JP2004242404A

JP2004242404A - Leakage detector

Info

Publication number: JP2004242404A
Application number: JP2003027505A
Authority: JP
Inventors: Manabu Tsutsumi; 学堤
Original assignee: Kawamura Electric Inc
Current assignee: Kawamura Electric Inc
Priority date: 2003-02-04
Filing date: 2003-02-04
Publication date: 2004-08-26
Anticipated expiration: 2023-02-04
Also published as: JP3988932B2

Abstract

<P>PROBLEM TO BE SOLVED: To properly detect leakage, even in a circuit that is large in ground resistance and is further large in capacitance to ground. <P>SOLUTION: In a Δ-connected three-phase three-line system of circuit, this leakage detector detects a zero-phase current Io and information Pi about the zero-cross point of zero-phase current waveform from a zero-phase current transformer I, provided on a grounding conductor 10 and a current zero-cross point detecting circuit 8, and also detects information Pv about the voltage zero cross point of power voltage waveform between ungrounded two lines from a voltage zero-cross point detecting circuit 9, and inputs them into a microcomputer 5. The microcomputer 5 calculates the zero-phase current instantaneous value Io (Φ) at the phase 180° of power voltage waveform as a value equivalent to a grounding current, from the zero-phase current Io information, the current zero-cross point information Pi, and the voltage zero-cross point information Pv, and ground resistance Re value information inputted from an input device 2, and compares this value equivalent to the grounding current with a sensitiveness reference value Is which is computed, based on the zero-phase current effective value Iorms and the ground resistance Re value thereby judging the occurrence of leakage. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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することを特徴とする。
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。
【００１０】
請求項４の発明は、請求項２の発明において、単相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、常時漏洩電流波形を基準とする電源電圧位相であり、感度基準値は零相電流実効値と入力設定した接地抵抗値と更に前記常時漏洩電流波形を基準とする電源電圧位相とを基に算出されることを特徴とする。
この構成により、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。尚、常時漏洩電流とは、電路と大地間に発生する静電容量により生ずる漏洩電流をいう。
【００１１】
請求項５の発明は、請求項２乃至４の何れかの発明において、漏電演算手段は、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感度基準値から地絡電流値を演算して出力することを特徴とする。
この構成により、地絡電流値を表示する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。
【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間の位相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と、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、地絡電流Ｉｇｒを特定して各相の対地静電容量が同一なら、接地抵抗Ｒｅと零相電流Ｉｏが求まれば位相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、例えば定格感度電流５０ｍＡの漏電検出装置において、接地抵抗値Ｒｅ＝１００Ω、零相電流値実効値Ｉｏｒｍｓ＝１５０ｍＡの場合の感度基準値は７７．３ｍＡとなる。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。
