JP2015206741A - insulation monitoring device - Google Patents

insulation monitoring device Download PDF

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JP2015206741A
JP2015206741A JP2014088776A JP2014088776A JP2015206741A JP 2015206741 A JP2015206741 A JP 2015206741A JP 2014088776 A JP2014088776 A JP 2014088776A JP 2014088776 A JP2014088776 A JP 2014088776A JP 2015206741 A JP2015206741 A JP 2015206741A
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wire
current
ground
ground fault
resistance
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JP6408785B2 (en
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鈴木 正美
Masami Suzuki
正美 鈴木
祐輔 篠崎
Yusuke Shinozaki
祐輔 篠崎
高明 上野
Takaaki Ueno
高明 上野
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KANTO ELECTRICAL SAFETY INSPECTION ASS
KANTO ELECTRICAL SAFETY INSPECTION ASSOCIATION
Midori Anzen Co Ltd
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KANTO ELECTRICAL SAFETY INSPECTION ASS
KANTO ELECTRICAL SAFETY INSPECTION ASSOCIATION
Midori Anzen Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide an insulation monitoring device capable of precisely detecting a leakage current even when a suppression resistance is interposed in a B kind ground line.SOLUTION: When electric leakage occurs in the secondary circuits of a transformer and the earth resistance of secondary electric wires becomes smaller than a threshold resistance, by opening a changing-over switch SW1, the transformer is in a state where a suppression resistance r is interposed in a B kind ground line 11. It is determined that one-line ground has occurred in the secondary electric wires and it is supposed that capacitance between each secondary electric wire and ground is the same, and a leakage current by one-line ground is calculated. Therefore, the leakage current can be precisely calculated even when the suppression resistance r is interposed in the B kind ground line 11.

Description

本発明は、変圧器のB種接地線に流れる電流を検出して、二次側電線の絶縁状態を監視する絶縁監視装置に係り、特に、B種接地線に電流を抑制するための抑制抵抗を設置した場合でも、絶縁状態を高精度に監視する技術に関する。   The present invention relates to an insulation monitoring device that detects a current flowing in a B-type grounding wire of a transformer and monitors an insulation state of a secondary-side electric wire, and more particularly, a suppression resistor for suppressing a current in a B-type grounding wire. The present invention relates to a technique for monitoring the insulation state with high accuracy even when installing the.

送電線により送電された高電圧を受電変圧器にて低電圧に変換して工場や一般家庭に電力を供給することが行われている。受電変圧器は、二次側電線が地絡して漏電することがあり、このような場合にはいち早く漏電を検出して電路を遮断する必要がある。そこで従来より、電線の絶縁状態を監視する絶縁監視装置が用いられている。従来の絶縁監視装置として、Igr方式を採用したものが知られている(特許文献1参照)。   A high voltage transmitted through a transmission line is converted into a low voltage by a power receiving transformer to supply power to a factory or a general household. In the power receiving transformer, there is a case where the secondary side electric wire is grounded and the electric leakage is caused. In such a case, it is necessary to quickly detect the electric leakage and interrupt the electric circuit. Therefore, conventionally, an insulation monitoring device for monitoring the insulation state of the electric wire has been used. As a conventional insulation monitoring device, one employing the Igr method is known (see Patent Document 1).

Igr方式の絶縁監視装置では、変圧器の二次側の電線に接続されるB種接地線に、商用周波数(50Hz、60Hz)とは異なる周波数の監視用信号を重畳する。そして、B種接地線に流れる監視信号と同一周波数の信号を検出し、この検出信号から漏電電流を求める。更に、漏電電流には、抵抗成分と容量成分(リアクタンス成分)が存在するので、容量成分の電流を除去して抵抗成分の電流のみを検出し、これを漏電電流とする。この漏電電流が閾値を超えた場合に警報を発する。   In the Igr type insulation monitoring device, a monitoring signal having a frequency different from the commercial frequency (50 Hz, 60 Hz) is superimposed on a B-type ground wire connected to the secondary-side electric wire of the transformer. And the signal of the same frequency as the monitoring signal which flows into a B class grounding line is detected, and a leakage current is calculated | required from this detection signal. Further, since the leakage current includes a resistance component and a capacitance component (reactance component), the current of the resistance component is detected by removing the current of the capacitance component, and this is used as the leakage current. An alarm is issued when the leakage current exceeds a threshold value.

ところで、昨今において、B種接地線に抑制抵抗を挿入することにより、漏電が発生した際に、B種接地線に流れる電流を抑制することが行われている。この場合には、B種接地線の抵抗をゼロと見なすことができないので、従来の演算方法を用いて漏電電流を算出することができない。以下、図7、図8を参照して説明する。   By the way, in recent years, a current flowing in the B-type ground line is suppressed when a leakage occurs by inserting a suppression resistor in the B-type ground line. In this case, since the resistance of the class B grounding wire cannot be regarded as zero, the leakage current cannot be calculated using the conventional calculation method. Hereinafter, a description will be given with reference to FIGS.

図7は、正常時におけるIgr方式を用いた絶縁監視装置の説明図であり、単相2線式の回路を示している。図7に示すように、変圧器110の二次側電線のうちの1つは、B種接地線101を介してグランドに接地されている。このB種接地線101には、監視信号を重畳するための信号発生器103と、B種接地線101に流れる監視信号を検出する電流検出器105と、該電流検出器105で検出される電流に基づいて地絡抵抗を演算する制御器102と、を備えている。また、B種接地線101に流れる電流を抑制するための抑制抵抗r、及びスイッチ104が設けられており、通常時はスイッチ104を閉塞して抑制抵抗rの両端を短絡する。   FIG. 7 is an explanatory diagram of an insulation monitoring apparatus using the Igr method in a normal state, and shows a single-phase two-wire circuit. As shown in FIG. 7, one of the secondary side electric wires of the transformer 110 is grounded to the ground via a B-type ground wire 101. The type B ground line 101 has a signal generator 103 for superimposing a monitoring signal, a current detector 105 for detecting a monitoring signal flowing in the type B ground line 101, and a current detected by the current detector 105. And a controller 102 for calculating ground fault resistance based on the above. In addition, a suppression resistor r and a switch 104 for suppressing the current flowing through the B-type ground line 101 are provided, and the switch 104 is normally closed to short-circuit both ends of the suppression resistor r.

そして、信号発生器103にてB種接地線に商用周波数とは異なる特定周波数(例えば、20Hz)の監視信号を重畳する。電線111に地絡が発生すると、B種接地線に地絡電流I101が流れ、該地絡電流I101には監視信号が含まれるので、制御器102にて監視信号が検出される。検出した監視信号から容量成分(静電容量C101を介して流れる電流)を除去することにより、地絡抵抗R101を求めることができる。   The signal generator 103 superimposes a monitoring signal having a specific frequency (for example, 20 Hz) different from the commercial frequency on the B-type ground line. When a ground fault occurs in the electric wire 111, a ground fault current I101 flows through the B-type grounding line, and since the ground fault current I101 includes a monitor signal, the controller 102 detects the monitor signal. The ground fault resistance R101 can be obtained by removing the capacitance component (current flowing through the capacitance C101) from the detected monitoring signal.

