JPS6036970A - Method for measuring insulation resistance - Google Patents

Abstract

PURPOSE:To measure exactly the insulation resistance of an electric line, etc. including an electronic circuit in which the stray capacity to ground tends to increase by applying the measuring signal voltages having the low frequencies f1 and f2 to the electric line via the ground line of a transformer and deriving a difference between the value obtd. by adding the weight (f1/f2)<2> to the effective component of the frequency f1 and the effective component of the frequency f2. CONSTITUTION:Oscillators OSC1 and OSC2 for generating respectively the low frequency signals f1 and f2 are connected in series to a ground line LE and the signal of the same voltage V is impressed thereto. On the other hand, the output from a zero phase current converter ZCT is branched and is inputted to one input terminal of synchronous detection circuits MULT1 and MULT2 via band- pass filters BFP1 and BFP2 of respectively f1 and f2 central frequencies and at the same time the outputs from both oscillators OSC1 and OSC2 are inputted respectively to the other input terminals of the circuits MULT1 and MULT2.

Description

【発明の詳細な説明】 本発明は活線状態にて電路等の絶縁抵抗を測定する方法
、殊に対地浮遊容量大なる場合無視し得なくなる接地抵
抗を補償した絶縁抵抗測定方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the insulation resistance of an electrical circuit or the like in a live line state, and particularly to an insulation resistance measuring method that compensates for the ground resistance, which cannot be ignored when the stray capacitance to ground is large.

従来、漏電等の早期発見の為には第１図に示す如き電路
の絶縁抵抗測定方法を用いるのが一般的であった。Conventionally, for early detection of electrical leakage, etc., it has been common to use a method of measuring the insulation resistance of electrical circuits as shown in FIG.

即ち、２なる負荷を有する受電変圧器Ｔの第２種接地線
Ｌｘを介して発振器Ｏ８Ｃがら商用周波数と異なった周
波数ｆｌなる測定用低周波信号電圧全電路Ｌ１及びＬ２
に印加し、前記接地線ＬＥを貫通する零相変流器ＺＣＴ
によって絶縁抵抗Ｒ・及び浮遊容量Ｃを介して帰還する
漏洩７ｎ流全検出する。That is, a low frequency signal voltage for measurement having a frequency fl different from the commercial frequency is transmitted from the oscillator O8C through the second type grounding line Lx of the power receiving transformer T having two loads, all electric lines L1 and L2.
and a zero-phase current transformer ZCT passing through the grounding wire LE.
All leakage 7n currents returning via insulation resistance R and stray capacitance C are detected.

この際前記零相変流器ＺＣＴの出力に含まれる周波数ｆ
１の成分をフィルター”　Ｉ　Ｌ　Ｔにて検出しその漏
洩電流中の有効分を例えば前記発振器Ｏ８Ｃの出力上用
いて掛算器ＭＴＪＬＴで同期検波して電路の絶縁抵抗を
測定するものであった。At this time, the frequency f included in the output of the zero-phase current transformer ZCT
1 component is detected by a filter "ILT", and the effective component of the leakage current is used, for example, on the output of the oscillator O8C and synchronously detected by a multiplier MTJLT to measure the insulation resistance of the electrical circuit.

その測定理論を第２図の等価回路全用いて更に説明する
ならば前記接地線ＬＥの接地点ＥＩ！ｃ介して前記発振
器Ｏ８Ｃに帰還する電流を１とすると ■ １−葺＋ｊωＩＣｖ（但しω１＝２π、ｆ１）・・・・
・・・・・（１）であるから印加する交流電圧と同相の
成分、即ち上記Ｕ）式右辺第１項に比例した値を同期検
波等の手法を用いて検出すれば絶縁抵抗Ｒ・に逆比例し
た測定値を得るものである。To further explain the measurement theory using the entire equivalent circuit shown in FIG. 2, the grounding point EI of the grounding wire LE! If the current that returns to the oscillator O8C via c is 1, then ■ 1-fuki+jωICv (however, ω1=2π, f1)...
・・・・・・Since (1) is satisfied, if the component in phase with the applied AC voltage, that is, the value proportional to the first term on the right side of the above equation U) is detected using a method such as synchronous detection, the insulation resistance R can be obtained. It obtains a measurement value that is inversely proportional.

