JP4367601B2 - Current measuring system, measuring apparatus and measuring method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、鉄道のレールなど場所によらない断面形状を有する導電体に流れる電流の計測に関するものである。
【０００２】
【従来の技術】
従来、導電体に流れる電流を非接触式で計測する電流計としてクランプ型電流計がある。クランプ型電流計は、導電体の周囲をリングで包囲するものである。しかし、導電体の周囲を包囲できないもの、例えば、鉄道のレールのように車輪がレール上を走るものは、このクランプ型電流計を使用することができない。
【０００３】
近年、電車線路から発生する磁場を調べることが求められている。電車線路から発生する磁場の大きさは、線路の電線やレールを流れる電流の大きさによって変化する。線路の電線には、き電線、吊架線やトロリ線がある。そのため、線路の上方に張られた、例えば図４のように、き電線にクランプ型電流計を設置して電流値を計測する方法がある。しかし、き電線に高圧の電圧がかけられているため地絡事故の発生、き電線に計測機材を設置するため高所作業による墜落事故の発生、また、終電後の深夜作業などの問題点がある。
【０００４】
線路の電線やレールに流れる電流は、直流電車の場合を例に取ると、直流変電所からき電線、吊架線やトロリ線、車輌を介してレールに流れ、直流変電所に戻る経路を通る。そのため、き電線の電流値を計測する代わりに、レールの電流値を計測しても良い。そこで、電車線路から発生する磁場を調べるために、レールに流れる電流を計る方法がある。その方法として、例えば図４のように、インピーダンスボンドにクランプ型電流計を取り付けることができる。インピーダンスボンドでは、レールに引き出しケーブルを接続し、レールに流れる全電流が流れるようにしてある。しかし、インピーダンスボンドの設置場所は限られており、レールを流れる電流値が計る場所によって異なるにも係わらず、電車線路の任意の場所に流れる電流値を計測することができないといった問題点がある。
【０００５】
また、通常のレールボンドにクランプ型電流計を取り付ける方法がある。通常のレールボンドは、数１０ｃｍ程度の長さの導線でレールに接続してある。しかし、通常のレールボンドには、レールに流れる全ての電流が流れるわけではないため、正確なレール電流を計測することができない。レールボンドに流れる電流は、レールの湿潤状態や、温度、接続方法などによって大きく変わるため、この電流値を計測しても、レールに流れる全電流を推定することは困難である。
【０００６】
上記クランプ型電流計は、「周回する磁力線に沿って積分した磁場は、磁力線の輪の中にある電流に比例する」という電流と磁界の関係を示すアンペールの周回積分の法則を利用したものである。この法則は、電流を測定する導線の周囲を囲えれば、導線がどの位置にあっても測定でき、汎用性が高い。しかし、レールのように周囲を囲えない導線の電流計測には応用ができない。それに対して、電流と磁場の関係を示す他の法則として、「ある線分電流が、任意の位置に発生させる磁界の大きさを定める」というビオ・サバールの法則があるが、電流線と磁力計との位置関係が固定されている場合でないと適用できず、汎用性が低いために、電車線路には応用されていなかった。
【０００７】
【発明が解決しようとする課題】
＜イ＞本発明は、導電体に流れる電流を非接触式で容易に計測できるようにすることにある。
＜ロ＞また、本発明は、鉄道のレールなどの断面形状が一定の導電体に流れる電流を容易に計測できるようにすることにある。
【０００８】
【課題を解決するための手段】
本願発明は、 レールである導電体に流れる電流を計測する電流計測システムにおいて、導電体の周囲を包囲することなく導電体の近傍に配置される磁力計と、導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出する処理装置と、前記の磁力計と処理装置をレールに固定する非磁性、非導電性の固定治具とを備えていることを特徴とする電流計測システム、または、レールである導電体に流れる電流を計測する電流計測装置において、導電体の周囲を包囲することなく導電体の近傍に配置される磁力計と、導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出する処理装置と、 前記の磁力計と処理装置をレールに固定する非磁性、非導電性の固定治具とを備えていることを特徴とする電流計測装置、または、レールである導電体に流れる電流を計測する電流計測方法において、導電体の周囲を包囲することなく導電体の近傍に磁力計と処理装置をレールに非磁性、非導電性の固定治具で固定し、導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて、前記の処理装置で電流を算出することを特徴とする電流計測方法である。
【０００９】
本発明にかかる電流計測システムは、
導電体の周囲を包囲することなく導電体の近傍に配置される磁力計と、
導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、
電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、
磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出する処理装置と