一方、地絡が発生したときは図8に示すように、スイッチ104を開放とし、B種接地線101に抑制抵抗rを介置する。この場合には、電線112とグランドとの間に生じる静電容量C102が無視できなくなり、抵抗R101に流れる電流は、静電容量C102に流れる電流I103とB種接地線101に流れる電流I102に分流される。従って、電流検出器105で検出される電流を測定しても、抵抗R101に流れる漏電電流を正確に求めることができない。   On the other hand, when a ground fault occurs, as shown in FIG. 8, the switch 104 is opened, and the suppression resistor r is interposed in the B-type ground line 101. In this case, the capacitance C102 generated between the electric wire 112 and the ground cannot be ignored, and the current flowing through the resistor R101 is divided into the current I103 flowing through the capacitance C102 and the current I102 flowing through the B-type ground line 101. Is done. Therefore, even if the current detected by the current detector 105 is measured, the leakage current flowing through the resistor R101 cannot be accurately obtained.

特許第4210210号公報Japanese Patent No. 4210210

上述したように、B種接地線101に抑制抵抗rを介置した場合には、電線111が地絡した際に、図8に示す電流I103が流れるので、電流検出器105で検出される電流から電線111の漏電電流を求めることができなくなるという問題があった。   As described above, when the suppression resistor r is interposed in the class B ground wire 101, the current I103 shown in FIG. 8 flows when the electric wire 111 is grounded. Therefore, there is a problem that the leakage current of the electric wire 111 cannot be obtained.

本発明はこのような従来の課題を解決するためになされたものであり、その目的とするところは、B種接地線に抑制抵抗を介置した場合でも漏電電流を高精度に検出することのできる絶縁監視装置を提供することにある。   The present invention has been made to solve such a conventional problem. The object of the present invention is to detect a leakage current with high accuracy even when a suppression resistor is interposed in a B-type ground wire. An object of the present invention is to provide an insulation monitoring device that can be used.

上記目的を達成するため、本願請求項1に記載の発明は、変圧器のB種接地線に、商用周波数と異なる特定周波数の監視信号を重畳する監視信号発生器と、前記B種接地線に流れる電流に含まれる前記特定周波数の電流を検出する電流検出手段と、前記特定周波数の電流の有効成分及び無効成分に基づいて、前記変圧器の二次側電線の地絡抵抗、及び静電容量を求める抵抗・静電容量算出手段と、前記B種接地線に設けられ、抑制抵抗と、該抑制抵抗の両端の短絡、開放を切り替える切替スイッチと、が並列接続された並列接続回路と、前記地絡抵抗が閾値抵抗を上回る場合には前記抑制抵抗の両端を短絡し、前記地絡抵抗が前記閾値抵抗よりも小さい場合には前記抑制抵抗の両端を開放するように前記切替スイッチを制御する切替制御手段と、前記抑制抵抗の両端が開放された際には、前記二次側電線に一線地絡が生じたものと判断し、且つ、各二次側電線とグランドとの間の静電容量が同一であると仮定して、前記一線地絡による漏電電流を算出する電流演算手段と、を備えたことを特徴とする。   In order to achieve the above object, the invention described in claim 1 of the present application includes a monitoring signal generator that superimposes a monitoring signal having a specific frequency different from a commercial frequency on a B-type grounding line of a transformer, and a B-type grounding line. Current detection means for detecting the current of the specific frequency included in the flowing current, ground fault resistance of the secondary side wire of the transformer, and capacitance based on the effective component and the ineffective component of the current of the specific frequency A parallel connection circuit in which a resistance / capacitance calculation means for obtaining the same, a suppression switch and a changeover switch that switches between short-circuiting and opening of both ends of the suppression resistance are provided in parallel to the B-type ground line; When the ground fault resistance exceeds the threshold resistance, both ends of the suppression resistor are short-circuited, and when the ground fault resistance is smaller than the threshold resistance, the changeover switch is controlled to open both ends of the suppression resistance. Switching control means When both ends of the suppression resistor are opened, it is determined that a single-wire ground fault has occurred in the secondary side wire, and the capacitance between each secondary side wire and the ground is the same. Assuming that there is a current calculation means for calculating a leakage current due to the one-line ground fault, the current calculation means is provided.

請求項2に記載の発明は、前記電流演算手段は、前記B種接地線に接続されない活線が地絡したと仮定して第1漏電電流を演算し、前記B種接地線に接続された中性線が地絡したと仮定して第2漏電電流を演算し、前記第1漏電電流と第2漏電電流のうち、大きい方の電流を漏電電流として採用することを特徴とする。   According to a second aspect of the present invention, the current calculation means calculates a first leakage current on the assumption that a live line that is not connected to the B-type ground line has a ground fault, and is connected to the B-type ground line. The second leakage current is calculated on the assumption that the neutral wire is grounded, and the larger one of the first leakage current and the second leakage current is employed as the leakage current.

請求項3に記載の発明は、前記変圧器の二次側は、R相、S相、T相の3相デルタ結線であり、このうち1つの相に接続される電線を前記中性線とし、他の2つの相に接続される電線を前記活線とすることを特徴とする。   According to a third aspect of the present invention, the secondary side of the transformer is a three-phase delta connection of an R phase, an S phase, and a T phase, and an electric wire connected to one of the phases is the neutral wire. The electric wires connected to the other two phases are the live wires.

請求項4に記載の発明は、前記変圧器の二次側は、単相3線結線であり、該単相3線結線の2つの端部に接続される各電線を前記活線とし、中間点に接続される電線を中性線とすることを特徴とする。   According to a fourth aspect of the present invention, the secondary side of the transformer is a single-phase three-wire connection, each wire connected to two ends of the single-phase three-wire connection is the live wire, The electric wire connected to the point is a neutral wire.

本発明に係る絶縁監視装置では、B種接地線に抑制抵抗が介置された場合でも、二次側電線とグランドとの間の静電容量が各電線で同一であると仮定し、且つ、漏電の原因が一線地絡であると仮定して漏電電流を算出する。従って、地絡した電線に流れる漏電電流を高精度に算出することが可能となる。   In the insulation monitoring device according to the present invention, it is assumed that the capacitance between the secondary side electric wire and the ground is the same for each electric wire even when the suppression resistor is interposed in the B-type ground wire, and The leakage current is calculated assuming that the cause of the leakage is a one-line ground fault. Therefore, the leakage current flowing through the grounded electric wire can be calculated with high accuracy.

また、活線が地絡した場合の第1漏電電流と、中性線が地絡した場合の第2漏電電流の双方を算出し、これらのうちの大きい方の電流を漏電電流として採用するので、一線地絡した電線が活線である場合、及び中性線である場合の双方において、漏電電流を高精度に算出することが可能となる。   In addition, since both the first leakage current when the live line is grounded and the second leakage current when the neutral line is grounded are calculated, the larger one of these is adopted as the leakage current. In both cases where the grounded electric wire is a live wire and a neutral wire, the leakage current can be calculated with high accuracy.

