JP4121979B2 - Non-grounded circuit insulation monitoring method and apparatus - Google Patents
Non-grounded circuit insulation monitoring method and apparatus Download PDFInfo
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Description
本発明は、接地用変圧器接地電路や中性点抵抗接地電路のように接地線に中性点抵抗を有する非接地電路の絶縁状態を常時監視する監視方法及び監視装置に関する。 The present invention relates to a monitoring method and a monitoring device for constantly monitoring the insulation state of a non-grounded circuit having a neutral point resistance on a grounding line such as a grounding transformer grounding circuit or a neutral point resistance grounding circuit.
接地用変圧器(EVT、GVT)接地電路又は中性点抵抗接地電路において、電路の絶縁状態を監視し、絶縁劣化が生じたときは事前に対策を講じて事故の発生を予防したり、地絡事故が発生したときは速やかにそれを検出して保護動作を行い停電の拡大を防止することが行はれている。 In the earthing transformer (EVT, GVT) earthing circuit or neutral resistance earthing circuit, the insulation state of the circuit is monitored, and when insulation deterioration occurs, measures are taken in advance to prevent the occurrence of accidents, When a tie-up accident occurs, it is promptly detected and a protective action is performed to prevent the spread of power outages.
従来、電路の絶縁状態を調べるには、定期点検時にメガリングによって電路の絶縁抵抗を測定する方法が取られている。しかし、このメガリングにより測定する場合は、電路の電源を切り一旦停電した状態で測定する必要があり常時の監視はできない。 Conventionally, in order to check the insulation state of an electric circuit, a method of measuring the insulation resistance of the electric circuit by a mega ring at a regular inspection is taken. However, when measuring by this mega ring, it is necessary to make a measurement in a state where the power of the electric circuit is turned off and the power is temporarily cut off.
近年はこの停電をすることなく活線状態で絶縁状態を調べる方法が要望され、いろいろ提案されている。その一例として、前もって保護範囲の静電容量を計測、あるいは対地静電容量、電力ケーブルの断面積、亘長などから静電容量を机上計算により求めておき、事故時に発生する零相電圧で負荷側対地静電容量に流れる電流を演算し、零相変流器に流れる電流から、この電流を加算あるいは差し引く演算処理により事故点電流を求めるようにしたものがある(例えば、特許文献1等)。
この方法は、電路の負荷変動や、負荷電路の遮断等により対地静電容量が変動した場合の対応が難しく、又電路の経年変化等によるデータを定期的に収集して補正する必要がある。 In this method, it is difficult to cope with a change in the ground capacitance due to load fluctuation of the electric circuit or interruption of the load electric circuit, and it is necessary to periodically collect and correct data due to aging of the electric circuit.
又、系統定数に影響されない絶縁抵抗値による電路の絶縁状態を診断する方法も提案されている。それは、例えば、非接地式高圧配電系統に配置するGVT(接地用変圧器)から商用周波数とは異なる低周波数の重畳信号を注入し、この重畳信号を検出CTと重畳電圧検出装置で検出し、制御装置であらかじいめ設定してあるプログラムにしたがって重畳電圧検出器の位相差および重畳電流成分の実効値に応じて重畳電流成分の比誤差及び位相誤差の補正を行った情報をCPUにより処理し、ベクトル合成により対地間抵抗成分を分離し、そのデータを監視または出力するようにしている(例えば、特許文献2等)。
この方法は、あらかじめ設定したプログラムにしたがって重畳電圧検出の位相差および重畳電流成分の実効値に応じて重畳電流検出の比誤差及び位相誤差を補正する必要がある。又、重畳信号発信器やその信号を重畳させるための結合装置及び重畳信号を取り出すための重畳電圧検出装置が必要となる。特に高圧電路の場合は、これらの装置は絶縁の関係から形状が大きくなり、且つ高価なものとなる。 In this method, it is necessary to correct the superimposed error detection ratio error and the phase error according to the phase difference of the superimposed voltage detection and the effective value of the superimposed current component according to a preset program. In addition, a superposition signal transmitter, a coupling device for superimposing the signal, and a superposition voltage detection device for extracting the superposition signal are required. Particularly in the case of high piezoelectric paths, these devices are large in shape and expensive due to insulation.
