JPH0833193A - Transformer protection relay system for power receiving and transforming equipment and transformer protecting method for power receiving and transforming equipment - Google Patents
Transformer protection relay system for power receiving and transforming equipment and transformer protecting method for power receiving and transforming equipmentInfo
- Publication number
- JPH0833193A JPH0833193A JP16668294A JP16668294A JPH0833193A JP H0833193 A JPH0833193 A JP H0833193A JP 16668294 A JP16668294 A JP 16668294A JP 16668294 A JP16668294 A JP 16668294A JP H0833193 A JPH0833193 A JP H0833193A
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- JP
- Japan
- Prior art keywords
- current
- transformer
- saturation
- power receiving
- difference
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Protection Of Transformers (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は受変電設備の変圧器用保
護継電システム及び受変電設備の変圧器保護方法の改良
に係り、特に変圧器の１次側と２次側に流れる差電流を
捕らえて変圧器の内部異常を検出するように形成されて
いる受変電設備の変圧器用保護継電システムに関するも
のである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a protective relay system for a transformer of a power receiving and transforming equipment and a method of protecting a transformer of the power receiving and transforming equipment, and more particularly, to a differential current flowing between a primary side and a secondary side of the transformer. The present invention relates to a protective relay system for a transformer of a power receiving and transforming facility, which is configured to catch and detect an internal abnormality of the transformer.
【０００２】[0002]
【従来の技術】従来一般に採用されているこの種変圧器
用保護継電システムにおいては、変圧器の一次側および
二次側に夫々変流器を備え、そしてこの変流器を介して
変圧器の１次側を流れる電流と２次側を流れる電流の差
を検出し、この検出値から変圧器内部の異常を検知し保
護リレーを介して受変電設備に設けられた遮断器を開放
するようにしているのが普通である。2. Description of the Related Art In a conventional protective relay system for a transformer of this type, a transformer is provided on each of a primary side and a secondary side of the transformer, and the transformer is connected via the current transformer. Detect the difference between the current flowing through the primary side and the current flowing through the secondary side, detect the abnormality inside the transformer from this detected value, and open the breaker installed in the power receiving and transforming equipment via the protection relay. It is normal that
【０００３】通常状態においては、この保護継電システ
ムで特に問題になることはないのであるが、しかしなが
らこの保護継電システムで、例えば電気炉等のように突
入電流の大きな負荷を起動しようとすると、その突入電
流の影響により、直流の重畳した交流電流が流れ、変流
器の磁心が飽和し、変流器の一次と二次が不一致となる
現象があり、保護リレーが誤動作する場合がある。Under normal conditions, there is no particular problem with this protective relay system, however, if this protective relay system is used to start a load with a large inrush current, such as an electric furnace, etc. , Due to the influence of the inrush current, AC current with superimposed DC flows, the magnetic core of the current transformer is saturated, and there is a phenomenon that the primary and secondary of the current transformer do not match, and the protection relay may malfunction. .
【０００４】従来、この誤動作を防止するために負荷の
起動状態をトリガーとし、タイマーにより時限を持たせ
る方法や外部からの信号により保護リレーの動作をロッ
クする方法などが考えられ、一部採用はされている。Conventionally, in order to prevent this malfunction, a method in which the start state of the load is used as a trigger and a time limit is set by a timer, a method of locking the operation of the protection relay by a signal from the outside, and the like have been considered. Has been done.
【０００５】なお、これに関連するものとしては、特開
昭５５−８６３２１号公報、特開昭６２−２９３９２８
号公報、特開平５−２２８３９号公報などが挙げられ
る。Incidentally, as for those related to this, JP-A-55-86321 and JP-A-62-293928.
Japanese Patent Laid-Open No. 5-22839, and the like.
【０００６】[0006]
【発明が解決しようとする課題】たしかに、この従来採
用されていたタイマーにより時限を持たせる方法、また
外部からの信号により保護リレーの動作をロックする方
法などは、そのときの運転条件によっては有効である
が、しかしながら、一般には負荷の起動装置が遠方に設
置されていることから状態を取り込めない場合があり、
また、タイマーや信号によるロックでは正常時と事故時
の区別が付かない場合もあり、本来遮断しなければなら
ない事故が発生した時であっても保護リレーの動作をロ
ックしてしまう可能性がある。また逆に、負荷起動時の
突入電流や変圧器外部における事故時の電流により、保
護リレーが動作し不要な停電を生じるなど正常な制御が
できないきらいがあった。Certainly, the method of setting a time limit by the timer and the method of locking the operation of the protection relay by a signal from the outside are effective depending on the operating conditions at that time. However, in general, since the load starter is installed far away, it may not be possible to capture the state,
In addition, there is a case where it is not possible to distinguish between a normal state and an accident by locking with a timer or a signal, and there is a possibility that the operation of the protection relay will be locked even when an accident that should be interrupted originally occurs. . On the contrary, there is a possibility that normal control cannot be performed, such as a protective relay operating due to an inrush current when starting a load or a current when an accident occurs outside the transformer, resulting in unnecessary power failure.
【０００７】本発明はこれに鑑みなされたもので、その
目的とするところは、負荷起動時の突入電流や変圧器外
部における事故時の電流により、保護リレーが誤動作す
ることがなく、不要な停電を防止して電力供給の信頼性
の向上を図ることが可能なこの種変圧器用保護継電シス
テムを提供するにある。The present invention has been made in view of the above circumstances, and an object thereof is to prevent unnecessary malfunction of a protection relay without causing malfunction of a protection relay due to an inrush current at the time of load startup or an accident current outside the transformer. It is an object of the present invention to provide a protective relay system for this type of transformer capable of preventing the above and improving the reliability of power supply.