更に、変圧器の二次側回路が三相デルタ結線である場合、及び単相3線結線である場合において、適用することが可能である。   Furthermore, the present invention can be applied when the secondary circuit of the transformer is a three-phase delta connection and a single-phase three-wire connection.

本発明の第1実施形態に係る絶縁監視装置の構成を示す回路図である。It is a circuit diagram which shows the structure of the insulation monitoring apparatus which concerns on 1st Embodiment of this invention. 信号発生器による重畳電圧V1と、二次側電線の地絡抵抗Rg及び静電容量Cgの等価回路図である。It is an equivalent circuit diagram of the superimposed voltage V1 by a signal generator, the ground fault resistance Rg of the secondary side electric wire, and the electrostatic capacitance Cg. 本発明の実施形態に係る絶縁監視装置による漏電電流の演算手順を示すフローチャートである。It is a flowchart which shows the calculation procedure of the leakage current by the insulation monitoring apparatus which concerns on embodiment of this invention. 本発明の実施形態に係り、活線が一線地絡した場合の等価回路図である。FIG. 6 is an equivalent circuit diagram in a case where a live line is a single-line ground fault according to the embodiment of the present invention. 本発明の実施形態に係り、中性線が一線地絡した場合の等価回路図である。FIG. 6 is an equivalent circuit diagram in a case where a neutral wire is grounded in a single line according to the embodiment of the present invention. 本発明の第2実施形態に係る絶縁監視装置の構成を示す回路図である。It is a circuit diagram which shows the structure of the insulation monitoring apparatus which concerns on 2nd Embodiment of this invention. 単相2線式回路の、正常時におけるIgr方式を用いた絶縁監視装置の説明図である。It is explanatory drawing of the insulation monitoring apparatus using the Igr system in the normal time of a single phase two-wire circuit. 単相2線式回路の、地絡発生時におけるIgr方式を用いた絶縁監視装置の説明図である。It is explanatory drawing of the insulation monitoring apparatus using the Igr system at the time of the occurrence of a ground fault of a single phase two-wire circuit.

以下、本発明の実施形態を図面を参照して説明する。   Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[第1実施形態の説明]
図1は、本発明第1実施形態に係る絶縁監視装置が採用された三相デルタ結線回路を示す説明図である。図1に示すように、この絶縁監視装置は、変圧器の二次側回路51がR相、S相、T相の3つの相からなる三相デルタ結線とされている。このうち、S相が中性相とされており、並列接続回路12が介置されたB種接地線11を経由してグランドに接地されている。
[Description of First Embodiment]
FIG. 1 is an explanatory diagram showing a three-phase delta connection circuit employing an insulation monitoring device according to the first embodiment of the present invention. As shown in FIG. 1, in this insulation monitoring device, the secondary side circuit 51 of the transformer is a three-phase delta connection composed of three phases of R phase, S phase, and T phase. Of these, the S phase is a neutral phase, and is grounded to the ground via the B-type grounding wire 11 in which the parallel connection circuit 12 is interposed.

B種接地線11には、並列接続回路12以外に、絶縁監視用の信号として商用周波数(50Hz、60Hz)とは相違する特定周波数(例えば、20Hz)の重畳電圧V1を重畳する信号発生器13(監視信号発生器)と、B種接地線11に流れる電流を検出する電流センサ14(電流検出手段)と、が接続されている。電流センサ14及び信号発生器13は、制御器15に接続されている。   In addition to the parallel connection circuit 12, a signal generator 13 that superimposes a superimposed voltage V1 of a specific frequency (for example, 20 Hz) different from the commercial frequency (50 Hz, 60 Hz) as an insulation monitoring signal on the B-type ground line 11. A (monitoring signal generator) and a current sensor 14 (current detection means) for detecting a current flowing through the B-type ground line 11 are connected. The current sensor 14 and the signal generator 13 are connected to the controller 15.

並列接続回路12は、抑制抵抗rと、切替スイッチSW1と、保護回路21を備えており、これらが互いに並列接続されている。切替スイッチSW1は、制御器15の制御下で閉塞、開放が制御される。保護回路21は、落雷等に起因して変圧器に過大な電圧が加えられ、該保護回路21の両端電圧が所定の電圧(例えば、600ボルト)を超えた場合に、両端を短絡して電流を流す機能を備えている。   The parallel connection circuit 12 includes a suppression resistor r, a changeover switch SW1, and a protection circuit 21, which are connected in parallel to each other. The changeover switch SW1 is controlled to be closed and opened under the control of the controller 15. When an excessive voltage is applied to the transformer due to lightning or the like, and the voltage across the protection circuit 21 exceeds a predetermined voltage (eg, 600 volts), the protection circuit 21 It has a function to flow.

制御器15は、電流センサ14で検出される電流から上述した重畳電圧V1と同一周波数の電流を検出し、この電流に基づいてIgr方式により変圧器の二次側回路51に接続された各電線L1,L2,L3とグランドとの間の地絡抵抗Rg、及び静電容量Cgを算出する。即ち、制御器15は、特定周波数の電流の有効成分及び無効成分に基づいて、変圧器の二次側電線L1,L2,L3の地絡抵抗、及び静電容量を求める抵抗・静電容量算出手段としての機能を備える。そして、地絡抵抗Rgが予め設定した閾値抵抗Rthよりも小さいと判断した場合には、各電線L1,L2,L3のうちの少なくとも一つに、漏電(地絡)が発生しているものと判断する。   The controller 15 detects a current having the same frequency as the above-described superimposed voltage V1 from the current detected by the current sensor 14, and based on this current, each electric wire connected to the secondary circuit 51 of the transformer by the Igr method. A ground fault resistance Rg between L1, L2, L3 and the ground and a capacitance Cg are calculated. That is, the controller 15 calculates the resistance / capacitance to obtain the ground fault resistance and capacitance of the secondary side wires L1, L2, and L3 of the transformer based on the effective component and the ineffective component of the current of the specific frequency. A function as a means is provided. And when it is judged that the ground fault resistance Rg is smaller than the preset threshold resistance Rth, a fault (ground fault) has occurred in at least one of the electric wires L1, L2, L3. to decide.

また、制御器15は、地絡抵抗Rgが閾値抵抗Rthよりも大きいと判断した場合(漏電が発生していない場合)には、切替スイッチSW1を閉塞し、地絡抵抗Rgが閾値抵抗Rthよりも小さい場合(漏電が発生している場合)には、切替スイッチSW1を開放するように制御する。即ち、地絡抵抗Rgが小さく、漏電が発生しているものと判断される場合には、切替スイッチSW1を開放して、B種接地線11に抑制抵抗rが介置されるように切り替えることにより、B種接地線11に過大な電流が流れることを阻止する。そして、切替スイッチSW1を開放した場合には、後述する演算方法により漏電電流を演算することにより、図8にて説明した問題を回避する。   Further, when the controller 15 determines that the ground fault resistance Rg is larger than the threshold resistance Rth (when no electric leakage occurs), the controller 15 closes the changeover switch SW1, and the ground fault resistance Rg is higher than the threshold resistance Rth. If it is also small (when electric leakage has occurred), the selector switch SW1 is controlled to be opened. That is, when it is determined that the ground fault resistance Rg is small and the electric leakage has occurred, the changeover switch SW1 is opened, and switching is performed so that the suppression resistor r is interposed in the class B ground line 11. Thus, an excessive current is prevented from flowing through the B-type ground line 11. When the changeover switch SW1 is opened, the problem described with reference to FIG. 8 is avoided by calculating the leakage current by a calculation method described later.

