JP5272678B2 - Overexcitation detection device - Google Patents

Overexcitation detection device Download PDF

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JP5272678B2
JP5272678B2 JP2008296608A JP2008296608A JP5272678B2 JP 5272678 B2 JP5272678 B2 JP 5272678B2 JP 2008296608 A JP2008296608 A JP 2008296608A JP 2008296608 A JP2008296608 A JP 2008296608A JP 5272678 B2 JP5272678 B2 JP 5272678B2
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overexcitation
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JP2010124623A (en
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幹夫 新谷
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Mitsubishi Electric Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an overexcitation detecting arrangement capable of detecting an overexcitation state of a coil without requiring a plurality of current detectors and an excitation current calculating circuit, to settle the problem of need for two current detectors and calculation precision since an excitation current is calculated from a primary current and a secondary current and a tertiary harmonics component is calculated from the excitation current for judgement based on the magnitude in order to determine the overexcitation state of a transformer. <P>SOLUTION: A current measurement device 4 is provided to a ground circuit of a neutral point of a Y winding 3 of a transformer 2. A tertiary harmonics is detected from the output using a tertiary harmonics filter 6, and the presence of the overexcitation state is detected based on the presence of the tertiary harmonics. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

この発明は、電力系統に接続され、変圧器の過励磁状態を検出する過励磁検出装置に関するものである。   The present invention relates to an overexcitation detection device that is connected to a power system and detects an overexcitation state of a transformer.

変圧器に、定格電圧を超える電圧を与えた場合には、鉄芯内で発生する鉄損が増大して、機器の異常加熱を引き起こすとともに効率の低下を発生させる過励磁状態に陥る。このため過励磁状態をいちはやく検出し対処するために過励磁検出装置が求められている。
従来の過励磁検出装置においては、変圧装置の一次電流と二次電流を測定するために電流測定器をそれぞれ設置し、その電流に基づいて励磁電流を算出し、その励磁電流に含まれる第三次高調波成分を検出することで変圧器の過励磁状態を判定している。（特許文献１） When a voltage exceeding the rated voltage is applied to the transformer, the iron loss generated in the iron core increases, resulting in an overexcitation state that causes abnormal heating of the device and a decrease in efficiency. For this reason, there is a need for an overexcitation detection device to quickly detect and deal with overexcitation conditions.
In the conventional overexcitation detection device, a current measuring device is installed to measure the primary current and secondary current of the transformer device, the excitation current is calculated based on the current, and the third current included in the excitation current is calculated. The over-excitation state of the transformer is determined by detecting the second harmonic component. (Patent Document 1)

特開２００４−４０９５５号公報（段落［００７２］から［００８１］、図９）JP 2004-40955 (paragraphs [0072] to [0081], FIG. 9)

従来の変圧器の過励磁検出装置によれば、第三次高調波成分を検出する場合、一次電流と二次電流の双方の電流を検出する電流検出器を設置する必要があった。さらに、双方の電流検出器の検出値から励磁電流を算出するための励磁電流計算回路を設置する必要もあった。   According to the conventional transformer overexcitation detection device, when detecting the third harmonic component, it is necessary to install a current detector for detecting both the primary current and the secondary current. In addition, it is necessary to install an excitation current calculation circuit for calculating the excitation current from the detection values of both current detectors.

この発明は、上記のような複数の電流検出器や励磁電流算出回路を必要とすることなく、コイルの過励磁状態を検出できる過励磁検出装置を得るものである。   The present invention provides an overexcitation detection device that can detect the overexcitation state of a coil without requiring a plurality of current detectors and excitation current calculation circuits as described above.

