JPH0528348B2 - - Google Patents
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- Publication number
- JPH0528348B2 JPH0528348B2 JP60130598A JP13059885A JPH0528348B2 JP H0528348 B2 JPH0528348 B2 JP H0528348B2 JP 60130598 A JP60130598 A JP 60130598A JP 13059885 A JP13059885 A JP 13059885A JP H0528348 B2 JPH0528348 B2 JP H0528348B2
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- JP
- Japan
- Prior art keywords
- ground fault
- voltage
- fault resistance
- ground
- grounding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000000034 method Methods 0.000 claims description 4
- 238000001514 detection method Methods 0.000 description 23
- 230000000694 effects Effects 0.000 description 9
- 238000010586 diagram Methods 0.000 description 8
- 230000002411 adverse Effects 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 4
- 238000009413 insulation Methods 0.000 description 4
- 230000007423 decrease Effects 0.000 description 2
- 230000007257 malfunction Effects 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Measurement Of Resistance Or Impedance (AREA)
Description
【発明の詳細な説明】
〔産業上の利用分野〕
この発明は、１点接地系採用の電気設備の接地
系の地絡抵抗を検出する地絡抵抗検出方法に関す
る。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ground fault resistance detection method for detecting ground fault resistance of a grounding system of electrical equipment employing a single point grounding system.
電気設備、特に高電圧、大電流の設備（例え
ば、核融合装置の電源設備）においては、その信
頼性向上等のために１点接地系が採用されている
が、この接地系は、それに接続された機器の水漏
れ、絶縁劣化、機械的変位等のために地絡抵抗
（即ち、対地に対する抵抗）を介して地絡する場
合がある。そのような状態で電気設備を運転する
と大事故につながることもあり、従つて接地系の
地絡抵抗を検出することは電気設備の安全運転及
び信頼性向上等の観点から極めて重要である。
Single-point grounding systems are used for electrical equipment, especially high-voltage and large-current equipment (for example, power equipment for nuclear fusion devices), to improve their reliability. Ground faults may occur due to water leakage, insulation deterioration, mechanical displacement, etc. of equipment that has been exposed to ground faults due to ground fault resistance (that is, resistance to ground). Operating electrical equipment under such conditions may lead to a major accident, and therefore, detecting the ground fault resistance of the grounding system is extremely important from the viewpoint of safe operation and reliability improvement of electrical equipment.
第３図は、従来の地絡抵抗検出方法の説明する
ための回路図である。電気設備２の接地系４は、
実際は複雑に枝分かれしている場合もあるが、こ
こでは単純化している。その接地系４を主接地点
７に接地する接地線６にスイツチ１８の挿入し、
更に接地系４にスイツチ２０を介して地絡抵抗検
出用の直流電源２６を接続するようにしている。 FIG. 3 is a circuit diagram for explaining a conventional ground fault resistance detection method. The grounding system 4 of the electrical equipment 2 is
In reality, there may be complex branches, but we have simplified them here. Insert the switch 18 into the grounding wire 6 that grounds the grounding system 4 to the main grounding point 7,
Further, a DC power supply 26 for detecting ground fault resistance is connected to the grounding system 4 via a switch 20.
電気設備２を運転する時は、スイツチ１８を閉
に、スイツチ２０を開にして接地系４を１点接地
する。又、地絡抵抗を測定する時は、スイツチ１
８を開にしてスイツチ２０を閉にし、接地系４に
所定時間だけ直流電圧Ｅを印加する。そしてその
時の電圧計２２及び電流計２４の値を読み取り、
それぞれの値をV0，I0とすれば、地絡抵抗８の抵
抗値Ｒは、Ｒ＝V0／I0より求める。 When operating the electrical equipment 2, the switch 18 is closed and the switch 20 is opened to ground the grounding system 4 at one point. Also, when measuring ground fault resistance, switch 1
8 is opened, switch 20 is closed, and DC voltage E is applied to grounding system 4 for a predetermined period of time. Then, read the values of the voltmeter 22 and ammeter 24 at that time,
If the respective values are V 0 and I 0 , then the resistance value R of the ground fault resistor 8 is determined from R=V 0 /I 0 .
