・（４）
但し、Ｚ_Ｌ０１＝地絡点Ｐから電源変圧器ＴＲ１までの線路の
零相インピーダンス
Ｚ_Ｌ０２＝地絡点Ｐからバンク変圧器ＴＲ２までの線路の
零相インピーダンス
Ｘ_ｔ１＝電源変圧器ＴＲ１の零相インピーダンス（リアクタンス）
Ｘ_ｔ２＝バンク変圧器ＴＲ２の零相インピーダンス（リアクタンス）
【００１４】
同様に、地絡点Ｐから見た系統全体の正相インピーダンスＺ_１および逆相インピーダンスＺ_２についても、地絡点Ｐから電源変圧器ＴＲ１側の正相および逆相インピーダンスＺ_１１，Ｚ_２１と地絡点Ｐからバンク変圧器ＴＲ２側の正相および逆相インピーダンスＺ_１２，Ｚ_２２の並列回路であるため、（５）式および（６）式のように表すことができる。
Ｚ_１＝Ｚ_１１・Ｚ_１２／（Ｚ_１１＋Ｚ_１２）・・・・・（５）
Ｚ_２＝Ｚ_２１・Ｚ_２２／（Ｚ_２１＋Ｚ_２２）・・・・・（６）
但し、Ｚ_１１＝地絡点Ｐから電源変圧器ＴＲ１側の正相インピーダンス
Ｚ_２１＝地絡点Ｐから電源変圧器ＴＲ１側の逆相インピーダンス
Ｚ_１２＝地絡点Ｐからバンク変圧器ＴＲ２側の正相インピーダンス
Ｚ_２２＝地絡点Ｐからバンク変圧器ＴＲ２側の逆相インピーダンス
【００１５】
ここで、計算簡略化のため、地絡点Ｐから見た系統全体の正相インピーダンスＺ_１および地絡点Ｐから見た系統全体の逆相インピーダンスＺ_２は小さいので無視すると、（２）式を（１）式に代入して、地絡電流Ｉｇを（７）式のように求めることができる。

【００１６】
また、電源変圧器ＴＲ１およびバンク変圧器ＴＲ２のそれそれの中性点Ｅ１，Ｅ２に分流する地絡電流は地絡点Ｐから電源変圧器ＴＲ１側を見た零相インピーダンスＺ_０１と地絡点Ｐからバンク変圧器ＴＲ２側を見た零相インピーダンスＺ_０２の逆比になるため、電源変圧器ＴＲ１側の中性点Ｅ１に分流する地絡電流Ｉｇの分流電流Ｉｇ１は、（８）式で求めることができる。

【００１７】
同様にして、バンク変圧器ＴＲ２側の中性点Ｅ２に分流する地絡電流Ｉｇの分流電流Ｉｇ２は、（９）式で求めることができる。

【００１８】
したがって、地絡点Ｐよりバンク変圧器ＴＲ２側の地絡相電流Ｉａ２、および健全相電流Ｉｂ，Ｉｃは分流電流Ｉｇ２の１／３であるので、（１０）式の通りとなる。
Ｉａ２＝Ｉｂ＝Ｉｃ＝Ｅａ／（Ｚ_Ｌ０２＋ｊＸ_ｔ２）・・（１０）
【００１９】
地絡点Ｐよりバンク変圧器ＴＲ２側の地絡相電流Ｉａ２および健全相電流Ｉｂ，Ｉｃは、前記（１０）式で表すことができるが、地絡点Ｐからバンク変圧器ＴＲ２までの線路の零相インピーダンスＺ_Ｌ０２は短距離のため非常に小さく、バンク変圧器ＴＲ２の零相リアクタンスのみを考慮すると、これらの電流は地絡発生前のＡ相対地電圧Ｅａに対し、ほぼ９０°遅れ位相で、バンク変圧器ＴＲ２側から電源変圧器ＴＲ１に向かって流れる電流である。しかし、これらの電流の方向を電源変圧器ＴＲ１側からバンク変圧器ＴＲ２側に向かって流れる方向を‘正’とした場合には、地絡点Ｐよりバンク変圧器ＴＲ２側の地絡相電流Ｉａ２および健全相電流Ｉｂ，Ｉｃは、電源変圧器ＴＲ１側からバンク変圧器ＴＲ２側に向かって流れる、地絡発生前のＡ相対地電圧Ｅａに対しほぼ９０°進み位相の電流と言える。即ち、前出の（１０）式は（１１）式となる。
Ｉａ２＝Ｉｂ＝Ｉｃ＝−Ｅａ／（Ｚ_Ｌ０２＋ｊＸ_ｔ２）・・（１１）
【００２０】
また、地絡点Ｐより電源変圧器ＴＲ１側の地絡相電流Ｉａ１は、分流電流Ｉｇ１と健全相電流Ｉｂ，Ｉｃのベクトル合成電流であるので、（１２）式となる。