しかしながら上記ａ）式からも明らかな如くこの測定法
は接地線ＬＥに大地を介して帰還する電流を測定するに
も拘らず接地抵抗を無視しているので対地浮遊容量Ｃが
大きくなると接地抵抗の影響が現われ測定値が現実の電
路の絶縁抵抗とはなはだしくかけ離れたものとなる、即
ち正確な絶縁抵抗の測定が不可能になるという欠陥があ
った。However, as is clear from equation a) above, this measurement method ignores the grounding resistance even though it measures the current that returns to the grounding line LE via the ground, so when the stray capacitance C to ground increases, the grounding resistance There was a defect in that the measured value became extremely different from the insulation resistance of the actual electric circuit, that is, it became impossible to accurately measure the insulation resistance.

本発明は上述の如き従来の絶縁抵抗測定方法の欠陥を除
去すべくなされたものであって、変圧器の接地線を介し
て電路にｆｌ及びｆ２なる低周波数の測定信号電圧全印
加し、前記接地線に帰還する前記画周波数の漏洩電流を
個別に検出した上でこれら両者の有効分を同期検波によ
って抽出すると共に前記−の周波数ｆ１の有効分に（ｆ
ｌ／ｆ２）　なる重み付けを与えた値と前記他の周波数
ｆ２の有効分との差をとることによって活線状態の電路
の絶縁抵抗を測定するよう等した絶縁抵抗測定方法を提
供せんとするものである。The present invention has been made in order to eliminate the defects of the conventional insulation resistance measuring method as described above. After individually detecting the leakage current of the above-mentioned image frequency that returns to the grounding wire, the effective components of both of them are extracted by synchronous detection, and the effective component of the above-mentioned - frequency f1 (f
l/f2) and the effective component of the other frequency f2 to provide an insulation resistance measuring method equivalent to measuring the insulation resistance of a live electrical circuit. It is.

以下本発明をその理論と図面に示す実施例とに基づいて
詳細に説明する。The present invention will be described in detail below based on its theory and embodiments shown in the drawings.

先ず、本発明に係る絶縁抵抗測定方法全説明する前に、
その理解を助ける為従来の手法の欠陥を少しく詳細に説
明する。First, before fully explaining the insulation resistance measurement method according to the present invention,
In order to facilitate understanding, the deficiencies of the conventional method will be explained in some detail.

第３図は接地抵抗ｒを考慮した場合の等価回路図である
。FIG. 3 is an equivalent circuit diagram when earthing resistance r is considered.

この場合接地点Ｅｆ介して発振器Ｏ８Ｃに帰還する電流
ｉＩｘとしこれを ■！＝（Ａ＋ｊＢ）Ｖ−・・・・・・・・・・・・・・
・・・（シシ）とする。このとき、 であリレ）式で接地抵抗ｒ’６無視すれば前記Ｕ）式と
同一になることはいうまでもない。In this case, the current iIx that returns to the oscillator O8C via the ground point Ef is defined as ■! =(A+jB)V-・・・・・・・・・・・・・・・
...(shishi). At this time, it goes without saying that if the earthing resistance r'6 is ignored in the Lillet equation, it becomes the same as the above-mentioned equation U).

さて３）式において、対地浮遊容量Ｃ＝０のとらＡは１
／Ｒ・と考えてよく前記Ｑ）式の同相分はＶ／Ｒ・とな
り、同相分を検出することにより絶縁れる如く正しい絶
縁抵抗を測定していないことになる。Now, in equation 3), the tora A of the floating capacitance to ground C=0 is 1
/R·, the in-phase component of the equation Q) becomes V/R·, which means that the correct insulation resistance is not measured so that insulation can be achieved by detecting the in-phase component.

このような誤差が実際上どの程度になるかを以下に示す
。The actual extent of such errors will be shown below.

一般にｎ・）γであるから０）式においてＢ・＋γ→Ｒ
・とすると と表し得る。In general, n・)γ, so in the equation 0), B・+γ→R
・It can be expressed as.

ココテ例えば　ｆ　１＝２０Ｈｚ　、ｃ＝５　μＩ’　
。For example, f 1 = 20Hz, c = 5 μI'
.

＝＝ｉ、ｏｏΩとすると ごＹ２ （ω＊＃）　＝　（２πＸ２０ｘ５Ｘ１０″Ｘ１００）
２主３．９５Ｘ１０−３ となり（ωｌＣγ）２（１である。If ==i, ooΩ, then Y2 (ω*#) = (2πX20x5X10″X100)
2 main 3.95X10-3, which is (ωlCγ)2(1).

