JP3790993B2 - Ground resistance measuring instrument and ground resistance measuring method - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、電気設備技術基準で定められているＢ種接地極と、低圧機器の筐体を接地するための機器用接地極との直列合成接地抵抗値を測定する接地抵抗測定器及び接地抵抗測定方法に関する。
【０００２】
【従来の技術】
従来、高低圧変圧器の低圧側端子の一つもしくは中性線を接地するためのＢ種接地極や、高低圧変圧器の低圧側電路に接続される低圧機器の筐体等を接地するためのＤ種接地極やＣ種接地極の接地抵抗値を接地抵抗計２０で測定する場合、図２に示すような電位降下法に基づいて行なわれる。この電位降下法とは、大地に埋設された測定対象接地極２１と電流補助極２２の間に交流電源２３から出力された交流電圧を計測用標準電圧として印加することにより、測定対象接地極２１と電流補助極２２の間に流れる電流Ｉを電流計２４で測定すると同時に、測定対象接地極２１と電流補助極２２の間の設置した電位補助極２５と測定対象接地極２１の間の電圧Ｖを電圧計２６で測定したうえ、電圧Ｖ／電流Ｉの計算をすることによって測定対象接地極２１の接地抵抗値を求める方法である。（例えば、非特許文献１参照。）
【０００３】
【非特許文献１】
高橋健彦著「接地技術入門」株式会社オーム社出版、昭和６３年２月１０日 ｐ１５０−１５３
【０００４】
【発明が解決しようとする課題】
上記従来の接地抵抗計２０で測定対象接地極２１、例えばＢ種接地極の接地抵抗値を測定する場合、高低圧変圧器等の電気設備の竣工時、あるいは年次点検時に需要家構内を停電にし、測定対象接地極２１を高低圧変圧器から電気的に切り離して測定しなければならない。そのため、測定対象接地極２１の接地抵抗値を随時、測定することは現実的に困難である。また、計測用標準電圧を出力するための交流電源２３を必要とする。
尚、一般に接地極の接地抵抗値は、気温や大地の水分量により季節的に変動するため、年間を通して一定値にはならないことが知られている。このため、高低圧変圧器の竣工時、あるいは年次点検時にのみ、接地極の接地抵抗値を測定するだけでは、接地極の接地抵抗値が電気設備技術基準で定められている許容値以下に常に保たれていることを保証することができない。
【０００５】
そこで本発明では、計測用標準電圧が不要で、且つ、１次側が特別高圧もしくは高圧の高低圧変圧器が稼動中であっても、Ｂ種接地極と低圧機器を接地するための機器用接地極との直列合成接地抵抗値を測定することができる接地抵抗測定器及び接地抵抗測定方法を提供するとともに、測定した直列合成接地抵抗値に基づいて計算した季節変動率を、高低圧変圧器の竣工時に予め測定されているＢ種接地極及び機器用接地極それぞれの接地抵抗値に乗じることによって、それぞれの接地極の接地抵抗値が電気設備技術基準で定められている許容値以下に保たれているか否かを判断することができる接地抵抗測定方法を提供することを解決すべき課題とするものである。
【０００６】
【課題を解決するための手段】
上記課題は、特許請求の範囲の欄に記載した接地抵抗測定器及び接地抵抗測定方法により解決することができる。
【０００７】
請求項１記載の接地抵抗測定器によれば、高低圧変圧器の低圧側電路から低圧機器の筐体に漏洩電流が流れた場合、電流検出手段により、低圧機器の筐体から機器用接地極、大地、及びＢ種接地極を介して低圧側電路に戻る第１の通電路を流れる漏洩電流と、低圧機器の筐体から可変電気抵抗を介して当該高低圧変圧器の低圧側電路に戻るように接続された第２の通電路を流れる漏洩電流とが反対の通電方向で同時に検出されると、調整手段は、電流検出手段から出力される電流検出信号がゼロになるように可変電気抵抗の抵抗値を自動的に調整するため、出力手段は、その抵抗値を出力する。このように、電流検出手段の電流検出値がゼロになるように可変電気抵抗の抵抗値が自動的に調整された場合に出力手段から出力された可変電気抵抗の抵抗値を、Ｂ種接地極と機器用接地極の直列合成接地抵抗値として測定する。
これにより、計測用標準電圧が不要で、且つ高低圧変圧器が稼動中であっても、Ｂ種接地極と低圧機器を接地するための機器用接地極の直列合成接地抵抗を測定することができる。
【０００８】
請求項２記載の接地抵抗測定方法によれば、高低圧変圧器の低圧側電路から低圧機器の筐体に漏洩電流が流れた場合、低圧機器の筐体から機器用接地極、大地、及びＢ種接地極を介して低圧側電路に戻る第１の通電路を流れる漏洩電流と、低圧機器の筐体から可変電気抵抗を介して当該高低圧変圧器の低圧側電路に戻るように接続された第２の通電路を流れる漏洩電流とが検出されると、第１、第２の二つの通電路を流れる漏洩電流が等しくなるように第２の通電路の可変電気抵抗の抵抗値が調整されるため、当該可変電気抵抗の抵抗値に基づいてＢ種接地極と機器用接地極の直列合成接地抵抗値を測定することができる。