を備えているものである。
また、本発明にかかる他の電流計測システムは、
導電体が、断面形状がほぼ一定の導電体であるものである。
更に、本発明にかかる他の電流計測システムは、
導電体が、レールである。
更に、本発明にかかる他の電流計測システムは、
導電体近傍の２点で同時に磁場を測定し、その２点で同じとなった磁場の大きさを、前記定常的な磁場の強さとするものである。
本発明にかかる電流計測装置は、
導電体の周囲を包囲することなく導電体の近傍に配置される磁力計と、
導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、
電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、
磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出する処理装置と
を備えている。
また、本発明にかかる他の電流計測装置は、
導電体近傍の２点で同時に磁場を測定し、その２点で同じとなった磁場の大きさを、前記定常的な磁場の強さとするものである。
本発明にかかる電流計測方法は、
導電体の周囲を包囲することなく導電体の近傍に磁力計を配置し、
導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、
電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、
磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出するものである。
また、本発明にかかる他の電流計測方法は、
導電体が、レールである。
更に、本発明にかかる他の電流計測方法は、
導電体近傍の２点で同時に磁場を測定し、その２点で同じとなった磁場の大きさを、前記定常的な磁場の強さとするものである。
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
【００１０】
＜イ＞電流計測システム
電流計測システムは、導電体に流れる電流を非接触で計測できるものであり、例えば図１のように、鉄道のレールなどの導電体の近傍に磁力計を配置し、磁力計と磁力計で計測した計測値を処理装置で演算処理して導電体に流れる電流を算出するものである。磁力計は、測定精度を高めるために磁界方向とほぼ平行に配置すると良い。磁力計は、種類によって測定値が飽和するフルスケールレンジが異なるため、測定される磁界の大きさがフルスケールレンジを越えないように使用する。磁力計は、磁場の強さを計測できるものであればよく、例えば、磁力計ＭＭ１２３（株式会社ＭＴＩ製）を使用できる。
【００１１】
鉄道には、直流と交流の方式があり、レールに流れる電流は、どちらでも測定できるが、本実施例では、一例としてレールに流れる直流電流の測定について記載する。本発明は、直流電流の測定に限定するものではない。
【００１２】
＜ロ＞磁力計のある場所に発生する磁場の強さ
電流と磁場の強さの関係式は、ビオ・サバールの法則（式１を参照）に従って求めることができる。導電体の断面を多数に区画し、各区画に微小電流ｉが流れた場合、磁力計のある場所に発生する磁場の強さｄＨをビオ・サバールの法則に従って求める。即ち、断面全体に流れる電流は、各区画に流れる電流ｉの総和Ｉとなり、磁力計のある場所ｒに発生する磁場の強さは、各区画によって生じる磁場の強さｄＨの総和Ｈとなる。
【００１３】
【式１】
＜ハ＞磁気の計測値から電流を求める
磁力計によって測定した磁場の強さから、電流を求める。
電流を求める式は、電流Ｉ＝ｋＨとなり、ここで係数ｋは、断面積や磁力計のある場所ｒに依存する定数である。このＨは、電流Ｉによって発生する磁場であり、実際計測された磁場の強さＨmは、導電体に流れる電流以外で発生する磁場が含まれている。導電体に流れる電流以外で発生する磁場としては、地磁気などの定常的な磁界や付近の導電体に流れる電流による変動磁界がある。ただし、鉄道のレールに流れる電流を測定する例の場合には、付近の導電体である隣接のレール、き電線、吊架線、トロリ線などによって発生する変動磁界は、測定するレールの電流によって発生する磁界に比例しており、これに比べると、通常は弱く殆ど無視することができる。そこで、こうした場合には、地磁気などの定常的な磁場の強さＨ0を求めて、計測した磁場の強さＨmから引いておく必要がある。その結果、電流と磁場の強さの関係式は、電流Ｉ＝ｋ（Ｈm−Ｈ0）となる。ここで、磁場の強さＨ0の計測方法は、導電体に電流を流さない状態のときの磁力計の計測値を利用する方法や、後説する２点で同時測定する方法などがある。
【００１５】
＜ハ＞磁界の強さＨ0の測定で２点で同時測定する方法
磁場の強さＨ0は、レールに電流が流れていない時に求める方法の他に、磁力計を測定点ＡとＢの２箇所に設置して求めることができる。測定点ＡとＢの２箇所の測定磁場ＨmA、ＨmBと電流値Ｉの関係は、以下の式となる。
【００１６】
【式２】
【式３】
２箇所で同時に測定し、Ｈ0A＝Ｈ0Bとなる個所がある場合、この式と上記式２と式３からＨ0＝Ｈ0A＝Ｈ0Bを求めることができる。即ち、Ｈ0A＝Ｈ0Bとなる２点に磁力計を設置して測定すれば、Ｈ0を求めることができる。
【００１９】
＜ニ＞処理装置
