JP3841248B2 - Ground fault suppression system and ground fault suppression method - Google Patents

Description

となる。
【００１８】
次に、地絡電流の抑制動作は次のようになる。
【００１９】
１．地絡回線１０１の等価零相変流器１０７では、地絡電流Ｉ_g のうちの健全回線および零相変圧器の一次側接地中性線からの流入分Ｉ_g2と逆位相電流Ｉ_V との残差ΔＩ_g2（＝Ｉ_g2＋Ｉ_V ）が検出される。
【００２０】
２．検出された残差ΔＩ_g2は、地絡事故検出装置１０５を通じて、逆位相波形発生装置１０６に入力され、そこで残差ΔＩ_g2に応じた逆位相電流Ｉ_V を生成、注入する。
【００２１】
３．逆位相電流Ｉ_V の注入当初は、残差ΔＩ_g2は小さくなり、次の時点での逆位相電流Ｉ_V の生成・注入量は減少する。
【００２２】
４．地絡が継続している場合、逆位相電流Ｉ_V が減少した分、再度、残差ΔＩ_g2が大きくなる。
【００２３】
５．１〜４の処理を繰り返し、ある一定レベルで抑制率が落ち着く。
【００２４】
このようにして、地絡電流のうちの健全回線の零相電流分および零相変圧器の一次側接地中性線からの流入分の合成電流Ｉ_g2（＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN）が減少する。よって、これに応じて地絡電流Ｉ_g （＝Ｉ_g1＋Ｉ_g2）も減少する。
【００２５】
図７は、従来における地絡電流Ｉ_g の抑制原理を示すベクトル図であって、図７（ａ）は逆位相波形発生装置を適用しない場合の通常の地絡状態、図７（ｂ）は図７（ａ）の状態において逆位相波形発生装置を適用した場合のある時点での状態、図７（ｃ）は図７（ａ）の状態において逆位相波形発生装置を適用した場合の図７（ｂ）とは異なる時点での状態を示すものである。残差ΔＩ_g2（＝Ｉ_g2＋Ｉ_v ）は図６の零相変流器１０７で常にモニタされている。地絡当初は、残差ΔＩ_g2はＩ_g2に等しく、それに応じた逆位相電流Ｉ_v （＝−ΔＩ_g2）を生成、注入する（図７（ａ），（ｂ）参照）。注入後、図７（ｂ）に示すように、残差ΔＩ_g2は小さくなり、その分地絡電流Ｉ_g も抑制される。しかし、残差ΔＩ_g2を常にモニタしているため、次の瞬間では、逆位相電流Ｉ_V は図７（ｃ）に示すような小さな電流となってしまう。また、Ｉ₀₂，Ｉ₀₃，Ｉ_RNの各電流は以前のまま流れようとするため、Ｉ_g2（＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN）は元の大きさに戻ろうとする。そのため、Ｉ_g2の抑制効果が小さくなり、地絡電流Ｉ_g （＝Ｉ_g1＋Ｉ_g2）の抑制効果も小さくなる。
【００２６】
このような図７（ｂ），（ｃ）の動作を繰り返すことにより、前述したように、地絡電流Ｉ_g が復帰して、地絡アークが消弧しずらいという問題が残る。
【００２７】
そこで、本発明の目的は、系統に注入する逆位相電流を安定させ、地絡電流の復帰を防ぎ、地絡アークが消弧しやすい地絡抑制システムおよび地絡抑制方法を提供することにある。
【００２８】
【課題を解決するための手段】
上記目的を達成するために、本発明によれば、共通の母線に接続された複数回線の配電線を備える電力配電線における地絡電流を抑制するものであって、前記電力配電線の零相電圧を検出する零相電圧検出手段および前記配電線の各零相電流を検出する零相電流検出手段を具えるとともに、前記零相電流検出手段により検出された電流に基づいて健全回線を判別する健全回線判別手段と、前記判別された健全回線の零相電流のベクトル和に基づいて近似地絡電流を算出する近似地絡電流算出手段と、前記算出された近似地絡電流とは逆位相の逆位相電流を作成する逆位相電流作成手段と、前記作成された逆位相電流を前記電力配電線に供給する逆位相電流供給手段とを具え、前記供給された逆位相電流によって前記地絡電流を抑制するようにすることによって、地絡抑制システムを構成する。
【００２９】
また、本発明によれば、共通の母線に接続された複数回線の配電線を備える電力配電線における地絡電流を抑制するものであって、前記電力配電線の零相電圧を検出する零相電圧検出工程および前記配電線の各零相電流を検出する零相電流検出手段を具えるとともに、前記零相電圧および前記零相電流検出工程により検出された電流に基づいて地絡事故を検出する地絡事故検出工程と、前記零相電流検出工程により検出された電流に基づいて健全回線を判別する健全回線判別工程と、前記判別された健全回線の零相電流のベクトル和に基づいて近似地絡電流を算出する近似地絡電流算出工程と、前記算出された近似地絡電流とは逆位相の逆位相電流を作成する逆位相電流作成工程と、前記作成された逆位相電流を前記電力配電線に供給する逆位相電流供給工程とを具え、前記供給された逆位相電流によって前記地絡電流を抑制するようにすることによって、地絡抑制方法を構成する。
【００３０】
また、かかる構成において、前記健全回線の零相電流のベクトル和の算出は、地絡事故発生直後の過渡状態を経過した後の前記健全回線の零相電流に対して行うようにするとよい。
【００３１】
【発明の実施の形態】
以下、図面を参照して、本発明の実施の形態を詳細に説明する。
【００３２】
（システム構成）
図１は、本発明を表す地絡抑制システムの構成例を示す。
【００３３】
配電変電所１の構内において、２は電源（電源用変圧器）である。この電源２の出力側は、母線３ａ〜３ｃを介して、配電線４ａ〜４ｃ，５ａ〜５ｃ、６ａ〜６ｃと接続されている。
【００３４】
母線３ａ〜３ｃには、零相電圧Ｖｏを検出する接地形計器用変圧器（ＧＶＴ）からなる零相変圧器８が接続されている。配電線４ａ〜４ｃ，５ａ〜５ｃ，６ａ〜６ｃには、零相変流器７ａ〜７ｃが接続されている。
【００３５】
１０は、配電線４ａ〜４ｃ，５ａ〜５ｃ、あるいは６ａ〜６ｃのうちの事故配電線に流れる近似地絡電流Ｉ_g3（＝Ｉ₀₂＋Ｉ₀₃）を検出する地絡電流検出手段としての地絡事故検出装置である。なお、図１は配電線４ａ〜４ｃが事故配電線となった場合を示している。この地絡事故検出装置１０の入力側は、零相変流器７ａ〜７ｃ，零相変圧器８と、計器用変圧器９ａ〜９ｃとが接続されている。また、地絡事故検出装置１０の出力側は、逆位相波形発生装置２０と、系統並入用の開閉器４１とが接続されている。
【００３６】
２０は、近似地絡電流Ｉ_g3と逆位相の逆位相電流Ｉ_v （＝−Ｉ_g3）を発生する逆位相電流発生手段としての逆位相波形発生装置である。この逆位相波形発生装置２０の入力側は、地絡事故検出装置１０の出力側と接続されている。また、逆位相波形発生装置２０の出力側は、注入用変圧器４０と接続されている。
【００３７】
また、配電変電所１から引き出された配電線４ａ〜４ｃ，５ａ〜５ｃ，６ａ〜６ｃには、各々負荷３０, ３１，３２が接続されている。Ｃ₀₁は、配電線４ａ〜４ｃの各相と大地との間の対地静電容量である。Ｃ₀₂は、配電線５ａ〜５ｃの各相と大地との間の対地静電容量である。Ｃ₀₃は、配電線６ａ〜６ｃの各相と大地との間の対地静電容量である。
【００３８】
図２は、地絡事故検出装置１０の内部構成を示す。この装置１０には、各種信号が入力される入力部１１と、地絡事故を検出するための事故検出部１２と、地絡事故の発生した相と、地絡事故の発生していない健全な配電線とを検出する比較部１３と、地絡相への系統並入用の開閉器４１の投入指令を発生させる開閉器投入指令部１４と、逆位相波形発生装置２０への入力となる近似地絡電流Ｉ_g3を算出するための演算部１５と、系統並入用の開閉器４１への投入指令と近似地絡電流Ｉ_g3とを出力する出力部１６とから構成されている。
【００３９】
