JP2004241530A

JP2004241530A - Zero phase-sequence current transformer

Info

Publication number: JP2004241530A
Application number: JP2003027920A
Authority: JP
Inventors: Takahiro Kudo; 高裕工藤; Tadashi Asada; 浅田　　規
Original assignee: Fuji Electric Holdings Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 2003-02-05
Filing date: 2003-02-05
Publication date: 2004-08-26
Anticipated expiration: 2023-02-05
Also published as: JP4158542B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-size zero phase-sequence current transformer with an overcurrent detecting function which detects grounding current which flows when there is an earth fault accident in electric power transmission and distribution lines or there is an electric shock. <P>SOLUTION: The zero phase-sequence current transformer comprises a plurality of primary conductors and magnetic sensors in the same number as that of the primary conductors. The plurality of primary conductors have different diameters. All the primary conductors except for the one having the smallest diameter are annular conductors. The primary conductor having the smallest diameter may be either annular or circular cylindrical. All the primary conductors are so arranged that the centers may nearly coincide with each other. Outside each of the primary conductors, one magnetic sensor is located. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、送配電線路において地絡事故が生じたり、感電があった場合に流れる地絡電流を検出する零相変流器に関する。
【０００２】
【従来の技術】
従来の電流トランス型零相変流器を示す構成図を図６に示す。電流トランス型零相変流器は、パーマロイなどの高透磁率材料により構成される環状鉄芯１３の全周にわたって出力巻線１４が巻回されており、一次導体６ａ、６ｂ、６ｃは環状鉄芯１３の中空部を貫通するように配置される。
零相変流器の地絡検出原理は、三相平衡状態（地絡が発生していない状態）ではＲ相導体６ａ、Ｓ相導体６ｂ、Ｔ相導体６ｃに流れるＲ相電流Ｉｒ、Ｓ相電流Ｉｓ、Ｔ相電流Ｉｔの総和が常に零であり、環状鉄芯１３内に発生する磁束は互いに打ち消し合って出力巻線１４には電圧は誘起されないが、地絡が発生した場合には、各相の電流の総和は零ではなくなり、環状鉄芯１３内に地絡電流に応じた磁束が発生し出力巻線１４に電圧が誘起されることにある。
【０００３】
零相変流器にシールドを施し、外部ノイズでの電子回路部品の誤動作を防止した漏電遮断器の漏電電流検出装置がある（例えば、特許文献１参照）。
また、三相交流電路において、零相変流器が不平衡出力を出すような過渡的大電流領域における誤動作防止を有した漏電遮断器の構成が示されている（例えば、特許文献２参照）。
通常、出力巻線１４は数千ターン巻き回す必要があるので、小型化に限界があるという問題があった。そこで、従来の電流トランス型に代わるものとして、環状鉄芯中に高感度な磁気インピーダンス素子を配置するものがある（例えば、特許文献３参照）。
【０００４】
従来の零相変流器端子構成を図７に示し、（ａ）は斜視図であり、（ｂ）は正面図、（ｃ）はＲ相端子のみを上部から見た図である。Ｒ相端子１０ａ、１００ａと、Ｓ相端子１０ｂ、１００ｂと、Ｔ相端子１０ｃ、１００ｃは、零相変流器１１内部に図７（ｂ）のように配置された、３本の円柱の各一次導体６ａ、６ｂ、６ｃにそれぞれ接続され、零相零相変流器１１の両側に対して、対象な端子構造を持っていた。
【０００５】
【特許文献１】
特開平８−３２１２４９号公報（第５−６頁、第１−５図）
【特許文献２】
特開平９−９３７９０号公報（第３−４頁、第１−５図）
【特許文献３】
特開平１０−２３２２５９号公報（第２−３頁、第１図）
【０００６】
【発明が解決しようとする課題】
しかしながら、従来の電流トランス型は、出力巻線により環状鉄芯内の磁束を周回積分するので、導体の位置による出力変化が少ないのに対して、特許文献３に開示されている方法は、磁束を周回積分できないので、導体の位置による出力変化が大きく、各導体からのアンペールの法則で発生する磁束の影響を受け易いために残留電流が増大するという問題があった。
また、零相変流器は通常、漏電遮断器に搭載されるが、漏電遮断器に要求される機能としては、地絡検出の他に、各相の過電流検出がある。しかし、従来の零相変流器では前述の原理にて検出を行っているため、過電流検出は不可能であった。そのため、過電流検出のために別途、カレントトランスもしくはバイメタルを用いた機械式の過電流検出機構が必要であった。
【０００７】
更に、一次導体６ａ、６ｂ、６ｃに接続する端子構造は、その取り出しの容易性から、一次導体６ａ、６ｂ、６ｃの長さ方向の中心に対して線対称の位置に端子を設ける図７に示した構成が容易に考えられる。しかし、図７（ｃ）に示すように、零相変流器１１の本体内部に位置する、導体６ａの内部では、電流密度の高い部分と低い部分とが存在することでの、導体を通過する電流密度の不均一性が著しく起こっていることが、磁場解析で明らかとなっており、３相平衡時の地絡電流が発生しない場合には、理想的には出力は現れないが、電流密度の不均一により、残留電流と呼ばれる出力が発生することで、地絡電流が流れた場合の出力との差を低下させる原因となるという問題があった。
【０００８】
本発明の課題は、前記の問題を解決し、小型の過電流検出機能付零相変流器を提供するである。
【０００９】
【課題を解決するための手段】
上記課題を解決するために、少なくとも２つの一次導体と、少なくとも２つの磁気センサにより構成される零相変流器において、
少なくとも２つの前記一次導体は径の異なる導体であって、最小径である前記一次導体を除く少なくとも１つの前記一次導体は環状導体であって、すべての前記一次導体は中心位置を同一にして配置し、すべての前記一次導体の外側に１つずつ前記磁気センサを設けることにする。
この際に、少なくとも２つの前記磁気センサのうち、最外郭導体の近傍に配置した前記磁気センサに磁気インピーダンス素子を用いて、他の前記磁気センサにホール素子または磁気抵抗素子を用いることにする。
【００１０】
少なくとも２つの一次導体と、少なくとも２つの磁気センサにより構成される零相変流器において、
少なくとも２つの前記一次導体は径の異なる導体であって、最小径である前記一次導体を除く少なくとも１つの前記一次導体は環状導体であって、すべての前記一次導体は中心位置を同一にして配置し、前記一次導体の外側に前記一次導体と中心位置をほぼ同一とする第一環状鉄芯を設け、少なくとも２つ前記一次導体で挟まれる間に１つずつ前記磁気センサを設け、前記第一環状鉄芯の外側に前記磁気センサを設けたことにする。
【００１１】
この際に、前記第一環状鉄芯の外側に配置した前記磁気センサに磁気インピーダンス素子を用いて、他の前記磁気センサにホール素子または磁気抵抗素子を用いることにする。
少なくとも２つの一次導体と、少なくとも２つの磁気センサにより構成される零相変流器において、
少なくとも２つの前記一次導体は径の異なる導体であって、最小径である前記一次導体を除く少なくとも１つの前記一次導体は環状導体であって、すべての前記一次導体は中心位置を同一にして配置し、前記一次導体の外側に前記一次導体と中心位置をほぼ同一とする第一環状鉄芯を設け、前記第一環状鉄芯の外側に前記一次導体と中心位置をほぼ同一とする第二環状鉄芯をそれぞれ設け、少なくとも２つ前記一次導体で挟まれる間に１つずつ前記磁気センサを設け、前記第二環状鉄芯に切欠部を設けて前記切欠部に前記磁気センサを配置したことにする。
【００１２】
この際に、前記第二環状鉄芯の切欠部に配置した前記磁気センサに磁気インピーダンス素子を用いて、他の前記磁気センサにホール素子または磁気抵抗素子を用いることにする。
また、最小径である前記一次導体が、円柱導体または環状導体であることにする。
さらに、前記一次導体は両端に接続バーを介して端子を有し、前記一次導体両端での前記端子の位置関係は前記一次導体に対して点対称であって、少なくとも２つの各前記一次導体に対する各前記端子間における導体断面と経路長を変更して、それぞれの端子間の電気抵抗を同等とする構成とすることにする。
【００１３】
また、前記一次導体両側に対する一方または他方に位置する各前記端子の高さは同一であって、前記一次導体を介して両端に配置された前記端子の高さは異なることにする。
また、前記接続バーは、前記一次導体の両側で長さが異なることにする。
次いで、前記磁気センサとして磁気インピーダンス素子を用いたことにする。
【００１４】
【発明の実施の形態】
図１は、本発明の第一の実施例を示す基本配置構成図であり、（ａ）は断面図で（ｂ）は側面図、（ｃ）はセンサ配置位置の異なる実施例の断面図である。中央には、円柱状導体である１次（Ｒ相）導体１ａを配置し、周囲には、同心であり径の異なる環状導体として、１次（Ｓ相）導体１ｂと１次（Ｔ相）導体１ｃをそれぞれ設けた同軸配線方式である。
また、円柱の１次（Ｒ相）導体１ａ外周と、環状の１次（Ｓ相）導体１ｂの内面との間に磁気センサ２ａを配置し、環状の１次（Ｓ相）導体１ｂの外周と、環状の１次（Ｔ相）導体１ｃの内面との間には磁気センサ２ｂを配置し、さらに環状の１次（Ｔ相）導体１ｃ外周には磁気センサ２ｃを配置している。
【００１５】
磁気センサ２ａ（２０ａ）、２ｂ、２ｃである３つのセンサの配置位置関係は、図１（ｃ）に示すように、中心から円周方向の同軸上にある必要はなく、また一次導体（Ｒ相、Ｓ相、Ｔ相）１ａＡ、１ｂ、１ｃの各導体間に対する配置位置は、磁気センサ２０ａのように、一次導体１ａＡよりも１ｂの近くに（外側に近く）配置しても、あるいは、磁気センサ２０ｂのように、一次導体１ｃよりも１ｂの近く（内側に近く）配置しても良い。