処理装置は、磁力計で計測した計測値を電流と磁場の強さの関係式に入れて、導電体に流れる電流値を算出するものであり、専用の演算処理装置やパソコンなどでの処理装置を使用することができる。処理装置は、磁力計と電気的に接続して測定値を入力してもよく、又は、処理装置と磁力計を分離しておき、磁力計の計測値をデータロガー（図示していない）で記憶し、後で、その計測データを処理装置で処理してもよい。処理装置には、測定値の表示部や、アナログ電圧出力端子など、測定値の記録に必要な機器を取り付けることができる。また、パソコンとの接続に必要なケーブル端子や通信機器との接続端子、データ記録装置やデータ通信装置などを取り付けることもできる。
【００２０】
＜ホ＞計測対象導電体
計測対象の導電体は、電気が流れるものならよく、鉄道やモノレールのレールの他にも、アース用金属配管、金属ワイヤ、鉄骨部材、高圧送電線、柱や梁などの筒状構造部材などがある。レールなどの長手方向の導電体において、長手方向に電流が流れ、長手方向に直交する断面形状が一定なものは、長手方向の任意の位置で同一の電流と磁場の強さの関係式で電流を求めることができる。レールのように断面形状が同一で何処でも電流密度が一定となる場合、ビオ・サバールの法則を利用することにより、計測を容易に行うことができる。
【００２１】
＜ヘ＞固定治具
固定治具３は、磁力計１１をレール２１の所定位置に位置合わせできるものであり、また、磁力計１１を必要に応じて適切な位置に固定できる。固定治具３の材質は、測定値に影響を与えないように、非磁性、非導電性のものが好ましい。固定治具３は、例えば図２に示すように、磁力計１１をレール２１に位置合わせできるので、磁力計１１がレール２１の決まった位置に設置され、線路の何処でも容易に電流を計測することができる。固定具の形状は、種々あり、一例を図２（Ａ）〜（Ｃ）に示す。固定治具３には、磁力計１１の他に、処理装置１２や留め具１４を備えている。処理装置には、表示部１３があり、測定値を即座に知ることができる。
【００２２】
以下に、レールに流れる電流値の計測方法を説明する。
【００２３】
＜イ＞磁力計の配置
磁力計の配置場所は、レールの近傍、即ちレールに流れた電流で作られる磁場が計測できる強さであり、測定対象のレール以外から発生する変動磁場の影響を受けないところならよい。経験的にレールの場合は、７０ｃｍ以上離れた位置では測定が困難であることが知られた。電流と磁場の強さの関係式の係数ｋは、磁力計の配置位置（レールの断面を含む平面上の位置）の変化で変わるので、予め決めた位置に配置するとよい。例えば、レールの面対称の位置で、底面の中央から下、数ｃｍ、例えば１ｃｍ〜５ｃｍ程度の個所では、磁場の強さが適当な大きさであり、磁場の方向がレールの底面に平行で、正しい測定値が得られ易い。
【００２４】
＜ロ＞レールに流れる電流の算出
磁力計１１で測定した磁場の強さを処理装置１２に入力し、電流と磁場の強さの関係式の磁場の強さＨmに代入してレール２１に流れる電流値Iを算出し、表示装置に表示する。
【００２５】
＜ハ＞実際の測定値の比較
実際の電車線路において、時刻１５時２０分から１５時３０分の１０分間に電車が通過した際に測定した。ここでは、インピーダンスボンド付近のレール底面下３ｃｍに磁力計を配置し、データロガーで計測値を記録した。同時に従来のインピーダンスボンドの個所でクランプ型電流計を配置し電流値を計測し、データロガーで記録した。それらの電流値を比較したグラフを図３に示す。
【００２６】
本発明で得られた電流値とインピーダンスボンドで測定した電流値は、正負３００アンペアと大幅に変動しても、殆ど一致していた。両者の相関係数は、０．９９であった。このように、非接触式で、レール周囲を覆うこと無く磁場の強さを測定しても、レールに流れる電流値を正確に測定することができた。
【００２７】
【発明の効果】
本発明は、次のような効果を得ることができる。
＜イ＞本発明によって、導電体に流れる電流を非接触の方法で容易に計測することができる。
＜ロ＞また、本発明によって、クランプ型電流計が設置できない大きさや形状、その他の状況の導電体でも電流値を容易に計測することができる。
＜ハ＞また、本発明によって、電車の走行に支障なく、レールの直流電流値を容易に計測することができる。
＜ニ＞また、本発明によって、電車線路を流れる電流を任意の個所で任意の時刻に容易に計測できるので、電車線路から発生する磁場が調査すべき周辺に及ぼす影響を検討することができる。
＜ホ＞また、本発明によって、電車線路を流れる最大電流を任意の個所で容易に計測できるので、き電線、吊架線、トロリ線の材質、断面積、条数を決めることができ、それに基づいて、架線の保持材の強度や、電車線路を保持する橋脚などの強度を求めることができる。その結果、電車線路の設計時に、必要最小限の構造部材を検討できるようになり、不要コストの削減、環境対策に寄与することができる。
＜ヘ＞また、本発明によって、き電線、吊架線、トロリ線を流れる電流の総和は、同じ場所でのレール電流値とレールからの漏洩電流値の総和に等しいので、レールからの漏洩電流を計測することができる。
＜ト＞また、本発明によって、水道管、ガス管などの金属配管に流れる迷走電流を計測でき、電食の危険性を知ることができる。
【図面の簡単な説明】
【図１】導電体に流れる電流を計測する電流計測システムの説明図
【図２】レール電流計測システムの説明図
【図３】本発明で計測した電流値を示すグラフの図
【図４】従来の電車線路に流れる電流計測の説明図
【符号の説明】
１・・・電流計測システム
１１・・磁力計
１２・・処理装置
１３・・表示部
２・・・導電体
２１・・レール
３・・・固定治具[0001]