そして、重畳信号で絶縁状態を調べる方法は、負荷機器に悪影響を与えないようにするため、重畳する信号を極力小さくする必要があり、検出信号に含まれる系統周波数信号を除去するためのフィルタを強化せざるを得ない。そのため計測時間が比較的長くなり、高速での動作が要求される継電装置としての機能を持たせることが難しく、絶縁監視のみの機能となってしまう、という課題がある。 The method of checking the insulation state with the superimposed signal needs to reduce the superimposed signal as much as possible so as not to adversely affect the load device, and a filter for removing the system frequency signal included in the detection signal is required. It must be strengthened. Therefore, there is a problem that the measurement time becomes relatively long, it is difficult to provide a function as a relay device that requires high-speed operation, and the function is only for insulation monitoring.
以上の点に鑑み、本発明は、活線状態で電路の絶縁状態を監視するものであるが、従来のように保護範囲の静電容量を前もって計測又は計算したり、又は商用周波数と異なる低周波の信号を重畳しこれを検出するのではなく、通常使用されている零相変流器と零相変圧器を用いることが出来るようにし、これに相電圧検出手段を追加するのみで電路の絶縁抵抗及び絶縁劣化時に流れる電流、地絡電流をも検出できるようにした絶縁状態監視方法および監視装置を提供することを目的とする。 In view of the above points, the present invention monitors the insulation state of the electric circuit in a live line state, but measures or calculates the capacitance of the protection range in advance as in the prior art, or is different from the commercial frequency. Instead of superimposing the frequency signal and detecting it, it is possible to use a normally used zero-phase current transformer and zero-phase transformer, and only by adding phase voltage detection means to this, It is an object of the present invention to provide an insulation state monitoring method and a monitoring apparatus that can detect an insulation resistance, a current that flows during insulation deterioration, and a ground fault current.
本発明において上記の課題を解決するための手段は、零相電流、零相電圧及び各充電相の相電圧から、絶縁劣化抵抗ならびに、この絶縁劣化抵抗を流れる電流を求め、非接地電路の絶縁状態を監視するようにするものである。 Means for solving the above problems in the present invention is to obtain an insulation deterioration resistance and a current flowing through the insulation deterioration resistance from the zero phase current, the zero phase voltage and the phase voltage of each charging phase, and to insulate the non-grounded circuit. It is intended to monitor the state.
通常、電力供給会社や特高受電した需要家の変電所には、接地用変圧器(GVT又はEVT)が設けられており、又低圧400V電路の場合には、EVT非接地とする場合が多く、従って、電源側中性点抵抗が存在し、絶縁劣化により生じる零相電圧と絶縁劣化時の絶縁劣化している相の大地間電圧の位相差及び零相電圧と零相電流との位相差は常に90度以上の位相となるため、絶縁劣化抵抗に流れる電流を算出することができることに着目して本発明が成されたもので、従来零相変流器で検出した零相電流で判断していたものを、事故点に流れる電流及び事故点抵抗を検出し、これにより非接地電路の絶縁を監視するようにしたことを特徴とするものである。以下、本発明の基本となる思想を図1によって説明する。 Usually, transformers for grounding (GVT or EVT) are installed in substations of power supply companies and customers receiving extra high voltage, and in the case of a low-voltage 400 V circuit, EVT is often ungrounded. Therefore, there is a neutral point resistance on the power source side, and the phase difference between the zero-phase voltage caused by insulation deterioration and the ground-to-ground voltage of the phase in which insulation is deteriorated at the time of insulation deterioration, and the phase difference between zero-phase voltage and zero-phase current The present invention has been made by paying attention to the fact that the current flowing through the insulation deterioration resistance can be calculated because the phase always has a phase of 90 degrees or more, and is determined by the zero-phase current detected by the conventional zero-phase current transformer. The current flowing through the fault point and the fault point resistance are detected, and the insulation of the ungrounded electric circuit is thereby monitored. The basic idea of the present invention will be described below with reference to FIG.
図1は接地用変圧器による非接地電路に於ける絶縁劣化又は地絡検出の説明図、図2は中性点抵抗接地電路に於ける絶縁劣化又は地絡事故検出の説明図である。 FIG. 1 is an explanatory diagram of insulation deterioration or ground fault detection in a non-grounded electric circuit by a grounding transformer, and FIG. 2 is an explanatory diagram of insulation deterioration or ground fault detection in a neutral resistance ground circuit.
尚、中性点抵抗接地電路は、接地用変圧器による非接地電路と等価回路は同じとなるため、接地用変圧器接地電路で説明し、また、接地用変圧器には容量によりGVT又はEVTと称されているが、回路的には等価であるので説明の簡略化のため以下、EVTと総称して説明する。 Since the equivalent circuit of the neutral point resistance grounding circuit is the same as the non-grounding circuit by the grounding transformer, the grounding transformer grounding circuit will be described, and the grounding transformer has GVT or EVT depending on the capacity. However, since they are equivalent in terms of circuit, for the sake of simplification of description, hereinafter, they will be collectively referred to as EVT.