（１２）式より、地絡点Ｐより電源変圧器ＴＲ１側の地絡相電流Ｉａ１は、
地絡発生前のＡ相対地電圧に対し、ほぼ９０°遅れ位相の電流である。
【００２１】
図１０（ａ）は、地絡点Ｐより電源変圧器ＴＲ１側の各相電流Ｉａ１，Ｉｂ，Ｉｃと母線電圧Ｖａ，Ｖｂ，Ｖｃの位相関係を示したベクトル図であり、図１０（ｂ）は、地絡点Ｐよりバンク変圧器ＴＲ２側の各相電流Ｉａ２，Ｉｂ，Ｉｃと母線電圧Ｖａ，Ｖｂ，Ｖｃの位相関係を示したベクトル図である。
同図（ａ）に示すように、直接接地方式の変電所の母線で１線地絡が発生した場合には、地絡点Ｐより電源変圧器ＴＲ１側では、地絡相に地絡発生前のＡ相電圧Ｖａに対しほぼ９０°の遅れ電流Ｉａ１が流れ、健全相には地絡発生前のＡ相電圧Ｖａに対しほぼ９０°進み位相の電流Ｉ，Ｉｃが流れる。
また、同図（ｂ）に示すように地絡点Ｐよりバンク変圧器ＴＲ２側では、地絡相および健全相には同じ大きさで地絡発生前のＡ相電圧Ｖａに対しほぼ９０°進み位相の電流Ｉａ２，Ｉｂ，Ｉｃが流れる。
【００２２】
次に、このような直接接地方式の変電所の地絡電流に対する短絡方向継電器の応動について説明する。
図１１は、直接接地方式の変電所の母線において、Ａ相１線地絡が発生した場合に受電線側人形部の短絡方向継電器ＲＹ１とバンク側人形部の短絡方向継電器ＲＹ２とにそれぞれ入力される相電流と母線電圧の位相関係を示したベクトル図と、それらの入力に対する各短絡方向継電器ＲＹ１，ＲＹ２の応動を各相毎に示した図である。なお、受電線側人形部の短絡方向継電器ＲＹ１は、継電器設置点から電源側の事故に対して動作し、バンク側人形部の短絡方向継電器ＲＹ２は継電器設置点からバンク側の事故に対して動作するものであり、同図中に示した短絡方向継電器ＲＹ１，ＲＹ２へのそれぞれの入力電流のベクトル図は、当該継電器ＲＹ１，ＲＹ２の設置点から動作すべき事故点に向かって流れる事故電流の方向を‘正’としたものである。
【００２３】
したがって、受電線側の短絡方向継電器ＲＹ１は人形部から電源側に向かって流れる方向が動作すべき事故電流の方向であり、同図中の当該継電器ＲＹ１の入力電流のベクトル図は人形部から電源側の向かって流れる方向を‘正’としている。よって、前出の図１０（ａ）に示した地絡点Ｐより電源側の電流ベクトルＩａ１，Ｉｂ，Ｉｃとは電流の極性が逆極性になっている。
同図より、受電線側の短絡方向継電器ＲＹ１は各相とも不動作であるが、地絡点が母線であることから、これらの応動は事故点方向を正しく判別した正規応動である。これに対し、バンク変圧器側の短絡方向継電器ＲＹ２は、地絡相であるａ相は不動作であるが、健全相であるｂ相およびｃ相が動作することになり、地絡点が母線であることを考慮すると、当該継電器ＲＹ２の不動作側の事故であるにも関わらず健全相の継電器が不要動作していることになる。
【００２４】
この現象は、前述で説明したように直接接地方式変電所の母線で１線地絡事故が発生した場合の地絡電流は、地絡点よりバンク変圧器側では地絡相、健全相とも同じ大きさで、地絡相電圧Ｖａに対しほぼ９０°進み位相の電流が流れることによるものである。また、これまでＡ相１線地絡の場合について説明してきたが、他相の１線地絡および２線地絡の場合も同様に健全相の継電器が不要動作する現象となる。
したがって、直接接地方式の変電所において、短絡方向継電器によって人形部に流れる短絡電流および地絡電流の方向を判別し、その結果から故障区間を判定する場合、前記のような地絡時の健全相電流によって短絡方向継電器の健全相が不要動作するため、正確な故障区間判定ができないことになる。
【００２５】
また、この問題に対し、短絡方向継電器の動作電流値を高整定にすることで、地絡時の健全相電流では動作しないように対策することは、直接接地系統における地絡電流は短絡電流と同程度に大きく、前記のような地絡時の健全相電流の大きさも数千Ａとなり、当該系統の最小短絡電流と接近した電流値であるため、短絡事故検出性能の低下を招く可能性があり、採用困難である。
【００２６】
本発明は、直接接地方式の変電所の故障区間判定を短絡、地絡とも短絡方向継電器の動作結果から行うこととし、その場合に課題となる前述のような地絡時の健全相電流による誤判定を防止し、正しく故障区間判定できる故障区間判定装置を提供するためになされたものである。
【００２７】
【課題を解決するための手段】
請求項１の発明の故障区間判定装置では、複数の受電線と複数の変圧器バンクと複数の送電線とを接続した２つの母線から成る直接接地方式変電所の前記各受電線、各変圧器バンク、および各送電線のそれぞれの人形部から前記第１の母線に出入りする事故電流の方向を判定する第１の短絡方向継電器群と、前記それぞれの人形部から前記第２の母線に出入りする事故電流の方向を判定する第２の短絡方向継電器群と、前記第１の母線の各線間電圧低下を検出する第１の不足電圧継電器と、前記第１の母線の各相電圧低下を検出する第２の不足電圧継電器と、前記第２の母線の各線間電圧低下を検出する第３の不足電圧継電器と、前記第２の母線の各相電圧低下を検出する第４の不足電圧継電器と、前記第１の不足電圧継電器の各相動作信号と前記第２の不足電圧継電器の各相動作信号とから前記第１の母線の係わる母線事故の事故相を検出し、前記第１の短絡方向継電器群の各相動作信号のうち事故相の動作信号を選択する第１の事故相選択部群と、前記第３の不足電圧継電器の各相動作信号と前記第４の不足電圧継電器の各相動作信号とから前記第２の母線の係わる母線事故の事故相を検出し、前記第２の短絡方向継電器群の各相動作信号のうち事故相の動作信号を選択する第２の事故相選択部群と、前記第１の事故相選択部群の出力と前記第２の事故相選択部群の出力とから母線事故の事故区間を検出する判定部とを備える。
【００２８】
請求項２の発明の故障区間判定装置では、複数の受電線と複数の変圧器バンクと複数の送電線とを接続した２つの母線から成る直接接地方式変電所の前記各受電線、各変圧器バンク、および各送電線のそれぞれの人形部から前記第１の母線に出入りする事故電流の方向を判定する第１の短絡方向継電器群と、前記それぞれの人形部から前記第２の母線に出入りする事故電流の方向を判定する第２の短絡方向継電器群と、前記第１の母線の係わる母線事故の保護を行う各相電流差動方式母線保護継電器の各相動作信号を用いて、前記第１の短絡方向継電器群の各相動作信号のうち事故相の動作信号を選択する第１の事故相選択部群と、前記第２の母線の係わる母線事故の保護を行う各相電流差動方式母線保護継電器の各相動作信号を用いて、前記第２の短絡方向継電器群の各相動作信号のうち事故相の動作信号を選択する第２の事故相選択部群と、前記第１の事故相選択部群の出力と前記第２の事故相選択部群の出力とから母線事故の事故区間を検出する判定部とを備える。
【００２９】
【発明の実施の形態】
図１は請求項１の発明の故障区間判定装置を２つの受電線と２つのバンク変圧器を有する２重母線構成の直接接地方式変電所に適用した場合の実施の形態の一例である。
図１において、１は甲母線、２は乙母線、３，４は第１および第２の受電線、５，６は第１および第２のバンクである。各受電線３，４の送電端の電源変圧器の中性点および各バンク変圧器５，６の中性点は直接接地されている。
【００３０】
各受電線３，４および各バンク５，６は、甲母線１と乙母線２の中央にある人形部と呼ばれる部分からそれぞれの甲母線側断路器３ａ〜６ａ、および乙母線側断路器３ｂ〜６ｂによって、甲母線１および乙母線２の両方に接続できる構造となっているが、通常は甲母線側断路器３ａ〜６ａあるいは乙母線側断路器３ｂ〜６ｂのいずれか一方を閉じ、他方を開くことによって甲母線１あるいは乙母線２のいずれかに選択的に接続されている。図１はその標準的な接続を示し、甲母線１は第１の受電線３から給電され、乙母線２は第２の受電線４から給電されるようになっている。また、第１のバンク５は甲母線１に接続され、第２のバンク６は乙母線２に接続されている。
【００３１】
３ｃ〜６ｃは受電線３，４の人形部およびバンク５，６の人形部の甲母線側断路器３ａ〜６ａの近傍に取り付けた光ＣＴであり、各人形部から甲母線１へ出入する電流を検出するための電流センサである。同様に、３ｄ〜６ｄは受電線３，４の人形部およびバンク５，６の人形部の乙母線側断路器３ｂ〜６ｂの近傍に取り付けた光ＣＴであり、各人形部から乙母線２へ出入りする電流を検出するための電流センサである。また、７は甲母線１の計器用変圧器、８は乙母線２の計器用変圧器である。９は光ＣＴ３ｃ〜６ｃおよび光ＣＴ３ｄ〜６ｄの出力信号を伝達する光ファイバケーブルである。
【００３２】
３ｇ〜６ｇは光ＣＴ３ｃ〜６ｃで検出した電流に応動する短絡方向継電器であり、甲母線１の母線電圧を基準に各人形部の甲母線１側を通過する事故電流の方向を判別する。３ｈ〜６ｈは光ＣＴ３ｄ〜６ｄで検出した電流に応動する短絡方向継電器であり、乙母線２の母線電圧を基準に各人形部の乙母線２側を通過する事故電流の方向を判別する。
【００３３】
１２は甲母線１の各線間電圧の低下を検出する第１の不足電圧継電器であり、１３は甲母線１の各相電圧の低下を検出する第２の不足電圧継電器である。１４は乙母線２のの各線間電圧の低下を検出する第３の不足電圧継電器であり、１５は乙母線２の各相電圧の低下を検出する第４の不足電圧継電器である。
また、３ｉ〜６ｉは第１の不足電圧継電器１２と第２の不足電圧継電器１３の各相動作信号から甲母線１と甲母線１に接続された受電線３、およびバンク５の短絡事故および地絡事故の事故発生相を検出し、短絡方向継電器３ｇ〜６ｇのそれぞれの各相動作信号のうち、事故発生相のみを選択出力する第１の事故相選択部である。
【００３４】
同様に、３ｊ〜６ｊは第３の不足電圧継電器１４と第４の不足電圧継電器１５の各相動作信号から乙母線２と乙母線２に接続された受電線４、およびバンク６の短絡事故および地絡事故の事故発生相を検出し、短絡方向継電器３ｈ〜６ｈのそれぞれの各相動作信号のうち、事故発生相のみを選択出力する第２の事故相選択部である。
１６は第１の事故相選択部３ｉ〜６ｉおよび第２の事故相選択部３ｊ〜６ｊの出力から母線事故の事故区間を自動判定する判定部である。
【００３５】
なお、図１は２つの受電線３，４と２つのバンク５，６を有する２重母線構成の変電所への適用例であるが、受電線数およびバンク数の増減に対しては、その数に対応した前記光ＣＴ、短絡方向継電器、事故相選択部を有する構成とすることで対応できる。また、図１は各人形部から甲母線１および乙母線２に出入りする電流を検出する電流センサに光ＣＴを適用した事例であるが、本発明による故障区間判定装置では計器用変流器などの電流センサの適用も可能である。
【００３６】
ここで、第１の不足電圧継電器１２と第２の不足電圧継電器１３の作用について説明する。
図３は３相短絡、ＢＣ相２相短絡、Ａ相１線地絡、およびＢＣ相２線地絡の場合を例に母線事故時の母線電圧のベクトル表示とその時の第１の不足電圧継電器１２と第２の不足電圧継電器１３の応動を示すものである。なお、同図中の数字は事故点抵抗を零とした完全短絡、完全地絡の場合の母線電圧の各線間電圧値および各相電圧値（計器用変圧器７の２次電圧換算）である。なお、各母線事故様相に対する第１および第２の不足電圧継電器１２，１３の応動を説明する上での各不足電圧継電器１２，１３の検出感度は、その適用の一例として事故様相の５０％検出を目途に第１の不足電圧継電器１２は５５Ｖ、第２の不足電圧継電器１３は３２Ｖにしたものである。