第４図は、従来の地絡抵抗検出方法において接
地系に印加される直流電圧を示す図である。従来
の方法においては、この図に示すように、比較的
高電圧（例えば、500〜1000V程度）の直流電圧
Ｅを、比較的長時間（例えば、１分間程度）接地
系４に印加している。 FIG. 4 is a diagram showing the DC voltage applied to the ground system in the conventional ground fault resistance detection method. In the conventional method, as shown in this figure, a relatively high voltage (for example, about 500 to 1000 V) DC voltage E is applied to the grounding system 4 for a relatively long time (for example, about 1 minute). .
上述のような地絡抵抗検出方法においては、地
絡抵抗検出動作中（即ち、試験中）に、接地系４
に比較的高電圧を比較的長時間印加するため、接
地系４に悪影響を与える可能性がある。例えば、
接地系４に絶縁劣化をもたらせたり、既にあつた
絶縁劣化を促進したりする可能性がある。
In the ground fault resistance detection method as described above, during the ground fault resistance detection operation (i.e., during the test),
Since a relatively high voltage is applied for a relatively long period of time, there is a possibility that the grounding system 4 will be adversely affected. for example,
This may cause insulation deterioration in the grounding system 4 or accelerate insulation deterioration that has already occurred.
更に、地絡抵抗８を検出する度にスイツチ１８
を開にしなければならないので、地絡抵抗８を繰
り返し監視することはできない。加えて、スイツ
チ１８は接地系４を主接地点７に接地する経路に
挿入されているため、その信頼性は極めて高いも
のが要求される。万一、スイツチ１８が開のまま
電気設備２を運転すれば、無接地となり大事故に
波及する恐れがある。 Furthermore, every time the ground fault resistance 8 is detected, the switch 18 is turned on.
Since the ground fault resistance 8 must be kept open, the ground fault resistance 8 cannot be repeatedly monitored. In addition, since the switch 18 is inserted into the path for grounding the grounding system 4 to the main grounding point 7, it is required to have extremely high reliability. If the electrical equipment 2 were to be operated with the switch 18 open, it would become ungrounded, which could lead to a major accident.
従つてこの発明は、上記のような接地系の地絡
抵抗を、接地系に与える悪影響を最小限にしてし
かも安全に検出することができる地絡抵抗検出方
法を提供することを主たる目的とする。 Therefore, the main object of the present invention is to provide a ground fault resistance detection method that can safely detect the ground fault resistance of the ground system as described above while minimizing the adverse effects on the ground system. .
この発明の地絡抵抗検出方法は、接地系の接地
線に、変流器を介して、周波数が数百Hz程度の高
周波でピーク値が数十ｍＶ〜数百ｍＶ程度の低電
圧を数サイクル程度の短時間誘起せしめ、この電
圧と接地系に流れる電流の比から地絡抵抗を検出
することを特徴とする。
In the ground fault resistance detection method of the present invention, a low voltage with a high frequency of several hundred Hz and a peak value of several tens of mV to several hundred mV is applied to the grounding line of the grounding system via a current transformer for several cycles. The ground fault resistance is detected from the ratio of this voltage and the current flowing through the ground system.
この発明の地絡抵抗検出方法においては、接地
線に変流器を介して上記のような高周波の低電圧
を短時間誘起せしめる。従つて、接地線を接地点
から切り離す必要はない。接地系に地絡抵抗があ
れば、それに応じた電流が接地系に流れるので、
この電流と誘起せしめた電圧との比によつて接地
系の地絡抵抗を検出することができる。
In the ground fault resistance detection method of the present invention, a high frequency low voltage as described above is induced in the ground wire for a short time via a current transformer. Therefore, there is no need to disconnect the ground wire from the ground point. If there is a ground fault resistance in the ground system, a corresponding current will flow through the ground system, so
The ground fault resistance of the ground system can be detected by the ratio of this current to the induced voltage.
