JP4245854B2

JP4245854B2 - Ground fault direction judgment device

Info

Publication number: JP4245854B2
Application number: JP2002101717A
Authority: JP
Inventors: 忠史松下; 昌善日山; 修治砂野
Original assignee: Shikoku Electric Power Co Inc; Shikoku Instrumentation Co Ltd
Current assignee: Shikoku Electric Power Co Inc; Shikoku Instrumentation Co Ltd
Priority date: 2002-04-03
Filing date: 2002-04-03
Publication date: 2009-04-02
Anticipated expiration: 2022-04-03
Also published as: JP2003294806A

Description

【０００１】
【発明の属する技術分野】
本発明は、多相送配電線に発生した地絡事故点が送配電線の観測点よりも電源側であるか負荷側であるかを判定する地絡方向判定装置に関する。
【０００２】
【従来の技術】
従来の地絡方向判定方法の一つに、零相電圧および零相電流を利用したものがある。零相電圧は、多相送配電線から検出した各相電圧を加算することにより求めることができ、また零相電流は、多相送配電線から検出した各相電流を加算することにより求めることができる。これら零相電圧および零相電流は、原理的に、地絡のような事故が生じない限り、その値が零となる。
【０００３】
従来の前記地絡方向判定方法では、地絡時に生じる零相電圧および零相電流からそれぞれの基本波成分（６０Ｈｚ）を抽出し、その基本波についての零相電圧および零相電流の位相差を求め、この基本波についての零相電圧および零相電流の位相差から、地絡事故点の方向が判定される。
【０００４】
図７に示すように、それぞれの送配電線１ａ、１ｂ、１ｃに沿って相互に間隔をおいた２点Ａ、Ｂで、それぞれの送配電線１ａ、１ｂ、１ｃに零相電圧および零相電流を検出するための検出手段２ａ〜２ｃ、３ａ〜３ｃを設け、各検出手段が設けられた各観測点Ａ、Ｂで地絡事故点の判定をしたとき、例えば観測点Ｂよりも電源側に位置する観測点Ａで、地絡事故点の方向が負荷側であると判定され、観測点Ｂで地絡事故点の方向が電源側であると判定されると、両観測点Ａ、Ｂ間で地絡が生じていることが分かる。
【０００５】
図８（ａ）および図８（ｂ）は、地絡時に生じる零相電圧および零相電流の位相差から地絡が生じた方向を判定する従来方法の基本原理を示すベクトル図である。図８（ａ）には、多相電源の中性点が接地されていない、いわゆる非接地系の多相送配電の場合における零相電圧および零相電流の基本波成分が、それぞれベクトルＶo、Ｉoで示されている。また、図８（ｂ）は、多相電源の中性点がリアクタンスを介して接地された、いわゆるリアクトル接地系の多相送配電の場合における零相電圧および零相電流の基本波成分が、それぞれベクトルＶo、Ｉoで示されている。
【０００６】
非接地系では、図８（ａ）に示すように、零相電圧ＶoをＸ軸上に書き表すと、零相電流Ｉoは、零相電圧および零相電流の検出点から見て地絡が電源側で生じたとき、Ｙ軸上の正方向に伸びるベクトルＩoで示され、また地絡が検出点よりも負荷側で生じたとき、Ｙ軸上の負方向に伸びるベクトルＩoで示される。この場合、地絡事故点の方向に応じた零相電流Ｉoの位相差は１８０度となり、両者を判定するための位相判定閾値θ_thからそれぞれの零相電流Ｉoまでの位相差は、ほぼ９０度の大きな値を示す。したがって、非接地系では、比較的容易かつ正確に零相電流ＩoがＹ軸の正方向を向いているか負方向を向いているかを判定することができ、これにより正確に地絡事故点の方向を判定することができる。
【０００７】
【発明が解決しようとする課題】
しかしながら、リアクトル接地系では、図８（ｂ）に示すように、零相電圧ＶoをＸ軸上に書き表すと、零相電流Ｉoは、零相電圧および零相電流の検出点から見て地絡が電源側で生じたときのベクトルＩoと、地絡が負荷側で生じたときのベクトルＩoとは、地絡事故点の情況によっては、鋭角θ′の関係になる。
【０００８】
位相判定のための閾値θ_thは、両零相電流Ｉoの位相差θ′の中間値（θ′／２）となるが、そのような場合、零相電圧および零相電流の位相差に基づいて判定する従来方法によれば、検出された零相電流Ｉoが電源側の地絡を示すものであるのか、あるいは負荷側の地絡を示すものであるのかを正確に判定することは難しい。
【０００９】
本発明は、上記の事情に鑑みて為されたもので、その目的は、地絡事故点の方向を正確に判定することができる地絡方向判定装置を提供することにある。
【００１０】
【課題を解決するための手段】
本発明は、基本的には、零相電圧および零相電流を用いるものの、両者の位相差を求めることなく、両者に位相変換を施した後、両者の積で表される電力値を求め、この電力値の積分値に基づいて、すなわち積分値が正の値を示すか負の値を示すかによって、地絡事故点の方向を判定するという構想に立脚する。
【００１１】
ところで、図１（ａ）および図１（ｂ）に示すリアクトル接地系での零相電圧、零相電流の各ベクトル図で以下に説明するように、単に検出された零相電圧および零相電流から電力値を求め、この電力値を積分しても、この積分値から正確かつ明確な地絡方向の判定は、実質的に不可能となる。
【００１２】
その理由を概略的に説明するに、各零相電圧および零相電流には、基本波および基本波の整数倍の周波数を有する高調波が含まれるが、それらの電圧ベクトル、電流ベクトルは、相互に異なる位相関係を示す。図１（ａ）は、基本波についての電圧ベクトル、電流ベクトルがそれぞれ破線で示されている。零相電圧ＶoのベクトルをＸ軸上で正方向に描くと、電源側で地絡が生じたときの零相電流Ｉoは第１象限にＹ軸と角度θをなすベクトルで描くことができる。また、負荷側で地絡が生じたときの零相電流Ｉoは、第２象限にＹ軸と角度θをなすベクトルで描くことができる。
【００１３】
これに対し、図１（ｂ）に示すように、高調波については、その零相電圧ＶoのベクトルをＸ軸上で正方向に描くと、電源側で地絡が生じたときの零相電流ＩoのベクトルはＹ軸上で正方向に描くことができる。また、負荷側で地絡が生じたときの零相電流Ｉoのベクトルは、Ｙ軸上で負方向に描くことができる。
【００１４】
この高調波について、単に零相電圧と零相電流とを相互に乗算して電力値を求め、この電力値を積分しても、零相電圧および零相電流は９０度の位相で互いに同様な脈動波形を描く。そのため、各電力値は周期的に正および負の値を繰り返すので、それらの積分値はほぼ零となり、この積分値は零相電流Ｉoのベクトル方向の決定すなわち地絡方向の判定に実質的に寄与しない。
【００１５】
そこで、図１（ｂ）にベクトルＶo′で示されるように、零相電圧Ｖoの位相を例えば９０度進める。この位相が進められた零相電圧Ｖo′と、零相電流Ｉoとの関係では、電源側で地絡が生じたときの零相電流Ｉoのベクトルは零相電圧Ｖo′の方向に一致する。そのため、それらの積である零相電力は、負になることはなく、正の値を示す。他方、負荷側で地絡が生じたときの零相電流Ｉoのベクトルは、零相電圧Ｖo′の方向と逆方向になる。そのため、それらの積である零相電力は、正になることはなく、負の値を示す。したがって、零相電圧Ｖoの位相を進めることにより、地絡方向に対応して高調波についての積分値の符号を変化させることができ、この高調波成分を判定に有効に利用することが可能となる。
【００１６】
ところが、単に、零相電圧Ｖoの位相を９０度進めると、図１（ａ）に位相変換後の零相電圧Ｖo′で示されているように、破線ベクトルで示された両零相電流Ｉo間で、この零相電圧Ｖo′がＹ軸に一致することになる。この場合、電源側で地絡が生じたときの零相電流Ｉoと零相電圧Ｖo′との積である電力値の積分値、負荷側で地絡が生じたときの零相電流Ｉoと零相電圧Ｖo′との積である電力値の積分値は、いずれも正の値を示すことから、この基本波について積分値が地絡方向の判定に寄与しない結果となる。
【００１７】
高調波についての電力積分値を判定に有効に利用すると共に、この基本波についての積分値をも判定に有効に利用するために、本発明では、零相電圧Ｖoの位相を進めると共に、基本波についての零相電流Ｉoの位相を例えば９０度進める。
【００１８】
図１（ａ）に実線ベクトルＩo′で示されているように、位相変換後の各零相電流Ｉo′の関係では、Ｘ軸を対象軸として、電源側で地絡が生じたときの零相電流Ｉoについての位相変換後の零相電流ベクトルＩo′は、第２象限上に表され、負荷側で地絡が生じたときの零相電流Ｉoについての位相変換後の零相電流ベクトルＩo′は、第３象限上に表される。したがって、基本波についても、電源側で地絡が生じたときの零相電流Ｉoについての位相変換後の零相電流Ｉo′と位相変換後の零相電圧Ｖo′との積である電力値、負荷側で地絡が生じたときの零相電流Ｉoについての位相変換後の零相電流Ｉo′と位相変換後の零相電圧Ｖo′との積である電力値のそれぞれの積分値は、互いに逆符号である正および負に明確に分かれる。