【００３７】
同図より、３相短絡が発生すると、Ａ−Ｂ線間電圧、Ｂ−Ｃ線間電圧、Ｃ−Ａ線間電圧が共に殆ど零に低下し、２相短絡の場合には、短絡発生相の線間電圧が殆ど零に低下する。したがって、線間電圧の低下を検出する第１の不足電圧継電器１２の動作相から短絡相を検出することができる。また、１線地絡が発生した場合には、地絡相の相電圧が殆ど零になるのに対し、健全相の相電圧は殆ど変化しない。よって、相電圧の低下を検出する第２の不足電圧継電器１３の動作相から地絡相を検出することができる。また、２線地絡は２相が大地を経由して短絡することであり、事故相の線間電圧は殆ど零となると共に、相電圧も殆ど零になるため、第１の不足電圧継電器１２および第２の不足電圧継電器１３が共に動作することになり、それらの動作相から事故相を検出できる。
【００３８】
このように、甲母線１の線間電圧の低下を検出する第１の不足電圧継電器１２と相電圧の低下を検出する第２の不足電圧継電器１３の動作相から、甲母線１および甲母線１に接続された受電線３、バンク５の短絡事故および地絡事故の事故相を検出することができる。なお、第３の不足電圧継電器１４と第４の不足電圧継電器１５の作用についても同様であり、それらの動作相から乙母線２および乙母線２に接続された受電線４、バンク６の短絡事故および地絡事故の事故相を検出できる。
【００３９】
次に、第１の事故相選択部３ｉの作用について説明する。
図４は、第１の事故相選択部３ｉの具体的な構成の一例である。
事故相選択部３ｉは第１の不足電圧継電器１２のＡＢ相、ＢＣ相、ＣＡ相の各線間電圧の低下に対するそれぞれの動作信号からＯＲゲート２０ａ、２０ｂ、２０ｃによって短絡相を検出し、更に、ＯＲゲート２１ａ、２１ｂ、２１ｃによって、第２の不足電圧継電器１３のＡ相、Ｂ相およびＣ相の各相電圧の低下に対するそれぞれの動作信号との論理和をとることによって、甲母線１および甲母線１に接続された受電線３やバンク５の短絡および地絡の事故相を検出する。
【００４０】
更に、ＡＮＤゲート２２ａ、２２ｂ、２２ｃによって、これらの事故相条件と前記短絡方向継電器３ｇのＡ相、Ｂ相、Ｃ相の各相電流の方向判定結果である各相の動作信号との論理積を取り、その結果をＯＲゲート２３で集約することで、短絡方向継電器３ｇの各相動作信号のうち事故相のみを選択し、当該人形部の甲母線１側を通過する事故電流の方向判定結果として、判定部１６に出力することができる。
【００４１】
他の第１の事故相選択部４ｉ〜６ｉも同様に、対応するそれぞれの短絡方向継電器４ｇ〜６ｇの各相動作信号のうち事故相のみを選択出力することができる。
また、第２の事故相選択部３ｊ〜６ｊは、第３の不足電圧継電器１４および第４の不足電圧継電器１５の動作信号から短絡方向継電器３ｈ〜６ｈの各相動作信号から事故相のみを選択出力するもので、第１の事故相選択部３ｉ〜６ｉの作用を乙母線２側に置き換えたものである。
【００４２】
このような第１の事故相選択部３ｉ〜６ｉおよび第２の事故相選択部３ｊ〜６ｊの作用によって、判定部１６では、各人形部における事故相のみの方向判定結果を基に故障区間判定を行うことが可能となり、直接接地方式の変電所における地絡事故時の方向継電器の健全相側不要動作による故障区間の誤判定を防止することができる。
【００４３】
次に、請求項２の発明の実施の形態の一例について説明する。
図２は請求項２の発明の故障区間判定装置を２つの受電線と２つのバンク変圧器を有する２重母線構成の直接接地方式変電所に適用した場合の実施の形態の一例である。
図２において、１７は甲母線１側の母線保護継電器の各相毎の動作信号、１８は乙母線２側の母線保護継電器の各相毎の動作信号である。また、３ｋ〜６ｋは甲母線１側の母線保護継電器の動作信号１７から短絡方向継電器３ｇ〜６ｇの各相動作信号のうち、事故発生相のみを選択出力する第１の事故相選択部である。同様に、３ｌ〜６ｌは乙母線２側の母線保護継電器の動作信号１８から短絡方向継電器３ｈ〜６ｈの各相動作信号のうち、事故発生相のみを選択出力する第２の事故相選択部である。また、他の構成は図１と同様に構成されているので、同一部分には同一符号を付して、その重複する説明を省略する。
【００４４】
ここで通常直接接地方式変電所の母線保護に適用される電流差動方式の母線保護継電器の動作について説明する。
常時および外部事故時には母線への流入電流は必ず流出電流となるので母線に接続された各受電線、各バンクから母線に出入りする電流をベクトル加算した合計は差し引き零となる。しかし、母線事故時には事故電流が流入するが、通常流出電流はないので、この合計は零とならない。このことから、母線保護継電器は母線に接続された各受電線および各バンクから母線に出入りする電流を各相毎にベクトル加算し、その合計を監視することで母線の内部・外部事故の判別を行うものである。
【００４５】
このように、電流差動方式の母線保護継電器は母線に接続された各受電線および各バンクから母線に出入りする電流を各相毎にベクトル加算し、その合計が所定の値を越えた場合に動作するよう構成されているので、短絡事故や地絡事故で事故相に事故電流が流入すると、その事故電流を検出し事故相の母線保護継電器が動作する。しかし、前述で説明した直接接地方式変電所の地絡事故において、直接接地された各バンク変圧器の中性点を通して健全相側に流れる地絡電流は母線を通過し電源変圧器まで流れるため、流入電流＝流出電流となり差し引き零となるため、健全相の母線保護継電器が不要動作することは無い。
【００４６】
図５は直接接地方式変電所の母線事故様相と電流差動方式の母線保護継電器の各相動作信号の関係を示したものである。同図より、３相短絡の場合には母線保護継電器は３相共動作し、２相短絡および２線地絡の場合にはその事故相である２相が動作する。また、１線地絡の場合には、母線保護継電器は事故相のみの１相が動作することになる。
このように、電流差動方式の母線保護継電器の動作相は母線事故の事故相を一致しており、即ち、電流差動方式の母線保護継電器の動作相から母線事故の事故相を判断することができる。
【００４７】
このことから、第１の事故相選択部３ｋは甲母線１側の母線保護継電器の各相動作信号１７から短絡方向継電器３ｇの各相動作信号のうち事故相のみを選択出力ものであり、図６は、第１の事故相選択部３ｋの具体的な構成の一例である。
母線保護継電器１７の動作相は母線事故の事故相と一致しているので、ＡＮＤゲート２４ａ、２４ｂ、２４ｃによって母線保護継電器の各相動作信号と短絡方向継電器３ｇのＡ相、Ｂ相、Ｃ相の各相電流の方向判定結果である各相の動作信号との論理積を取り、その結果をＯＲゲート２５で集約することで、短絡方向継電器３ｇの各相動作信号のうち事故相のみを選択し、当該人形部の甲母線１側を通過する事故電流の方向判定結果として、判定部１６に出力することができる。
【００４８】
また、他の第１の事故相選択部４ｋ〜６ｋも同様に、対応する短絡方向継電器４ｇ〜６ｇの各相動作信号のうち事故相のみを選択出力するものである。また、第２の事故相選択部３ｌ〜６ｌは乙母線２側の母線保護継電器の各相動作信号１８から対応する短絡方向継電器３ｊ〜６ｊの各相動作信号のうち事故相のみを選択出力するものである。
このような第１の事故相選択部３ｋ〜６ｋおよび第２の事故相選択部３ｌ〜６ｌの作用によって、判定部１６では、各人形部における事故相のみの方向判定結果を基に故障区間判定を行うことが可能となり、直接接地方式変電所における地絡事故時の方向継電器の健全相側不要動作による故障区間の誤判定を防止することができる。
【００４９】
【発明の効果】
以上に説明したように、この発明によれば、直接接地方式の変電所における地絡時の健全相の方向継電器の不要動作の影響を受けないため、正確に故障区間判定ができる。
【図面の簡単な説明】
【図１】請求項１の発明の故障区間判定装置の実施の形態の一例を示す説明図である。
【図２】請求項２の発明の故障区間判定装置の実施の形態の一例を示す説明図である。
【図３】請求項１の発明の不足電圧継電器の動作を示す説明図である。
【図４】請求項１の発明の事故相選択部の具体的な構成の一例の説明図である。
【図５】請求項２の発明に関わる母線保護継電器の動作を示す説明図である。
【図６】請求項２の発明の事故相選択部の具体的な構成の一例の説明図である。
【図７】方向継電器の動作特性図である。
【図８】直接接地系統の地絡電流の方向の説明図である。
【図９】直接接地系統の零相回路である。
【図１０】直接接地系統の１線地絡時の電流・電圧ベクトル図である。
【図１１】直接接地系統の１線地絡時の短絡方向継電器の応動の説明図である。
【図１２】従来の故障区間判定装置の説明図である。
【符号の説明】
１，２母線
３，４受電線
５，６変圧器バンク
７，８計器用変圧器
３ｇ〜６ｇ，３ｈ〜６ｈ方向継電器
３ｉ〜６ｉ，３ｊ〜６ｊ請求項１の発明の事故相選択部
３ｋ〜６ｋ，３ｌ〜６ｌ請求項２の発明の事故相選択部
１２，１３，１４，１５不足電圧継電器
１６判定部
１７，１８母線保護継電器の動作信号[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a substation fault zone determination device that can automatically detect a fault zone when a ground fault or short circuit accident occurs inside a power transmission substation.
[0002]
[Prior art]
An apparatus for detecting a failure section of a double-bus power transmission substation is described in, for example, Japanese Patent Application Laid-Open No. 2-223334. FIG. 12 shows an example of a conventional substation failure section detection system.
In FIG. 12, reference numeral 1 denotes a first bus (hereinafter, referred to as an instep bus), 2 denotes a second bus (hereinafter, referred to as an auxiliary bus), and 5, 6 denote first and second transformer banks ( Hereinafter, banks will be used.) Reference numerals 10 and 11 denote first and second load lines. Each of the