これにより、計測用標準電圧が不要で、且つ高低圧変圧器が稼動中であっても、Ｂ種接地極と低圧機器を接地するための機器用接地極の直列合成接地抵抗を測定することができる。
【０００９】
請求項３記載の接地抵抗測定方法によれば、高低圧変圧器の低圧側電路から低圧機器の筐体に漏洩電流が流れた場合、低圧機器の筐体から前記機器用接地極、大地、及び前記Ｂ種接地極を介して低圧側電路に戻る第１の通電路を流れる漏洩電流と、Ｂ種接地極と前記機器用接地極の想定される直列合成接地抵抗値より大きい抵抗値の固定電気抵抗を有する第２の通電路を流れる漏洩電流とを、それぞれの漏洩電流の通電方向が反対になるように変流器により検出した状態で、第２の通電路の変流器への巻数を、第１、第２の二つの通電路を流れる漏洩電流の変流器による検出電流がゼロになるように調整する。この状態での第２の通電路の変流器への巻数と当該固定電気抵抗の抵抗値に基づいてＢ種接地極と機器用接地極の直列合成接地抵抗値を求めることができる。
これにより、計測用標準電圧が不要で、且つ高低圧変圧器が稼動中であっても、Ｂ種接地極と低圧機器を接地するための機器用接地極の直列合成接地抵抗を求めることができる。
【００１０】
請求項４記載の接地抵抗測定方法によれば、Ｂ種接地極と機器用接地極の直列合成接地抵抗値が定期的に測定されると、直列合成接地抵抗値の季節変動率が計算されるため、Ｂ種接地極及び機器用接地極それぞれの予め測定されている接地抵抗値に上記季節変動率を乗じることによってＢ種接地極及び機器用接地極それぞれの接地極の接地抵抗値を計算することができる。
これにより、Ｂ種接地極及び機器用接地極それぞれの接地抵抗値を簡易的に求めることができるため、Ｂ種接地極及び機器用接地極それぞれの接地抵抗値が電気設備技術基準に定められている許容値以下に保たれているか否かを判断することができる。
【００１１】
【発明の実施の形態】
次に、本発明の実施の形態について説明する。
図１は、電気設備技術基準で定められているＢ種接地極ＥＢと、１次側が特別高圧もしくは高圧の高低圧変圧器Ｔｒ１の低圧側電路ＬＬに接続される低圧機器ＬＭの筐体を接地するための機器用接地極（Ｄ種接地極、もしくは４００ボルト回路が存在すればＣ種接地極）ＥＤとの直列合成接地抵抗値を測定するための接地抵抗測定器１の構成を説明するための系統図である。
尚、上記低圧機器ＬＭは、電動機、電熱機器、照明機器等の電気機器や、電子機器、事務機器等の弱電機器、及び金属製電線管や金属製配線ダクト等を総称したものである。
【００１２】
Ｂ種接地極ＥＢは、高低圧変圧器Ｔｒ１の低圧側端子の一つもしくは中性線を接地するための接地極であり、Ｂ種接地極ＥＢと高低圧変圧器Ｔｒ１の低圧側端子の一つもしくは中性線とは接地線ＥＢＬで接続されている。また、低圧機器ＬＭの筐体と機器用接地極ＥＤとは接地線ＥＤＬで接続されている。
尚、接地線ＥＤＬは、一般的に良好な接地特性を有する建物の基礎Ｇに接続されることが多い。
【００１３】
図１に示すように、接地線ＥＢＬは電流検出手段である変流器ＺＣＴを貫通するようにセットされる。また、接地線ＥＢＬと接地線ＥＤＬの間に通電路２が接続されており、通電路２の中間部には可変抵抗器Ｒが直列に接続されている。尚、可変抵抗器Ｒに対して接地線ＥＢＬ側の配線２Ｌは、接地線ＥＢＬを流れる電流と反対の方向に流れる電流が検出されるように変流器ＺＣＴをセットされる。
【００１４】
変流器ＺＣＴにより検出される電流は、前記低圧側電路ＬＬから低圧機器ＬＭの筐体に漏洩した漏洩電流であり、その漏洩電流の一部Ｉ１は、接地線ＥＤＬから、通電路２の配線２Ｒ、可変抵抗器Ｒ、配線２Ｌ、接地線ＥＢＬを流れ、低圧側電路ＬＬに戻る回路を流れ、残りの漏洩電流Ｉ２は、接地線ＥＤＬから、機器用接地極ＥＤ、大地、Ｂ種接地極ＥＢ、接地線ＥＢＬを流れ、低圧側電路ＬＬに戻る回路を流れる。この場合、漏洩電流Ｉ１と漏洩電流Ｉ２は流れる方向が反対の状態で変流器ＺＣＴにより同時に検出される。
【００１５】
変流器ＺＣＴは調整手段である制御回路３に接続されており、漏洩電流Ｉ１と漏洩電流Ｉ２の電流検出信号が変流器ＺＣＴから制御回路３に入力される。制御回路３は、変流器ＺＣＴから出力された電流検出信号がゼロとなるように前述の可変抵抗器Ｒの抵抗値を調整する。制御回路３が可変抵抗器Ｒの抵抗値を調整する手段としては、フィードバック制御により可変抵抗器Ｒをサーボモータで駆動する手段や、リレースイッチ等を利用して、いくつかの抵抗素子を直並列に接続替えを行い、抵抗値を変化させる手段などがある。
【００１６】
上記のように、制御回路３が変流器ＺＣＴから出力される電流検出信号をゼロにするように前述の可変抵抗器Ｒの抵抗値を調整した場合、この状態での可変抵抗器Ｒの抵抗値がＢ種接地極ＥＢと機器用接地極ＥＤの直列合成接地抵抗値となる。この可変抵抗器Ｒの抵抗値は、制御回路３から表示装置等の出力手段４に出力される。尚、図１に示すように機器用接地極ＥＤと建物基礎Ｇが並列的に接続されている場合、可変抵抗器Ｒの抵抗値は、機器用接地極ＥＤの接地抵抗値ＲＤと建物基礎Ｇの接地抵抗値ＲＸとを並列合成した接地抵抗値とＢ種接地極ＥＢの接地抵抗値ＲＢを直列に合成した直列合成接地抵抗値と等しくなる。