図３は、逆位相波形発生装置２０の内部構成を示す。この装置２０は、逆位相電流発生指令が入力される入力部２１と、入力信号波形と同じ位相波形を生成する波形生成部２２と、生成した波形を反転させる波形反転部２３と、逆位相電流Ｉ_v を出力する出力部２４とから構成されている。
【００４０】
（地絡電流抑制動作）
次に、地絡抑制システムの動作について説明する。
【００４１】
いま、配電線４ａ〜４ｃのうち、ｃ相の配電線４ｃに地絡故障が発生したとする。この場合、母線３ａには、配電線４ａ〜４ｃのうち、ａ相の配電線４ａから対地静電容量Ｃ₀₁に基づく零相電流ｉ₀₁と、配電線５ａ〜５ｃのうち、ａ相の配電線５ａから対地静電容量Ｃ₀₂に基づく零相電流ｉ₀₂と、配電線６ａ〜６ｃのうち、ａ相の配電線６ａから対地静電容量Ｃ₀₃に基づく零相電流ｉ₀₃と、零相変圧器８の接地中性線８ａからの地絡抵抗分電流のうち、ａ相に流れる分Ｉ_raとの合成電流が破線矢印のごとく流れる。
【００４２】
母線３ｂには、配電線４ａ〜４ｃのうち、ｂ相の配電線４ｂから対地静電容量Ｃ₀₁に基づく零相電流ｉ₀₁と、配電線５ａ〜５ｃのうち、ｂ相の配電線５ｂから対地静電容量Ｃ₀₂に基づく零相電流ｉ₀₂と、配電線６ａ〜６ｃのうち、ｂ相の配電線６ｂから対地静電容量Ｃ₀₃に基づく零相電流ｉ₀₃と、零相変圧器８の接地中性線８ａからの地絡抵抗分電流のうち、ｂ相に流れる分Ｉ_rbとの合成電流が破線矢印のごとく流れる。
【００４３】
母線３ｃには、配電線５ａ〜５ｃのうち、ｃ相の配電線５ｃから対地静電容量Ｃ₀₂に基づく零相電流ｉ₀₂と、配電線６ａ〜６ｃのうち、ｃ相の配電線６ｃから対地静電容量Ｃ₀₃に基づく零相電流ｉ₀₃と、零相変圧器８の接地中性線８ａからの地絡抵抗分電流のうち、ｃ相に流れる分Ｉ_rcとの合成電流が破線矢印のごとく流れる。
【００４４】
母線３ａ〜３ｃに流れる零相電流と抵抗分電流との合成電流は、最終的には、事故配電線４ａ〜４ｃの事故相４ｃの地絡点Ｇに破線矢印のごとく流れ込む。すなわち、母線３ａ，３ｂに流れる零相電流と抵抗分電流の各合成電流は、破線矢印のごとく電源２を介して母線３ｃに流れ、再度、合成電流となり、事故回線４ａ〜４ｃの事故相４ｃに流れ、地絡点Ｇに流れていく。
【００４５】
一方、地絡事故時には、母線３ａ〜３ｃの各相電圧が不平衡となり、零相変圧器８において零相電圧Ｖｏが検出され、また、配電線５ａ〜５ｃ，６ａ〜６ｃの各零相変流器７ｂ，７ｃにおいて各零相電流Ｉ₀₂，Ｉ₀₃が検出される。配電線４ａ〜４ｃの零相変流器７ａでは、零相変流器７ｂ，７ｃで検出された零相電流Ｉ₀₂，Ｉ₀₃と零相変圧器８の接地中性線８ａからの地絡抵抗分電流Ｉ_ra，Ｉ_rb，Ｉ_rcとの合成電流Ｉ_g2が検出される。これら検出された零相電圧Ｖｏ、零相電流Ｉ₀₂，Ｉ₀₃およびＩ_g2から、地絡事故検出装置１０において地絡事故が発生したことを判別することができる。
【００４６】
また、地絡事故検出装置１０では、母線３ａ〜３ｃに接続された計器用変圧器９ａ〜９ｃで検出される各相の相電圧Ｖａ〜Ｖｃを比較することによって、地絡相を容易に判別することができる。
【００４７】
なお、各健全回線の各相を流れる零相電流ｉ₀₂，ｉ₀₃と各健全回線の零相電流Ｉ₀₂，Ｉ₀₃、および地絡回線の零相変流器で検出される電流Ｉ_g2との関係は、次のようになっている。
【００４８】
【数２】
Ｉ_g2＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_ra＋Ｉ_rb＋Ｉ_rc …（２）
【００４９】
【数３】
Ｉ₀₂＝３ｉ₀₂ …（３）
【００５０】
【数４】
Ｉ₀₃＝３ｉ₀₃ …（４）
ここで、図２に示す地絡事故検出装置１０の内部処理を詳細に説明する。
【００５１】
入力部１１には、零相電圧Ｖｏと、各零相変流器で検出される電流Ｉ₀₂，Ｉ₀₃，Ｉ_g2と、各相の相電圧Ｖａ〜Ｖｃとが入力される。事故検出部１２では、零相電圧Ｖｏと各零相変流器で検出される電流Ｉ₀₂，Ｉ₀₃，Ｉ_g2の両方の大きさを見て、両方とも変化が生じたとき（ＡＮＤ条件）に地絡事故と判断する。この判断時における零相変流器で検出される電流は、少なくとも１つの大きさを見ればよい。
【００５２】
このようにして地絡事故の検出が認められた場合、比較部１３において各相の相電圧Ｖａ〜Ｖｃの大きさを比較して、最も小さい値の相を地絡相と判別する。
【００５３】
また、比較部１３では、零相電圧と、零相変流器で検出される電流Ｉ₀₂，Ｉ₀₃，Ｉ_g2の大きさおよび位相差により、地絡回線と健全回線とを区別することによって、近似地絡電流Ｉ_g2と、健全回線に流れる零相電流Ｉ₀₂，Ｉ₀₃とを区別する。なお、この判別方法としては、配電系統に一般的に使用されている方向継電器と同じ原理を用いる。また、各零相変流器で検出される電流はそのピーク値同士を比較して、ピーク値が最大の回線を地絡回線と判別する。
【００５４】
開閉器投入指令部１４では、比較部１３から出力された地絡相判別信号を受け、注入用変圧器４０を地絡相に連係する開閉器４１への投入指令信号Ｉｔを出力する。
【００５５】
一方、演算部１５では、比較部１３によって判別された健全回線５ａ〜５ｃ，６ａ〜６ｃの零相電流Ｉ₀₂，Ｉ₀₃に基づいてべクトル和を求めて近似地絡電流Ｉ_g3を算出する。このベクトル和は、瞬時値を加算することによって求められる。
【００５６】
また、ベクトル和の演算は、地絡事故を検出した後の健全回線５ａ〜５ｃ，６ａ〜６ｃの零相電流Ｉ₀₂，Ｉ₀₃に対して実施するとよく、また、過渡状態を経過した後の健全回線５ａ〜５ｃ，６ａ〜６ｃの零相電流Ｉ₀₂，Ｉ₀₃に対して実施するようにしてもよい。
【００５７】
なお、この過渡状態を経過した後の健全回線の零相電流に対してベクトル和の演算を行う場合に、地絡事故検出装置１０内にタイマー機能を設けておいて、地絡事故検出後から所定の時間、例えば１００ｍｓ程度経過した後の健全回線の零相電流の和に対して実施するようにすることができる。
【００５８】
また、地絡事故を検出した後の過渡状態において検出される健全回線の零相電流は不規則な波形で、かつ、高周波成分を有するものとなっているが、過渡状態を経過した後で検出される健全回線の零相電流は安定した波形であり、かつ過渡状態におけるほど高い高周波成分を有するものではないため、その信号処理は容易となる。従って、上記のような、過渡状態を経過した後の健全回線の零相電流に対してベクトル和の演算を行うという構成とすることにより、過渡期間をマスキングすることによって地絡事故検出後の例えば１００ｍｓ程度の多少の時間は無駄時間となるものの、健全回線の零相電流に対する信号処理手段を簡素な構成とすることができるため、地絡抑制システムの低コスト化が可能となる。
【００５９】
このようにして算出した近似地絡電流Ｉ_g3は、出力部１６を介して逆位相波形発生装置２０へと出力され、一方、投入指令信号Ｉｔは出力部１６を介して系統並入用の開閉器４１へと出力される。
【００６０】
逆位相波形発生装置２０において、入力部２１には、近似地絡電流Ｉ_g3が入力される。波形生成部２２では、入力された近似地絡電流信号と同じ電流波形を随時生成する。波形反転部２３では、波形生成部２２で生成した電流波形に、地絡電流に対して逆位相となるように、反転処理を施す。このようにして生成した逆位相電流Ｉ_v は、出力部２４から注入用変圧器４０に出力される。
【００６１】
そして、注入用変圧器４０に出力された逆位相電流Ｉ_v は、実線矢印のごとく母線３ｃを経て、地絡回線４ａ〜４ｃの地絡相４ｃに流れ、地絡点Ｇに流れ込み、地絡電流Ｉ_g を抑制する。
【００６２】
なお、上述の図１の地絡抑制システムにおいて、注入用変圧器４０と並列に数Ωの抵抗を有する誤動作時保護用抵抗回路４２が設けられている。図１のシステムにおいて万一地絡相の誤判別により注入用変圧器４０が健全相に接続された場合でも、上記の抵抗回路４２の抵抗が配電系統側で注入用変圧器４０の変圧比の２乗に比例して作用することにより、異相地絡短絡による短絡電流を小さくすることができる。
【００６３】
（地絡電流抑制原理）