banks

5 and 6 and each of the load lines 10 and 11 are separated from a part called a doll section at the center of the instep bus 1 and the instep bus 2 to the instep bus side disconnectors 3a to 6a and the instep bus side disconnectors 3b to 3b. 6b, it is configured to be connectable to both the instep bus 1 and the inversion bus 2, but usually one of the instep bus side disconnectors 3a to 6a or the inversion bus side disconnectors 3b to 6b is closed, and the other is closed. By being opened, it is selectively connected to either the instep bus 1 or the inversion bus 2. FIG. 12 shows the standard connection, in which the instep bus 1 is supplied with power from the first bank 5 and the second bus 2 is supplied with power from the second bank 6. Further, the first load line 10 is connected to the instep bus 1, and the second load line 11 is connected to the second bus 2.
[0003]
Reference numerals 3c to 6c denote optical CTs attached to the doll parts of the

banks

5 and 6 and the doll parts of the load lines 10 and 11 in the vicinity of the instep bus-side disconnectors 3a to 6a, respectively. It is a current sensor for detecting a current. Similarly, reference numerals 3d to 6d denote optical CTs attached to the doll portions of the

banks

5 and 6 and the doll portions of the load lines 10 and 11 in the vicinity of the maiden line disconnectors 3b to 6b, respectively. It is a current sensor for detecting a current flowing into and out of the device. Reference numeral 7 denotes an instrument transformer of the instep bus 1, and reference numeral 8 denotes an instrument transformer of the maiden bus 2. Reference numeral 9 denotes an optical fiber cable for transmitting output signals of the optical CTs 3c to 6c and the optical CTs 3d to 6d.
[0004]
Reference numerals 3g to 6g denote directional relays that respond to the currents detected by the light CTs 3c to 6c, and determine the direction of the fault current passing through the instep bus 1 side of each doll section with reference to the bus voltage of the instep bus 1. Reference numerals 3h to 6h denote directional relays that respond to the currents detected by the light CTs 3d to 6d, and determine the direction of the fault current passing through the doll bus 2 side of each doll section with reference to the bus voltage of the doll bus 2.
As described above, each bank-side doll section of the substation in which the plurality of

