JP3988932B2

JP3988932B2 - Earth leakage detector

Info

Publication number: JP3988932B2
Application number: JP2003027505A
Authority: JP
Inventors: 学堤
Original assignee: Kawamura Electric Inc
Current assignee: Kawamura Electric Inc
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2007-10-10
Anticipated expiration: 2023-02-04
Also published as: JP2004242404A

Description

【０００１】
【発明の属する技術分野】
本発明は、電路の漏電を検出する漏電検出装置に関し、特に三相３線式電路及び単相３線式電路の漏電を検出する漏電検出装置に関する。
【０００２】
【従来の技術】
例えば三相３線式電路の従来の漏電検出装置としては特許文献１に示す構成のもの、また単相電路の従来の漏電検出装置としては特許文献２に示す構成のものがある。双方とも本発明者等が提案した技術で、それまでの漏電検出装置が有していた対地静電容量による常時漏洩電流が大きくなると感度が劣化する問題を解決する為に本発明者等が提案したもので、特許文献１では、非接地線間電圧位相の０°又は１８０°の固定タイミングで零相電流Ｉｏ波形をサンプリングして、地絡電流Ｉgrを検出していた。また、特許文献２では、電源電圧位相の９０°又は２７０°の固定タイミングで零相電流Ｉｏ波形をサンプリングして、地絡電流Ｉgrを検出していた。
【０００３】
【特許文献１】
実開平６−５７０３７号公報
【特許文献２】
実開平６−５７０３６号公報
【０００４】
【発明が解決しようとする課題】
しかし、上記特許文献１，２の技術は、三相３線式電路或いは単相３線式電路において、接地抵抗が小さい場合には良好に地絡電流Ｉgrを検出できたが、接地抵抗は１００Ω以上という大きい値の場合もあり、このような場合に各相の対地静電容量のバランスが崩れたり、全体の対地静電容量が大きくなったりして電路全体の漏洩電流（常時漏洩電流Ｉgc）が大きくなった場合は、漏洩電流の遅れ位相が大きくなるため、上記タイミングでサンプリングした零相電流値と実際の地絡電流値との差が大きくなってしまい誤動作する問題があった。
【０００５】
図９の波形図を基に具体的に説明すると、図９は三相３線式電路の零相電流Ｉｏ、常時漏洩電流Ｉgc、地絡電流Ｉgrの各位相を説明する為の波形図であり、（ａ）は接地抵抗値が例えば１０Ωと小さい場合、（ｂ）は接地抵抗値が例えば１００Ωと大きい場合を示し、電源電圧と同相の常時漏洩電流Ｉgcの位相１８０°での零相電流Ｉｏの値が図９（ａ）では地絡電流Ｉgrと重なるが、図（ｂ）では交差点が大きくずれて重ならない。そのため、大きな誤差が生ずることになる。そして、この特徴は単相３線式電路でも同様であった。
【０００６】
そこで、本発明は上記問題点に鑑み、接地抵抗が大きく更に対地静電容量が大きい電路においても良好に漏電を検出できる漏電検出装置を提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記課題を解決するため、請求項１の発明は、零相電流検出手段と、零相電流波形のゼロクロス点を検出する電流ゼロクロス点検出手段と、電源電圧波形のゼロクロス点を検出する電圧ゼロクロス点検出手段と、接地抵抗値入力手段と、前記各手段の出力を基に漏電を判断する漏電演算手段とを有し、前記漏電演算手段は、予め入力設定された接地抵抗情報と検出した零相電流情報と前記電流ゼロクロス点情報及び電圧ゼロクロス点情報とから、予め設定した電源電圧の位相角における零相電流瞬時値を地絡電流相当値として演算し、該地絡電流相当値を、少なくとも零相電流と接地抵抗値を基に算出した感度基準値と比較して漏電発生を判断し、前記感度基準値を、現在と同一の零相電流と接地抵抗の条件下で、漏電検出装置の定格感度電流に等しい漏電が発生している時の予め設定した電源電圧の位相角における零相電流瞬時値としたことを特徴とする。
この構成により、対地静電容量による常時漏洩電流が大きくなっても、また接地抵抗値が大きくなっても感度基準値がそれに伴い変更され、常に精度良く地絡電流相当値を比較判断でき、精度良く漏電を判定できる。
【０００８】
請求項２の発明は、請求項１の発明において、漏電演算手段は、零相電流情報から零相電流実効値を演算し、電流ゼロクロス点情報と電圧ゼロクロス点情報とを基に、予め設定した電源電圧の位相角での零相電流位相を演算し、求めた前記零相電流位相と前記零相電流実効値とから零相電流の瞬時値を演算し、求めた零相電流の瞬時値を地絡電流相当値として感度基準値と比較することを特徴とする。
この構成により地絡電流相当値を精度良く演算できる。
【０００９】
請求項３の発明は、請求項２の発明において、Δ結線された三相３線式電路にあっては、予め設定した電源電圧の位相角が、電源電圧波形の位相０°或いは１８０°であることを特徴とする。
このように地絡電流を演算するための電源電圧位相角を１８０°とすることで、三相３線式電路の地絡電流値を容易に求める事ができる。
【００１２】
【発明の実施の形態】
以下、本発明を具体化した実施の形態を、図面に基づいて詳細に説明する。
図１は本発明に係る漏電検出装置の第１実施形態を示す回路ブロック図であり、Δ結線された三相３線式電路において漏電を検出する構成を示している。図において、１は接地線１０の零相電流を検出する零相電流検出手段としての零相変流器（ＺＣＴ）、２は接地抵抗Ｒｅ値等を入力する入力手段としての入力装置、３は漏電発生を報知する警報装置、４は地絡電流値を表示する表示装置であり、５は漏電演算手段としてのマイクロコンピュータ（以下、単にマイコンとする）を示している。また、６は検出した零相電流を増幅する増幅回路、７はＡ／Ｄコンバータ、８は零相電流波形のゼロクロス点を検出する電流ゼロクロス点検出手段としての電流ゼロクロス点検出回路、９は電源電圧波形のゼロクロス点を検出する電圧ゼロクロス点検出手段としての電圧ゼロクロス点検出回路を示している。
【００１３】
尚、接地線１０は、Ｒ，Ｓ，Ｔ相のうちＳ相に設けられ、Ｂ種接地されている。また、電圧ゼロクロス点検出回路９は図示しない電圧検出手段により接地されていないＴ相−Ｒ相間の電圧Ｖtrを電源電圧として検出し、その電源電圧Ｖtrの波形からゼロクロス点を検出している。
【００１４】
マイコン５は、説明のために演算データ（演算情報）及び各演算部をブロックで示し、データの流れを矢印で示している。図において、１１は接地抵抗値データ、１２は零相電流ゼロクロス点検出情報、１３は電源電圧ゼロクロス点検出情報を示し、１４は零相電流実効値演算部、１５は零相電流の位相演算部、１６は感度基準値演算部、１７は零相電流の瞬時値演算部、１８は地絡電流演算部、１９は比較部を示している。
そして、Ａ／Ｄコンバータ７を介して零相電流Ｉｏ検出データがマイコン５に入力されると共に、検出された零相電流Ｉｏは電流ゼロクロス点検出回路８により、ゼロクロス点情報が検出した零相電流Ｉｏと同位相の方形波信号Ｐｉ（以下、零相電流ゼロクロス点情報をＰｉ情報とする。）としてマイコン５に入力される。また検出された電源電圧Ｖtrのゼロクロス点情報が検出電圧と同位相の方形波信号Ｐｖ（以下、電源電圧ゼロクロス点情報をＰｖ情報とする。）としてマイコン５に入力される。
【００１５】
こうして入力された接地抵抗Ｒｅ、零相電流Ｉｏ、Ｐｉ情報、Ｐｖ情報を基に、Δ結線された三相３線電路の場合、マイコン５は、予め入力された接地抵抗値Ｒｅと現在の零相電流Ｉｏの実効値Ｉｏｒｍｓとから感度基準値Ｉｓを設定すると共に、電源電圧Ｖｔｒの位相０°又は１８０°（以下、位相Φｖｏとする）で零相電流Ｉｏ波形をサンプリングする演算をして、
Ｉｏサンプリング値≧Ｉｓ
の場合漏電発生と判断する。
【００１６】
マイコン５の動作を具体的に説明すると、まず、デジタルデータに変換された零相電流Ｉｏ値から実効値演算プログラムにより零相電流実効値Ｉormsを求める。求めた零相電流実効値Ｉormsと予め測定して入力設定された接地抵抗Ｒｅのデータとを基に数１に示す演算式から成る感度基準値演算プログラムにより現在の感度基準値Ｉｓを求める。
【００１７】
【数１】

