JP2010273478A

JP2010273478A - Method and system for detection of line-to-ground fault in dc and ac circuit

Info

Publication number: JP2010273478A
Application number: JP2009124294A
Authority: JP
Inventors: Takashi Ganji; 崇元治; Shigeo Matsuoka; 樹生松岡; Shu Nakamura; 脩中村; Masanori Ota; 正徳太田
Original assignee: Kansai Electric Power Co Inc; Hasegawa Electric Co Ltd
Current assignee: Kansai Electric Power Co Inc; Hasegawa Electric Co Ltd
Priority date: 2009-05-22
Filing date: 2009-05-22
Publication date: 2010-12-02

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and system for detection of line-to-ground faults in DC and AC circuits, for facilitating the cost reduction of the whole line-to-ground fault protection system of an AC circuit and a DC circuit in an AC/DC power distribution system. <P>SOLUTION: The method is used for detecting a line-to-ground fault accident of a DC circuit 30 on the basis of a change in excitation current i of a zero-phase transformer 41 for an AC line-to-ground fault. The DC circuit 30 is connected to a secondary-side non-grounding system AC circuit 10 of a main transformer 1. The zero-phase transformer 41 for an AC line-to-ground fault is arranged as an AC line-to-ground fault sensor 40b on the side of the AC circuit 10. A phase current transformer CT1 is installed on the primary side of the zero-phase transformer 41. The phase current transformer CT1 measures a primary-side excitation current of the zero-phase transformer. The change in excitation current i, displaced to the side of the DC circuit when the DC line-to-ground fault accident occurs, is detected by a data arithmetic processing part 81 so as to subject the change to arithmetic processing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、工場変圧器などの主変圧器二次側の非接地系交流回路に整流器を介して直流回路を接続した非接地系交流回路における直流・交流回路地絡検出方法および直流・交流回路地絡検出システムに関する。 The present invention relates to a DC / AC circuit ground fault detection method and a DC / AC circuit in a non-grounded AC circuit in which a DC circuit is connected to a non-grounded AC circuit on the secondary side of a main transformer such as a factory transformer via a rectifier. The present invention relates to a ground fault detection system.

一次側配電線路の三相交流を電力需要家の主変圧器で変圧し、三相整流器で整流して直流負荷に給電する交直配電系統は、主変圧器二次側に非接地系交流回路を備える。非接地系交流回路は、非接地三相交流回路、この非接地三相交流回路に準じる高抵抗接地三相交流回路である。非接地系交流回路に三相整流器を介して接続される直流回路に直流負荷が設置される。このような交直配電系統においては、交流回路側を非接地系にすることで、交流側地絡の事故電流を小さく抑制する。また、通常は交流回路側に交流地絡を検出する交流地絡センサが常設され、この交流地絡センサは等価的に高抵抗を挿入した状態で接地される。また、直流回路側には必要に応じて直流地絡を検出する直流地絡センサ（例えば、特許文献１参照）が配設される。 The AC / DC distribution system that transforms the three-phase AC of the primary distribution line with the main transformer of the power consumer, rectifies it with the three-phase rectifier, and supplies the DC load with the ungrounded AC circuit on the secondary side of the main transformer. Prepare. The non-grounded AC circuit is a non-grounded three-phase AC circuit and a high-resistance grounded three-phase AC circuit according to the non-grounded three-phase AC circuit. A DC load is installed in a DC circuit connected to the non-grounded AC circuit via a three-phase rectifier. In such an AC / DC power distribution system, the AC circuit side is set to a non-grounded system, so that the fault current of the AC side ground fault is suppressed to be small. Further, normally, an AC ground fault sensor for detecting an AC ground fault is permanently installed on the AC circuit side, and this AC ground fault sensor is grounded in a state where a high resistance is equivalently inserted. Further, a DC ground fault sensor (for example, see Patent Document 1) that detects a DC ground fault is disposed on the DC circuit side as necessary.

図８に示す交直配電系統は、主変圧器１の二次側の非接地系交流回路１０に交流地絡センサ４０ａを設置し、直流回路３０に直流地絡センサ７０ａを設置している。交流回路１０の三相三線それぞれに遮断器１１が介挿され、三相三線それぞれは対地静電容量Ｃｏを有する。交流回路１０にダイオードブリッジの三相整流器２０を介し直流回路３０を接続し、直流回路３０の正極端子３１と負極端子３２に直流負荷３３を接続する。 In the AC / DC power distribution system shown in FIG. 8, an AC ground fault sensor 40 a is installed in the non-grounded AC circuit 10 on the secondary side of the main transformer 1, and a DC ground fault sensor 70 a is installed in the DC circuit 30. The circuit breaker 11 is inserted in each of the three-phase three-wires of the AC circuit 10, and each of the three-phase three-wires has a ground capacitance Co. A DC circuit 30 is connected to the AC circuit 10 via a diode bridge three-phase rectifier 20, and a DC load 33 is connected to the positive terminal 31 and the negative terminal 32 of the DC circuit 30.

交流地絡センサ４０ａは、図８に示す零相変圧器（ＥＶＴ）を使用した様式と、図７で後述する零相電圧分圧器（ＺＰＤ）を使用した様式が一般的である。図８の交流地絡センサ４０ａは、主変圧器１の二次側三相三線に接続した零相変圧器（ＥＶＴ）４１と、零相変圧器４１の中性点接地線４２に流れる零相電流を検出する零相変流器（ＺＣＴ）４３を備えるが、いずれか一方を備えればよい。零相変圧器４１の一次側がＥＶＴ保護ヒューズＦを介して主変圧器二次側に接続される。零相変圧器４１の三次側に交流電流制限抵抗４５を介して交流地絡継電器４６が接続される。交流回路１０のいずれか一端子に地絡事故が発生すると、零相変圧器４１の中性点接地線４２に零相電流Ｉｏが流れ、これを零相変流器４３に接続された地絡継電器４４が検出する。地絡継電器４４は、零相電流Ｉｏを検出すると、交流地絡発生のアラーム等の表示を行い、必要に応じて遮断器１１を開いて交流回路１０を保護する。又は、地絡継電器４６が零相電圧Ｖｏを検出して、交流回路１０を保護する。地絡継電器４６の交流電流制限抵抗４５は、零相変圧器４１に流れる零相電流Ｉｏを抑制して、零相変圧器４１の過負荷を防止する。 The AC ground fault sensor 40a is generally in a mode using a zero phase transformer (EVT) shown in FIG. 8 and a mode using a zero phase voltage divider (ZPD) described later in FIG. The AC ground fault sensor 40a of FIG. 8 includes a zero-phase transformer (EVT) 41 connected to the secondary-side three-phase three-wire of the main transformer 1 and a zero-phase flowing through the neutral point ground line 42 of the zero-phase transformer 41. Although a zero-phase current transformer (ZCT) 43 for detecting current is provided, either one may be provided. The primary side of the zero-phase transformer 41 is connected to the secondary side of the main transformer via the EVT protection fuse F. An AC ground fault relay 46 is connected to the tertiary side of the zero-phase transformer 41 via an AC current limiting resistor 45. When a ground fault occurs at any one terminal of the AC circuit 10, a zero-phase current Io flows through the neutral ground line 42 of the zero-phase transformer 41, and this is connected to the zero-phase current transformer 43. The relay 44 detects. When detecting the zero-phase current Io, the ground fault relay 44 displays an AC ground fault alarm or the like, and opens the circuit breaker 11 to protect the AC circuit 10 as necessary. Alternatively, the ground fault relay 46 detects the zero-phase voltage Vo and protects the AC circuit 10. The alternating current limiting resistor 45 of the ground fault relay 46 suppresses the zero-phase current Io flowing through the zero-phase transformer 41 and prevents the zero-phase transformer 41 from being overloaded.

