JP2004309182A - Instrument and method for measuring ground resistance - Google Patents
Instrument and method for measuring ground resistance Download PDFInfo
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Abstract
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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grounding resistance measuring instrument and a grounding resistance measuring series combined grounding resistance of a class B grounding electrode defined by the technical standards of electrical equipment and a grounding electrode for equipment for grounding a housing of a low-voltage equipment. Related to the measurement method.
[0002]
[Prior art]
Conventionally, to ground one of the low-voltage terminals of a high-low voltage transformer or a B-type grounding electrode for grounding the neutral conductor, or to ground the housing of a low-voltage device connected to the low-voltage circuit of the high-low voltage transformer When the ground resistance of the D-class ground electrode or the C-class ground electrode is measured by the ground resistance meter 20, the measurement is performed based on the potential drop method as shown in FIG. The potential drop method is to apply an AC voltage output from an
[0003]
[Non-patent document 1]
Takehiko Takahashi, Introduction to Grounding Technology, Ohmsha Publishing Co., Ltd., February 10, 1988, p150-153
[0004]
[Problems to be solved by the invention]
When measuring the grounding resistance of the grounding electrode 21 to be measured, for example, the class B grounding electrode, with the above-mentioned conventional grounding resistance meter 20, when the electrical equipment such as a high-low voltage transformer or the like is completed, or when the annual inspection is performed, the power in the customer premises is interrupted. The measurement must be performed by electrically disconnecting the ground electrode 21 to be measured from the high / low voltage transformer. Therefore, it is practically difficult to measure the ground resistance value of the measurement target ground electrode 21 at any time. Further, an
In general, it is known that the grounding resistance value of the grounding electrode does not become constant throughout the year because it varies seasonally depending on the temperature and the water content of the ground. Therefore, simply measuring the grounding resistance of the grounding electrode only at the time of completion of the high-low voltage transformer or at the time of annual inspection, the grounding resistance of the grounding electrode falls below the allowable value specified by the Electrical Equipment Technical Standards. We cannot guarantee that it is always kept.
[0005]
Therefore, in the present invention, even if a standard voltage for measurement is not required and the primary side is operating a special high voltage or high voltage low / high voltage transformer, the class B grounding electrode and the equipment ground for grounding the low voltage equipment are used. A ground resistance measuring instrument and a ground resistance measuring method capable of measuring a series combined ground resistance value with a pole are provided, and a seasonal variation rate calculated based on the measured series combined ground resistance value is calculated for a high-low voltage transformer. By multiplying the ground resistance values of the class B ground electrode and the equipment ground electrode measured in advance at the time of completion, the ground resistance value of each ground electrode is kept below the allowable value specified in the Electrical Equipment Technical Standards. It is an object of the present invention to provide a ground resistance measuring method capable of judging whether or not the ground resistance is measured.
[0006]
[Means for Solving the Problems]
The above object can be solved by a ground resistance measuring instrument and a ground resistance measuring method described in the claims.
[0007]
According to the grounding resistance measuring device of the present invention, 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 current detecting means moves the grounding electrode for the device from the housing of the low-voltage device. , Ground, and leakage current flowing through the first current path returning to the low-voltage side electric circuit via the B-type grounding electrode, and returning to the low-voltage side electric circuit of the high-low-voltage transformer via the variable electric resistance from the housing of the low-voltage device. When the leakage current flowing through the second current path connected as described above is detected simultaneously in the opposite direction of current flow, 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 changed to the class B ground electrode. It is measured as the series combined ground resistance value of the device and the ground electrode for the device.
This makes it possible to measure the series combined ground resistance of the class B ground electrode and the equipment ground electrode for grounding the low-voltage equipment even when the standard voltage for measurement is unnecessary and the high-low voltage transformer is operating. it can.