図1において、1は一次側がスター結線、二次側がデルター結線された電源変圧器、2は被監視電路、3は零相電流検出手段としての零相変流器、4はEVT(接地用変圧器)を示し、該EVTは一次回路が被監視電路に接続されたスター結線の一次回路41と、デルター結線の二次回路(図示省略)と、三次回路43(ブロークンデルタ回路)、から成り、一次回路の中性点は接地線44で接地され、三次回路43には制限抵抗Ro(一次換算した中性点抵抗)が設けられている。
In FIG. 1, 1 is a power transformer in which the primary side is star-connected and the secondary side is delta-connected, 2 is a monitored circuit, 3 is a zero-phase current transformer as zero-phase current detecting means, and 4 is an EVT (grounding transformer). The EVT includes a
なお、図中C0は電源側対地静電容量、CLは負荷側対地静電容量を示している。 In the figure, C0 represents the power-side ground capacitance, and CL represents the load-side ground capacitance.
この図1の回路を等価回路に書き換えると図3のようになる。図4は、図1のG点で絶縁劣化が発生したときの各電圧及び電流のベクトル図を示し、その(A図)は全体,(B)図はA図の点線の丸で囲んだ部分の拡大図を示している。 When the circuit of FIG. 1 is rewritten to an equivalent circuit, it becomes as shown in FIG. 4 shows a vector diagram of each voltage and current when insulation deterioration occurs at point G in FIG. 1. FIG. 4A is a whole, and FIG. 4B is a portion surrounded by a dotted circle in FIG. FIG.
今、図1の零相変流器3より負荷側のG点で絶縁劣化が発生すると、図3及び図4に示すように、EVT4の接地線44に流れる電流Ir0は三次回路43の中性点抵抗Roに流れる電流であるため、零相電圧V0と同位相となるが、零相電圧V0を対地電圧E点から電路の中性点N点を見ている関係で、零相変流器3から見たとき逆位相となり、零相電圧V0に対し180°の位相となる。
If the insulation deterioration occurs at point G on the load side of the zero-phase
電源側対地静電容量C0に流れる電流Ic0は、零相電圧V0により流れる静電容量分電流であるため、零相電圧V0に対し90°進みであるが、零相変流器3から見たとき逆位相となり遅れ90°となる。負荷側対地静電容量CLに流れる電流IcLは、零相変流器3を一旦流れるが、負荷側対地静電容量CLを通して零相変流器3を帰還し、静電容量CLに流れる電流IcLは相殺される。
The current Ic0 that flows through the power supply side ground capacitance C0 is a current corresponding to the capacitance that flows due to the zero-phase voltage V0, and therefore is 90 ° ahead of the zero-phase voltage V0, but is viewed from the zero-phase
絶縁劣化点G点に流れる電流Igは、接地線44に流れる電流Ir0と電源側対地静電容量C0に流れる電流Ic0及び負荷側対地静電容量CLに流れる電流IcLとのベクトル和で
The current Ig flowing through the insulation deterioration point G is a vector sum of the current Ir0 flowing through the
となる。 It becomes.
絶縁劣化時の地絡相電圧Vg(地絡相−大地間電圧)は、絶縁劣化抵抗RgとこのRgに流れる電流Igの積となるから、位相はこの電流Igと同相となる。 Since the ground fault phase voltage Vg (ground fault phase-ground voltage) at the time of insulation deterioration is the product of the insulation deterioration resistance Rg and the current Ig flowing through the Rg, the phase is in phase with the current Ig.
絶縁劣化により生じる零相電圧Voと地絡相電圧Vgの位相差θは、中性点抵抗Roが無限大のとき接地線44に流れる電流Ir0が零で90°に、電源側対地静電容量C0が零のとき、この静電容量C0に流れる電流Ic0が零で180°となる。
The phase difference θ between the zero-phase voltage Vo and the ground-fault phase voltage Vg caused by the insulation deterioration is 90 ° when the current Ir0 flowing through the
従って、EVT4の中性点抵抗R0が無限大でなければ90°<θ≦180°となる。 Therefore, if the neutral point resistance R0 of the EVT 4 is not infinite, 90 ° <θ ≦ 180 °.