【００１９】
従って、基本波およびその高調波のいずれをも有効に利用して、これらを含む零相電圧、零相電流の積である零相電力値の積分値から、地絡方向を比較的容易に正確に判定することが可能となる。
【００２１】
請求項１に記載の地絡方向判定装置は、多相の送配電線から零相電圧を検出する零相電圧検出器と、前記多相の送配電線から零相電流を検出する零相電流検出器と、前記零相電圧検出器からの零相電圧の位相を９０度ずらすための第１の位相変換器と、前記零相電流検出器からの零相電流の基本波の位相を９０度ずらすための第２の位相変換器と、該両位相変換器から得られた零相電圧および零相電流を時系列的に順次乗算する乗算器と、該乗算器の乗算結果を所定の期間で積分する積分器と、該積分器の積分値の符号が正であるか負であるかを判定する判定器とを備えることを特徴とする。
【００２２】
請求項２に記載の地絡判定装置は、請求項１記載の地絡方向判定装置において、前記零相電圧に含まれ、基本波の整数倍の周波数を有する高調波の所定周波数よりも高い遮断周波数を有し前記零相電圧の前記基本波および高調波の位相を９０度ずらすハイパスフィルタであり、前記第２の位相変換器は、前記零相電流の基本波の周波数にほぼ等しい遮断周波数を有し、前記零相電流の基本波の位相を９０度ずらす第２のハイパスフィルタであることを特徴とする。
【００２３】
請求項３に記載の地絡判定装置は、請求項１記載の地絡方向判定装置において、
前記各位相変換器と前記乗算器との間に、前記位相変換器で位相をずらされた零相電圧および零相電流に含まれ、地絡以外の原因で発生する残留零相成分をそれぞれ除去するための残留零相成分除去回路を設けたことを特徴とする。
【００２４】
請求項４に記載の地絡方向判定装置は、請求項３に記載の地絡方向判定装置において、前記零相電圧または前記零相電流の値が所定の閾値を越えるキック成分を検出するキック成分検出部と、位相をずらされた前記零相電圧および零相電流の各データをそれぞれ時系列的に記憶し、前記キック成分検出部が前記キック成分を検出したとき、記憶された前記零相電圧のデータと前記零相電流のデータとのうち、キック成分検出時点からその直後の一サイクル分の各データとキック成分検出時点より前の一サイクル分の各データとを出力する波形抽出部と、該波形抽出部から出力された前記各データを用いて残留零相成分が除去された零相電圧データおよび零相電流データを求める演算処理部とを有し、該演算処理部により求められた前記零相電圧データおよび零相電流データが前記乗算器に供給されることを特徴とする。
【００２５】
請求項５に記載の地絡方向判定装置は、請求項４に記載の地絡方向判定装置において、前記波形抽出部は、位相がずらされた前記零相電圧および零相電流の各データおよび位相をずらす前の前記零相電圧のデータをそれぞれ記憶し、記憶されたデータの量が記憶容量を越えるとき、先に記憶されたデータから順次破棄され、引き続く新たなデータが記憶されることにより、記憶データが順次更新されるメモリと、前記キック成分検出部からの検出信号の有無に応じて、位相をずらされた前記零相電圧および零相電流の各所定のデータを前記メモリから前記演算処理部に供給する制御部とを有することを特徴とする。
【００２６】
請求項６に記載の地絡方向判定装置は、請求項５に記載の地絡方向判定装置において、前記制御部は、前記キック成分検出部がキック成分を検出したとき、位相をずらす前の前記零相電圧データから前記キック成分が前記閾値よりも小さな値の閾値を超える直前の地絡発生時点を求め、位相をずらされた前記零相電圧および零相電流の各データのうち、求めた前記地絡発生時点の直前の一サイクル分のデータをそれぞれの残留零相成分データとして、また前記地絡発生時点の直後の一サイクル分のデータを残留零相成分を含む零相電圧データおよび零相電流データとして、それぞれ前記演算処理部に供給し、他方、前記キック成分検出部がキック成分を検出しないとき、位相をずらす前の前記零相電圧データからその基本波成分を求め、位相をずらされた前記零相電圧および零相電流のデータのうち、求めた前記基本波成分の最小レベル時に対応する一サイクル分のデータをそれぞれの残留零相成分データとして、また、求めた前記基本波成分の最大のレベルに対応する一サイクル分のデータを残留零相成分を含む零相電圧データおよび零相電流データとして、それぞれ前記演算処理部に供給することを特徴とする。
【００２７】
請求項１に記載の発明によれば、検出された零相電圧および零相電流の位相差を求めることなく、それらに所定の位相変換を施した後、それらの乗算により、各電力値を算出し、該各電力値を積分して得られた積分結果の符号が正であるとき、たとえば検出位置から電源側で地絡が生じたと判定することができ、積分結果の符号が負であるとき、検出位置から負荷側で地絡が生じたと判定することができる。
【００２８】
請求項２に記載の地絡方向判定装置によれば、第１の位相変換器として、高調波の周波数よりも高い値の遮断周波数を有するハイパスフィルタを用い、第２の位相変換器として基本波の周波数にほぼ等しい値の遮断周波数を有するハイパスフィルタを用いることにより、単純な構成により、零相電圧および零相電流のそれぞれの位相を適正にずらすことが可能となる。
【００２９】
請求項３に記載の地絡方向判定装置によれば、残留零相成分除去回路により、零相電圧および零相電流に含まれるノイズ成分を好適に除去することができ、これにより、地絡方向の判定精度を高めることができる。
【００３０】
請求項４、５、６に記載の地絡方向判定装置によれば、地絡の発生時点を零相電圧に含まれるキック成分の検出により、適正に判定することができ、この判定により、適正な波形データに基づいて地絡方向をより正確に判定することが可能となる。
【００３１】
【発明の実施の形態】
以下、本発明に係わる地絡方向判定方法を実施する地絡方向判定装置を示す図示の実施の形態に沿って、詳細に説明する。
【００３２】
図２は、本発明に係わる地絡方向判定装置１０を３相送配電線１１（１１ａ、１１ｂ、１１ｃ）を有するリアクトル接地系の配電系統に適用した例を示す。リアクトル接地系では、３相送配電線１１の電源１２の中性点がリアクタンス１３を介して接地されている。
【００３３】
地絡方向判定装置１０は、送配電線１１から零相電圧を検出するための零相電圧検出器１４と、送配電線１１から零相電流を検出するための零相電流検出器１５とを備える。零相電圧検出器１４は、例えば各送配電線１１ａ、１１ｂ、１１ｃに設けられる電圧検出計で構成される。零相電流検出器１５は、例えば送配電線１１ａ、１１ｂ、１１ｃを取り巻いて配置される零相変流器で構成される。
【００３４】
地絡方向判定装置１０は、零相電圧検出器１４、零相電流検出器１５で得られた零相電圧および零相電流から地絡事故点Ｆの方向を判定するための判定処理手段１６を備える。
【００３５】
判定処理手段１６は、図示の例ではデジタル処理方式であり、零相電圧検出器１４からの零相電圧のアナログ値を順次サンプリングし、そのアナログ値をデジタル変換するためのＡ／Ｄ変換回路１７と、零相電流検出器１５からの零相電流のアナログ値を順次サンプリングし、そのアナログ値をデジタル変換するためのＡ／Ｄ変換器１８とを備える。
【００３６】
また、判定処理手段１６は、各Ａ／Ｄ変換回路１７、１８によりデジタル変換された零相電圧Ｖo、零相電流Ｉoのそれぞれに位相変換を施すための位相変換器１９、２０と、両位相変換器１９、２０を経て位相にずれを与えられた零相電圧Ｖo′、零相電流Ｉo′から地絡以外の原因、例えば降雨や積雪のような周囲環境の変化等により生じる残留零相成分を除去するための残留零相成分除去回路２１と、この残留零相成分除去回路２１からの零相電圧Ｖo′、零相電流Ｉo′を相互に乗算して零相電力Ｐoを求めるための乗算器２２と、乗算器２２の演算結果を積分するための積分器２３と、積分器２３の演算結果の符号の判定を行う符号判定器２４とを備える。
【００３７】
零相電圧検出器１４からＡ／Ｄ変換回路１７を経て零相電圧Ｖoの供給を受ける第１の位相変換器１９は、この零相電圧Ｖoの基本波の周波数（例えば６０Ｈｚ）の整数倍の周波数を有する高調波よりも十分に高い周波数、例えば６４次の高調波周波数に等しい周波数の遮断周波数（例えば３８４０Ｈｚ）を有する。この遮断周波数よりも十分低い周波数の零相電圧Ｖoは、位相変換器１９を経ることにより、その基本波成分および高調波成分共に、位相が９０度進められる。この第１の位相変換器１９として、例えばデジタルハイパスフィルタを用いることができる。
【００３８】
零相電流検出器１５からＡ／Ｄ変換回路１８を経て零相電流Ｉoの供給を受ける第２の位相変換器２０は、この零相電圧Ｉoの基本波の周波数（例えば６０Ｈｚ）にほぼ等しい遮断周波数を有する。零相電流Ｉoの高調波は、この遮断周波数よりも十分に高い周波数を有するので、その位相を進められることなく位相変換器２０を通過する。しかしながら、零相電流Ｉoの基本波は、遮断周波数にほぼ等しい周波数を有する。そのため、零相電流Ｉoは、位相変換器２０を経ることにより、零相電圧Ｖoの基本波成分のみがその位相を９０度進められる。この第２の位相変換器２０として、例えば２次のバターワースデジタルハイパスフィルタを用いることができる。
【００３９】