【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。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、常時漏洩電流Ｉｇｃ＝１０１．３ｍＡとし、接地抵抗Ｒｅ及び常時漏洩電流Ｉｇｃを大きい値に設定した場合のシミュレーション値である。
【００２８】
この波形図から、Ｔ相漏電の場合、数１に基づく演算により、定格感度電流を５０ｍＡに設定した場合、感度基準値Ｉｓ＝７３．６ｍＡ、また電源電圧位相１８０°のときの零相電流瞬時値Ｉｏ（Φ）は図２から７１．５ｍＡであるため、数４に基づく演算により地絡電流Ｉｇｒ＝４８．６ｍＡ（図４のシミュレーションからの値はＩｇｒ＝４８．６ｍＡ）を得る。また、Ｒ相漏電の場合、数１に基づく演算により、感度基準値Ｉｓ＝６５．５ｍＡ、また電源電圧位相１８０°のときの零相電流瞬時値Ｉｏ（Φ）は図３から６７．３ｍＡ、であるため、数４に基づく演算により地絡電流Ｉｇｒ＝５１．４ｍＡ（図４のシミュレーションからの値はＩｇｒ＝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を数６に示す演算式からなる感度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。
【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た図である。この図から、地絡電流Ｉｇｒを特定すれば、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わかる。
【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。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。
【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。何れも、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、接地抵抗Ｒｅ及び常時漏洩電流Ｉｇｃを大きい値に設定（Ｘ相のＩｇｃ＝８７．３ｍＡ、Ｙ相のＩｇｃ＝９９．８ｍＡ）した場合のシミュレーション値である。
【００５３】
この波形図から、定格感度電流を５０ｍＡに設定した場合、Ｘ相漏電の場合、数６に基づく演算により、感度基準値Ｉｓ＝７０．２ｍＡ、また数５の演算で求めた電源電圧位相Φｃｏ＝９６．８°の時の零相電流瞬時値Ｉｏ（Φ）は図６から７０．２ｍＡであるため、数９に基づく演算により地絡電流Ｉｇｒ＝５０．０ｍＡ（図８のシミュレーションからの値はＩｇｒ＝４９．７ｍＡ）を得る。また、Ｙ相漏電の場合、数６に基づく演算により、感度基準値Ｉｓ＝７０．２ｍＡ、また、数５の演算で求めた電源電圧位相Φｃｏ＝９６．８°の時の零相電流瞬時値Ｉｏ（Φ）は図７から７０．７ｍＡであるため、数９に基ずく演算により地絡電流Ｉｇｒ＝５０．４ｍＡ（図８のシミュレーションからの値はＩｇｒ＝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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a leakage detection device that detects leakage of an electric circuit, and more particularly to a leakage detection device that detects leakage of a three-phase three-wire circuit and a single-phase three-wire circuit.
[0002]
[Prior art]
For example, a conventional leakage detecting device of a three-phase three-wire circuit has a configuration shown in Patent Document 1, and a conventional leakage detecting device of a single-phase circuit has a structure shown in Patent Document 2. Both are technologies proposed by the present inventors, and are proposed by the present inventors to solve the problem that the sensitivity is deteriorated when the constant leakage current due to the ground capacitance, which the leak detection device had so far, has increased. In Patent Document 1, the zero-phase current Io waveform is sampled at a fixed timing of 0 ° or 180 ° of the non-ground line voltage phase, and the ground fault current Igr is detected. In Patent Document 2, the zero-phase current Io waveform is sampled at a fixed timing of 90 ° or 270 ° of the power supply voltage phase to detect the ground fault current Igr.
[0003]
[Patent Document 1]
JP-A-6-57037 [Patent Document 2]
Published Japanese Utility Model Application No. Hei 6-57036
[Problems to be solved by the invention]
However, the techniques of