第１図は、この発明に係る地絡抵抗検出方法を
説明するための回路図の一例である。電気設備２
の接地系４の接地線６に、例えば貫通形の変流器
１０及び１２を取付け、後で詳述するように、駆
動電源１４から変流器１０に駆動電圧V2を供給
して、接地線６に（即ち、地絡ループＬに）高周
波の低電圧V1を短時間誘起させる（印加する）。
これによつて、接地系４に地絡抵抗８が生じてい
る場合には接地線６に電流I1が流れ、これを変流
器１２で検出し、更に必要に応じて増幅回路１６
で増幅する。そしてこの時の地絡抵抗８の抵抗値
Ｒを、上記電圧V1および電流I1を用いて、Ｒ＝
V1／I1より求める。これの演算には、種々の公知
の手段が利用できる。
FIG. 1 is an example of a circuit diagram for explaining the ground fault resistance detection method according to the present invention. Electrical equipment 2
For example, through-type current transformers 10 and 12 are attached to the grounding wire 6 of the grounding system 4, and as will be described in detail later, the drive voltage V2 is supplied from the drive power supply 14 to the current transformer 10, and the grounding A high-frequency low voltage V 1 is induced (applied) to the line 6 (that is, to the ground fault loop L) for a short time.
As a result, when a ground fault resistance 8 occurs in the grounding system 4, a current I1 flows through the grounding wire 6, which is detected by the current transformer 12, and is further detected by the amplifier circuit 16 as necessary.
Amplify with. Then, the resistance value R of the ground fault resistor 8 at this time is determined by using the above voltage V 1 and current I 1 , R=
Calculated from V 1 /I 1 . Various known means can be used for this calculation.
第２図は、この発明により接地線に誘起される
電圧V1の波形の一例を示す図である。この電圧
V1は、周波数が数百Hz、例えば100〜500Hzの高
周波であり、印加時間Ｔが数サイクル、例えば３
〜５サイクルの短時間であり、ピーク値Vpが数
十ｍＶ〜数百ｍＶの低電圧である。 FIG. 2 is a diagram showing an example of the waveform of the voltage V1 induced in the ground line according to the present invention. this voltage
V 1 is a high frequency with a frequency of several hundred Hz, for example 100 to 500 Hz, and the application time T is several cycles, for example 3
It is a short period of ~5 cycles, and is a low voltage with a peak value Vp of several tens of mV to several hundred mV.
このような電圧V1を変流器１０を介して接地
線６に誘起させるため、駆動電源１４から、上記
と同様の周波数及び印加時間で変流器１０の巻数
比に応じた大きさの駆動電圧V2を変流器１０に
供給する。この場合、変流器１０の１次／２次の
巻数比をａとすれば、V2＝V1／ａで定まり、こ
の巻数比ａを１／数百とすれば、上述のような電
圧V1を誘起させるための駆動電圧V2のピーク値
は、数Ｖ〜数十Ｖ、例えば３〜30V程度となる。 In order to induce such a voltage V 1 in the grounding wire 6 via the current transformer 10, a drive voltage corresponding to the turns ratio of the current transformer 10 is applied from the drive power source 14 at the same frequency and application time as above. A voltage V 2 is supplied to the current transformer 10 . In this case, if the primary/secondary turns ratio of the current transformer 10 is a, it is determined by V 2 =V 1 /a, and if this turns ratio a is 1/several hundred, the above voltage The peak value of the driving voltage V 2 for inducing V 1 is from several volts to several tens of volts, for example, about 3 to 30 volts.