次に、地絡電流抑制原理を、図４および図５に基づいて具体的に説明する。
【００６４】
図４は、地絡電流Ｉ_g を抑制する等価回路を示す。なお，ここでは、前述した図６の等価回路と比較して説明するため、同一部分には同一符号を用いる。
【００６５】
地絡電流Ｉ_g の抑制動作は、次のようになる。
【００６６】
（１）地絡電流Ｉ_g のうちの、各健全回線１０２，１０３に流れる零相電流Ｉ₀₂，Ｉ₀₃の和と接地形計器用変圧器（ＧＶＴ）からなる零相変圧器の一次側接地中性線１０４から流れる抵抗分電流Ｉ_RNとの合成電流Ｉ_g2（＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN）と逆位相電流Ｉ_v との残差（＝Ｉ_g2＋Ｉ_v ＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN＋Ｉ_v ）はモニタせず、各健全回線の零相電流の和Ｉ_g3（＝Ｉ₀₂＋Ｉ₀₃）のみをモニタする。
【００６７】
（２）各健全回線の零相電流の和Ｉ_g3（＝Ｉ₀₂＋Ｉ₀₃）に従って逆位相電流Ｉ_v を生成し、配電系統に注入する。
【００６８】
（３）地絡電流Ｉ_g （＝Ｉ₀₁＋Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN）のうち、各健全回線の零相電流の和Ｉ_g3（＝Ｉ₀₂＋Ｉ₀₃）の分を抑制することにより、地絡電流Ｉ_g を抑制する。
【００６９】
（４）各健全回線の零相電流は、地絡事故原因が除去されない限り流れ続けるため、地絡電流Ｉ_g と逆位相電流Ｉ_v との残差が小さくなっても、逆位相電流Ｉ_v の生成・注入量は減少せず、安定的に地絡電流を抑制する。
【００７０】
図５は、本発明による地絡電流Ｉ_g の抑制原理を示すベクトル図であって、図５（ａ）は逆位相波形発生装置を適用しない場合の通常の地絡状態、図５（ｂ）は図５（ａ）の状態において逆位相波形発生装置を適用した場合の状態を示すものである。図５（ａ）に示される各健全回線の零相電流Ｉ₀₂，Ｉ₀₃が図４の等価回路の零相変流器１０８，１０９によりそれぞれ検出され、その和Ｉ_g3（＝Ｉ₀₂＋Ｉ₀₃）が常にモニタされている。このＩ_g3に従って図５（ｂ）に示されるように逆位相電流Ｉ_V （＝−Ｉ_g3）が生成、注入されることにより、地絡電流Ｉ_g のうち、Ｉ_g3の分が抑制され、地絡電流Ｉ_g も抑制される。
【００７１】
なお、地絡電流Ｉ_g と各回線の零相電流および零相電圧器の一次側接地中性線で流れる抵抗分電流との関係についてもう一度整理しておくと次の通りである。
【００７２】
【数５】

ここで、 Ｉ_g1＝Ｉ₀₁
Ｉ_g2＝Ｉ_g3＋Ｉ_RN
Ｉ_g3＝Ｉ₀₂＋Ｉ₀₃
Ｉ₀₁：地絡回線１０１自身で流れる零相電流であり、零相変流器で
は検出できない電流である。
【００７３】
Ｉ₀₂：健全回線１０２で流れる零相電流。
【００７４】
Ｉ₀₃：健全回線１０３で流れる零相電流。
【００７５】
Ｉ_RN：零相変圧器の一次側接地中性線１０４で流れる抵抗分電流
以上のように、本発明による地絡抑制システムおよび地絡抑制方法では、従来のように地絡回線に流れる地絡電流Ｉ_g のうちの、各健全回線に流れる零相電流と零相変圧器の一次側接地中性線から流れる抵抗分電流Ｉ_RNとの合成電流Ｉ_g2（＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN）と逆位相電流Ｉ_V との残差（＝Ｉ_g2＋Ｉ_V ＝Ｉ₀₂＋Ｉ₀₃＋Ｉ_RN＋Ｉ_V ）をモニタするのではなく、各健全回線の零相電流の和Ｉ_g3（＝Ｉ₀₂＋Ｉ₀₃）のみをモニタするようにしているため、地絡電流Ｉ_g を復帰させることなく安定的に抑制することが可能となる。
【００７６】
なお、図１の構成例では、上述のように、電力配電線と注入用変圧器４０との間に開閉器４１を設け、地絡事故検出装置１０からの開閉器投入信号Ｉｔによる開閉器４１の投入操作によって注入用変圧器２０を地絡相に連系する構成としているが、本発明による地絡抑制システムの構成は上記に限定されるものではなく、電力配電線の任意の相に注入用変圧器４０を接続しておく構成としてもよい。このような構成とすれば、注入用変圧器４０を連系させる相を選択するのにかかるステップを省略できるので、地絡事故検出装置１０の構成を簡素化することができる。
【００７７】
【発明の効果】
以上説明したように、本発明によれば、健全回線の零相電流のベクトル和に基づいて近似地絡電流を算出し、その算出された近似地絡電流とは逆位相の逆位相電流を電力配電線に供給するようにしたので、地絡電流を復帰させることなく常に安定的に抑制することができ、地絡アークが消弧し易い地絡抑制システムおよび地絡抑制方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態である地絡抑制システムを示す構成図である。
【図２】地絡事故検出装置の回路構成を示すブロック図である。
【図３】逆位相波形発生装置の回路構成を示すブロック図である。
【図４】本発明による地絡電流抑制原理を示す回路図である。
【図５】本発明による地絡電流抑制原理を示すベクトル図であって、（ａ）は逆位相波形発生装置を適用しない場合の通常の地絡状態、（ｂ）は図５（ａ）の状態において逆位相波形発生装置を適用した場合の状態を示す。
【図６】従来における地絡電流抑制原理を示す回路図である。
【図７】従来における地絡電流抑制原理を示すベクトル図であって、（ａ）は逆位相波形発生装置を適用しない場合の通常の地絡状態、（ｂ）は図７（ａ）の状態において逆位相波形発生装置を適用した場合のある時点での状態、（ｃ）は図７（ａ）の状態において逆位相波形発生装置を適用した場合の図７（ｂ）とは異なる時点での状態を示す。
【符号の説明】
１ 配電変電所
２ 電源（電源用変圧器）
３ａ〜３ｃ 母線
４ａ〜４ｃ 配電線（事故配電線）
５ａ〜５ｃ 配電線（健全配電線）
６ａ〜６ｃ 配電線（健全配電線）
７ａ〜７ｃ 零相変流器
８ 零相変圧器
８ａ 零相変圧器の一次側接地中性線
９ａ〜９ｃ 計器用変圧器
１０ 地絡事故検出装置
２０ 逆位相波形発生装置
３０〜３２ 配電線負荷
４０ 注入用変圧器
４１ 系統並入用開閉器
４２ 誤動作時保護用抵抗回路
Ｉ_g 地絡電流
Ｉ_V 逆位相電流
Ｖ₀ 零相電圧
Ｉ_g2，Ｉ₀₂，Ｉ₀₃ 配電線４ａ〜４ｃ，５ａ〜５ｃ，６ａ〜６ｃの各零相変流器で検出される電流[0001]
BACKGROUND OF THE INVENTION
The present invention suppresses a ground fault itself by suppressing a ground fault current caused by a ground fault in an instantaneous ground fault or a permanent ground fault generated in a power distribution line, and further, electrical equipment technical standards It relates to a ground fault suppression system and a ground fault suppression method for reducing the grounding resistance value by the class B grounding work defined in the above.
[0002]
[Prior art]