【００１８】
尚、ここでは漏電検出装置の定格感度電流を５０ｍＡとしている。
また、Ｐｉ情報と、Ｐｖ情報とを基に、数２に示す演算式からなる位相演算プログラムにより電源電圧Ｖtrが位相Φvoの時の零相電流Ｉｏの位相Φを求める。
【００１９】
【数２】

【００２０】
尚、ここでは位相Φvoを便宜上１８０°としている。
次に、求めた上記位相Φを基に、電源電圧Ｖtrの位相１８０°での零相電流Ｉｏの瞬時値Ｉｏ（Φ）を数３に示す演算式からなるプログラムにより求める。
【００２１】
【数３】

【００２２】
この処理により、電源電圧Ｖtrの位相１８０°における零相電流Ｉｏの瞬時値Ｉｏ（Φ）がサンプリングされる。そして、この零相電流瞬時値Ｉｏ（Φ）と求めた現在の感度基準値Ｉｓを基に、数４に示す地絡電流Ｉgr演算式からなるプログラムにより地絡電流Ｉgrを求める。更に、求めた地絡電流Ｉgrを、表示プログラムにより表示装置４にて表示する。
【００２３】
【数４】

【００２４】
そして、求めた零相電流瞬時値Ｉｏ（Φ）を現在の感度基準値Ｉｓと比較して、零相電流瞬時値Ｉｏ（Φ）が感度基準値Ｉｓに達したら漏電発生と判断して警報信号を出力し、継電器等の警報装置３を動作させる。
【００２５】
ここで、上記演算式の根拠を図４のシミュレーション図を基に説明する。図４は、周波数５０ＨｚのΔ結線した三相３線式電路において、位相Φｖｏにおける零相電流Ｉｏの瞬時値Ｉｏ（Φ）をシミュレーションして作成したグラフであり、地絡電流Ｉｇｒ＝５０ｍＡの漏電を発生させた状態で、接地抵抗値Ｒｅ及び零相電流実効値Ｉｏｒｍｓを変化させている。
このシミュレーション図から、接地抵抗Ｒｅと零相電流Ｉｏが求まれば、５０ｍＡの漏電が発生している時の位相Φｖｏにおける零相電流瞬時値Ｉｏ（Φ）を特定できることが解る。
【００２６】
このことから、図４から求まる位相Φｖｏにおける零相電流瞬時値Ｉｏ（Φ）を、定格感度電流を５０ｍＡとした場合の漏電検出装置の感度基準値Ｉｓに設定できることが解る。そして、上記実施形態では、図４の特性を補間法等により近似式数１に変換して、マイコン５の演算により感度基準値Ｉｓを求めたものである。
ここで、感度基準値について説明する。感度電流が５０ｍＡの場合の感度基準値は、５０ｍＡの漏電が発生しているときの位相Φｖｏにおける零相電流Ｉｏの瞬時値Ｉｏ（Φ）（の絶対値）をいう。図４に示すように、位相Φｖｏでの零相電流Ｉｏ瞬時値＝感度基準値は、Ｂ種接地抵抗値ＲＥ、零相電流値Ｉｏｒｍｓに応じて変化する。逆に、数１に基づく演算等の手段を用いて、Ｂ種接地抵抗ＲＥ及び現在の零相電流値Ｉｏｒｍｓから、現在の感度基準値Ｉｓを求めることができる。そして、別途位相Φｖｏにおける現在の零相電流瞬時値Ｉｏ（Φ）を測定し、この値と現在の感度基準値Ｉｓを比較すれば、５０ｍＡ以上の漏電の発生を検知できる。即ち、零相電流瞬時値Ｉｏ（Φ）が感度基準値Ｉｓより小さいときは、漏電電流は５０ｍＡ以下と判断できるし、零相電流瞬時値Ｉｏ（Φ）が感度基準値Ｉｓより大きいときは、５０ｍＡ以上の漏電が発生していると判断できる。
【００２７】
具体的に波形図により説明すると、図２はＴ相にて漏電が発生した場合の各波形を示し、図３はＲ相にて漏電が発生した場合の各波形を示している。縦軸は電流値で単位はアンペア、横軸は基準電圧である非接地線間電圧Ｖｔｒの位相角で単位は度である。何れも、接地抵抗Ｒｅ＝１００Ω、Ｒ相、Ｔ相の対地静電容量ＣＲ＝ＣＴ＝０．９５６μＦ、地絡抵抗Ｒｇ＝３９００Ω、とした場合のシミュレーション結果である。尚、後述する表１のシミュレーション結果の欄に、図１及び図２の各波形の実効値、電源電圧Ｖｔｒと零相電流Ｉｏの位相差、及び位相Φｖｏにおける零相電流瞬時値Ｉｏ（Φ）を示している。
【００２８】
次に、接地抵抗Ｒｅと零相電流Ｉｏの実効値及び位相情報のみから、地絡電流Ｉｇｒを演算により求めてみる。Ｔ相漏電の場合、零相電流実効値Ｉｏｒｍｓ＝１３３．４ｍＡ、接地抵抗Ｒｅ＝１００Ωを数１に代入して感度基準値Ｉｓ＝７３．６ｍＡを得る。また、電源電圧Ｖｔｒと零相電流Ｉｏの位相差２２．３°を数２に代入して、電源電圧位相１８０°のときの零相電流Ｉｏの位相Φ＝１５７．７°を得る。これを数３に代入して電源電圧位相１８０°のときの零相電流瞬時値Ｉｏ（Φ）＝７１．５ｍＡを得る。最後に、求めた感度基準値Ｉｓと零相電流瞬時値Ｉｏ（Φ）を数４に代入して、地絡電流Ｉｇｒ＝４８．６ｍＡ（真値も４８．６ｍＡ）を得る。
また、Ｒ相漏電の場合、零相電流Ｉｏ＝８７．７ｍＡ、接地抵抗Ｒｅ＝１００Ωを数１に代入して、感度基準値Ｉｓ＝６５．５ｍＡを得る。また、電源電圧Ｖｔｒと零相電流Ｉｏの位相差が３２．９°を数２に代入して、電源電圧位相１８０°のときの零相電流Ｉｏの位相Φ＝１４７．１°を得る。これを数３に代入して、電源電圧１８０°の時の零相電流瞬時値Ｉｏ（Φ）＝６７．３ｍＡを得る。最後に、求めた感度基準値Ｉｓと零相電流瞬時値Ｉｏ（Φ）を数４に代入して、地絡電流Ｉｇｒ＝５１．４ｍＡ（真値は５１．２ｍＡ）を得る。
尚、特許文献１に示す従来の技術では、Ｔ相漏電の場合、地絡電流Ｉｇｒ＝Ｉｏ（Φ）／（√２ｓｉｎ１２０°）からＩｇｒ＝５８．４ｍＡであるし、Ｒ相漏電の場合は、同様に地絡電流Ｉｇｒ＝５４．９ｍＡである。
【００２９】
この結果をまとめると表１のようになる。この比較結果から、上記実施の形態による演算から求められた地絡電流Ｉgrは、Ｔ相漏電の場合、Ｉgr＝４８．６ｍＡ、Ｒ相漏電の場合、Ｉgr＝５１．４ｍＡと、実際の地絡電流値４８．６ｍＡ、５１．２ｍＡに近い値で漏電を検出するのに対して、従来の技術ではＩgr＝５８．４ｍＡ、或いはＩgr＝５４．９ｍＡと実際の地絡電流値から大きく外れた値を示していることがわかる。
【００３０】
【表１】

