JPS58127172A - Insulation resistance measuring apparatus for electric line with suppressed stray capacity - Google Patents

Abstract

PURPOSE:To enable a highly accurate measurement of insulation resistance under a hot-line condition in a wide range utterly irrelevant to stray capacity with a simple method. CONSTITUTION:An output of a zero phase current transformer ZCT is applied to a buffer BA via a low pass filter F and the output ig of the buffer is the sum of the current iR flowing through an insulation resistance and the current iC flowing through a stray capacity C, where iR<<iC. An output of an oscillator OSC, V=V0 sinomega0t undergoes a 90 deg. phase shifter PS and an inversion circuit INV to obtain an output current i=-acosomega0t. The outputs ig and i are added with an adder ADD, the output of which is applied to one input end of a multiplier MULT1. The output V2cosomega0t of the preceding phase shifter PS is applied to the other input end of the multiplier MULT1. Therefore, the output of the MULT1 provides a signal as represented by (ig+i)V2cosomega0t which is applied to an LPF1 to obtain the DC component (omega0CV0-a)V2/2. A VR is adjusted to render the output zero and a multiplier MULT2 extracts the DC component with an LPF2. Thus, V0V2R is obtained at the output thereof as a value reversely proportional to the insulation resitance.

Description

【発明の詳細な説明】 精密に辿ｌ定する方法に関する。[Detailed description of the invention] It relates to a method of precisely tracing.

活線状態にある電路の絶縁状＃を測定する場合には通常
は零相質流器（以下Ｚ　Ｃ　Ｔと略称する）を使用して
漏洩電流を検出しているがこの漏洩電流には漏洩抵抗（
以下絶縁孤抗と呼称する）による成分の他に対地静電５
容−Ｊｉｌｏ（以下浮遊容量と呼称する）によって流れ
る成分も含まれる。一般に浮遊ｓ量による電流は絶縁抵
抗のそれにくらべて著しく犬なるため絶縁抵抗の測定誤
差が犬となる。これらの電流は負荷の有無によっても変
動する。また活線回路のオンライン監視等においては測
定系のその都度の調整が本来できない性質をもつため測
定系には無調整化が要求される。しかも絶縁劣化に伴っ
て生ずる広範囲にわたる絶縁抵抗の変動値全正確で、安
定に測定することを必要とする。When measuring the insulation level of a live electrical circuit, a zero-phase current detector (hereinafter abbreviated as ZCT) is normally used to detect leakage current. resistance(
In addition to the component due to insulation resistance (hereinafter referred to as insulation resistance), ground static electricity 5
Also included is a component flowing due to capacitance (hereinafter referred to as stray capacitance). In general, the current due to the amount of stray s is significantly larger than that of insulation resistance, so the measurement error of insulation resistance becomes larger. These currents also vary depending on the presence or absence of a load. Furthermore, in online monitoring of live circuits, etc., the measurement system cannot be adjusted on a case-by-case basis, so the measurement system is required to be non-adjustable. Moreover, it is necessary to accurately and stably measure all fluctuations in insulation resistance over a wide range that occur due to insulation deterioration.

本発明は浮遊容量に全く関係なく、活線状態で広範囲に
わたって絶縁担抗の測定を可能にする有用な装置に関す
る。The present invention relates to a useful device which allows measurements of insulation charge over a wide range under live line conditions, completely independent of stray capacitance.

以下図面を参照しながら本発明の詳細な説明する。The present invention will be described in detail below with reference to the drawings.

第１図は本発明の実施例であって接地線に零相変流器Ｚ
ＣＴ　１（貫通させると共に周波数ｆ。Figure 1 shows an embodiment of the present invention, in which a zero-phase current transformer Z is connected to the ground wire.
CT 1 (throughput and frequency f.