Conventionally, when a ground fault occurs in a power distribution system, a ground fault current flows through the distribution line. As a countermeasure against this ground fault, in the normal case, a ground fault is detected by a zero-phase transformer, a relay that detects a fault line by a zero-phase current transformer operates, and a distribution line breaker (distribution line CB) is installed. A reclosing operation is performed in which the distribution line is brought into a non-voltage state and the distribution line CB is closed after one minute, and power is retransmitted to the distribution line.
[0003]
However, when an instantaneous ground fault occurs due to a temporary contact between a distribution line and a conductive material, it is not a permanent ground fault and ground fault accidents are often eliminated. If the reclosing operation is performed in the case of such an instantaneous ground fault, a power failure is caused, so that the reliability of power supply is remarkably lowered.
[0004]
Therefore, in the case of an instantaneous ground fault, before the distribution line CB operates, a method of instantaneously diverting the ground fault current from the distribution line by the forced grounding device, or a part of the ground fault current by installing an arc extinguishing reactor A method has been devised in which the ground fault current is suppressed and the distribution line CB is not operated by the method of canceling out.
[0005]
However, the method of bypassing the ground fault current (providing a bypass circuit in the power transmission side power supply) does not reduce the current value of the ground fault current. In addition, a grounding resistance corresponding to the ground fault current value is required, and a large construction cost is required.
[0006]
In addition, a method for canceling a part of the ground fault current by providing an arc extinguishing reactor (providing an LC resonance circuit in which a coil L is inserted into a capacitor C) requires a grounding point on the power transmission side. The form on the power transmission side is limited.
[0007]
Furthermore, even if an arc extinguishing reactor is used, the fundamental wave component of the ground fault current based on the ground capacitance can be canceled, and it is the principle to cancel all of the ground fault current including the resistance current and the harmonic current. This is impossible, and the remaining ground fault current becomes a problem.
[0008]
Further, when the ground capacitance changes due to the change in the distribution line length, the current compensation rate changes if the reactor capacity is constant.
[0009]
[Problems to be solved by the invention]
Therefore, as a ground fault suppression system and a ground fault suppression method that has no dependency on the power transmission form, can suppress additional facilities at low cost, and can suppress the ground fault current, a current having a phase opposite to that of the ground fault current is injected. Thus, an anti-phase current injection method for suppressing the ground fault current has been devised.
[0010]
However, in the reverse phase current injection method, when the current detected in the zero phase variable flow path of the ground fault line as an approximate ground fault current is input to the reverse phase waveform generator, Input / output is performed on the same ground fault line.
[0011]
Therefore, the input to the anti-phase waveform generator results in a residual between the ground fault current and the anti-phase current.