【００３１】
このように、予め設定した電源電圧の位相角における零相電流瞬時値を地絡電流相当値として求め、零相電流と接地抵抗値を基に算出した感度基準値と比較して漏電発生を判断するので、対地静電容量による常時漏洩電流が大きくなっても、また接地抵抗値が大きくなっても感度基準値がそれに伴い変更されるので、常に精度良く地絡電流相当値を比較判断でき、精度良く漏電を判定できる。
また、地絡電流相当値を演算するための電源電圧位相角を１８０°とすることで三相３線式電路の地絡電流相当値を容易に求める事ができるし、地絡電流相当値を予め設定した電源電圧の位相角での零相電流位相と零相電流実効値とから求めるので精度よく求めることができる。
更に、表示装置が演算した地絡電流値を表示するので、漏電発生時の漏電状態を把握でき、復旧等に有効に活用できる。
【００３２】
尚、上記実施形態では、零相電流の瞬時値Ｉｏ（Φ）を求める電源電圧位相Φvoを１８０°として演算しているが０°としても良い。また、漏電検出装置の定格感度電流を５０ｍＡとして説明したが、他の定格感度電流に対しても感度基準値Ｉｓの演算式等をそれに合わせて変更することで適用できる。
【００３３】
図５は漏電検出装置の第２実施形態を示す図であり、単相３線式電路に適用した漏電検出装置の回路ブロック図を示している。図において、２１は中性線Ｎ相に設けた接地線３０の零相電流を検出する零相変流器（ＺＣＴ）、２２は接地抵抗値等を入力する入力装置、２３は漏電発生を報知する警報装置、２４は地絡電流値を表示する表示装置であり、２５はマイクロコンピュータ（以下、単にマイコンとする。）を示している。また、２６は検出した零相電流を増幅する増幅回路、２７はＡ／Ｄコンバータ、２８は零相電流波形のゼロクロス点を検出する電流ゼロクロス点検出回路、２９は電源電圧波形のゼロクロス点を検出ずる電圧ゼロクロス点検出回路を示している。
【００３４】
尚、電源電圧波形のゼロクロス点検出回路２９は、図示しない電圧検出手段により電圧線Ｘ，Ｙ間の電圧を検出し、その電源電圧Ｖの波形からゼロクロス点を検出している。
【００３５】
マイコン２５は、説明のために演算データ（演算情報）及び演算部をブロックで示し、データの流れを矢印で示している。図において、３１は接地抵抗値データ、３２は零相電流ゼロクロス点検出情報、３３は電源電圧ゼロクロス点検出情報を示し、３４は零相電流実効値演算部、３５は対地静電容量による漏洩電流である常時漏洩電流Ｉgc波形がゼロクロスするときの電源電圧位相Φcoを求める電圧位相演算部、３６は零相電流の位相演算部、３７は感度基準値演算部、３８は零相電流の瞬時値演算部、３９は地絡電流演算部、４０は比較部を示している。
【００３６】
そして、Ａ／Ｄコンバータ２７を介して零相電流検出データがマイコン２５に入力されると共に、検出された零相電流Ｉｏは電流ゼロクロス点検出回路２８により、ゼロクロス点情報が検出した零相電流と同位相の方形波信号Ｐｉ（以下、零相電流ゼロクロス点情報をＰｉ情報とする。）としてマイコン２５に入力される。また、検出された電源電圧Ｖのゼロクロス点情報は検出電圧と同位相の方形波信号Ｐｖ（以下、電源電圧ゼロクロス点情報をＰｖ情報とする。）としてマイコン２５に入力される。
【００３７】
このように、入力された接地抵抗値Ｒｅ、零相電流Ｉｏ、Ｐｉ情報、Ｐｖ情報を基に、単相３線式電路の場合、マイコン２５が、予め入力された接地抵抗値Ｒｅと現在の零相電流Ｉｏの実効値Ｉormsとから電路の対地静電容量を介して流れる常時漏洩電流Ｉgc波形のゼロクロスタイミングを特定して、特定したゼロクロスタイミングから感度基準値Ｉｓを設定すると共に、そのゼロクロスタイミングでＩｏ波形をサンプリングして、求めた感度基準値Ｉｓと比較して、
Ｉｏサンプリング値≧Ｉｓ
の場合漏電発生と判断する。
【００３８】
マイコン２５の動作を具体的に説明すると、まずデジタルデータに変換された零相電流Ｉｏ値から実効値演算プログラムにより零相電流実効値Ｉormsを求める。求めた零相電流実効値Ｉormsと入力設定された接地抵抗Ｒｅのデータとを基に、数５に示す演算式からなる演算プログラムにより常時漏洩電流Ｉgcがゼロクロスするときの電源電圧位相（以下、ゼロクロス電圧位相とする。）Φcoを求める。
【００３９】
【数５】

【００４０】
そして、このゼロクロス電圧位相Φｃｏを基に数６に示す演算式からなる感度基準値演算プログラムにより現在の感度基準値Ｉｓを求める。
【００４１】
【数６】

【００４２】
尚、漏電検出装置の定格感度電流を５０ｍＡとしてプログラムしてある。
また、ゼロクロス電圧位相Φcoと、Ｐｉ情報と、Ｐｖ情報を基に、数７に示す演算式からなる位相演算プログラムから電源電圧Ｖの位相がゼロクロス電圧位相Φcoの時の零相電流Ｉｏの位相Φを求める。
【００４３】
【数７】

【００４４】
次に、求めた上記位相Φでの零相電流Ｉｏの瞬時値Ｉｏ（Φ）を数８に示す演算式からなるプログラムから求める。尚、この瞬時値Ｉｏ（Φ）は常時漏洩電流Ｉｇｃがゼロクロスする瞬間の零相電流Ｉｏの値であるから、地絡電流Ｉｇｒの位相を電源電圧位相と同相とすれば、地絡電流Ｉｇｒの位相Φｃｏにおける瞬時値と見なせる。
【００４５】
【数８】

【００４６】
この処理により、電源電圧Ｖのゼロクロス電圧位相Φcoにおける零相電流Ｉｏの瞬時値がサンプリングされ、この零相電流瞬時値Ｉｏ（Φ）と現在の感度基準値Ｉｓを基に、数９に示す地絡電流Ｉgr演算式からなるプログラムにより地絡電流Ｉgrを求め、求めた地絡電流Ｉgrを表示プログラムにより表示装置２４にて表示する。
【００４７】
【数９】