直流回路３０は、三相整流器２０で整流された直流電圧を平滑する平滑リアクトル３４と平滑コンデンサ３５を備える。平滑コンデンサ３５に並列的に直流地絡センサ７０ａが設置される。直流地絡センサ７０ａは、直流回路３０の正極側または負極側で地絡した直流地絡電流Ｉｄｇを検出する地絡検出器や、この地絡検出器の地絡電流検出信号に基づいてアラームを発生させ、必要に応じて直流回路３０を開回路に制御する駆動制御器などを備える。直流地絡センサ７０ａが直流地絡電流Ｉｄｇを検出して、直流回路３０を開回路に制御すると、直流地絡電流が無くなり、直流回路３０が自己の地絡事故から保護されると共に、交流回路１０への波及が防止される。 The DC circuit 30 includes a smoothing reactor 34 and a smoothing capacitor 35 that smooth the DC voltage rectified by the three-phase rectifier 20. A DC ground fault sensor 70 a is installed in parallel with the smoothing capacitor 35. The DC ground fault sensor 70a is configured to detect an alarm based on a ground fault detector that detects a DC ground fault current Idg that is grounded on the positive electrode side or the negative electrode side of the DC circuit 30, and a ground fault current detection signal of the ground fault detector. And a drive controller for controlling the DC circuit 30 to be an open circuit. When the DC ground fault sensor 70a detects the DC ground fault current Idg and controls the DC circuit 30 to be an open circuit, the DC ground fault current disappears, the DC circuit 30 is protected from its own ground fault, and the AC circuit Ripple to 10 is prevented.

特開２００５−１３７０９５号公報JP 2005-137095 A

図８のような交直配電系統に設置される交流回路側の交流地絡センサと直流回路側の直流地絡センサそれぞれは、対応する交流回路、直流回路を地絡事故から保護するが、このような各地絡センサは大型化し、高価である。特に、直流地絡センサが高価であり、交直配電系統の地絡保護システム全体を高価なものにしている。また、共通の交流回路に複数の直流回路を接続した配電系統においては、複数の直流回路それぞれに高価な直流地絡センサを配備することが設備投資的に難しい。 Although each of the AC ground fault sensor on the AC circuit side and the DC ground fault sensor on the DC circuit side installed in the AC / DC power distribution system as shown in FIG. 8 protects the corresponding AC circuit and DC circuit from a ground fault, Such local fault sensors are large and expensive. In particular, the DC ground fault sensor is expensive, making the entire ground fault protection system of the AC / DC power distribution system expensive. In a distribution system in which a plurality of DC circuits are connected to a common AC circuit, it is difficult to install an expensive DC ground fault sensor in each of the plurality of DC circuits.

また、直流回路の直流地絡センサには、地絡事故検出の際にアラームのみを出して、交流回路から直流回路への給電を継続させ、直流回路の停電を回避するように機能するものがある。さらに、共通の交流回路に接続された複数の直流回路の中には、直流地絡センサを配備しない直流回路がある。前者のような直流地絡センサを有する直流回路や、後者のような直流地絡センサを装備しない直流回路に直流地絡事故が発生すると、交流回路側にも直流地絡電流が流れて、次の不具合が発生することがある。 In addition, some DC ground fault sensors of DC circuits function so that only an alarm is issued when a ground fault is detected, power supply from the AC circuit to the DC circuit is continued, and a power failure of the DC circuit is avoided. is there. Further, among a plurality of DC circuits connected to a common AC circuit, there is a DC circuit in which no DC ground fault sensor is provided. When a DC ground fault occurs in a DC circuit having a DC ground fault sensor such as the former or in a DC circuit that is not equipped with a DC ground fault sensor such as the latter, a DC ground fault current also flows to the AC circuit side. May occur.

例えば、図８の直流回路３０に示すように、負極側で直流地絡が発生すると、平滑コンデンサ３５の平滑直流電圧が電池電圧となり、交流回路１０の三相三線の対地静電容量Ｃｏと零相変圧器４１の中性点接地線４２を経由して、図８の破線矢印方向に直流地絡電流Ｉｄｇが流れる。また、直流回路３０の正極側で直流地絡が発生すると、図８の破線矢印方向と反対方向に直流地絡電流Ｉｄｇが流れる。この直流地絡電流Ｉｄｇが零相変圧器４１の鉄心を直流偏磁させて、ＥＶＴ励磁電流が過大になると、ＥＶＴ保護ヒューズＦが溶断して交流地絡センサが機能しなくなることがある。また、ヒューズ溶断がない場合は、過大な励磁電流と直流地絡電流Ｉｄｇの継続した流れで、零相変圧器焼損に至る可能性が生じる。そのため、交流地絡センサ側に直流地絡電流対策が必要となり、交流地絡センサが更に高価になり、地絡保護システム全体が尚更に高価になる不具合があった。 For example, as shown in the DC circuit 30 of FIG. 8, when a DC ground fault occurs on the negative electrode side, the smoothing DC voltage of the smoothing capacitor 35 becomes the battery voltage, and the three-phase three-wire ground capacitance Co of the AC circuit 10 and zero A DC ground fault current Idg flows in the direction of the broken line arrow in FIG. 8 via the neutral point ground line 42 of the phase transformer 41. Further, when a DC ground fault occurs on the positive electrode side of the DC circuit 30, a DC ground fault current Idg flows in the direction opposite to the direction of the broken line arrow in FIG. If this DC ground fault current Idg causes the iron core of the zero-phase transformer 41 to be DC biased and the EVT excitation current becomes excessive, the EVT protection fuse F may melt and the AC ground fault sensor may not function. Further, when the fuse is not blown, there is a possibility that the zero-phase transformer will be burned by the continuous flow of excessive excitation current and DC ground fault current Idg. For this reason, it is necessary to take measures against a DC ground fault current on the AC ground fault sensor side, the AC ground fault sensor becomes more expensive, and the entire ground fault protection system becomes even more expensive.

本発明の目的とするところは、交直配電系統全体の地絡保護システムのコスト低減を容易にする直流・交流回路地絡検出方法と地絡検出システムを提供することにある。 An object of the present invention is to provide a DC / AC circuit ground fault detection method and a ground fault detection system that facilitate the cost reduction of the ground fault protection system for the entire AC / DC power distribution system.

上記目的を達成する本発明方法は、主変圧器二次側の非接地系交流回路に接続された直流回路の地絡事故を、交流回路側に交流地絡センサとして配設した交流地絡用零相変圧器の励磁電流の変化により検出することを特徴とする。 The method of the present invention to achieve the above object is for an AC ground fault in which a ground fault of a DC circuit connected to an ungrounded AC circuit on the secondary side of the main transformer is arranged as an AC ground fault sensor on the AC circuit side. It is detected by a change in the excitation current of the zero-phase transformer.