banks

5, 6 and the plurality of load lines 10, 11 are connected to the two

buses

1, 2 and the bus disconnectors 3a to 6a, In the vicinity of 3b to 6b, light CTs 3c to 6c and 3d to 6d are attached, and directional relays 3g to 6g and 3h to 6h that can detect the direction of the fault current from the light CTs 3c to 6c and 3d to 6d are provided. The fault current at the time of occurrence is detected by the light CTs 3c to 6c and 3d to 6d, the direction of the fault current flowing is determined by the direction relays 3g to 6g and 3h to 6h from the current, and the result is input to the determination unit 16. The section where the accident occurred was automatically detected.
[0005]
Here, the directional relays 3g to 6g and 3h to 6h for determining the direction in which the fault current flows from the light CTs 3c to 6c and 3d to 6d in the above-described conventional fault section determination device will be described.
As the direction relays 3g to 6g and 3h to 6h of the conventional failure section determination device, a short-circuit direction relay is used to determine the direction of the short-circuit current, and a ground-fault direction relay is used to determine the direction of the ground fault current.
[0006]
FIG. 7 shows an example of the operation characteristics of the short-circuit direction relay and the ground fault direction relay. The short-circuit direction relay RY is a relay that operates when the phase difference of the phase current I is within a predetermined range based on the line voltage V, as shown in FIG. For example, in the case of a 90 ° lead connection system, the A-phase current is based on the BC line voltage, the B-phase current is based on the CA line voltage, and the C-phase current is based on the AB line voltage. And a relay for determining the direction of the short-circuit current as viewed from the relay installation point, that is, the direction of the short-circuit fault occurrence point, from the OR point of the phase difference determination for each of the three phases. It is.
Similarly, the ground fault direction relay RY is a relay that operates when the phase difference of the zero-phase current Io is within a predetermined range based on the zero-phase voltage Vo, as shown in FIG. The relay determines the direction of the observed ground fault current, that is, the direction of the ground fault occurrence point.
[0007]
[Problems to be solved by the invention]
Next, a problem in a case where the above-described conventional substation failure section determination device is applied to a substation of a direct grounding type will be described.
In a substation of the direct grounding system, the neutral point of the power transformer and the bank transformer at the transmission end of each receiving line is directly grounded, so the zero-phase impedance is small. Although the fault current becomes as large as that of the above, almost no zero-sequence voltage is generated.
Therefore, in a ground fault directional relay that determines the direction of the ground fault current based on the zero-sequence voltage, it is difficult to determine the direction of the ground fault current because a sufficient reference zero-phase voltage cannot be obtained. That is, the conventional substation failure section determination device has a problem that it is difficult to determine a failure section at the time of a ground fault in a substation of the direct grounding type.
[0008]
To cope with this problem, utilizing the fact that the ground fault current becomes a very large current of the same order as the short-circuit current, the direction of the ground fault current is also determined by the above-described short-circuit direction relay in the same manner as the short-circuit current direction. However, in the event of a ground fault at the bus of a substation of the direct grounding type, not only the ground fault phase but also the sound phase where no ground fault occurs through the neutral point of the directly grounded bank transformer Since the ground fault current is divided and flows, there is a problem that the phase difference determination on the sound phase side of the short-circuit direction relay operates unnecessarily.
[0009]
In the following, a description will be given of a ground fault current flowing in a ground fault phase and a healthy phase when a ground fault occurs in a substation of a direct grounding method, and how a short-circuit direction relay responds to the ground fault current.
FIG. 8 shows the direction in which the ground fault current Ig flows, taking as an example a case where an A-phase one-line ground fault occurs in the direct grounding system. As shown in the figure, in the direct grounding system, since the neutral points E1 and E2 of the power transformer TR1 and the bank transformer TR2 are both directly grounded, the ground fault current Ig is changed to the neutral point E1 of the power transformer TR1. And flows toward the neutral point E2 of the bank transformer TR2, and flows into the system from the neutral points E1 and E2. This shunt ratio is the inverse ratio of the zero-phase impedance on the power supply side viewed from the ground fault point P and the zero-phase impedance viewed on the bank side.
[0010]
The shunt portion Ig2 of the ground fault current flowing into the system from the neutral point E2 of the bank transformer TR2 is further shunted to each phase coil of the bank transformer TR2 by 1/3, and the bank transformer TR2 side from the ground fault point P. And the B-phase current Ib and the C-phase current Ic (hereinafter referred to as healthy phase currents Ib and Ic), which are the phase currents of the healthy phase where no ground fault occurs. The ground fault phase current Ia2 flows to the ground fault point P, and the sound phase currents Ib and Ic pass through the b-phase and c-phase coils of the power transformer TR1 and flow from the neutral point E1 of the power transformer TR1. The other ground current Ig is combined with the divided current Ig1 of the other ground fault current Ig to become a ground fault phase current Ia1 on the power transformer TR1 side from the ground fault point P, and the ground fault point P1 via the a-phase coil of the power transformer TR1. Flows up to
[0011]
The one-line ground-fault current Ig of such a direct grounding system can be obtained by the symmetric coordinate method as shown in Expression (1).
Ig = 3Ea / (Z ₀ + Z ₁ + Z ₂ ・・・・・・・・・ (1)
Here, Ea is the ground voltage at the ground fault point before the occurrence of the ground fault.
Z ₀ = Zero-phase impedance of the whole system viewed from the ground fault point
Z ₁ = Positive phase impedance of the whole system from the ground fault point
Z ₂ = Reverse-phase impedance of the entire system as seen from the ground fault point
[0012]
FIG. 9 shows a zero-phase circuit of a direct grounding system. From the figure, the zero-phase impedance Z of the whole system viewed from the ground fault point P ₀ Is the zero-phase impedance Z on the power transformer TR1 side from the ground fault point P. ₀₁ And zero-phase impedance Z on the bank transformer TR2 side from ground fault point P ₀₂ , It can be expressed as in equation (2).
Z ₀ = Z ₀₁ ・ Z ₀₂ / (Z ₀₁ + Z ₀₂ ・・・・・ (2)
Where Z ₀₁ = Zero-phase impedance from the ground fault point P to the power transformer TR1
Z ₀₂ = Zero-phase impedance from ground fault point P to bank transformer TR2
[0013]
Further, the zero-phase impedance Z on the power transformer TR1 side from the ground fault point P. ₀₁ And zero-phase impedance Z on the bank transformer TR2 side from ground fault point P ₀₂ Are the equations (3) and (4).
Z ₀₁ = Z _L01 + JX _t1 ... (3)
Z ₀₂ = Z _L02 + JX _t2 ... (4)
Where Z _L01 = Of the line from the ground fault point P to the power transformer TR1
Zero-phase impedance
Z _L02 = Of the line from the ground fault point P to the bank transformer TR2
Zero-phase impedance
X _t1 = Zero-phase impedance (reactance) of power transformer TR1
X _t2 = Zero-phase impedance (reactance) of bank transformer TR2
[0014]
Similarly, the positive impedance Z of the entire system viewed from the ground fault point P ₁ And anti-phase impedance Z ₂ , The positive and negative phase impedances Z from the ground fault point P to the power transformer TR1 side. ₁₁ , Z ₂₁ And negative phase impedance Z on the bank transformer TR2 side from the ground fault point P ₁₂ , Z ₂₂ , And can be expressed as in equations (5) and (6).
Z ₁ = Z ₁₁ ・ Z ₁₂ / (Z ₁₁ + Z ₁₂ ・・・・・ (5)
Z ₂ = Z ₂₁ ・ Z ₂₂ / (Z ₂₁ + Z ₂₂ ) ・・・・・ (6)
Where Z ₁₁ = Positive phase impedance from the ground fault point P to the power transformer TR1 side
Z ₂₁ = Reverse-phase impedance from the ground fault point P to the power transformer TR1
Z ₁₂ = Positive phase impedance from the ground fault point P to the bank transformer TR2 side
Z ₂₂ = Reverse-phase impedance from ground fault point P to bank transformer TR2 side
[0015]
Here, for simplicity of calculation, the positive-phase impedance Z of the entire system viewed from the ground fault point P is shown. ₁ And the negative impedance Z of the whole system viewed from the ground fault point P ₂ Is ignored because it is small, the equation (2) is substituted into the equation (1), and the ground fault current Ig can be obtained as shown in the equation (7).

[0016]
Further, the ground fault current shunted to the neutral points E1 and E2 of the power transformer TR1 and the bank transformer TR2 is a zero-phase impedance Z when the power transformer TR1 side is viewed from the ground fault point P. ₀₁ And zero-phase impedance Z looking at bank transformer TR2 side from ground fault point P ₀₂ Therefore, the shunt current Ig1 of the ground fault current Ig shunted to the neutral point E1 on the side of the power transformer TR1 can be obtained by Expression (8).

[0017]
Similarly, the shunt current Ig2 of the ground fault current Ig shunting to the neutral point E2 on the side of the bank transformer TR2 can be obtained by equation (9).

[0018]
Therefore, since the ground fault phase current Ia2 and the healthy phase currents Ib and Ic on the bank transformer TR2 side from the ground fault point P are １／ of the shunt current Ig2, the equation (10) is obtained.
Ia2 = Ib = Ic = Ea / (Z _L02 + JX _t2 ) ・・ (10)
[0019]
The ground fault phase current Ia2 and the sound phase currents Ib and Ic on the bank transformer TR2 side from the ground fault point P can be expressed by the above equation (10), but the line from the ground fault point P to the bank transformer TR2 is Zero-phase impedance Z _L02 Is very small due to the short distance, and considering only the zero-phase reactance of the bank transformer TR2, these currents are approximately 90 ° delayed from the A relative ground voltage Ea before the ground fault occurs, and the bank transformer TR2 This is a current flowing from the side toward the power transformer TR1. However, when the direction of these currents is "positive" from the power transformer TR1 toward the bank transformer TR2, the ground fault phase current Ia2 on the bank transformer TR2 side from the ground fault point P is considered. The sound phase currents Ib and Ic can be said to be currents which flow from the power transformer TR1 toward the bank transformer TR2 and have a phase leading by approximately 90 ° with respect to the A relative ground voltage Ea before the occurrence of the ground fault. That is, the equation (10) becomes the equation (11).
Ia2 = Ib = Ic = −Ea / (Z _L02 + JX _t2 ) ・・ (11)
[0020]
Further, since the ground fault phase current Ia1 on the power transformer TR1 side from the ground fault point P is a vector composite current of the shunt current Ig1 and the healthy phase currents Ib and Ic, the equation (12) is obtained.