【０００８】[0008]
【課題を解決するための手段】すなわち本発明は、保護
継電システムに、変流器の磁心の磁気飽和を検出する磁
気飽和検出装置と、変流器の差電流の発生から変流器磁
心の飽和までの時間を計測する飽和時間計時装置と、そ
れに計測時間値が所定値を越えたときに遮断器への開放
指令を発する判定装置とを設け、変圧器の１次と２次の
差電流の発生から、変流器の磁心の飽和までの時間を検
出してその値が規準時間以下である場合には、遮断器へ
の開放指令はロックされるようになし所期の目的を達成
するようにしたものである。That is, the present invention provides a protective relay system, a magnetic saturation detecting device for detecting magnetic saturation of a magnetic core of a current transformer, and a current transformer magnetic core for generating a differential current of the current transformer. Is equipped with a saturation time measuring device for measuring the time until saturation and a judgment device for issuing an opening command to the circuit breaker when the measured time value exceeds a predetermined value. The time from the generation of current to the saturation of the magnetic core of the current transformer is detected, and if the value is less than the reference time, the open command to the circuit breaker is not locked and the intended purpose is achieved. It is something that is done.
【０００９】[0009]
【作用】すなわちこのように形成された保護リレーの誤
動作防止装置であると、負荷の起動信号を使用しないこ
とから、負荷起動装置が遠方にあり信号の取り込みが不
可能な場合であっても、変圧器内部の事故とそれ以外の
負荷起動及び変圧器外部事故を区別することができ、し
たがって負荷起動時の突入電流や変圧器外部における事
故時の電流による保護リレーの誤動作はなく、不要な停
電を防止して電力供給の信頼性の向上を図ることが可能
となる。In other words, the protective relay malfunction prevention device thus formed does not use the load start signal, so that even if the load start device is located far away and signal acquisition is impossible, It is possible to distinguish between an internal accident of the transformer and other external load start-up and transformer external accidents.Therefore, there is no malfunction of the protection relay due to inrush current at load start-up or current outside the transformer, and unnecessary power failure. It becomes possible to improve the reliability of the power supply by preventing the above.
【００１０】[0010]
【実施例】以下図示した実施例に基づいて本発明を詳細
に説明する。図１には、その変圧器用保護継電システム
が適用された受変電設備が線図示されている。１が電源
であり、４が変圧器、８が負荷である。なお、二転鎖線
枠で示す９は保護リレー、１０は誤動作防止装置、すな
わち保護装置を示している。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiments. In FIG. 1, a power receiving and transforming facility to which the protective relay system for a transformer is applied is diagrammatically illustrated. 1 is a power supply, 4 is a transformer, and 8 is a load. The double-chain line frame 9 indicates a protection relay, and 10 indicates a malfunction prevention device, that is, a protection device.
【００１１】電源１は遮断器２を介して変圧器４の１次
側端子に接続され、変圧器４の２次側端子は、遮断器６
および７（７１〜７５）を介して負荷群８に接続されて
いる。さらに、電源１から変圧器４に流入する電流を検
出するために、変圧器４の１次側端子には変流器３を配
され、また変圧器４から流出する電流を検出するため
に、変圧器４の２次側端子には変流器５が配されてい
る。The power source 1 is connected to the primary side terminal of the transformer 4 via the circuit breaker 2, and the secondary side terminal of the transformer 4 is connected to the circuit breaker 6
And 7 (71 to 75) to the load group 8. Furthermore, in order to detect the current flowing from the power source 1 into the transformer 4, a current transformer 3 is arranged at the primary side terminal of the transformer 4, and in order to detect the current flowing out from the transformer 4, A current transformer 5 is arranged at the secondary side terminal of the transformer 4.
【００１２】変流器３および変流器５の２次側端子３
ａ，５ａは保護リレー９に接続され、３次側端子３ｂ，
５ｂは変流器の磁心の飽和を検出する誤動作防止装置１
０の飽和検出装置Ａ１，Ａ２に接続されている。また、
保護リレー９の動作コイル９ａは、誤動作防止装置１０
の差電流発生検出装置Ａ３に接続されている。Secondary terminal 3 of current transformer 3 and current transformer 5
a and 5a are connected to the protection relay 9 and are connected to the tertiary side terminal 3b,
5b is a malfunction prevention device 1 for detecting the saturation of the magnetic core of the current transformer.
It is connected to zero saturation detection devices A1 and A2. Also,
The operation coil 9a of the protection relay 9 has a malfunction prevention device 10
Is connected to the differential current generation detection device A3.
【００１３】保護リレー９は、前記２つの変流器の２次
側端子から出力される電流信号を比較処理し変圧器内部
において発生した事故を検出して、必要に応じ接点９ｂ
を閉じ、遮断器２および６に開放指令９ｃ，９ｄを送出
する。The protection relay 9 compares the current signals output from the secondary side terminals of the two current transformers, detects an accident occurring inside the transformer, and contacts 9b as necessary.
Is closed, and open commands 9c and 9d are sent to the circuit breakers 2 and 6.
【００１４】ところが前述もしたように、負荷８が起動
した場合に、通常の交流電流に直流電流が重畳した電流
が変流器３，５の１次側に流れ、変流器３および５に使
用されている磁心が、飽和現象を起こす場合がある。す
なわち変流器の磁心が飽和すると、変流器２次側端子か
ら出力される電流信号は、変流器の１次側の電流を忠実
に再現できず、歪が発生する。負荷８の起動時には、遮
断器の開放は不要であるにも拘らず、電流信号の歪によ
り、保護リレー９の動作コイル９ａに差電流が流れ、変
圧器４内部において、事故が発生したと誤判断し遮断器
２および６を開放して負荷が全停電するケースがあると
云うことである。However, as described above, when the load 8 is started, the current in which the direct current is superimposed on the normal alternating current flows to the primary side of the current transformers 3 and 5, and flows into the current transformers 3 and 5. The magnetic core used may cause a saturation phenomenon. That is, when the magnetic core of the current transformer is saturated, the current signal output from the secondary side terminal of the current transformer cannot faithfully reproduce the current on the primary side of the current transformer and distortion occurs. Although it is not necessary to open the circuit breaker at the time of starting the load 8, a difference current flows through the operating coil 9a of the protection relay 9 due to the distortion of the current signal, and it is mistaken that an accident has occurred inside the transformer 4. It is said that there is a case in which the load is completely cut off by making a judgment and opening the circuit breakers 2 and 6.