零相変流器3で検出される零相電流I0には、負荷側対地静電容量CLに流れる電流IcLは相殺されるため、零相変流器3で検出される零相電流I0は次式のように接地線44に流れる電流Ir0と電源側対地静電容量C0に流れる電流Ic0の和となる。
Since the current IcL flowing through the load side ground capacitance CL is canceled out by the zero phase current I0 detected by the zero
そして、図4の零相電流I0のように接地線44に流れる電流Ir0と絶縁劣化抵抗Rgに流れる電流Igの間の位相に存在することになる。
4 exists in a phase between the current Ir0 flowing through the
これらの関係から、中性点抵抗R0が無限大でなく90°<<θの条件であるとき零相電圧V0,零相電流I0,地絡相電圧Vgの絶対値及び位相が計測されれば、下記の演算により接地線に流れる電流Ir0,絶縁劣化抵抗に流れる電流Igが次のように求められる。 From these relationships, if the neutral point resistance R0 is not infinite but 90 ° << θ, the absolute value and phase of the zero-phase voltage V0, the zero-phase current I0, and the ground fault phase voltage Vg are measured. The current Ir0 flowing through the ground line and the current Ig flowing through the insulation deterioration resistance are obtained as follows by the following calculation.
Ir0=I0×Cos(180°−φ)……(3)
Ig=Ir0÷Cos(180°−θ)……(4)
但し、φは零相電圧V0と零相電流I0の位相差,θは零相電圧V0と地絡相電圧Vgの位相差とする。
Ir0 = I0 × Cos (180 ° −φ) (3)
Ig = Ir0 ÷ Cos (180 ° −θ) (4)
Where φ is the phase difference between the zero-phase voltage V0 and the zero-phase current I0, and θ is the phase difference between the zero-phase voltage V0 and the ground fault phase voltage Vg.
更に、地絡相電圧Vgと絶縁劣化抵抗に流れる電流Igから、絶縁劣化抵抗Rgが次式で求められる。 Further, the insulation deterioration resistance Rg is obtained from the ground fault phase voltage Vg and the current Ig flowing through the insulation deterioration resistance by the following equation.
Rg=Vg÷Ig……(5)
又、地絡相がどの相かの判断は、絶縁劣化時の各相電圧が零相電圧V0に対して遅れ90°〜180°の範囲にあるか否かで判断し、範囲内にある相を絶縁劣化相と判断する。
Rg = Vg ÷ Ig (5)
The phase of the ground fault phase is determined by whether each phase voltage at the time of insulation deterioration is within a range of 90 ° to 180 ° with respect to the zero phase voltage V0. Is judged as an insulation deterioration phase.
なお、相電圧の検出は、各相の電圧を検出するか、又は任意の一相の相電圧と零相電圧から、本来の相電圧(絶縁劣化のない状態の相電圧)を演算手段でベクトル演算して求め、更に残りの他相の本来の相電圧は120°づつの位相差を持たせることで求め、更に、絶縁劣化時の他相の相電圧を求めるようにしても良い。 The phase voltage can be detected by detecting the voltage of each phase or by calculating the original phase voltage (phase voltage without insulation deterioration) from any one-phase voltage and zero-phase voltage using a calculation means. It may be obtained by calculation, and the original phase voltage of the remaining other phase may be obtained by giving a phase difference of 120 °, and the phase voltage of the other phase at the time of insulation deterioration may be obtained.
以上のように、中性点抵抗R0が無限大でなく、零相電圧V0と地絡相電圧Vgの位相差θが90°<<θの条件にある時、零相電圧V0、零相電流I0及び地絡相電圧Vgの絶対値及び位相を計測することにより、絶縁劣化抵抗Rg及びこの抵抗Rgに流れる電流Igが求められるので、この抵抗値Rg及び/又は電流値Igをデスプレー等に表示することで被監視電路の絶縁状態を常時監視することができる。 As described above, when the neutral point resistance R0 is not infinite and the phase difference θ between the zero-phase voltage V0 and the ground fault voltage Vg is 90 ° << θ, the zero-phase voltage V0, the zero-phase current By measuring the absolute value and phase of I0 and the ground fault phase voltage Vg, the insulation degradation resistance Rg and the current Ig flowing through the resistance Rg can be obtained, so that the resistance value Rg and / or the current value Ig is displayed on a display or the like. By doing so, the insulation state of the monitored electric circuit can be constantly monitored.