残留零相成分除去回路２１は、図３に示すように、Ａ／Ｄ変換回路１７から、第１の位相変換器１９による位相変換を受けない零相電圧Ｖoの供給を受けるキック成分検出部２５と、両位相変換器１９、２０によりそれぞれ位相を進められた零相電圧Ｖo′、零相電流Ｉo′の供給を受け、また、キック成分検出部２５と同様に、位相変換器１９による位相変換を受けない零相電圧Ｖoの供給を受ける波形抽出部２６と、波形抽出部２６からの波形データを演算処理するための演算処理部２７とを備える。
【００４０】
キック成分検出部２５は、第１の位相変換器１９に用いたと同様のハイパスフィルタ２８と、比較器２９とを有する。比較器２９は、ハイパスフィルタ２８を通過した零相電圧Ｖoの高周波成分Ｖohpfの強度と予め設定されたキック電圧検出用閾値Ｖokとを比較する。この閾値Ｖokは、図５の（ａ）に示されているように、地絡発生時に生じる零相電圧Ｖoの急峻に立ち上がる高周波成分Ｖohpfを検出するのに適正な値に設定される。比較器２９は、高周波成分Ｖohpfの強度がキック電圧検出用閾値Ｖokを越えたとき、検出信号Ｓをキック検出信号として波形抽出部２６に出力する。
【００４１】
波形抽出部２６は、メモリ３０と、該メモリの動作を制御する制御部３１とを有する。メモリ３０は、制御部３１の制御により、第１の位相変換器１９から順次供給される零相電圧Ｖo′の零相電圧データ、第２の位相変換器２０から順次供給される零相電流Ｉo′の零相電流データ、位相変換を受けていない零相電圧Ｖoの零相電圧データをそれぞれ時系列的に格納する。メモリ３０は、例えば３秒間の各データを格納する記憶容量を有し、制御部３１の制御下で、記憶されたデータ量が記憶容量を超えるとき、各データ毎に、記憶されたデータのうち先に記憶されたデータ分から順次破棄し、引き続く新たなデータを記憶する。これにより、メモリ３０内の零相電圧Ｖo′の零相電圧データ、零相電流Ｉo′の零相電流データおよび零相電圧Ｖoの零相電圧データが部分的に順次更新される。
【００４２】
また、制御部３１は、キック成分検出部２５からの検出信号Ｓの有無に応じて、時系列的に順次更新されているメモリ３０内の零相電圧Ｖo′の零相電圧データおよび零相電流Ｉo′の零相電流データから選択された所定のデータを演算処理部２７に出力する。
【００４３】
この制御部３１の動作手順を図４に示されたフローチャートに沿って説明する。地絡が検出されたとき、キック成分検出部２５がキック成分である高周波成分Ｖohpfを検出する（ステップＳ１）と、その検出信号Ｓが制御部３１に出力される。制御部３１は、検出信号Ｓを受ける（ステップＳ２）と、図５（ａ）に示されているように、メモリ３０内に格納された位相変換を受けていない零相電圧Ｖoの零相電圧データ（Ｖo）の高周波成分Ｖohpfに基づいて、地絡の発生時点ｔが検出される。この発生時点ｔとして、例えば高周波成分Ｖohpfの強度が設定された前記閾値Ｖokの約１０分の１に達する時間ｔが検出される（ステップＳ３）。
【００４４】
この発生時点ｔが検出されると、制御部３１は、メモリ３０内に格納された零相電圧データ（Ｖo′）、零相電流データ（Ｉo′）のうち、図５（ｂ）および図５（ｃ）に示すように、発生時点ｔの直前の一サイクル分の各零相電圧データＶoa′、零相電流データＩoa′と、発生時点ｔの直後の一サイクル分の各零相電圧データＶob′、零相電流データＩob′とを、演算処理部２７に並列的に出力する（ステップＳ４）。
【００４５】
演算処理部２７が制御部３１から各零相電圧データＶoa′、零相電流データＩoa′、零相電圧データＶob′、零相電流データＩob′を受けると、演算処理部２７は、零相電圧データＶob′の各値からこれに対応する零相電圧データＶoa′の各値を差し引いた結果を順次零相電圧データＶo′として乗算器２２に出力する。また、演算処理部２７は、零相電流データＩob′の各値からこれに対応する零相電流データＩoa′の各値を差し引いた結果を順次零相電圧データＩo′として、零相電圧データＶo′の出力と同時的に、乗算器２２に出力する。
【００４６】
地絡発生時点ｔ後の各零相電圧データＶob′、零相電流データＩob′には、残留零相成分が含まれているが、その直前の各零相電圧データＶoa′、零相電流データＩoa′にも同様な残留零相成分が含まれていると考えられる。従って、地絡発生時点ｔの直後におけるの零相電圧データＶob′、零相電流データＩob′からその直後の各零相電圧データＶoa′、零相電流データＩoa′をそれぞれ差し引くことにより、この残留零相成分を除去した、零相電圧データＶo′および零相電流データＩo′を乗算器２２に並列的すなわち同時的に出力することができる。
【００４７】
地絡が検出されたとき、その零相電圧Ｖoにキック成分が含まれていない場合、すなわち制御部３１がキック成分検出部２５からの検出信号Ｓを検出しない場合（ステップＳ２）、制御部３１は、図６（ａ）に示されているように、メモリ３０内に格納された位相変換を受けていない零相電圧Ｖoの零相電圧データ（Ｖo）からその基本波を抽出する（ステップＳ５）。制御部３１は、抽出された基本波の最小レベルを示す一サイクルおよび最大レベルを示す一サイクルを求め、零相電圧データ（Ｖo′）、零相電流データ（Ｉo′）のうち、図６（ｂ）、図６（ｃ）に示すように、零相電圧データ（Ｖo）の最小レベル、最大レベルに対応する各一サイクル分の零相電圧データＶoa′、零相電圧データＶob′と、零相電流データＩoa′、零相電流データＩob′とを、演算処理部２７に並列的に出力する（ステップＳ６）。
【００４８】
演算処理部２７は、制御部３１からの各零相電圧データＶoa′、零相電流データＩoa′を残留零相成分として、零相電圧データＶob′、零相電流データＩob′からそれぞれを差し引き、この差し引いた結果を順次零相電圧データＶo′および零相電圧データＩo′として、同時的に、乗算器２２に出力する。
【００４９】
再び図２を参照するに、残留零相成分除去回路２１から残留零相成分を除去された零相電圧データＶo′、零相電流データＩo′が同時的かつ時系列に乗算器２２に出力されると、該乗算器２２は、それらを相互に乗算して、サンプリング毎の電力値Ｐoを算出する。乗算器２２により算出された各電力値Ｐoは、積分器２３により、基本波の一サイクル分にわたって積分され、この積分値の符号が符号判定器２４により判定される。
【００５０】
本発明に係る地絡方向判定装置１０では、零相電圧と零相電流との積で表される電力値Ｐoを求めるについて、零相電圧Ｖoは、第１の位相変換器であるハイパスフィルタ１９により、その基本波および高調波共に、位相を９０度進められている。また零相電流Ｉoは、第２の位相変換器であるハイパスフィルタ２０により、その基本波のみの位相が９０度進められている。そのため、図１のベクトル図に沿って本発明の基本原理で説明したとおり、地絡が零相電圧および零相電流の検出位置よりも電源１２で生じているとき、高調波成分については、それらの積分値の符号は正の値を示す。また、基本波成分についても、それらの積分値の符号は正の値を示すので、符号判定器２４により、明確に正符号の判定結果を得ることができる。
【００５１】
他方、地絡が零相電圧および零相電流の検出位置よりも電源１２と反対側、即ち負荷側で生じているとき、高調波成分については、それらの積分値の符号は負の値を示す。また、基本波成分についても、それらの積分値の符号は負の値を示すので、符号判定器２４により、明確に負符号の判定結果を得ることができる。
【００５２】
図１に示す例では、符号判定器２４により負の判定結果が出力され、この判定結果により、電源１２と反対側の負荷側で地絡事故が生じていると判定することができる。
【００５３】
本発明に係わる地絡方向判定装置１０によれば、位相を変換された零相電圧および零相電流から求めた零相電力の積分値の符号に応じて、地絡の発生方向を判定することができ、これにより零相電圧および零相電流間の位相差から位相判定のための閾値を用いることなく、地絡の発生方向を判定することができる。従って、従来に比較して正確かつ容易に地絡の発生方向が電源側であるか負荷側であるかを判定することができる。
【００５４】
また、残留零相成分除去回路２１を不要とすることができるが、この残留零相成分は、零相電圧Ｖoおよび零相電流Ｉoのベクトル方向を変化させるので、この残留零相成分による各零相電圧Ｖoおよび零相電流Ｉoのベクトル方向の変位による誤動作を確実に防止し、より正確な判定を可能とする上で、残留零相成分除去回路２１を設けることが望ましい。
【００５５】
図示の実施の形態では、零相電圧および零相電流の位相をほぼ９０度進める例を示したが、零相電圧Ｖoの基本波および高調波の位相を９０度の奇数倍、進めることができ、また零相電流Ｉoの基本波の位相を同様に９０度の奇数倍進めることができる。
【００５６】
また、例えば零相電圧Ｖoの基本波および高調波の位相を２７０度進め、すなわち９０度遅らせ、零相電流Ｉoの基本波の位相を同様に２７０度進め、すなわち９０度遅らせた場合、符号判定器２４の負の判定結果は、地絡が電源側で生じていることを意味し、正の判定結果は地絡が負荷側で生じていることを意味する。
【００５７】
本発明は、実施の形態で示したリアクトル接地系に限らず、非接地系にも適用することができる。
【００５８】
【発明の効果】