従って、センサの配置位置は、配置すべき範囲内にあれば良く、センサ感度は導体からの距離で決まるため、センサ感度を満足すれば細かな位置関係は限定されるものではない。
【００１６】
また、一次導体（Ｒ相）１ａは、図１（ａ）に示す円柱でも良く、図１（ｃ）に示す円筒（１ａＡ）でも良い。
さらに、一次導体が、中央の円柱導体または円柱導体と、その外側に配置される同心で径の異なる円筒導体とからなる、２重導体で構成される単相の電気配線にも適用でき、これが交流であっても、直流であっても適用可能である。
図１のように、環状または円柱との組み合わせからなる一次導体１ａ、１ｂ、１ｃから成る構成の場合には、各相の一次導体１ａ、１ｂ、１ｃは、同心である必要がある。この同心である場合には、各相から発生する磁束の状態が平衡を保つため、ノイズが発生せず、磁気センサ２ａ、２ｂ、２ｃの測定感度が良い。しかし、同心条件を０．１ｍｍ外れても、ノイズ発生への影響が生ずる。
【００１７】
検出原理について以下に説明する。各一次導体（Ｒ相、Ｓ相、Ｔ相）１ａ、１ｂ、１ｃの半径距離は、図１に示すようにａ〜ｅとし、一次電流をそれぞれＩｒ，Ｉｓ，Ｉｔとすると、各一次導体に１相づつ電流を印加した場合に、任意の半径ｒに発生する磁界の強さは以下の通りとなる。
Ｒ相導体のみに電流を通電した場合。
ｒ≦ａの時、Ｈ＝ｒ＊Ｉｒ／（２＊π＊ａ^２） ……（１）
ｒ＞ａの時、Ｈ＝Ｉｒ／（２＊π＊ｒ） ……（２）
Ｓ相導体のみに電流を通電した場合。
【００１８】
ｒ＜ｂの場合、Ｈ＝０ ……（３）
ｂ≦ｒ≦ｃの場合、Ｈ＝Ｉｓ／（２＊π＊ｒ）＊（ｒ^２−ｂ^２）／（ｃ^２−ｂ^２） ……（４）
ｒ＞ｃの場合、Ｈ＝Ｉｓ／（２＊π＊ｒ） ……（５）
Ｔ相導体のみに電流を通電
ｒ＜ｄの場合、Ｈ＝０ ……（６）
ｄ≦ｒ≦ｅの場合、Ｈ＝Ｉｔ／（２＊π＊ｒ）＊（ｒ^２−ｄ^２）／（ｅ^２−ｄ^２） ……（７）
ｒ＞ｅの場合、Ｈ＝Ｉｔ／（２＊π＊ｒ） ……（８）
一次導体に三相交流を通電した場合の磁界の強さは、各相で発生した磁界強度の合成であるため、Ｔ相導体の外側に配置した磁気センサ２ｃの磁界は、前記（１）式、（５）式、（８）式の加算となるので、
センサ２ｃの磁界の強さＨ＝（Ｉｒ＋Ｉｓ＋Ｉｔ）／（２＊π＊ｒ） ……（９）
地絡電流が流れない場合、３相交流電流の和は零であるので、（９）式つまり、センサ２ｃの磁界は零となる。一方、任意の相に地絡電流Ｉ_Δ _３０が流れた場合を（１０）式に示す。
【００１９】
センサ２ｃの磁界の強さＨ＝（Ｉｒ＋Ｉｓ＋Ｉｔ＋Ｉ_Δ _３０）／（２＊π＊ｒ） ……（１０）
以上より、最外郭導体の外側に磁気センサを配置し、その出力を検出することにより、地絡電流の検出が可能となる。この場合、一次導体１ａ、１ｂ、１ｃに３相交流を通電した際の地絡検出および過電流検出を、３つの磁気センサ２ａ、２ｂ、２ｃで行なっても良いし、最外郭導体の近傍に配置した磁気センサ２ｃで地絡検出を行い、残りの２つの磁気センサ２ａ、２ｂで過電流検出を行うこともできる。
同軸配線方式における中心からの距離と発生磁界の強さの関係を、図１中記載の各一次導体（Ｒ相、Ｓ相、Ｔ相）１ａ、１ｂ、１ｃの半径距離ａ〜ｅを以下のように設定した場合の計算結果として図２に示す。
【００２０】
ａ＝３．５ｍｍ，ｂ＝５．５ｍｍ，ｃ＝６．５ｍｍ，ｄ＝８．５ｍｍ，ｅ＝９ｍｍ
図２は、Ｒ相のみ１２５Ａの電流を通電した場合、Ｔ相のみ、またはＳ相のみマイナス６２．５Ａ通電した場合のそれぞれについて、中心からの距離に対する磁界の強さの変化を示した。これらの計算結果の加算が、実際の３相交流電流として平衡の取れた状態であるため、図２中に３相加算出力として併記した。
地絡電流が無い状態では、３相交流電流を通電すると、最外郭導体の外側では図２中のＡ部に示す通り、磁界は零である。
【００２１】
次に各相電流の検知について説明する。
一次Ｓ相導体１ｂと一次Ｔ相導体１ｃの導体内側に磁界は発生しないので、一次Ｒ相導体１ａと一次Ｓ相導体１ｂの間に配置した磁気センサ２ａの磁界を検出することにより、Ｒ相電流の検出が可能となる。
磁気センサ２ａの磁界の強さ（Ｒ相電流に比例した磁界の強さ）は、上記（２）式の通りであり、一次Ｓ相導体１ｂと一次Ｔ相導体１ｃとの間に配置した磁気センサ２ｂの磁界は、Ｒ相とＳ相との電流の合成となるので、磁気センサ２ｂの出力から磁気センサ２ａの出力を減算することにより、Ｓ相電流を算出できる。
【００２２】
磁気センサ２ｂの磁界の強さ（（２）式＋（５）式）
Ｈ＝（Ｉｒ＋Ｉｓ）／（２＊π＊ｒ） ……（１１）
（１１）式−（２）式（Ｓ相電流に比例した磁界の強さ）
Ｈ＝Ｉｓ／（２＊π＊ｒ） ……（１２）
Ｔ相電流は、Ｒ相電流とＳ相電流の和の逆符号であるので、磁気センサ２ｂの出力に−１をかけることにより、Ｔ相電流を算出できる。
Ｔ相電流に比例した磁界の強さ
Ｈ＝−（Ｉｒ＋Ｉｓ）／（２＊π＊ｒ）＝Ｉｔ／（２＊π＊ｒ） ……（１３）
以上より、３つの磁気センサにより地絡電流および各相電流の検出が可能となる。
【００２３】
第一の実施例に対する零相変流器全体の構成として、図３に同軸配線方式の零相変流器端子構成を示し、（ａ）は斜視図であり、（ｂ）は正面図、（ｃ）は裏面図である。
同軸配線方式の一次導体１ａ、１ｂ、１ｃの両端に配置された各々の端子であるＲ相端子８ａ、８０ａと、Ｓ相端子８ｂ、８０ｂと、Ｔ相端子８ｃ、８０ｃは、各一次導体１ａ、１ｂ、１ｃの一方の端子８ａ、８ｂ、８ｃの接続バー９ａ、９ｂ、９ｃに対して、一次導体１ａ、１ｂ、１ｃと他方の端子８０ａ、８０ｂ、８０ｃとの接続バー９０ａ、９０ｂ、９０ｃを、一次導体の導体中心に対して点対称の位置に設けている。
【００２４】
本構成により、端子接続バー９ａ、９ｂ、９ｃと９０ａ、９０ｂ、９０ｃとは、各相としての経路長がほぼ同一となったことから、従来図７に示す構成で発生していた残留電流を著しく低減することが可能である。
端子構成は、必要により図３に示すように、一方の端子８０ａ、８０ｂ、８０ｃをセットとして、他方の端子８ａ、８ｂ、８ｃに対して高さや位置を変えることもできる。
次に、本発明の第二の実施例について図４により説明する。図４の第二の実施例の構成は、図１の第一実施例の構成に対して、最外郭の一次導体１ｃの外側にシールド用の鉄芯として第一環状鉄芯３を設け、磁気センサ２ｃの位置を第一環状鉄芯３の外側に移動したことが異なっている。また、一次導体（Ｒ相）１ａは、円柱でも円筒でも良く、第一環状鉄芯３を配置した以外は第一の実施例と同じであるので、その他の説明は省略する。
【００２５】
第一実施例の構成において、図１では三つの一次導体１ａ、１ｂ、１ｃが同心の場合は、地絡電流が流れない場合の３相交流電流の和が零になるが、同心でない場合には残留電流と呼ばれる出力が発生し、地絡電流が流れた場合の出力との差を低下させる原因になった。そこで、この対策として第二の実施例の構成では、図４における最外郭に、シールド用の第一環状鉄芯３を設けることで、一次導体１ａ、１ｂ、１ｃが同心でない場合に発生する残留電流の低減が可能となるので、第一環状鉄芯３の外側に磁気センサ２ｃを配置し、その出力を検出することにより、地絡電流を検出することができる。
【００２６】
このように、３つの磁気センサ２ａ、２ｂ、２ｃのうち、第一環状鉄芯３の外側に配置した磁気センサ２ｃで地絡検出を、残りの２つの磁気センサ２ａ、２ｂで過電流検出を行うことができる。
次に、本発明の第三の実施例について図５により説明する。図５の第三の実施例は、図４の第二実施例の構成に対して、最外郭の第一環状鉄芯３の外側に、集磁鉄芯である第二環状鉄芯４を設け、地絡検出用の磁気センサ２ｃを、第二環状鉄芯４の中に配置した構成である。その他の構成は第二の実施例と同じであるので、説明は省略する。
【００２７】
図５のような第三の実施例に基づく第二環状鉄芯４の内部に磁気センサ２ｃを配置する構成では、地絡時の感度向上と、センサ位置誤差の影響を低減することができる。その場合、磁気センサ２ｃの検知磁界は数Ａ／ｍと微小であり、鉄芯飽和の影響が少ない。
零相変流器としての検出は、３つの磁気センサ２ａ、２ｂ、２ｃのうち、第二環状鉄芯４中に配置した磁気センサ２ｃで地絡検出を、残りの２つの磁気センサ２ａ、２ｂで過電流検出を行うことができる。
地絡電流用のセンサ２ｃの検知磁界は数Ａ／ｍと微小であるので、ホール素子や磁気抵抗素子では検出不可能なため、高感度な磁気センサである磁気インピーダンス素子を使用する必要がある。但し、各相電流用のセンサ２ａ，２ｂの検知磁界はホール素子や磁気抵抗素子で検出可能である。
【００２８】
従って、３つの磁気センサ２ａ，２ｂ，２ｃを磁気インピーダンス素子で構成することもできるし、他のセンサ２ａ，２ｂをホール素子または磁気抵抗素子で構成し、センサ２ｃを磁気インピーダンス素子で構成することもできる。
【００２９】
【発明の効果】
この発明の零相変流器では、従来方式のように巻き線を巻回する環状鉄芯を用いないので、磁気飽和を考慮する必要がなく、小型化が可能となる。
また、零相変流器で、地絡検出と過電流検出の両方が可能なことから、漏電遮断器に従来用いられていた過電流検出部を削除することができるので、漏電遮断器の小型化、低コストが容易に達成できる。
一次導体に流れる電流密度を均一にできるので、電流密度の不均一により発生する残留電流の低減が可能となり、地絡検出性能も向上できる。
【００３０】
シールド鉄芯を設けることで、一次導体が同心でない場合に発生する残留電流を低減できるので、一般的な導体位置決め精度でも、安定した地絡検出が可能となり、低コストが容易に行える。
地絡検出用センサを集磁鉄芯中に配置することにより、地絡時の感度向上と、センサ位置誤差の影響を低減することができる。この場合、地絡検出用センサの検知磁界は数Ａ／ｍと微小であり、鉄芯飽和の影響が少ない。低コストな構造で、高精度な地絡検出が可能となる。
３つの磁気センサともに磁気インピーダンス素子を用いることができるので、回路の共通化が図れ、低コスト化が可能となる。
【００３１】
さらに、地絡検出用に磁気インピーダンス素子を用い、各相電流検知用にホール素子を用いることができるので、ホール素子用回路部分の簡略化が図れ、低コスト化が可能となる。
【図面の簡単な説明】
【図１】本発明の第一の実施例を示す基本配置構成図
【図２】本発明の実施例の計算結果説明図
【図３】本発明の実施例に係る零相変流器端子構成図
【図４】本発明の第二実施例の構成図
【図５】本発明の第三実施例の構成図
【図６】従来の電流トランス型零相変流器を示す構成図
【図７】従来の零相変流器端子構成図
【符号の説明】
１：一次導体
２：磁気センサ
３：第一環状鉄心
４：第二環状鉄心
８、８０：端子
９、９０：端子接続バー
１０、１００：端子
１１：零相変流器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a zero-phase current transformer that detects a ground fault current that flows when a ground fault occurs in a transmission and distribution line or there is an electric shock.