BACKGROUND OF THE INVENTION
The present invention relates to measurement of current flowing in a conductor having a cross-sectional shape that does not depend on a location such as a railroad rail.
[0002]
[Prior art]
Conventionally, there is a clamp-type ammeter as an ammeter that measures a current flowing through a conductor in a non-contact manner. A clamp-type ammeter surrounds a conductor with a ring. However, the clamp-type ammeter cannot be used if the conductor cannot be surrounded, for example, a wheel running on the rail such as a railroad rail.
[0003]
In recent years, it has been required to examine the magnetic field generated from a train track. The magnitude of the magnetic field generated from the train line changes depending on the magnitude of the current flowing through the electric wire and rail of the line. There are feeders, suspension lines and trolley wires in the electric wires of the track. Therefore, there is a method of measuring a current value by installing a clamp-type ammeter on a feeder, for example, as shown in FIG. However, there are problems such as a ground fault due to the high voltage applied to the feeder, a crash due to work at a high place due to the installation of measuring equipment on the feeder, and midnight work after the last train. is there.
[0004]
For example, in the case of a DC train, the current flowing in the electric wires and rails of the track flows from the DC substation to the rail via the electric wires, suspension lines, trolley wires, and vehicles, and then returns to the DC substation. Therefore, instead of measuring the current value of the feeder, the current value of the rail may be measured. Therefore, in order to investigate the magnetic field generated from the train track, there is a method of measuring the current flowing through the rail. As the method, for example, as shown in FIG. 4, a clamp-type ammeter can be attached to the impedance bond. In the impedance bond, a lead-out cable is connected to the rail so that all current flowing through the rail flows. However, the location where the impedance bond is installed is limited, and there is a problem that it is impossible to measure the value of the current flowing through an arbitrary place on the train line, even though the value of the current flowing through the rail varies depending on the place where the current is measured.