接地線６に誘起させる電圧V1として、通常考
えられる連続した商用周波数のものと違つて、上
述のような高周波、低電圧、短時間のものが好ま
しい理由を説明すると、第１図に示したような地
絡抵抗検出回路においても、地絡抵抗８の検出動
作中に接地系４に１回の測定のために長時間電圧
を印加すると、絶縁劣化を進行させる等の悪影響
を接地系４や地絡ループＬに与える恐れが無いと
は言えない。そのような悪影響を最小限にするた
めには、接地線６に誘起させる電圧V1はできる
限り短時間のもの、例えばパルス電圧のようなも
のの方が良い。しかし、接地線６に流れる電流I1
等を或る程度正確に検出するためには、或る程度
の時間が必要である。従つて印加時間Ｔは、上述
のように数サイクル程度が好ましい。 The reason why the voltage V 1 induced in the grounding wire 6 is preferable to be a high frequency, low voltage, short time voltage as described above, unlike the normally considered continuous commercial frequency voltage, is as shown in Figure 1. Even in such a ground fault resistance detection circuit, if a voltage is applied to the ground system 4 for a long time for one measurement while the ground fault resistance 8 is being detected, it may cause negative effects such as progressing insulation deterioration on the ground system 4 and the ground fault resistance 8. It cannot be said that there is no risk of damaging the ground fault loop L. In order to minimize such adverse effects, it is preferable that the voltage V 1 induced in the ground line 6 be as short as possible, such as a pulse voltage. However, the current I 1 flowing through the grounding wire 6
etc., a certain amount of time is required to detect them with a certain degree of accuracy. Therefore, the application time T is preferably about several cycles as described above.
又、電圧V1の大きさも、接地系４に与える悪
影響を最小限にするため、地絡抵抗８を検出でき
る最小の電圧、例えば数十ｍＶ〜数百ｍＶ程度の
電圧が好ましい。 Furthermore, in order to minimize the adverse effect on the grounding system 4, the magnitude of the voltage V1 is preferably the minimum voltage at which the ground fault resistance 8 can be detected, for example, a voltage of about several tens of mV to several hundred mV.
更に、一般に変流器においては、出力電圧を一
定とするならば、それの磁束密度は周波数に逆比
例して小さくできるので、駆動電圧V2の周波数
が高い方が変流器１０及び１２を小形にすること
ができる。しかし、あまり周波数が高いと漂遊容
量が大となる等の問題が生じるので、駆動電圧
V2は数百Hz程度の高周波が好ましく、従つてこ
れによつて誘起される電圧V1も同じ高周波とな
る。又、電圧V1の周波数を高周波とすると、電
気設備２に一般に用いられている商用周波と容易
に弁別できるため、検出上の誤動作を防止するこ
ともできる。更に、変流器１０及び１２が小形に
なると、それらを接地系４内の複数箇所に設置す
ることが容易となる。 Furthermore, in general, in a current transformer, if the output voltage is kept constant, its magnetic flux density can be reduced in inverse proportion to the frequency. Can be made small. However, if the frequency is too high, problems such as large stray capacitance will occur, so the driving voltage
V 2 is preferably a high frequency of about several hundred Hz, and therefore the voltage V 1 induced thereby also has the same high frequency. Moreover, if the frequency of the voltage V 1 is set to a high frequency, it can be easily distinguished from the commercial frequency commonly used in the electrical equipment 2, so that malfunctions in detection can be prevented. Furthermore, when the current transformers 10 and 12 are made smaller, it becomes easier to install them at multiple locations within the grounding system 4.
従つて、上述したような地絡抵抗検出方法によ
れば、接地系に与える悪影響を最小限にして地絡
抵抗を検出することが可能となる。又、それ故、
上記のような電圧V1を間欠的に繰り返して誘起
させるようにしてもよく、そのようにすれば、地
絡抵抗の繰り返し監視をすることも、接地系に与
える悪影響を最小限にして行うことができる。更
に接地系を主接地点から切り離す必要はないので
安全である。 Therefore, according to the ground fault resistance detection method as described above, it is possible to detect the ground fault resistance while minimizing the adverse effects on the ground system. Also, therefore,
The above voltage V 1 may be induced repeatedly intermittently, and in this way, the earth fault resistance can be repeatedly monitored while minimizing the adverse effects on the earthing system. I can do it. Furthermore, it is safe because there is no need to separate the grounding system from the main grounding point.