[0002]
[Prior art]
FIG. 6 is a configuration diagram showing a conventional current transformer type zero-phase current transformer. In a current transformer type zero-phase current transformer, an output winding 14 is wound around the entire circumference of an annular iron core 13 made of a high magnetic permeability material such as permalloy, and the primary conductors 6a, 6b, and 6c are annular irons. It is arranged so as to penetrate the hollow portion of the core 13.
The principle of detecting the ground fault of the zero-phase current transformer is that the R-phase current Ir and the S-phase current flowing through the R-phase conductor 6a, the S-phase conductor 6b, and the T-phase conductor 6c in a three-phase equilibrium state (a state in which no ground fault occurs). The sum of the current Is and the T-phase current It is always zero, and the magnetic fluxes generated in the annular iron core 13 cancel each other out, so that no voltage is induced in the output winding 14, but if a ground fault occurs, The sum of the currents of the phases is not zero, and a magnetic flux corresponding to the ground fault current is generated in the annular iron core 13 to induce a voltage in the output winding 14.
[0003]
There is a leakage current detection device for a leakage breaker in which a zero-phase current transformer is shielded to prevent malfunction of electronic circuit components due to external noise (for example, see Patent Document 1).
Further, in a three-phase AC circuit, there is disclosed a configuration of an earth leakage breaker having malfunction prevention in a transient large current region where a zero-phase current transformer outputs an unbalanced output (for example, see Patent Document 2). .
Usually, it is necessary to wind the output winding 14 several thousand turns, so that there is a problem in that the size reduction is limited. Then, as an alternative to the conventional current transformer type, there is one in which a highly sensitive magnetic impedance element is arranged in a ring-shaped iron core (for example, see Patent Document 3).
[0004]
FIG. 7 shows a conventional zero-phase current transformer terminal configuration, in which (a) is a perspective view, (b) is a front view, and (c) is a view of only the R-phase terminal viewed from above. The R-phase terminals 10a and 100a, the S-phase terminals 10b and 100b, and the T-phase terminals 10c and 100c are each formed of three cylinders arranged inside the zero-phase current transformer 11 as shown in FIG. Each of the primary conductors 6a, 6b, and 6c was connected to each other, and had a target terminal structure on both sides of the zero-phase zero-phase current transformer 11.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-322249 (pages 5-6, FIG. 1-5)
[Patent Document 2]
JP-A-9-93790 (page 3-4, FIG. 1-5)
[Patent Document 3]
JP-A-10-232259 (page 2-3, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, the conventional current transformer type uses the output winding to orbitally integrate the magnetic flux in the annular iron core, so that the output change due to the position of the conductor is small. However, there is a problem that the output changes depending on the position of the conductor is large and the residual current increases due to the susceptibility to the magnetic flux generated by Ampere's law from each conductor.
In addition, the zero-phase current transformer is usually mounted on the earth leakage breaker. The functions required for the earth leakage breaker include overcurrent detection of each phase in addition to ground fault detection. However, in the conventional zero-phase current transformer, since the detection is performed based on the above-described principle, overcurrent cannot be detected. Therefore, a separate mechanical overcurrent detection mechanism using a current transformer or bimetal is required for overcurrent detection.
[0007]
Further, the terminal structure connected to the primary conductors 6a, 6b, 6c has a structure shown in FIG. 7 in which terminals are provided at line-symmetrical positions with respect to the longitudinal centers of the primary conductors 6a, 6b, 6c because of the ease of taking out the terminals. The configuration shown is readily conceivable. However, as shown in FIG. 7 (c), inside the conductor 6a located inside the main body of the zero-phase current transformer 11, the conductor 6a passes through the conductor due to the presence of the high current density portion and the low current density portion. It is clear from the magnetic field analysis that the non-uniformity of the current density occurs significantly. If no ground-fault current occurs at the time of three-phase equilibrium, the output does not appear ideally. Due to the non-uniform density, an output called a residual current is generated, which causes a problem that a difference from an output when a ground fault current flows is reduced.