[0008]
According to the grounding resistance measuring method of claim 2, 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 equipment grounding pole, the ground, and the B from the low-voltage device housing. A leakage current flowing through the first current path returning to the low-voltage side electric circuit via the seed grounding electrode, and a connection is made to return to the low-voltage side electric circuit of the high / low-voltage transformer via a variable electric resistance from the housing of the low-voltage device. When the leakage current flowing through the second current path is detected, the resistance value of the variable electric resistance of the second current path is adjusted so that the leakage current flowing through the first and second current paths becomes equal. Therefore, based on the resistance value of the variable electric resistance, the series combined ground resistance value of the class B ground electrode and the equipment ground electrode can be measured.
This makes it possible to measure the series combined ground resistance of the class B ground electrode and the equipment ground electrode for grounding the low-voltage equipment even when the standard voltage for measurement is unnecessary and the high-low voltage transformer is operating. it can.
[0009]
According to the grounding resistance measuring method of claim 3, 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 device grounding pole, the ground, and the low-voltage device housing. A leakage current flowing through the first current path returning to the low-voltage side electric circuit via the class-B ground electrode, and a fixed electricity having a resistance value larger than an assumed series combined ground resistance value of the class-B ground electrode and the equipment ground electrode. The number of turns of the second current path to the current transformer is determined in a state where the 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 leakage current flowing through the first and second current paths is adjusted so that the current detected by the current transformer becomes zero. In this state, the series combined ground resistance value of the class B ground electrode and the equipment ground electrode can be obtained based on the number of turns of the second current path to the current transformer and the resistance value of the fixed electric resistance.
Thus, even when the standard voltage for measurement is unnecessary and the high-low voltage transformer is in operation, the series combined ground resistance of the class B ground electrode and the equipment ground electrode for grounding the low-voltage equipment can be obtained. .
[0010]
According to the ground resistance measuring method of the fourth aspect, when the series combined ground resistance value of the class B ground electrode and the equipment ground electrode is periodically measured, the seasonal variation rate of the series combined ground resistance value is calculated. Therefore, the ground resistance value of each of the class B 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 seasonal variation rate. be able to.
This makes it possible to easily determine the ground resistance value of each of the Class B ground electrode and the equipment ground electrode. Therefore, the ground resistance value of each of the Class B ground electrode and the equipment ground electrode is determined by the technical standards for electrical equipment. It can be determined whether or not the value is kept below the allowable value.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described.
FIG. 1 illustrates the grounding of the type-B grounding electrode EB defined in the technical standards for electrical equipment and the housing of the low-voltage device LM whose primary side is connected to the low-voltage side electric circuit LL of the high-low-voltage transformer Tr1 of extra high voltage or high voltage. The grounding resistance measuring device 1 for measuring a series combined grounding resistance value with a device grounding pole (D-class grounding pole or a C-class grounding pole if a 400 volt circuit is present) ED to perform the measurement is described. FIG.
The low-voltage device LM is a general term for electric devices such as electric motors, electric heating devices, and lighting devices, weak electric devices such as electronic devices and office devices, and metal conduits and metal wiring ducts.
[0012]
The class B ground electrode EB is a ground electrode for grounding one of the low-voltage terminals of the high / low voltage transformer Tr1 or the neutral wire, and is one of the low voltage terminals of the class B ground electrode EB and the high / low voltage transformer Tr1. Or the neutral line is connected to a ground line EBL. Further, the housing of the low-voltage device LM and the device ground electrode ED are connected by a ground line EDL.
The ground line EDL is often connected to the foundation G of a building having generally good grounding characteristics.