【００４８】
そして、求めた零相電流瞬時値Ｉｏ（Φ）を、求めた現在の感度基準値Ｉｓと比較して、零相電流瞬時値Ｉｏ（Φ）が感度基準値Ｉｓに達していたら漏電発生と判断して警報信号を出力し、継電器等の警報装置２３を動作させる。
【００４９】
ここで上記演算式の根拠を図８のシミュレーション図を基に説明する。図８は周波数５０Ｈｚの単相３線式電路で地絡電流Ｉｇｒ＝５０ｍＡの漏電を発生させた状態で、接地抵抗Ｒｅ及び零相電流Ｉｏの実効値を変化させてゼロクロス電圧位相Φｃｏ、即ち常時漏洩電流Ｉｇｃがゼロクロスするときの電源電圧位相をシミュレーションして作成した図である。尚、零相電流Ｉｏの変化は、Ｙ相側の対地対地静電容量を一定とし、Ｘ相側の対地静電容量を変化することによる。
この図から、接地抵抗Ｒｅと零相電流Ｉｏとからゼロクロス電圧位相Φｃｏを特定できることが解る。
【００５０】
この図８から、地絡電流Ｉｇｒは電源電圧位相と同相と仮定することで、Ｉｇｒ＝５０ｍＡの時のゼロクロス電圧位相Φｃｏにおける地絡電流Ｉｇｒの瞬時値は、√２×５０×ｓｉｎ（Φｃｏ）で求まり、これが感度基準値Ｉｓとなる（数６）。正確には、定格感度電流５０ｍＡの漏電検出装置のゼロクロス電圧位相Φｃｏにおける感度基準値Ｉｓとなる。例えば、定格感度電流５０ｍＡの漏電検出装置において、ゼロクロス電圧位相Φｃｏ＝９５°の時の感度基準値Ｉｓは７０．４ｍＡとなる。
そして、上記第２実施形態では、図８の特性を補間法等により近似式に変換して、マイコンの演算により感度基準値Ｉｓを求めた。
感度電流が５０ｍＡの場合の感度基準値とは、ある接地抵抗と零相電流において５０ｍＡの漏電が発生しているときの位相Φｃｏにおける地絡電流Ｉｇｒの瞬時値をいう。そして、別途位相Φｃｏにおける零相電流Ｉｏの現在の瞬時値Ｉｏ（Φ）を測定し、この値と現在の感度基準値Ｉｓとを比較すれば、５０ｍＡ以上の漏電の発生を検知できる。即ち、零相電流瞬時値Ｉｏ（Φ）が感度基準値Ｉｓより小さい時は、漏電電流は５０ｍＡ以下と判断できるし、感度基準値Ｉｓより大きい時は、５０ｍＡ以上の漏電が発生していると判断できる。
【００５１】
尚、図８の零相電流Ｉｏの変化はＹ相の対地静電容量を固定とし、Ｘ相の対地静電容量を変化させて求めている。また、図８では９０°付近のゼロクロス電圧位相Φcoを示しているが、当然ゼロクロス電圧位相Φcoに１８０°を加えた位相にも常時漏洩電流Ｉgc波形のゼロクロスタイミングが存在する。
【００５２】
具体的に波形図により説明すると、図６はＸ相で漏電が発生した場合の各波形を示し、図７はＹ相にて漏電が発生した場合の各波形を示している。双方とも、縦軸は電流値で単位はアンペア、横軸は電源電圧の位相角で単位は度である。また、接地抵抗Ｒｅ＝１００Ω、地絡抵抗Ｒｇ＝１９００Ωで、Ｘ相の対地静電容量Ｃｘ＝３．５μＦ、Ｙ相の対地静電容量Ｃｙ＝０．５μＦとした場合のシミュレーション結果である。尚、後述する表２のシミュレーション結果の欄に、図６及び図７の各波形の実効値と、零相電流瞬時値Ｉｏの位相を示している。
【００５３】
次に、接地抵抗Ｒｅと零相電流Ｉｏの実効値及び位相情報のみから、地絡電流Ｉｇｒを演算により求めてみる。Ｘ相漏電の場合、零相電流Ｉｏ＝１０１．８ｍＡ、接地抵抗Ｒｅ＝１００Ωを数５に代入してゼロクロス電圧位相Φｃｏ＝９６．８°得る。この結果を数６に代入して感度基準値Ｉｓ＝７０．２ｍＡを得る。また、数５で求めたゼロクロス電圧位相Φｃｏと零相電流Ｉｏと電源電圧の位相差５４．０°を数７に代入して、ゼロクロス電圧位相Φｃｏ時の零相電流位相Φ＝１５０．８°を得る。そして、この結果を数８に代入してゼロクロス電圧位相Φｃｏ時の零相電流瞬時値Ｉｏ（Φ）＝７０．２ｍＡを得る。最後に、求めた感度基準値Ｉｓと零相電流瞬時値Ｉｏ（Φ）を数９に代入して、地絡電流Ｉｇｒ＝５０．０ｍＡ（真値は４９．７ｍＡ）を得る。
また、Ｙ相漏電の場合、零相電流Ｉｏ＝１０１．８ｍＡ、接地抵抗Ｒｅ＝１００Ωを数５に代入してゼロクロス電圧位相Φｃｏ＝９６．８°得る。この結果を数６に代入して感度基準値Ｉｓ＝７０．２ｍＡを得る。また、数５で求めたゼロクロス電圧位相Φｃｏと零相電流Ｉｏと電源電圧の位相差１１２．４°を数７に代入して、ゼロクロス電圧位相Φｃｏ時の零相電流位相Φ＝２９．４°を得る。そして、この結果を数８に代入してゼロクロス電圧位相Φｃｏ時の零相電流瞬時値Ｉｏ（Φ）＝７０．７ｍＡを得る。最後に、求めた感度基準値Ｉｓと零相電流瞬時値Ｉｏ（Φ）を数９に代入して、地絡電流Ｉｇｒ＝５０．４ｍＡ（真値は５０．８ｍＡ）を得る。
尚、特許文献２に示す従来の技術では、Ｘ相漏電の場合、地絡電流Ｉｇｒ＝Ｉｏ（Φ）×ｓｉｎ（Ｉｏ位相＋９０°）からＩｇｒ＝５９．８ｍＡであるし、Ｙ相漏電の場合、同様にＩｇｒ＝３８．８ｍＡである。
【００５４】
この結果をまとめると表２のようになる。この比較結果から、上記実施の形態による演算から求められた地絡電流Ｉgrは、Ｘ相漏電の場合、Ｉgr＝５０．０ｍＡ、Ｙ相漏電の場合、Ｉgr＝５０．４ｍＡと、実際の地絡電流値４９．７ｍＡ、５０．８ｍＡに近い値で漏電を検出するのに対して、従来の技術ではＩgr＝５９．８ｍＡ、或いは３８．８ｍＡと、実際の地絡電流値から大きく外れた値を示していることがわかる。
【００５５】
【表２】

【００５６】
このように、常時漏洩電流Ｉgcがゼロクロスするときの位相Φでの零相電流瞬時値を地絡電流相当値として求め、設定した定格感度電流のその位相Φcoでの瞬時値を感度基準値とし、双方を比較して漏電発生を判断するので、対地静電容量による常時漏洩電流が大きくなっても、また接地抵抗値が大きくなっても感度基準値がそれに伴い変更され、常に精度良く地絡電流相当値を比較判断でき、精度良く漏電を判定できる。
また、地絡電流を演算するための電源電圧位相角を常時漏洩電流波形を基準とする電源電圧位相とすることで、単相３線式電路の地絡電流値を容易に求める事ができるし、地絡電流値を出力するので、その表示装置を設ければ漏電発生時の漏電状態を把握でき、復旧等に有効に活用できる。
【００５７】
尚、上記実施形態は、何れも接地線に零相変流器を設けて零相電流を検出しているが、零相電流は電路から直接検出しても良い。
【００５８】
【発明の効果】
以上詳述したように、本発明によれば、予め設定した電源電圧の位相角における零相電流瞬時値を地絡電流相当値として求め、少なくとも零相電流と接地抵抗値を基に算出した感度基準値と比較して漏電発生を判断するので、対地静電容量による常時漏洩電流が大きくなっても、また接地抵抗値が大きくなっても感度基準値がそれに伴い変更されるので、常に精度良く地絡電流相当値を比較判断でき、精度良く漏電を判定できる。
【００５９】
また、地絡電流を演算するための電源電圧位相角を１８０°とすることで、三相３線式電路の地絡電流値を容易に求める事ができるし、地絡電流を演算するための電源電圧位相角を常時漏洩電流波形を基準とする電源電圧位相とすることで、単相３線式電路の地絡電流値を容易に求める事ができる。
さらに、演算した地絡電流値を出力するので、その表示装置を設ければ漏電発生時の漏電状態を把握でき、復旧等に有効に活用できる。
【図面の簡単な説明】
【図１】本発明の第１実施形態を示し、三相３線式電路に設けた漏電検出装置のブロック図である。
【図２】三相３線式電路のＴ相で漏電が発生した場合の各波形を示し、図１の漏電検出装置により漏電を検出する説明図である。
【図３】三相３線式電路のＲ相で漏電が発生した場合の各波形を示し、図１の漏電検出装置により漏電を検出する説明図である。
【図４】三相３線式電路の零相電流瞬時値Ｉｏ（Φ）のシミュレーションデータを示す図である。
【図５】本発明の第２実施形態を示し、単相３線式電路に設けた漏電検出装置のブロック図である。
【図６】単相３線式電路のＸ相で漏電が発生した場合の各波形を示し、図５の漏電検出装置により漏電を検出する説明図である。
【図７】単相３線式電路のＹ相で漏電が発生した場合の各波形を示し、図５の漏電検出装置により漏電を検出する説明図である。
【図８】単相３線式電路において、常時漏洩電流波形がゼロクロスするときの電源電圧位相と接地抵抗の関係をシミュレーションして求めた図である。
【図９】従来の三相３線式電路のＴ相で漏電が発生した状態の波形図であり、（ａ）は接地抵抗が小さい場合、（ｂ）は接地抵抗が大きい場合を示している。
【符号の説明】
１・・零相変流器、２・・入力装置、５・・マイクロコンピュータ（マイコン）、８・・電流ゼロクロス点検出回路、９・・電圧ゼロクロス点検出回路、１０・・接地線、２１・・零相変流器、２２・・入力装置、２５・・マイクロコンピュータ（マイコン）、２８・・電流ゼロクロス点検出検出回路、２９・・電圧ゼロクロス点検出回路、３０・・接地線。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a leakage detection device that detects a leakage in a circuit, and more particularly to a leakage detection device that detects a leakage in a three-phase three-wire circuit and a single-phase three-wire circuit.
[0002]
[Prior art]
For example, a conventional leakage detection device of a three-phase three-wire circuit has a configuration shown in Patent Document 1, and a conventional leakage detection device of a single-phase circuit has a configuration shown in Patent Document 2. Both are technologies proposed by the present inventors, and the present inventors have proposed to solve the problem that the sensitivity deteriorates when the constant leakage current due to the ground capacitance of the current leakage detection device has increased. Therefore, in Patent Document 1, the ground-fault current Igr is detected by sampling the zero-phase current Io waveform at a fixed timing of 0 ° or 180 ° of the non-ground line voltage phase. In Patent Document 2, the ground fault current Igr is detected by sampling the zero-phase current Io waveform at a fixed timing of 90 ° or 270 ° of the power supply voltage phase.
[0003]
[Patent Document 1]
Japanese Utility Model Publication No. 6-57037
[Patent Document 2]
Japanese Utility Model Publication No. 6-57036
[0004]
[Problems to be solved by the invention]
However, in the techniques of