Patent Documents

1 and 2 can detect the ground fault current Igr well in a three-phase three-wire circuit or a single-phase three-wire circuit when the ground resistance is small, but the ground resistance is 100Ω. In such a case, the balance of the ground capacitance of each phase may be lost, or the total ground capacitance may increase, and the leakage current of the entire electric circuit (constant leakage current Igc) may occur. Becomes larger, the lag phase of the leakage current becomes larger, so that the difference between the zero-phase current value sampled at the above timing and the actual ground fault current value becomes larger, causing a problem of malfunction.
[0005]
FIG. 9 is a waveform chart for explaining each phase 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 the case where the ground resistance is as small as, for example, 10Ω, and (b) shows the case where the ground resistance is as large as, for example, 100Ω. The zero-phase current Io at 180 ° phase of the constant leakage current Igc in phase with the power supply voltage is shown. 9 (a) overlaps with the ground fault current Igr in FIG. 9 (a), but in FIG. Therefore, a large error occurs. This feature was the same for a single-phase three-wire circuit.
[0006]
In view of the above problems, it is an object of the present invention to provide a leakage detection device capable of detecting leakage current satisfactorily even on an electric circuit having a large ground resistance and a large earth capacitance.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention according to claim 1 includes a zero-phase current detection means, a current zero-cross point detection means for detecting a zero-cross point of a zero-phase current waveform, and a voltage zero-cross check 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 of the means. 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 power supply voltage phase angle is calculated as a ground fault current equivalent value. It is characterized in that occurrence of electric leakage is determined by comparing with a sensitivity reference value calculated based on the phase current and the ground resistance value.
With this configuration, 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 equivalent value can always be compared and determined with high accuracy. The leakage can be judged well.
[0008]
According to a second aspect of the present invention, in the first aspect of the invention, the leakage calculating means calculates a zero-phase current effective value from the zero-phase current information, and sets the effective value in advance 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 obtained zero-phase current phase and the zero-phase current effective value, and calculate the instantaneous value of the obtained zero-phase current. It is characterized in that it is compared with a sensitivity reference value as a ground fault current equivalent value.
With this configuration, the ground fault current equivalent value can be accurately calculated.
[0009]
According to a third aspect of the present invention, in the second aspect of the present invention, in the three-phase three-wire circuit connected by Δ, the preset power supply voltage phase angle is 0 ° or 180 ° of the power supply voltage waveform phase. There is a feature.
By setting the power supply voltage phase angle for calculating the ground fault current to 180 ° as described above, the ground fault current value of the three-phase three-wire circuit can be easily obtained.
[0010]
According to a fourth aspect of the present invention, in the second aspect of the present invention, in the single-phase three-wire circuit, the preset phase angle of the power supply voltage is a power supply voltage phase that is always based on the leakage current waveform, and the sensitivity is high. The reference value is calculated based on a zero-phase current effective value, an input and set ground resistance value, and a power supply voltage phase based on the constant leakage current waveform.
With this configuration, the ground fault current value of the single-phase three-wire circuit can be easily obtained. In addition, the constant leakage current refers to a leakage current generated by a capacitance generated between the electric circuit and the ground.
[0011]
According to a fifth aspect of the present invention, in any one of the second to fourth aspects of the present invention, the earth leakage calculating means calculates a ground fault current value from a zero-phase current instantaneous value and a sensitivity reference value at a preset phase angle of the power supply voltage. Output.
According to this configuration, if a display device for displaying a ground fault current value is provided, the state of leakage at the time of occurrence of leakage can be grasped, and can be effectively used for recovery or the like.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present 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 device 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 line

10, 2 is an input device as an input means for inputting a ground resistance Re value and the like, and 3 is an input device. 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 electric leakage calculating means. Reference numeral 6 denotes an amplifier 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 supply. 2 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 line 10 is provided in the S phase of the R, S, and T phases, and is grounded to the B class. The voltage zero-cross point detection circuit 9 detects a voltage Vtr between the T phase and the R phase that is not grounded as a power supply voltage by a voltage detection means (not shown), and detects a zero cross point from the waveform of the power supply voltage Vtr.
[0014]
The microcomputer 5 shows operation data (operation information) and each operation unit by blocks for explanation, and the flow of data is indicated by arrows. In the figure, 11 indicates ground resistance value data, 12 indicates zero-phase current zero-crossing point detection information, 13 indicates power supply voltage zero-crossing point detection information, 14 indicates a zero-phase current effective value calculation unit, and 15 indicates a zero-phase current phase calculation unit. , 16 a sensitivity reference value calculator, 17 a zero-phase current instantaneous value calculator, 18 a ground fault current calculator, and 19 a comparator.
Then, 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-crossing point detection circuit 8. It is input to the microcomputer 5 as 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). Further, 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]
Based on the ground resistance Re, zero-phase current Io, Pi information, and Pv information thus input, in the case of a three-phase three-wire circuit connected by Δ, the microcomputer 5 determines the ground resistance Re input in advance and the current zero. A sensitivity reference value Is is set from the effective value Iorms of the phase current Io, and a calculation is performed to sample the zero-phase current Io waveform at a phase of 0 ° or 180 ° (hereinafter referred to as a phase Φvo) between the power supply voltages Vtr. ,
Io sampling value ≧ Is
In the case of, it is determined that a short circuit has occurred.
[0016]
More specifically, the operation of the microcomputer 5 will be 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 data of the grounding resistance Re measured and set in advance, the current sensitivity reference value Is is obtained by a sensitivity reference value calculation program comprising a calculation formula shown in Expression 1.
[0017]
(Equation 1)

[0018]
Here, the rated sensitivity current of the leakage detection device is set to 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 a phase calculation program consisting of a calculation formula shown in Expression 2.
[0019]
(Equation 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 a phase of 180 ° of the power supply voltage Vtr is obtained by a program comprising an arithmetic expression shown in Expression 3.
[0021]
[Equation 3]