即ち、制御器15は、地絡抵抗Rgが閾値抵抗Rthを上回る場合には抑制抵抗rの両端を短絡し、地絡抵抗Rgが閾値抵抗Rthよりも小さい場合には抑制抵抗rの両端を開放するように切替スイッチSW1を制御する切替制御手段としての機能を備えている。更に、抑制抵抗rの両端が開放された際には、二次側電線に一線地絡が生じたものと判断し、且つ、各二次側電線とグランドとの間の静電容量が同一であると仮定して、一線地絡による漏電電流を算出する電流演算手段としての機能を備えている。なお、制御器15は、例えば、中央演算ユニット(CPU)や、RAM、ROM、ハードディスク等の記憶手段からなる一体型のコンピュータとして構成することができる。   That is, the controller 15 shorts both ends of the suppression resistor r when the ground fault resistance Rg exceeds the threshold resistance Rth, and opens both ends of the suppression resistor r when the ground fault resistance Rg is smaller than the threshold resistance Rth. Thus, a function as switching control means for controlling the switching switch SW1 is provided. Furthermore, when both ends of the suppression resistor r are opened, it is determined that a one-wire ground fault has occurred in the secondary side electric wires, and the capacitance between each secondary side electric wire and the ground is the same. It is assumed that there is a function as current calculation means for calculating a leakage current due to a one-line ground fault. The controller 15 can be configured as an integrated computer including a central processing unit (CPU) and storage means such as a RAM, a ROM, and a hard disk.

また、図1に示すように、変圧器の二次側回路51に設けられるS相、R相、T相の各電線L1、L2、L3とグランドとの間に存在する静電容量をそれぞれ、C1、C2、C3とし、各電線L1、L2、L3とグランドとの間の抵抗をR1、R2、R3とする。すると、重畳電圧V1に対して、図2に示す如くの等価回路が得られる。図2において、符号V1は監視信号の重畳電圧を示している。符号CgはC1〜C3の合計の静電容量であり、該静電容量CgはCg=C1+C2+C3で示すことができる。また、符号RgはR1〜R3の合計の抵抗であり、1/Rg=1/R1+1/R2+1/R3で示すことができる。   In addition, as shown in FIG. 1, the capacitances existing between the S-phase, R-phase, and T-phase electric wires L1, L2, and L3 provided in the secondary circuit 51 of the transformer and the ground, respectively, C1, C2, and C3, and resistances between the electric wires L1, L2, and L3 and the ground are R1, R2, and R3. Then, an equivalent circuit as shown in FIG. 2 is obtained for the superimposed voltage V1. In FIG. 2, the symbol V1 indicates the superposed voltage of the monitoring signal. The symbol Cg is the total capacitance of C1 to C3, and the capacitance Cg can be represented by Cg = C1 + C2 + C3. The symbol Rg is the total resistance of R1 to R3, and can be represented by 1 / Rg = 1 / R1 + 1 / R2 + 1 / R3.

そして、本実施形態に係る絶縁監視装置では、制御器15において上述したIgr方式を用いることにより3つの電線L1〜L3とグランドとの間の地絡抵抗Rgを演算し、この地絡抵抗Rgが閾値抵抗Rthを下回った場合、即ち、電線L1〜L3のうち少なくとも一つの電線にて漏電が発生しているものと判断された場合に、切替スイッチSW1を閉塞から開放に切り替える。更に、切り替えスイッチSW1を開放した場合には、図8に示した如くの問題が生じるので、以下に示す演算方式により、漏電電流を算出する。   In the insulation monitoring apparatus according to the present embodiment, the controller 15 calculates the ground fault resistance Rg between the three electric wires L1 to L3 and the ground by using the Igr method described above, and the ground fault resistance Rg is calculated as follows. When the value falls below the threshold resistance Rth, that is, when it is determined that a leakage has occurred in at least one of the wires L1 to L3, the changeover switch SW1 is switched from closed to open. Furthermore, since the problem as shown in FIG. 8 occurs when the changeover switch SW1 is opened, the leakage current is calculated by the following calculation method.

本実施形態では、漏電の発生原因が一線地絡によるものと仮定し、且つ、各電線L1、L2、L3とグランドとの間の静電容量C1、C2、C3が全て同一の静電容量「C」であると仮定して、地絡した電線からの漏電電流を高精度に算出する。   In the present embodiment, it is assumed that the cause of the leakage is due to a single-line ground fault, and the capacitances C1, C2, and C3 between the electric wires L1, L2, and L3 and the ground are all the same capacitance “ Assuming “C”, the leakage current from the grounded electric wire is calculated with high accuracy.

また、一線地絡については、中性相であるS相が地絡する場合(以下「中性線地絡」という)、及び活線であるR相またはT相が地絡する場合(以下「活線地絡」という)の2通りがある。本実施形態では、後述する演算手法により中性線地絡の場合の漏電電流、及び活線地絡の場合の漏電電流の双方を算出し、大きい方の電流を一線地絡時の漏電電流として求める。   In addition, with regard to the single-line ground fault, the S phase that is a neutral phase is grounded (hereinafter referred to as “neutral ground fault”), and the R phase or T phase that is a live line is grounded (hereinafter “ There are two types of live ground faults). In this embodiment, both the leakage current in the case of a neutral ground fault and the leakage current in the case of a live ground fault are calculated by the calculation method described later, and the larger current is used as the leakage current at the time of the one-wire ground fault. Ask.

また、図4に示すように、R相電圧はS相電圧に対して位相が60°進み、T相電圧は、S相電圧に対して120°進んでいる。つまり、活線地絡の場合には、図4に示すT相が地絡した場合とR相が地絡した場合で、流れる電流が異なる。具体的には、地絡抵抗が同一であってもT線地絡電流の方が、R線地絡電流よりも大きい電流が流れることになる。従って、本実施形態では、一線地絡が発生した場合には、T線が地絡したものと判断して、地絡電流を演算する。   As shown in FIG. 4, the phase of the R-phase voltage is advanced by 60 ° with respect to the S-phase voltage, and the phase of the T-phase voltage is advanced by 120 ° with respect to the S-phase voltage. That is, in the case of a live-line ground fault, the flowing current differs depending on whether the T phase shown in FIG. 4 is ground fault or the R phase is ground fault. Specifically, even if the ground fault resistance is the same, a larger current flows in the T-line ground fault current than in the R-line ground fault current. Therefore, in this embodiment, when a one-line ground fault occurs, it is determined that the T-line is grounded, and the ground fault current is calculated.