請求項１に記載の発明によれば、検出された零相電圧および零相電流の位相差を求めることなく、位相がずらされた零相電圧および零相電流から各電力値を求め、この電力値を積分して得られた積分結果の符号に応じて地絡事故のの発生点の方向を判定することができ、これにより、地絡事故の発生点の方向を正確に判定することができる。
【００５９】
請求項２に記載の地絡方向判定装置によれば、単純な構成により、零相電圧および零相電流の位相を適正にずらすことができ、これにより単純な構成でもって正確に地絡事故の発生点の方向を判定することができる。
【００６０】
請求項３に記載の地絡方向判定装置によれば、零相電圧および零相電流に含まれるノイズ成分を好適に除去することができ、これにより、地絡方向の判定精度をより高めることができる。
【００６１】
請求項４、５、６に記載の地絡方向判定装置によれば、地絡の発生時点を零相電圧に含まれるキック成分の検出による適正に判定することができ、この判定結果から適正な波形データに基づいて地絡方向をより正確に判定することが可能となる。
【図面の簡単な説明】
【図１】図１（ａ）および図１（ｂ）は、それぞれ本発明に係わる地絡方向判定方法の基本原理を説明するためのベクトル図である。
【図２】本発明に係わる地絡方向判定方法を実施する地絡方向判定装置を概略的に示すブロック図である。
【図３】図２に示した残留零相成分除去回路を概略的に示すブロック図である。
【図４】図３に示した残留零相成分除去回路による波形抽出手順を示すフローチャートである。
【図５】波形抽出手順で「キック有り」と判定された場合の波形抽出原理を示す説明図である。
【図６】波形抽出手順で「キック無し」と判定された場合の波形抽出原理を示す説明図である。
【図７】従来の地絡方向判定方法の適用例を示す斜視図である。
【図８】図８（ａ）および図８（ｂ）は、それぞれ従来の地絡方向判定方法の基本原理を説明するためのベクトル図である。
【符号の説明】
１０地絡方向判定装置
１１（１１ａ、１１ｂ、１１ｃ）送配電線
１２電源
１４零相電圧検出器
１５零相電流検出器
１９、２０位相変換器（ハイパスフィルタ）
２１残留零相成分除去回路
２２乗算器
２３積分器
２４符号判定器[0001]
BACKGROUND OF THE INVENTION
The present invention determines whether the ground fault point occurring in the multiphase transmission / distribution line is on the power supply side or the load side with respect to the observation point of the transmission / distribution line. Ground fault direction determination device About.
[0002]
[Prior art]
One conventional ground fault direction determination method uses a zero-phase voltage and a zero-phase current. The zero-phase voltage can be obtained by adding each phase voltage detected from the multi-phase transmission / distribution line, and the zero-phase current can be obtained by adding each phase current detected from the multi-phase transmission / distribution line. Can do. These zero-phase voltage and zero-phase current are zero in principle unless an accident such as a ground fault occurs.
[0003]
In the conventional ground fault direction determination method, each fundamental wave component (60 Hz) is extracted from the zero phase voltage and the zero phase current generated at the time of the ground fault, and the phase difference between the zero phase voltage and the zero phase current for the fundamental wave is calculated. The direction of the ground fault point is determined from the phase difference between the zero phase voltage and the zero phase current for the fundamental wave.
[0004]
As shown in FIG. 7, zero-phase voltage and zero-phase are applied to each of the transmission and distribution lines 1a, 1b, and 1c at two points A and B that are spaced apart from each other along each of the transmission and distribution lines 1a, 1b, and 1c. When detecting means 2a to 2c and 3a to 3c for detecting the current are provided and the ground fault point is determined at each of the observation points A and B provided with each of the detecting means, for example, the power source side from the observation point B If the direction of the ground fault point is determined to be on the load side at the observation point A located at, and the direction of the ground fault point is determined to be on the power source side at the observation point B, both observation points A and B It can be seen that there is a ground fault between them.
[0005]
FIGS. 8A and 8B are vector diagrams showing the basic principle of a conventional method for determining the direction in which a ground fault has occurred from the phase difference between the zero-phase voltage and the zero-phase current that occur during a ground fault. FIG. 8A shows the fundamental wave components of the zero-phase voltage and the zero-phase current in the case of so-called non-grounded multi-phase power transmission and distribution in which the neutral point of the multi-phase power source is not grounded, respectively, as a vector Vo, It is indicated by Io. FIG. 8 (b) shows the fundamental wave components of the zero-phase voltage and the zero-phase current in the case of so-called reactor grounded multi-phase power transmission and distribution in which the neutral point of the multi-phase power source is grounded via reactance. Respectively indicated by vectors Vo and Io.