宮バ周波を発振する発振器０８Ｃに接続されたトランス
Ｔもしくは低周波ｆｏｋ発振する発振トランスのコアｆ
貫通させる。電路に印加された周波数ｆｏの電圧ｉＶと
すれば、零相変流器ＺＣＴの出力には商用周波成分と印
加した低周波電圧成分による漏洩電流が検出される。零
相変流器出力を印加した低周波電圧のみ全選択するフィ
ルタＦに印加すれば、その出力１ｇには絶縁担抗Ｒｉ介
して流れる電流ｊＨと浮遊容ｉ−Ｃを介して流れる電流
ｉｃとが含まれる。を路に印加された低周波電圧■（電
路と天地間の電圧）　ｋ　Ｖ−Ｖｏｓｉｎωｏ　ｔ　（
ωｏ＝２　ｙｒ　ｆ　ｏ　）　　とおくことにより　Ｉ
ｇは ｉｇ＝＊Ｒ＋ｉｃ となる。この電流は零相変流器出刃をフィルタＦに加え
ることにより得られ、このＩｇはバッファアンプＢＡに
て増幅される。A transformer T connected to the oscillator 08C that oscillates high frequency waves or a core f of an oscillation transformer that oscillates low frequency fok.
Penetrate. Assuming that the voltage iV at the frequency fo applied to the electric path is, a leakage current due to the commercial frequency component and the applied low frequency voltage component is detected in the output of the zero-phase current transformer ZCT. If the zero-phase current transformer output is applied to a filter F that selects only the applied low-frequency voltage, its output 1g will have a current jH flowing through the insulator Ri, a current ic flowing through the stray capacitance i-C, and is included. The low-frequency voltage ■ applied to the circuit (voltage between the circuit and the ground) k V−Vosinωot (
By setting ωo=2 yr f o ), I
g becomes ig=*R+ic. This current is obtained by adding a zero-phase current transformer to the filter F, and this Ig is amplified by the buffer amplifier BA.

ところでｉｎ（０式の第１項）と　ｉｃ（０式の第２項
）の大きさを比較すると一般にｊＨはｉｃよりもはるか
に小さい値である。このため（１１式の第２項が小さく
ないときは目的とする第１項に比例する値を同期検波等
で検出する際に誤差を発生する可能性がある。By the way, when comparing the magnitudes of in (first term of equation 0) and ic (second term of equation 0), jH is generally a much smaller value than ic. For this reason, if the second term in equation 11 is not small, an error may occur when detecting a value proportional to the target first term using synchronous detection or the like.

本発明の装置はこの問題を次の如く解決する。The device of the invention solves this problem as follows.

すなわち上記電路印加電圧■を９ｏ°゛移相器に通すこ
とにより得られる電圧Ｖ２ＣＯ８ωｏｔｋ極性反転する
ことにより振幅ａの電流ｉ　−−Ｂ　ｃｏｓωｏｔ　な
る補正信号１に得る。これヲ（１）式のＩｇに加算すれ
は 凰ｇ　＋ｔと上記ｖ２ｃｏｓωｏｔ　　との「積」をと
れば（ｒ　ｇ　＋　ｉ　）　ｘ　Ｖ　２ＣＯ８ωｏｔと
なる。（３１式の右辺の直流分 に注目するとこれはωｏＣＶｏ＝＝ａ　　のとき零とな
る。That is, by inverting the polarity of the voltage V2CO8ωotk obtained by passing the voltage applied to the electric circuit through a 9° phase shifter, a correction signal 1 is obtained, which is a current i --B cosωot with an amplitude a. Adding this to Ig in equation (1), the "product" of g +t and the above v2cosωot becomes (r g + i ) x V 2CO8ωot. (If we pay attention to the DC component on the right side of Equation 31, it becomes zero when ωoCVo==a.

そしてその時（２１式の第２項は零となる。すなわち上
記の積（ｉｇ十１）Ｘｖ２ωＳωｏｔの直流分が零とこ
とになる。At that time, the second term of equation (21) becomes zero. That is, the DC component of the above product (ig11)Xv2ωSωot becomes zero.