Ｒ＝｛ＲＤ・ＲＸ／（ＲＤ＋ＲＸ）｝＋ＲＢ・・・・・式（１）
尚、前述の接地線ＥＤＬが建物基礎Ｇに接続されていない場合、当然、可変抵抗器Ｒの抵抗値は、機器用接地極ＥＤの接地抵抗値ＲＤとＢ種接地極ＥＢの接地抵抗値ＲＢとを直列に合成した直列合成接地抵抗値と等しくなる。
Ｒ＝ＲＤ＋ＲＢ・・・・・・・・・・・・・・・・・・式（２）
【００１７】
以上のように、変流器ＺＣＴで前述の漏洩電流Ｉ１と漏洩電流Ｉ２が同時に検出されて変流器ＺＣＴから出力される電流検出信号がゼロとなるように可変抵抗器Ｒが調整された場合、制御回路３は、式（１）で示される抵抗値を、Ｂ種接地極ＥＢと機器用接地極ＥＤと建物基礎Ｇの合成接地抵抗値として測定する。
また、前述の接地線ＥＤＬが建物基礎Ｇに接続されていない場合、制御回路３は、式（２）で示される抵抗値を、Ｂ種接地極ＥＢと機器用接地極ＥＤの直列合成接地抵抗値として測定する。
【００１８】
接地抵抗測定担当者は、接地抵抗測定器１を用いることにより、上記式（１）、式（２）で示される直列合成接地抵抗値を高低圧変圧器Ｔｒ１の竣工時から定期的に測定することによって、その直列合成接地抵抗値の季節的変動幅と季節的変動率を計算する。
【００１９】
Ｂ種接地極ＥＢ、及び、機器用接地極ＥＤは、それぞれの接地極の竣工時に、高低圧変圧器Ｔｒ１に関する電気設備と接続されていない状態でそれぞれの接地極の接地抵抗値が従来の接地抵抗計により測定されている。
Ｂ種接地極ＥＢ、及び、機器用接地極ＥＤそれぞれの接地抵抗値が、上記直列合成接地抵抗値と同様に季節的に変動するものと仮定すれば、既に測定されているＢ種接地極ＥＢ、及び、機器用接地極ＥＤそれぞれの竣工時の接地抵抗値に上記直列合成接地抵抗値の季節的変動率を乗算することによって、それぞれの接地極の接地抵抗値が電気設備技術基準で定められている許容値以下となっているか否かを判断することが可能である。
【００２０】
以上の説明した接地抵抗測定器１では、制御回路３により自動的に直列合成接地抵抗値を求めるものであるが、制御回路３を無くすとともに、変流器ＺＣＴの代わりに漏れ電流計測用の表示付き携帯型クランプセンサを用い、その表示値がゼロとなるように、即ち、前述の漏洩電流Ｉ１と漏洩電流Ｉ２が等しくなるように可変抵抗器Ｒを調整し、表示値がゼロとなったときの可変抵抗Ｒの抵抗値を機器用接地極ＥＤとＢ種接地極ＥＢの直列合成接地抵抗値としてもよい。
【００２１】
また、図１における可変抵抗器Ｒを、測定対象となるＢ種接地極ＥＢと機器用接地極ＥＤの想定される直列合成接地抵抗値の１０倍程度の固定抵抗器に代えるとともに、変流器ＺＣＴを、漏れ電流計測用の表示付き携帯型クランプセンサに代えた状態で、その表示値がゼロとなるように、表示付き携帯型クランプセンサに巻きつける配線（図１に示した配線２Ｌに相当する）の巻数Ｎを増やす。そして、その固定抵抗の抵抗値を上記配線の巻数Ｎで除した値を、機器用接地極ＥＤとＢ種接地極ＥＢの直列合成接地抵抗値としてもよい。尚、この場合、固定抵抗の抵抗値は、測定対象となるＢ種接地極ＥＢと機器用接地極ＥＤの想定される直列合成接地抵抗値より大きいほど、直列合成接地抵抗値の測定精度が高くなる。その理由は、表示付き携帯型クランプセンサに巻きつける配線の巻数Ｎが増えて検出電流の分解能が高くなるためである。
【００２２】
【発明の効果】
本発明によれば、計測用標準電圧が不要で、且つ高低圧変圧器が稼動中であってもＢ種接地極と機器用接地極の直列合成接地抵抗値を測定することができる。また、定期的に測定した直列合成接地抵抗値に基づいて計算した直列合成接地抵抗値の季節変動率を、Ｂ種接地極及び機器用接地極それぞれの竣工時に既に測定されている接地抵抗値に乗じることによって、それぞれの接地極の接地抵抗値が電気設備技術基準で定められている許容値以下に保たれているか否かを判断することができる。
【図面の簡単な説明】
【図１】接地抵抗測定器の全体的な構成と接地抵抗値を測定するための方法を説明するための系統図である。
【図２】接地抵抗値を測定するための従来の手段を説明した説明図である。
【符号の説明】
１ 接地抵抗測定器
２ 通電路
３ 制御回路
４ 出力手段
Ｔｒ１ 高低圧変圧器
ＥＢ Ｂ種接地極
ＥＤ 機器用接地極
ＥＢＬ Ｂ種接地線
ＥＤＬ 接地線
Ｒ 可変抵抗器
ＬＬ 低圧側電路
ＬＭ 低圧機器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground resistance measuring instrument and a ground resistance for measuring a series composite ground resistance value of a class B ground electrode defined in the electrical equipment technical standards and a device ground electrode for grounding a casing of a low-voltage device. It relates to a measurement method.