ここで、非接地系交流回路は、零相変圧器（ＥＶＴ）や零相変流器（ＺＣＴ）を備えた交流地絡センサを有する非接地系三相交流回路の他、零相電圧分圧器（ＺＰＤ）の交流地絡センサを有する高抵抗接地回路にも適用できる。交流回路に配設する交流地絡センサは、図８の既存の交流地絡用零相変圧器４１を使用したものが適用でき、または、後述する交流地絡用零相電圧分圧器（ＺＰＤ）を使用したものが適用できる。直流回路側に地絡事故が発生すると、大地を経由することで交流回路の交流地絡センサに直流地絡電流Ｉｄｇが流れる。この直流地絡電流Ｉｄｇで、交流地絡センサとしての零相変圧器（以下、必要に応じＥＶＴと称す）の鉄心が直流偏磁しＥＶＴの励磁電流が変化し、交流地絡センサの様々な導電箇所に電磁気的変位が生じる。そこで、直流地絡事故時のＥＶＴ励磁電流の変化を検出して、直流回路側の地絡事故発生を検出する。このように交流回路の交流地絡センサ側で直流回路側の地絡事故発生を検出することで、直流回路側に高価な直流地絡センサを配備しなくても、直流地絡事故に対する保護対策が低コストで実行できる。また、直流地絡事故時の交流回路側への波及が防止でき、交流と直流の両地絡保護システムのコスト低減が容易になる。 Here, the ungrounded AC circuit includes a non-grounded three-phase AC circuit having an AC ground fault sensor having a zero-phase transformer (EVT) and a zero-phase current transformer (ZCT), and a zero-phase voltage divider. The present invention can also be applied to a high resistance grounding circuit having a (ZPD) AC ground fault sensor. As the AC ground fault sensor disposed in the AC circuit, one using the existing AC ground fault zero-phase transformer 41 of FIG. 8 can be applied, or a zero-phase voltage divider (ZPD) for AC ground fault described later. The one using can be applied. When a ground fault occurs on the DC circuit side, a DC ground fault current Idg flows to the AC ground fault sensor of the AC circuit through the ground. With this DC ground fault current Idg, the core of a zero-phase transformer (hereinafter referred to as EVT if necessary) as an AC ground fault sensor is DC biased, and the excitation current of the EVT changes. Electromagnetic displacement occurs in the conductive location. Therefore, a change in the EVT excitation current at the time of a DC ground fault is detected to detect the occurrence of a ground fault on the DC circuit side. In this way, by detecting the occurrence of a ground fault on the DC circuit side on the AC ground fault sensor side of the AC circuit, protection measures against DC ground fault accidents can be achieved without installing an expensive DC ground fault sensor on the DC circuit side. Can be executed at low cost. Further, it is possible to prevent the AC circuit from spreading to the AC circuit side at the time of a DC ground fault, and it is easy to reduce the cost of both AC and DC ground fault protection systems.

本発明方法においては、ＥＶＴの励磁電流をＥＶＴの一次側相に設置した相変流器により検出し、検出したＥＶＴ励磁電流の複数種類の特性項目の中の実効値の増加、波高値の増加、偶数調波の発生および増加、６ｎ±１次調波の増加の各特性項目の１項目以上で直流回路の地絡事故検出を行うことができる。 In the method of the present invention, the excitation current of the EVT is detected by a phase current transformer installed in the primary side phase of the EVT, and an increase in effective value and an increase in peak value among a plurality of characteristic items of the detected EVT excitation current are detected. It is possible to detect a ground fault in a DC circuit with one or more of the characteristic items of generation and increase of even harmonics and increase of 6n ± 1st harmonic.

ここで、ＥＶＴ励磁電流の特性項目である実効値の増加、波高値の増加、偶数調波の発生および増加、６ｎ±１次調波の増加のそれぞれは、直流地絡事故発生の検出に有効であり、正確に検出し易い電磁気的変位の特性項目である。これら複数種類の特性項目の内の少なくとも１項目の電磁気的変位を予め設定された閾値に基づいて検出すれば、確実性よく直流地絡発生を検出することができる。また、複数種類の特性項目それぞれで電磁気的変位の増加成分を検出するようにして、複数全ての特性項目で閾値以上の増加成分を検出した時点で地絡事故発生を検知するようにしてもよい。複数種類の特性項目のいずれの項目を適用するかは、発生する配電系統の様式、直流地絡事故の規模等を考慮して選定することができる。 Here, each of the increase in effective value, the increase in peak value, the generation and increase of even harmonics, and the increase of 6n ± 1st harmonic, which are characteristic items of EVT excitation current, are effective for detecting the occurrence of a DC ground fault. It is a characteristic item of electromagnetic displacement that is easy to detect accurately. If the electromagnetic displacement of at least one of these multiple types of characteristic items is detected based on a preset threshold value, the occurrence of a DC ground fault can be detected with certainty. Further, an increase component of electromagnetic displacement may be detected for each of a plurality of types of characteristic items, and occurrence of a ground fault may be detected when an increase component equal to or greater than a threshold value is detected for all of the plurality of characteristic items. . Which item of multiple types of characteristic items is to be applied can be selected in consideration of the type of distribution system to be generated, the scale of a DC ground fault, and the like.

また、本発明方法においては、相変流器の交流出力の正側波高値と負側波高値を比較し、正側波高値と負側波高値の差の増加分を検知することで、地絡事故検出を行うことができる。さらに、正側波高値と負側波高値の差の大きさから、直流回路での地絡抵抗値の大きさを検知することができる。 Further, in the method of the present invention, the positive side peak value and the negative side peak value of the alternating current output of the phase current transformer are compared, and an increase in the difference between the positive side peak value and the negative side peak value is detected. A fault detection can be performed. Furthermore, the magnitude of the ground fault resistance value in the DC circuit can be detected from the magnitude of the difference between the positive side peak value and the negative side peak value.

また、本発明方法においては、相変流器の交流出力の正側波高値と負側波高値の大小比較で、直流回路での地絡事故の極性を判定することができる。ここでの直流回路での地絡事故の極性は、直流回路にある正極電路と負極電路である。この正極電路と負極電路の一方で直流地絡事故が発生した場合、相変流器の交流出力の正側波高値と負側波高値のいずれが大きいかを比較すれば、相関関係から直流回路での地絡事故の極性が正極電路側か負極電路側かを判定することができる。 Further, in the method of the present invention, the polarity of the ground fault in the DC circuit can be determined by comparing the positive side peak value and the negative side peak value of the AC output of the phase current transformer. The polarity of the ground fault in the DC circuit here is the positive circuit and the negative circuit in the DC circuit. If a DC ground fault occurs on one of the positive and negative circuit, if the comparison is made between the positive side peak value and the negative side peak value of the AC output of the phase current transformer, the DC circuit It is possible to determine whether the polarity of the ground fault at the positive electrode circuit side or the negative electrode circuit side.