【００１５】この保護リレー９の誤判断による不必要な
全停電を防止するため次のようにするのである。すなわ
ち、誤動作防止装置１０において、保護リレー９の動作
コイル９ａに差電流が発生してから変流器３または５の
磁心が飽和するまでの時間を計測しておき、この時間が
規準時間内の場合には負荷の突入電流または変圧器外部
の事故と判断し、保護リレー９から誤送出された遮断器
２および６への開放指令９ｃ，９ｄを、無効とするよう
に接点１０ａにより遮断する。In order to prevent an unnecessary total power failure due to an erroneous judgment of the protection relay 9, the following is done. That is, in the malfunction prevention device 10, the time from the generation of the differential current in the operating coil 9a of the protection relay 9 to the saturation of the magnetic core of the current transformer 3 or 5 is measured, and this time is within the reference time. In this case, it is determined that the load is an inrush current or an accident outside the transformer, and the opening commands 9c and 9d to the circuit breakers 2 and 6 erroneously sent from the protection relay 9 are interrupted by the contact 10a so as to be invalid.
【００１６】ここで、誤動作防止装置の構成および判定
方法についてもう少し詳しく図２から図４に基づき説明
すると、飽和検出装置Ａ１およびＡ２と差電流検出装置
Ａ３は、それぞれカウンタＡ４の入力端に接続され、差
電流発生から飽和発生までの時間差Ｔ１が計測され、判
定装置Ａ７の１つの入力端に接続される。Now, the structure of the malfunction preventing device and the judging method will be described in more detail with reference to FIGS. 2 to 4. The saturation detecting devices A1 and A2 and the differential current detecting device A3 are connected to the input terminals of the counter A4, respectively. The time difference T1 from the generation of the difference current to the generation of the saturation is measured and connected to one input end of the determination device A7.
【００１７】判定装置Ａ７のもう１つの入力端には、可
変の規準時間入力器Ａ５と規準時間記憶装置Ａ６が接続
される。判定装置Ａ７では、差電流発生から飽和発生ま
での時間差Ｔ１と規準時間Ｔ２を比較し、前者が後者の
時間以下の場合に、変圧器４の外部事故電流または負荷
８の突入電流による変流器３または５の飽和と判断し、
無効信号ｄが出力され接点１０ａを開き、保護リレー９
が誤動作しても開放指令９ｃ，９ｄは遮断器２および６
に到達しない。A variable reference time input device A5 and a reference time storage device A6 are connected to the other input terminal of the judging device A7. The determination device A7 compares the time difference T1 from the generation of the differential current to the generation of the saturation with the reference time T2, and when the former is the latter time or less, the current transformer due to the external fault current of the transformer 4 or the inrush current of the load 8. Judged as 3 or 5 saturation,
The invalid signal d is output, the contact 10a is opened, and the protection relay 9
Even if the malfunction occurs, the opening commands 9c and 9d are issued to the circuit breakers 2 and 6
Does not reach
【００１８】また、前者が後者の時間以上の場合には、
変圧器４の内部事故と判断し、無効信号ｄが出力され
ず、接点１０ａは閉じたままとなり開放指令９ｃ，９ｄ
は遮断器２および６に到達する。When the former is longer than the latter time,
It is determined that the transformer 4 has an internal accident, the invalid signal d is not output, the contact 10a remains closed, and the opening commands 9c and 9d are issued.
Reaches circuit breakers 2 and 6.
【００１９】次に飽和と電流の関係について説明する。
直流電流の重畳と、磁心の飽和および変流器２次側の出
力の歪との関係を波形により示すと図５から図７に示す
ような波形となる。すなわち交流電流に直流電流が重畳
した場合には、残留磁気により磁心中の磁束密度が図５
に示すように増加し、図６の磁心のＢ−Ｈ特性曲線に示
される飽和磁束密度を超過すると、変流器１次側の電流
が変化しても、磁心中の磁束密度が増加できないため、
変流器２次側から出力される信号は、変流器の１次側の
電流を忠実に再現できず、歪が発生する。Next, the relationship between saturation and current will be described.
The relationship between the superposition of the DC current and the saturation of the magnetic core and the distortion of the output of the secondary side of the current transformer is represented by waveforms as shown in FIGS. 5 to 7. That is, when the direct current is superposed on the alternating current, the magnetic flux density in the magnetic core is reduced by the residual magnetism as shown in FIG.
6 and exceeds the saturation magnetic flux density shown in the BH characteristic curve of the magnetic core of FIG. 6, the magnetic flux density in the magnetic core cannot be increased even if the current on the primary side of the current transformer changes. ,
The signal output from the secondary side of the current transformer cannot faithfully reproduce the current on the primary side of the current transformer, resulting in distortion.
【００２０】次に、上記現象を変圧器用保護継電システ
ムについて考えると、図８から図１１のようになる。す
なわち正常運転中、磁心が飽和していない場合には、変
流器３および５の１次電流Ｉ１，Ｉ２と２次電流ｉ１，
ｉ２は、同じ大きさで同方向の電流が流れるため、差電
流ｉ３は流れない。しかし、変圧器４の内部で事故が発
生した場合Ｉ２はＩ１と逆方向に流れ、更に、事故電流
により変流器５の磁心が飽和しｉ２に歪が生じる。Next, considering the above phenomenon in a protective relay system for a transformer, it becomes as shown in FIGS. That is, during normal operation, when the magnetic core is not saturated, the primary currents I1 and I2 and the secondary currents i1 of the current transformers 3 and 5 are
Since the current i2 has the same magnitude and flows in the same direction, the difference current i3 does not flow. However, when an accident occurs inside the transformer 4, I2 flows in the opposite direction to I1, and the accident current saturates the magnetic core of the current transformer 5 to cause distortion in i2.
【００２１】事故発生時にｉ１とｉ２は逆方向に流れる
ため、差電流ｉ３が同時に流れ始めるが、飽和は遅れて
発生するため、そこに時間差が生じてくる。一方、負荷
の突入電流や変圧器外部で事故が発生した場合は、Ｉ１
とＩ２は同方向に流れているが、突入電流や事故電流に
より磁心が飽和しｉ２に歪が生じる。よって、ｉ１とｉ
２には差が生じ、差電流ｉ３が流れ始める。つまり、飽
和発生と同時に差電流ｉ３が流れ始めるので、ほとんど
時間差が生じない。よって、この時間差を検出すること
により、変圧器４の内部事故、外部事故等の判断が可能
となる。When an accident occurs, i1 and i2 flow in opposite directions, so that the differential current i3 begins to flow at the same time, but saturation occurs with a delay, so that a time difference occurs there. On the other hand, if an inrush current of the load or an accident occurs outside the transformer, I1
Although I2 and I2 are flowing in the same direction, the magnetic core is saturated due to the inrush current or the fault current, and distortion occurs in i2. Therefore, i1 and i
2, a difference occurs, and the difference current i3 starts to flow. That is, since the difference current i3 starts to flow at the same time when saturation occurs, there is almost no time difference. Therefore, by detecting this time difference, it is possible to judge an internal accident, an external accident, etc. of the transformer 4.