[0005]
There is also a method of attaching a clamp type ammeter to a normal rail bond. A normal rail bond is connected to the rail with a conducting wire having a length of about several tens of centimeters. However, since not all current flowing through the rail flows through a normal rail bond, accurate rail current cannot be measured. Since the current flowing through the rail bond varies greatly depending on the rail wet state, temperature, connection method, and the like, it is difficult to estimate the total current flowing through the rail even if this current value is measured.
[0006]
The clamp-type ammeter uses Ampere's orbital integration law, which indicates the relationship between current and magnetic field, saying that the magnetic field integrated along the magnetic field lines is proportional to the current in the ring of magnetic field lines. is there. This law is highly versatile because it can be measured at any position as long as it surrounds the conductor for measuring current. However, it cannot be applied to the current measurement of conductors that cannot be surrounded by rails. On the other hand, as another law indicating the relationship between current and magnetic field, there is Bio-Savart's law that "a certain line segment current determines the magnitude of the magnetic field generated at an arbitrary position". It could not be applied unless the positional relationship with the meter is fixed, and because of its low versatility, it was not applied to train tracks.
[0007]
[Problems to be solved by the invention]
<A> An object of the present invention is to make it possible to easily measure a current flowing through a conductor in a non-contact manner.
<B> The present invention also makes it possible to easily measure a current flowing in a conductor having a constant cross-sectional shape such as a railroad rail.
[0008]
[Means for Solving the Problems]
The present invention is a current measurement system for measuring a current flowing through a conductor , which is a rail, and includes a magnetometer disposed in the vicinity of the conductor without surrounding the conductor, and a cross-sectional shape of the conductor. Calculate the sum of the magnetic field strength at the position of the magnetometer generated by the flowing current, obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position, and A processing device that calculates a current by applying a value obtained by subtracting the strength of a stationary magnetic field from the magnitude of the magnetic field measured at the meter position to the relational expression, and fixing the magnetometer and the processing device to the rail. Surrounding the periphery of a conductor in a current measurement system characterized by comprising a non-magnetic, non-conductive fixture or a current measurement device for measuring a current flowing through a conductor as a rail Placed close to the conductor The sum of the magnetic field strength at the position of the magnetometer generated by the magnetometer and the current flowing in each part of the cross-sectional shape of the conductor is calculated, the sum of the current and the strength of the magnetic field at the magnetometer position Is a processing device that calculates a current by obtaining a relational expression including a coefficient with the sum of the two and applying a value obtained by subtracting the stationary magnetic field strength from the magnitude of the magnetic field measured at the magnetometer position to the relational expression. And a current measuring device comprising a nonmagnetic and nonconductive fixing jig for fixing the magnetometer and the processing device to a rail, or a current flowing through a conductor as a rail. In the current measurement method, the magnetometer and the processing device are fixed to the rail with a nonmagnetic and nonconductive fixing jig in the vicinity of the conductor without surrounding the conductor, and each portion of the cross section of the conductor At a position where the magnetometer is generated by the current flowing through Calculate the sum of the magnetic field strength, obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position, and from the magnitude of the magnetic field measured at the magnetometer position, The current measurement method is characterized in that a value obtained by subtracting the strength of a simple magnetic field is applied to the relational expression, and the current is calculated by the processing apparatus .
[0009]
The current measurement system according to the present invention is:
A magnetometer disposed in the vicinity of the conductor without surrounding the conductor;
Calculate the sum of the magnetic field strength at the position of the magnetometer, generated by the current flowing in each part of the cross-sectional shape of the conductor,
Obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position,
And a processing device for calculating a current by applying a value obtained by subtracting the strength of a stationary magnetic field from the magnitude of the magnetic field measured at the magnetometer position to the relational expression.
In addition, another current measurement system according to the present invention is:
The conductor is a conductor having a substantially constant cross-sectional shape.
Furthermore, other current measurement systems according to the present invention include:
The conductor is a rail.