[0006]
In the non-grounded system, as shown in FIG. 8A, when the zero-phase voltage Vo is written on the X axis, the zero-phase current Io has a ground fault when viewed from the detection point of the zero-phase voltage and zero-phase current. When it occurs on the side, it is indicated by a vector Io extending in the positive direction on the Y-axis, and when a ground fault occurs on the load side from the detection point, it is indicated by a vector Io extending in the negative direction on the Y-axis. In this case, the phase difference of the zero-phase current Io corresponding to the direction of the ground fault point is 180 degrees, and the phase determination threshold θ for determining both _th To each zero-phase current Io shows a large value of approximately 90 degrees. Therefore, in the non-grounded system, it is possible to determine whether the zero-phase current Io is facing the positive direction or the negative direction of the Y-axis relatively easily and accurately, thereby accurately determining the direction of the ground fault point. Can be determined.
[0007]
[Problems to be solved by the invention]
However, in the reactor grounding system, as shown in FIG. 8B, when the zero-phase voltage Vo is written on the X axis, the zero-phase current Io is a ground fault as seen from the detection points of the zero-phase voltage and the zero-phase current. Depending on the situation of the ground fault point, the vector Io at the time when the ground fault occurs on the power supply side and the vector Io when the ground fault occurs on the load side have an acute angle θ ′ relationship.
[0008]
Threshold value θ for phase judgment _th Is the intermediate value (θ ′ / 2) of the phase difference θ ′ between the two zero-phase currents Io. In such a case, according to the conventional method of determining based on the phase difference between the zero-phase voltage and the zero-phase current, It is difficult to accurately determine whether the detected zero-phase current Io indicates a ground fault on the power supply side or a ground fault on the load side.
[0009]
The present invention has been made in view of the above circumstances, and its purpose is to accurately determine the direction of the ground fault point. Possible ground fault It is to provide a direction determination device.
[0010]
[Means for Solving the Problems]
The present invention basically uses a zero-phase voltage and a zero-phase current, but without obtaining the phase difference between the two, after performing phase conversion on both, find the power value represented by the product of both, Based on the integral value of the power value, that is, based on the concept of determining the direction of the ground fault point depending on whether the integral value shows a positive value or a negative value.
[0011]
By the way, as will be described below with reference to the vector diagrams of the zero-phase voltage and zero-phase current in the reactor grounding system shown in FIGS. 1A and 1B, the detected zero-phase voltage and zero-phase current are simply detected. Even if the power value is obtained from this and the power value is integrated, it is substantially impossible to accurately and clearly determine the ground fault direction from the integrated value.
[0012]
To explain the reason roughly, each zero-phase voltage and zero-phase current includes a fundamental wave and a harmonic having a frequency that is an integer multiple of the fundamental wave. Shows different phase relationships. In FIG. 1A, the voltage vector and the current vector for the fundamental wave are indicated by broken lines. When the vector of the zero-phase voltage Vo is drawn in the positive direction on the X-axis, the zero-phase current Io when a ground fault occurs on the power supply side can be drawn by a vector that forms an angle θ with the Y-axis in the first quadrant. Further, the zero-phase current Io when a ground fault occurs on the load side can be drawn by a vector that forms an angle θ with the Y axis in the second quadrant.
[0013]
On the other hand, as shown in FIG. 1B, for harmonics, when the vector of the zero-phase voltage Vo is drawn in the positive direction on the X-axis, the zero-phase current when a ground fault occurs on the power supply side The vector of Io can be drawn in the positive direction on the Y axis. The vector of the zero-phase current Io when a ground fault occurs on the load side can be drawn in the negative direction on the Y axis.
[0014]
For this harmonic, the zero-phase voltage and the zero-phase current are simply multiplied by each other to obtain a power value, and even if this power value is integrated, the zero-phase voltage and the zero-phase current are 90 degrees in phase. Draw a pulsating waveform. Therefore, since each power value periodically repeats positive and negative values, their integrated value becomes almost zero, and this integrated value is substantially used for determining the vector direction of the zero-phase current Io, that is, determining the ground fault direction. Does not contribute.
[0015]
Therefore, as shown by the vector Vo ′ in FIG. 1B, the phase of the zero-phase voltage Vo is advanced by 90 degrees, for example. In relation to the zero-phase voltage Vo ′ whose phase has been advanced and the zero-phase current Io, the vector of the zero-phase current Io when a ground fault occurs on the power supply side coincides with the direction of the zero-phase voltage Vo ′. Therefore, the zero-phase power that is the product of these products does not become negative and shows a positive value. On the other hand, the vector of the zero-phase current Io when a ground fault occurs on the load side is opposite to the direction of the zero-phase voltage Vo ′. Therefore, the zero-phase power that is the product of these products does not become positive and shows a negative value. Therefore, by advancing the phase of the zero-phase voltage Vo, the sign of the integrated value for the harmonic can be changed corresponding to the ground fault direction, and this harmonic component can be effectively used for determination. Become.
[0016]
However, when the phase of the zero-phase voltage Vo is simply advanced by 90 degrees, as shown by the zero-phase voltage Vo ′ after phase conversion in FIG. In the meantime, this zero-phase voltage Vo ′ coincides with the Y-axis. In this case, the integral value of the power value, which is the product of the zero-phase current Io and the zero-phase voltage Vo ′ when a ground fault occurs on the power supply side, and the zero-phase current Io and zero when a ground fault occurs on the load side Since the integral value of the power value, which is the product of the phase voltage Vo ′, shows a positive value, the integral value of this fundamental wave does not contribute to the determination of the ground fault direction.
[0017]
In order to effectively use the power integral value for the harmonic wave for the determination and also effectively use the integral value for the fundamental wave for the determination, in the present invention, the phase of the zero-phase voltage Vo is advanced and the fundamental wave is also used. For example, the phase of the zero-phase current Io is advanced by 90 degrees.
[0018]
As shown by the solid line vector Io ′ in FIG. 1A, the relationship between the zero-phase currents Io ′ after phase conversion is zero when a ground fault occurs on the power source side with the X axis as the target axis. Zero phase current vector Io ′ after phase conversion for phase current Io is represented in the second quadrant, and zero phase current vector Io after phase conversion for zero phase current Io when a ground fault occurs on the load side. 'Is represented in the third quadrant. Therefore, also for the fundamental wave, a power value that is the product of the phase-converted zero-phase current Io ′ and the phase-converted zero-phase voltage Vo ′ for the zero-phase current Io when a ground fault occurs on the power supply side, The integral values of the power values, which are the products of the phase-converted zero-phase current Io ′ and the phase-converted zero-phase voltage Vo ′ for the zero-phase current Io when a ground fault occurs on the load side, are It is clearly divided into positive and negative signs.
[0019]
Therefore, by effectively using both the fundamental wave and its harmonics, the ground fault direction can be determined relatively easily and accurately from the integral value of the zero-phase power value, which is the product of the zero-phase voltage and zero-phase current including them. Can be determined.
[0021]
Claim 1 The ground fault direction determination device according to claim 1, a zero-phase voltage detector that detects a zero-phase voltage from a multi-phase transmission / distribution line, and a zero-phase current detector that detects a zero-phase current from the multi-phase transmission / distribution line; A first phase converter for shifting the phase of the zero phase voltage from the zero phase voltage detector by 90 degrees, and a phase shift of the fundamental wave of the zero phase current from the zero phase current detector by 90 degrees A second phase converter, a multiplier that sequentially multiplies the zero-phase voltage and the zero-phase current obtained from both phase converters in time series, and an integration that integrates the multiplication results of the multiplier over a predetermined period And a determination unit for determining whether the sign of the integration value of the integrator is positive or negative.
[0022]
Claim 2 The ground fault determination device described in Claim 1 The ground fault direction determination device according to claim 1, wherein the fundamental wave and the harmonic wave of the zero-phase voltage have a cutoff frequency higher than a predetermined frequency of a harmonic wave that is included in the zero-phase voltage and has a frequency that is an integral multiple of the fundamental wave. The second phase converter has a cutoff frequency substantially equal to the frequency of the fundamental wave of the zero-phase current, and the phase of the fundamental wave of the zero-phase current is 90 degrees. A second high-pass filter to be shifted is characterized.