また、絶縁劣化抵抗に流れる電流Igの検出閾値を設け、閾値を超えた時警報及び/又は接点を出力させて故障電路を遮断する等の保護動作をおこなわせることで地絡検出保護ができる。 Further, a ground fault detection protection can be performed by providing a detection threshold value for the current Ig flowing through the insulation deterioration resistance and performing a protection operation such as outputting an alarm and / or a contact when the threshold value is exceeded to shut off the fault circuit.
上記の説明は、零相変流器が被監視電路に設けられている場合であるが、この零相変流器を接地線に設けると、零相変流器から見て被監視電路全てが負荷側となり、電路全体の絶縁劣化状態の監視ができる。この場合は、接地線に流れる電流Ir0を直接計測できることになるので、零相変流器で検出された零相電流I0は接地線に流れる電流Ir0と等しいから、その絶対値を零相電圧V0の位相と地絡相電圧Vgの位相差θから絶縁劣化抵抗Rgに流れる電流Igは上記の(4)式のIr0をI0とすることで求められ、絶縁劣化抵抗Rgは(5)式で求めることができる。 The above explanation is a case where a zero-phase current transformer is provided in the monitored circuit. However, if this zero-phase current transformer is provided in the ground line, all the monitored circuits are viewed from the zero-phase current transformer. It becomes the load side and can monitor the insulation deterioration state of the whole electric circuit. In this case, since the current Ir0 flowing through the ground line can be directly measured, the zero-phase current I0 detected by the zero-phase current transformer is equal to the current Ir0 flowing through the ground line. The current Ig flowing in the insulation deterioration resistance Rg from the phase difference θ between the phase of the ground and the ground fault voltage Vg is obtained by setting Ir0 in the above equation (4) to I0, and the insulation deterioration resistance Rg is obtained by the equation (5). be able to.
また、EVT接地系電路においては、EVTの接地線から零相電流を検出し、相間電圧の検出はEVTの二次回路から、零相電圧はEVTの三次回路から検出し、EVTの二次回路の各線間電圧値を相電圧値に換算し30°遅らせた位相として各相電圧を得、あるいは任意の一相の線間電圧を相電圧に換算して30°遅らせた位相とし、その他の相電圧は三相三線の場合、120°づつ位相がずれているので演算により各相電圧を求め、更に、零相電圧V0とベクトル演算することにより、絶縁劣化時の各相電圧を得、この絶縁劣化時の各相電圧と零相電圧V0の各値から絶縁劣化相又は地絡相がどの相かを判別し、地絡相電圧Vgの値及び位相を求めることができる。そして前述同様に接地線から検出した零相電流I0は接地線に流れる電流Ir0に等しいから、その絶対値を零相電圧V0の位相と地絡相電圧Vgの位相差θから絶縁劣化抵抗に流れる電流Igを前記の(4)式のIr0をI0とすることにより求めることができる。 In the EVT ground system circuit, the zero-phase current is detected from the EVT ground line, the interphase voltage is detected from the EVT secondary circuit, the zero-phase voltage is detected from the EVT tertiary circuit, and the EVT secondary circuit is detected. Each line voltage is converted into a phase voltage value and each phase voltage is obtained as a phase delayed by 30 °, or any one phase line voltage is converted into a phase voltage and a phase delayed by 30 °, and the other phases In the case of a three-phase three-wire voltage, the phase is shifted by 120 °, so each phase voltage is obtained by calculation. Further, by calculating a vector with zero phase voltage V0, each phase voltage at the time of insulation deterioration is obtained. It is possible to determine which phase is the insulation deterioration phase or the ground fault phase from each value of the phase voltage and the zero phase voltage V0 at the time of deterioration, and obtain the value and phase of the ground fault phase voltage Vg. Since the zero-phase current I0 detected from the ground line is equal to the current Ir0 flowing through the ground line as described above, its absolute value flows from the phase difference θ between the zero-phase voltage V0 and the ground fault voltage Vg to the insulation deterioration resistance. The current Ig can be obtained by setting Ir0 in the above equation (4) to I0.
本発明は上記のように、通常の検出手段で計測可能な零相電圧、零相電流及び地絡相電圧によって絶縁劣化抵抗値及びこの絶縁劣化抵抗に流れる電流値を求めることができるので、下記のような効果を奏する。 As described above, the present invention can determine the insulation deterioration resistance value and the current value flowing through the insulation deterioration resistance by the zero phase voltage, the zero phase current and the ground fault phase voltage which can be measured by the normal detection means. There are effects like this.
(1)停電を必要とせずに活線状態で被監視電路の絶縁状態を常時監視できる。 (1) The insulation state of the monitored circuit can be constantly monitored in a live line state without requiring a power failure.