Patent Documents

1 and 2, the ground fault current Igr can be detected well when the ground resistance is small in the three-phase three-wire circuit or the single-phase three-wire circuit, but the ground resistance is 100Ω. There are cases where the value is as large as above. In such a case, the balance of the ground capacitance of each phase is lost, or the overall ground capacitance becomes large, so that the leakage current of the entire circuit (always leakage current Igc) When the current value becomes large, the delay phase of the leakage current becomes large, so that the difference between the zero-phase current value sampled at the above timing and the actual ground fault current value becomes large, resulting in a malfunction.
[0005]
More specifically, FIG. 9 is a waveform diagram for explaining the phases of the zero-phase current Io, the constant leakage current Igc, and the ground fault current Igr of the three-phase three-wire circuit. , (A) shows a case where the ground resistance value is as small as 10Ω, for example, and (b) shows a case where the ground resistance value is as large as 100Ω, for example, and the zero-phase current Io at a phase 180 ° of the constant leakage current Igc in phase with the power supply voltage. 9A overlaps with the ground fault current Igr in FIG. 9A, but the intersection in FIG. As a result, a large error occurs. This feature is the same in the single-phase three-wire circuit.
[0006]
Therefore, in view of the above problems, an object of the present invention is to provide a leakage detecting device that can detect leakage even in an electric circuit having a large ground resistance and a large ground capacitance.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the invention of claim 1 is directed to zero-phase current detection means, current zero-cross point detection means for detecting a zero-cross point of a zero-phase current waveform, and voltage zero-cross inspection for detecting a zero-cross point of a power supply voltage waveform. Output means, ground resistance value input means, and leakage calculation means for determining leakage based on the output of each means, wherein the leakage calculation means is configured to input ground resistance information set in advance and detected zero phase From the current information, the current zero cross point information and the voltage zero cross point information, a zero phase current instantaneous value at a preset phase angle of the power supply voltage is calculated as a ground fault current equivalent value, and the ground fault current equivalent value is at least zero. Compared to the sensitivity reference value calculated based on the phase current and ground resistance value, the occurrence of leakage is judged.Then, the sensitivity reference value is set to zero at a preset phase angle of the power supply voltage when a leakage current equal to the rated sensitivity current of the leakage detection device occurs under the same zero-phase current and grounding resistance conditions as the current one. Phase current instantaneous valueIt is characterized by that.
With this configuration, even if the constant leakage current due to ground capacitance increases or the grounding resistance value increases, the sensitivity reference value is changed accordingly, and the ground fault current equivalent value can always be compared and judged with high accuracy. It is possible to determine the leakage.
[0008]
According to a second aspect of the present invention, in the first aspect of the invention, the leakage calculation means calculates a zero-phase current effective value from the zero-phase current information, and is preset based on the current zero-cross point information and the voltage zero-cross point information. Calculate the zero-phase current phase at the phase angle of the power supply voltage, calculate the instantaneous value of the zero-phase current from the calculated zero-phase current phase and the calculated effective value of the zero-phase current, and calculate the calculated instantaneous value of the zero-phase current. It is characterized by comparing with a sensitivity reference value as a ground fault current equivalent value.
With this configuration, the ground fault current equivalent value can be calculated with high accuracy.
[0009]
According to a third aspect of the present invention, in the second aspect of the invention, in the three-phase three-wire electric circuit that is Δ-connected, the preset phase angle of the power supply voltage is 0 ° or 180 ° of the power supply voltage waveform. It is characterized by being.
Thus, by setting the power supply voltage phase angle for calculating the ground fault current to 180 °, the ground fault current value of the three-phase three-wire circuit can be easily obtained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings.
FIG. 1 is a circuit block diagram showing a first embodiment of a leakage detecting apparatus according to the present invention, and shows a configuration for detecting a leakage in a three-phase three-wire circuit connected in Δ. In the figure, 1 is a zero-phase current transformer (ZCT) as a zero-phase current detecting means for detecting a zero-phase current of the

ground wire

10, 2 is an input device as an input means for inputting a ground resistance Re value, etc. An alarm device for notifying the occurrence of electric leakage, 4 is a display device for displaying a ground fault current value, and 5 is a microcomputer (hereinafter simply referred to as a microcomputer) as an electric leakage calculation means. Reference numeral 6 denotes an amplification circuit for amplifying the detected zero-phase current, 7 denotes an A / D converter, 8 denotes a current zero-cross point detection circuit as current zero-cross point detection means for detecting a zero-cross point of the zero-phase current waveform, and 9 denotes a power source. 1 shows a voltage zero cross point detection circuit as voltage zero cross point detection means for detecting a zero cross point of a voltage waveform.
[0013]
The ground wire 10 is provided in the S phase among the R, S, and T phases, and is B-type grounded. Further, the voltage zero cross point detection circuit 9 detects a voltage Vtr between the T phase and the R phase which is not grounded by a voltage detection means (not shown) as a power supply voltage, and detects a zero cross point from the waveform of the power supply voltage Vtr.
[0014]
For the sake of explanation, the microcomputer 5 shows calculation data (calculation information) and each calculation unit as blocks, and the data flow is indicated by arrows. In the figure, 11 is ground resistance value data, 12 is zero phase current zero cross point detection information, 13 is power supply voltage zero cross point detection information, 14 is a zero phase current effective value calculation unit, and 15 is a zero phase current phase calculation unit. , 16 is a sensitivity reference value calculation unit, 17 is a zero-phase current instantaneous value calculation unit, 18 is a ground fault current calculation unit, and 19 is a comparison unit.
The zero-phase current Io detection data is input to the microcomputer 5 via the A / D converter 7, and the detected zero-phase current Io is detected by the current zero-cross point detection circuit 8. A square wave signal Pi having the same phase as Io (hereinafter, zero-phase current zero-cross point information is referred to as Pi information) is input to the microcomputer 5. The detected zero cross point information of the power supply voltage Vtr is input to the microcomputer 5 as a square wave signal Pv having the same phase as the detected voltage (hereinafter, the power supply voltage zero cross point information is referred to as Pv information).
[0015]
In the case of a three-phase three-wire electric circuit that is Δ-connected based on the ground resistance Re, the zero-phase current Io, Pi information, and Pv information that is input in this way, the microcomputer 5 determines the ground resistance value Re that is input in advance and the current zero. The sensitivity reference value Is is set from the effective value Iorms of the phase current Io, and the power supply voltageVtrAn operation for sampling the zero-phase current Io waveform at a phase of 0 ° or 180 ° (hereinafter referred to as phase Φvo),
Io sampling value ≧ Is
In the case of, it is judged that leakage has occurred.
[0016]
The operation of the microcomputer 5 will be specifically described. First, the zero-phase current effective value Iorms is obtained from the zero-phase current Io value converted into digital data by an effective value calculation program. Based on the obtained zero-phase current effective value Iorms and the ground resistance Re data measured and set in advance, the current sensitivity reference value Is is obtained by a sensitivity reference value calculation program consisting of an arithmetic expression shown in Formula 1.
[0017]
[Expression 1]

[0018]
Here, the rated sensitivity current of the leakage detection device is 50 mA.
Further, based on the Pi information and the Pv information, the phase Φ of the zero-phase current Io when the power supply voltage Vtr is the phase Φvo is obtained by the phase calculation program consisting of the calculation formula shown in Equation 2.
[0019]
[Expression 2]