[0013]
As shown in FIG. 1, the ground line EBL is set so as to pass through a current transformer ZCT which is a current detecting means. A current 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 current path 2. The current transformer ZCT is set on the
[0014]
The current detected by the current transformer ZCT is a leakage current leaking from the low-voltage side electric circuit LL to the housing of the low-voltage device LM, and a part I1 of the leakage current is transmitted from the ground line EDL to the wiring of the current path 2. 2R, the variable resistor R, the
[0015]
The current transformer ZCT is connected to the control circuit 3 as adjusting means, and current detection signals of the leakage current I1 and the leakage current I2 are input to the control circuit 3 from the current transformer ZCT. 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 becomes zero. As means for the control circuit 3 to adjust the resistance value of the variable resistor R, means for driving the variable resistor R with a servomotor by feedback control, or using a relay switch or the like to connect several resistance elements in series and parallel. There is a method of changing the connection and changing the resistance value.
[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 becomes zero, the resistance of the variable resistor R in this state is adjusted. The value is a series combined ground resistance value of the class B 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. When the equipment ground electrode ED and the building foundation G are connected in parallel as shown in FIG. 1, the resistance value of the variable resistor R is equal to the ground resistance value RD of the equipment ground electrode ED and the building foundation G. And the ground resistance value RX obtained by combining the ground resistance value RX of the B-type ground electrode EB in series with the ground resistance value obtained by combining the ground resistance values RX in parallel with each other.
R = {RD.RX / (RD + RX)} + RB... Formula (1)
When the above-mentioned ground line EDL is not connected to the building foundation G, the resistance value of the variable resistor R is naturally the ground resistance value RD of the equipment ground electrode ED and the ground resistance value RB of the class B ground electrode EB. Are combined in series to be equal to a series combined ground resistance value.
R = RD + RB (2)
[0017]
As described above, when the above-described leakage current I1 and leakage current I2 are simultaneously detected by the current transformer ZCT and the variable resistor R is adjusted so that the current detection signal output from the current transformer ZCT becomes zero. The control circuit 3 measures the resistance value represented by the equation (1) as a combined ground resistance value of the class B ground electrode EB, the equipment ground electrode ED, and the building foundation G.
When the above-mentioned ground line EDL is not connected to the building foundation G, the control circuit 3 sets the resistance value represented by the equation (2) to a series combined 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 measuring the ground resistance uses the ground resistance measuring device 1 to periodically measure the series combined 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 combined ground resistance value are calculated.
[0019]
The class B ground pole EB and the equipment ground pole ED have the ground resistance of each ground pole at the time of completion of each ground pole in a state where the ground resistance value of each ground pole is not connected to the electrical equipment related to the high / low voltage transformer Tr1. It is measured by a resistance meter.
Assuming that the ground resistance values of the class B ground electrode EB and the device ground electrode ED fluctuate seasonally similarly to the series combined ground resistance value, the class B ground electrode EB already measured is assumed. , And by multiplying the ground resistance at the time of completion of each of the equipment ground poles ED by the seasonal variation rate of the series combined ground resistance, the ground resistance of each ground pole is determined by the electrical equipment technical standards. It is possible to determine whether or not it is equal to or less than the allowable value.
[0020]
In the grounding resistance measuring device 1 described above, the series combined grounding resistance is automatically obtained by the control circuit 3. However, the control circuit 3 is eliminated, and a display for measuring a leakage current is provided instead of the current transformer ZCT. When the variable resistor R is adjusted so that the display value becomes zero, that is, the above-described leakage current I1 and the leakage current I2 are equalized using the portable clamp sensor with May be used as a series combined ground resistance value of the equipment ground electrode ED and the class B ground electrode EB.
[0021]
Further, the variable resistor R in FIG. 1 is replaced with a fixed resistor having a value of about 10 times the assumed series combined ground resistance value of the type B ground electrode EB and the equipment ground electrode ED to be measured, and a current transformer. Wiring (equivalent to the
[0022]
【The invention's effect】
According to the present invention, a series combined ground resistance value of the class B ground electrode and the equipment ground electrode can be measured even when the standard voltage for measurement is unnecessary and the high / low voltage transformer is operating. In addition, the seasonal variation rate of the series combined ground resistance calculated based on the series combined ground resistance measured periodically is changed to the ground resistance already measured at the completion of each of the Class B ground pole and the equipment ground pole. By multiplying, it is possible to determine whether or not the ground resistance value of each ground electrode is maintained at or below an allowable value defined by 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 device and a method for measuring a ground resistance value.