第１図の実施例においてフィルタＦの出力はバッファア
ンプＢＡに加えられて（１）式のＩｇが得られる。一方
、低周波電圧発振器Ｏ８Ｃの出力から電、圧Ｖ２ｓｉｎ
ωｏｔが得られる。発振器Ｏ８Ｃの出力は９０度移相器
Ｐｓに加えられて９０度位相をシフトされ■２ｃｏＳω
ｏｔが得られる。それは更に極性反転回路ＩＮＶに入力
されてその出力には−Ｖ２ｃｏＳωｏｔが得られ１．Ｔ
ＮＶの出方は可変減衰器に加えられその出力にはｉ　−
−Ｂ　ｃｏｓωｏｔの１１２流が得られる。加算器ＡＤ
Ｄによりｉｇと１が得られる０このＡＤＤ出力はかけ算
器ＭＵＬ　Ｔ１の一方の入力端に加えられ、先の移相器
ｐｓの出力Ｖ　２ＣＯ８ωａｔがかけ算器ＭＵＬＴ１の
他の入力端に加えられる。したがってＭＵＬ’ｌｌ’ｌ
の出力には（３）式で表わされる信号が得られる。この
ＭＵＬＴＩ　　の出力はローパスフィルタＬＰＦ’ｌに
加えることにより直流分 器ＡＰで増幅され可変減衰器ＶＲを制御しＬ　Ｐ　Ｐｌ
ｌの出力が零となるように作用するものである。In the embodiment of FIG. 1, the output of filter F is applied to buffer amplifier BA to obtain Ig of equation (1). On the other hand, the voltage V2sin is generated from the output of the low frequency voltage oscillator O8C.
ωot is obtained. The output of the oscillator O8C is applied to a 90 degree phase shifter Ps and the phase is shifted by 90 degrees.■2coSω
ot is obtained. It is further input to the polarity inversion circuit INV, and -V2coSωot is obtained at its output. T
The output of NV is added to a variable attenuator, and the output is i −
112 streams of −B cosωot are obtained. Adder AD
D gives ig and 1.0 This ADD output is applied to one input of the multiplier MULT1, and the output V2CO8ωat of the previous phase shifter ps is applied to the other input of the multiplier MULT1. Therefore MUL'll'l
A signal expressed by equation (3) is obtained at the output. The output of this MULTI is applied to the low-pass filter LPF'l, is amplified by the DC divider AP, controls the variable attenuator VR, and is L P Pl
It acts so that the output of l becomes zero.

この種の技術は自動利得制御回路等で当業者には慣用さ
れている技術である。かくして上記ＬＰＦＩ出力の直流
分が零に近づくことは加算器Ａ　Ｉ）　Ｄの出方に含ま
れる無効成分即ち（２）式の第２項は零に近づくことに
なる。したがって加算器ＡＤＩ）（７）出力と発振器Ｏ
８Ｃの出力Ｖ２ｓｉｎωｏｔとの積をかけ算器ＭＵＬＴ
２でとりその直流分をローパスフィルタＬＰＦ２でとる
ことによりＬＰＦに逆比例した量となる。なおこの自動
調整ではＡ　Ｄ　Ｉ）出力にはｉ（Ｈによる成分は含ま
れなくなるからＡ　Ｉ）　Ｄの出力を整流しても同様な
結果を得ることができる。また（３）式からも明らかな
ようにかけ算器ＭＵＬＴＩの出力全バイパスフィルこれ
全整流しても同様な結果を得る。This type of technique is commonly used by those skilled in the art in automatic gain control circuits and the like. Thus, when the DC component of the LPFI output approaches zero, the reactive component included in the output of the adder AI), ie, the second term in equation (2), approaches zero. Therefore adder ADI) (7) output and oscillator O
Multiplier MULT multiplier with 8C output V2sinωot
2 and its DC component is taken by the low-pass filter LPF2, resulting in an amount inversely proportional to the LPF. Note that in this automatic adjustment, the component due to i(H) is no longer included in the ADI) output, so a similar result can be obtained even if the output of AID is rectified. Furthermore, as is clear from equation (3), a similar result is obtained even if the output of the multiplier MULTI is completely bypassed and completely rectified.

さらに（３）式においてａ　＝　Ｏとすればすなわち１
＝０としたとき Ｉｇｘｖ２ｃｏｓωｏｔ となり、浮遊容量を活線状態で測定することができる。Furthermore, if a = O in equation (3), then 1
When Igxv2cosωot is set to 0, stray capacitance can be measured in a live line state.

上記説明では単相２線式の場合について説明したが本発
明では２次１端接地の単相３線、３相３線等の回路の場
合でも同様に適用できる。In the above explanation, the case of a single-phase two-wire type was explained, but the present invention can be similarly applied to a single-phase three-wire circuit, a three-phase three-wire type, etc., in which the secondary end is grounded.