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

[0024]
Then, the obtained zero-phase current instantaneous value Io (Φ) is compared with the current sensitivity reference value Is. 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 issued. Is output, and the alarm device 3 such as a relay is operated.
[0025]
Here, the basis of the above arithmetic expression will be described with reference to the simulation diagram of FIG. 4. FIG. 4 shows that the instantaneous value Io () of the zero-phase current Io at the phase φvo in a three-phase three-wire circuit with a frequency of 50 Hz and Δ connection. Is a graph created by simulating Φ), in which a ground resistance value Re and a zero-phase current effective value Iorms are changed in a state where a ground fault current Igr = leakage of 50 mA is generated.
From this simulation diagram, if the ground fault current Igr is specified and the ground capacitance of each phase is the same, the ground resistance Re and the zero-phase current Io are obtained, and the zero-phase current instantaneous value Io (Φ) in the phase Φvo is specified. Understand what you can do.
[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 detection device when the rated sensitivity current is 50 mA. In the detection device, when the ground resistance value Re = 100Ω and the zero-phase current value effective value Iorms = 150 mA, the sensitivity reference value is 77.3 mA. In the above embodiment, the characteristic shown in FIG. 4 is converted into an approximate expression by an interpolation method or the like, and the sensitivity reference value Is is obtained by the calculation of the microcomputer 5.
[0027]
Explaining specifically with waveform diagrams, FIG. 2 shows respective waveforms when a leakage occurs in the T phase, and FIG. 3 shows respective waveforms when a leakage occurs in the R phase. In each case, the ground resistance Re = 100Ω, the R-phase and T-phase capacitances to ground CR = CT = 0.965 μF, the ground fault resistance Rg = 3900Ω, the constant leakage current Igc = 101.3 mA, the ground resistance Re and the constant leakage This is a simulation value when the current Igc is set to a large value.
[0028]
From this waveform diagram, in the case of T-phase leakage, when the rated sensitivity current is set to 50 mA by calculation based on Equation 1, the sensitivity reference value Is = 73.6 mA, and the zero-phase current instantaneous when the power supply voltage phase is 180 °. Since the value Io (Φ) is 71.5 mA from FIG. 2, a ground fault current Igr = 48.6 mA (the value from the simulation in FIG. 4 is Igr = 48.6 mA) is obtained by the calculation based on Equation 4. In the case of an R-phase leakage, the sensitivity reference value Is = 65.5 mA and the zero-phase current instantaneous value Io (Φ) at a power supply voltage phase of 180 ° are 67.3 mA from FIG. Therefore, the ground fault current Igr = 51.4 mA (the value from the simulation in FIG. 4 is Igr = 51.2 mA) is obtained by the calculation based on Equation 4.
According to the conventional technique disclosed 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]
Table 1 summarizes the results. From this comparison result, the ground fault current Igr obtained by the calculation according to the above embodiment is as follows: Tgr = 48.6 mA for T-phase leakage, Igr = 51.4 mA for R-phase leakage, and an actual ground fault While current leakage is detected at a current value of 48.6 mA or a value close to 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 turns out that it shows.
[0030]
[Table 1]