FIG. 2 is an explanatory view illustrating a conventional means for measuring a ground resistance value.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ground resistance measuring device 2 Current path 3 Control circuit 4 Output means Tr1 High / low voltage transformer EB Class B ground pole ED Equipment ground pole EBL Class B ground wire EDL Ground wire R Variable resistor LL Low voltage side circuit LM Low voltage device
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 device for grounding one of the low-voltage terminals of the high-low voltage transformer or a class B ground electrode for grounding the neutral conductor, and a low-voltage device housing used in the low-voltage circuit of the high-low voltage transformer A ground resistance measuring device for measuring a series combined ground resistance value with a ground electrode for
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 equipment, the low-voltage equipment is connected to the low-voltage equipment via the equipment grounding pole, the ground, and the B-type grounding pole. A leakage current flowing through the first current path returning to the side power path and a second current path connected to return to the low voltage side power path of the high / low voltage transformer via a variable electric resistance from the housing of the low voltage device. Current detection means for simultaneously detecting the flowing leakage current in the direction of current flow opposite to the direction of current flow of the leakage current flowing through the first current path, and a current detection signal output from the current detection means being zero. Adjustment means for automatically adjusting the resistance value of the variable electric resistance, and output means for outputting the resistance value of the variable electric resistance adjusted by the adjustment means to the outside, wherein the current detection value of the current detection means is The variable electrical resistor is set to zero. Measuring the series combined ground resistance value of the class B ground electrode and the device ground electrode based on the resistance value of the variable electric 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 device for grounding one of the low-voltage terminals of the high-low voltage transformer or a class B ground electrode for grounding the neutral conductor, and a low-voltage device housing used in the low-voltage circuit of the high-low voltage transformer A ground resistance measuring method for measuring a series combined ground resistance value with a ground electrode for
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 equipment, the low-voltage equipment is connected to the low-voltage equipment via the equipment grounding pole, the ground, and the B-type grounding pole. A leakage current flowing through the first current path returning to the side power path and a second current path connected to return to the low voltage side power path of the high / low voltage transformer via a variable electric resistance from the housing of the low voltage device. A step of detecting a flowing leakage current, a step of adjusting a resistance value of a variable electric resistance of the second current path so that the leakage current flowing through the first and second current paths becomes equal, When the resistance value of the variable electric resistance of the second current path is adjusted so that the leakage currents flowing through the first and second two current paths become equal, the B-type ground electrode is Measuring a series combined earth resistance value of the equipment earth 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 device for grounding one of the low-voltage terminals of the high-low voltage transformer or a class B ground electrode for grounding the neutral conductor, and a low-voltage device housing used in the low-voltage circuit of the high-low voltage transformer A ground resistance measuring method for measuring a series combined ground resistance value with a ground electrode for
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 equipment, the low-voltage equipment is connected to the low-voltage equipment via the equipment grounding pole, the ground, and the B-type grounding pole. A leakage current flowing through a first current path returning to the side electric circuit, and a fixed electric resistance having a resistance value larger than an assumed series combined ground resistance value of the class B ground electrode and the equipment ground electrode from the housing of the low voltage device. Detecting the leakage current flowing through the second current path connected back to the low-voltage side electric circuit of the high-low voltage transformer with a current transformer so that the direction of current flow of each leakage current is opposite. Adjusting the number of turns of the second current path to the current transformer so as to adjust the detection current of the leakage current flowing through the first and second two current paths to zero; and So that the detected current of the second current path becomes zero. Determining a series combined ground resistance value of the class B ground electrode and the equipment ground electrode based on the number of turns when the resistance is adjusted and the resistance value of the fixed electrical resistance. .
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