(2)零相電流検出手段、零相電圧検出手段は、方向性地絡継電器などに通常使用されている零相変流器や零相電圧検出装置と同等のものでよく、又、相電圧の検出は零相電圧と本来の相電圧からベクトル演算により求めるか、又は相電圧検出手段を追加するだけでよく、特別な装置を必要としない。 (2) Zero-phase current detection means and zero-phase voltage detection means may be equivalent to zero-phase current transformers and zero-phase voltage detection devices normally used for directional ground fault relays, etc. Is detected by vector calculation from the zero-phase voltage and the original phase voltage, or only a phase voltage detecting means is added, and no special device is required.
(3)EVT接地電路に於いては、地絡相電圧はEVTの二次回路と三次回路から演算により求めることができので、相電圧検出手段を不要とする事ができる。 (3) In the EVT ground circuit, the ground fault phase voltage can be obtained by calculation from the secondary circuit and tertiary circuit of the EVT, so that the phase voltage detecting means can be dispensed with.
(4)各分岐に複数台取り付ける事により絶縁劣化箇所の特定が可能となる。 (4) By attaching a plurality of units to each branch, it is possible to identify the location of insulation deterioration.
(5)接地線に流れる零相電流を検出することにより、被監視電路全体の絶縁劣化を監視することができる。 (5) By detecting the zero-phase current flowing in the ground line, it is possible to monitor the insulation deterioration of the entire monitored electric circuit.
(6)負荷側の静電容量が変動してもこれに影響されること無く常に正確な絶縁監視ができる。 (6) Even if the capacitance on the load side fluctuates, accurate insulation monitoring can always be performed without being affected by this.
以下、本発明の実施の形態を図面によって説明する。 Embodiments of the present invention will be described below with reference to the drawings.
図5及び図6は本発明の第一の実施の形態の説明図で、図5は全体の構成図、図6は絶縁監視手段の内部構成図を示している。なお、これらの図において、図1と同じか又は相当部分にはこれと同じ符号を付して説明を省略する。 5 and 6 are explanatory diagrams of the first embodiment of the present invention. FIG. 5 is an overall configuration diagram, and FIG. 6 is an internal configuration diagram of insulation monitoring means. In these drawings, the same or corresponding parts as those in FIG.
しかして、5は零相電圧検出手段、6は相電圧検出手段で、両検出手段はコンデンサーを使用した場合であるが、他の手段でも良い。7は絶縁監視手段で、該絶縁監視手段7には零相変流器3で検出した零相電流信号と、零相電圧検出手段5で検出した零相電圧信号及び相電圧検出手段6で検出した相電圧信号(各充電相と大地間電圧)を入力する。
Thus, 5 is a zero-phase voltage detection means, 6 is a phase voltage detection means, and both detection means use a capacitor, but other means may be used.
この絶縁監視手段7は図6に示す構成となっており、入力された各信号はフィルタFで不要ノイズを除去し、増幅器Aで増幅し、各信号の絶対値を得るためA/D変換器71でアナログ−デジタル変換して演算器72に入力する。又位相を判別するために各信号は波形整形回路Pで波形整形し、演算器72に入力する。73はデスプレー等による表示手段、74はリレー、75は警報手段を示し、演算器72の出力信号によって作動される。
The insulation monitoring means 7 has a configuration shown in FIG. 6. An input signal is an A / D converter for removing unnecessary noise by a filter F, amplifying by an amplifier A, and obtaining an absolute value of each signal. The analog-digital conversion is performed at 71 and the result is input to the
なお、相電圧検出手段6は、三相の各相から必ずしも信号を取る必要はなく、任意の一相の相電圧と零相電圧から本来の相電圧(絶縁劣化のない状態の相電圧)を演算器でベクトル演算で求め、更に残りの他相の本来の相電圧は120°づつの位相差を持たせることで求め、更に、絶縁劣化時の他相の相電圧を求めても良い。 The phase voltage detection means 6 does not necessarily take signals from each of the three phases. The original phase voltage (phase voltage without insulation deterioration) is obtained from any one phase voltage and zero phase voltage. It may be obtained by a vector calculation by an arithmetic unit, and the original phase voltage of the remaining other phase may be obtained by giving a phase difference of 120 °, and the phase voltage of the other phase at the time of insulation deterioration may be obtained.