Furthermore, other current measurement systems according to the present invention include:
The magnetic field is measured simultaneously at two points in the vicinity of the conductor, and the magnitude of the magnetic field that is the same at the two points is the strength of the steady magnetic field.
The current measuring device according to the present invention is:
A magnetometer disposed in the vicinity of the conductor without surrounding the conductor;
Calculate the sum of the magnetic field strength at the position of the magnetometer, generated by the current flowing in each part of the cross-sectional shape of the conductor,
Obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position,
And a processing device that calculates a current by applying a value obtained by subtracting the strength of a stationary magnetic field from the magnitude of the magnetic field measured at the magnetometer position to the relational expression.
In addition, another current measuring device according to the present invention is
The magnetic field is measured simultaneously at two points in the vicinity of the conductor, and the magnitude of the magnetic field that is the same at the two points is the strength of the steady magnetic field.
The current measurement method according to the present invention includes:
A magnetometer is placed in the vicinity of the conductor without surrounding the conductor,
Calculate the sum of the magnetic field strength at the position of the magnetometer, generated by the current flowing in each part of the cross-sectional shape of the conductor,
Obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position,
The current is calculated by applying the value obtained by subtracting the strength of the stationary magnetic field from the magnitude of the magnetic field measured at the magnetometer position to the relational expression.
In addition, another current measurement method according to the present invention is:
The conductor is a rail.
Furthermore, other current measurement methods according to the present invention include:
The magnetic field is measured simultaneously at two points in the vicinity of the conductor, and the magnitude of the magnetic field that is the same at the two points is the strength of the steady magnetic field.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0010]
<A> Current measurement system The current measurement system can measure the current flowing through the conductor in a non-contact manner. For example, as shown in FIG. 1, a magnetometer is arranged in the vicinity of a conductor such as a rail of a railway. A measurement value measured by a meter and a magnetometer is processed by a processing device to calculate a current flowing through the conductor. The magnetometer is preferably arranged substantially parallel to the magnetic field direction in order to increase the measurement accuracy. The magnetometer is used so that the magnitude of the magnetic field to be measured does not exceed the full scale range because the full scale range in which the measured value is saturated differs depending on the type. Any magnetometer may be used as long as it can measure the strength of the magnetic field. For example, a magnetometer MM123 (manufactured by MTI Co., Ltd.) can be used.
[0011]
There are direct current and alternating current systems for railways, and the current flowing through the rail can be measured by either method. In this embodiment, the measurement of the direct current flowing through the rail is described as an example. The present invention is not limited to the measurement of direct current.
[0012]
<B> Strength of the magnetic field generated at a place where the magnetometer is located The relational expression between the current and the strength of the magnetic field can be obtained according to Bio-Savart's law (see Formula 1). When a cross section of the conductor is divided into many sections and a minute current i flows through each section, the strength dH of the magnetic field generated at a place where the magnetometer is located is obtained according to Bio-Savart's law. That is, the current flowing through the entire cross section is the sum I of the current i flowing through each section, and the strength of the magnetic field generated at the location r where the magnetometer is located is the sum H of the magnetic field strength dH generated by each section.
[0013]
[Formula 1]
<C> Obtaining the current from the measured value of magnetism The current is obtained from the strength of the magnetic field measured by the magnetometer.
The equation for obtaining the current is the current I = kH, where the coefficient k is a constant depending on the cross-sectional area and the location r where the magnetometer is located. This H is a magnetic field generated by the current I, and the actually measured magnetic field strength H m includes a magnetic field generated other than the current flowing through the conductor. The magnetic field generated other than the current flowing through the conductor includes a stationary magnetic field such as geomagnetism and a variable magnetic field due to the current flowing through a nearby conductor. However, in the example of measuring the current flowing in the rail of the railway, the magnetic field generated by the adjacent rail, feeder, suspension wire, trolley wire, etc., which are nearby conductors, is generated by the current of the rail being measured. In comparison with this, it is usually weak and almost negligible. Therefore, in such a case, it is necessary to obtain a steady magnetic field strength H 0 such as geomagnetism and subtract it from the measured magnetic field strength H m . As a result, the relational expression between the current and the strength of the magnetic field is a current I = k (H m −H 0 ). Here, there are a method of measuring the magnetic field strength H 0 , such as a method of using a measured value of a magnetometer when no current is passed through a conductor, or a method of simultaneously measuring two points described later.