本発明においては、相変流器の交流出力の正側波高値と負側波高値の測定を、相変流器の出力端子に接続した正負それぞれの半波整流回路の電圧出力の測定で行うことができる。このように、相変流器の交流出力を半波整流して、交流出力の正側波形のみから正側波高値を算出し、負側波形のみから負側波高値を算出することで、正確な波高値測定ができ、正側波高値と負側波高値の比較演算による直流地絡事故の検出、地絡抵抗値の測定、地絡事故の極性判定などを高精度で行うことが容易になる。 In the present invention, the measurement of the positive side peak value and the negative side peak value of the AC output of the phase current transformer is performed by measuring the voltage outputs of the positive and negative half-wave rectifier circuits connected to the output terminal of the phase current transformer. be able to. In this way, the AC output of the phase current transformer is half-wave rectified, the positive side peak value is calculated only from the positive side waveform of the AC output, and the negative side peak value is calculated only from the negative side waveform. It is easy to perform high-accuracy measurement of DC ground faults, measurement of ground fault resistance, polarity determination of ground faults, etc. by comparing the positive and negative peak values. Become.

さらに、本発明においては、直流地絡事故に伴うＥＶＴ励磁電流の変化は、ＥＶＴの中性点接地線に設置した中性点変流器による３ｎ次調波電流の増加により検出することができる。直流回路側で直流地絡事故が発生したときのＥＶＴ励磁電流は、中性点接地線に流れる交流電流成分の３ｎ次調波の増加として現れる。したがって、中性点変流器で検出した交流電流の３ｎ次調波電流の増加成分を閾値に基づいて判定することで、直流回路側の地絡事故発生を検出することができる。 Furthermore, in the present invention, the change in the EVT excitation current due to the DC ground fault can be detected by the increase of the 3n-order harmonic current by the neutral point current transformer installed on the neutral point grounding line of the EVT. . The EVT excitation current when a DC ground fault occurs on the DC circuit side appears as an increase in the 3n-order harmonic of the AC current component flowing through the neutral point ground line. Therefore, it is possible to detect the occurrence of a ground fault on the DC circuit side by determining the increase component of the 3n-order harmonic current of the AC current detected by the neutral point current transformer based on the threshold value.

また、上記目的を達成する本発明方法は、主変圧器の二次側の非接地系交流回路に接続された直流回路の地絡事故を、交流回路側に交流地絡センサとして配設した交流地絡用ＥＶＴの三次巻線の３ｎ次調波電圧の変化により検出することを特徴とする。 In addition, the method of the present invention for achieving the above object is the AC circuit in which the ground fault of the DC circuit connected to the non-grounded AC circuit on the secondary side of the main transformer is arranged as an AC ground fault sensor on the AC circuit side. It is detected by a change in the 3n-order harmonic voltage of the tertiary winding of the ground fault EVT.

ここで、直流回路側で直流地絡事故が発生してＥＶＴ側に直流地絡電流Ｉｄｇが流れると、ＥＶＴの励磁電流が変化すると共に、交流地絡センサの様々な導電箇所に電磁気的変位が生じる。この電磁気的変位の１つが、ＥＶＴの三次巻線の３ｎ次調波電圧の変化であり、この変化をＥＶＴ励磁電流の変化に代わり検出することで、直流回路側の地絡事故発生を検出することができる。また、ＥＶＴの三次巻線の３ｎ次調波電圧の変化とＥＶＴ励磁電流の変化を共に検出するようにして、直流地絡事故発生を検知することもできる。 Here, when a DC ground fault occurs on the DC circuit side and a DC ground fault current Idg flows on the EVT side, the excitation current of the EVT changes, and electromagnetic displacement occurs at various conductive locations of the AC ground fault sensor. Arise. One of the electromagnetic displacements is a change in the 3n-order harmonic voltage of the EVT tertiary winding. By detecting this change in place of the change in the EVT excitation current, the occurrence of a ground fault on the DC circuit side is detected. be able to. It is also possible to detect the occurrence of a DC ground fault by detecting both the change in the 3n-order harmonic voltage of the EVT tertiary winding and the change in the EVT excitation current.

さらに、本発明においては、ＥＶＴの中性点に直流阻止用コンデンサを入切可能に設置し、直流回路の地絡事故検出時に直流阻止用コンデンサを入状態にして中性点を直流阻止用コンデンサを介して接地することができる。この場合、ＥＶＴの中性点接地線に介挿した常閉の切換スイッチに直流阻止用コンデンサを並列接続すればよい。直流回路側に地絡事故が発生して、ＥＶＴの中性点接地線に直流地絡電流が流れた時点で、常閉の切換スイッチをオフに切り換え、中性点を直流阻止用コンデンサを介して接地する。このようにすれば、直流地絡事故発生直後に、直流地絡電流の流れがコンデンサで阻止されて、交流地絡センサのＥＶＴが直流地絡電流による偏磁から保護され、直流地絡センサとしての機能が安定する。 Further, in the present invention, the DC blocking capacitor is installed at the neutral point of the EVT so that it can be turned on and off, and when the ground fault of the DC circuit is detected, the DC blocking capacitor is turned on to set the neutral point to the DC blocking capacitor. Can be grounded. In this case, a DC blocking capacitor may be connected in parallel to a normally closed changeover switch inserted in the neutral point ground line of the EVT. When a ground fault occurs on the DC circuit side and a DC ground fault current flows through the neutral point grounding wire of the EVT, the normally closed changeover switch is turned off, and the neutral point is connected via the DC blocking capacitor. To ground. In this way, immediately after the occurrence of the DC ground fault, the flow of the DC ground fault current is blocked by the capacitor, and the EVT of the AC ground fault sensor is protected from the demagnetization due to the DC ground fault current. The function is stable.

また、上記目的を達成する本発明システムは、主変圧器二次側の非接地系交流回路に接続された直流回路の地絡事故を、交流回路側に交流地絡センサとして配設した零相電圧分圧器（ＺＰＤ）および交流回路側に直流地絡センサとして配設したＥＶＴの励磁電流の変化により検出する直流・交流回路地絡検出システムであって、直流回路の地絡事故による直流地絡電流を抑制する直流制限抵抗をＥＶＴの中性点に挿入し、または、ＥＶＴの一次側に、当該一次側を直流地絡事故時に交流回路から切り離す開閉手段を挿入したことを特徴とする。 The system of the present invention that achieves the above object is a zero-phase circuit in which a ground fault of a DC circuit connected to a non-grounded AC circuit on the secondary side of the main transformer is arranged as an AC ground fault sensor on the AC circuit side. A DC / AC circuit ground fault detection system for detecting a change in excitation current of an EVT arranged as a DC ground fault sensor on a voltage divider (ZPD) and an AC circuit side, and a DC ground fault due to a ground fault of the DC circuit A DC limiting resistor for suppressing current is inserted at the neutral point of the EVT, or switching means for separating the primary side from the AC circuit in the event of a DC ground fault is inserted on the primary side of the EVT.

このシステムは、交流回路側に零相電圧分圧器（ＺＰＤ）を交流地絡センサとして配設して、ＥＶＴを直流回路の直流地絡電流を交流回路側に流す直流地絡センサとして使用する。このシステムの場合、交流回路側に配設した直流地絡センサに直流制限抵抗を追加挿入してＥＶＴ励磁電流が過大になるのを防止する。さらに、直流地絡センサに直流地絡発生時に交流地絡センサから切り離す開閉手段を追加挿入して、ＥＶＴが過電流になるのを防止することができる。 In this system, a zero-phase voltage divider (ZPD) is arranged as an AC ground fault sensor on the AC circuit side, and the EVT is used as a DC ground fault sensor for passing a DC ground fault current of the DC circuit to the AC circuit side. In the case of this system, an additional DC limiting resistor is inserted into the DC ground fault sensor disposed on the AC circuit side to prevent the EVT excitation current from becoming excessive. Furthermore, it is possible to prevent the EVT from becoming an overcurrent by additionally inserting an opening / closing means for disconnecting the DC ground fault sensor from the AC ground fault sensor when a DC ground fault occurs.