したがってＵ）式は とみなしてよい。Therefore, U) formula is It can be considered as

従って、例えばＪｔ＝２０Ｈｚ　、　ｅ＝＝５μＦ　、
　ｌ（・＝１００にΩ、γ＝ｉｏｏΩの場合前記６）式
の（）内は１＋（ω＋Ｃ）”Ｒ，γ＝４．９５ となり、同相分から検出されるべき絶縁抵抗値１００に
Ωは　１００にΩ／４．９５＝２０．２にΩとして測定
されてしまうことになる。Therefore, for example, Jt=20Hz, e==5μF,
When l(・=100 is Ω and γ=iooΩ, the parentheses in equation 6) are 1+(ω+C)”R, γ=4.95, and Ω is 100 for the insulation resistance value 100 to be detected from the in-phase component. It will be measured as Ω/4.95=20.2.

斯くの如く、従来の接地抵抗を無視した絶縁抵抗測定方
法では対地浮遊容量が大きい場合極めて測定誤差が大き
くなる欠陥を有すること前述の通りである。更に対地浮
遊器量には一般電子機器の電源回路に付加されるノイズ
フィルりのキャパシタンスも含まれるので今後対地浮遊
容量は大きくなっていく傾向にあるから従来の方法では
ます１す正確な画定結果が得られないことになる。As described above, the conventional method of measuring insulation resistance that ignores ground resistance has the drawback that the measurement error becomes extremely large when the stray capacitance to ground is large. Furthermore, since the amount of stray capacitance to the ground includes the noise fill capacitance added to the power supply circuit of general electronic equipment, the stray capacitance to the ground will tend to increase in the future, so conventional methods cannot provide accurate determination results. You won't get it.

この問題全解決する為不発明に於いては以下の如き手法
をとる。In order to completely solve this problem, we will take the following approach.

即ち、周波数ｆ１の印加信号によって得られる同相分、
即ち有効分’ｋｉｇｔ　とすると前記（２）及び（５）
式から どなる。That is, the in-phase component obtained by the applied signal of frequency f1,
In other words, if the effective amount is 'kigt', then (2) and (5) above
There was a roar from the ceremony.

又、周波数ｆ２＜ｆＩ＼Ｊ゛２）の印加信号にょっと近
似できる。Moreover, it can be somewhat approximated to the applied signal of frequency f2<fI\J゛2).

上記両式から を得る。From both equations above get.

と表わすことができる。It can be expressed as

ここでａ２は一定値に維持し得るからｉｇｌ及び１ｇ２
を検出しく９）式の通り１ｇ２にａ２に重み係数として
掛けその値とｉｇｌとの差をめることにより接地抵抗ｒ
の影ｅ　ｔキャンセルして電路の絶縁抵抗ｌ（・に逆比
例したＶ／Ｒ・全測定することができる。Here, since a2 can be maintained at a constant value, igl and 1g2
9) As per formula 9), multiply 1g2 by a2 as a weighting coefficient and find the difference between that value and igl to calculate the grounding resistance r.
By canceling the shadow of ET, it is possible to measure V/R, which is inversely proportional to the insulation resistance of the electric circuit.

このような測定法全実現する為には以下の如くすればよ
い。In order to fully realize such a measurement method, the following steps should be taken.

第４図は本発明に係る絶縁抵抗測定方法を実現する為の
回路の一実施例を示す図である。FIG. 4 is a diagram showing an embodiment of a circuit for realizing the insulation resistance measuring method according to the present invention.

即ち、接地線ＬＥに夫々ｆｌ及びｆ２なる低周波信号発
生用の発振器Ｏ８Ｃ１及び０８Ｃｚ＜直列に接続して同
一電圧Ｖなる信号を印加する。That is, oscillators O8C1 and O8Cz for generating low frequency signals fl and f2, respectively, are connected in series to the ground line LE, and signals of the same voltage V are applied thereto.

一方、前記零相変流器ＺＣＴの出力を分枝して中心周波
数が夫々ｆｌ及びｆ２のバンドパス・フィルタＢＦＰ　
１及びＢＦＰ２　＞介して同期検波回路ＭＵＬＴ１及び
Ｍ［Ｊｌ、Ｔ２の一人カ端に入力せしめると共に前記両
発撮器０８Ｃ１及びＯ２０２の出力を夫々前記同期検波
回路ＭＵＬ’ｌ’ｌ及びＭＵＬＴ２の他の入力端に入力
せしめる。On the other hand, the output of the zero-phase current transformer ZCT is branched to form bandpass filters BFP whose center frequencies are fl and f2, respectively.
1 and BFP2>, the outputs of the two oscillators 08C1 and O202 are input to the other terminals of the synchronous detection circuits MUL'l'l and MULT2, respectively. Input it to the input terminal.