この発明では、電力系統に接続された変圧器のＹ巻線が過励磁状態にあるとき、Ｙ巻線の中性点の接地回路に第三次高調波を含んだ電流が流れることに着眼したものである。このためＹ巻線の中性点の接地回路に電流検出器を設け、この電流検出器により検出された電流値の第三次高調波成分を抽出するための第三次高調波濾波器を設け、第三次高調波成分による出力が所定値を超えた場合、過励磁状態の判定を実施する。   In the present invention, when the Y winding of the transformer connected to the power system is in an overexcited state, it is noted that a current including the third harmonic flows in the ground circuit at the neutral point of the Y winding. Is. For this purpose, a current detector is provided in the grounding circuit at the neutral point of the Y winding, and a third harmonic filter is provided for extracting the third harmonic component of the current value detected by the current detector. When the output by the third harmonic component exceeds a predetermined value, the overexcitation state is determined.

この発明の過励磁検出装置は、変圧器のＹ巻線の中性点の接地回路に流れる電流を測定するので、中性点に電流検出器があればよい。従来技術では、２台の電流検出器を必要とし２台の電流検出器の出力の誤差が発生し判定結果に影響を及ぼすこととなる。この発明では、中性点の電流検出器の精度だけを考慮すればよいので、電流をより正確に検出することが出来、過励磁状態を精度良く検出することができる。   Since the overexcitation detection device of the present invention measures the current flowing in the grounding circuit at the neutral point of the Y winding of the transformer, it suffices if there is a current detector at the neutral point. In the prior art, two current detectors are required, and an error in the output of the two current detectors occurs, affecting the determination result. In the present invention, since only the accuracy of the neutral-point current detector needs to be considered, the current can be detected more accurately, and the overexcitation state can be detected with high accuracy.

実施の形態１．
図１は、この発明を実施するための実施の形態１における過励磁検出装置の回路構成図である。過励磁検出装置５は、電流測定器４、第三次高調波濾波器６、レベル判定器７から構成されている。電力系統１に接続された変圧器２における一次側Ｙ巻線３の中性点の接地回路に、電流測定器４が設置されている。過励磁検出装置５において、電流測定器４の出力は、第三次高調波成分を抽出する第三次高調波濾波器６の入力に接続され、第三次高調波濾波器６の出力がレベル判定器７の入力部に接続されている。 Embodiment 1 FIG.
FIG. 1 is a circuit configuration diagram of an overexcitation detection device according to Embodiment 1 for carrying out the present invention. The overexcitation detection device 5 includes a current measuring device 4, a third harmonic filter 6, and a level determination device 7. A current measuring device 4 is installed in the ground circuit at the neutral point of the primary Y winding 3 in the transformer 2 connected to the power system 1. In the overexcitation detection device 5, the output of the current measuring device 4 is connected to the input of the third harmonic filter 6 that extracts the third harmonic component, and the output of the third harmonic filter 6 is level. It is connected to the input unit of the determiner 7.