[0012]
For this reason, it repeats that ground fault current will be returned if it is suppressed, and it will be suppressed if it recovers, and since the ground current returns, there will be a problem that it is difficult to extinguish the ground fault arc.
[0013]
Here, the conventional ground fault current suppression principle will be described with reference to FIGS.
[0014]
Figure 6 shows a suppressing equivalent circuit ground fault current I _g. Reference numeral 100 denotes an equivalent power source. 101 is a ground fault line. Reference numerals 102 and 103 are sound lines. C1, C2 and C3 are ground capacitances of the ground fault line 101 and the sound lines 102 and 103, respectively. 104 Grounded potential transformer; a primary side ground neutral line of zero-phase transformer comprising a (GVT Grounding Voltage Transformer), the resistor R _N is converted primary side Aru limiting resistor provided in the zero-phase transformer Equivalent resistance. Reference numeral 105 denotes a ground fault detection device. 106 is the reverse phase waveform generator for generating a reverse phase current I _V suppresses the ground fault current I _g. Reference numeral 107 denotes an equivalent zero-phase current transformer corresponding to the zero-phase current transformer installed in the ground fault line 101, and reference numerals 108 and 109 denote zero-phase current transformers installed in the sound lines 102 and 103. Note that the zero-phase current transformer of the ground fault line 101 cannot detect the current for its own line due to its characteristics.
[0015]
The current detected by the zero-phase current transformer 108 of the healthy line 102 is the zero-phase current I ₀₂ , and the current detected by the zero-phase current transformer 109 of the healthy line 103 is the zero-phase current I ₀₃ . Further, a resistance current I _RN flows through the primary-side ground neutral line 104 of the zero-phase transformer. On the other hand, the current detected by the original zero-phase current transformer of the ground fault line 101 is a vector sum of I ₀₂ , I ₀₃ and I _RN .
[0016]
Here, the zero-phase current generated in the ground fault line 101 of the ground fault current is I _g1 (= I ₀₁ ), the healthy lines 102 and 103 of the ground fault current, and the primary side ground neutrality of the zero-phase transformer. If the current generated from the line 104 is I _g2 (= I ₀₂ + I ₀₃ + I _RN ), and the current generated only from the sound lines 102 and 103 of the ground fault current is I _g3 (= I ₀₂ + I ₀₃ ), ground fault current I _g is,
[0017]
[Expression 1]

It becomes.
[0018]
Next, the ground fault current suppression operation is as follows.
[0019]
1. In the equivalent zero-phase current transformer 107 of the ground fault line 101, an inflow I _{g2 of} the ground fault current I _g from the healthy line and the primary-side ground neutral line of the zero-phase transformer and the antiphase current I _V A residual ΔI _g2 (= I _g2 + I _V ) is detected.
[0020]
2. Residual [Delta] I _g2 the detected, through ground fault detector 105, are input to the opposite phase waveform generator 106, where generating the anti-phase current I _V in response to the residual [Delta] I _g2, injected.
[0021]
3. At the beginning of the injection of the anti-phase current I _V , the residual ΔI _g2 becomes small, and the generation / injection amount of the anti-phase current I _V at the next time point decreases.
[0022]
4). When the ground fault continues, the residual ΔI _g2 increases again by the amount corresponding to the decrease in the antiphase current _IV .
[0023]
The processing of 5.1 to 4 is repeated, and the suppression rate settles down at a certain level.
[0024]
In this way, the combined current I _g2 (= I ₀₂ + I ₀₃ + I _RN ) of the zero-phase current of the sound line in the ground fault current and the inflow from the primary-side ground neutral line of the zero-phase transformer is reduced. To do. Accordingly, the ground fault current I _g (= I _g1 + I _g2 ) is also reduced accordingly.
[0025]
Figure 7 is a vector diagram showing the principle of suppressing the ground fault current I _g in prior art, FIG. 7 (a) in the case of not applying the antiphase waveform generator normal ground fault state, FIG. 7 (b) FIG. 7A shows a state at a certain time when the antiphase waveform generator is applied in the state of FIG. 7A, and FIG. 7C shows the state when the antiphase waveform generator is applied in the state of FIG. It shows a state at a different time from (b). The residual ΔI _g2 (= I _g2 + I _v ) is constantly monitored by the zero-phase current transformer 107 in FIG. At the beginning of the ground fault, the residual ΔI _g2 is equal to I _g2 , and a corresponding antiphase current I _v (= −ΔI _g2 ) is generated and injected (see FIGS. 7A and 7B). After injection, as shown in FIG. 7 (b), the residual [Delta] I _g2 decreases, correspondingly grounding current I _g is also suppressed. However, since the residual ΔI _g2 is constantly monitored, the antiphase current I _V becomes a small current as shown in FIG. 7C at the next moment. Further, since the currents I ₀₂ , I ₀₃ , and I _RN tend to flow as before, I _g2 (= I ₀₂ + I ₀₃ + I _RN ) tries to return to the original size. Therefore, the effect of suppressing I _g2 is reduced, and the effect of suppressing the ground fault current I _g (= I _g1 + I _g2 ) is also reduced.
[0026]
Such FIG. 7 (b), the by repeating the operations of (c), as described above, and the ground fault current I _g is restored, ground fault arc remains a problem that extinguishing to hesitation.
[0027]
Therefore, an object of the present invention is to provide a ground fault suppression system and a ground fault suppression method that stabilizes the antiphase current injected into the system, prevents the return of the ground fault current, and easily extinguishes the ground fault arc. .
[0028]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a ground fault current in a power distribution line including a plurality of distribution lines connected to a common bus is suppressed, and the zero phase of the power distribution line is provided. A zero-phase voltage detecting means for detecting voltage and a zero-phase current detecting means for detecting each zero-phase current of the distribution line are provided, and a healthy line is discriminated based on the current detected by the zero-phase current detecting means. Healthy line discrimination means, approximate ground fault current calculation means for calculating an approximate ground fault current based on a vector sum of the determined zero phase currents of the healthy line, and the calculated approximate ground fault current having an opposite phase An anti-phase current generating means for generating an anti-phase current; and an anti-phase current supplying means for supplying the generated anti-phase current to the power distribution line, and the ground fault current is generated by the supplied anti-phase current. To suppress By Rukoto, constitute a ground 絡抑 control systems.
[0029]
Further, according to the present invention, a ground fault current in a power distribution line including a plurality of distribution lines connected to a common bus is suppressed, and a zero phase for detecting a zero phase voltage of the power distribution line A zero-phase current detection means for detecting each zero-phase current of the voltage detection step and the distribution line is provided, and a ground fault is detected based on the zero-phase voltage and the current detected by the zero-phase current detection step. A ground fault detection step, a healthy line discrimination step for discriminating a healthy line based on the current detected by the zero phase current detection step, and an approximate ground based on a vector sum of the zero phase current of the discriminated healthy line. An approximate ground fault current calculating step for calculating a fault current, a reverse phase current generating step for generating a reverse phase current having a phase opposite to that of the calculated approximate ground fault current, and the generated reverse phase current for the power distribution. Reverse supply to electric wire Comprising a phase current supplying step, by so as to suppress the ground fault current by the supplied antiphase current, constitutes the land 絡抑 system method.