これら両同期検波回路の出方は夫々前述（６）式及びｑ
）式のｉｇｌ及び１ｇ２．に相当する信号となるのでこ
れらを引算器８０Ｂに入力せしめた上で予じめ与えられ
ている（ｆｌ／ｆ２）２に相当する値ｋｉｇ２に掛け、
その値とｉｇｌとの差を出力ＯＵＴに出力するよう構成
したものである。The outputs of these two synchronous detection circuits are shown in equation (6) and q
) of the formulas igl and 1g2. Since the signals correspond to
The configuration is such that the difference between that value and igl is output to the output OUT.

上述の実施例は第５図に示す如く変形してもよい。The embodiment described above may be modified as shown in FIG.

即ち、前記接地線ＬＥに接続する発振器’ｃｆ１なる周
波数を発振する単一の矩形波発振器Ｏ８に置換すると共
に該発振器Ｏ８の出力全分枝してｆ１以外の高調波、例
えば３ｆｌ全中心周波数とするバンドパス・フィルりＢ
ＦＰ３’に介して前記同期検波回路ＭＵＬＴ２の他の入
力端に入力せしめるようにしてもよい。この際前記零相
変流器ＺＣＴの分校出力も同様のバンドパス・フィルタ
ＢＦＰ３ｉ介して同期検波回路ＭＴＪＬＴｚに入力せし
めるべきことはいうまでもない。That is, the frequency of the oscillator 'cf1 connected to the ground line LE is replaced with a single rectangular wave oscillator O8 that oscillates, and all the outputs of the oscillator O8 are branched to generate harmonics other than f1, for example, 3fl all center frequencies. Bandpass fill B
The signal may be input to another input terminal of the synchronous detection circuit MULT2 via FP3'. At this time, it goes without saying that the branch output of the zero-phase current transformer ZCT should also be input to the synchronous detection circuit MTJLTz via a similar band-pass filter BFP3i.

斯くすることによって単一の発振器Ｏ８が発振する測定
用信号周波数ｆ１及び同時に発振されるｆｌの高調波成
分　例えば３ｆ１　’ｃ他の信号周波数ｆ２として利用
することができるので発振益金節約することが可能であ
る。In this way, the measurement signal frequency f1 oscillated by a single oscillator O8 and the harmonic component of fl simultaneously oscillated, for example 3f1 'c, can be used as another signal frequency f2, so oscillation profit can be saved. It is.

もっともこのような手段によればｆ＝及びｆ２の信号電
圧が夫々相違することになるのでその相違分だけ一方の
信号を増幅或は減衰させる必要がある。However, according to such means, the signal voltages of f= and f2 will be different, so it is necessary to amplify or attenuate one signal by the difference.

例えば　ｆ　２　＝　３　ｆ　１とした場合にはａ２−
（ｆｌ／ｆ２）２−（ｆ１／３ｆ１）２−１／９となる
。（７）式に於けるＶは（６）式のそれの１７３となっ
ているので（基本周波数ｆｌに対し３ｆｌの成分は１／
３となるため）前記引算器５ＬＩＢに於いて１ｇ２ｋｌ
／９Ｘ３＝１／３に減衰せしめればよい。For example, if f 2 = 3 f 1, a2-
(fl/f2)2-(f1/3f1)2-1/9. Since V in equation (7) is 173 of that in equation (6) (the component of 3fl with respect to the fundamental frequency fl is 1/
3) In the subtractor 5LIB, 1g2kl
It is sufficient to attenuate it to /9X3=1/3.

本発明に係る絶縁抵抗測定方法を実現するについては上
述の実施例に限定する必要性は全くなく、例えば第１図
の回路に於いて前記発振器０ＳＣの発振周波数とバンド
パス・フィルタＦＩＬＴの選択特性を切り換え得るよう
にしておきｆｌについて先ず測定しその出力を一時記憶
し然る後にｆｌについて測定しこれらの差ヲ（９）式に
従って引算器ＳＵＢで演算する如き時分割処理を行って
もよい。In order to realize the insulation resistance measuring method according to the present invention, there is no need to limit it to the above-described embodiment. For example, in the circuit shown in FIG. It is also possible to perform time-sharing processing such as first measuring fl, temporarily storing the output, and then measuring fl and computing the difference between them using the subtracter SUB according to equation (9). .