【００２２】次に、誤動作防止装置１０の飽和検出装置
Ａ１およびＡ２の詳細な構成を、図１２により説明す
る。ここでは、図１中の変流器５と飽和検出装置Ａ２の
１相分を取り出して説明を行う。この図において、変流
器５は、磁心１２，２次巻線５ａ，３次巻線５ｂにより
構成され、リング状の磁心１２の中心を１次電流、すな
わち変圧器４の２次側電流が流れる導体１１が貫通す
る。Next, the detailed structure of the saturation detection devices A1 and A2 of the malfunction prevention device 10 will be described with reference to FIG. Here, one phase of the current transformer 5 and the saturation detection device A2 in FIG. 1 will be taken out and described. In this figure, the current transformer 5 is composed of a magnetic core 12, a secondary winding 5a, and a tertiary winding 5b. The primary current, that is, the secondary side current of the transformer 4 is at the center of the ring-shaped magnetic core 12. The flowing conductor 11 penetrates.
【００２３】３次巻線５ｂは、飽和検出装置Ａ２に接続
される。飽和検出装置Ａ２の内部は次のように構成され
る。３次巻線５ｂが接続された端子には、交流定電流源
装置Ａ２ａおよび、上記定電流源装置Ａ２ａの使用周波
数を選択的に通過させるバンドパスフィルターを備えた
電圧検出器Ａ２ｂが接続される。The tertiary winding 5b is connected to the saturation detection device A2. The inside of the saturation detection device A2 is configured as follows. The terminal to which the tertiary winding 5b is connected is connected to an AC constant current source device A2a and a voltage detector A2b provided with a bandpass filter that selectively passes the working frequency of the constant current source device A2a. .
【００２４】電圧検出器Ａ２ｂは、その両端に接続され
た３次巻線５ｂ両端の電圧に比例した直流電圧を出力
し、その出力は比較器Ａ２ｄの１つの入力端に接続され
る。比較器Ａ２ｄの、もう１つの入力端には、可変の規
準電圧発生器Ａ２ｃが接続される。比較器Ａ２ｄでは、
電圧検出器Ａ２ｂの出力と、規準電圧発生器Ａ２ｃの出
力を比較し、前者が後者よりも小さい場合に信号Ａ２ｅ
が出力される。The voltage detector A2b outputs a DC voltage proportional to the voltage across the tertiary winding 5b connected across the output of the voltage detector A2b, and its output is connected to one input end of the comparator A2d. A variable reference voltage generator A2c is connected to the other input terminal of the comparator A2d. In the comparator A2d,
The output of the voltage detector A2b is compared with the output of the reference voltage generator A2c, and if the former is smaller than the latter, the signal A2e
Is output.
【００２５】次に、上記装置により変流器の磁心の飽和
を検出する原理およびその方法について図１３から図１
５に基づき説明する。Next, the principle and method for detecting the saturation of the magnetic core of the current transformer by the above apparatus will be described with reference to FIGS.
It will be described based on 5.
【００２６】磁心が飽和していない場合には、変流器の
１次電流Ｉ１と、誤動作防止装置Ａ２内部の交流定電流
源装置Ａ２ａから変流器の３次巻線１２ｂに流される高
周波電流Ｉ３の合成として、変流器の２次巻線１２ａに
は図中Ｉ２で示す電流が流れる。Ｉ３の周波数は、フィ
ルタにより、商用電源の周波数と分離することが可能な
周波数、例えば５００Ｈｚ〜１０ｋＨｚ程度が使用され
る。When the magnetic core is not saturated, the primary current I1 of the current transformer and the high-frequency current flowing from the AC constant current source device A2a inside the malfunction prevention device A2 to the tertiary winding 12b of the current transformer. As a combination of I3, a current I2 in the figure flows through the secondary winding 12a of the current transformer. As the frequency of I3, a frequency that can be separated from the frequency of the commercial power source by a filter, for example, about 500 Hz to 10 kHz is used.
【００２７】保護リレー９においては、変流器の２次巻
線５ａに流れる図中Ｉ２で示される電流を入力し、低域
通過フィルターにより、交流定電流源装置Ａ２ａから出
力される高周波電流成分を除去して処理に使用する。一
方、飽和検出器内部においては、電圧検出器Ａ２ｂ両端
には、図中Ｖ３で示される電圧が発生し、バンドパスフ
ィルターにより交流定電流源装置Ａ２ａから出力される
高周波電流成分のみを抽出した電圧に比例した直流電圧
が、電圧検出器Ａ２ｂから出力される。In the protection relay 9, the current I2 in the figure flowing in the secondary winding 5a of the current transformer is input, and the high-frequency current component output from the AC constant current source device A2a by the low-pass filter. Used for processing. On the other hand, inside the saturation detector, a voltage indicated by V3 in the figure is generated across the voltage detector A2b, and the voltage obtained by extracting only the high frequency current component output from the AC constant current source device A2a by the bandpass filter. A DC voltage proportional to is output from the voltage detector A2b.
【００２８】この時、磁心中に発生する磁束密度は、図
中のＢ−Ｈ特性曲線に示すように、高周波電流による部
分的な微小ヒステリシスループを伴った、商用周波数
の、大きなヒステリシスループを描く。電圧検出器Ａ２
ｂから出力される直流電圧は、前記部分的な微小ヒステ
リシスループの磁束密度の変化幅に比例する。At this time, the magnetic flux density generated in the magnetic core draws a large hysteresis loop of commercial frequency accompanied by a partial minute hysteresis loop due to a high frequency current, as shown by the BH characteristic curve in the figure. . Voltage detector A2
The DC voltage output from b is proportional to the change width of the magnetic flux density of the partial minute hysteresis loop.