[0008]
An object of the present invention is to solve the above-mentioned problem and to provide a compact zero-phase current transformer with an overcurrent detection function.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, in a zero-phase current transformer composed of at least two primary conductors and at least two magnetic sensors,
At least two of the primary conductors are conductors having different diameters, and at least one of the primary conductors except for the primary conductor having the smallest diameter is an annular conductor, and all the primary conductors are arranged with the same center position. Then, one magnetic sensor is provided outside each of the primary conductors.
In this case, of the at least two magnetic sensors, a magnetic impedance element is used for the magnetic sensor arranged near the outermost conductor, and a Hall element or a magnetoresistive element is used for the other magnetic sensors.
[0010]
In a zero-phase current transformer composed of at least two primary conductors and at least two magnetic sensors,
At least two of the primary conductors are conductors having different diameters, and at least one of the primary conductors except for the primary conductor having the smallest diameter is an annular conductor, and all the primary conductors are arranged with the same center position. A first annular iron core having a center position substantially the same as the primary conductor is provided outside the primary conductor, and the magnetic sensors are provided one by one while being sandwiched between at least two primary conductors. It is assumed that the magnetic sensor is provided outside the annular iron core.
[0011]
At this time, a magnetic impedance element is used for the magnetic sensor disposed outside the first annular iron core, and a Hall element or a magnetoresistive element is used for the other magnetic sensors.
In a zero-phase current transformer composed of at least two primary conductors and at least two magnetic sensors,
At least two of the primary conductors are conductors having different diameters, and at least one of the primary conductors except for the primary conductor having the smallest diameter is an annular conductor, and all the primary conductors are arranged with the same center position. A first annular iron core having substantially the same center position as the primary conductor is provided outside the primary conductor, and a second annular core having substantially the same center position as the primary conductor outside the first annular iron core is provided. Iron cores are provided, and the magnetic sensors are provided one by one while being sandwiched by at least two primary conductors; a notch is provided in the second annular iron core; and the magnetic sensor is arranged in the notch. I do.
[0012]
At this time, a magnetic impedance element is used for the magnetic sensor disposed in the cutout of the second annular iron core, and a Hall element or a magnetoresistive element is used for the other magnetic sensors.
The primary conductor having the minimum diameter is a cylindrical conductor or an annular conductor.
Further, the primary conductor has terminals at both ends via connection bars, and the positional relationship of the terminals at both ends of the primary conductor is point-symmetric with respect to the primary conductor, and at least two positions relative to each of the primary conductors are provided. The conductor cross section and the path length between the terminals are changed to make the electric resistance between the terminals equal.
[0013]
Also, the height of each terminal located at one or the other with respect to both sides of the primary conductor is the same, and the height of the terminals disposed at both ends via the primary conductor is different.
Further, the connection bar has a different length on both sides of the primary conductor.
Next, a magnetic impedance element is used as the magnetic sensor.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIGS. 1A and 1B are basic arrangement configuration diagrams showing a first embodiment of the present invention. FIG. 1A is a cross-sectional view, FIG. 1B is a side view, and FIG. 1C is a cross-sectional view of an embodiment having different sensor arrangement positions. is there. A primary (R-phase) conductor 1a, which is a columnar conductor, is disposed at the center, and concentric circular conductors having different diameters are arranged around the primary (S-phase) conductor 1b and the primary (T-phase) conductor. This is a coaxial wiring system provided with conductors 1c.