[0023]
Claim 3 The ground fault determination device described in Claim 1 In the ground fault direction determination device described,
The residual zero-phase components that are included in the zero-phase voltage and zero-phase current shifted in phase by the phase converter and are caused by causes other than ground faults are removed between each phase converter and the multiplier. A residual zero-phase component removing circuit is provided.
[0024]
Claim 4 The ground fault direction determination device described in Claim 3 In the ground fault direction determination device according to claim 1, a kick component detection unit that detects a kick component in which a value of the zero-phase voltage or the zero-phase current exceeds a predetermined threshold, and the zero-phase voltage and the zero-phase shifted in phase Each current data is stored in time series, and when the kick component detection unit detects the kick component, the kick component detection is performed among the stored zero phase voltage data and the zero phase current data. A waveform extractor for outputting each data for one cycle immediately after the time and each data for one cycle before the kick component detection time, and using the data output from the waveform extractor, An arithmetic processing unit that obtains zero-phase voltage data and zero-phase current data from which phase components have been removed, and the zero-phase voltage data and zero-phase current data obtained by the arithmetic processing unit are supplied to the multiplier. Is the fact characterized.
[0025]
Claim 5 The ground fault direction determination device described in Claim 4 In the ground fault direction determination device according to claim 1, the waveform extraction unit stores the data of the zero-phase voltage and the zero-phase current that are shifted in phase and the data of the zero-phase voltage before the phase is shifted, respectively. When the amount of data exceeds the storage capacity, the previously stored data is sequentially discarded, and the subsequent new data is stored, so that the stored data is sequentially updated, and the kick component detection unit And a control unit that supplies the predetermined data of the zero-phase voltage and the zero-phase current, which are shifted in phase according to the presence or absence of the detection signal, from the memory to the arithmetic processing unit.
[0026]
Claim 6 The ground fault direction determination device described in Claim 5 In the ground fault direction determination device according to claim 1, when the kick component detection unit detects the kick component, the control unit determines that the kick component has a value smaller than the threshold value from the zero-phase voltage data before the phase is shifted. The ground fault occurrence time immediately before exceeding the threshold value is obtained, and among the zero phase voltage and zero phase current data shifted in phase, the data for one cycle immediately before the obtained ground fault occurrence time is stored in the respective data. As zero-phase component data, and data for one cycle immediately after the occurrence of the ground fault are supplied to the arithmetic processing unit as zero-phase voltage data and zero-phase current data including residual zero-phase components, respectively, When the kick component detector does not detect the kick component, the fundamental component is obtained from the zero-phase voltage data before the phase is shifted, and the zero-phase voltage and zero-phase current data that are shifted in phase are obtained. Data corresponding to one cycle corresponding to the minimum level of the fundamental wave component obtained as the residual zero-phase component data, and data corresponding to one cycle corresponding to the maximum level of the fundamental wave component obtained. Are supplied to the arithmetic processing unit as zero-phase voltage data and zero-phase current data including a residual zero-phase component, respectively.
[0027]
Claim 1 According to the invention described in the above, each power value is calculated by performing a predetermined phase conversion on the detected zero-phase voltage and zero-phase current without obtaining a phase difference between them, and multiplying them. When the sign of the integration result obtained by integrating each power value is positive, for example, it can be determined that a ground fault has occurred on the power supply side from the detection position, and when the sign of the integration result is negative, the detection position It can be determined that a ground fault has occurred on the load side.
[0028]
Claim 2 According to the ground fault direction determination device described in the above, a high-pass filter having a cutoff frequency higher than the harmonic frequency is used as the first phase converter, and the fundamental frequency is used as the second phase converter. By using a high-pass filter having substantially the same cutoff frequency, the phases of the zero-phase voltage and the zero-phase current can be appropriately shifted with a simple configuration.
[0029]
Claim 3 According to the ground fault direction determination device described in the above, the noise component included in the zero phase voltage and the zero phase current can be suitably removed by the residual zero phase component removal circuit. Can be increased.
[0030]
Claim 4, 5, 6 According to the ground fault direction determination device described in 1), it is possible to appropriately determine the occurrence time of the ground fault by detecting the kick component included in the zero-phase voltage, and by this determination, the ground fault is determined based on the appropriate waveform data. It becomes possible to determine the entrainment direction more accurately.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, it demonstrates in detail along embodiment of illustration which shows the ground fault direction determination apparatus which implements the ground fault direction determination method concerning this invention.
[0032]
FIG. 2 shows an example in which the ground fault direction determination device 10 according to the present invention is applied to a reactor grounded distribution system having three-phase transmission and distribution lines 11 (11a, 11b, 11c). In the reactor grounding system, the neutral point of the power supply 12 of the three-phase transmission / distribution line 11 is grounded via the reactance 13.
[0033]
The ground fault direction determination device 10 includes a zero-phase voltage detector 14 for detecting a zero-phase voltage from the transmission / distribution line 11 and a zero-phase current detector 15 for detecting a zero-phase current from the transmission / distribution line 11. Prepare. The zero-phase voltage detector 14 is composed of, for example, a voltage detector provided in each of the transmission and distribution lines 11a, 11b, and 11c. The zero-phase current detector 15 is constituted by a zero-phase current transformer that is disposed around, for example, the transmission and distribution lines 11a, 11b, and 11c.
[0034]
The ground fault direction determination device 10 includes a determination processing means 16 for determining the direction of the ground fault point F from the zero phase voltage and the zero phase current obtained by the zero phase voltage detector 14 and the zero phase current detector 15. Prepare.
[0035]
The determination processing means 16 is a digital processing method in the illustrated example, and sequentially samples analog values of the zero-phase voltage from the zero-phase voltage detector 14 and digitally converts the analog values to the A / D conversion circuit 17. And an A / D converter 18 for sequentially sampling the analog value of the zero-phase current from the zero-phase current detector 15 and digitally converting the analog value.
[0036]
The determination processing means 16 includes phase converters 19 and 20 for performing phase conversion on the zero-phase voltage Vo and the zero-phase current Io digitally converted by the A / D conversion circuits 17 and 18, respectively, Residual zero-phase component caused by causes other than the ground fault from the zero-phase voltage Vo ′ and the zero-phase current Io ′ given a phase shift through the converters 19 and 20, for example, changes in the surrounding environment such as rain or snow The residual zero-phase component removing circuit 21 for removing the signal and the multiplication for obtaining the zero-phase power Po by multiplying the zero-phase voltage Vo ′ and the zero-phase current Io ′ from the residual zero-phase component removing circuit 21 with each other. A calculator 22, an integrator 23 for integrating the calculation result of the multiplier 22, and a sign determination unit 24 for determining the sign of the calculation result of the integrator 23.
[0037]
The first phase converter 19 that receives the supply of the zero-phase voltage Vo from the zero-phase voltage detector 14 via the A / D conversion circuit 17 is an integral multiple of the fundamental frequency (for example, 60 Hz) of the zero-phase voltage Vo. It has a cut-off frequency (for example, 3840 Hz) that is sufficiently higher than a harmonic having a frequency, for example, a frequency equal to the 64th-order harmonic frequency. The phase of the zero-phase voltage Vo having a frequency sufficiently lower than the cut-off frequency passes through the phase converter 19 so that the phase of the zero-phase voltage Vo is advanced by 90 degrees. For example, a digital high-pass filter can be used as the first phase converter 19.
[0038]
The second phase converter 20 that receives the supply of the zero-phase current Io from the zero-phase current detector 15 via the A / D conversion circuit 18 is cut off substantially equal to the fundamental frequency (for example, 60 Hz) of the zero-phase voltage Io. Has a frequency. Since the harmonics of the zero-phase current Io have a frequency sufficiently higher than the cut-off frequency, the harmonics of the zero-phase current Io pass through the phase converter 20 without being advanced in phase. However, the fundamental wave of the zero-phase current Io has a frequency approximately equal to the cutoff frequency. Therefore, the phase of the zero-phase current Io passes through the phase converter 20 so that only the fundamental wave component of the zero-phase voltage Vo is advanced in phase by 90 degrees. As the second phase converter 20, for example, a second order Butterworth digital high-pass filter can be used.