図２は実施の形態１における過励磁検出装置の動作を説明する波形図である。図２（ａ）は変圧器２のＹ巻線３に印加される電圧を示しており、図２（ｂ）は、電流測定器４で計測したＹ巻線３の中性点の接地回路に流れる電流を示している。
通常の電力用変圧器の定格電圧での磁束密度は鉄心の飽和磁束密度の８５％前後に設定される場合が多いため、変圧器２に定格電圧Ｖを例えば１０％超える電圧が印加されると、図２（ａ）に示すように過励磁分の電圧によって変圧器２のＹ巻線３の鉄心の磁束飽和現象が発生し、変圧器２のＹ巻線３の中性点の接地回路に鉄心の磁束飽和により低下した励磁インピーダンスに応じた電流ＩＮ（図２（ｂ））が流れる。
過励磁状態にある変圧器２のＹ巻線３は電圧１相につき１周期で正方向と負方向で１８０度間隔で２回の鉄心飽和が発生する。よって、位相が１２０度と２４０度ずれた位相を合わせて、電圧３相では、正方向と負方向で６０度間隔６回の鉄心飽和が発生し、変圧器２のＹ巻線３の中性点の接地回路には第三次高調波を含んだ電流ＩＮが発生する。従って、電流測定器４の出力から第三次高調波濾波器６によって第三次高調波成分を抽出し、第三次高調波成分の有無をレベル判定器７で判定する。
このレベル判定器７で用いる判定値は、変圧器の励磁特性に応じて任意に設定する固有のものであるが、少なくとも変圧器２に定格電圧Ｖが印加されるときＹ巻線３の中性点の接地回路に流れる電流の第三次高調波成分より大きな値に設定される。このとき、第三次高調波濾波器６の出力は実効値又は波高値を抽出してあらかじめ定めた所定値と比較することとしてもよい。 FIG. 2 is a waveform diagram for explaining the operation of the overexcitation detection apparatus in the first embodiment. 2A shows the voltage applied to the Y winding 3 of the transformer 2, and FIG. 2B shows the neutral circuit of the Y winding 3 measured by the current measuring device 4. The flowing current is shown.
Since the magnetic flux density at the rated voltage of a normal power transformer is often set to about 85% of the saturation magnetic flux density of the iron core, when a voltage exceeding the rated voltage V, for example, 10% is applied to the transformer 2. As shown in FIG. 2A, the magnetic flux saturation phenomenon of the iron core of the Y winding 3 of the transformer 2 occurs due to the overexcitation voltage, and the neutral circuit of the Y winding 3 of the transformer 2 becomes A current I N (FIG. 2 (b)) corresponding to the excitation impedance reduced by the magnetic flux saturation of the iron core flows.
The Y winding 3 of the transformer 2 in an overexcited state undergoes iron core saturation twice at 180 ° intervals in the positive and negative directions in one cycle per voltage phase. Therefore, when the phases are shifted by 120 degrees and 240 degrees, in the three voltage phases, the iron core saturation occurs six times at 60 degree intervals in the positive and negative directions, and the neutrality of the Y winding 3 of the transformer 2 the ground circuit of point current I N is generated that contains the third harmonic. Therefore, the third harmonic component is extracted from the output of the current measuring device 4 by the third harmonic filter 6, and the presence or absence of the third harmonic component is determined by the level determiner 7.
The determination value used in the level determination unit 7 is a unique value that is arbitrarily set according to the excitation characteristics of the transformer, but at least when the rated voltage V is applied to the transformer 2, the neutrality of the Y winding 3. It is set to a value larger than the third harmonic component of the current flowing through the point ground circuit. At this time, the output of the third harmonic filter 6 may extract an effective value or a peak value and compare it with a predetermined value.

このように、過励磁検出装置５に於いては、変圧器２の過励磁状態をＹ巻線３の中性点の接地回路に流れる電流から検出できるようにしたので、単一の電流検出器を用いて変圧器の過励磁状態を精度よく検出できる。また、電流検出器を２台用いる方法に比べて経済的である。加えて、従来必要であった、一次電流検出値、二次電流検出値から励磁電流を算出する励磁電流計算回路も不要であるので、この回路の計算誤差も考慮しなくてもよいので、より正確な過励磁検出が出来、経済的にも有利である。 Thus, in the overexcitation detection device 5, the overexcitation state of the transformer 2 can be detected from the current flowing in the grounding circuit at the neutral point of the Y winding 3, so that a single current detector is provided. Can be used to accurately detect the overexcitation state of the transformer. Moreover, it is more economical than the method using two current detectors. In addition, since the excitation current calculation circuit for calculating the excitation current from the primary current detection value and the secondary current detection value, which was necessary in the past, is unnecessary, it is not necessary to consider the calculation error of this circuit. Accurate overexcitation detection is possible, which is economically advantageous.