本発明は以上説明した如き手法によって電路の絶縁抵抗
を測定するものであるから接地抵抗の影響を完全にキャ
ンセルすることが可能となるのみならず発振器等の出力
抵抗の影咎ヲも接地抵抗に加味して補償するので対地浮
遊容量増大の傾向にある電子回路を含んだ電路等の絶縁
抵抗を正確に測定する上で著しい効果を発揮する。Since the present invention measures the insulation resistance of the electrical circuit using the method explained above, it is not only possible to completely cancel the influence of the ground resistance, but also to eliminate the influence of the output resistance of the oscillator etc. on the ground resistance. Since it takes into account and compensates, it is extremely effective in accurately measuring the insulation resistance of electrical circuits, etc., including electronic circuits, which tend to increase stray capacitance to ground.

更に実施例からも明らかな如く本発明の測定方法を実現
する測定用回路は極めて簡単、従って安価に供給可能で
あるから工場、各家庭等の電路の絶縁状態自動監視シス
テムに適用する際殊に効果的である。Furthermore, as is clear from the examples, the measuring circuit for implementing the measuring method of the present invention is extremely simple and can therefore be supplied at low cost, making it particularly suitable when applied to automatic monitoring systems for the insulation condition of electric circuits in factories, households, etc. Effective.

伺、実施例に於いては説明簡単の為単相２綜の場合を示
したが本発明はこれに限定する必然性は全くなく単相３
綜或は３相３線の場合であっても同一の原理に基づいて
実施可能なことは明らかであろう。In the example, the case of a single-phase 2-heel is shown for the sake of simplicity, but the present invention is not necessarily limited to this, and the case of a single-phase 3-heel is shown.
It is clear that the same principle can be used even in the case of a heald or three-phase three-wire system.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は従来の絶縁抵抗測定方法を説明するブロック図
、第２図はその等価回路図、第３図は接地抵抗を考慮し
た場合の等価回路図、第４図は本発明に係る絶縁抵抗測
定方法を実現する為の一実施例を示すブロック図、第５
図は他の実施例を示すブロック図でおる。 Ｔ・・・・・・・・・変圧器、　Ｌｌ及びＬ２・・・・
・・・・・電路、ＬＥ・・・・・・・・・接地線、　Ｏ
２０及びＯ８・・・・・・・・・発振器、　ＭＵＬＴ・
・・叩・・同期検波回路、ＳＵＢ・・−・・・・・・引
算回路 ％詐出願人　東洋通信機株式会社Fig. 1 is a block diagram explaining the conventional insulation resistance measurement method, Fig. 2 is its equivalent circuit diagram, Fig. 3 is an equivalent circuit diagram when grounding resistance is considered, and Fig. 4 is the insulation resistance according to the present invention. Block diagram showing an embodiment for realizing the measurement method, No. 5
The figure is a block diagram showing another embodiment. T......Transformer, Ll and L2...
...Electric circuit, LE...Ground wire, O
20 and O8...Oscillator, MULT・
...Synchronous detection circuit, SUB...Subtraction circuit% Fraudulent applicant Toyo Tsushinki Co., Ltd.

Claims (1)

【特許請求の範囲】[Claims] 変圧器の接地線ヲ介して電路に相異なる２周波数ｆｌ及
びｆ２なる低周波の測定信号電圧を電磁誘導或は直列結
合によって印加し、前記接地線に帰還する周波数ｆ＝及
びｆ２の漏洩電流を個別に検出してこれら両者の有効分
を夫々同期検波によって抽出すると共に前記画周波数比
の自乗の重みを付した前記−の周波数信号の有効分と前
記側の周波数信号の有効分との差をめることによって接
地抵抗を補償して活線状態にて電路の絶縁抵抗を測定す
るようにしたこと全特徴とする絶縁抵抗測定方法。Apply low-frequency measurement signal voltages of two different frequencies fl and f2 to the electrical circuit through the ground wire of the transformer by electromagnetic induction or series combination, and leakage currents of frequencies f= and f2 that return to the ground wire are generated. The difference between the effective component of the - frequency signal and the effective component of the frequency signal on the above side, which are individually detected and the effective components of both are extracted by synchronous detection, and weighted by the square of the image frequency ratio is calculated. An insulation resistance measuring method characterized in that the insulation resistance of an electrical circuit is measured in a live line state by compensating for grounding resistance.