以下、第1実施形態に係る絶縁監視装置の作用を図3に示すフローチャートを参照して説明する。この処理は、図1に示す制御器15により、所定の演算周期で実行される。また、初期的には、切替スイッチSW1は閉塞されており、抑制抵抗rの両端は短絡されている。つまり、切替スイッチSW1はノーマリクローズ型のスイッチである。   Hereinafter, the operation of the insulation monitoring apparatus according to the first embodiment will be described with reference to the flowchart shown in FIG. This process is executed at a predetermined calculation cycle by the controller 15 shown in FIG. Initially, the changeover switch SW1 is closed and both ends of the suppression resistor r are short-circuited. That is, the changeover switch SW1 is a normally closed type switch.

初めに、図3のステップS11において、制御器15は、電流センサ14で検出される電流から、変圧器の二次側回路51に接続された各電線L1〜L3とグランドとの間の地絡抵抗Rg及び静電容量Cgを算出する。この演算は、信号発生器13からB種接地線11に重畳した重畳電圧V1の位相と、電流センサ14で検出される重畳電圧V1と同一周波数の電流の位相との位相差から、地絡抵抗Rg、及び静電容量Cgを算出する。   First, in step S11 of FIG. 3, the controller 15 determines the ground fault between the electric wires L1 to L3 connected to the secondary circuit 51 of the transformer and the ground from the current detected by the current sensor 14. The resistance Rg and the capacitance Cg are calculated. This calculation is based on the phase difference between the phase of the superimposed voltage V1 superimposed on the B-type ground line 11 from the signal generator 13 and the phase of the current having the same frequency as the superimposed voltage V1 detected by the current sensor 14. Rg and capacitance Cg are calculated.

ステップS12において、制御器15は、ステップS11の処理で算出した地絡抵抗Rgが予め設定した閾値抵抗Rth以下であるか否かを判断する。そして、地絡抵抗Rgが閾値抵抗Rthよりも大きい場合には(ステップS12でNO)、ステップS11に処理を戻す。一方、地絡抵抗Rgが閾値抵抗Rth以下である場合には(ステップS12でYES)、ステップS13において、制御器15は、各電線L1〜L3の地絡抵抗Rgが異常であり、漏電が発生しているものと判断する。   In step S12, the controller 15 determines whether or not the ground fault resistance Rg calculated in the process of step S11 is equal to or less than a preset threshold resistance Rth. If the ground fault resistance Rg is larger than the threshold resistance Rth (NO in step S12), the process returns to step S11. On the other hand, when the ground fault resistance Rg is equal to or less than the threshold resistance Rth (YES in step S12), in step S13, the controller 15 indicates that the ground fault resistance Rg of each of the electric wires L1 to L3 is abnormal, and leakage occurs. Judge that you are doing.

ステップS14において、制御器15は、切替スイッチSW1を閉塞から開放に切り替える。即ち、通常時においては、切替スイッチSW1は閉塞され、抑制抵抗rの両端が短絡されており、地絡抵抗Rgが小さくなった場合には、切替スイッチSW1を開放することにより、抑制抵抗rの両端を開放する。こうすることにより、図1に示すB種接地線11に抑制抵抗rが介置されることになり、該B種接地線11を流れる電流は、抑制抵抗rを流れることになる。従って、漏電の発生により、B種接地線11に過大な電流が流れることを抑制することができる。   In step S14, the controller 15 switches the changeover switch SW1 from closed to open. That is, at the normal time, the changeover switch SW1 is closed, both ends of the suppression resistor r are short-circuited, and when the ground fault resistance Rg becomes small, the changeover switch SW1 is opened to open the changeover resistor r1. Open both ends. By doing so, the suppression resistor r is interposed in the B-type ground line 11 shown in FIG. 1, and the current flowing through the B-type ground line 11 flows through the suppression resistor r. Therefore, it is possible to suppress an excessive current from flowing through the B-type ground line 11 due to the occurrence of electric leakage.

ステップS15において、制御器15は、Igr方式を用いて地絡抵抗Rg及び静電容量Cgを演算する。そして、上述したように、各電線L1〜L3とグランドとの間の静電容量C1〜C3は同一であるものと仮定しこれを「静電容量C」とするので、静電容量Cgに基づいて静電容量Cを求めることができる。また、一線地絡であると仮定するので、地絡した電線とグランドとの間の抵抗Rは、地絡抵抗Rgと見なすことができる。   In step S15, the controller 15 calculates the ground fault resistance Rg and the electrostatic capacitance Cg using the Igr method. And as above-mentioned, since it is assumed that the electrostatic capacitance C1-C3 between each electric wire L1-L3 and a ground is the same, and this is set to "electrostatic capacitance C", it is based on the electrostatic capacitance Cg. Thus, the capacitance C can be obtained. Moreover, since it is assumed that it is a one-line ground fault, the resistance R between the grounded electric wire and the ground can be regarded as the ground fault resistance Rg.

そして、ステップS16において、制御器15は、静電容量C、及び地絡抵抗Rgを用いて後述する手法により漏電電流を求める。   And in step S16, the controller 15 calculates | requires a leakage current with the method mentioned later using the electrostatic capacitance C and the ground fault resistance Rg.

ステップS17において、制御器15は、ステップS16の処理で演算した漏電電流が予め設定した基準値以上であるか否かを判断する。そして、基準値以上であると判断された場合には(ステップS17でYES)、ステップS18において、制御器15は、警報機(図示省略)により警報を出力することにより、漏電が発生していることをユーザ通知する。   In step S17, the controller 15 determines whether or not the leakage current calculated in the process of step S16 is greater than or equal to a preset reference value. And when it is judged that it is more than a standard value (it is YES at Step S17), in Step S18, controller 15 outputs an alarm by an alarm machine (illustration omitted), and electric leakage has occurred. This is notified to the user.

ステップS19において、制御器15は、地絡抵抗Rgが閾値抵抗Rth以上であるか否かを判断する。そして、閾値抵抗Rthを下回る場合にはステップS15に処理を戻し、閾値抵抗Rth以上である場合には、ステップS20において、制御器15は、切替スイッチSW1を閉塞する。こうして、電線L1〜L3にて地絡事故が発生し、地絡抵抗Rgが低下した場合には、B種接地線11に抑制抵抗rを介置することにより、漏電発生時にB種接地線11に過大な電流が流れることを防止することができる。これに加えて、漏電電流の検出を高精度に行うことが可能となる。   In step S19, the controller 15 determines whether or not the ground fault resistance Rg is greater than or equal to the threshold resistance Rth. If it is below the threshold resistance Rth, the process returns to step S15. If it is equal to or higher than the threshold resistance Rth, the controller 15 closes the changeover switch SW1 in step S20. In this way, when a ground fault occurs in the electric wires L1 to L3 and the ground fault resistance Rg is lowered, the suppression resistance r is interposed in the B type grounding wire 11, so that the B type grounding wire 11 is generated when a leakage occurs. It is possible to prevent an excessive current from flowing through. In addition to this, it is possible to detect the leakage current with high accuracy.