実施の形態２．
図３は、この発明を実施するための実施の形態２における過励磁検出装置の回路構成図である。過励磁検出装置１０は、電流測定器４、第三次高調波濾波器６、基本波濾波器８、比較器９から構成されている。
実施の形態１では、電流測定器４を、第三次高調波濾波器６に接続し、この出力レベルをレベル判定器７であらかじめ定めた所定値と比較して過励磁状態を判定するよう構成した。これに対して、実施の形態２では図３に示すように、電流測定器４を第三次高調波濾波器６と、基本波濾波器８に接続し、第三次高調波濾波器６と基本波濾波器８を比較器９に接続している。 Embodiment 2. FIG.
FIG. 3 is a circuit configuration diagram of an overexcitation detection device according to Embodiment 2 for carrying out the present invention. The overexcitation detection device 10 includes a current measuring device 4, a third harmonic filter 6, a fundamental wave filter 8, and a comparator 9.
In the first embodiment, the current measuring device 4 is connected to the third harmonic filter 6, and the output level is compared with a predetermined value determined in advance by the level determining device 7 to determine the overexcitation state. did. On the other hand, in the second embodiment, as shown in FIG. 3, the current measuring device 4 is connected to the third harmonic filter 6 and the fundamental wave filter 8, and the third harmonic filter 6 and A fundamental wave filter 8 is connected to a comparator 9.

図４は、この発明の実施の形態２の比較器における判定特性の第１の例について示した図である。図４は、第三次高調波成分と基本波成分の大きさから、過励磁状態を判定するための特性を示しており、この境界を示す基準値より上の斜線で示す領域が過励磁状態と判定する領域である。
変圧器２のＹ巻線３の接地回路に流れる電流を、電流検出器４で検出し、この出力を第三次高調波濾波器６と基本波濾波器８で濾波し、基本波濾波器８の出力値の関数として定められた基準値と第三次高調波濾波器６の出力値を比較し、第三次高調波成分の出力値の方が、図４の境界を示す基準値より大きければ、過励磁状態と判定する。 FIG. 4 is a diagram showing a first example of determination characteristics in the comparator according to the second embodiment of the present invention. FIG. 4 shows the characteristics for determining the overexcitation state from the magnitudes of the third harmonic component and the fundamental wave component. The region indicated by the oblique line above the reference value indicating this boundary is the overexcitation state. It is an area to be determined.
The current flowing through the ground circuit of the Y winding 3 of the transformer 2 is detected by the current detector 4, and the output is filtered by the third harmonic filter 6 and the fundamental wave filter 8. 4 is compared with the output value of the third harmonic filter 6 and the output value of the third harmonic component is larger than the reference value indicating the boundary of FIG. In this case, the overexcitation state is determined.