[0020]
Here, the phase Φvo is set to 180 ° for convenience.
Next, based on the obtained phase Φ, an instantaneous value Io (Φ) of the zero-phase current Io at the phase 180 ° of the power supply voltage Vtr is obtained by a program consisting of an arithmetic expression shown in Equation 3.
[0021]
[Equation 3]

[0022]
By this processing, the instantaneous value Io (Φ) of the zero-phase current Io at the phase 180 ° of the power supply voltage Vtr is sampled. Then, based on the zero-phase current instantaneous value Io (Φ) and the obtained current sensitivity reference value Is, the ground fault current Igr is obtained by a program composed of the ground fault current Igr calculation formula shown in Equation 4. Further, the obtained ground fault current Igr is displayed on the display device 4 by a display program.
[0023]
[Expression 4]

[0024]
Then, the obtained zero-phase current instantaneous value Io (Φ) is compared with the current sensitivity reference value Is, and when the zero-phase current instantaneous value Io (Φ) reaches the sensitivity reference value Is, it is determined that leakage has occurred and an alarm signal is generated. And the alarm device 3 such as a relay is operated.
[0025]
  Here, the basis of the above arithmetic expression will be described based on the simulation diagram of FIG. FIG. 4 is a graph created by simulating the instantaneous value Io (Φ) of the zero-phase current Io at the phase Φvo in a three-phase three-wire circuit having a Δ connection at a frequency of 50 Hz. The ground resistance value Re and the zero-phase current effective value Iorms are changed in the state where.
  From this simulation diagram, it can be seen that if the ground resistance Re and the zero-phase current Io are obtained, the zero-phase current instantaneous value Io (Φ) in the phase Φvo when the 50 mA leakage occurs can be specified..
[0026]
  From this, the zero-phase current instantaneous value Io (Φ) in the phase Φvo obtained from FIG. 4 can be set to the sensitivity reference value Is of the leakage detecting device when the rated sensitivity current is 50 mA.I understand that.In the above embodiment, the characteristic of FIG. 4 is approximated by an interpolation method or the like.Number 1The sensitivity reference value Is is obtained by calculation of the microcomputer 5.
  Here, the sensitivity reference value will be described. The sensitivity reference value when the sensitivity current is 50 mA refers to the instantaneous value Io (Φ) (the absolute value thereof) of the zero-phase current Io at the phase Φvo when the 50 mA leakage occurs. As shown in FIG. 4, the zero-phase current Io instantaneous value at the phase Φvo = the sensitivity reference value changes according to the B-type grounding resistance value RE and the zero-phase current value Iorms. On the contrary, the current sensitivity reference value Is can be obtained from the B-type grounding resistor RE and the current zero-phase current value Iorms using means such as the calculation based on Equation 1. Then, by separately measuring the current zero-phase current instantaneous value Io (Φ) in the phase Φvo and comparing this value with the current sensitivity reference value Is, it is possible to detect the occurrence of leakage of 50 mA or more. That is, when the zero-phase current instantaneous value Io (Φ) is smaller than the sensitivity reference value Is, the leakage current can be determined to be 50 mA or less, and when the zero-phase current instantaneous value Io (Φ) is larger than the sensitivity reference value Is, It can be determined that a leakage of 50 mA or more has occurred.
[0027]
  Specifically, FIG. 2 shows each waveform when leakage occurs in the T phase, and FIG. 3 shows each waveform when leakage occurs in the R phase.The vertical axis represents the current value in units of amperes, and the horizontal axis represents the phase angle of the ungrounded line voltage Vtr, which is the reference voltage, in units of degrees.In any case, the grounding resistance Re = 100Ω, the R-phase and T-phase ground capacitance CR = CT = 0.9556 μF, and the ground fault resistance Rg = 3900Ω,WhenSimulationresultIt is.In the simulation result column of Table 1 to be described later, the effective value of each waveform in FIGS. 1 and 2, the phase difference between the power supply voltage Vtr and the zero-phase current Io, and the instantaneous zero-phase current value Io (Φ) at the phase Φvo. Is shown.
[0028]
  Next, the ground fault current Igr is obtained by calculation only from the ground resistance Re and the effective value and phase information of the zero-phase current Io.In the case of T-phase leakage, the zero-phase current effective value Iorms = 133.4 mA,Substituting the ground resistance Re = 100Ω into Equation 1Sensitivity reference value Is = 73.6 mAGet. Also, the phase difference 22.3 ° between the power supply voltage Vtr and the zero-phase current Io is substituted into Equation 2, and the phase Φ = 157.7 ° of the zero-phase current Io when the power supply voltage phase is 180 ° is obtained. Substituting this into Equation 3A zero-phase current instantaneous value Io (Φ) = 71.5 mA when the power supply voltage phase is 180 ° is obtained.Finally, the obtained sensitivity reference value Is and the zero-phase current instantaneous value Io (Φ) are substituted into Equation 4,Ground fault current Igr = 48.6 mA(True value is also 48.6 mA).
  In the case of R phase leakage,Substituting the zero-phase current Io = 87.7 mA and the ground resistance Re = 100Ω into Equation 1 to obtain the sensitivity reference value Is = 65.5 mA. Further, by substituting 32.9 ° for the phase difference between the power supply voltage Vtr and the zero-phase current Io into Equation 2, the phase Φ = 147.1 ° of the zero-phase current Io when the power supply voltage phase is 180 ° is obtained. By substituting this into Equation 3, the zero-phase current instantaneous value Io (Φ) = 67.3 mA when the power supply voltage is 180 ° is obtained. Finally, the obtained sensitivity reference value Is and the zero-phase current instantaneous value Io (Φ) are substituted into Equation 4,Ground fault current Igr = 51.4 mA(True value is 51.2 mA).
  In the conventional technique shown in Patent Document 1, in the case of T-phase leakage, Igr = 58.4 mA from ground fault current Igr = Io (Φ) / (√2 sin 120 °), and in the case of R-phase leakage, Similarly, the ground fault current Igr = 54.9 mA.
[0029]
The results are summarized in Table 1. From this comparison result, the ground fault current Igr obtained from the calculation according to the above embodiment is Igr = 48.6 mA in the case of T-phase leakage, and Igr = 51.4 mA in the case of R-phase leakage. While current leakage is detected at a value close to 48.6 mA and 51.2 mA, in the conventional technology, Igr = 58.4 mA, or Igr = 54.9 mA, a value greatly deviating from the actual ground fault current value. It can be seen that
[0030]
[Table 1]