次に、図3のステップS16に示した漏電電流の演算方法について説明する。漏電電流の演算方法は、活性地絡の場合と中性線地絡の場合で異なる。以下、それぞれの場合について説明する。   Next, the calculation method of the leakage current shown in step S16 of FIG. 3 will be described. The calculation method of the leakage current is different between the case of the active ground fault and the case of the neutral ground fault. Hereinafter, each case will be described.

[活線が地絡した場合の漏電電流の演算方法]
図1にて説明したように、S相、R相、T相のそれぞれに接続される電線L1、L2、L3とグランドとの間には、抵抗R1、R2、R3、及び静電容量C1、C2、C3が存在する。そして、各電線L1〜L3のうち、活線である電線L3が地絡した場合には、図4に示す如くの等価回路となる。地絡していない電線L1,L2とグランドとの間の抵抗R1,R2は、抵抗値が無限大であるので、図4に記載していない。また、図4では地絡した電線L3とグランドとの間の抵抗R3を「R」で示している。
[Calculation method of earth leakage current in case of live ground fault]
As described with reference to FIG. 1, resistors R1, R2, R3, and capacitance C1, between the wires L1, L2, L3 connected to the S phase, R phase, and T phase, respectively, and the ground, C2 and C3 exist. And when the electric wire L3 which is a live wire among each electric wire L1-L3 has a ground fault, it becomes an equivalent circuit as shown in FIG. Resistances R1 and R2 between the ungrounded electric wires L1 and L2 and the ground are not shown in FIG. 4 because the resistance values are infinite. In FIG. 4, the resistance R3 between the grounded electric wire L3 and the ground is indicated by “R”.

そして、抵抗Rに流れる電流をI1、コンデンサC3,C2,C1に流れる電流をそれぞれI2,I3,I5とし、抑制抵抗rに流れる電流をI4とする。また、R相の電圧をEa、T相の電圧をEbとすると、電圧Ea,Ebは下記の(1)、(2)式で示すことができる。また、グランドの電圧をExとする。   The current flowing through the resistor R is I1, the currents flowing through the capacitors C3, C2, and C1 are I2, I3, and I5, respectively, and the current that flows through the suppression resistor r is I4. Further, assuming that the R-phase voltage is Ea and the T-phase voltage is Eb, the voltages Ea and Eb can be expressed by the following equations (1) and (2). Also, let the ground voltage be Ex.

Figure 2015206741
Figure 2015206741

Figure 2015206741
すると、図4に示す電流I1について下記(3)式が成立し、I2について下記(4)式が成立し、電流I3について下記(5)式が成立し、I4について下記(6)式が成立し、I5について下記(7)式が成立する。
Figure 2015206741
Then, the following equation (3) is established for the current I1 shown in FIG. 4, the following equation (4) is established for I2, the following equation (5) is established for the current I3, and the following equation (6) is established for I4: Then, the following equation (7) is established for I5.

Figure 2015206741
Figure 2015206741

Figure 2015206741
Figure 2015206741

Figure 2015206741
Figure 2015206741

Figure 2015206741
Figure 2015206741

Figure 2015206741
更に、電流I1〜I5について、下記(8)式が成立する。
Figure 2015206741
Further, the following formula (8) is established for the currents I1 to I5.

I1+I2+I3=I4+I5 …(8)
(8)式に上記した(3)〜(7)式を代入すると、下記(9)式が得られる。
I1 + I2 + I3 = I4 + I5 (8)
Substituting the above equations (3) to (7) into the equation (8), the following equation (9) is obtained.

Figure 2015206741
(9)式から電圧Exを求めると、下記(10)式となる。
Figure 2015206741
When the voltage Ex is obtained from the equation (9), the following equation (10) is obtained.

Figure 2015206741
(10)式を前述の(6)式に代入すると、下記(11)式が得られる。
Figure 2015206741
Substituting equation (10) into equation (6) above yields equation (11) below.

Figure 2015206741
即ち、抑制抵抗rに流れる電流I4は(11)式で示される。また、(10)式を前述の(3)式に代入すると、下記(12)式が得られる。
Figure 2015206741
That is, the current I4 flowing through the suppression resistor r is expressed by equation (11). Further, when the formula (10) is substituted into the above-described formula (3), the following formula (12) is obtained.

Figure 2015206741
即ち、抵抗Rに流れる電流I1、即ち電線L3が地絡することによって流れる漏電電流I1は、(12)式で示される。そして、(12)式で用いている各数値Ea、Eb、C、r、Rは全て既知であるから、(12)式を用いることにより、抑制抵抗rが介置された場合でも、活線地絡が発生した場合の漏電電流I1を精度良く算出することができる。
Figure 2015206741
That is, the current I1 that flows through the resistor R, that is, the leakage current I1 that flows when the electric wire L3 is grounded is expressed by the following equation (12). Since all the numerical values Ea, Eb, C, r, and R used in the equation (12) are already known, even if the suppression resistor r is interposed by using the equation (12), It is possible to accurately calculate the leakage current I1 when a ground fault occurs.

[中性線が地絡した場合の漏電電流の演算方法]
図1にて説明したように、S相、R相、T相のそれぞれに接続される電線L1、L2、L3とグランドとの間には、抵抗R1、R2、R3、及び静電容量C1、C2、C3が存在する。そして、図1に示した各電線L1〜L3のうち、中性線である電線L1が地絡した場合には、図5に示す如くの等価回路となる。地絡していない電線L2,L3とグランドとの間の抵抗R2,R3は、抵抗値が無限大であるので、図5に記載していない。また、図5では地絡した電線L1とグランドとの間の抵抗R1を「R」で示している。
[Calculation method of leakage current when neutral wire is grounded]
As described with reference to FIG. 1, resistors R1, R2, R3, and capacitance C1, between the wires L1, L2, L3 connected to the S phase, R phase, and T phase, respectively, and the ground, C2 and C3 exist. And when the electric wire L1 which is a neutral wire among each electric wire L1-L3 shown in FIG. 1 has a ground fault, it becomes an equivalent circuit as shown in FIG. Resistances R2 and R3 between the ungrounded electric wires L2 and L3 and the ground are not shown in FIG. 5 because the resistance values are infinite. In FIG. 5, the resistance R1 between the grounded electric wire L1 and the ground is indicated by “R”.

そして、抵抗Rに流れる電流をI3、コンデンサC3,C2,C1に流れる電流をそれぞれI1,I2,I4とし、抑制抵抗rに流れる電流をI5とする。また、T相の電圧をEb、R相の電圧をEaとし、グランドの電圧をExとする。電圧Ea,Ebは前述した(1)、(2)式で示すことができる。   The current flowing through the resistor R is I3, the currents flowing through the capacitors C3, C2, and C1 are I1, I2, and I4, respectively, and the current that flows through the suppression resistor r is I5. The T-phase voltage is Eb, the R-phase voltage is Ea, and the ground voltage is Ex. The voltages Ea and Eb can be expressed by the above-described equations (1) and (2).