図２、図３、図４により、実施の形態２における、過励磁検出器の動作について説明する。
図３で、電力系統１から変圧器２のＹ巻線３に変圧器２の定格電圧Ｖ以下の電圧が印加されている状態では、電流測定器４の出力はほぼゼロである。実際にはインピーダンス不整合により流れる基本波成分の電流が存在するが微小である。
変圧器２に定格電圧Ｖを超える電圧が印加されると、図２（ａ）に示すように変圧器２のＹ巻線３の鉄心の磁束飽和現象が発生し、変圧器２のＹ巻線３の中性点の接地回路に鉄心の磁束飽和により低下した励磁インピーダンスに応じた電流ＩＮ（図２（ｂ））が流れる。
過励磁状態にある変圧器２のＹ巻線３は電圧１相につき１周期で正方向と負方向で１８０度間隔で２回の鉄心飽和が発生する。よって、位相が１２０度と２４０度ずれた位相を合わせて、電圧３相では、正方向と負方向で６０度間隔６回の鉄心飽和が発生し、変圧器２のＹ巻線３の中性点の接地回路には第三次高調波を含んだ電流ＩＮが発生する。
変圧器２のＹ巻線３の接地回路に流れる電流を、電流検出器４で検出し、この出力を第三次高調波濾波器６と基本波濾波器８で濾波し、基本波濾波器８の出力値の関数として定められた基準値と第三次高調波濾波器６の出力値を比較し、第三次高調波成分の出力値の方が、図４の境界を示す基準値より大きければ、過励磁状態と判定する。 The operation of the overexcitation detector in the second embodiment will be described with reference to FIGS.
In FIG. 3, the output of the current measuring device 4 is almost zero when a voltage equal to or lower than the rated voltage V of the transformer 2 is applied from the power system 1 to the Y winding 3 of the transformer 2. Actually, a current of a fundamental wave component flowing due to impedance mismatch exists but is very small.
When a voltage exceeding the rated voltage V is applied to the transformer 2, a magnetic flux saturation phenomenon occurs in the iron core of the Y winding 3 of the transformer 2 as shown in FIG. A current I N (FIG. 2B) corresponding to the excitation impedance reduced due to the magnetic flux saturation of the iron core flows through the grounding circuit at the neutral point of 3.
The Y winding 3 of the transformer 2 in an overexcited state undergoes iron core saturation twice at 180 ° intervals in the positive and negative directions in one cycle per voltage phase. Therefore, when the phases are shifted by 120 degrees and 240 degrees, in the three voltage phases, the iron core saturation occurs six times at 60 degree intervals in the positive and negative directions, and the neutrality of the Y winding 3 of the transformer 2 the ground circuit of point current I N is generated that contains the third harmonic.
The current flowing through the ground circuit of the Y winding 3 of the transformer 2 is detected by the current detector 4, and the output is filtered by the third harmonic filter 6 and the fundamental wave filter 8. 4 is compared with the output value of the third harmonic filter 6 and the output value of the third harmonic component is larger than the reference value indicating the boundary of FIG. In this case, the overexcitation state is determined.