本発明方法によれば、交流回路側に配設した交流地絡センサや、この交流地絡センサと同等な構成で交流回路側に配設した直流地絡センサで、直流回路側の直流地絡発生を検出し監視するようにしたので、直流回路側に高価な直流地絡センサを配備しなくても、直流地絡事故に対する保護対策が低コストで実行でき、直流地絡事故の交流回路側への波及が防止できて、交流と直流の両地絡保護システムのコスト低減が容易となる優れた効果を奏し得る。 According to the method of the present invention, an AC ground fault sensor disposed on the AC circuit side, or a DC ground fault sensor disposed on the AC circuit side with the same configuration as the AC ground fault sensor, the DC ground fault on the DC circuit side is provided. Since the occurrence is detected and monitored, protection measures against DC ground fault accidents can be implemented at low cost without installing an expensive DC ground fault sensor on the DC circuit side. It is possible to prevent the ripple from spreading to the outside, and it is possible to achieve an excellent effect of facilitating cost reduction of both the AC and DC ground fault protection systems.

本発明方法の実施の形態を示す配電系統の回路図である。It is a circuit diagram of a power distribution system showing an embodiment of the method of the present invention. 本発明方法を説明するためのＥＶＴ励磁電流の波形図および特性項目の図である。It is a wave form diagram of EVT excitation current for explaining the method of the present invention, and a figure of a characteristic item. 他の実施の形態を示す回路図である。It is a circuit diagram which shows other embodiment. 他の実施の形態を示す回路図である。It is a circuit diagram which shows other embodiment. 他の実施の形態を示す回路図である。It is a circuit diagram which shows other embodiment. 他の実施の形態を示す回路図である。It is a circuit diagram which shows other embodiment. 他の実施の形態を示す回路図である。It is a circuit diagram which shows other embodiment. 従来の直流・交流回路地絡検出方法を説明するための配電系統の回路図である。It is a circuit diagram of a power distribution system for demonstrating the conventional DC / AC circuit ground fault detection method.

以下、実施の形態を図１〜図７を参照して説明する。 Hereinafter, embodiments will be described with reference to FIGS.

図１は、図８の交直配電系統に適用したもので、図８と同一または相当部分には同一符号を付して説明の重複を避ける。図１の配電系統は、直流回路３０側から図８に示すような直流地絡センサを省略している。図１の配電系統は、非接地系交流回路１０に配設した交流地絡センサ４０ｂが、直流回路３０の直流地絡事故を検出する直流地絡センサ機能を有する。交流地絡センサ４０ｂは、例えば図８と同様な零相変圧器４１や零相変流器４３を備え、図８と同様にして交流回路１０側の交流地絡事故発生を検出する。さらに、交流地絡センサ４０ｂは、直流回路３０側の直流地絡発生時における零相変圧器（ＥＶＴ）４１の励磁電流ｉの変化を検出することで、直流地絡発生を検出する。 FIG. 1 is applied to the AC / DC power distribution system of FIG. 8, and the same or corresponding parts as in FIG. The power distribution system of FIG. 1 omits a DC ground fault sensor as shown in FIG. 8 from the DC circuit 30 side. In the power distribution system of FIG. 1, the AC ground fault sensor 40 b disposed in the non-grounded AC circuit 10 has a DC ground fault sensor function for detecting a DC ground fault in the DC circuit 30. The AC ground fault sensor 40b includes, for example, a zero-phase transformer 41 and a zero-phase current transformer 43 similar to those in FIG. 8, and detects the occurrence of an AC ground fault on the AC circuit 10 side in the same manner as in FIG. Furthermore, the AC ground fault sensor 40b detects the occurrence of a DC ground fault by detecting a change in the excitation current i of the zero-phase transformer (EVT) 41 when a DC ground fault occurs on the DC circuit 30 side.

交流地絡センサ４０ｂを具体的に説明する。交流地絡センサ４０ｂは、ＥＶＴ４１の励磁電流ｉをＥＶＴ４１の一次側相に設置した相変流器ＣＴ１により検出する。相変流器ＣＴ１を、ＥＶＴ４１の一次側三相三線の少なくとも一相に設置する。相変流器ＣＴ１でＥＶＴ４１の一次側励磁電流を測定し、直流回路３０側に直流地絡事故発生の時点で変位するＥＶＴ励磁電流ｉの変化をデータ演算処理部８１で検出して演算処理する。データ演算処理部８１は、ＥＶＴ励磁電流ｉの変化を、図２に示すような特性項目に関する演算を行い、直流地絡発生の有無データを出力する。 The AC ground fault sensor 40b will be specifically described. The AC ground fault sensor 40b detects the excitation current i of the EVT 41 by the phase current transformer CT1 installed in the primary side phase of the EVT 41. The phase current transformer CT1 is installed in at least one phase of the primary side three-phase three-wire of the EVT 41. The primary current excitation of the EVT 41 is measured by the phase current transformer CT1, and the change of the EVT excitation current i that is displaced when the DC ground fault occurs on the DC circuit 30 side is detected and calculated by the data calculation processing unit 81. . The data calculation processing unit 81 performs a calculation related to the characteristic item as shown in FIG.

図２に示す特性項目は、［Ａ］ＥＶＴ励磁電流ｉの実効値の増加項目、［Ｂ］ＥＶＴ励磁電流ｉの波高値の増加項目、［Ｃ］ＥＶＴ励磁電流ｉの偶数調波の発生および増加項目、［Ｄ］ＥＶＴ励磁電流ｉの６ｎ±１次調波の増加項目である。これら各特性項目［Ａ］〜［Ｄ］の内の１項目以上の特性項目別にデータの増加成分を演算して、直流回路３０側の地絡事故検出を行う。 The characteristic items shown in FIG. 2 are [A] an item for increasing the effective value of the EVT excitation current i, [B] an item for increasing the peak value of the EVT excitation current i, [C] generation of even harmonics of the EVT excitation current i, and Increase item, [D] Increase item of 6n ± 1st harmonic of EVT excitation current i. The increase component of the data is calculated for each one or more of these characteristic items [A] to [D] to detect the ground fault on the DC circuit 30 side.

［Ａ］〜［Ｄ］の各特性項目それぞれは、正確に検出し易い電磁気的変位であり、かつ、直流地絡事故発生の検出に有効な項目であることから、少なくとも１項目の電磁気的変位を予め設定された閾値と比較などして演算すれば、確実性よく直流地絡発生を検出することができる。なお、複数種類の特性項目それぞれで電磁気的変位の増加成分を演算するようにして、複数全ての特性項目で閾値以上の増加成分を演算した時点で直流地絡事故発生を検出することも可能である。 Since each of the characteristic items [A] to [D] is an electromagnetic displacement that is easy to detect accurately and is an effective item for detecting the occurrence of a DC ground fault, at least one electromagnetic displacement is required. Can be detected with a certainty, for example, by comparing with a preset threshold value. It is also possible to calculate the increase component of electromagnetic displacement for each of multiple types of characteristic items, and detect the occurrence of a DC ground fault when all the multiple characteristic items have been calculated for the increase component above the threshold. is there.