Further, the magnetic sensor 2a is arranged between the outer periphery of the cylindrical primary (R-phase) conductor 1a and the inner surface of the annular primary (S-phase) conductor 1b, and the outer periphery of the annular primary (S-phase) conductor 1b. A magnetic sensor 2b is disposed between the magnetic sensor 2b and the inner surface of the annular primary (T-phase) conductor 1c, and a magnetic sensor 2c is arranged on the outer periphery of the annular primary (T-phase) conductor 1c.
[0015]
As shown in FIG. 1C, the positional relationship between the three sensors, ie, the magnetic sensors 2a (20a), 2b, and 2c, does not need to be coaxial in the circumferential direction from the center, and the primary conductor (R (Phase, S phase, T phase) 1aA, 1b, 1c may be arranged closer to (closer to the outside of) the primary conductor 1aA than the primary conductor 1aA, as in the magnetic sensor 20a. Like the magnetic sensor 20b, it may be arranged closer to (closer to) the inside of the primary conductor 1c than to the primary conductor 1c.
Therefore, it is sufficient that the sensor is disposed within a range in which the sensor is to be disposed, and the sensor sensitivity is determined by the distance from the conductor. Therefore, if the sensor sensitivity is satisfied, the detailed positional relationship is not limited.
[0016]
Further, the primary conductor (R phase) 1a may be a cylinder shown in FIG. 1A or a cylinder (1aA) shown in FIG. 1C.
Furthermore, the primary conductor can also be applied to a single-phase electrical wiring composed of a double conductor consisting of a central cylindrical conductor or a cylindrical conductor and concentric cylindrical conductors having different diameters arranged outside the central conductor. It can be applied to both AC and DC.
As shown in FIG. 1, in the case of a configuration including the primary conductors 1a, 1b, and 1c formed of a combination with a ring or a cylinder, the primary conductors 1a, 1b, and 1c of each phase need to be concentric. In the case of this concentricity, since the state of the magnetic flux generated from each phase is kept in balance, no noise is generated and the measurement sensitivity of the magnetic sensors 2a, 2b, 2c is good. However, deviating from the concentric condition by 0.1 mm has an effect on noise generation.
[0017]
The detection principle will be described below. As shown in FIG. 1, the radius distances of the primary conductors (R phase, S phase, T phase) 1a, 1b, and 1c are a to e, and the primary currents are Ir, Is, and It, respectively. When a current is applied one phase at a time, the intensity of the magnetic field generated at an arbitrary radius r is as follows.
When current is applied only to the R-phase conductor.
When r ≦ a, H = r * Ir / (2 * π * a ² ) (1)
When r> a, H = Ir / (2 * π * r) (2)
When current is applied only to the S-phase conductor.
[0018]
In the case of r <b, H = 0 (3)
When b ≦ r ≦ c, H = Is / (2 * π * r) * (r ² −b ² ) / (c ² −b ² ) (4)
When r> c, H = Is / (2 * π * r) (5)
When a current is applied only to the T-phase conductor and r <d, H = 0 (6)
In the case of d ≦ r ≦ e, H = It / (2 * π * r) * (r ² −d ² ) / (e ² −d ² ) (7)
When r> e, H = It / (2 * π * r) (8)
Since the strength of the magnetic field when a three-phase alternating current is applied to the primary conductor is a composite of the strength of the magnetic field generated in each phase, the magnetic field of the magnetic sensor 2c disposed outside the T-phase conductor is expressed by the above equation (1). , (5), and (8).
Magnetic field strength of sensor 2c H = (Ir + Is + It) / (2 * π * r) (9)
When the ground fault current does not flow, the sum of the three-phase AC currents is zero, and therefore the expression (9), that is, the magnetic field of the sensor 2c is zero. On the other hand, shows the case where the ground fault current I _delta ₃₀ flows in any phase to (10).
[0019]
The strength of the magnetic field of the sensor 2c H = (Ir + Is + It + I Δ 30) / (2 * π * r) ...... (10)
As described above, by arranging the magnetic sensor outside the outermost conductor and detecting its output, the ground fault current can be detected. In this case, the ground fault detection and the overcurrent detection when the three-phase alternating current is applied to the primary conductors 1a, 1b, and 1c may be performed by the three magnetic sensors 2a, 2b, and 2c, or in the vicinity of the outermost conductor. Ground fault detection may be performed by the disposed magnetic sensor 2c, and overcurrent detection may be performed by the remaining two magnetic sensors 2a and 2b.
The relationship between the distance from the center and the strength of the generated magnetic field in the coaxial wiring method is shown in FIG. 1 by using the radial distances a to e of the primary conductors (R, S, and T phases) 1a, 1b, and 1c as follows. FIG. 2 shows the calculation results when the settings are made as described above.
[0020]
a = 3.5 mm, b = 5.5 mm, c = 6.5 mm, d = 8.5 mm, e = 9 mm