実施の形態１では変圧器２が過励磁状態と判定するために、レベル判定器７に変圧器２毎に定めた固有の所定値を設定しなければならなかった。
これに対して、実施の形態２では、変圧器２のＹ巻線３の接地回路に流れる電流を、電流検出器４で検出し、この出力を第三次高調波濾波器６と基本波濾波器８で濾波し、基本波濾波器８の出力値の関数として定められた基準値と第三次高調波濾波器６の出力値を比較し、第三次高調波成分の出力値の方が、図４の境界を示す基準値より大きければ、過励磁状態と判定する構成とした。第三次高調波成分による出力が図４の境界値より大きければ、過励磁状態と判定することとした。これにより中性点の接地回路に流れる電流が、トランス巻線や電流系統の微小なアンバランス、地絡事故等によって基本成分、第三次高調波成分ともに増大するような場合であっても、精度のよい過励磁状態の判定ができ、変圧器２毎に固有の閾値を設定する必要がない。第三次高調波成分の大きさと基本波成分の大きさを前もって設定した図４の判定特性を基に比較することにより変圧器の過励磁を検出できるものである。第三次高調波成分の大きさと基本波成分の大きさは、各濾波器の出力の実効値又は波高値を抽出して比較することとしてもよい。
図５は、この発明の実施の形態２の比較器における判定特性の第１の例を説明する図である。図５で、図４に示した境界値の特性について説明する。インピーダンス不整合を起因としたアンバランス現象による中性点に流れる電流の基本波及び第三次高調波成分は絶対値が比較的小さいので、これは図の左方下部の「アンバランス領域」と記載した領域にあたる。よってこの領域を避けて過励磁状態を検出する為、第三次高調波成分の大きさが所定の値Ａ１以上の時のみ、過励磁状態を検出すべくＡ１の値を設定すればよい。
また、地絡事故による中性点の電流量は大きくなるが、第三次高調波成分の大きさは基本波成分の大きさの３０％を超えず、図５の「比率３０％」と記載した直線の下側の、図５の右下部の「地絡事故領域」と記載した領域にあたる。この領域を避けて過励磁状態を検出しかつ誤検出防止の為、例えば第三次高調波成分の大きさが基本波成分の大きさの３５％となる直線を、図５に「過励磁検出比率」と記載して示したように決めてやればよい。
過励磁による中性点を流れる電流の第三次高調波成分は、図４の左方上部領域の「過励磁領域」と記載した領域を占めるので、この領域を検出することで、過励磁状態を精度よく確認することが出来る。 In Embodiment 1, in order to determine that the transformer 2 is in an overexcited state, a specific predetermined value determined for each transformer 2 must be set in the level determiner 7.
On the other hand, in the second embodiment, the current flowing through the ground circuit of the Y winding 3 of the transformer 2 is detected by the current detector 4, and this output is detected by the third harmonic filter 6 and the fundamental wave filter. The filter 8 is filtered, the reference value determined as a function of the output value of the fundamental wave filter 8 is compared with the output value of the third harmonic filter 6, and the output value of the third harmonic component is better. If it is larger than the reference value indicating the boundary in FIG. 4, the overexcitation state is determined. If the output by the third harmonic component is larger than the boundary value in FIG. As a result, even if the current flowing in the grounding circuit at the neutral point increases both the basic component and the third harmonic component due to a slight imbalance in the transformer winding and current system, a ground fault, etc. The overexcitation state can be determined with high accuracy, and there is no need to set a unique threshold value for each transformer 2. By comparing the magnitude of the third harmonic component and the magnitude of the fundamental component based on the determination characteristics shown in FIG. 4 set in advance, overexcitation of the transformer can be detected. The magnitude of the third harmonic component and the magnitude of the fundamental component may be compared by extracting the effective value or peak value of the output of each filter.
FIG. 5 is a diagram illustrating a first example of determination characteristics in the comparator according to the second embodiment of the present invention. The characteristics of the boundary values shown in FIG. 4 will be described with reference to FIG. Since the absolute value of the fundamental and third harmonic components of the current flowing in the neutral point due to the unbalance phenomenon due to impedance mismatch is relatively small, this is the `` unbalance region '' at the lower left of the figure. It corresponds to the described area. Therefore, in order to detect the overexcitation state while avoiding this region, the value of A1 may be set to detect the overexcitation state only when the magnitude of the third harmonic component is equal to or greater than the predetermined value A1.
Moreover, although the amount of current at the neutral point due to the ground fault increases, the magnitude of the third harmonic component does not exceed 30% of the magnitude of the fundamental component, and is described as “ratio 30%” in FIG. This corresponds to the area described as “ground fault area” in the lower right part of FIG. 5 below the straight line. In order to detect the overexcitation state while avoiding this region and prevent erroneous detection, for example, a straight line in which the third harmonic component is 35% of the fundamental component is shown in FIG. What is necessary is just to determine as described in the ratio.
The third harmonic component of the current flowing through the neutral point due to over-excitation occupies the region described as “over-excitation region” in the upper left region of FIG. 4. By detecting this region, the over-excitation state Can be confirmed with high accuracy.

このように、過励磁検出装置１０においては、変圧器２毎に固有の所定値の設定が不要で、変圧器２の過励磁状態を精度よく検出できるという効果がある。
図６は、この発明の実施の形態２の比較器における判定特性の第２の例について示した図である。基本波成分と第三次高調波成分の関係から、過励磁状態を検出する特性を、図４に例示したが、図６に示すように、２つの成分の関係を所定の傾きと切片を持った一次関数として表し、第三次高調波成分の大きさがこれを超えたとき、過励磁状態と判定してもよい。 Thus, in the overexcitation detection device 10, there is no need to set a specific predetermined value for each transformer 2, and the overexcitation state of the transformer 2 can be accurately detected.
FIG. 6 is a diagram showing a second example of determination characteristics in the comparator according to the second embodiment of the present invention. FIG. 4 illustrates the characteristic of detecting the overexcitation state from the relationship between the fundamental wave component and the third harmonic component. As shown in FIG. 6, the relationship between the two components has a predetermined slope and intercept. When the magnitude of the third harmonic component exceeds this, it may be determined as an overexcitation state.