又、単に電源から流出する電流の値を検出する
だけで地絡を検出する場合は、電流電圧変動の影
響を受けて検出精度が低下するが、この地絡抵抗
検出方法では、印加電圧とそれによつて接地系に
流れる電流との比から地絡抵抗を検出するので、
電源電圧変動の影響を受けず、検出精度が高くな
るという効果も得られる。例えば、話を簡単にす
るために電源電圧が半分になつたとすると、地絡
抵抗を有する接地系に流れる電流も半分になるの
で、単に電流を検出するだけでは、正確な地絡検
出は望めない。ところが、電源電圧が半分になり
電流が半分になつても、両者の比である地絡抵抗
について見れば不変であるから、地絡抵抗を検出
するようにしておけば、電源電圧変動の影響は受
けない。 In addition, when detecting a ground fault by simply detecting the value of the current flowing from the power supply, the detection accuracy decreases due to the influence of current and voltage fluctuations, but with this ground fault resistance detection method, the applied voltage and its Therefore, since the ground fault resistance is detected from the ratio with the current flowing in the ground system,
It is also possible to obtain the effect of increasing detection accuracy without being affected by power supply voltage fluctuations. For example, to keep things simple, if the power supply voltage is halved, the current flowing through the grounding system that has a ground fault resistance will also be halved, so you cannot expect accurate ground fault detection by simply detecting the current. . However, even if the power supply voltage is halved and the current is halved, the ground fault resistance, which is the ratio of the two, remains unchanged, so if the ground fault resistance is detected, the influence of power supply voltage fluctuations can be reduced. I don't accept it.
尚、前述した変流器１０及び１２は、巻線形と
して接地線６の途中に挿入接続しても良い。又、
変流器１０及び１２は、接地系４内の任意の接地
線に取付けても良く、しかも複数箇所に取付けて
も良い。 Incidentally, the current transformers 10 and 12 described above may be inserted and connected in the middle of the ground wire 6 as winding wires. or,
The current transformers 10 and 12 may be attached to any grounding wire in the grounding system 4, and may be attached at a plurality of locations.
更に、接地線６に流れる電流I1を検出する方法
としては、第１図に示したように変流器１２で直
接に検出するものの他に、駆動電源１４と変流器
１０との間に変流器を入れてそこを流れる電流を
測定してそれを電流I1に換算し、言わば間接的に
電流I1を検出する方法もある。又、接地線６に誘
起される電圧V1は、第１図に示した回路では、
V1＝aV2から算出できるが、これ以外に、変流器
１０に３次巻線を設けてそこの電圧V3を検出し、
変流器１０の１次／３次の巻数比をa3としてV1
＝a3V3から算出することもできる。 Furthermore, as a method of detecting the current I 1 flowing through the grounding wire 6, in addition to directly detecting it with the current transformer 12 as shown in FIG. There is also a method of indirectly detecting current I 1 by inserting a current transformer, measuring the current flowing through it, and converting it to current I 1 . In addition, the voltage V 1 induced in the grounding wire 6 is as follows in the circuit shown in FIG.
It can be calculated from V 1 = aV 2 , but in addition to this, a tertiary winding is provided in the current transformer 10 and the voltage V 3 there is detected,
Assuming that the primary/tertiary turns ratio of the current transformer 10 is a 3 , V 1
It can also be calculated from = a 3 V 3 .
以上のようにこの発明によれば、接地系の接地
線に変流器を介して上記のような高周波の低電圧
を短時間誘起せしめるので、電気設備の接地系に
与える悪影響を最小限にしてその地絡抵抗を検出
することができる。又、上記のような高周波を使
用しているので、変流器を小形にすることができ
ると共に、商用周波と容易に弁別できるため検出
上の誤動作を防止することもできる。しかも、地
絡抵抗の検出の際に接地系を主接地点から切り離
す必要が無いので、地絡抵抗の常時監視が可能で
あると共に安全性も高い。
As described above, according to the present invention, the above-mentioned high-frequency low voltage is induced in the grounding line of the grounding system via the current transformer for a short time, thereby minimizing the negative impact on the grounding system of electrical equipment. Its ground fault resistance can be detected. Furthermore, since the above-mentioned high frequency is used, the current transformer can be made compact, and since it can be easily distinguished from the commercial frequency, it is also possible to prevent malfunctions in detection. Moreover, since there is no need to disconnect the grounding system from the main grounding point when detecting the ground fault resistance, the ground fault resistance can be constantly monitored and safety is high.