[0031]
In this way, the zero-phase current instantaneous value at the preset phase angle of the power supply voltage is obtained as the ground fault current equivalent value, and compared with the sensitivity reference value calculated based on the zero-phase current and the ground resistance value, the occurrence of leakage is determined. Therefore, even if the leakage current due to the ground capacitance always increases or the ground resistance value increases, the sensitivity reference value is changed accordingly, so it is always possible to compare and judge the ground fault current equivalent value with high accuracy, Electric leakage can be determined with high accuracy.
In addition, by setting the power supply voltage phase angle for calculating the ground fault current equivalent value to 180 °, the ground fault current equivalent value of the three-phase three-wire circuit can be easily obtained. Since it is obtained from the zero phase current phase and the zero phase current effective value at the preset phase angle of the power supply voltage, it can be obtained with high accuracy.
Furthermore, since the ground fault current value calculated by the display device is displayed, it is possible to grasp the leakage state at the time of occurrence of the leakage and effectively utilize it for recovery or the like.
[0032]
In the above embodiment, the power supply voltage phase Φvo for obtaining the instantaneous value Io (Φ) of the zero-phase current is calculated as 180 °, but it may be 0 °. Moreover, although the rated sensitivity current of the leakage detection device has been described as 50 mA, it can be applied to other rated sensitivity currents by changing the calculation formula of the sensitivity reference value Is or the like accordingly.
[0033]
FIG. 5 is a diagram showing a second embodiment of the leakage detection device, and shows a circuit block diagram of the leakage detection device applied to a single-phase three-wire electric circuit. In the figure, 21 is a zero-phase current transformer (ZCT) that detects the zero-phase current of the ground wire 30 provided in the N-phase of the neutral wire, 22 is an input device that inputs a ground resistance value, etc., and 23 is announcing the occurrence of electric leakage. The alarm device 24 is a display device for displaying a ground fault current value, and 25 is a microcomputer (hereinafter simply referred to as a microcomputer). Reference numeral 26 denotes an amplification circuit that amplifies the detected zero-phase current, 27 denotes an A / D converter, 28 denotes a current zero-cross point detection circuit that detects a zero-cross point of the zero-phase current waveform, and 29 denotes a zero-cross point of the power supply voltage waveform. Fig. 3 shows a shear voltage zero cross point detection circuit.
[0034]
The power supply voltage waveform zero cross point detection circuit 29 detects a voltage between the voltage lines X and Y by a voltage detection means (not shown), and detects a zero cross point from the waveform of the power supply voltage V.
[0035]
The microcomputer 25 shows calculation data (calculation information) and a calculation part with a block for description, and the data flow is shown with an arrow. In the figure, 31 is ground resistance value data, 32 is zero-phase current zero-cross point detection information, 33 is power-supply voltage zero-cross point detection information, 34 is a zero-phase current effective value calculation unit, and 35 is a leakage current due to ground capacitance. Is a voltage phase calculation unit for obtaining a power supply voltage phase Φco when the waveform of the constant leakage current Igc is zero-crossed, 36 is a phase calculation unit for zero phase current, 37 is a sensitivity reference value calculation unit, and 38 is an instantaneous value calculation of zero phase current. , 39 indicates a ground fault current calculation unit, and 40 indicates a comparison unit.
[0036]
The zero-phase current detection data is input to the microcomputer 25 via the A / D converter 27, and the detected zero-phase current Io is detected by the current zero-cross point detection circuit 28 as the zero-phase current detected by the zero-cross point information. A square wave signal Pi having the same phase (hereinafter, zero phase current zero cross point information is referred to as Pi information) is input to the microcomputer 25. The detected zero cross point information of the power supply voltage V is input to the microcomputer 25 as a square wave signal Pv having the same phase as the detected voltage (hereinafter, the power supply voltage zero cross point information is referred to as Pv information).
[0037]
As described above, in the case of a single-phase three-wire circuit based on the input ground resistance value Re, zero-phase current Io, Pi information, and Pv information, the microcomputer 25 determines that the input ground resistance value Re and the current The zero cross timing of the constantly leaking current Igc waveform flowing through the ground capacitance of the circuit is determined from the effective value Iorms of the zero phase current Io, and the sensitivity reference value Is is set from the specified zero cross timing, and the zero cross timing The Io waveform is sampled with and compared with the obtained sensitivity reference value Is,
Io sampling value ≧ Is
In the case of, it is judged that leakage has occurred.
[0038]
The operation of the microcomputer 25 will be specifically described. First, the zero-phase current effective value Iorms is obtained from the zero-phase current Io value converted into digital data by an effective value calculation program. Based on the obtained zero-phase current effective value Iorms and the input ground resistance data Re, the power supply voltage phase (hereinafter referred to as zero-crossing) when the leakage current Igc constantly zero-crosses by the calculation program consisting of the calculation formula shown in Formula 5. Voltage phase.) Find Φco.
[0039]
[Equation 5]

[0040]
And this zero cross voltage phase ΦcoBased onSensitivity consisting of the equation shown in Equation 6Standard valueA current sensitivity reference value Is is obtained by an arithmetic program.
[0041]
[Formula 6]

[0042]
It is programmed that the rated sensitivity current of the leakage detection device is 50 mA.
Further, based on the zero-cross voltage phase Φco, Pi information, and Pv information, the phase Φ of the zero-phase current Io when the phase of the power supply voltage V is the zero-cross voltage phase Φco from the phase calculation program consisting of the calculation formula shown in Equation 7 Ask for.
[0043]
[Expression 7]

[0044]
Next, the instantaneous value Io (Φ) of the zero-phase current Io at the calculated phase Φ is determined from a program consisting of an arithmetic expression shown in Equation 8.Since the instantaneous value Io (Φ) is the value of the zero-phase current Io at the moment when the leakage current Igc constantly crosses zero, if the phase of the ground fault current Igr is in phase with the power supply voltage phase, the ground fault current Igr It can be regarded as an instantaneous value in the phase Φco.
[0045]
[Equation 8]

[0046]
By this processing, the instantaneous value of the zero-phase current Io at the zero-cross voltage phase Φco of the power supply voltage V is sampled. Based on the zero-phase current instantaneous value Io (Φ) and the current sensitivity reference value Is, The ground fault current Igr is obtained by a program consisting of the calculation formula of the fault current Igr, and the obtained ground fault current Igr is displayed on the display device 24 by a display program.
[0047]
[Equation 9]

[0048]
Then, the obtained zero-phase current instantaneous value Io (Φ) is compared with the obtained current sensitivity reference value Is, and if the zero-phase current instantaneous value Io (Φ) reaches the sensitivity reference value Is, it is determined that leakage has occurred. Then, an alarm signal is output and the alarm device 23 such as a relay is operated.
[0049]
  Here, the basis of the above arithmetic expression will be described based on the simulation diagram of FIG. FIG. 8 shows a state where a ground fault current Igr = 50 mA is generated in a single-phase three-wire circuit having a frequency of 50 Hz, and changes the effective values of the ground resistance Re and the zero-phase current Io to change the zero-cross voltage phase Φco, that is, constantly. It is the figure created by simulating the power supply voltage phase when the leakage current Igc crosses zero. The change in the zero-phase current Io is caused by changing the ground capacitance on the X-phase side while keeping the ground-side capacitance on the Y-phase side constant.
  From this figure, it can be seen that the zero-cross voltage phase Φco can be specified from the ground resistance Re and the zero-phase current Io..
[0050]
  From FIG. 8, assuming that the ground fault current Igr is in phase with the power supply voltage phase, the instantaneous value of the ground fault current Igr at the zero cross voltage phase Φco when Igr = 50 mA is √2 × 50 × sin (Φco) This is the sensitivity reference value Is.(Equation 6). Precisely, it is the sensitivity reference value Is in the zero-cross voltage phase Φco of the leakage detection device with a rated sensitivity current of 50 mA. For example, in the leakage detection device with a rated sensitivity current of 50 mA, the sensitivity reference value Is when the zero cross voltage phase Φco = 95 ° is 70.4 mA.
  In the second embodiment, the characteristic of FIG. 8 is converted into an approximate expression by an interpolation method or the like, and the sensitivity reference value Is is obtained by calculation of a microcomputer.
The sensitivity reference value when the sensitivity current is 50 mA refers to the instantaneous value of the ground fault current Igr at the phase Φco when a leakage current of 50 mA occurs at a certain ground resistance and zero phase current. Then, by separately measuring the current instantaneous value Io (Φ) of the zero-phase current Io in the phase Φco and comparing this value with the current sensitivity reference value Is, it is possible to detect the occurrence of a leakage of 50 mA or more. That is, when the zero-phase current instantaneous value Io (Φ) is smaller than the sensitivity reference value Is, the leakage current can be determined to be 50 mA or less, and when it is larger than the sensitivity reference value Is, a leakage of 50 mA or more has occurred. I can judge.
[0051]
The change in the zero-phase current Io in FIG. 8 is obtained by fixing the Y-phase ground capacitance and changing the X-phase ground capacitance. In FIG. 8, the zero cross voltage phase Φco near 90 ° is shown, but naturally the zero cross timing of the leakage current Igc waveform always exists in the phase obtained by adding 180 ° to the zero cross voltage phase Φco.
[0052]
  Specifically, FIG. 6 shows each waveform when leakage occurs in the X phase, and FIG. 7 shows each waveform when leakage occurs in the Y phase.In both cases, the vertical axis represents the current value in units of amperes, the horizontal axis represents the phase angle of the power supply voltage, and the units are in degrees. AlsoGround resistance Re = 100Ω, ground fault resistance Rg = 1900Ω, X-phase ground capacitance Cx = 3.5 μF, Y-phase ground capacitance Cy = 0.5 μFdidCase simulationresultIt is.In the simulation result column of Table 2 described later, the effective value of each waveform in FIGS. 6 and 7 and the phase of the zero-phase current instantaneous value Io are shown.
[0053]
  Next, the ground fault current Igr is obtained by calculation only from the ground resistance Re and the effective value and phase information of the zero-phase current Io. In the case of the X-phase leakage, the zero-phase voltage phase Φco = 96.8 ° is obtained by substituting the zero-phase current Io = 101.8 mA and the ground resistance Re = 100Ω into Equation 5. By substituting this result into Equation 6, the sensitivity reference value Is = 70.2 mA is obtained. In addition, the zero-cross voltage phase Φco, the zero-phase current Io, and the phase difference 54.0 ° of the power supply voltage obtained in Equation 5 are substituted into Equation 7, and the zero-phase current phase Φ at the zero-cross voltage phase Φco = 150.8 ° Get. Then, by substituting this result into Equation 8, the zero-phase current instantaneous value Io (Φ) = 70.2 mA at the zero-cross voltage phase Φco is obtained. Finally, the obtained sensitivity reference value Is and the zero-phase current instantaneous value Io (Φ) are substituted into Equation 9 to obtain the ground fault current Igr = 50.0 mA (true value is 49.7 mA).
  In the case of Y-phase leakage, zero-phase voltage phase Φco = 96.8 ° is obtained by substituting zero-phase current Io = 101.8 mA and ground resistance Re = 100Ω into Equation 5. By substituting this result into Equation 6, the sensitivity reference value Is = 70.2 mA is obtained. Also, the zero-cross voltage phase Φco, the zero-phase current Io, and the phase difference 112.4 ° of the power supply voltage obtained in Equation 5 are substituted into Equation 7, so that the zero-phase current phase Φ = 29.4 ° in the zero-cross voltage phase Φco. Get. Then, by substituting this result into Equation 8, a zero-phase current instantaneous value Io (Φ) = 70.7 mA at the zero-cross voltage phase Φco is obtained. Finally, the obtained sensitivity reference value Is and the zero-phase current instantaneous value Io (Φ) are substituted into Equation 9 to obtain the ground fault current Igr = 50.4 mA (true value is 50.8 mA).
  In the conventional technique shown in Patent Document 2, in the case of X-phase leakage, ground fault current Igr = Io (Φ) × sin (Io phase + 90 °) to Igr = 59.8 mA, and in the case of Y-phase leakage Similarly, Igr = 38.8 mA.
[0054]
The results are summarized in Table 2. From this comparison result, the ground fault current Igr obtained from the calculation according to the above embodiment is Igr = 50.0 mA in the case of X-phase leakage and Igr = 50.4 mA in the case of Y-phase leakage. While current leakage is detected at a current value close to 49.7 mA and 50.8 mA, in the conventional technology, Igr = 59.8 mA or 38.8 mA, which is a value greatly deviating from the actual ground fault current value. You can see that
[0055]
[Table 2]