[0039]
As shown in FIG. 3, the residual zero-phase component removing circuit 21 is supplied with a zero-phase voltage Vo that is not subjected to phase conversion by the first phase converter 19 from the A / D conversion circuit 17. Are supplied with the zero-phase voltage Vo ′ and the zero-phase current Io ′ whose phases have been advanced by the two phase converters 19 and 20, respectively, and, similarly to the kick component detection unit 25, the phase conversion by the phase converter 19 A waveform extraction unit 26 that receives the supply of the zero-phase voltage Vo that does not receive the signal, and an arithmetic processing unit 27 that performs arithmetic processing on the waveform data from the waveform extraction unit 26.
[0040]
The kick component detection unit 25 includes a high-pass filter 28 similar to that used in the first phase converter 19 and a comparator 29. The comparator 29 compares the intensity of the high-frequency component Vohpf of the zero-phase voltage Vo that has passed through the high-pass filter 28 with a preset kick voltage detection threshold value Vok. As shown in FIG. 5A, the threshold value Vok is set to an appropriate value for detecting the high-frequency component Vophf that rises sharply in the zero-phase voltage Vo generated when a ground fault occurs. The comparator 29 outputs the detection signal S as a kick detection signal to the waveform extraction unit 26 when the intensity of the high frequency component Vohpf exceeds the kick voltage detection threshold Vok.
[0041]
The waveform extraction unit 26 includes a memory 30 and a control unit 31 that controls the operation of the memory. Under the control of the control unit 31, the memory 30 stores zero-phase voltage data of the zero-phase voltage Vo ′ sequentially supplied from the first phase converter 19 and zero-phase current Io sequentially supplied from the second phase converter 20. The zero-phase current data of 'and the zero-phase voltage data of the zero-phase voltage Vo that has not undergone phase conversion are stored in time series. The memory 30 has a storage capacity for storing, for example, each piece of data for 3 seconds. When the amount of stored data exceeds the storage capacity under the control of the control unit 31, for each piece of data, Discard sequentially from the previously stored data and store new data. As a result, the zero-phase voltage data of the zero-phase voltage Vo ′, the zero-phase current data of the zero-phase current Io ′, and the zero-phase voltage data of the zero-phase voltage Vo in the memory 30 are partially updated sequentially.
[0042]
The control unit 31 also detects the zero-phase voltage data and the zero-phase current of the zero-phase voltage Vo ′ in the memory 30 that are sequentially updated in time series according to the presence or absence of the detection signal S from the kick component detection unit 25. Predetermined data selected from the zero-phase current data of Io ′ is output to the arithmetic processing unit 27.
[0043]
The operation procedure of the control unit 31 will be described with reference to the flowchart shown in FIG. When the ground fault is detected, when the kick component detection unit 25 detects the high frequency component Vohpf which is a kick component (step S1), the detection signal S is output to the control unit 31. When the control unit 31 receives the detection signal S (step S2), as shown in FIG. 5A, the zero-phase voltage Vo of the zero-phase voltage Vo that has not been subjected to the phase conversion stored in the memory 30 is obtained. A ground fault occurrence time t is detected based on the high-frequency component Vohpf of the data (Vo). As this occurrence time t, for example, a time t when the intensity of the high-frequency component Vohpf reaches about one-tenth of the threshold value Vok set is detected (step S3).
[0044]
When this occurrence time t is detected, the control unit 31 uses the zero-phase voltage data (Vo ′) and the zero-phase current data (Io ′) stored in the memory 30 as shown in FIGS. As shown in (c), each zero-phase voltage data Voa ′ and zero-phase current data Ioa ′ for one cycle immediately before the generation time t, and each zero-phase voltage data Vob for one cycle immediately after the generation time t. 'And zero-phase current data Iob' are output in parallel to the arithmetic processing unit 27 (step S4).
[0045]
When the arithmetic processing unit 27 receives each zero-phase voltage data Voa ′, zero-phase current data Ioa ′, zero-phase voltage data Vob ′, and zero-phase current data Iob ′ from the control unit 31, the arithmetic processing unit 27 A result obtained by subtracting each value of the zero-phase voltage data Voa ′ corresponding to each value of the data Vob ′ is sequentially output to the multiplier 22 as zero-phase voltage data Vo ′. The arithmetic processing unit 27 sequentially subtracts each value of the zero-phase current data Ioa ′ corresponding to each value of the zero-phase current data Iob ′ as the zero-phase voltage data Io ′, and uses the result as the zero-phase voltage data Vo. Simultaneously with the output of ′, it is output to the multiplier 22.
[0046]
Each zero-phase voltage data Vob ′ and zero-phase current data Iob ′ after the occurrence of the ground fault includes a residual zero-phase component, but each immediately preceding zero-phase voltage data Voa ′ and zero-phase current data are included. Ioa ′ is considered to contain a similar residual zero-phase component. Therefore, by subtracting each zero-phase voltage data Voa 'and zero-phase current data Ioa' immediately after the zero-phase voltage data Vob 'and zero-phase current data Iob' immediately after the occurrence of the ground fault t, Zero-phase voltage data Vo ′ and zero-phase current data Io ′ from which the zero-phase component has been removed can be output to the multiplier 22 in parallel, that is, simultaneously.
[0047]
When a ground fault is detected, if the zero-phase voltage Vo does not include a kick component, that is, if the control unit 31 does not detect the detection signal S from the kick component detection unit 25 (step S2), the control unit 31. 6A, the fundamental wave is extracted from the zero-phase voltage data (Vo) of the zero-phase voltage Vo that has not been subjected to phase conversion and stored in the memory 30 (step S5). ). The control unit 31 obtains one cycle indicating the minimum level and one cycle indicating the maximum level of the extracted fundamental wave, and among the zero-phase voltage data (Vo ′) and the zero-phase current data (Io ′), FIG. b) As shown in FIG. 6C, zero-phase voltage data Voa ', zero-phase voltage data Vob' for one cycle corresponding to the minimum level and maximum level of zero-phase voltage data (Vo), zero phase voltage data The phase current data Ioa ′ and the zero phase current data Iob ′ are output in parallel to the arithmetic processing unit 27 (step S6).
[0048]
The arithmetic processing unit 27 subtracts each of the zero-phase voltage data Voa ′ and the zero-phase current data Iob ′ from the zero-phase voltage data Vob ′ and the zero-phase current data Iob ′ using the zero-phase voltage data Voa ′ and the zero-phase current data Ioa ′ from the control unit 31 as residual zero-phase components. The subtracted results are sequentially output to the multiplier 22 as zero phase voltage data Vo ′ and zero phase voltage data Io ′.
[0049]
Referring again to FIG. 2, the zero-phase voltage data Vo ′ and zero-phase current data Io ′ from which the residual zero-phase component has been removed from the residual zero-phase component removal circuit 21 are output to the multiplier 22 simultaneously and in time series. Then, the multiplier 22 multiplies them and calculates a power value Po for each sampling. Each power value Po calculated by the multiplier 22 is integrated for one cycle of the fundamental wave by the integrator 23, and the sign of the integrated value is determined by the sign determination unit 24.
[0050]
In the ground fault direction determination device 10 according to the present invention, the zero-phase voltage Vo is a first phase converter 19 for obtaining the power value Po represented by the product of the zero-phase voltage and the zero-phase current. Thus, both the fundamental wave and the harmonic wave are advanced in phase by 90 degrees. Further, the phase of only the fundamental wave of the zero-phase current Io is advanced by 90 degrees by the high-pass filter 20 which is the second phase converter. Therefore, as described in the basic principle of the present invention along the vector diagram of FIG. 1, when the ground fault is generated in the power source 12 rather than the detection position of the zero-phase voltage and the zero-phase current, The sign of the integral value indicates a positive value. Also, with respect to the fundamental wave component, since the sign of the integral value indicates a positive value, the sign determination unit 24 can clearly obtain a positive sign determination result.
[0051]
On the other hand, when the ground fault occurs on the side opposite to the power source 12 from the detection position of the zero-phase voltage and zero-phase current, that is, on the load side, the signs of the integral values of the harmonic components indicate negative values. . Also, with respect to the fundamental wave component, since the sign of the integral value indicates a negative value, the sign determination unit 24 can clearly obtain a negative sign determination result.
[0052]
In the example illustrated in FIG. 1, a negative determination result is output by the sign determination unit 24, and it can be determined that a ground fault has occurred on the load side opposite to the power source 12 based on the determination result.