すると、図5に示す電流I1について下記(13)式が成立し、I2について下記(14)式が成立し、電流I3について下記(15)式が成立し、I4について下記(16)式が成立し、I5について下記(17)式が成立する。   Then, the following equation (13) is established for the current I1 shown in FIG. 5, the following equation (14) is established for I2, the following equation (15) is established for the current I3, and the following equation (16) is established for I4: The following equation (17) is established for I5.

Figure 2015206741
Figure 2015206741

Figure 2015206741
Figure 2015206741

Figure 2015206741
Figure 2015206741

Figure 2015206741
Figure 2015206741

Figure 2015206741
更に、電流I1〜I5について、下記(18)式が成立する。
Figure 2015206741
Furthermore, the following equation (18) is established for the currents I1 to I5.

I1+I2=I3+I4+I5 …(18)
(18)式に上記した(13)〜(17)式を代入すると、下記(19)式が得られる。
I1 + I2 = I3 + I4 + I5 (18)
Substituting the above equations (13) to (17) into the equation (18), the following equation (19) is obtained.

Figure 2015206741
(19)式から電圧Exを求めると、下記(20)式となる。
Figure 2015206741
When the voltage Ex is obtained from the equation (19), the following equation (20) is obtained.

Figure 2015206741
(20)式を前述の(17)式に代入すると、下記(21)式が得られる。
Figure 2015206741
Substituting the equation (20) into the above equation (17) yields the following equation (21).

Figure 2015206741
即ち、抑制抵抗rに流れる電流I5は(21)式で示される。また、(20)式を前述の(14)式に代入すると、下記(22)式が得られる。
Figure 2015206741
That is, the current I5 flowing through the suppression resistor r is expressed by equation (21). Further, when the equation (20) is substituted into the above equation (14), the following equation (22) is obtained.

Figure 2015206741
即ち、抵抗Rに流れる電流I3、即ち電線L1が地絡することによって流れる漏電電流はI3は、(22)式で示される。そして、(22)式で用いている各数値Ea、Eb、C、r、Rは全て既知であるから、(22)式を用いることにより、抑制抵抗rが介置された場合でも、中性線地絡が発生した場合の漏電電流I1を精度良く算出することができる。
Figure 2015206741
That is, the current I3 that flows through the resistor R, that is, the leakage current that flows when the electric wire L1 is grounded, is expressed by equation (22). Since all the numerical values Ea, Eb, C, r, and R used in the equation (22) are already known, even if the suppression resistor r is interposed by using the equation (22), the neutral value is neutral. It is possible to accurately calculate the leakage current I1 when a wire ground fault occurs.

そして、本実施形態では、前述した活線地絡の場合、及び中性線地絡の場合の双方について漏電電流を演算する。即ち、活線地絡の場合の漏電電流を第1漏電電流とし、中性線地絡の場合の漏電電流を第2漏電電流とし、第1漏電電流と第2漏電電流のうち大きい方の漏電電流が実際の漏電電流であるものと判断する。つまり、活線地絡の場合の上記(12)式で演算した電流I1、及び中性線地絡の場合の上記(22)式で演算した電流I3のうちの大きい方の電流を用いて、漏電電流を判断する。   In the present embodiment, the leakage current is calculated for both the above-described live wire ground fault and the neutral wire ground fault. That is, the leakage current in the case of a live line ground fault is the first leakage current, the leakage current in the case of a neutral line ground fault is the second leakage current, and the larger one of the first leakage current and the second leakage current. Judge that the current is the actual leakage current. That is, by using the larger current of the current I1 calculated by the above equation (12) in the case of a live wire ground fault and the current I3 calculated by the above equation (22) in the case of a neutral wire ground fault, Determine the leakage current.

このようにして、本実施形態に係る絶縁監視装置では、B種接地線11に流れる電流が大きくなった場合には、切替スイッチSW1を開放することにより、B種接地線11に抑制抵抗rを介置して過大な電流が流れることを阻止する。更に、制御器15は、二次側電線とグランドとの間の合計の静電容量Cgを演算し、更に、各電線L1〜L3とグランドとの間の静電容量C1〜C3が同一であると仮定して、この同一の静電容量Cを求める。そして、漏電の原因が一線地絡であると仮定して、上述したように連立方程式を設定して、地絡した電線に流れる漏電電流を算出する。従って、B種接地線11に抑制抵抗rが介置された場合でも、漏電電流を高精度に算出することが可能となる。   Thus, in the insulation monitoring apparatus according to the present embodiment, when the current flowing through the B-type ground line 11 becomes large, by opening the changeover switch SW1, the suppression resistor r is provided to the B-type ground line 11. This prevents an excessive current from flowing. Further, the controller 15 calculates the total capacitance Cg between the secondary side electric wire and the ground, and furthermore, the capacitances C1 to C3 between the electric wires L1 to L3 and the ground are the same. Assuming that, the same capacitance C is obtained. Then, assuming that the cause of the leakage is a one-line ground fault, simultaneous equations are set as described above, and the leakage current flowing through the grounded electric wire is calculated. Therefore, even when the suppression resistor r is interposed in the B-type ground line 11, the leakage current can be calculated with high accuracy.

また、地絡が発生した際には、活線地絡の場合、及び中性線地絡の場合の双方について漏電電流を算出し、このうち大きい方の漏電電流を採用する。従って、活線地絡、及び中性線地絡のいずれが発生した場合においても、高精度な漏電電流の算出が可能となる。   In addition, when a ground fault occurs, the leakage current is calculated for both a live-line ground fault and a neutral-line ground fault, and the larger one of these is adopted. Therefore, even when either a live wire ground fault or a neutral wire ground fault occurs, it is possible to calculate the leakage current with high accuracy.

なお、第1実施形態では、(1)式、(2)式に示したように、電圧Ea、Ebが200Vである例について説明したが、本発明はこれに限定されず、例えば、400V等の他の電圧とすることも可能である。   In the first embodiment, as shown in the formulas (1) and (2), the example in which the voltages Ea and Eb are 200V has been described. However, the present invention is not limited to this, and for example, 400V or the like. Other voltages can also be used.

[第2実施形態の説明]
次に、本発明の第2実施形態について説明する。図6は、本発明の第2実施形態に係る絶縁監視装置の構成を示す回路図である。図6に示すように、第2実施形態は、変圧器の二次側回路52が単相3線結線とされている。即ち、変圧器の二次側回路52の中間点が電線L11に接続され2つの端部がそれぞれ電線L12,L13に接続されている。また、二次側回路52の中間点にはB種接地線11が接続されている。それ以外の構成は、前述した図1と同一であるので構成説明を省略する。
[Description of Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 6 is a circuit diagram showing a configuration of an insulation monitoring apparatus according to the second embodiment of the present invention. As shown in FIG. 6, in the second embodiment, the secondary circuit 52 of the transformer is a single-phase three-wire connection. That is, the intermediate point of the secondary circuit 52 of the transformer is connected to the electric wire L11, and the two ends are connected to the electric wires L12 and L13, respectively. In addition, a B-type ground line 11 is connected to an intermediate point of the secondary side circuit 52. Since the other configuration is the same as that of FIG. 1 described above, the description of the configuration is omitted.