上記説明は、この発明の用途として発電所に設置される変圧器の場合を説明した。他に、変電所の変圧器など、Ｙ巻線の中性点が接地された変圧器であれば、過励磁検出が必要となる保護継電器などの分野にも応用できる。 The above description has explained the case of a transformer installed in a power plant as an application of the present invention. In addition, any transformer such as a transformer in a substation, where the neutral point of the Y winding is grounded, can be applied to a field such as a protective relay that requires overexcitation detection.

この発明の実施の形態１を示す過励磁検出装置の回路構成図である。It is a circuit block diagram of the overexcitation detection apparatus which shows Embodiment 1 of this invention. この発明の実施の形態１、２による過励磁検出装置の動作を説明する波形図である。It is a wave form diagram explaining operation | movement of the overexcitation detection apparatus by Embodiment 1, 2 of this invention. この発明の実施の形態２を示す過励磁検出装置の回路構成図である。It is a circuit block diagram of the overexcitation detection apparatus which shows Embodiment 2 of this invention. この発明の実施の形態２の比較器における判定特性の第１の例について示した図である。It is the figure shown about the 1st example of the determination characteristic in the comparator of Embodiment 2 of this invention. この発明の実施の形態２の比較器における判定特性の第１の例を説明する図である。It is a figure explaining the 1st example of the determination characteristic in the comparator of Embodiment 2 of this invention. この発明の実施の形態２の比較器における判定特性の第２の例について示した図である。It is the figure shown about the 2nd example of the determination characteristic in the comparator of Embodiment 2 of this invention.

符号の説明Explanation of symbols

１ 電力系統
２ 変圧器
３ Ｙ巻線
４ 電流測定器
５、１０ 過励磁検出装置
６ 第３次高調波濾波器
７ レベル判定器
８ 基本波濾波器
９ 比較器

DESCRIPTION OF SYMBOLS 1 Electric power system 2 Transformer 3 Y winding 4 Current measuring device 5, 10 Overexcitation detection device 6 3rd harmonic filter 7 Level judgment device 8 Fundamental wave filter 9 Comparator

Claims (2)

電力系統に接続された変圧器の一次側又は二次側のいずれか一方のＹ巻線における中性点の接地回路に設けられた電流測定器と、前記電流測定器の出力から第三次高調波成分を抽出する第三次高調波濾波器と、前記第三次高調波濾波器の出力から第三次高調波成分の有無を判定するレベル判定器を備えた過励磁検出装置。 A current measuring device provided in a grounding circuit at a neutral point in the Y winding on either the primary side or the secondary side of the transformer connected to the electric power system, and a third harmonic from the output of the current measuring device; An overexcitation detection device comprising: a third harmonic filter for extracting a wave component; and a level determination unit for determining the presence or absence of the third harmonic component from the output of the third harmonic filter. 電力系統に接続された変圧器の一次側又は二次側のいずれか一方のＹ巻線における中性点の接地回路に設けられた電流測定器と、前記電流測定器の出力から第三次高調波成分を抽出する第三次高調波濾波器と、前記電流測定器の出力から基本波成分を抽出する基本波濾波器と、前記基本波濾波器の出力の関数として定められた基準値と前記第三次高調波濾波器の出力とを比較し前記第三次高調波濾波器の出力の方が大きいか否か判別する比較器を備えた過励磁検出装置。 A current measuring device provided in a grounding circuit at a neutral point in the Y winding on either the primary side or the secondary side of the transformer connected to the electric power system, and a third harmonic from the output of the current measuring device; A third harmonic filter for extracting a wave component, a fundamental wave filter for extracting a fundamental wave component from the output of the current measuring instrument, a reference value defined as a function of the output of the fundamental wave filter, and the An overexcitation detection device comprising a comparator for comparing the output of a third harmonic filter and determining whether the output of the third harmonic filter is greater.
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