上記［Ｂ］項目の励磁電流波高値演算において、データ演算処理部８１で相変流器ＣＴ１の交流出力の正側波高値Ｉｐと負側波高値Ｉｑの差の増加成分を演算することも有効である。すなわち、直流回路３０側で直流地絡事故が発生した時点で、ＥＶＴ励磁電流ｉが変化し、相変流器ＣＴ１の交流出力の正側波高値Ｉｐと負側波高値Ｉｑの差が増加する。この正負側波高値の差増加成分を演算することで、直流回路３０側の地絡事故発生を検出することができる。また、正側波高値Ｉｐと負側波高値Ｉｑの差の大きさを演算することで、直流地絡事故を起こした直流回路３０の地絡抵抗値Ｒｄｇの大きさが検知でき、より有効な直流地絡保護対策が実施できる。 In the excitation current peak value calculation of the item [B], it is also effective to calculate an increasing component of the difference between the positive side peak value Ip and the negative side peak value Iq of the AC output of the phase current transformer CT1 in the data calculation processing unit 81. It is. That is, when a DC ground fault occurs on the DC circuit 30 side, the EVT excitation current i changes, and the difference between the positive side peak value Ip and the negative side peak value Iq of the AC output of the phase current transformer CT1 increases. . The occurrence of a ground fault on the DC circuit 30 side can be detected by calculating the difference increasing component of the positive and negative side peak values. Further, by calculating the magnitude of the difference between the positive side peak value Ip and the negative side peak value Iq, the magnitude of the ground fault resistance value Rdg of the DC circuit 30 that has caused the DC ground fault can be detected, which is more effective. DC ground fault protection measures can be implemented.

また、上記［Ｂ］項目のＥＶＴ励磁電流ｉの波高値演算において、相変流器ＣＴ１の交流出力の正側波高値Ｉｐの絶対値と負側波高値Ｉｑの絶対値のいずれが大きいかをデータ演算処理部８１で行い、この大小比較結果で直流回路３０での地絡事故の極性を判定する。すなわち、正側波高値Ｉｐの絶対値が負側波高値Ｉｑの絶対値より大きい場合、直流回路３０で地絡事故を起こした電路は正極電路側であると判定する。また、負側波高値Ｉｑの絶対値が正側波高値Ｉｐの絶対値より大きい場合は、地絡事故を起こした直流回路３０の電路は負極電路側であると判定する。このように地絡事故の極性を判定することで、より有効な直流地絡保護対策が実行できる。 In addition, in the calculation of the peak value of the EVT excitation current i in the item [B], which of the absolute value of the positive side peak value Ip and the negative side peak value Iq of the AC output of the phase current transformer CT1 is greater is determined. This is performed by the data arithmetic processing unit 81, and the polarity of the ground fault in the DC circuit 30 is determined based on the magnitude comparison result. That is, when the absolute value of the positive side peak value Ip is larger than the absolute value of the negative side peak value Iq, it is determined that the electric circuit causing the ground fault in the DC circuit 30 is the positive electrode circuit side. When the absolute value of the negative side peak value Iq is larger than the absolute value of the positive side peak value Ip, it is determined that the circuit of the DC circuit 30 that has caused the ground fault is on the negative circuit side. By determining the polarity of the ground fault in this way, more effective DC ground fault protection measures can be executed.

また、図３に示すように、相変流器ＣＴ１の出力端子に正側半波整流回路８２と負側半波整流回路８３を接続して、相変流器ＣＴ１の交流出力の正側波高値Ｉｐと負側波高値Ｉｑの測定を、正負それぞれの半波整流回路８２、８３の電圧出力の測定で行うことができる。このように、相変流器ＣＴ１の交流出力を半波整流して、交流出力の正側波形のみから正側波高値を算出し、負側波形のみから負側波高値を算出することで、より正確な波高値測定ができ、上記［Ｂ］特性項目での演算処理の精度を上げることができる。 In addition, as shown in FIG. 3, a positive half-wave rectifier circuit 82 and a negative half-wave rectifier circuit 83 are connected to the output terminal of the phase current transformer CT1, and the positive side wave of the AC output of the phase current transformer CT1. The high value Ip and the negative side peak value Iq can be measured by measuring the voltage outputs of the positive and negative half-wave rectifier circuits 82 and 83, respectively. Thus, by half-wave rectifying the AC output of the phase current transformer CT1, calculating the positive side peak value only from the positive side waveform of the AC output, and calculating the negative side peak value only from the negative side waveform, More accurate peak value measurement can be performed, and the accuracy of the arithmetic processing in the [B] characteristic item can be increased.

図４に示す実施の形態は、ＥＶＴ励磁電流ｉの変化を、ＥＶＴ４１の中性点接地線４２に設置した中性点変流器ＣＴ２による３ｎ次調波電流の増加により検出する。ここでの中性点変流器ＣＴ２は、図８の零相変流器４３と同等のものが適用できる。なお、図４に示す零相変流器４３は必ずしも必要でなく、中性点変流器ＣＴ２として兼用することができる。このように兼用することで、地絡保護システムのコストダウンが図れる。 In the embodiment shown in FIG. 4, a change in the EVT excitation current i is detected by an increase in the 3n-order harmonic current by the neutral point current transformer CT <b> 2 installed on the neutral point ground line 42 of the EVT 41. Here, the neutral point current transformer CT2 can be equivalent to the zero-phase current transformer 43 of FIG. Note that the zero-phase current transformer 43 shown in FIG. 4 is not necessarily required, and can also be used as the neutral point current transformer CT2. By combining this way, the cost of the ground fault protection system can be reduced.

直流回路３０側で直流地絡事故が発生したときのＥＶＴ４１の励磁電流ｉの変化は、中性点接地線４２に流れる交流電流成分の３ｎ次調波の増加として現れる。そこで、中性点変流器ＣＴ２（又は、零相変流器４３）で検出した交流電流の３ｎ次調波電流の増加分を閾値に基づいて演算することで、直流回路３０側の地絡事故発生を検出することができる。 The change in the excitation current i of the EVT 41 when a DC ground fault occurs on the DC circuit 30 side appears as an increase in the 3n-order harmonic of the AC current component flowing through the neutral point ground line 42. Therefore, the ground fault on the DC circuit 30 side is calculated by calculating the increment of the 3n-order harmonic current of the AC current detected by the neutral point current transformer CT2 (or the zero-phase current transformer 43) based on the threshold value. Accident occurrence can be detected.