[0053]
According to the ground fault direction determination device 10 according to the present invention, the direction of occurrence of the ground fault is determined according to the sign of the integral value of the zero phase power obtained from the zero phase voltage and the zero phase current whose phase has been converted. Thus, the occurrence direction of the ground fault can be determined from the phase difference between the zero-phase voltage and the zero-phase current without using a threshold for phase determination. Therefore, it is possible to determine whether the direction of occurrence of the ground fault is the power supply side or the load side more accurately and easily than in the past.
[0054]
Further, the residual zero-phase component removing circuit 21 can be dispensed with, but this residual zero-phase component changes the vector direction of the zero-phase voltage Vo and the zero-phase current Io. It is desirable to provide a residual zero-phase component removal circuit 21 in order to reliably prevent malfunction due to displacement of the phase voltage Vo and zero-phase current Io in the vector direction and to enable more accurate determination.
[0055]
In the illustrated embodiment, an example in which the phase of the zero-phase voltage and the zero-phase current is advanced by approximately 90 degrees has been described. However, the fundamental wave and the harmonic phase of the zero-phase voltage Vo can be advanced by an odd multiple of 90 degrees. Similarly, the phase of the fundamental wave of the zero-phase current Io can be advanced by an odd multiple of 90 degrees.
[0056]
For example, if the phase of the fundamental wave and the harmonic of the zero phase voltage Vo is advanced by 270 degrees, that is, delayed by 90 degrees, and the phase of the fundamental wave of the zero phase current Io is similarly advanced by 270 degrees, that is, delayed by 90 degrees, the sign determination The negative determination result of the device 24 means that a ground fault has occurred on the power supply side, and the positive determination result means that a ground fault has occurred on the load side.
[0057]
The present invention can be applied not only to the reactor grounding system shown in the embodiment but also to a non-grounding system.
[0058]
【The invention's effect】
Claim 1 According to the invention described in, each power value is obtained from the phase-shifted zero-phase voltage and zero-phase current without obtaining the phase difference between the detected zero-phase voltage and zero-phase current, and this power value is integrated. The direction of the occurrence point of the ground fault accident can be determined according to the sign of the integration result obtained in this way, and thereby the direction of the occurrence point of the ground fault accident can be accurately determined.
[0059]
Claim 2 According to the ground fault direction determination device described in (1), the phase of the zero-phase voltage and the zero-phase current can be appropriately shifted with a simple configuration, and thus the ground fault accident occurrence point can be accurately detected with the simple configuration. The direction can be determined.
[0060]
Claim 3 According to the ground fault direction determination device described in (1), it is possible to suitably remove the noise component contained in the zero phase voltage and the zero phase current, thereby further improving the accuracy in determining the ground fault direction.
[0061]
Claims 4, 5, 6 According to the ground fault direction determination device described in 1), it is possible to appropriately determine the occurrence time of the ground fault by detecting the kick component included in the zero-phase voltage, and based on the proper waveform data from the determination result, It becomes possible to determine the direction more accurately.
[Brief description of the drawings]
FIGS. 1A and 1B are vector diagrams for explaining the basic principle of a ground fault direction determining method according to the present invention, respectively.
FIG. 2 is a block diagram schematically showing a ground fault direction determining apparatus for executing the ground fault direction determining method according to the present invention.
FIG. 3 is a block diagram schematically showing a residual zero phase component removal circuit shown in FIG. 2;
4 is a flowchart showing a waveform extraction procedure by the residual zero-phase component removal circuit shown in FIG. 3;
FIG. 5 is an explanatory diagram illustrating a waveform extraction principle when it is determined that “kick is present” in the waveform extraction procedure;
FIG. 6 is an explanatory diagram showing a waveform extraction principle when it is determined that “no kick” is obtained in the waveform extraction procedure;
FIG. 7 is a perspective view showing an application example of a conventional ground fault direction determination method.
FIGS. 8A and 8B are vector diagrams for explaining the basic principle of a conventional ground fault direction determination method, respectively.
[Explanation of symbols]
10 Ground fault direction determination device
11 (11a, 11b, 11c)
12 Power supply
14 Zero-phase voltage detector
15 Zero-phase current detector
19, 20 Phase converter (high pass filter)
21 Residual zero-phase component removal circuit
22 multiplier
23 Integrator
24 Code determination unit

Claims

A zero-phase voltage detector for detecting a zero-phase voltage from a multi-phase transmission / distribution line, a zero-phase current detector for detecting a zero-phase current from the multi-phase transmission / distribution line, and a zero-phase voltage detector from the zero-phase voltage detector A first phase converter for shifting the phase of the phase voltage by 90 degrees, a second phase converter for shifting the phase of the fundamental wave of the zero phase current from the zero phase current detector by 90 degrees, A multiplier that sequentially multiplies the zero-phase voltage and zero-phase current obtained from the phase converter in time series, an integrator that integrates the multiplication results of the multiplier over a predetermined period, and an integration value of the integrator A ground fault direction determination apparatus comprising: a determination unit that determines whether a sign is positive or negative.

The first phase converter is included in the zero-phase voltage and has a cutoff frequency higher than a predetermined frequency of a harmonic having a frequency that is an integral multiple of the fundamental wave, and the fundamental and harmonics of the zero-phase voltage. The second phase converter has a cutoff frequency substantially equal to the frequency of the fundamental wave of the zero-phase current, and the phase of the fundamental wave of the zero-phase current is 90 degrees. The ground fault direction determination device according to claim 1, which is a second high-pass filter to be shifted.

The residual zero-phase components that are included in the zero-phase voltage and zero-phase current shifted in phase by the phase converter and are caused by causes other than ground faults are removed between each phase converter and the multiplier. The ground fault direction determination apparatus according to claim 1, further comprising a residual zero-phase component removal circuit for performing the operation.

The residual zero-phase component removal circuit includes a kick component detection unit that detects a kick component in which a value of the zero-phase voltage or the zero-phase current exceeds a predetermined threshold, and the zero-phase voltage and zero-phase current that are out of phase. Are stored in time series, and when the kick component detector detects the kick component, the kick component detection time point out of the stored zero-phase voltage data and the zero-phase current data is stored. A waveform extraction unit for outputting each data for one cycle immediately after that and each data for one cycle before the kick component detection time, and using the data output from the waveform extraction unit, the residual zero phase An arithmetic processing unit for obtaining zero-phase voltage data and zero-phase current data from which components have been removed, and the zero-phase voltage data and zero-phase current data obtained by the arithmetic processing unit are supplied to the multiplier. Ground direction determination apparatus according to claim 3, wherein.

The waveform extraction unit stores the data of the zero-phase voltage and the zero-phase current shifted in phase and the data of the zero-phase voltage before shifting the phase, respectively, and the amount of stored data exceeds the storage capacity When the data is sequentially discarded from the previously stored data and the subsequent new data is stored, the stored data is sequentially updated, and the phase depends on the presence or absence of the detection signal from the kick component detection unit. The ground fault direction determination apparatus according to claim 4, further comprising: a control unit that supplies the predetermined data of the zero-phase voltage and the zero-phase current shifted from each other to the arithmetic processing unit.

When the kick component detection unit detects the kick component, the control unit detects a ground fault occurrence time immediately before the kick component exceeds a threshold value smaller than the threshold value from the zero-phase voltage data before shifting the phase. Of the obtained zero-phase voltage and zero-phase current data obtained by shifting the phase, the data for one cycle immediately before the obtained ground fault occurrence time is used as the respective residual zero-phase component data and the ground fault. Data for one cycle immediately after the occurrence point is supplied to the arithmetic processing unit as zero-phase voltage data and zero-phase current data including residual zero-phase components,
On the other hand, when the kick component detection unit does not detect the kick component, the fundamental component is obtained from the zero-phase voltage data before the phase is shifted, and the phase-shifted data of the zero-phase voltage and the zero-phase current are obtained. The obtained data for one cycle corresponding to the minimum level of the fundamental wave component is used as the respective residual zero-phase component data, and the data for one cycle corresponding to the maximum level of the obtained fundamental wave component is set to the residual zero. The ground fault direction determination device according to claim 5 , wherein zero-phase voltage data including phase components and zero-phase current data are respectively supplied to the arithmetic processing unit.