[0015]
Strength H 0 of the method the magnetic field measured simultaneously at two points in the measurement of the strength H 0 of <c> magnetic field, in addition to the method of determining when no current is flowing in the rail, the measurement points A and B the magnetometer It can be obtained by installing in two places. The relationship between the measurement magnetic fields H mA and H mB at two measurement points A and B and the current value I is as follows.
[0016]
[Formula 2]
[Formula 3]
If there are locations where H 0A = H 0B is measured simultaneously at two locations, H 0 = H 0A = H 0B can be obtained from this equation and the
[0019]
<D> Processing device The processing device calculates the current value flowing through the conductor by putting the measured value measured by the magnetometer into the relational expression between the current and the magnetic field strength. And the like can be used. The processing device may be electrically connected to the magnetometer to input the measured value, or the processing device and the magnetometer may be separated and the measured value of the magnetometer may be input with a data logger (not shown). You may memorize | store and process the measurement data with a processing apparatus later. Equipment necessary for recording measurement values, such as a display unit for measurement values and an analog voltage output terminal, can be attached to the processing device. In addition, a cable terminal necessary for connection with a personal computer, a connection terminal with a communication device, a data recording device, a data communication device, and the like can be attached.
[0020]
<E> Conductor to be measured The conductor to be measured is not limited as long as electricity flows through it. In addition to railroad and monorail rails, metal pipes for earthing, metal wires, steel members, high-voltage power transmission lines, columns and beams, etc. There is a cylindrical structural member. In a conductor in the longitudinal direction such as a rail, a current flows in the longitudinal direction and the cross-sectional shape perpendicular to the longitudinal direction is constant, the current is expressed by the relational expression between the same current and the strength of the magnetic field at an arbitrary position in the longitudinal direction. Can be requested. When the cross-sectional shape is the same as in a rail and the current density is constant everywhere, measurement can be easily performed by using Bio-Savart's law.
[0021]
<F> Fixing jig The fixing
[0022]
Below, the measuring method of the electric current value which flows into a rail is demonstrated.
[0023]
<A> Magnetometer location The magnetometer location is the strength that allows measurement of the magnetic field created by the current that flows in the vicinity of the rail, that is, the rail, and is affected by the fluctuation magnetic field generated from other than the rail to be measured. If there is no place, it is good. Empirically, it has been known that measurement is difficult at a position of 70 cm or more in the case of a rail. The coefficient k in the relational expression between the current and the magnetic field strength changes depending on the change of the magnetometer placement position (position on the plane including the rail cross section), so it may be placed at a predetermined position. For example, at a position symmetrical to the surface of the rail and at a position several cm, for example, about 1 cm to 5 cm below the center of the bottom surface, the magnetic field strength is appropriate, and the direction of the magnetic field is parallel to the bottom surface of the rail. It is easy to obtain correct measurement values.
[0024]
<B> Calculation of the current flowing in the rail The magnetic field strength measured by the
[0025]
<C> Comparison of Actual Measurement Values Measurement was performed when the train passed from 15:20 to 10:30 on the actual train track. Here, a magnetometer was placed 3 cm below the rail bottom near the impedance bond, and the measured value was recorded with a data logger. At the same time, a clamp-type ammeter was placed at the location of the conventional impedance bond, and the current value was measured and recorded with a data logger. The graph which compared those electric current values is shown in FIG.
[0026]
The current value obtained by the present invention and the current value measured by the impedance bond almost coincided with each other even if it fluctuated significantly by 300 amperes. The correlation coefficient between them was 0.99. Thus, even if the magnetic field strength was measured without covering the periphery of the rail in a non-contact manner, the current value flowing through the rail could be accurately measured.
[0027]
【The invention's effect】
The present invention can obtain the following effects.
<A> According to the present invention, the current flowing through the conductor can be easily measured by a non-contact method.
<B> Further, according to the present invention, a current value can be easily measured even with a conductor in a size, shape, or other situation where a clamp-type ammeter cannot be installed.
<C> Further, according to the present invention, it is possible to easily measure the direct current value of the rail without any trouble in traveling the train.