演算器72は、まず、入力された零相電流信号I0,零相電圧信号V0の位相から絶縁劣化が電源側か,負荷側かの方向判別を行う。この方向判別は、例えば零相電圧V0に対し遅れ45°〜225°位相の範囲を、負荷側事故又は絶縁劣化と判断する。
The
又、相電圧検出手段で得られた各相電圧位相と零相電圧位相から、零相電圧に対し遅れ90°〜180°となる条件の相電圧位相の相が地絡相又は絶縁劣化相と判断する。 In addition, the phase voltage phase of the condition that is 90 ° to 180 ° behind the zero phase voltage from the phase voltage phase and the zero phase voltage phase obtained by the phase voltage detection means is the ground fault phase or the insulation deterioration phase. to decide.
電源側の絶縁劣化又は事故であれば次の処理は行わないが、負荷側であれば、零相電流検出手段で検出された零相電流I0の絶対値と位相及び零相電圧V0の絶対値と位相から中性点抵抗R0により接地線に流れる抵抗分電流Ir0を前記の(3)式により演算器72で求める。
If the power supply side of the insulation deterioration or accident does not perform the following processing, if the load side, the absolute value and the absolute phase and zero-phase voltage V0 of the zero-phase current I0 detected by the zero-phase current detecting means From the value and phase, the resistance component current Ir0 flowing to the ground line by the neutral point resistance R0 is obtained by the
次に、絶縁劣化抵抗Rgに流れる電流Igを求める。この電流Igは負荷側対地静電容量に流れる電流IcLと零相電流I0を合成した電流であり、地絡相電圧Vgと同相の電流となるから、零相電圧V0と地絡相電圧Vgの位相差をθとしたとき前記の(4)式による演算器により求める。 Next, the current Ig flowing through the insulation deterioration resistance Rg is obtained. This current Ig is a current obtained by synthesizing the current IcL flowing through the load-side ground capacitance and the zero-phase current I0, and is a current in phase with the ground-fault voltage Vg. Therefore, the zero-phase voltage V0 and the ground-fault voltage Vg When the phase difference is θ, it is obtained by the calculator according to the above equation (4).
次に、絶縁劣化時の地絡相電圧Vgを絶縁劣化抵抗Rgに流れる電流Igで除した値が絶縁劣化抵抗RgであるからRg=Vg÷Igで求める。 Next, since the value obtained by dividing the ground fault phase voltage Vg at the time of insulation deterioration by the current Ig flowing through the insulation deterioration resistance Rg is the insulation deterioration resistance Rg, Rg = Vg ÷ Ig is obtained.
これらの電流値Ig及び抵抗値Rgを絶縁監視手段7の表示手段73で表示して絶縁状態を監視し、又は検出閾値を設け閾値を超えたら警報手段75及び/又はリレー74で接点を出力させるなどにより絶縁状態を監視する。
These current value Ig and resistance value Rg are displayed on the display means 73 of the insulation monitoring means 7 to monitor the insulation state, or when a detection threshold is set and the threshold is exceeded, the alarm means 75 and / or the
又、地絡方向継電装置又は方向性漏電継電器として機能させる場合は、絶縁劣化抵抗に流れる電流Igの値の動作閾値を設け、この閾値を超えたとき警報及び/又は接点を出力させて保護動作をさせる。 Moreover, when functioning as a ground fault direction relay device or a directional leakage relay, an operation threshold is set for the value of the current Ig flowing through the insulation deterioration resistance, and when this threshold is exceeded, an alarm and / or contact is output to protect it. Make it work.
図7及び図8は本発明の第2の実施の形態の説明図で、図7は全体の構成図、図8は絶縁監視手段の構成図を示し、第1の実施の形態との相違は、零相電流検出手段での零相電流の検出は、EVTの接地線に設けた零相変流器によって行い、線間電圧検出はEVTの二次回路から、零相電圧の検出はEVTの三次回路によって行う点である。なお、図5及び図6と同じか相当部分にはこれと同じ符号を付して説明を省略する。 7 and 8 are explanatory diagrams of the second embodiment of the present invention. FIG. 7 is an overall configuration diagram, FIG. 8 is a configuration diagram of the insulation monitoring means, and the difference from the first embodiment is as follows. The zero-phase current detection means detects the zero-phase current using a zero-phase current transformer provided on the EVT ground line, detects the line voltage from the secondary circuit of the EVT, and detects the zero-phase voltage of the EVT. This is a point performed by a tertiary circuit. Note that the same or corresponding parts as those in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof is omitted.