【００２９】さて、直流が重畳した電流が変流器１次に
流れた場合には、前述のように磁心中の磁束密度が増加
し、Ｂ−Ｈ特性曲線の飽和点に達する。この時、前記部
分的な微小ヒステリシスループの磁束密度の変化幅は、
微小ヒステリシスループがＢ−Ｈ特性曲線の飽和部分で
変化するため、交流定電流源装置Ａ２ａから出力される
高周波電流値が同一であるならば、磁心の飽和が無い場
合に比べ小さな値となり、したがって、電圧検出器Ａ２
ｂから出力される直流電圧も小さくなる。When a DC-superimposed current flows to the primary side of the current transformer, the magnetic flux density in the magnetic core increases as described above and reaches the saturation point of the BH characteristic curve. At this time, the change width of the magnetic flux density of the partial minute hysteresis loop is
Since the minute hysteresis loop changes in the saturated portion of the B-H characteristic curve, if the high frequency current value output from the AC constant current source device A2a is the same, the value becomes smaller than that in the case where there is no saturation of the magnetic core. , Voltage detector A2
The DC voltage output from b also becomes small.
【００３０】したがって、規準電圧発生器Ａ２ｃの出力
を調整し、磁心の飽和がない場合に電圧検出器Ａ２ｂか
ら出力される直流電圧よりも小さく、また、磁心が飽和
した場合に電圧検出器Ａ２ｂから出力される直流電圧よ
りも大きく設定すれば、磁心が飽和した場合のみ、信号
Ａ２ｅが出力されることになる。Therefore, the output of the reference voltage generator A2c is adjusted to be smaller than the DC voltage output from the voltage detector A2b when there is no saturation of the magnetic core, and from the voltage detector A2b when the magnetic core is saturated. If it is set higher than the output DC voltage, the signal A2e will be output only when the magnetic core is saturated.
【００３１】次に、差電流検出装置の構成およびその作
動を図１６、図１７により説明する。変流器２次電流ｉ
１およびｉ２が保護リレー９に入力され、ｉ１とｉ２に
差が生じると動作コイル９ａに差電流ｉ３が流れる。動
作コイル９ａに発生する交流電圧ｖ１を差電流検出装置
Ａ３に取り込み、整流し直流に変換され、装置内に設け
た抵抗の両端に直流電圧ｖ２が発生し、比較器に１つの
入力端に入力される。もう一つの入力端には、規準電圧
ｖ３が入力される。前者が後者の電圧値以上となった場
合いに、差電流発生信号Ａ３ａが出力される。Next, the structure and operation of the differential current detecting device will be described with reference to FIGS. Current transformer secondary current i
When 1 and i2 are input to the protection relay 9 and a difference occurs between i1 and i2, a difference current i3 flows through the operating coil 9a. The AC voltage v1 generated in the operating coil 9a is taken into the difference current detection device A3, rectified and converted into DC, and a DC voltage v2 is generated at both ends of the resistor provided in the device, and is input to one input end of the comparator. To be done. The reference voltage v3 is input to the other input terminal. When the former becomes equal to or higher than the latter voltage value, the differential current generation signal A3a is output.
【００３２】よって、保護リレー９から遮断器２および
６に開放指令９ｃ，９ｄが、上記の通り制御される信号
Ａ２ｅおよび、Ａ３ａが誤動作防止装置１０で差電流発
生からの時間差を比較処理された接点１０ａを経由して
出力すれば、保護リレー９の誤った開放指令は、遮断器
２および６に到達しない。したがって、保護リレーの誤
動作による不必要な停電を防止することが出来る。Therefore, the opening instructions 9c and 9d from the protection relay 9 to the circuit breakers 2 and 6 and the signals A2e and A3a controlled as described above are compared and processed by the malfunction prevention device 10 for the time difference from the generation of the difference current. If output is made via the contact 10a, an erroneous opening command of the protection relay 9 will not reach the circuit breakers 2 and 6. Therefore, it is possible to prevent unnecessary power failure due to malfunction of the protection relay.
【００３３】[0033]
【発明の効果】以上説明してきたように本発明は、保護
継電システムに、変流器の磁心の磁気飽和を検出する磁
気飽和検出装置と、変流器の差電流の発生から変流器磁
心の飽和までの時間を計測する飽和時間計時装置、それ
に計測時間値が所定値を越えたときに遮断器への開放指
令を発する判定装置とを設け、変流器の差電流の発生か
ら変流器の磁心の飽和までの時間を検出して、この値が
規準時間以下である場合には遮断器への開放指令をロッ
クするようになしたから、たとえ負荷起動装置が遠方に
あり、信号の取り込みが不可能な場合であっても、変圧
器内部の事故とそれ以外の負荷起動及び変圧器外部事故
を区別することができ、したがって負荷起動時の突入電
流や変圧器外部における事故時の電流による保護リレー
の誤動作はなく、不要な停電を防止して電力供給の信頼
性の向上を図ることができるこの種変圧器用保護継電シ
ステムを得ることができる。As described above, the present invention provides a protective relay system, a magnetic saturation detecting device for detecting magnetic saturation of a magnetic core of a current transformer, and a current transformer for generating a differential current of the current transformer. A saturation time measuring device that measures the time until saturation of the magnetic core and a determination device that issues an opening command to the circuit breaker when the measured time value exceeds a predetermined value are provided to change from the occurrence of the differential current of the current transformer. Since the time until the saturation of the magnetic core of the current transformer is detected and the value is less than the reference time, the opening command to the circuit breaker is locked. Even if it is impossible to capture the load, it is possible to distinguish between the internal accident of the transformer and the other load startup and external transformer failures. There is no malfunction of the protection relay due to current, It is possible to prevent the main power failure to obtain this type transformers protective relay system which can improve the reliability of power supply.
【図１】本発明の受変電設備の変圧器用保護継電システ
ムの一実施例を示す系統線図である。FIG. 1 is a system diagram showing an embodiment of a protective relay system for a transformer of a power receiving and transforming facility of the present invention.
【図２】本発明の変圧器用保護継電システムの保護装置
の一実施例を示す線図である。FIG. 2 is a diagram showing an embodiment of a protective device for a protective relay system for a transformer according to the present invention.
【図３】本発明の保護装置の判定方法を説明するための
フローチャートである。FIG. 3 is a flowchart for explaining a determination method of the protection device of the present invention.