From equation (12), the ground fault phase current Ia1 on the power transformer TR1 side from the ground fault point P is
This is a current having a phase delayed by about 90 ° with respect to the A relative ground voltage before the occurrence of the ground fault.
[0021]
FIG. 10A is a vector diagram showing a phase relationship between the respective phase currents Ia1, Ib, Ic and the bus voltages Va, Vb, Vc on the power transformer TR1 side from the ground fault point P, and FIG. Is a vector diagram showing a phase relationship between each phase current Ia2, Ib, Ic on the bank transformer TR2 side from the ground fault point P and bus voltages Va, Vb, Vc.
As shown in FIG. 3A, when a single-ground fault occurs in the bus of a substation of the direct grounding type, the ground fault occurs before a ground fault occurs on the power transformer TR1 side from the ground fault point P. Lag current Ia1 of approximately 90 ° flows with respect to the A-phase voltage Va, and currents I and Ic with phases approximately 90 ° ahead of the A-phase voltage Va before the occurrence of ground fault flow in the healthy phase.
Further, as shown in FIG. 3B, on the bank transformer TR2 side from the ground fault point P, the ground fault phase and the sound phase have the same magnitude and lead by approximately 90 ° with respect to the A-phase voltage Va before the occurrence of the ground fault. Phase currents Ia2, Ib, and Ic flow.
[0022]
Next, the response of the short-circuit direction relay to the ground fault current of the substation of the direct grounding type will be described.
FIG. 11 shows a case where an A-phase 1-line ground fault occurs in a bus of a substation of a direct grounding system and is input to the short-circuit direction relay RY1 of the doll section on the receiving line side and the short-circuit direction relay RY2 of the doll section on the bank side. FIG. 4 is a vector diagram showing a phase relationship between a phase current and a bus voltage, and a diagram showing a response of each of the short-circuit direction relays RY1 and RY2 to the input for each phase. In addition, the short-circuit direction relay RY1 of the doll part on the receiving wire side operates for an accident on the power supply side from the relay installation point, and the short-circuit direction relay RY2 of the doll part on the bank side operates for the accident on the bank side from the relay installation point. The vector diagrams of the respective input currents to the short-circuit direction relays RY1 and RY2 shown in the figure show the direction of the fault current flowing from the installation point of the relays RY1 and RY2 to the fault point to be operated. Is 'positive'.
[0023]
Therefore, the short-circuit direction relay RY1 on the receiving wire side is the direction of the fault current to be operated when flowing from the doll section toward the power supply side, and the vector diagram of the input current of the relay RY1 in FIG. The direction flowing toward the side is defined as 'positive'. Therefore, the polarity of the current is opposite to that of the current vectors Ia1, Ib, and Ic on the power supply side from the ground fault point P shown in FIG.
As shown in the figure, the short-circuit direction relay RY1 on the receiving line side does not operate in each phase, but since the ground fault point is the bus, these responses are normal responses that correctly discriminate the direction of the fault point. On the other hand, in the short-circuit direction relay RY2 on the side of the bank transformer, the a-phase which is a ground fault phase is inactive, but the b-phase and the c-phase which are sound phases operate, and the ground fault point is a bus line. Considering that, the relay of the healthy phase is operating unnecessarily despite the accident on the non-operation side of the relay RY2.
[0024]
As described above, the ground fault current when a one-line ground fault occurs at the bus of the direct grounding substation is the same for both the ground fault phase and the sound phase on the bank transformer side from the ground fault point. This is due to the fact that a current having a phase leading by approximately 90 ° with respect to the ground fault phase voltage Va flows. Although the case of the A-phase single-line ground fault has been described so far, the case of the other-phase one-line ground fault and the two-line ground fault also causes a phenomenon in which the healthy-phase relay operates unnecessarily.
Therefore, in a substation of the direct grounding type, when the direction of the short-circuit current and the ground fault current flowing in the doll section is determined by the short-circuit direction relay, and the fault section is determined from the result, the sound phase at the time of the ground fault described above is determined. Since the healthy phase of the short-circuit direction relay operates unnecessarily due to the current, accurate fault section determination cannot be performed.
[0025]
In order to avoid this problem, by setting the operating current value of the short-circuit direction relay to a high setting so that it does not operate with the normal phase current at the time of ground fault, the ground fault current in the direct grounding system is the short-circuit current. As large as the above, the magnitude of the sound phase current at the time of the ground fault as described above is also several thousand A, and since the current value is close to the minimum short-circuit current of the system, there is a possibility that the short-circuit fault detection performance may be reduced. Yes, it is difficult to adopt.
[0026]
According to the present invention, the fault section of the substation of the direct grounding system is determined based on the operation result of the short-circuit direction relay for both the short-circuit and the ground fault. The purpose of the present invention is to provide a failure section determination device that prevents the determination and can correctly determine the failure section.
[0027]
[Means for Solving the Problems]
In the fault section determination device according to the first aspect of the present invention, each of the receiving lines and each transformer of the direct grounding type substation comprising two buses connecting a plurality of receiving lines, a plurality of transformer banks, and a plurality of transmission lines. A first group of short-circuit direction relays for determining the direction of the fault current flowing into and out of the first bus from each of the dolls of the bank and each transmission line; and entering and exiting the second bus from each of the dolls. A second group of short-circuit direction relays for determining the direction of the fault current, a first undervoltage relay for detecting a voltage drop between the first buses, and a phase voltage drop for each of the first buses are detected. A second undervoltage relay, a third undervoltage relay that detects each line voltage drop of the second bus, and a fourth undervoltage relay that detects each phase voltage drop of the second bus, Each phase operation signal of the first undervoltage relay An accident phase of a bus fault involving the first bus is detected from each phase operation signal of the second undervoltage relay, and an operation signal of an accident phase among the phase operation signals of the first short-circuit direction relay group is detected. A first fault phase selecting unit group for selecting a bus fault of the second bus bar based on each phase operation signal of the third undervoltage relay and each phase operation signal of the fourth undervoltage relay. A second fault phase selection unit group for detecting a fault phase and selecting a fault phase operation signal among the phase operation signals of the second short-circuit direction relay group, and an output of the first fault phase selection unit group And a determination unit for detecting an accident section of the bus accident from the output of the second accident phase selection unit group.
[0028]
In the failure section determination device according to the second aspect of the present invention, each of the receiving lines and each transformer of the direct grounding type substation comprising two buses connecting a plurality of receiving lines, a plurality of transformer banks, and a plurality of transmission lines. A first group of short-circuit direction relays for determining the direction of the fault current flowing into and out of the first bus from each of the dolls of the bank and each transmission line; and entering and exiting the second bus from each of the dolls. The first short-circuit direction relay group for determining the direction of the fault current and the phase operation signals of the phase current differential type bus protection relays for protecting the bus fault related to the first bus are used for the first short-circuit direction. A first fault phase selection unit group for selecting a fault phase operation signal among the phase operation signals of the short-circuit direction relay group, and a phase current differential bus for protecting a bus fault involving the second bus. Using each phase operation signal of the protection relay, A second fault phase selector for selecting a fault phase operation signal among the respective phase operation signals of the second short-circuit direction relay group; an output of the first fault phase selector and a second fault phase; A determination unit that detects an accident section of the bus accident from the output of the selection unit group.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows an example of an embodiment in which the fault zone judging device according to the first aspect of the present invention is applied to a direct grounding type substation having a double bus configuration having two receiving lines and two bank transformers.
In FIG. 1, reference numeral 1 denotes the instep bus, 2 denotes the second bus, 3, 4 denotes the first and second receiving wires, and 5, 6 denote the first and second banks. The neutral points of the power transformers at the transmitting ends of the

receiving lines

3 and 4 and the neutral points of the

bank transformers

5 and 6 are directly grounded.
[0030]
Each of the receiving

wires

3 and 4 and each of the

banks

5 and 6 are separated from a portion called a doll portion at the center of the instep bus 1 and the instep bus 2 to the instep bus side disconnectors 3a to 6a and the instep bus side disconnectors 3b to 3b. 6b, it is configured to be connectable to both the instep bus 1 and the inversion bus 2, but usually one of the instep bus side disconnectors 3a to 6a or the inversion bus side disconnectors 3b to 6b is closed, and the other is closed. By being opened, it is selectively connected to either the instep bus 1 or the instep bus 2. FIG. 1 shows the standard connection, in which the instep bus 1 is supplied with power from a first receiving line 3 and the second bus 2 is supplied with power from a second receiving line 4. The first bank 5 is connected to the instep bus 1, and the second bank 6 is connected to the second bus 2.
[0031]
Reference numerals 3c to 6c denote optical CTs attached to the doll parts of the receiving