[0002]
[Prior art]
Conventionally, to ground one of the low-voltage side terminals of a high-low voltage transformer or a B-type grounding electrode for grounding a neutral wire, or the housing of a low-voltage device connected to the low-voltage circuit of a high-low voltage transformer When the ground resistance value of the D-type grounding electrode and the C-type grounding electrode is measured by the grounding resistance meter 20, it is performed based on a potential drop method as shown in FIG. In this potential drop method, an AC voltage output from an
[0003]
[Non-Patent Document 1]
Takehiko Takahashi “Introduction to Grounding Technology”, published by Ohmsha, Ltd., February 10, 1988 p150-153
[0004]
[Problems to be solved by the invention]
When measuring the grounding resistance value of the grounding electrode 21 to be measured, for example, the B-type grounding electrode, with the conventional grounding resistance meter 20, the customer premises are blacked out at the time of completion of electrical equipment such as a high / low voltage transformer or at the annual inspection. Therefore, the measurement target ground electrode 21 must be electrically disconnected from the high / low voltage transformer for measurement. Therefore, it is practically difficult to measure the ground resistance value of the measurement target ground electrode 21 at any time. Moreover, the alternating
In general, it is known that the grounding resistance value of the grounding electrode does not become a constant value throughout the year because it varies seasonally depending on the temperature and the amount of moisture in the ground. For this reason, only by measuring the grounding resistance value of the grounding electrode at the time of completion of the high / low voltage transformer or during the annual inspection, the grounding resistance value of the grounding electrode is less than the allowable value defined in the technical standards for electrical equipment. We cannot guarantee that it will always be kept.