【図４】本発明の保護装置の判定方法を説明するための
フローチャートである。FIG. 4 is a flowchart for explaining a determination method of the protection device of the present invention.
【図５】直流電流の重畳と磁心の飽和の関係を示す波形
図である。FIG. 5 is a waveform diagram showing a relationship between superposition of direct current and saturation of a magnetic core.
【図６】磁心の飽和の関係を示す特性図である。FIG. 6 is a characteristic diagram showing a saturation relationship of a magnetic core.
【図７】変流器２次側の出力の歪の関係を波形により示
した図である。FIG. 7 is a diagram showing a waveform of a relation of distortion of an output on the secondary side of the current transformer.
【図８】受変電設備の変圧器用保護継電システムの一実
施例を示す系統線図である。FIG. 8 is a system diagram showing an example of a protective relay system for a transformer of a power receiving and transforming facility.
【図９】本発明による装置の判定方法を電流波形で示し
た図である。FIG. 9 is a diagram showing a method of determining an apparatus according to the present invention by a current waveform.
【図１０】本発明による装置の判定方法を電流波形で示
した図である。FIG. 10 is a diagram showing a method of determining an apparatus according to the present invention by a current waveform.
【図１１】本発明による装置の判定方法を説明するため
のフローチャートである。FIG. 11 is a flowchart illustrating a method for determining a device according to the present invention.
【図１２】本発明による保護装置内の飽和検出装置の一
実施例を示した線図である。FIG. 12 is a diagram showing an embodiment of a saturation detection device in a protection device according to the present invention.
【図１３】変流器における各部電圧、電流の関係を示す
線図である。FIG. 13 is a diagram showing the relationship between the voltage and current of each part in the current transformer.
【図１４】鉄心が飽和していない場合の各部の電流、電
圧波形を示した図である。FIG. 14 is a diagram showing current and voltage waveforms at various portions when the iron core is not saturated.
【図１５】鉄心が飽和した場合の各部の電流、電圧波形
を示した図である。FIG. 15 is a diagram showing current and voltage waveforms at various portions when the iron core is saturated.
【図１６】本発明による保護装置内の差電流検出装置の
１例を示した線図である。FIG. 16 is a diagram showing an example of a differential current detection device in a protection device according to the present invention.
【図１７】本発明による保護装置内の差電流検出装置に
おける波形図である。FIG. 17 is a waveform diagram in the differential current detection device in the protection device according to the present invention.
１…電源、２，６，７…遮断器、３，５…変流器、３
ａ，５ａ…変流器２次巻線、３ｂ，５ｂ…変流器３次巻
線、４…変圧器、８…負荷、９…保護リレー、９ａ…動
作コイル、９ｂ…接点、９ｃ，９ｄ…開放指令、１０…
誤動作防止装置、１０ａ…接点、Ａ１，Ａ２…飽和検出
装置、Ａ３…差電流検出装置、Ａ４…カウンタ、Ａ５…
規準時間入力器、Ａ６…規準時間記憶装置、Ａ７…判定
装置、１１…導体、１２…磁心、Ａ２ａ…定電流源装
置、Ａ２ｂ…電圧検出器、Ａ２ｃ…規準電圧発生器、Ａ
２ｄ…比較器、Ａ２ｅ，Ａ３ａ…信号。1 ... Power supply, 2, 6, 7 ... Circuit breaker, 3, 5 ... Current transformer, 3
a, 5a ... Current transformer secondary winding, 3b, 5b ... Current transformer tertiary winding, 4 ... Transformer, 8 ... Load, 9 ... Protection relay, 9a ... Operating coil, 9b ... Contact, 9c, 9d … Open command, 10…
Malfunction prevention device, 10a ... Contact, A1, A2 ... Saturation detection device, A3 ... Differential current detection device, A4 ... Counter, A5 ...
Reference time input device, A6 ... Reference time storage device, A7 ... Judgment device, 11 ... Conductor, 12 ... Magnetic core, A2a ... Constant current source device, A2b ... Voltage detector, A2c ... Reference voltage generator, A
2d ... Comparator, A2e, A3a ... Signal.
Claims (10)
れた変流器と、該両変流器間の差電流を検知するととも
に、この差電流に基づき作動する保護リレーを有する保
護装置とを備え、変圧器の１次および２次側を流れる電
流差の検出により変圧器内部の異常を検知し遮断するよ
うになした受変電設備の変圧器用保護継電システムにお
いて、 前記システムに、前記変流器磁心の磁気飽和を検出する
磁気飽和検出装置と、前記変流器の差電流の発生から変
流器磁心の飽和までの時間を計測する飽和時間計時装置
と、前記計測時間値が所定値を越えたときに遮断器への
開放指令を発する判定装置とを設けたことを特徴とする
受変電設備の変圧器用保護継電システム。1. A protection having a current transformer provided on each of a primary side and a secondary side of a transformer and a protection relay for detecting a current difference between the current transformers and operating based on the current difference. A protective relay system for a transformer of a power receiving and transforming facility, which is configured to detect an abnormality inside the transformer by detecting a difference in current flowing between the primary side and the secondary side of the transformer, A magnetic saturation detecting device for detecting magnetic saturation of the current transformer magnetic core, a saturation time measuring device for measuring time from generation of a differential current of the current transformer to saturation of the current transformer magnetic core, and the measured time value A protective relay system for a transformer of a power receiving and transforming facility, which is provided with a determining device which issues an opening command to a circuit breaker when the current exceeds a predetermined value.