[0030]
In this configuration, the calculation of the vector sum of the zero-phase current of the healthy line may be performed on the zero-phase current of the healthy line after a transient state immediately after the occurrence of the ground fault.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0032]
(System configuration)
FIG. 1 shows a configuration example of a ground fault suppression system representing the present invention.
[0033]
In the premises of the distribution substation 1, reference numeral 2 denotes a power source (power transformer). The output side of the power source 2 is connected to the distribution lines 4a to 4c, 5a to 5c, and 6a to 6c via buses 3a to 3c.
[0034]
Connected to the buses 3a to 3c is a zero-phase transformer 8 composed of a grounded instrument transformer (GVT) for detecting the zero-phase voltage Vo. Zero-phase current transformers 7a to 7c are connected to the distribution lines 4a to 4c, 5a to 5c, and 6a to 6c.
[0035]
10 is a ground fault as a ground fault current detecting means for detecting an approximate ground fault current I _g3 (= I ₀₂ + I ₀₃ ) flowing through the fault distribution line among the distribution lines 4a to 4c, 5a to 5c, or 6a to 6c. Accident detection device. In addition, FIG. 1 has shown the case where the distribution lines 4a-4c become accident distribution lines. Zero-phase current transformers 7a to 7c, a zero-phase transformer 8 and instrument transformers 9a to 9c are connected to the input side of the ground fault detector 10. The output side of the ground fault detection device 10 is connected to an antiphase waveform generator 20 and a switch 41 for system entry.
[0036]
Reference numeral 20 denotes an anti-phase waveform generator as anti-phase current generating means for generating an anti-phase current I _v (= −I _g3 ) having a phase opposite to that of the approximate ground fault current I _g3 . The input side of the antiphase waveform generator 20 is connected to the output side of the ground fault detector 10. The output side of the antiphase waveform generator 20 is connected to the injection transformer 40.
[0037]
In addition, loads 30, 31 and 32 are connected to the distribution lines 4a to 4c, 5a to 5c, and 6a to 6c drawn from the distribution substation 1, respectively. C ₀₁ is a ground capacitance between each phase of the distribution lines 4a to 4c and the ground. C ₀₂ is a capacitance to ground between the phases and ground distribution lines bodies 5a to 5c. C ₀₃ is a capacitance to ground between the phases and ground distribution lines 6 a to 6 c.
[0038]
FIG. 2 shows the internal configuration of the ground fault detection device 10. The device 10 includes an input unit 11 to which various signals are input, an accident detection unit 12 for detecting a ground fault, a phase in which a ground fault has occurred, and a healthy state in which no ground fault has occurred. The comparison unit 13 for detecting the distribution line, the switch input command unit 14 for generating the input command of the switch 41 for system parallel insertion to the ground fault phase, and the approximation to be input to the antiphase waveform generator 20 an arithmetic unit 15 for calculating the ground fault current I _g3, and an output unit 16 for outputting the approximation grounding current I _g3 and closing command to the switch 41 of the system parallel necessity.
[0039]
FIG. 3 shows the internal configuration of the antiphase waveform generator 20. This device 20 includes an input unit 21 to which an antiphase current generation command is input, a waveform generation unit 22 that generates the same phase waveform as the input signal waveform, a waveform inversion unit 23 that inverts the generated waveform, and an antiphase current And an output unit 24 for outputting I _v .
[0040]
(Ground fault current suppression operation)
Next, the operation of the ground fault suppression system will be described.
[0041]
It is assumed that a ground fault has occurred in the c-phase distribution line 4c among the distribution lines 4a to 4c. In this case, the bus 3a, of the distribution lines 4 a to 4 c, the zero-phase current i ₀₁ based on the earth capacitance C ₀₁ from the power distribution line 4a of a phase, of the distribution line bodies 5a to 5c, distribution of a phase The zero-phase current i ₀₂ based on the ground capacitance C ₀₂ from the wire 5a, and the zero-phase current i ₀₃ based on the ground capacitance C ₀₃ from the a-phase distribution wire 6a among the distribution wires 6a to 6c, and the zero-phase Of the ground fault resistance current from the ground neutral line 8a of the transformer 8, the combined current with the amount I _ra flowing in the a phase flows as indicated by the broken line arrow.
[0042]
The bus 3b, of the distribution lines 4 a to 4 c, the zero-phase current i ₀₁ based on the earth capacitance C ₀₁ from b-phase distribution line 4b, of the distribution line bodies 5a to 5c, the b-phase distribution line 5b A zero-phase current i ₀₂ based on the ground capacitance C ₀₂ and a zero-phase current i ₀₃ based on the ground capacitance C ₀₃ from the b-phase distribution wire 6b among the distribution wires 6a to 6c, and the zero-phase transformer 8 Of the ground fault resistance component current from the ground neutral wire 8a, the combined current with the component I _rb flowing in the b phase flows as indicated by the broken arrow.
[0043]
The bus 3c, of the distribution line bodies 5a to 5c, the zero-phase current i ₀₂ based on the earth capacitance C ₀₂ from the power distribution line 5c of the c-phase, out of the distribution line 6 a to 6 c, the distribution line 6c of the c-phase The combined current of the zero-phase current i ₀₃ based on the capacitance to ground C ₀₃ and the component I _rc that flows in the c-phase of the ground-fault resistance current from the ground neutral line 8a of the zero-phase transformer 8 is a dashed arrow It flows like
[0044]
The combined current of the zero-phase current flowing through the buses 3a to 3c and the resistance-divided current finally flows into the ground fault point G of the accident phase 4c of the accident distribution lines 4a to 4c as indicated by the broken arrow. That is, each combined current of the zero-phase current and the resistance-divided current flowing in the buses 3a and 3b flows to the bus 3c via the power source 2 as indicated by the broken line arrow, and becomes a combined current again, and the accident phase 4c of the fault lines 4a to 4c To the ground fault point G.
[0045]
On the other hand, at the time of the ground fault, the phase voltages of the buses 3a to 3c become unbalanced, the zero phase voltage Vo is detected by the zero phase transformer 8, and the zero phase changes of the distribution lines 5a to 5c and 6a to 6c are detected. The zero phase currents I ₀₂ and I ₀₃ are detected in the flow devices 7b and 7c. In the zero-phase current transformer 7a of the distribution lines 4a to 4c, the zero-phase currents I ₀₂ and I ₀₃ detected by the zero-phase current transformers 7b and 7c and the ground fault from the ground neutral line 8a of the zero-phase transformer 8 are detected. A combined current I _g2 with the resistance currents I _ra , I _rb and I _rc is detected. From the detected zero-phase voltage Vo, zero-phase currents I ₀₂ , I ₀₃ and _{Ig 2} , it can be determined that a ground fault has occurred in the ground fault detection device 10.
[0046]
Further, in the ground fault detection device 10, the ground fault phase can be easily determined by comparing the phase voltages Va to Vc of the respective phases detected by the instrument transformers 9a to 9c connected to the buses 3a to 3c. can do.