FIG. 2 shows a change in the magnetic field strength with respect to the distance from the center when a current of 125 A is applied only to the R phase, when only the T phase is applied, or when only the S phase is applied to minus 62.5 A. Since the addition of these calculation results is in a balanced state as an actual three-phase alternating current, it is also shown as a three-phase addition output in FIG.
In the state where there is no ground fault current, when a three-phase AC current is applied, the magnetic field is zero outside the outermost conductor as shown in the portion A in FIG.
[0021]
Next, detection of each phase current will be described.
Since no magnetic field is generated inside the conductors of the primary S-phase conductor 1b and the primary T-phase conductor 1c, the R-phase is detected by detecting the magnetic field of the magnetic sensor 2a disposed between the primary R-phase conductor 1a and the primary S-phase conductor 1b. The current can be detected.
The strength of the magnetic field of the magnetic sensor 2a (the strength of the magnetic field in proportion to the R-phase current) is as shown in the above equation (2), and the magnetic field disposed between the primary S-phase conductor 1b and the primary T-phase conductor 1c. Since the magnetic field of the sensor 2b is a combination of the currents of the R and S phases, the S-phase current can be calculated by subtracting the output of the magnetic sensor 2a from the output of the magnetic sensor 2b.
[0022]
Magnetic field strength of magnetic sensor 2b (Formula (2) + Formula (5))
H = (Ir + Is) / (2 * π * r) (11)
Equation (11)-Equation (2) (magnetic field strength proportional to S-phase current)
H = Is / (2 * π * r) (12)
Since the T-phase current has the opposite sign of the sum of the R-phase current and the S-phase current, the T-phase current can be calculated by multiplying the output of the magnetic sensor 2b by -1.
Magnetic field strength H = − (Ir + Is) / (2 * π * r) = It / (2 * π * r) proportional to T-phase current (13)
As described above, the ground fault current and each phase current can be detected by the three magnetic sensors.
[0023]
As a configuration of the entire zero-phase current transformer for the first embodiment, FIG. 3 shows a terminal configuration of a zero-phase current transformer of a coaxial wiring system, (a) is a perspective view, (b) is a front view, and (b) is a front view. (c) is a back view.
The R-phase terminals 8a and 80a, the S-phase terminals 8b and 80b, and the T-phase terminals 8c and 80c, which are terminals disposed at both ends of the primary conductors 1a, 1b, and 1c of the coaxial wiring system, are each a primary conductor 1a. Connection bars 90a, 90b, 90c between the primary conductors 1a, 1b, 1c and the other terminals 80a, 80b, 80c with respect to the connection bars 9a, 9b, 9c of one of the terminals 8a, 8b, 8c of the first terminals 1b, 1c. Are provided at point-symmetric positions with respect to the conductor center of the primary conductor.
[0024]
With this configuration, the terminal connection bars 9a, 9b, 9c and 90a, 90b, 90c have substantially the same path length for each phase, so that the residual current generated in the configuration shown in FIG. Significant reduction is possible.
As shown in FIG. 3, if necessary, one terminal 80a, 80b, 80c can be set as a set, and the height and position of the other terminal 8a, 8b, 8c can be changed.
Next, a second embodiment of the present invention will be described with reference to FIG. The configuration of the second embodiment of FIG. 4 is different from the configuration of the first embodiment of FIG. 1 in that a first annular iron core 3 is provided as an iron core for shielding outside the outermost primary conductor 1c. The difference is that the position of the sensor 2c has been moved to the outside of the first annular iron core 3. Further, the primary conductor (R phase) 1a may be a cylinder or a cylinder, and is the same as the first embodiment except that the first annular iron core 3 is arranged.
[0025]
In the configuration of the first embodiment, in FIG. 1, when the three primary conductors 1a, 1b, and 1c are concentric, the sum of the three-phase AC currents when no ground fault current flows becomes zero, but when the three primary conductors are not concentric, Causes an output called a residual current, which reduces the difference from the output when a ground fault current flows. Therefore, as a countermeasure against this, in the configuration of the second embodiment, the first annular iron core 3 for shielding is provided at the outermost part in FIG. 4 so that the residual that occurs when the primary conductors 1a, 1b, and 1c are not concentric. Since the current can be reduced, the ground sensor current can be detected by arranging the magnetic sensor 2c outside the first annular iron core 3 and detecting its output.