れた変流器と、該両変流器間の差電流を検知するととも
に、この差電流に基づき作動する保護リレーを有する保
護装置とを備え、変圧器の１次および２次側を流れる電
流差の検出により変圧器内部の異常を検知し遮断するよ
うになした受変電設備の変圧器用保護継電システムにお
いて、 前記システムに、前記変流器磁心の磁気飽和を検出する
磁気飽和検出装置と、前記変流器の差電流の発生から変
流器磁心の飽和までの時間を計測する飽和時間計時装置
と、該飽和時間計時装置の計測時間値と予め記憶装置に
入力された基準飽和時間値とを比較し、前記計測時間値
が基準飽和時間値を越えたときに遮断器への開放指令を
発する判定装置と、を設けたことを特徴とする受変電設
備の変圧器用保護継電システム。2. A protection having a current transformer provided on each of a primary side and a secondary side of the transformer and a protection relay for detecting a difference current between the two current transformers and operating based on the difference current. A protective relay system for a transformer of a power receiving and transforming facility, which is configured to detect an abnormality inside the transformer by detecting a difference in current flowing between the primary side and the secondary side of the transformer, A magnetic saturation detecting device for detecting magnetic saturation of the current transformer magnetic core, a saturation time measuring device for measuring time from generation of a differential current of the current transformer to saturation of the current transformer magnetic core, and the saturation time measuring device And a determination device that compares the measured time value of the device with a reference saturation time value input in advance in the storage device and issues an opening command to the circuit breaker when the measured time value exceeds the reference saturation time value. The transformer of the power receiving and transforming facility characterized by Protective relay system.
れた変流器と、該両変流器間の差電流を検知するととも
に、この差電流に基づき変圧器の内部異常を検知し、か
つその異常時に作動する保護リレーを有する保護装置と
を備え、前記保護リレーの動作出力により、受変電設備
に設けられた遮断器を開放するように形成されている受
変電設備の変圧器用保護継電システムにおいて、 前記システムに、前記変流器磁心の磁気飽和を検出する
磁気飽和検出装置と、前記変流器の差電流の発生から変
流器磁心の飽和までの時間を計測する飽和時間計時装置
と、該飽和時間計時装置の計測時間値と予め記憶装置に
入力された基準飽和時間値とを比較し、基準飽和時間値
内では前記保護リレーから出力される遮断器への開放指
令を無効とさせる判定装置と、を設けたことを特徴とす
る受変電設備の変圧器用保護継電システム。3. A current transformer provided on each of a primary side and a secondary side of the transformer, and a difference current between the current transformers is detected, and an internal abnormality of the transformer is detected based on the difference current. And a protection device having a protection relay that operates when there is an abnormality, and for the transformer of the power receiving and transforming equipment, which is formed so as to open the breaker provided in the power receiving and transforming equipment by the operation output of the protection relay. In the protective relay system, the system includes a magnetic saturation detection device for detecting magnetic saturation of the current transformer core, and a saturation for measuring time from generation of a differential current of the current transformer to saturation of the current transformer core. The time measuring device compares the measured time value of the saturation time measuring device with the reference saturation time value previously input to the storage device, and within the reference saturation time value, an opening command to the circuit breaker output from the protection relay. Judgment device that invalidates When transformers protection relay system power receiving and transforming equipment characterized in that it was a provided.
れた変流器と、該両変流器間の差電流を検知するととも
に、この差電流に基づき変圧器の内部異常を検知し、か
つその異常時に作動する保護リレーを有する保護装置と
を備え、前記保護リレーの動作出力により、受変電設備
に設けられた遮断器を開放するように形成されている受
変電設備の変圧器用保護継電システムにおいて、 前記システムに、前記変流器磁心の磁気飽和を検出する
磁気飽和検出装置と、前記変流器の差電流の発生から変
流器磁心の飽和までの時間を計測する飽和時間計時装置
と、該飽和時間計時装置の計時時間値と予め記憶装置に
入力された基準飽和時間値とを比較し、飽和時間計時装
置にて計測された時間が基準飽和時間値より短い場合
に、前記保護リレーから遮断器への開放指令を無効とす
る信号を出力する判定装置と、を設けたことを特徴とす
る受変電設備の変圧器用保護継電システム。4. A current transformer provided on each of a primary side and a secondary side of the transformer, and a difference current between the current transformers is detected, and an internal abnormality of the transformer is detected based on the difference current. And a protection device having a protection relay that operates when there is an abnormality, and for the transformer of the power receiving and transforming equipment, which is formed so as to open the breaker provided in the power receiving and transforming equipment by the operation output of the protection relay. In the protective relay system, the system includes a magnetic saturation detection device for detecting magnetic saturation of the current transformer core, and a saturation for measuring time from generation of a differential current of the current transformer to saturation of the current transformer core. When the time counting device and the saturation time measuring device compare the measured time value of the saturation time measuring device with a reference saturation time value previously input to the storage device, and when the time measured by the saturation time measuring device is shorter than the reference saturation time value, Shielded from the protection relay Transformers protective relay system of power receiving and transforming equipment characterized in that a determination device which outputs a signal for disabling the opening command to the vessel, the provided.
３次巻線に高周波定電流を通電する高周波電流源と、前
記変流器の３次巻線に誘起される高周波電圧成分を検出
する電圧検出部と、該電圧検出部の検出電圧と予め設定
された規準電圧値との比較を行ない、検出電圧の方が小
さい場合に磁心飽和信号を出力する比較部とにより構成
されてなる請求項１、２、３若しくは４記載の受変電設
備の変圧器用保護継電システム。5. The high frequency current source for supplying a high frequency constant current to the tertiary winding of the current transformer, and the high frequency voltage component induced in the tertiary winding of the current transformer. It is composed of a voltage detecting section for detecting and a comparing section for comparing the detected voltage of the voltage detecting section with a preset reference voltage value and outputting a magnetic core saturation signal when the detected voltage is smaller. A protective relay system for a transformer of a power receiving and transforming facility according to claim 1, 2, 3, or 4.
２次巻線に高周波定電流を通電し、この２次巻線に誘起
される高周波電圧成分により変流器磁心の飽和を検出す
るように形成されてなる請求項１、２、３若しくは４記
載の受変電設備の変圧器用保護継電システム。6. The magnetic saturation detection device applies a high frequency constant current to a secondary winding of the current transformer, and detects saturation of the current transformer magnetic core by a high frequency voltage component induced in the secondary winding. The protective relay system for the transformer of the power receiving and transforming equipment according to claim 1, 2, 3 or 4.
し、前記保護リレー内部の動作コイルに発生する電圧を
取り込み、この取り込んだ電圧を予め設定された規準電
圧と比較し、動作コイルに発生した電圧が大きい場合
に、差電流発生信号を出力するようにした請求項１、
２、３若しくは４記載の受変電設備の変圧器用保護継電
システム。7. When the differential current detection device detects a differential current, a voltage generated in an operating coil inside the protection relay is taken in, and the taken-in voltage is compared with a preset reference voltage to generate in the operating coil. A differential current generation signal is output when the voltage is large.