[0031]
In this way, the instantaneous value of the zero-phase current at the preset phase angle of the power supply voltage is obtained as the ground fault current equivalent value, and the occurrence of the earth leakage is determined by comparing the zero-phase current with the sensitivity reference value calculated based on the ground resistance value. Therefore, even if the constant leakage current due to the ground capacitance increases, and even if the ground resistance increases, the sensitivity reference value changes accordingly, so that the ground fault current equivalent value can always be compared and determined with high accuracy. Leakage can be determined with high accuracy.
Further, 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 effective zero-phase current value at a preset phase angle of the power supply voltage, it can be obtained with high accuracy.
Further, since the display device displays the calculated ground fault current value, it is possible to grasp the state of the earth leakage at the time of occurrence of the earth leakage, and it can be effectively used 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 may be set to 0 °. In addition, although the rated sensitivity current of the leakage detection device has been described as 50 mA, the present invention can be applied to other rated sensitivity currents by changing the arithmetic expression of the sensitivity reference value Is and the like.
[0033]
FIG. 5 is a diagram showing a second embodiment of the earth leakage detection device, and shows a circuit block diagram of the earth leakage detection device applied to a single-phase three-wire circuit. In the figure, reference numeral 21 denotes a zero-phase current transformer (ZCT) for detecting a zero-phase current of a ground wire 30 provided in a neutral line N-phase; 22, an input device for inputting a ground resistance value and the like; Reference numeral 24 denotes a display device for displaying a ground fault current value, and 25 denotes a microcomputer (hereinafter simply referred to as a microcomputer). 26 is an amplifier circuit for amplifying the detected zero-phase current, 27 is an A / D converter, 28 is a current zero-cross point detection circuit for detecting a zero-cross point of the zero-phase current waveform, and 29 is a zero-cross point of the power supply voltage waveform. 3 illustrates a shear voltage zero cross point detection circuit.
[0034]
The zero-cross point detection circuit 29 of the power supply voltage waveform detects the voltage between the voltage lines X and Y by voltage detection means (not shown), and detects the zero-cross point from the waveform of the power supply voltage V.
[0035]
The microcomputer 25 shows operation data (operation information) and operation units by blocks for explanation, and the flow of data is indicated by arrows. In the figure, 31 indicates ground resistance data, 32 indicates zero-phase current zero-crossing point detection information, 33 indicates power supply voltage zero-crossing point detection information, 34 indicates a zero-phase current effective value calculation unit, and 35 indicates leakage current due to capacitance to ground. , A voltage phase calculator for calculating the power supply voltage phase Φco when the waveform of the constant leakage current Igc crosses zero, 36 is a phase calculator for the zero-phase current, 37 is a sensitivity reference value calculator, and 38 is an instantaneous value calculation of the zero-phase current. , 39 denotes a ground fault current calculation unit, and 40 denotes a comparison unit.
[0036]
Then, 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 compared with the zero-phase current detected by the zero-cross point information by the current zero-cross point detection circuit 28. The in-phase square wave signal Pi (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, based on the input ground resistance Re, zero-phase current Io, Pi information, and Pv information, in the case of a single-phase three-wire circuit, the microcomputer 25 compares the ground resistance Re input in advance with the current ground resistance Re. From the effective value Iorms of the zero-phase current Io, the zero-cross timing of the waveform of the continuous leakage current Igc flowing through the earth capacitance of the electric circuit is specified, and the sensitivity reference value Is is set from the specified zero-cross timing, and the zero-cross timing is set. The Io waveform is sampled by comparing with the obtained sensitivity reference value Is,
Io sampling value ≧ Is
In the case of, it is determined that a short circuit 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 and set data of the ground resistance Re, a power supply voltage phase (hereinafter referred to as zero crossing) when the leakage current Igc always crosses zero by a calculation program including a calculation formula shown in Expression 5 Φco is obtained.
[0039]
(Equation 5)

[0040]
Then, the current sensitivity reference value Is is obtained from the zero-cross voltage phase Φco by a sensitivity calculation program including a calculation formula shown in Expression 6.
[0041]
(Equation 6)

[0042]
In addition, the rated sensitivity current of the leakage detection device is programmed as 50 mA.
Also, 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 is obtained from the phase calculation program consisting of the calculation formula shown in Expression 7. Ask for.
[0043]
(Equation 7)

[0044]
Next, an instantaneous value Io (Φ) of the zero-phase current Io at the above-mentioned phase Φ is obtained from a program comprising an arithmetic expression shown in Expression 8.
[0045]
(Equation 8)