[0026]
As described above, of the three magnetic sensors 2a, 2b, 2c, the ground sensor is detected by the magnetic sensor 2c disposed outside the first annular iron core 3, and the overcurrent detection is performed by the remaining two magnetic sensors 2a, 2b. It can be carried out.
Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment shown in FIG. 5 is different from the second embodiment shown in FIG. 4 in that a second annular iron core 4 as a magnetic flux collecting core is provided outside the outermost first annular iron core 3. The magnetic sensor 2c for detecting a ground fault is arranged in the second annular iron core 4. The other configuration is the same as that of the second embodiment, and the description is omitted.
[0027]
In the configuration in which the magnetic sensor 2c is disposed inside the second annular iron core 4 based on the third embodiment as shown in FIG. 5, the sensitivity at the time of ground fault can be improved and the influence of the sensor position error can be reduced. In this case, the detection magnetic field of the magnetic sensor 2c is as small as several A / m, and the influence of iron core saturation is small.
The detection as a zero-phase current transformer detects the ground fault with the magnetic sensor 2c arranged in the second annular iron core 4 among the three magnetic sensors 2a, 2b, 2c, and the other two magnetic sensors 2a, 2b To perform overcurrent detection.
Since the detection magnetic field of the ground fault current sensor 2c is as small as several A / m and cannot be detected by a Hall element or a magnetoresistive element, it is necessary to use a magnetic impedance element which is a highly sensitive magnetic sensor. . However, the magnetic field detected by the sensors 2a and 2b for each phase current can be detected by a Hall element or a magnetoresistive element.
[0028]
Therefore, the three magnetic sensors 2a, 2b, 2c can be constituted by magnetic impedance elements, the other sensors 2a, 2b can be constituted by Hall elements or magnetoresistive elements, and the sensor 2c can be constituted by magnetic impedance elements. You can also.
[0029]
【The invention's effect】
The zero-phase current transformer of the present invention does not use a ring-shaped iron core for winding a winding as in the conventional method, so that it is not necessary to consider magnetic saturation and the size can be reduced.
In addition, since the zero-phase current transformer can perform both ground fault detection and overcurrent detection, the overcurrent detection unit conventionally used for an earth leakage breaker can be eliminated. And cost reduction can be easily achieved.
Since the current density flowing through the primary conductor can be made uniform, the residual current generated due to the uneven current density can be reduced, and the ground fault detection performance can be improved.
[0030]
By providing the shield iron core, the residual current generated when the primary conductor is not concentric can be reduced, so that stable ground fault detection is possible even with general conductor positioning accuracy, and low cost can be easily achieved.
By arranging the ground fault detection sensor in the magnetism collecting iron core, it is possible to improve the sensitivity at the time of ground fault and reduce the influence of the sensor position error. In this case, the detection magnetic field of the ground fault detection sensor is as small as several A / m, and the influence of iron core saturation is small. With a low cost structure, highly accurate ground fault detection becomes possible.
Since a magnetic impedance element can be used for each of the three magnetic sensors, the circuit can be shared, and the cost can be reduced.
[0031]
Further, since a magnetic impedance element is used for detecting a ground fault, and a Hall element can be used for detecting each phase current, the circuit for the Hall element can be simplified and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a basic arrangement diagram showing a first embodiment of the present invention. FIG. 2 is a diagram illustrating calculation results of an embodiment of the present invention. FIG. 3 is a terminal configuration of a zero-phase current transformer according to an embodiment of the present invention. FIG. 4 is a block diagram of a second embodiment of the present invention. FIG. 5 is a block diagram of a third embodiment of the present invention. FIG. 6 is a block diagram showing a conventional current transformer type zero-phase current transformer. ] Conventional zero-phase current transformer terminal configuration diagram [Description of symbols]
1: Primary conductor 2: Magnetic sensor 3: First annular core 4: Second annular core 8, 80: Terminal 9, 90: Terminal connecting bar 10, 100: Terminal 11: Zero-phase current transformer