絶縁監視手段7には、零相電流検出手段3の零相電流とEVTの三次回路43の零相電圧の各信号及び二次回路42の線間電圧を入力する。各信号はフィルタFで不要ノイズを除去し、増幅器Aで増幅し、各信号の絶対値を得るためA/D変換器71に入力され演算器72に送る。又、位相判別するため波形整形回路Pで波形整形し演算器72に送る。なお、EVTの二次回路42の任意の一相の線間電圧でも可能である。
The insulation monitoring means 7 receives the zero-phase current of the zero-phase current detection means 3, the zero-phase voltage signals of the EVT
EVTの二次回路42の各線間電圧値を相電圧値に換算し30°遅らせた位相として各相電圧を得る。あるいは任意の一相の線間電圧を相電圧に換算して30°遅らせた位相とし、その他の相電圧は三相三線の場合、120°づつ位相がずれることが分かっているため演算により各相電圧を求める。更に、零相電圧V0とベクトル演算することで絶縁劣化時の各相電圧を得、この絶縁劣化時の各相電圧と零相電圧V0の各値から絶縁劣化相又は地絡相がどの相か判別し、地絡相電圧Vgの値及び位相を求める。
Each line voltage value of the EVT
零相電流検出手段3で検出された零相電流I0は接地線に流れる電流Ir0に等しいから、その絶対値を零相電圧V0の位相と地絡相電圧Vgの位相差θから絶縁劣化抵抗に流れる電流Igを前記の(4)式のIr0をI0とすることにより求める。 Since the zero-phase current I0 detected by the zero-phase current detection means 3 is equal to the current Ir0 flowing through the ground line, the absolute value is converted from the phase difference θ between the zero-phase voltage V0 and the ground fault phase voltage Vg to the insulation deterioration resistance. The flowing current Ig is obtained by setting Ir0 in the above equation (4) to I0.
次に、絶縁劣化時の地絡相電圧Vgを絶縁劣化抵抗Rgに流れる電流Igで除した値が絶縁劣化抵抗Rgであるから、Rg=Vg÷Igで求めることができる。 Next, since the value obtained by dividing the ground fault phase voltage Vg at the time of insulation deterioration by the current Ig flowing through the insulation deterioration resistance Rg is the insulation deterioration resistance Rg, it can be obtained by Rg = Vg ÷ Ig.
これらの絶縁劣化時の電流値Ig及び絶縁劣化抵抗値Rgを絶縁監視の場合は表示手段で表示し、又は検出閾値を設けて閾値を超えたとき警報及び/又は接点を出力させ被監視電路の絶縁劣化状態を監視する。 In the case of insulation monitoring, the current value Ig and insulation deterioration resistance value Rg at the time of insulation deterioration are displayed on the display means, or when a detection threshold value is set and the threshold value is exceeded, an alarm and / or a contact is output to output the monitored circuit Monitor insulation degradation.
地絡継電装置又は漏電継電器の機能をもたせる場合は、絶縁劣化時の電流Igの値の動作閾値を設け、閾値を超えたとき警報及び/又は接点を出力させ所定の保護動作をさせる。 When the function of the ground fault relay device or the earth leakage relay is provided, an operation threshold value of the current Ig at the time of insulation deterioration is provided, and when the threshold value is exceeded, an alarm and / or a contact is output to perform a predetermined protective operation.
この実施の形態のように、零相電流検出手段3を地絡線44に設けると、零相電流検出手段3から見て被監視電路全てが負荷側となり電路全体の絶縁監視ができるとともに接地線に流れる電流Ir0を直接計測できる。又、EVT非接地電路に於いては地絡相電圧は、EVTの二次回路42と三次回路43から演算により求められ、相電圧検出手段6は不要となる等のメリットがある。
If the zero-phase current detection means 3 is provided on the
以上、本発明において、記載された具体例に対してのみ詳細に説明したが、本発明の技術思想の範囲で零相電圧零相電流および相電圧の検出方法を適宜組み合わせて適用するなど多彩な変形および修正が可能であることは、当業者にとって明白なことであり、このような変形および修正が特許請求の範囲に属することは当然のことである。 As described above, the present invention has been described in detail only with respect to the specific examples described above, but various methods such as applying a suitable combination of the zero-phase voltage zero-phase current and the phase voltage detection method within the scope of the technical idea of the present invention. It will be apparent to those skilled in the art that variations and modifications can be made, and it is obvious that such variations and modifications fall within the scope of the claims.
1…電源変圧器
2…被監視電路
3…零相変流器
4…接地用変圧器
5…零相電圧検出手段
6…相電圧検出手段
7…絶縁監視手段
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