wires

3 and 4 and the doll parts of the

banks

5 and 6 near the instep bus-side disconnectors 3a to 6a. Is a current sensor for detecting. Similarly, reference numerals 3d to 6d denote optical CTs mounted near the doll parts of the receiving

wires

3 and 4 and the doll parts of the

banks

5 and 6 near the maiden line-side disconnectors 3b to 6b. It is a current sensor for detecting a current flowing in and out. Reference numeral 7 denotes an instrument transformer of the instep bus 1, and reference numeral 8 denotes an instrument transformer of the maiden bus 2. Reference numeral 9 denotes an optical fiber cable for transmitting output signals of the optical CTs 3c to 6c and the optical CTs 3d to 6d.
[0032]
Reference numerals 3g to 6g denote short-circuit direction relays that respond to the currents detected by the light CTs 3c to 6c, and determine the direction of an accident current passing through the instep bus 1 side of each doll section based on the in-line bus voltage. Reference numerals 3h to 6h denote short-circuit direction relays that respond to the currents detected by the light CTs 3d to 6d, and determine the direction of the fault current passing through the doll bus 2 side of each doll section based on the bus voltage of the doll bus 2.
[0033]
Reference numeral 12 denotes a first undervoltage relay that detects a drop in the line voltage of the instep bus 1, and reference numeral 13 denotes a second undervoltage relay that detects a drop in the phase voltage of the instep bus 1. Reference numeral 14 denotes a third undervoltage relay that detects a drop in the line voltage of the maiden bus 2, and reference numeral 15 denotes a fourth undervoltage relay that detects a drop in the phase voltage of the maiden bus 2.
In addition, 3i to 6i are based on the respective phase operation signals of the first undervoltage relay 12 and the second undervoltage relay 13, and the short-circuit accident and ground of the instep bus 1 and the receiving line 3 connected to the instep bus 1 and the bank 5 This is a first fault phase selection unit that detects the fault occurrence phase of a fault and selects and outputs only the fault occurrence phase among the respective phase operation signals of the short-circuit direction relays 3g to 6g.
[0034]
Similarly, 3j to 6j indicate the short-circuit accidents of the sub-bus 2 and the receiving line 4 connected to the sub-bus 2 and the bank 6 from the respective phase operation signals of the third under-voltage relay 14 and the fourth under-voltage relay 15. A second fault phase selector that detects the fault occurrence phase of the ground fault and selects and outputs only the fault occurrence phase among the respective phase operation signals of the short-circuit direction relays 3h to 6h.
Reference numeral 16 denotes a determination unit for automatically determining an accident section of a bus accident from the outputs of the first accident phase selection units 3i to 6i and the second accident phase selection units 3j to 6j.
[0035]
FIG. 1 shows an example of application to a substation having a double-bus configuration having two

receiving lines

3 and 4 and two

banks

5 and 6. This can be dealt with by providing a configuration having the optical CTs, the short-circuit direction relays, and the fault phase selection units corresponding to the numbers. FIG. 1 shows an example in which optical CT is applied to a current sensor for detecting a current flowing into and out of each of the doll parts to the instep bus 1 and the inversion bus 2. In the failure section determination device according to the present invention, a current transformer for an instrument or the like is used. Application of the current sensor described above is also possible.
[0036]
Here, the operation of the first undervoltage relay 12 and the second undervoltage relay 13 will be described.
FIG. 3 shows, as an example, a three-phase short-circuit, a BC-phase two-phase short-circuit, an A-phase one-wire ground fault, and a BC-phase two-wire ground fault. 12 shows the response of the second undervoltage relay 12 and the second undervoltage relay 13. The figures in the figure are the line voltage values and the phase voltage values (converted to the secondary voltage of the transformer 7 for the instrument) of the bus voltage in the case of a complete short circuit or a complete ground fault with the fault point resistance set to zero. . Note that the detection sensitivity of each of the undervoltage relays 12 and 13 for explaining the response of the first and second undervoltage relays 12 and 13 to each bus accident mode is, for example, 50% detection of the accident mode. The first undervoltage relay 12 is set to 55V, and the second undervoltage relay 13 is set to 32V.
[0037]
As shown in the figure, when a three-phase short circuit occurs, the voltage between the A-B line, the voltage between the B-C line, and the voltage between the C-A lines all decrease to almost zero. Is almost zero. Therefore, a short-circuit phase can be detected from the operating phase of the first undervoltage relay 12 that detects a drop in line voltage. When a one-line ground fault occurs, the phase voltage of the ground fault phase becomes almost zero, whereas the phase voltage of the sound phase hardly changes. Therefore, a ground fault phase can be detected from the operating phase of the second undervoltage relay 13 that detects a decrease in phase voltage. A two-wire ground fault is a short-circuit between two phases via the ground. The line voltage in the accident phase becomes almost zero and the phase voltage also becomes almost zero. The second undervoltage relay 13 and the second undervoltage relay 13 operate together, and an accident phase can be detected from their operation phases.
[0038]
As described above, from the operating phases of the first undervoltage relay 12 for detecting a decrease in the line voltage of the instep bus 1 and the second undervoltage relay 13 for detecting a drop in the phase voltage, the instep bus 1 and the instep 1 In this case, an accident phase of a short circuit accident and a ground fault accident of the receiving line 3 and the bank 5 connected to the power line 3 can be detected. The same applies to the operation of the third undervoltage relay 14 and the fourth undervoltage relay 15, and from the operation phases thereof, a short circuit accident occurs between the second bus 2, the receiving wire 4 connected to the second bus 2, and the bank 6. And the fault phase of a ground fault can be detected.
[0039]
Next, the operation of the first accident phase selector 3i will be described.
FIG. 4 is an example of a specific configuration of the first accident phase selection unit 3i.
The fault phase selection unit 3i detects a short-circuit phase from the respective operation signals corresponding to the drop in the line voltage of each of the AB, BC, and CA phases of the first undervoltage relay 12 by the OR gates 20a, 20b, and 20c. OR gates 21a, 21b, and 21c OR the respective operating signals with respect to the reduction in the phase voltages of the A, B, and C phases of the second undervoltage relay 13 to obtain the