図５に示す実施の形態は、主変圧器１の二次側の非接地系交流回路１０に接続された直流回路３０の地絡事故を、交流回路１０側に交流地絡センサ４０ｂとして配設した交流地絡用零相変圧器（ＥＶＴ）４１の三次巻線の３ｎ次調波電圧の変化により検出する。すなわち、直流回路３０側で直流地絡事故が発生してＥＶＴ４１側に直流地絡電流Ｉｄｇが流れると、ＥＶＴ４１の励磁電流ｉが変化すると共に、ＥＶＴ４１の三次巻線の３ｎ次調波電圧が変化する。この変化をＥＶＴ励磁電流ｉの変化に代わり検出することで、直流回路３０側の地絡事故発生を検出することができる。この場合、ＥＶＴ４１の三次巻線の３ｎ次調波電圧の変化とＥＶＴ励磁電流ｉの変化を共に検出するようにして、直流地絡事故発生を検知してもよい。 In the embodiment shown in FIG. 5, a ground fault of the DC circuit 30 connected to the non-grounded AC circuit 10 on the secondary side of the main transformer 1 is arranged as an AC ground fault sensor 40 b on the AC circuit 10 side. Detected by a change in the 3n-order harmonic voltage of the tertiary winding of the AC ground fault zero-phase transformer (EVT) 41. That is, when a DC ground fault occurs on the DC circuit 30 side and the DC ground fault current Idg flows on the EVT 41 side, the excitation current i of the EVT 41 changes and the 3n harmonic voltage of the tertiary winding of the EVT 41 changes. To do. By detecting this change instead of the change in the EVT excitation current i, it is possible to detect the occurrence of a ground fault on the DC circuit 30 side. In this case, the occurrence of a DC ground fault may be detected by detecting both the change in the 3n-order harmonic voltage of the tertiary winding of the EVT 41 and the change in the EVT excitation current i.

以上の各実施の形態において、ＥＶＴ４１の中性点Ｐに直流阻止用コンデンサを入切可能に設置することが有効である。例えば、図６に示すように、中性点接地線４２に直流阻止用コンデンサＣ１と常閉の切換スイッチＳ１の並列回路を介挿する。この場合、ＥＶＴ４１の中性点接地線４２に介挿した常閉の切換スイッチＳ１に直流阻止用コンデンサＣ１を並列接続する。直流回路３０側に地絡事故が発生して、ＥＶＴ４１の中性点接地線４２に直流地絡電流Ｉｄｇが流れた時点で、常閉の切換スイッチＳ１をオフに切り換え、中性点Ｐを直流阻止用コンデンサＣ１を介して接地した状態にする。このようにすれば、直流地絡事故発生直後に、直流地絡電流Ｉｄｇの流れがコンデンサＣ１で阻止されて、交流地絡センサ４０ｂのＥＶＴ４１側が直流地絡電流Ｉｄｇによる偏磁から保護される。 In each of the above-described embodiments, it is effective to install a DC blocking capacitor at the neutral point P of the EVT 41 so that it can be turned on and off. For example, as shown in FIG. 6, a parallel circuit of a DC blocking capacitor C1 and a normally closed changeover switch S1 is inserted in the neutral point ground line 42. In this case, a DC blocking capacitor C1 is connected in parallel to a normally closed changeover switch S1 inserted in the neutral point ground line 42 of the EVT 41. When a ground fault occurs on the DC circuit 30 side and the DC ground fault current Idg flows through the neutral point ground line 42 of the EVT 41, the normally closed changeover switch S1 is turned off, and the neutral point P is switched to DC. The grounding state is established via the blocking capacitor C1. In this way, immediately after the occurrence of the DC ground fault, the flow of the DC ground fault current Idg is blocked by the capacitor C1, and the EVT 41 side of the AC ground fault sensor 40b is protected from the demagnetization due to the DC ground fault current Idg.

次に、図７に示す本発明システムの実施の形態を説明する。 Next, an embodiment of the system of the present invention shown in FIG. 7 will be described.

図７の本発明システムは、主変圧器１の二次側の非接地系交流回路１０に交流地絡センサ４０ｃとして零相電圧分圧器（ＺＰＤ）５１と、直流地絡センサ７０ｂとして零相変圧器（ＥＶＴ）４１’を配備している。同システムは、直流回路３０の地絡事故を、交流回路１０側に直流地絡センサ７０ｂとして配備されたＥＶＴ４１’における励磁電流ｉの変化により検出する。このシステムにおいては、ＥＶＴ４１’の中性点Ｐに直流地絡電流Ｉｄｇを抑制する直流制限抵抗Ｒ１を挿入すると共に、直流地絡事故時にＥＶＴ４１’の一次側を交流回路１０から切り離す開閉手段Ｓ２をＥＶＴ一次側に挿入する。 The system of the present invention in FIG. 7 includes a zero-phase voltage divider (ZPD) 51 as an AC ground fault sensor 40c and a zero-phase transformer as a DC ground fault sensor 70b in the non-grounded AC circuit 10 on the secondary side of the main transformer 1. A container (EVT) 41 'is provided. The system detects a ground fault in the DC circuit 30 based on a change in the excitation current i in the EVT 41 ′ provided as the DC ground fault sensor 70 b on the AC circuit 10 side. In this system, the DC limiting resistor R1 for suppressing the DC ground fault current Idg is inserted at the neutral point P of the EVT 41 ′, and the opening / closing means S2 for disconnecting the primary side of the EVT 41 ′ from the AC circuit 10 in the event of a DC ground fault. Insert into the EVT primary side.

交流地絡センサ４０ｃとしての零相電圧分圧器５１は、例えば、交流回路１０の三相それぞれに一端を接続したコンデンサＣ１〜Ｃ３と、各コンデンサＣ１〜Ｃ３の他端に接続した共通の零相電圧検出用コンデンサＣ４と、コンデンサＣ４に並列に接続した絶縁変圧器６２を備える。零相電圧検出用コンデンサＣ４が接地される。交流回路１０に交流地絡事故が発生していないとき、絶縁変圧器６２の出力電圧はゼロである。交流回路１０の三相三線のいずれか一端子に交流地絡事故が発生すると、コンデンサＣ１〜Ｃ３のいずれかから零相電流検出用コンデンサＣ４に電圧が供給され、絶縁変圧器６２の二次側電圧が上昇して交流地絡事故発生が検出される。 The zero-phase voltage divider 51 serving as the AC ground fault sensor 40c includes, for example, capacitors C1 to C3 having one end connected to each of the three phases of the AC circuit 10, and a common zero phase connected to the other ends of the capacitors C1 to C3. A voltage detection capacitor C4 and an insulation transformer 62 connected in parallel to the capacitor C4 are provided. The zero-phase voltage detection capacitor C4 is grounded. When no AC ground fault has occurred in the AC circuit 10, the output voltage of the isolation transformer 62 is zero. When an AC ground fault occurs at any one of the three-phase three-wire terminals of the AC circuit 10, a voltage is supplied from any of the capacitors C1 to C3 to the zero-phase current detection capacitor C4, and the secondary side of the insulation transformer 62 The voltage rises and the occurrence of an AC ground fault is detected.

図７システムの場合、交流回路１０側に配設した直流地絡センサ７０ｂとしてのＥＶＴ４１’の中性点接地線４２に介挿した直流制限抵抗Ｒ１が、直流地絡事故発生時に流れる過大なＥＶＴ励磁電流ｉからＥＶＴ４１’を保護する。または、直流地絡事故発生時に、開閉手段Ｓ２でＥＶＴ４１’を交流回路１０側から切り離すようにすることで、ＥＶＴ４１’を同様に保護することができる。 In the case of the system shown in FIG. 7, the DC limiting resistor R1 inserted in the neutral grounding wire 42 of the EVT 41 ′ as the DC ground fault sensor 70b disposed on the AC circuit 10 side causes an excessive EVT that flows when a DC ground fault occurs. The EVT 41 ′ is protected from the excitation current i. Alternatively, when the DC ground fault occurs, the EVT 41 'can be similarly protected by disconnecting the EVT 41' from the AC circuit 10 side by the switching means S2.