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

[0048]
Then, the calculated instantaneous zero-phase current value Io (Φ) is compared with the obtained current sensitivity reference value Is. If the instantaneous zero-phase current value Io (Φ) has reached the sensitivity reference value Is, it is determined that an electric leakage has occurred. And outputs an alarm signal to operate an alarm device 23 such as a relay.
[0049]
Here, the basis of the above arithmetic expression will be described based on the simulation diagram of FIG. FIG. 8 shows a state in which a ground fault current Igr = 50 mA is leaked in a single-phase three-wire circuit with a frequency of 50 Hz, and the effective value of the ground resistance Re and the zero-phase current Io is changed to change the zero-cross voltage phase Φco, that is, at all times. FIG. 9 is a diagram simulating a power supply voltage phase when a leakage current Igc crosses zero. From this figure, it is understood that if the ground fault current Igr is specified, 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) And this is the sensitivity reference value Is. To be more precise, it is the sensitivity reference value Is at the zero-cross voltage phase Φco of the leakage detection device having the rated sensitivity current of 50 mA. For example, in a leakage detection device having a rated sensitivity current of 50 mA, the sensitivity reference value Is at the time of zero cross voltage phase Φco = 95 ° is 70.4 mA.
In the second embodiment, the characteristic shown in FIG. 8 is converted into an approximate expression by an interpolation method or the like, and the sensitivity reference value Is is obtained by an operation of the microcomputer.
[0051]
The change in the zero-phase current Io in FIG. 8 is obtained by fixing the ground capacitance of the Y phase and changing the ground capacitance of the X phase. FIG. 8 shows a zero-cross voltage phase Φco near 90 °, but a zero-cross timing of the leakage current Igc waveform always exists in a phase obtained by adding 180 ° to the zero-cross voltage phase Φco.
[0052]
Specifically, referring to waveform diagrams, FIG. 6 shows respective waveforms when a leakage occurs in the X phase, and FIG. 7 shows respective waveforms when a leakage occurs in the Y phase. In each case, the ground resistance Re = 100Ω, the ground fault resistance Rg = 1900Ω, the X-phase ground capacitance Cx = 3.5 μF, the Y-phase ground capacitance Cy = 0.5 μF, the ground resistance Re and the constant leakage This is a simulation value when the current Igc is set to a large value (Igc for X phase = 87.3 mA, Igc for Y phase = 99.8 mA).
[0053]
From this waveform diagram, when the rated sensitivity current is set to 50 mA, in the case of X-phase leakage, the sensitivity reference value Is = 70.2 mA by the calculation based on Expression 6, and the power supply voltage phase Φco = Since the instantaneous zero-phase current value Io (Φ) at 96.8 ° is 70.2 mA from FIG. 6, the ground fault current Igr = 50.0 mA (the value from the simulation in FIG. Igr = 49.7 mA). In the case of the Y-phase leakage, the sensitivity reference value Is = 70.2 mA by the calculation based on the expression 6, and the instantaneous zero-phase current value when the power supply voltage phase Φco = 96.8 ° obtained by the calculation of the expression 5 Since Io (Φ) is 70.7 mA from FIG. 7, the ground fault current Igr = 50.4 mA (the value from the simulation in FIG. 8 is Igr = 50.8 mA) is obtained by the calculation based on Expression 9.
In the conventional technique disclosed in Patent Document 2, in the case of X-phase leakage, Igr = 59.8 mA from ground fault current Igr = Io (Φ) × sin (Io phase + 90 °), and in the case of Y-phase leakage. Similarly, Igr = 38.8 mA.
[0054]
Table 2 summarizes the results. From this comparison result, the ground fault current Igr obtained from the calculation according to the above-described embodiment is as follows: 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 value close to the current value of 49.7 mA and 50.8 mA, the conventional technique uses Igr = 59.8 mA or 38.8 mA, which is a value greatly deviating from the actual ground fault current value. It turns out that it shows.
[0055]
[Table 2]