Claims

In a zero-phase current transformer composed of at least two primary conductors and at least two magnetic sensors,
At least two of the primary conductors are conductors having different diameters, and at least one of the primary conductors except for the primary conductor having the smallest diameter is an annular conductor, and all the primary conductors are arranged with the same center position. A zero-phase current transformer, wherein one magnetic sensor is provided outside each of the primary conductors.

In a zero-phase current transformer composed of at least two primary conductors and at least two magnetic sensors,
At least two of the primary conductors are conductors having different diameters, and at least one of the primary conductors except for the primary conductor having the smallest diameter is an annular conductor, and all the primary conductors are arranged with the same center position. A first annular iron core having a center position substantially the same as the primary conductor is provided outside the primary conductor, and the magnetic sensors are provided one by one while being sandwiched between at least two primary conductors. A zero-phase current transformer, wherein the magnetic sensor is provided outside a ring-shaped iron core.

In a zero-phase current transformer composed of at least two primary conductors and at least two magnetic sensors,
At least two of the primary conductors are conductors having different diameters, and at least one of the primary conductors except for the primary conductor having the smallest diameter is an annular conductor, and all the primary conductors are arranged with the same center position. A first annular iron core having substantially the same center position as the primary conductor is provided outside the primary conductor, and a second annular core having substantially the same center position as the primary conductor outside the first annular iron core is provided. Iron cores are respectively provided, the magnetic sensors are provided one by one while being sandwiched by at least two primary conductors, a notch is provided in the second annular iron core, and the magnetic sensor is arranged in the notch. Characterized zero-phase current transformer.

The zero-phase current transformer according to any one of claims 1 to 4, wherein the primary conductor having a minimum diameter is a cylindrical conductor or an annular conductor.

The primary conductor has terminals at both ends via connection bars, and the positional relationship of the terminals at both ends of the primary conductor is point-symmetric with respect to the primary conductor, and at least two of each of the primary conductors The zero-phase current transformer according to any one of claims 1 to 4, wherein a conductor cross section and a path length between the terminals are changed to make the electric resistance between the terminals equal.

The height of each terminal located at one or the other with respect to both sides of the primary conductor is the same, and the height of the terminals arranged at both ends via the primary conductor is different. The described zero-phase current transformer.

The zero-phase current transformer according to claim 5, wherein the connection bar has a different length on both sides of the primary conductor.

The current transformer according to any one of claims 1 to 7, wherein a magnetic impedance element is used as the magnetic sensor.

2. The magnetic sensor according to claim 1, wherein a magnetic impedance element is used for the magnetic sensor arranged near the outermost conductor of the at least two magnetic sensors, and a Hall element or a magnetoresistive element is used for the other magnetic sensors. 2. The zero-phase current transformer according to claim 1.

The zero phase change according to claim 2, wherein a magnetic impedance element is used for the magnetic sensor disposed outside the first annular iron core, and a Hall element or a magnetoresistive element is used for another magnetic sensor. Sink.

The zero phase according to claim 3, wherein a magnetic impedance element is used for the magnetic sensor disposed in the cutout portion of the second annular iron core, and a Hall element or a magnetoresistive element is used for another magnetic sensor. Current transformer.