[0056]
Thus, the zero-phase current instantaneous value at the phase Φ when the leakage current Igc constantly crosses zero is obtained as the ground fault current equivalent value, and the instantaneous value at the phase Φco of the set rated sensitivity current is set as the sensitivity reference value. Since leakage is judged by comparing the two, even if the constant leakage current due to the ground capacitance increases or the ground resistance value increases, the sensitivity reference value changes accordingly, and the ground fault current is always accurate. Equivalent values can be compared and judged, and leakage can be accurately determined.
Also, by setting the power supply voltage phase angle for calculating the ground fault current to the power supply voltage phase based on the constant leakage current waveform, the ground fault current value of the single-phase three-wire circuit can be easily obtained. Since the ground fault current value is output, if the display device is provided, it is possible to grasp the leakage state at the time of occurrence of the leakage and effectively utilize it for recovery or the like.
[0057]
In any of the above embodiments, a zero-phase current transformer is provided on the ground line to detect the zero-phase current, but the zero-phase current may be detected directly from the electric circuit.
[0058]
【The invention's effect】
As described in detail above, according to the present invention, the zero-phase current instantaneous value at the preset phase angle of the power supply voltage is obtained as the ground fault current equivalent value, and the sensitivity calculated based on at least the zero-phase current and the ground resistance value. Since leakage is judged by comparing with the reference value, the sensitivity reference value is changed accordingly even if the constant leakage current due to the ground capacitance increases or the grounding resistance value increases. The ground fault current equivalent value can be compared and determined, and the leakage can be determined with high accuracy.
[0059]
In addition, by setting the power supply voltage phase angle for calculating the ground fault current to 180 °, the ground fault current value of the three-phase three-wire circuit can be easily obtained, and the ground fault current can be calculated. By setting the power supply voltage phase angle to the power supply voltage phase that is always based on the leakage current waveform, the ground fault current value of the single-phase three-wire circuit can be easily obtained.
Furthermore, since the calculated ground fault current value is output, if the display device is provided, the leakage state at the time of occurrence of the leakage can be grasped, and it can be effectively utilized for recovery or the like.
[Brief description of the drawings]
FIG. 1 is a block diagram of a leakage detection device provided in a three-phase three-wire circuit according to the first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing each waveform when a leakage occurs in the T phase of the three-phase three-wire circuit, and detecting the leakage by the leakage detection device of FIG. 1;
FIG. 3 is an explanatory diagram showing each waveform when a leakage occurs in the R phase of the three-phase three-wire circuit, and detecting the leakage by the leakage detection device of FIG. 1;
FIG. 4 is a diagram showing simulation data of a zero-phase current instantaneous value Io (Φ) of a three-phase three-wire circuit.
FIG. 5 is a block diagram of a leakage detection device provided in a single-phase three-wire circuit according to a second embodiment of the present invention.
6 is a diagram illustrating each waveform when a leakage occurs in the X phase of the single-phase three-wire circuit, and is an explanatory diagram for detecting the leakage by the leakage detection device of FIG. 5. FIG.
7 is a diagram illustrating each waveform when a leakage occurs in the Y phase of the single-phase three-wire circuit, and is an explanatory diagram for detecting the leakage by the leakage detection device of FIG. 5. FIG.
FIG. 8 is a diagram obtained by simulating a relationship between a power supply voltage phase and a ground resistance when a leakage current waveform constantly crosses zero in a single-phase three-wire circuit.
FIGS. 9A and 9B are waveform diagrams showing a state in which leakage occurs in the T phase of the conventional three-phase three-wire circuit, where FIG. 9A shows a case where the ground resistance is small and FIG. 9B shows a case where the ground resistance is large. .
[Explanation of symbols]
1 .. Zero phase current transformer 2.. Input device 5.. Microcomputer (computer) 8.. Current zero cross point detection circuit 9.. Voltage zero cross point detection circuit 10.・ Zero-phase current transformer 22 ・・ Input device 25 ・・ Microcomputer (28) ・・ Current zero-cross point detection detection circuit 29 ・・ Voltage zero-cross point detection circuit 30 ・・ Grounding line

Claims

Zero-phase current detection means, current zero-cross point detection means for detecting the zero-cross point of the zero-phase current waveform, voltage zero-cross point detection means for detecting the zero-cross point of the power supply voltage waveform, ground resistance value input means, and each of the above means A leakage calculation means for determining leakage based on the output of
The leakage calculation means calculates a zero-phase current instantaneous value at a preset phase angle of the power supply voltage from the ground resistance information set in advance, the detected zero-phase current information, the current zero-cross point information, and the voltage zero-cross point information. Calculate as ground fault current equivalent value,
Compare the ground fault current equivalent value with a sensitivity reference value calculated based on at least the zero-phase current and the ground resistance value, and determine the occurrence of leakage.
The sensitivity reference value is a zero-phase current at a preset phase angle of the power supply voltage when a leakage equal to the rated sensitivity current of the leakage detection device occurs under the same zero-phase current and grounding resistance conditions as the current one. A leakage detection device characterized by instantaneous values.

The leakage calculation means calculates the zero-phase current effective value from the zero-phase current information,
Based on the current zero-cross point information and the voltage zero-cross point information, the zero-phase current phase at the preset phase angle of the power supply voltage is calculated,
The instantaneous value of the zero phase current is calculated from the obtained zero phase current phase and the zero phase current effective value,
The leakage detecting device according to claim 1, wherein the obtained instantaneous value of the zero-phase current is compared with a sensitivity reference value as a ground fault current equivalent value.

3. The leakage detecting device according to claim 2, wherein the phase angle of the power supply voltage set in advance is a phase of the power supply voltage waveform of 0 ° or 180 ° in the Δ-connected three-phase three-wire circuit.