[0047]
The zero-phase currents i ₀₂ and i ₀₃ flowing through each phase of each healthy line, the zero-phase currents I ₀₂ and I _{03 of} each healthy line, and the current I _g2 detected by the zero-phase current transformer of the ground fault line and The relationship is as follows.
[0048]
[Expression 2]
I _g2 = I ₀₂ + I ₀₃ + I _ra + I _rb + I _rc (2)
[0049]
[Equation 3]
I ₀₂ = 3i ₀₂ (3)
[0050]
[Expression 4]
I ₀₃ = 3i ₀₃ (4)
Here, the internal processing of the ground fault detection apparatus 10 shown in FIG. 2 will be described in detail.
[0051]
The input unit 11 receives a zero-phase voltage Vo, currents I ₀₂ , I ₀₃ , and Ig ₂ detected by each zero-phase current transformer, and phase voltages Va to Vc of each phase. The accident detector 12 looks at the magnitudes of both the zero-phase voltage Vo and the currents I ₀₂ , I ₀₃ , and I _g2 detected by each zero-phase current transformer, and when both change (AND condition) Judged to be a ground fault. The current detected by the zero-phase current transformer at the time of this determination may be at least one magnitude.
[0052]
When a ground fault is detected in this way, the comparison unit 13 compares the phase voltages Va to Vc of the respective phases, and determines the phase having the smallest value as the ground fault phase.
[0053]
Further, the comparison unit 13 distinguishes the ground fault line and the healthy line from the zero phase voltage and the magnitudes and phase differences of the currents I ₀₂ , I ₀₃ , and Ig ₂ detected by the zero phase current transformer. The approximate ground current I _g2 is distinguished from the zero-phase currents I ₀₂ and I ₀₃ flowing through the healthy line. In addition, as this discrimination method, the same principle as the direction relay generally used for the distribution system is used. Moreover, the current detected by each zero-phase current transformer compares the peak values thereof, and determines the line having the maximum peak value as a ground fault line.
[0054]
The switch input command unit 14 receives the ground fault phase determination signal output from the comparison unit 13 and outputs the input command signal It to the switch 41 that links the injection transformer 40 to the ground fault phase.
[0055]
On the other hand, the arithmetic unit 15, sound line 5a~5c judged by the comparing unit 13 calculates the approximate ground fault current I _g3 seeking vector sum base based on the zero-phase current I _02, I ₀₃ of 6a~6c . This vector sum is obtained by adding instantaneous values.
[0056]
Further, the calculation of the vector sum may be performed on the zero-phase currents I ₀₂ and I ₀₃ of the sound lines 5a to 5c and 6a to 6c after detecting the ground fault, and after the transient state has elapsed. healthy line bodies 5a to 5c, may be performed on the zero-phase current I _02, I ₀₃ of 6 a to 6 c.
[0057]
In addition, when calculating the vector sum for the zero-phase current of the sound line after passing this transient state, a timer function is provided in the ground fault detection device 10 and after the ground fault is detected. It can be implemented for a sum of zero-phase currents of a healthy line after a predetermined time, for example, about 100 ms has elapsed.
[0058]
Also, the zero-phase current of the sound line detected in the transient state after detecting a ground fault has an irregular waveform and high frequency component, but is detected after the transient state has elapsed. Since the zero-phase current of the sound line is a stable waveform and does not have a high-frequency component as high as in the transient state, the signal processing becomes easy. Therefore, for example, after the ground fault is detected by masking the transient period by performing the calculation of the vector sum with respect to the zero-phase current of the healthy line after the transient state as described above. Although some time of about 100 ms is wasted time, since the signal processing means for the zero-phase current of the healthy line can be configured simply, the cost of the ground fault suppression system can be reduced.
[0059]
The approximate ground fault current I _g3 calculated in this way is output to the antiphase waveform generator 20 via the output unit 16, while the input command signal It is opened and closed for system entry via the output unit 16. Is output to the device 41.
[0060]
In the antiphase waveform generator 20, the approximate ground fault current I _g3 is input to the input unit 21. The waveform generator 22 generates the same current waveform as the input approximate ground fault current signal as needed. The waveform reversing unit 23 performs reversal processing on the current waveform generated by the waveform generating unit 22 so as to be in reverse phase with respect to the ground fault current. The antiphase current I _v generated in this way is output from the output unit 24 to the injection transformer 40.
[0061]
Then, the antiphase current I _v output to the injection transformer 40 passes through the bus 3c as indicated by the solid line arrow, flows into the ground fault phase 4c of the ground fault lines 4a to 4c, flows into the ground fault point G, and is connected to the ground fault. The current _Ig is suppressed.
[0062]
In the ground fault suppression system of FIG. 1 described above, a malfunction protection resistor circuit 42 having a resistance of several Ω is provided in parallel with the injection transformer 40. In the system of FIG. 1, even if the injection transformer 40 is connected to a healthy phase due to a misidentification of the ground fault phase, the resistance of the resistance circuit 42 is equal to the transformation ratio of the injection transformer 40 on the distribution system side. By acting in proportion to the square, the short-circuit current due to the out-of-phase ground short circuit can be reduced.
[0063]
(Ground fault current suppression principle)
Next, the principle of ground fault current suppression will be specifically described based on FIG. 4 and FIG.
[0064]
Figure 4 shows a suppressing equivalent circuit ground fault current I _g. Here, in order to explain in comparison with the equivalent circuit of FIG. 6 described above, the same symbols are used for the same parts.
[0065]
Suppressing operation of the ground fault current I _g is as follows.
[0066]
(1) Primary grounding of the zero-phase transformer composed of the sum of the zero-phase currents I ₀₂ and I ₀₃ flowing through the sound lines 102 and 103 of the ground fault current I _g and a grounded instrument transformer (GVT) Residual (= I _g2 + I _v = I ₀₂ + I ₀₃ + I _RN + I _RN ) between the combined current I _g2 (= I ₀₂ + I ₀₃ + I _RN ) with the resistance current I _RN flowing from the neutral line 104 and the antiphase current I _{v v} ) is not monitored, and only the sum I _g3 (= I ₀₂ + I ₀₃ ) of the zero-phase current of each sound line is monitored.
[0067]
(2) A negative phase current I _v is generated according to the sum I _g3 (= I ₀₂ + I ₀₃ ) of the zero phase current of each healthy line and injected into the distribution system.
[0068]
(3) Of the ground fault current I _g (= I ₀₁ + I ₀₂ + I ₀₃ + I _RN ), the ground fault is suppressed by suppressing the sum of the zero phase currents I _g3 (= I ₀₂ + I ₀₃ ) of each sound line. The current _Ig is suppressed.
[0069]
(4) Since the zero-phase current of each healthy line continues to flow unless the cause of the ground fault is removed, even if the residual between the ground fault current I _g and the negative phase current I _v becomes small, the negative phase current I _v The generation / injection amount of is not reduced, and the ground fault current is stably suppressed.