なお実施例では電路への低周波印加用のトランスならひ
に零相変流器を接地線を共に貫通するごとくしたが、電
１路へ両名又は一方を貫通させてもよい。また接地線全
切断してこれに直列に低周波電圧を印加してもよい。簡
単な方法で電路の絶縁抵抗の精密な測定を可能にする本
発明の工業的価値は高い。In the embodiment, the transformer for applying low frequency to the electric line is made to pass through both the zero-phase current transformer and the grounding wire, but it is also possible to make both or one of them pass through the electric line. Alternatively, the grounding wire may be completely cut off and a low frequency voltage may be applied in series thereto. The industrial value of the present invention, which enables accurate measurement of the insulation resistance of an electric circuit by a simple method, is high.

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

第１図は本発明の絶縁狐抗測ボ装置の実施例を示す。 ＺＣ’ｌ’・・・・・・零相質流器　　Ｔ・・・・・・
　トランスＯ８Ｃ・・・・・・低周波発揚器　ＢＡ・・
・・・バッファアンプＭＵＬＴＩ　、　ＭＵＬ’ｌ’２
・・・・・・がけ算器ＺＬ・・・・・・　負荷　　　　
　Ｃ・・・・・・浮遊容量Ｒ・・・・・・絶縁抵抗　　
　　ｐｓ・・・・・・９０度移相器ＩＮＶ・・・・・・
極性反転回路　ＶＲ・・・・・・可変減衰器ＡＤＤ・・
・・・・加算器 ＬＰｋ’１．ＬＰＦ２・・・・・・　ローパスフィルタ
ＡＰ・・・・・・　増幅器 特許出願人　　東洋通信機株式会社FIG. 1 shows an embodiment of the insulated fox resistance measuring device of the present invention. ZC'l'・・・Zero phase flow vessel T・・・・・・
Transformer O8C...Low frequency generator BA...
...Buffer amplifier MULTI, MUL'l'2
... Multiplication calculator ZL ... Load
C... Stray capacitance R... Insulation resistance
ps...90 degree phase shifter INV...
Polarity reversal circuit VR...Variable attenuator ADD...
...Adder LPk'1. LPF2・・・・・・ Low pass filter AP・・・・・・ Amplifier patent applicant Toyo Tsushinki Co., Ltd.

Claims (1)

【特許請求の範囲】[Claims] 活線状態にある電路の接地線を通じて電路に画定信号で
ある低周波電圧を電ａ誘導によりまたは直列結合によっ
て印加し、該接地線に帰還する漏洩電流を零相変流器で
検出し、該零相変流器の出力に含まれる該低周波成分中
の絶縁抵抗による有効成分を検出することにより該電路
の絶縁抵抗を測定する装置において、「該零相変流器出
力中の該低周波成分の電流」と「該印加低周波電圧とは
位相が９０°異なる第１の電流」との「差の信号」を得
る手段と、該「差の信号」と「該印加低周波電圧とは位
相が９０°異なる第２の電圧」との「槓の直流分」が零
となるように「該第１の電流」の大きさ全自動調整する
手段を設け、該「差の信号」に含まれる浮遊容量による
電流成分を零にすることにより漏洩電流中の絶縁抵抗に
よる有効成分全精密に迎；定したことを特徴とする絶縁
抵抗測定装置１．A low-frequency voltage, which is a demarcation signal, is applied to the electrical circuit through the grounding wire of the live electrical circuit by electric induction or by series coupling, and the leakage current that returns to the grounding wire is detected by a zero-phase current transformer. In a device that measures the insulation resistance of the electrical circuit by detecting the effective component due to insulation resistance in the low frequency component contained in the output of the zero phase current transformer, means for obtaining a "difference signal" between a component current and a first current having a phase different by 90 degrees from the applied low-frequency voltage; A means is provided to fully automatically adjust the magnitude of "the first current" so that "the direct current component" with respect to the "second voltage having a phase difference of 90 degrees" is zero, and the "first current" is included in the "difference signal". 1. Insulation resistance measuring device characterized in that the effective component of insulation resistance in leakage current can be precisely determined by reducing the current component due to stray capacitance to zero.