[0005]
Therefore, in the present invention, even when a standard voltage for measurement is not required and a high-low voltage transformer with an extra high voltage or high voltage on the primary side is in operation, the equipment ground for grounding the B-type ground electrode and the low-voltage equipment. In addition to providing a ground resistance measuring instrument and a ground resistance measuring method capable of measuring a series composite ground resistance value with a pole, a seasonal variation rate calculated based on the measured series composite ground resistance value is calculated for a high-low voltage transformer. By multiplying the ground resistance value of each of the Class B grounding electrode and the equipment grounding electrode measured in advance at the time of completion, the grounding resistance value of each grounding electrode is kept below the allowable value defined in the electrical equipment technical standards. It is an object of the present invention to provide a ground resistance measurement method that can determine whether or not the device is in contact.
[0006]
[Means for Solving the Problems]
The above-mentioned problem can be solved by the ground resistance measuring instrument and the ground resistance measuring method described in the claims.
[0007]
According to the grounding resistance measuring device of claim 1, when a leakage current flows from the low voltage side circuit of the high / low voltage transformer to the low voltage device casing, the current detecting means causes the device grounding electrode from the low voltage device casing. , The ground, and the leakage current flowing through the first energization path that returns to the low-voltage side electric circuit via the B-type grounding electrode, and the low-voltage equipment casing returns to the low-voltage side electric circuit via the variable electrical resistance When the leakage current flowing through the connected second energization paths is simultaneously detected in the opposite energization direction, the adjustment means adjusts the variable electric resistance so that the current detection signal output from the current detection means becomes zero. In order to automatically adjust the resistance value, the output means outputs the resistance value. As described above, when the resistance value of the variable electric resistance is automatically adjusted so that the current detection value of the current detection means becomes zero, the resistance value of the variable electric resistance output from the output means is expressed as the B type grounding electrode. And measured as the series composite ground resistance value of the grounding electrode for equipment.
As a result, even if the standard voltage for measurement is not required and the high and low voltage transformer is in operation, the series combined ground resistance of the equipment ground electrode for grounding the class B ground electrode and the low voltage device can be measured. it can.
[0008]
According to the ground resistance measuring method of claim 2, when a leakage current flows from the low voltage side circuit of the high / low voltage transformer to the low voltage device casing, the device ground electrode, ground, and B Leakage current flowing through the first current path returning to the low-voltage side circuit via the seed grounding electrode, and connected to return from the low-voltage device housing to the low-voltage side circuit of the high-low voltage transformer via the variable electrical resistance When the leakage current flowing through the second current path is detected, the resistance value of the variable electrical resistance of the second current path is adjusted so that the leakage currents flowing through the first and second current paths are equal. Therefore, the series composite ground resistance value of the B-type ground electrode and the equipment ground electrode can be measured based on the resistance value of the variable electric resistance.
As a result, even if the standard voltage for measurement is not required and the high and low voltage transformer is in operation, the series combined ground resistance of the equipment ground electrode for grounding the class B ground electrode and the low voltage device can be measured. it can.
[0009]
According to the ground resistance measuring method of claim 3, when a leakage current flows from the low-voltage side circuit of the high-low voltage transformer to the housing of the low-voltage device, the device grounding electrode, ground, and A fixed current having a leakage value that flows through the first current path that returns to the low-voltage side circuit via the B-type grounding electrode, and a resistance value that is greater than the assumed series composite grounding resistance value of the B-type grounding electrode and the equipment grounding electrode In a state in which the leakage current flowing through the second current path having resistance is detected by the current transformer so that the current directions of the respective leakage currents are opposite to each other, the number of turns to the current transformer of the second current path is determined. The leakage current flowing through the first and second current paths is adjusted so that the current detected by the current transformer becomes zero. Based on the number of turns to the current transformer of the second current path in this state and the resistance value of the fixed electrical resistance, the series composite ground resistance value of the class B ground electrode and the equipment ground electrode can be obtained.
Thereby, even if the standard voltage for measurement is unnecessary and the high and low voltage transformer is in operation, it is possible to obtain the series composite ground resistance of the class B ground electrode and the device ground electrode for grounding the low voltage device. .
[0010]
According to the ground resistance measuring method of claim 4, when the series composite ground resistance value of the class B ground electrode and the equipment ground electrode is periodically measured, the seasonal variation rate of the series composite ground resistance value is calculated. Therefore, the ground resistance value of each of the B-type ground electrode and the equipment ground electrode is calculated by multiplying the previously measured ground resistance value of each of the Class B ground electrode and the equipment ground electrode by the above-mentioned seasonal variation rate. be able to.
As a result, the ground resistance value of each of the class B grounding electrode and the equipment grounding electrode can be easily obtained. Therefore, the grounding resistance value of each of the class B grounding electrode and the equipment grounding electrode is defined in the electrical equipment technical standards. It can be determined whether or not it is kept below a certain allowable value.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described.