<D> Further, according to the present invention, since the current flowing through the train track can be easily measured at any location and at any time, the influence of the magnetic field generated from the train track on the periphery to be investigated can be examined.
<E> Further, according to the present invention, the maximum current flowing through the train track can be easily measured at any location, so that the material, cross-sectional area, and number of strips of feeders, suspension wires, and trolley wires can be determined. Thus, the strength of the overhead wire holding material and the strength of the bridge pier holding the train track can be obtained. As a result, the minimum necessary structural members can be studied at the time of designing the train track, which can contribute to reduction of unnecessary costs and environmental measures.
<F> Further, according to the present invention, the sum of currents flowing through feeders, suspension wires, and trolley wires is equal to the sum of the rail current value at the same place and the leakage current value from the rail. It can be measured.
<G> Further, according to the present invention, stray currents flowing in metal pipes such as water pipes and gas pipes can be measured, and the risk of electrolytic corrosion can be known.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a current measuring system for measuring a current flowing through a conductor. FIG. 2 is an explanatory diagram of a rail current measuring system. FIG. 3 is a graph showing a current value measured by the present invention. Illustration of current flowing in the train line [Explanation of symbols]
DESCRIPTION OF
Claims (3)
導電体の周囲を包囲することなく導電体の近傍に配置される磁力計と、
導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、
電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、
磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出する処理装置と、
前記の磁力計と処理装置をレールに固定する非磁性、非導電性の固定治具とを備えていることを特徴とする、電流計測システム。 In the current measurement system that measures the current flowing through the conductor, which is a rail ,
A magnetometer disposed in the vicinity of the conductor without surrounding the conductor;
Calculate the sum of the magnetic field strength at the position of the magnetometer, generated by the current flowing in each part of the cross-sectional shape of the conductor,
Obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position,
A processing device that calculates a current by applying a value obtained by subtracting the strength of a stationary magnetic field from the magnitude of the magnetic field measured at the magnetometer position to the relational expression,
A current measurement system comprising: the magnetometer and a non-magnetic, non-conductive fixing jig for fixing the processing device to a rail .
導電体の周囲を包囲することなく導電体の近傍に配置される磁力計と、
導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、
電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、
磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて電流を算出する処理装置と、
前記の磁力計と処理装置をレールに固定する非磁性、非導電性の固定治具とを備えていることを特徴とする、
電流計測装置。 In the current measurement device that measures the current flowing through the conductor, which is a rail ,
A magnetometer disposed in the vicinity of the conductor without surrounding the conductor;
Calculate the sum of the magnetic field strength at the position of the magnetometer, generated by the current flowing in each part of the cross-sectional shape of the conductor,
Obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position,
A processing device that calculates a current by applying a value obtained by subtracting the strength of a stationary magnetic field from the magnitude of the magnetic field measured at the magnetometer position to the relational expression,
A non-magnetic, non-conductive fixing jig for fixing the magnetometer and the processing device to a rail is provided.
Current measuring device.
導電体の周囲を包囲することなく導電体の近傍に磁力計と処理装置をレールに非磁性、非導電性の固定治具で固定し、
導電体の断面形状の各部分に流れる電流によって発生する、磁力計のある位置での磁場の強さの総和を算出し、
電流の総和と、磁力計位置の磁場の強さの総和との、係数を含む関係式を得、
磁力計位置で計測した磁場の大きさから、定常的な磁場の強さを差し引いた値を、前記関係式に当てはめて、前記の処理装置で電流を算出することを特徴とする
電流計測方法。 In the current measurement method for measuring the current flowing through the conductor, which is a rail ,
Fix the magnetometer and processing device in the vicinity of the conductor without surrounding the conductor with a nonmagnetic, nonconductive fixing jig on the rail ,
Calculate the sum of the magnetic field strength at the position of the magnetometer, generated by the current flowing in each part of the cross-sectional shape of the conductor,
Obtain the relational expression including the coefficient of the sum of the current and the sum of the magnetic field strength at the magnetometer position,
A current measurement method, wherein a value obtained by subtracting a steady magnetic field strength from the magnitude of a magnetic field measured at a magnetometer position is applied to the relational expression, and the current is calculated by the processing device .
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