[0070]
Figure 5 is a vector diagram showing the principle of suppressing the ground fault current I _g according to the invention, FIG. 5 (a) regular ground fault condition in the case of not applying the anti-phase waveform generator, and FIG. 5 (b) These show the state at the time of applying an antiphase waveform generator in the state of Fig.5 (a). The zero-phase currents I ₀₂ and I _{03 of} each healthy line shown in FIG. 5A are respectively detected by the zero-phase current transformers 108 and 109 of the equivalent circuit of FIG. 4, and the sum I _g3 (= I ₀₂ + I _03). ) Is always monitored. According to this I _{g3, the} antiphase current I _V (= −I _g3 ) is generated and injected as shown in FIG. 5B, so that the portion of the ground fault current I _g is suppressed by I _g3 , ground fault current I _g is also suppressed.
[0071]
Incidentally, as it follows idea to arrange again the relationship between the resistance component current flowing in the primary side ground neutral line of the ground fault current I _g and the zero-phase current and zero-phase voltage unit for each line.
[0072]
[Equation 5]

Where I _g1 = I ₀₁
I _g2 = I _g3 + I _RN
I _g3 = I ₀₂ + I ₀₃
I ₀₁ : Zero-phase current that flows in the ground fault line 101 itself, and cannot be detected by the zero-phase current transformer.
[0073]
I ₀₂ : Zero-phase current flowing through the healthy line 102.
[0074]
I ₀₃ : Zero-phase current flowing through the healthy line 103.
[0075]
I _RN : In the ground fault suppression system and the ground fault suppression method according to the present invention as described above, the ground fault flowing in the ground fault line as in the prior art is equal to or more than the resistance current flowing in the primary-side ground neutral line 104 of the zero-phase transformer. Of the current I _g , the combined current I _g2 (= I ₀₂ + I ₀₃ + I _RN ) of the zero-phase current flowing in each healthy line and the resistance- _divided current I _RN flowing from the primary-side ground neutral line of the zero-phase transformer Instead of monitoring the residual with the reverse phase current I _V (= I _g2 + I _V = I ₀₂ + I ₀₃ + I _RN + I _V ), the sum of the zero-phase currents I _g3 (= I ₀₂ + I ₀₃ ) of each sound line because you have to monitor only, it is possible to stably suppressed without returning the ground fault current I _g.
[0076]
In the configuration example of FIG. 1, as described above, the switch 41 is provided between the power distribution line and the injection transformer 40, and the switch 41 based on the switch input signal It from the ground fault detection device 10. However, the configuration of the ground fault suppression system according to the present invention is not limited to the above, and it is injected into any phase of the power distribution line. It is good also as a structure which connects the transformer 40 for an operation. With such a configuration, it is possible to omit the step for selecting a phase for interconnecting the injecting transformer 40, so that the configuration of the ground fault detection device 10 can be simplified.
[0077]
【The invention's effect】
As described above, according to the present invention, the approximate ground fault current is calculated based on the vector sum of the zero phase current of the healthy line, and the reverse phase current having the opposite phase to the calculated approximate ground fault current is calculated. Since the power supply is supplied to the distribution line, it is possible to always stably suppress the ground fault current without returning the ground fault, and to provide a ground fault suppression system and a ground fault suppression method in which the ground fault arc is easily extinguished. it can.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a ground fault suppression system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a circuit configuration of the ground fault detection device.
FIG. 3 is a block diagram showing a circuit configuration of an antiphase waveform generator.
FIG. 4 is a circuit diagram illustrating a ground fault current suppression principle according to the present invention.
5A and 5B are vector diagrams showing a ground fault current suppression principle according to the present invention, in which FIG. 5A is a normal ground fault state when an antiphase waveform generator is not applied, and FIG. 5B is a diagram of FIG. The state at the time of applying an antiphase waveform generator in a state is shown.
FIG. 6 is a circuit diagram illustrating a conventional ground fault current suppression principle.
7A and 7B are vector diagrams showing a conventional ground fault current suppression principle, where FIG. 7A is a normal ground fault state when an antiphase waveform generator is not applied, and FIG. 7B is a state shown in FIG. FIG. 7C shows a state at a certain time when the antiphase waveform generator is applied, and FIG. 7C shows a state at a time different from FIG. 7B when the antiphase waveform generator is applied in the state of FIG. Indicates the state.
[Explanation of symbols]
1 Distribution substation 2 Power supply (Power transformer)
3a-3c Busbar 4a-4c Distribution line (Accident distribution line)
5a-5c Distribution line (sound distribution line)
6a-6c Distribution line (sound distribution line)
7a to 7c Zero-phase current transformer 8 Zero-phase transformer 8a Primary-phase grounded neutral wire 9a to 9c Zero-phase transformer Instrument transformer 10 Ground fault detection device 20 Reverse phase waveform generator 30 to 32 Distribution line load 40 Transformer for injection 41 Switch for parallel insertion 42 Resistor circuit for protection against malfunction I _g Ground fault current I _V Reverse phase current V ₀ Zero phase voltage I _g2 , I ₀₂ , I ₀₃ Distribution lines 4a to 4c, 5a to Current detected by each zero-phase current transformer 5c, 6a-6c

Claims (4)

Suppressing a ground fault current in a power distribution line including a plurality of distribution lines connected to a common bus,
Comprising zero phase voltage detecting means for detecting the zero phase voltage of the power distribution line and zero phase current detection means for detecting each zero phase current of the distribution line;
A ground fault detection means for detecting a ground fault based on the zero phase voltage and the current detected by the zero phase current detection means;
Healthy line discrimination means for discriminating a healthy line based on the current detected by the zero-phase current detection means;
An approximate ground fault current calculating means for calculating an approximate ground fault current based on a vector sum of zero phase currents of the determined healthy line;
An antiphase current creating means for creating an antiphase current having an antiphase with the calculated approximate ground fault current;
A ground fault suppression system comprising: a reverse phase current supply unit configured to supply the generated reverse phase current to the power distribution line, and suppressing the ground fault current by the supplied reverse phase current. 2. The ground fault according to claim 1, wherein the calculation of the vector sum of the zero phase current of the healthy line is performed for the zero phase current of the healthy line after a transient state immediately after the occurrence of the ground fault. Suppression system. Suppressing a ground fault current in a power distribution line including a plurality of distribution lines connected to a common bus,
Comprising a zero phase voltage detection step for detecting a zero phase voltage of the power distribution line and a zero phase current detection step for detecting each zero phase current of the distribution line;
A ground fault detection step for detecting a ground fault based on the zero phase voltage and the current detected by the zero phase current detection step;
A sound line determination step of determining a sound line based on the current detected by the zero-phase current detection step;
An approximate ground fault current calculating step for calculating an approximate ground fault current based on the vector sum of the zero phase current of the determined healthy line;
An antiphase current creating step for creating an antiphase current having an antiphase with the calculated approximate ground fault current;
A ground fault suppression method comprising: a reverse phase current supply step of supplying the created reverse phase current to the power distribution line, and suppressing the ground fault current by the supplied reverse phase current. 4. The ground fault according to claim 3, wherein the calculation of the vector sum of the zero phase current of the healthy line is performed on the zero phase current of the healthy line after a transient state immediately after the occurrence of the ground fault. Suppression method.

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