FIG. 1 shows the grounding of the B type grounding electrode EB defined by the electric equipment technical standards and the housing of the low-voltage equipment LM whose primary side is connected to the low-voltage side circuit LL of the high-low voltage transformer Tr1 having an extra high voltage or high voltage. In order to explain the configuration of the ground resistance measuring instrument 1 for measuring a series composite ground resistance value with a device ground electrode (a class D ground electrode or a class C ground electrode if a 400 volt circuit is present) ED It is a systematic diagram.
The low-voltage device LM is a generic term for electric devices such as electric motors, electric heating devices, and lighting devices, weak electric devices such as electronic devices and office equipment, and metal conduits and metal wiring ducts.
[0012]
The class B grounding electrode EB is a grounding electrode for grounding one of the low-voltage side terminals of the high-low voltage transformer Tr1 or a neutral wire, and is one of the class-B grounding electrode EB and the low-voltage side terminal of the high-low voltage transformer Tr1. Two or neutral wires are connected by a ground wire EBL. The casing of the low-voltage device LM and the device grounding electrode ED are connected by a grounding wire EDL.
The ground line EDL is generally connected to a foundation G of a building having generally good ground characteristics.
[0013]
As shown in FIG. 1, the ground line EBL is set so as to penetrate the current transformer ZCT which is a current detection means. In addition, the energization path 2 is connected between the ground line EBL and the ground line EDL, and a variable resistor R is connected in series to an intermediate portion of the energization path 2. Note that the current transformer ZCT is set so that the current flowing in the direction opposite to the current flowing through the ground line EBL is detected in the
[0014]
The current detected by the current transformer ZCT is a leakage current leaked from the low voltage side circuit LL to the casing of the low voltage device LM, and a part of the leakage current I1 is wired from the ground line EDL to the current path 2. 2R, variable resistor R,
[0015]
The current transformer ZCT is connected to the control circuit 3 which is an adjusting means, and current detection signals of the leakage current I1 and the leakage current I2 are input from the current transformer ZCT to the control circuit 3. The control circuit 3 adjusts the resistance value of the aforementioned variable resistor R so that the current detection signal output from the current transformer ZCT becomes zero. As a means for the control circuit 3 to adjust the resistance value of the variable resistor R, some resistance elements are connected in series and parallel using a means for driving the variable resistor R with a servo motor by feedback control, a relay switch, or the like. There is a means for changing the resistance value by changing the connection.
[0016]
As described above, when the control circuit 3 adjusts the resistance value of the variable resistor R so that the current detection signal output from the current transformer ZCT is zero, the resistance of the variable resistor R in this state The value is a series composite ground resistance value of the B-type ground electrode EB and the equipment ground electrode ED. The resistance value of the variable resistor R is output from the control circuit 3 to output means 4 such as a display device. As shown in FIG. 1, when the equipment grounding electrode ED and the building foundation G are connected in parallel, the resistance value of the variable resistor R is the resistance value RD of the equipment grounding electrode ED and the building foundation G. Are equal to the series combined ground resistance value obtained by combining the ground resistance value RB of the B-type grounding electrode EB in series.
R = {RD · RX / (RD + RX)} + RB (1)
When the above-described ground line EDL is not connected to the building foundation G, naturally, the resistance value of the variable resistor R is the ground resistance value RD of the equipment grounding electrode ED and the grounding resistance value RB of the class B grounding electrode EB. Is equal to the series combined ground resistance value obtained by combining
R = RD + RB ... Formula (2)
[0017]
As described above, when the variable resistor R is adjusted so that the current detection signal output from the current transformer ZCT is zero by simultaneously detecting the leakage current I1 and the leakage current I2 described above with the current transformer ZCT. The control circuit 3 measures the resistance value represented by the formula (1) as a combined ground resistance value of the B-type grounding electrode EB, the equipment grounding electrode ED, and the building foundation G.
Further, when the above-described ground line EDL is not connected to the building foundation G, the control circuit 3 uses the resistance value represented by the equation (2) as the series composite ground resistance of the class B ground electrode EB and the equipment ground electrode ED. Measure as a value.
[0018]
The person in charge of ground resistance measurement uses the ground resistance measuring instrument 1 to periodically measure the series composite ground resistance value represented by the above formulas (1) and (2) from the time of completion of the high / low voltage transformer Tr1. Thus, the seasonal fluctuation range and the seasonal fluctuation rate of the series composite ground resistance value are calculated.
[0019]
Class B grounding electrode EB and equipment grounding electrode ED are not connected to electrical equipment related to high / low voltage transformer Tr1 at the time of completion of each grounding electrode. It is measured by an ohmmeter.
Assuming that the ground resistance value of each of the class B ground electrode EB and the equipment ground electrode ED varies seasonally in the same manner as the series composite ground resistance value, the class B ground electrode EB that has already been measured. And by multiplying the ground resistance value at the time of completion of each grounding electrode ED for equipment by the seasonal variation rate of the series composite grounding resistance value, the grounding resistance value of each grounding electrode is determined by the electrical equipment technical standards. It is possible to determine whether or not the value is equal to or less than the allowable value.