１主変圧器
１０交流回路
２０三相整流器
３０直流回路
３３直流負荷
４０ｂ、４０ｃ交流地絡センサ
４１交流地絡検出用零相変圧器（ＥＶＴ）
４１’ 直流地絡検出用零相変圧器（ＥＶＴ）
４２中性点接地線
４３零相変流器
７０ｂ直流地絡センサ
ＣＴ１相変流器
ＣＴ２中性点変流器
Ｃ１直流阻止用コンデンサ
Ｓ１切換スイッチ
Ｒ１直流制限抵抗
Ｓ２開閉手段
Iｄｇ直流地絡電流
Ｒｄｇ地絡抵抗 DESCRIPTION OF SYMBOLS 1 Main transformer 10 AC circuit 20 Three-phase rectifier 30 DC circuit 33 DC load 40b, 40c AC ground fault sensor 41 Zero phase transformer (EVT) for AC ground fault detection
41 'Zero-phase transformer (EVT) for DC ground fault detection
42 Neutral grounding wire 43 Zero-phase current transformer 70b DC ground fault sensor CT1 Phase current transformer CT2 Neutral current transformer C1 DC blocking capacitor S1 Changeover switch R1 DC limiting resistor S2 Opening / closing means
Idg DC ground fault current Rdg Ground fault resistance

Claims

主変圧器二次側の非接地系交流回路に接続された直流回路の地絡事故を、前記交流回路側に交流地絡センサとして配設した交流地絡用零相変圧器の励磁電流の変化により検出することを特徴とする直流・交流回路地絡検出方法。 Changes in the excitation current of a zero-phase transformer for AC ground fault that is arranged as an AC ground fault sensor on the AC circuit side due to a ground fault in the DC circuit connected to the ungrounded AC circuit on the secondary side of the main transformer DC / AC circuit ground fault detection method characterized by detecting by the above.

前記励磁電流を前記零相変圧器の一次側相に設置した相変流器により検出し、検出した励磁電流の特性項目である実効値の増加、波高値の増加、偶数調波の発生および増加、６ｎ±１次調波の増加の各特性項目の１項目以上で前記直流回路の地絡事故検出を行うことを特徴とする請求項１に記載の直流・交流回路地絡検出方法。 The exciting current is detected by a phase current transformer installed in the primary side phase of the zero-phase transformer, and an increase in effective value, an increase in peak value, generation and increase of even harmonics are characteristic items of the detected exciting current. 2. The DC / AC circuit ground fault detection method according to claim 1, wherein the fault detection of the DC circuit is performed on one or more of each characteristic item of an increase in 6n ± 1st harmonic.

前記相変流器の交流出力の正側波高値と負側波高値の差の増加により前記直流回路の地絡事故検出を行うことを特徴とする請求項２に記載の直流・交流回路地絡検出方法。 3. The DC / AC circuit ground fault according to claim 2, wherein the fault detection of the DC circuit is performed by increasing a difference between a positive side peak value and a negative side peak value of the AC output of the phase current transformer. Detection method.

前記差の大きさから、前記直流回路での地絡抵抗値の大きさを検知することを特徴とする請求項３に記載の直流・交流回路地絡検出方法。 4. The DC / AC circuit ground fault detection method according to claim 3, wherein the magnitude of the ground fault resistance value in the DC circuit is detected from the magnitude of the difference.

前記正側波高値と負側波高値の大小比較で、前記直流回路での地絡事故の極性を検知することを特徴とする請求項３または４に記載の直流・交流回路地絡検出方法。 5. The DC / AC circuit ground fault detection method according to claim 3, wherein the polarity of the ground fault in the DC circuit is detected by comparing the magnitudes of the positive side peak value and the negative side peak value. 6.

前記波高値の測定を、前記相変流器の出力端子に接続した正負それぞれの半波整流回路の電圧出力の測定で行うことを特徴とする請求項３〜５のいずれか一記載の直流・交流回路地絡検出方法。 6. The direct current and the direct current of claim 3, wherein the peak value is measured by measuring voltage outputs of positive and negative half-wave rectifier circuits connected to an output terminal of the phase current transformer. AC circuit ground fault detection method.

前記励磁電流の変化を、前記零相変圧器の中性点接地線に設置した中性点変流器による３ｎ次調波電流の増加により検出することを特徴とする請求項１に記載の直流・交流回路地絡検出方法。 2. The direct current according to claim 1, wherein the change in the excitation current is detected by an increase in a 3n-order harmonic current by a neutral point current transformer installed on a neutral point ground line of the zero-phase transformer.・ AC circuit ground fault detection method.

主変圧器二次側の非接地系交流回路に接続された直流回路の地絡事故を、前記交流回路側に交流地絡センサとして配設した交流地絡用零相変圧器の三次巻線の３ｎ次調波電圧の変化により検出することを特徴とする直流・交流回路地絡検出方法。 A ground fault of a DC circuit connected to a non-grounded AC circuit on the secondary side of the main transformer is detected by a third winding of a zero-phase transformer for AC ground fault arranged as an AC ground fault sensor on the AC circuit side. A method for detecting a ground fault of a DC / AC circuit, characterized by detecting a change in a 3n-order harmonic voltage.

前記零相変圧器の中性点に直流阻止用コンデンサを入切可能に設置し、前記直流回路の地絡事故検出時に前記コンデンサを入状態にして前記中性点を前記コンデンサを介して接地することを特徴とする請求項１〜８のいずれか一記載の直流・交流回路地絡検出方法。 A DC blocking capacitor is installed at the neutral point of the zero-phase transformer so that it can be turned on and off, and when the ground fault of the DC circuit is detected, the capacitor is turned on and the neutral point is grounded through the capacitor. The DC / AC circuit ground fault detection method according to any one of claims 1 to 8.

主変圧器二次側の非接地系交流回路に接続された直流回路の地絡事故を、前記交流回路側に交流地絡センサとして配設した零相電圧分圧器および前記交流回路側に直流地絡センサとして配設した零相変圧器における前記零相変圧器の励磁電流の変化により検出する直流・交流回路地絡検出システムであって、
前記直流回路の地絡事故による直流地絡電流を抑制する直流制限抵抗を前記零相変圧器の中性点に挿入し、または、前記零相変圧器の一次側に、当該一次側を直流地絡事故時に前記交流回路から切り離す開閉手段を挿入したことを特徴とする直流・交流回路地絡検出システム。 A ground fault in a DC circuit connected to a non-grounded AC circuit on the secondary side of the main transformer is a zero-phase voltage divider arranged as an AC ground fault sensor on the AC circuit side and a DC ground on the AC circuit side. A DC / AC circuit ground fault detection system for detecting a change in excitation current of the zero-phase transformer in a zero-phase transformer arranged as a fault sensor,
A DC limiting resistor that suppresses a DC ground fault current due to a ground fault in the DC circuit is inserted at the neutral point of the zero phase transformer, or the primary side is connected to the DC ground. A DC / AC circuit ground fault detection system comprising an opening / closing means for disconnecting from the AC circuit in the event of a fault.