[0056]
In this way, the instantaneous value of the zero-phase current at the phase Φ when the leakage current Igc always crosses zero is obtained as the ground fault current equivalent value, and the instantaneous value of the set rated sensitivity current at the phase Φco is set as the sensitivity reference value, Since both sides are compared to determine the occurrence of earth leakage, even if the leakage current due to the earth capacitance is large or the ground resistance value is large, the sensitivity reference value is changed accordingly, and the ground fault current is always accurate. The equivalent values can be compared and determined, and the leakage can be accurately determined.
Further, by setting the power supply voltage phase angle for calculating the ground fault current to the power supply voltage phase with the leakage current waveform as a reference at all times, 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, the state of the earth leakage at the time of occurrence of the earth leakage can be grasped, and it can be effectively used for recovery or the like.
[0057]
In each 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 directly detected from the electric circuit.
[0058]
【The invention's effect】
As described in detail above, according to the present invention, the instantaneous value of the zero-phase current at the preset phase angle of the power supply voltage is determined 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 the occurrence of electric leakage is judged by comparing with the reference value, even if the leakage current due to the capacitance to the ground always increases, and even if the ground resistance value increases, the sensitivity reference value changes accordingly, so it is always accurate. The ground fault current equivalent value can be compared and determined, and the leakage can be accurately determined.
[0059]
Further, 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 based on the leakage current waveform at all times, the ground fault current value of the single-phase three-wire circuit can be easily obtained.
Further, since the calculated ground fault current value is output, if the display device is provided, the state of the leakage at the time of the occurrence of the leakage can be grasped and can be effectively used for recovery or the like.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of the present invention, and is a block diagram of a leakage detection device provided in a three-phase three-wire circuit.
FIG. 2 is a diagram illustrating waveforms when a leakage occurs in a T-phase of a three-phase three-wire circuit, and is an explanatory diagram of detecting a leakage by the leakage detection device of FIG. 1;
FIG. 3 is an explanatory diagram showing waveforms when a leakage occurs in the R phase of a three-phase three-wire circuit, and detecting 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 shows a second embodiment of the present invention, and is a block diagram of a leakage detection device provided in a single-phase three-wire circuit.
6 is a diagram illustrating waveforms when a leakage occurs in the X-phase of a single-phase three-wire circuit, and illustrates leakage detection by the leakage detection device of FIG. 5;
7 is a diagram illustrating waveforms when a leakage occurs in the Y-phase of a single-phase three-wire circuit, and is a diagram illustrating leakage detection by the leakage detection device of FIG. 5;
FIG. 8 is a diagram obtained by simulating a relationship between a power supply voltage phase and a ground resistance when a zero leakage current waveform always crosses in a single-phase three-wire circuit.
9A and 9B are waveform diagrams showing a state in which a leakage has occurred in the T phase of a conventional three-phase three-wire circuit. 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, 8. Current zero-cross point detection circuit, 9. Voltage zero-cross point detection circuit, 10. Ground line, 21. -Zero-phase current transformer, 22-Input device, 25-Microcomputer (microcomputer), 28-Current zero-cross point detection circuit, 29-Voltage zero-cross point detection circuit, 30-Ground line.

Claims

Zero-phase current detection means, current zero-cross point detection means for detecting a zero-cross point of a zero-phase current waveform, voltage zero-cross point detection means for detecting a zero-cross point of a power supply voltage waveform, ground resistance input means, And a leakage calculating means for determining leakage based on the output of
The earth leakage calculating means calculates a zero-phase current instantaneous value at a preset power supply voltage phase angle from the previously input ground resistance information, the detected zero-phase current information, the current zero-cross point information, and the voltage zero-cross point information. Calculate as the ground fault current equivalent value,
An earth leakage detection device characterized by comparing the ground fault current equivalent value with a sensitivity reference value calculated based on at least a zero-phase current and a ground resistance value to determine occurrence of earth leakage.

The leakage calculating means calculates a 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, calculate a zero-phase current phase at a preset power supply voltage phase angle,
Calculate the instantaneous value of the zero-phase current from the obtained zero-phase current phase and the zero-phase current effective value,
2. The leakage detection device according to claim 1, wherein the instantaneous value of the obtained zero-phase current is compared with a sensitivity reference value as a ground fault current equivalent value.

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

In a single-phase three-wire circuit, the preset phase angle of the power supply voltage is the power supply voltage phase with reference to the leakage current waveform at all times, and the sensitivity reference value is the zero-phase current effective value and the ground resistance input and set. 3. The leakage detection device according to claim 2, wherein the leakage current detection device is calculated based on a value and a power supply voltage phase based on the constant leakage current waveform.

5. The leakage detection device according to claim 2, wherein the leakage calculation means calculates and outputs a ground fault current value from a zero-phase current instantaneous value and a sensitivity reference value at a preset phase angle of the power supply voltage.