[0020]
In the above-described ground resistance measuring instrument 1, the series combined ground resistance value is automatically obtained by the control circuit 3, but the control circuit 3 is eliminated and a display for measuring leakage current is used instead of the current transformer ZCT. When the variable resistor R is adjusted so that the displayed value becomes zero, that is, the leakage current I1 and the leakage current I2 are equal, and the displayed value becomes zero. The resistance value of the variable resistor R may be a series combined ground resistance value of the equipment grounding electrode ED and the B-type grounding electrode EB.
[0021]
In addition, the variable resistor R in FIG. 1 is replaced with a fixed resistor that is about 10 times the assumed series composite ground resistance value of the B-type grounding electrode EB and the equipment grounding electrode ED to be measured. Wiring (corresponding to the
[0022]
【The invention's effect】
According to the present invention, it is possible to measure the series composite ground resistance value of the class B ground electrode and the equipment ground electrode even when the standard voltage for measurement is unnecessary and the high / low voltage transformer is in operation. Moreover, the seasonal variation rate of the series composite ground resistance value calculated based on the series composite ground resistance value measured periodically is changed to the ground resistance value already measured at the completion of each of the class B ground electrode and the equipment ground electrode. By multiplying, it is possible to determine whether or not the grounding resistance value of each grounding electrode is kept below the allowable value defined in the electrical equipment technical standards.
[Brief description of the drawings]
FIG. 1 is a system diagram for explaining an overall configuration of a ground resistance measuring instrument and a method for measuring a ground resistance value.
FIG. 2 is an explanatory diagram for explaining conventional means for measuring a ground resistance value.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Grounding resistance measuring device 2 Current path 3 Control circuit 4 Output means Tr1 High / low voltage transformer EB Class B grounding electrode ED Equipment grounding electrode EBL Class B grounding wire EDL Grounding wire R Variable resistor LL Low voltage side electric circuit LM Low voltage equipment
Claims (4)
前記高低圧変圧器の低圧側電路から前記低圧機器の筐体に漏洩電流が流れた場合、前記低圧機器の筐体から前記機器用接地極、大地、及び前記Ｂ種接地極を介して前記低圧側電路に戻る第１の通電路を流れる漏洩電流と、前記低圧機器の筐体から可変電気抵抗を介して当該高低圧変圧器の低圧側電路に戻るように接続された第２の通電路を流れる漏洩電流とを、前記第１の通電路を流れる漏洩電流の通電方向と反対の通電方向で同時に検出する電流検出手段と、前記電流検出手段から出力される電流検出信号がゼロになるように前記可変電気抵抗の抵抗値を自動的に調整する調整手段と、前記調整手段で調整された可変電気抵抗の抵抗値を外部に出力する出力手段とを備え、前記電流検出手段の電流検出値がゼロになるように前記可変電気抵抗の抵抗値が自動的に調整された場合の当該可変電気抵抗の抵抗値に基づいて前記Ｂ種接地極と前記機器用接地極の直列合成接地抵抗値を測定することを特徴とする接地抵抗測定器。A B-type grounding electrode for grounding one of the low-voltage side terminals or the neutral wire of the high-low voltage transformer, and a device for grounding the casing of the low-voltage equipment used in the low-voltage circuit of the high-low voltage transformer A ground resistance measuring instrument for measuring a series composite ground resistance value with a ground electrode for use,
When a leakage current flows from the low voltage side electric circuit of the high / low voltage transformer to the housing of the low voltage device, the low voltage is supplied from the housing of the low voltage device through the device grounding electrode, the ground, and the class B grounding electrode. A leakage current flowing through the first energization path returning to the side electric circuit, and a second energization path connected so as to return to the low-voltage side electric circuit of the high-low voltage transformer from the housing of the low-voltage device via a variable electrical resistance. A current detecting means for simultaneously detecting a flowing leakage current in an energization direction opposite to an energizing direction of the leakage current flowing through the first energization path; and a current detection signal output from the current detecting means becomes zero. An adjustment unit that automatically adjusts the resistance value of the variable electric resistance; and an output unit that outputs the resistance value of the variable electric resistance adjusted by the adjustment unit to the outside. The current detection value of the current detection unit is The variable electrical resistance is set to zero. Measuring the series combined grounding resistance value of the B-type grounding electrode and the equipment grounding electrode based on the resistance value of the variable electrical resistance when the resistance value of the device is automatically adjusted. vessel.