The protective relay system for the transformer of the power receiving and transforming equipment according to 2, 3 or 4.
た変流器と、該両変流器間の差電流を検知するととも
に、この差電流に基づき作動する保護リレーを有する保
護装置とを備え、変圧器の１次側および２次側を流れる
電流差の検出により変圧器内部の異常を検知するように
なした受変電設備の変圧器保護方法において、 前記両変流器の差電流の発生から変流器磁心の飽和まで
の時間を計測し、この計測時間値と予め準備された基準
飽和時間値とを比較し、この計測時間値が所定値を越え
たときに遮断器への開放指令を発するようにしたことを
特徴とする受変電設備の変圧器の保護方法。8. A transformer having a current transformer provided on each of a primary side and a secondary side of the transformer, and a protection relay for detecting a difference current between the two current transformers and operating based on the difference current. A transformer protection method for power receiving and transforming equipment, comprising: a protection device, wherein an abnormality inside the transformer is detected by detecting a current difference flowing between the primary side and the secondary side of the transformer. The time from the generation of the differential current to the saturation of the current transformer magnetic core is measured, this measured time value is compared with the reference saturation time value prepared in advance, and when this measured time value exceeds the specified value, the circuit is cut off. A method for protecting a transformer of a power receiving and transforming facility, characterized in that an opening command is issued to the transformer.
流れる電流との差電流を検知し、この差電流に基づき変
圧器内部の異常を検知するようになした受変電設備の変
圧器保護方法において、 前記両変流器の差電流の発生から変流器磁心の飽和まで
の時間を計測し、この計測時間値と予め準備された基準
飽和時間値とを比較し、この計測時間が所定値を越えた
ときに変圧器の内部異常と判断し遮断するようにしたこ
とを特徴とする受変電設備の変圧器保護方法。9. A power receiving and transforming facility which detects a difference between a current flowing through a primary side of a transformer and a current flowing through a secondary side and detects an abnormality inside the transformer based on the difference current. In the transformer protection method, the time from the generation of the difference current between the two current transformers to the saturation of the current transformer magnetic core is measured, and the measured time value is compared with a previously prepared reference saturation time value, and this measurement is performed. A method of protecting a transformer of a power receiving and transforming facility, which is characterized in that when a time exceeds a predetermined value, it is judged to be an internal abnormality of the transformer and is shut off.
に流れる電流との差電流を検知し、この差電流に基づき
変圧器内部の異常を検知し遮断するようになした受変電
設備の変圧器保護方法において、 前記両変流器の差電流の発生から変流器磁心の飽和まで
の時間を計測し、この計測時間値と予め準備された基準
飽和時間値とを比較し、この計測時間値が基準飽和時間
値より短い場合に、前記保護リレーから遮断器への開放
指令を無効とする信号を出力するようにしたことを特徴
とする受変電設備の変圧器保護方法。10. A power receiving and transforming device configured to detect a difference current between a current flowing through a primary side and a current flowing through a secondary side of a transformer, detect an abnormality inside the transformer based on the difference current, and cut off the abnormality. In the transformer protection method of equipment, the time from the generation of the current difference between the two current transformers to the saturation of the current transformer magnetic core is measured, and the measured time value and the reference saturation time value prepared in advance are compared, When the measured time value is shorter than the reference saturation time value, a signal for invalidating the opening command from the protection relay to the circuit breaker is output, and the transformer protection method for power receiving and transforming equipment is characterized.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16668294A JP3447811B2 (en) | 1994-07-19 | 1994-07-19 | Transformer protection relay system for substation equipment and transformer protection method for substation equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16668294A JP3447811B2 (en) | 1994-07-19 | 1994-07-19 | Transformer protection relay system for substation equipment and transformer protection method for substation equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0833193A true JPH0833193A (en) | 1996-02-02 |
| JP3447811B2 JP3447811B2 (en) | 2003-09-16 |
Family
ID=15835785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16668294A Expired - Fee Related JP3447811B2 (en) | 1994-07-19 | 1994-07-19 | Transformer protection relay system for substation equipment and transformer protection method for substation equipment |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3447811B2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100987164B1 (en) * | 2008-07-23 | 2010-10-11 | 한국전력공사 | Closed Loop Distribution System |
| CN102255284A (en) * | 2011-07-26 | 2011-11-23 | 重庆电力高等专科学校 | Method for realizing protection of transformer by comparing polarities of instantaneous values of current fault components |
| CN103683195A (en) * | 2012-09-11 | 2014-03-26 | 南京南瑞继保电气有限公司 | Frequency-conversion differential protection method for output transformer of SFC system |
| CN104410045A (en) * | 2014-12-05 | 2015-03-11 | 国家电网公司 | Photoelectricity and CT (Computed Tomography) mixed differential protection system and method for isolation transformer |
| WO2024253068A1 (en) * | 2023-06-05 | 2024-12-12 | 日本製鉄株式会社 | Magnetic saturation detection device, protection system, magnetic saturation detection method, and protection method |
-
1994
- 1994-07-19 JP JP16668294A patent/JP3447811B2/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100987164B1 (en) * | 2008-07-23 | 2010-10-11 | 한국전력공사 | Closed Loop Distribution System |
| CN102255284A (en) * | 2011-07-26 | 2011-11-23 | 重庆电力高等专科学校 | Method for realizing protection of transformer by comparing polarities of instantaneous values of current fault components |
| CN103683195A (en) * | 2012-09-11 | 2014-03-26 | 南京南瑞继保电气有限公司 | Frequency-conversion differential protection method for output transformer of SFC system |
| CN104410045A (en) * | 2014-12-05 | 2015-03-11 | 国家电网公司 | Photoelectricity and CT (Computed Tomography) mixed differential protection system and method for isolation transformer |
| CN104410045B (en) * | 2014-12-05 | 2017-07-14 | 国家电网公司 | The isolating transformer differential protective system and method for a kind of photoelectricity CT mixing |
| WO2024253068A1 (en) * | 2023-06-05 | 2024-12-12 | 日本製鉄株式会社 | Magnetic saturation detection device, protection system, magnetic saturation detection method, and protection method |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3447811B2 (en) | 2003-09-16 |
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