又、単に電源から流出する電流の値を検出する
だけで地絡を検出する場合は、電源電圧変動の影
響を受けて検出精度が低下するが、この発明の地
絡抵抗検出方法では、印加電圧とそれによつて接
地系に流れる電流との比から地絡抵抗を検出する
ようにしているので、電源電圧変動の影響を受け
ず、検出精度が高くなるという効果も得られる。 In addition, when detecting a ground fault by simply detecting the value of the current flowing from the power supply, the detection accuracy decreases due to the influence of power supply voltage fluctuation, but in the ground fault resistance detection method of this invention, the applied voltage Since the ground fault resistance is detected from the ratio of the current flowing through the ground system and the current flowing through the ground system, it is not affected by power supply voltage fluctuations and the detection accuracy is improved.
第１図は、この発明に係る地絡抵抗検出方法を
説明するための回路図の一例である。第２図は、
この発明により接地線に誘起される電圧の波形の
一例を示す図である。第３図は、従来の地絡抵抗
検出方法を説明するための回路図である。第４図
は、従来の地絡抵抗検出方法において接地系に印
加される直流電圧を示す図である。
２……電気設備、４……接地系、６……接地
線、８……地絡抵抗、１０，１２……変流器、
V1……接地線に誘起される電圧、I1……接地系に
流れる電流。
FIG. 1 is an example of a circuit diagram for explaining the ground fault resistance detection method according to the present invention. Figure 2 shows
FIG. 3 is a diagram showing an example of the waveform of a voltage induced in a ground line according to the present invention. FIG. 3 is a circuit diagram for explaining a conventional ground fault resistance detection method. FIG. 4 is a diagram showing the DC voltage applied to the ground system in the conventional ground fault resistance detection method. 2...Electrical equipment, 4...Grounding system, 6...Grounding wire, 8...Ground fault resistance, 10, 12...Current transformer,
V 1 ... Voltage induced in the grounding wire, I 1 ... Current flowing in the grounding system.
Claims (1)
抗を検出する方法であつて、当該接地系の接地線
に、変流器を介して、周波数が数百Hz程度の高周
波でピーク値が数十ｍＶ〜数百ｍＶ程度の低電圧
を数サイクル程度の短時間誘起せしめ、この電圧
と接地系に流れる電流の比から地絡抵抗を検出す
ることを特徴とする地絡抵抗検出方法。1 A method for detecting the ground fault resistance of the grounding system of electrical equipment that uses a single-point grounding system, in which the peak value is detected at a high frequency of about several hundred Hz through a current transformer in the grounding wire of the grounding system. A method for detecting ground fault resistance, characterized in that a low voltage of several tens of mV to several hundred mV is induced for a short period of time of several cycles, and ground fault resistance is detected from the ratio of this voltage to the current flowing through the ground system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13059885A JPS61288171A (en) | 1985-06-14 | 1985-06-14 | Detecting method for grounding resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13059885A JPS61288171A (en) | 1985-06-14 | 1985-06-14 | Detecting method for grounding resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61288171A JPS61288171A (en) | 1986-12-18 |
| JPH0528348B2 true JPH0528348B2 (en) | 1993-04-26 |
Family
ID=15038037
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13059885A Granted JPS61288171A (en) | 1985-06-14 | 1985-06-14 | Detecting method for grounding resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61288171A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997004323A1 (en) * | 1995-07-19 | 1997-02-06 | The Nippon Signal Co., Ltd. | Apparatus for detecting discontinuity of ground conductor and leak detector having function of detecting discontinuity of ground conductor |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007121028A (en) * | 2005-10-26 | 2007-05-17 | Hitachi Building Systems Co Ltd | Insulation resistance diagnostic system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5421721Y2 (en) * | 1973-10-19 | 1979-08-01 |
-
1985
- 1985-06-14 JP JP13059885A patent/JPS61288171A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997004323A1 (en) * | 1995-07-19 | 1997-02-06 | The Nippon Signal Co., Ltd. | Apparatus for detecting discontinuity of ground conductor and leak detector having function of detecting discontinuity of ground conductor |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61288171A (en) | 1986-12-18 |
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