そして、第2実施形態では、図4、図5に示した電圧EaとEbが逆位相となる。即ち、Ea=−Ebの関係となる。それ以外の演算方法は、前述した第1実施形態と同様である。従って、前述した(12)式にて用いるEaをEa=−Eb、またはEbをEb=−Eaと置き換えることにより、活線地絡が発生したときの漏電電流I1を演算することができる。   In the second embodiment, the voltages Ea and Eb shown in FIGS. 4 and 5 are in opposite phases. That is, Ea = −Eb. The other calculation method is the same as that of the first embodiment described above. Therefore, by replacing Ea used in the above-described equation (12) with Ea = −Eb, or Eb with Eb = −Ea, it is possible to calculate the leakage current I1 when a live line ground fault occurs.

同様に前述した(22)式にて用いるEaをEa=−Eb、またはEbをEb=−Eaと置き換えることにより、中性線地絡が発生したときの漏電電流I3を演算することができる。   Similarly, by replacing Ea used in the above-described equation (22) with Ea = −Eb or Eb with Eb = −Ea, it is possible to calculate the leakage current I3 when a neutral ground fault occurs.

このようにして、第2実施形態では、単相3線式回路にて、B種接地線11に抑制抵抗rを介置した場合においても、前述した第1実施形態と同様に、漏電電流を高精度に演算することが可能となる。   Thus, in the second embodiment, even in the case where the suppression resistor r is interposed in the B-type ground line 11 in the single-phase three-wire circuit, the leakage current is reduced as in the first embodiment described above. It is possible to calculate with high accuracy.

以上、本発明の絶縁監視装置を図示の実施形態に基づいて説明したが、本発明はこれに限定されるものではなく、各部の構成は、同様の機能を有する任意の構成のものに置き換えることができる。   As described above, the insulation monitoring device of the present invention has been described based on the illustrated embodiment. However, the present invention is not limited to this, and the configuration of each part is replaced with an arbitrary configuration having the same function. Can do.

11 B種接地線
12 並列接続回路
13 信号発生器(監視信号発生器)
14 電流センサ(電流検出手段)
15 制御器(抵抗・静電容量算出手段、切替制御手段、電流算出手段)
21 保護回路
51 二次側回路
52 二次側回路
101 B種接地線
102 制御器
103 信号発生器
104 スイッチ
105 電流検出器
110 変圧器
111 電線
112 電線
r 抑制抵抗
SW1 切替スイッチ
11 B class grounding line 12 Parallel connection circuit 13 Signal generator (monitor signal generator)
14 Current sensor (current detection means)
15 Controller (resistance / capacitance calculation means, switching control means, current calculation means)
21 protection circuit 51 secondary side circuit 52 secondary side circuit 101 class B ground wire 102 controller 103 signal generator 104 switch 105 current detector 110 transformer 111 electric wire 112 electric wire r suppression resistance SW1 changeover switch

Claims (4)

変圧器のB種接地線に、商用周波数と異なる特定周波数の監視信号を重畳する監視信号発生器と、
前記B種接地線に流れる電流に含まれる前記特定周波数の電流を検出する電流検出手段と、
前記特定周波数の電流の有効成分及び無効成分に基づいて、前記変圧器の二次側電線の地絡抵抗、及び静電容量を求める抵抗・静電容量算出手段と、
前記B種接地線に設けられ、抑制抵抗と、該抑制抵抗の両端の短絡、開放を切り替える切替スイッチと、が並列接続された並列接続回路と、
前記地絡抵抗が閾値抵抗を上回る場合には前記抑制抵抗の両端を短絡し、前記地絡抵抗が前記閾値抵抗よりも小さい場合には前記抑制抵抗の両端を開放するように前記切替スイッチを制御する切替制御手段と、
前記抑制抵抗の両端が開放された際には、前記二次側電線に一線地絡が生じたものと判断し、且つ、各二次側電線とグランドとの間の静電容量が同一であると仮定して、前記一線地絡による漏電電流を算出する電流演算手段と、
を備えたことを特徴とする絶縁監視装置。
A supervisory signal generator that superimposes a supervisory signal of a specific frequency different from the commercial frequency on the class B ground wire of the transformer;
Current detection means for detecting a current of the specific frequency included in the current flowing in the B-type ground line;
Based on the effective component and the ineffective component of the current of the specific frequency, the ground fault resistance of the secondary side electric wire of the transformer, and a resistance / capacitance calculation means for obtaining the capacitance
A parallel connection circuit in which the suppression resistor and a changeover switch that switches between short-circuiting and opening of both ends of the suppression resistor are connected in parallel;
When the ground fault resistance exceeds a threshold resistance, both ends of the suppression resistor are short-circuited, and when the ground fault resistance is smaller than the threshold resistance, the changeover switch is controlled to open both ends of the suppression resistance. Switching control means for
When both ends of the suppression resistor are opened, it is determined that a single-wire ground fault has occurred in the secondary-side wire, and the capacitance between each secondary-side wire and the ground is the same. Assuming that, current calculation means for calculating a leakage current due to the one-line ground fault,
An insulation monitoring device comprising:
前記電流演算手段は、前記B種接地線に接続されない活線が地絡したと仮定して第1漏電電流を演算し、前記B種接地線に接続された中性線が地絡したと仮定して第2漏電電流を演算し、前記第1漏電電流と第2漏電電流のうち、大きい方の電流を漏電電流として採用することを特徴とする請求項1に記載の絶縁監視装置。   The current calculation means calculates a first leakage current on the assumption that a live wire not connected to the class B ground wire has a ground fault, and assumes that a neutral wire connected to the class B ground wire has a ground fault. Then, the second leakage current is calculated, and the larger one of the first leakage current and the second leakage current is employed as the leakage current. 前記変圧器の二次側は、R相、S相、T相の3相デルタ結線であり、このうち1つの相に接続される電線を前記中性線とし、他の2つの相に接続される電線を前記活線とすることを特徴とする請求項2に記載の絶縁監視装置。   The secondary side of the transformer is a R-phase, S-phase, and T-phase three-phase delta connection, of which the wire connected to one phase is the neutral wire and is connected to the other two phases. The insulation monitoring apparatus according to claim 2, wherein the electric wire is a live wire. 前記変圧器の二次側は、単相3線結線であり、該単相3線結線の2つの端部に接続される各電線を前記活線とし、中間点に接続される電線を中性線とすることを特徴とする請求項2に記載の絶縁監視装置。   The secondary side of the transformer is a single-phase three-wire connection, each wire connected to the two ends of the single-phase three-wire connection is the live wire, and the wire connected to the intermediate point is neutral The insulation monitoring device according to claim 2, wherein the insulation monitoring device is a wire.
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CN110794332A (en) * 2019-11-14 2020-02-14 浙江晨泰科技股份有限公司 Residual current transformer detection system for fire detection detector and detection method thereof
JP7480445B1 (en) 2022-12-21 2024-05-10 一般財団法人関東電気保安協会 Insulation monitoring device
JP7480444B1 (en) 2022-12-21 2024-05-10 一般財団法人関東電気保安協会 Insulation monitoring system and insulation monitoring method

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