前記高低圧変圧器の低圧側電路から前記低圧機器の筐体に漏洩電流が流れた場合、前記低圧機器の筐体から前記機器用接地極、大地、及び前記Ｂ種接地極を介して前記低圧側電路に戻る第１の通電路を流れる漏洩電流と、前記低圧機器の筐体から可変電気抵抗を介して当該高低圧変圧器の低圧側電路に戻るように接続された第２の通電路を流れる漏洩電流とを検出する行程と、前記第１、第２の二つの通電路を流れる漏洩電流が等しくなるように前記第２の通電路の可変電気抵抗の抵抗値を調整する行程と、前記第１、第２の二つの通電路を流れる漏洩電流が等しくなるように前記第２の通電路の可変電気抵抗の抵抗値が調整された場合の当該抵抗値に基づいて前記Ｂ種接地極と前記機器用接地極の直列合成接地抵抗値を測定する行程とを有することを特徴とする接地抵抗測定方法。A B-type grounding electrode for grounding one of the low-voltage side terminals or the neutral wire of the high-low voltage transformer, and a device for grounding the casing of the low-voltage equipment used in the low-voltage circuit of the high-low voltage transformer A ground resistance measurement method for measuring a series composite ground resistance value with a ground electrode for use,
When a leakage current flows from the low voltage side electric circuit of the high / low voltage transformer to the housing of the low voltage device, the low voltage is supplied from the housing of the low voltage device through the device grounding electrode, the ground, and the class B grounding electrode. A leakage current flowing through the first energization path returning to the side electric circuit, and a second energization path connected so as to return to the low-voltage side electric circuit of the high-low voltage transformer from the housing of the low-voltage device via a variable electrical resistance. A step of detecting a leakage current flowing, a step of adjusting a resistance value of the variable electrical resistance of the second current path so that the leakage currents flowing through the first and second current paths are equal, and Based on the resistance value when the variable electrical resistance value of the second current path is adjusted so that the leakage currents flowing through the first and second current paths are equal, Measuring the series composite ground resistance value of the equipment grounding electrode. Ground resistance measurement method according to claim Rukoto.
前記高低圧変圧器の低圧側電路から前記低圧機器の筐体に漏洩電流が流れた場合、前記低圧機器の筐体から前記機器用接地極、大地、及び前記Ｂ種接地極を介して前記低圧側電路に戻る第１の通電路を流れる漏洩電流と、前記低圧機器の筐体から前記Ｂ種接地極と前記機器用接地極の想定直列合成接地抵抗値より大きい抵抗値の固定電気抵抗を介して前記高低圧変圧器の低圧側電路に戻るように接続された第２の通電路を流れる漏洩電流とを、それぞれの漏洩電流の通電方向が反対になるように変流器により検出する行程と、前記第２の通電路の変流器への巻数を調整して前記第１、第２の二つの通電路を流れる漏洩電流の検出電流がゼロになるように調整する行程と、変流器の検出電流がゼロになるように前記第２の通電路の変流器への巻数が調整された場合の巻数と前記固定電気抵抗の抵抗値に基づいて前記Ｂ種接地極と前記機器用接地極の直列合成接地抵抗値を求める行程とを有することを特徴とする接地抵抗測定方法。A B-type grounding electrode for grounding one of the low-voltage side terminals or the neutral wire of the high-low voltage transformer, and a device for grounding the casing of the low-voltage equipment used in the low-voltage circuit of the high-low voltage transformer A ground resistance measurement method for measuring a series composite ground resistance value with a ground electrode for use,
When a leakage current flows from the low voltage side electric circuit of the high / low voltage transformer to the housing of the low voltage device, the low voltage is supplied from the housing of the low voltage device through the device grounding electrode, the ground, and the class B grounding electrode. A leakage current flowing through the first current path returning to the side circuit, and a fixed electrical resistance having a resistance value greater than an assumed series composite ground resistance value of the type B ground electrode and the device ground electrode from the housing of the low-voltage device. And a step of detecting the leakage current flowing through the second energization path connected so as to return to the low-voltage side circuit of the high-low voltage transformer by a current transformer so that the energization directions of the respective leakage currents are opposite to each other. Adjusting the number of turns of the second current path to the current transformer to adjust the leakage current flowing through the first and second current paths to zero, and a current transformer. Winding the second current path around the current transformer so that the detected current of the current becomes zero. And a step of obtaining a series composite ground resistance value of the B-type grounding electrode and the equipment grounding electrode based on the number of turns when the resistance is adjusted and the resistance value of the fixed electric resistance. .
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| CN102866301A (en) * | 2012-09-18 | 2013-01-09 | 深圳远征技术有限公司 | Grounding resistance analyzing device and grounding resistance analyzing method |
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| CN102866301A (en) * | 2012-09-18 | 2013-01-09 | 深圳远征技术有限公司 | Grounding resistance analyzing device and grounding resistance analyzing method |
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