buses

1 and 2 The fault phase of the short circuit and ground fault of the receiving line 3 and the bank 5 connected to the bus 1 is detected.
[0040]
Further, the AND gates 22a, 22b, and 22c perform a logical product of the fault phase conditions and the operation signals of the respective phases, which are the results of the direction determination of the respective phase currents of the phases A, B, and C of the short-circuit direction relay 3g. And summing up the results by the OR gate 23, thereby selecting only the faulty phase among the respective phase operation signals of the short-circuit direction relay 3g, and determining the direction of the fault current passing through the instep bus 1 side of the doll part. Can be output to the determination unit 16.
[0041]
Similarly, the other first fault phase selectors 4i to 6i can selectively output only the fault phase among the phase operation signals of the corresponding short-circuit direction relays 4g to 6g.
Further, the second fault phase selection units 3j to 6j select only fault phases from the operation signals of the short-circuit direction relays 3h to 6h from the operation signals of the third undervoltage relay 14 and the fourth undervoltage relay 15. This is an output, in which the operation of the first accident phase selection units 3i to 6i is replaced with the maiden bus 2 side.
[0042]
By the operation of the first accident phase selection units 3i to 6i and the second accident phase selection units 3j to 6j, the determination unit 16 determines a failure section based on the direction determination result of only the accident phase in each doll. Can be performed, and erroneous determination of a fault section due to unnecessary operation of the directional relay on the sound phase side in the event of a ground fault at a substation of the direct grounding type can be prevented.
[0043]
Next, an example of the embodiment of the invention will be described.
FIG. 2 shows an example of an embodiment in which the fault zone judging device according to the second aspect of the present invention is applied to a double-bus direct-grounding type substation having two receiving lines and two bank transformers.
In FIG. 2, reference numeral 17 denotes an operation signal for each phase of the bus protection relay on the instep bus 1 side, and reference numeral 18 denotes an operation signal for each phase of the bus protection relay on the second bus line 2 side. Reference numerals 3k to 6k denote first fault phase selectors for selectively outputting only the fault occurrence phase among the phase operation signals of the short-circuit direction relays 3g to 6g from the operation signal 17 of the bus protection relay on the instep bus 1 side. . Similarly, reference numerals 3l to 6l denote second fault phase selectors for selectively outputting only the fault occurrence phase among the phase operation signals of the short-circuit direction relays 3h to 6h from the operation signal 18 of the bus protection relay on the second bus 2 side. is there. Further, since the other configuration is the same as that of FIG. 1, the same portions are denoted by the same reference numerals, and the duplicate description thereof will be omitted.
[0044]
Here, the operation of the current differential type bus protection relay normally applied to the bus protection of the direct ground type substation will be described.
At all times and at the time of an external accident, the inflow current to the bus is always the outflow current, so the total obtained by vector addition of the currents flowing into and out of the bus from each receiving line connected to the bus and each bank is zero. However, at the time of a bus fault, the fault current flows in, but since there is usually no flow current, the sum does not become zero. From this, the bus protection relay adds the current flowing into and out of the bus from each receiving line connected to the bus and each bank, and adds the current to each bus for each phase, and monitors the sum to determine whether the bus has an internal or external accident. Is what you do.
[0045]
As described above, the current differential type bus protection relay performs vector addition for each phase of current flowing into and out of the bus from each receiving line and each bank connected to the bus, and when the sum exceeds a predetermined value. Since it is configured to operate, when an accident current flows into the accident phase due to a short circuit accident or a ground fault accident, the accident current is detected and the bus protection relay of the accident phase operates. However, in the ground fault of the direct grounding substation described above, the ground fault current flowing to the healthy phase side through the neutral point of each directly grounded bank transformer flows through the bus and to the power transformer, Since the inflow current is equal to the outflow current and the subtraction becomes zero, the bus protection relay of the sound phase does not needlessly operate.
[0046]
FIG. 5 shows the relationship between the bus fault condition of the direct grounding type substation and each phase operation signal of the current differential type bus protection relay. As shown in the figure, in the case of a three-phase short circuit, the bus protection relay operates in three phases, and in the case of a two-phase short circuit and a two-wire ground fault, two phases, which are the accident phases thereof, operate. In addition, in the case of a one-line ground fault, the bus protection relay operates in only one phase of the fault phase.
As described above, the operating phase of the current-differential bus protection relay matches the fault phase of the bus fault, that is, judging the fault phase of the bus fault from the operating phase of the current differential bus protection relay. Can be.
[0047]
From this, the first fault phase selector 3k selects and outputs only the fault phase from the phase operation signals 17 of the bus protection relay on the instep bus 1 side to the phase operation signals of the short-circuit direction relay 3g. 6 is an example of a specific configuration of the first accident phase selection unit 3k.
Since the operation phase of the bus protection relay 17 coincides with the fault phase of the bus fault, the AND gates 24a, 24b and 24c operate the respective phase operation signals of the bus protection relay and the A phase, B phase and C phase of the short-circuit direction relay 3g. The logical product of each phase current and the operation signal of each phase, which is the direction determination result of each phase current, is obtained, and the result is aggregated by the OR gate 25 to select only the faulty phase among the operation signals of each phase of the short-circuit direction relay 3g. Then, it can be output to the determination unit 16 as a direction determination result of the fault current passing through the instep bus 1 side of the doll section.
[0048]
Similarly, the other first fault phase selectors 4k to 6k selectively output only the fault phase from the phase operation signals of the corresponding short-circuit direction relays 4g to 6g. The second fault phase selectors 31 to 61 select and output only the fault phase from the phase operation signals of the corresponding short-circuit direction relays 3j to 6j from the phase operation signals 18 of the bus protection relays on the second bus 2 side. Things.
By the operation of the first accident phase selection units 3k to 6k and the second accident phase selection units 31 to 61, the determination unit 16 determines the failure section based on the direction determination result of only the accident phase in each doll. This makes it possible to prevent erroneous determination of a fault section due to unnecessary operation of the directional relay on the sound phase side in the event of a ground fault in a direct grounding type substation.
[0049]
【The invention's effect】
As described above, according to the present invention, a faulty section can be accurately determined because there is no influence of unnecessary operation of a healthy-phase directional relay at the time of a ground fault in a substation of a direct grounding system.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of an embodiment of a fault zone determination device according to the present invention;
FIG. 2 is an explanatory diagram showing an example of an embodiment of a failure section determination device according to the invention of claim 2;
FIG. 3 is an explanatory diagram showing an operation of the undervoltage relay according to the first embodiment of the present invention.
FIG. 4 is an explanatory diagram of an example of a specific configuration of the accident phase selection unit according to the first embodiment of the present invention.
FIG. 5 is an explanatory diagram showing the operation of the bus protection relay according to the second aspect of the present invention.
FIG. 6 is an explanatory diagram of an example of a specific configuration of an accident phase selection unit according to the second aspect of the present invention.
FIG. 7 is an operation characteristic diagram of the directional relay.
FIG. 8 is an explanatory diagram of a direction of a ground fault current of a direct grounding system.
FIG. 9 is a zero-phase circuit of a direct grounding system.
FIG. 10 is a current / voltage vector diagram at the time of one-line ground fault of the direct grounding system.
FIG. 11 is an explanatory diagram of a response of a short-circuit direction relay at the time of one-line ground fault of a direct grounding system.
FIG. 12 is an explanatory diagram of a conventional failure section determination device.
[Explanation of symbols]
1,2 busbar
3,4 receiving wire
5,6 transformer bank
7,8 Instrument transformer
3g-6g, 3h-6h Directional relay
3i to 6i, 3j to 6j The accident phase selector according to the invention of claim 1
3k to 6k, 3l to 6l Accident phase selection unit according to the invention of claim 2
12,13,14,15 Undervoltage relay
16 Judgment unit
17, 18 Operation signal of bus protection relay

Claims

From each receiving line, each transformer bank, and each figure of each transmission line of a direct grounding substation consisting of two buses connecting a plurality of receiving lines, a plurality of transformer banks, and a plurality of transmission lines. A first group of short-circuit direction relays for determining a direction of an accident current flowing into and out of the first bus;
A second group of short-circuit direction relays for determining a direction of an accident current flowing into and out of the second bus from each of the doll parts;
A first undervoltage relay for detecting each line voltage drop of the first bus,
A second undervoltage relay for detecting each phase voltage drop of the first bus,
A third undervoltage relay for detecting a voltage drop between the lines of the second bus,
A fourth undervoltage relay for detecting each phase voltage drop of the second bus,
Detecting an accident phase of a bus fault involving the first bus from each phase operation signal of the first undervoltage relay and each phase operation signal of the second undervoltage relay; A first accident phase selection unit group for selecting an operation signal of an accident phase among the phase operation signals of the group;
Detecting an accident phase of a bus fault involving the second bus from each phase operation signal of the third undervoltage relay and each phase operation signal of the fourth undervoltage relay; A second accident phase selection unit group for selecting an operation signal of an accident phase among the phase operation signals of the group;
A determination unit that detects an accident section of a bus accident from an output of the first accident phase selection unit group and an output of the second accident phase selection unit group;
A substation failure section determination device, comprising:

From each receiving line, each transformer bank, and each figure of each transmission line of a direct grounding substation consisting of two buses connecting a plurality of receiving lines, a plurality of transformer banks, and a plurality of transmission lines. A first group of short-circuit direction relays for determining a direction of an accident current flowing into and out of the first bus;
A second group of short-circuit direction relays for determining a direction of an accident current flowing into and out of the second bus from each of the doll parts;
The operation of the fault phase of the phase operation signals of the first group of short-circuit direction relays is performed by using each phase operation signal of each phase current differential type bus protection relay that protects the bus fault involving the first bus. A first accident phase selector group for selecting a signal;
The operation of the fault phase among the phase operation signals of the second short-circuit direction relay group using each phase operation signal of each phase current differential type bus protection relay that protects the bus fault involving the second bus. A second accident phase selector group for selecting a signal;
A determination unit that detects an accident section of a bus accident from an output of the first accident phase selection unit group and an output of the second accident phase selection unit group;
A substation failure section determination device, comprising: