【０００１】
【発明の属する技術分野】
本発明は、電力系統の変圧器内部における短絡等の事故を検出する比率差動継電器に関する。
【０００２】
【従来の技術】
電力系統の変圧器の内部事故を検出し保護する継電器としては、比率差動継電器がある。図３は、電力系統の変圧器３を比率差動継電器６で保護する場合の系統図である。変圧器３の一次側は一次側遮断器２を介して発電機等の電源１に接続され、また二次側は二次側遮断器７を介して送電線や配電線などの負荷側に接続されている。変圧器３の一次側には一次側変流器４が接続され、二次側には二次側変流器５が接続されて、一次側変流器４からの一次側電流Ｉ１および二次側変流器５の二次側電流Ｉ２が比率差動継電器６に入力されている。
【０００３】
比率差動継電器６は一次側電流Ｉ１および二次側電流Ｉ２を逆極性で入力し、その差電流が負荷電流に応じて設定された所定範囲を逸脱したときに変圧器の内部故障と判定するようにしている。変圧器の内部故障であると判定したときは変圧器３の一次側遮断器２および二次側遮断器７を開放し、変圧器３を電力系統から切り離す。これにより、故障区間を健全な電力系統から切り離し健全な電力系統の運用を継続できるようにしている。
【０００４】
このように、比率差動継電器６に入力される変圧器３の一次側電流Ｉ１と二次側電流Ｉ２とは、逆方向で入力されその差電流により変圧器３の内部故障を検出するようにしている。従って、一次側電流Ｉ１を検出する一次側変流器４および二次側電流Ｉ２を検出する二次側変流器５の極性は重要である。
【０００５】
【発明が解決しようとする課題】
ところが、この電流の向きが変流器４、５の極性誤りや配線ミスなどにより、同方向となった場合には、正常な故障判定演算を行うことができず、比率差動継電器６が誤動作に至ることになる。そこで、変圧器３の一次側電流Ｉ１および二次側電流Ｉ２が逆方向で比率差動継電器６に入力するように、細心の注意を払い変流器４、５の二次側回路の極性を定め、さらには運用開始前の確認試験を行っている。しかし、確認試験では実際に変圧器３に電流を流して試験を行うことが事実上できないので、変流器４、５の極性誤りや配線ミスを完全に防止できないことがあり、運用開始直後に比率差動継電器６の誤動作が起きる可能性がある。
【０００６】
本発明の目的は、変圧器の一次側電流および二次側電流の向きが間違った方向で入力されても誤動作を防止でき、変圧器の内部故障発生時は正常に動作することができる差動比率継電器を提供することである。
【０００７】
【課題を解決するための手段】
請求項１の発明に係る比率差動継電器は、電力系統に設けられた変圧器の一次側および二次側に変流器をそれぞれ設け、これら変流器より流入する一次側電流と二次側電流との位相差および大きさに基づいて変圧器の内部故障と判定する比率差動継電器において、前記一次側電流と二次側電流との極性が逆方向として故障判定演算を行う第１の内部故障検出手段と、前記一次側電流と二次側電流との極性が同方向として故障判定演算を行う第２の内部故障検出手段と、前記一次側電流と二次側電流との極性を判定し極性が逆方向であるときは前記第１の内部故障検出手段を選択し極性が同方向であるときは前記第２の内部故障検出手段を選択する演算処理手段と、前記演算処理手段で選択された第１の内部故障検出手段または第２の内部故障検出手段の故障判定演算結果を外部に出力する外部出力手段と、前記演算処理手段で選択され使用中の第１の内部故障検出手段または第２の内部故障検出手段を表示する表示手段とを備えたことを特徴とする。
【０００８】
請求項１の発明に係る比率差動継電器においては、演算処理手段は、一次側電流と二次側電流との極性を判定し極性が逆方向であるときは第１の内部故障検出手段を選択し、極性が同方向であるときは第２の内部故障検出手段を選択して、変圧器の故障判定演算を行う。そして、第１の内部故障検出手段または第２の内部故障検出手段の故障判定演算結果を外部出力手段を介して外部に出力する。また、表示手段には、演算処理手段で選択され使用中の第１の内部故障検出手段または第２の内部故障検出手段を表示する。
【０００９】
請求項２の発明に係る比率差動継電器は、請求項１の発明において、前記変圧器の一次側電流が定格負荷未満であるか否かを検出する負荷量検出手段を設け、前記演算処理手段は、前記負荷量検出手段により前記変圧器の一次側電流が定格負荷未満であることが検出されているときに、前記一次側電流と二次側電流との極性を判定し、第１の内部故障検出手段または第２の内部故障検出手段のいずれかを選択し、前記負荷量検出手段により前記変圧器の一次側電流が定格負荷以上であることが検出されているときは、第１の内部故障検出手段および第２の内部故障検出手段の双方を選択することを特徴とする。
【００１０】
請求項２の発明に係る比率差動継電器においては、請求項１の発明の発明の作用に加え、演算処理手段は、負荷量検出手段により変圧器の一次側電流が定格負荷未満であることが検出されているときに、一次側電流と二次側電流との極性を判定し、その極性に基づいて、第１の内部故障検出手段または第２の内部故障検出手段のいずれかを選択する。一方、負荷量検出手段により変圧器の一次側電流が定格負荷以上であることが検出されているときは、第１の内部故障検出手段および第２の内部故障検出手段の双方を選択する。これにより、定格負荷以上の運転状態では、第１の内部故障検出手段または第２の内部故障検出手段のいずれかが動作したときに変圧器を電力系統から切り離す。
【００１１】
請求項３の発明に係る比率差動継電器は、請求項１または請求項２の発明において、第１の内部故障検出手段または第２の内部故障検出手段のいずれかを選択設定する設定手段を設け、前記演算処理手段は、前記設定手段で設定された第１の内部故障検出手段または第２の内部故障検出手段を優先して使用することを特徴とする。
【００１２】
請求項３の発明に係る比率差動継電器においては、請求項１または請求項２の発明の作用に加え、演算処理手段は、設定手段で設定された第１の内部故障検出手段または第２の内部故障検出手段を優先して使用する。
【００１３】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。図１は本発明の実施の形態に係る比率差動継電器のブロック構成図である。一次側変流器４で検出された一次側電流Ｉ１および二次側変流器５で検出された二次側電流Ｉ２は、比率差動継電器６の入力変換手段８を介してそれぞれのアナログデジタル変換手段９ａ、９ｂに入力される。アナログデジタル変換手段９ａ、９ｂに取込まれたアナログ量はデジタルデータに変換されデータバス１６に導かれる。データバス１６に導かれたデジタルデータは、第１の内部故障検出手段１０ａ、第２の内部故障検出手段１０ｂ、負荷量検出手段１１、演算処理手段１２に取込まれる。
【００１４】
第１の内部故障検出手段１０ａは、既存の比率差動継電器６の故障判定演算と同様な故障判定演算を行うものである。つまり、変圧器３の一次側電流Ｉ１に対し二次側電流Ｉ２を逆方向として故障判定演算を行い、変圧器３の内部故障を検出する。一方、第２の内部故障検出手段１０ｂは、変圧器３の一次側電流Ｉ１に対し二次側電流Ｉ２を同方向として故障判定演算を行い、変圧器３の内部故障を検出するものである。つまり、一次側変流器４または二次側変流器５の接続が誤接続により、極性が逆になっていた場合であっても適正に故障判定演算を行えるようにしたものである。
【００１５】
負荷量検出手段１１は、変圧器３の一次側電流Ｉ１が変圧器３の定格負荷電流未満であることを検出するものである。変圧器３の運用開始時には負荷電流として定格負荷電流未満の電流が印加されるので、運用開始時において変流器４、５の極性を適正に判別できるようにするためである。
【００１６】
演算処理手段１２は、負荷量検出手段１１で検出された負荷量が整定値未満である場合に、変圧器３の一次側電流Ｉ１と二次側電流Ｉ２との極性を判別し、その極性に基づいて、第１の内部故障検出手段１０ａまたは第２の内部故障検出手段１０ｂのいずれかを選択する。一次側電流Ｉ１に対し二次側電流Ｉ２が逆極性の場合には、第２の内部故障検出手段１０ｂをロックし第１の内部故障検出手段１０ａを選択する。一方、一次側電流Ｉ１に対し二次側電流Ｉ２が同極性の場合には、第１の内部故障検出手段１０ａをロックし第２の内部故障検出手段１０ｂを選択する。これにより、極性が正しい側の内部故障検出手段を使用し、誤った極性側の内部故障検出手段をロックするようにしている。
【００１７】
一方、負荷量検出手段１１により変圧器３の一次側電流が定格負荷以上であることが検出されているときは、第１の内部故障検出手段１０ａおよび第２の内部故障検出手段１０ｂの双方を選択する。これにより、定格負荷以上の運転状態では、第１の内部故障検出手段１０ａまたは第２の内部故障検出手段１０ｂのいずれかが動作したときに変圧器３を電力系統から切り離すことになり、保護の強化を図っている。
【００１８】
外部出力手段１３は、第１の内部故障検出手段１０ａまたは第２の内部故障検出手段１０ｂが検出した内部故障をデータバス１６を介して取込み、遮断器２、７に開放指令を出力するものである。表示手段１４は、設定手段１５で設定された内容を表示するほか、どちらの内部故障検出手段が使用されているのかを表示する。設定手段１５は、第１の内部故障検出手段１０ａまたは第２の内部故障検出手段１０ｂの動作条件等の設定を行うほか、負荷量検出手段１１の負荷量の設定も行う。
【００１９】
また、第１の内部故障検出手段１０ａまたは第２の内部故障検出手段１０ｂのどちらの内部故障検出手段を使用するかの設定もできるようになっている。例えば、運用開始時に演算処理手段１２で自動選択された内部故障検出手段が正しい極性であるとして、それ以降の運転においては、その内部故障検出手段を優先して使用する場合に、設定手段１５にその内部故障検出手段を設定する。
【００２０】
図２は、本発明の実施の形態における比率差動継電器の動作を示すフローチャートである。まず、設定手段１５に第１の内部故障検出手段１０ａが使用する内部故障検出手段として設定されているか否か判定する（Ｓ１）。第１の内部故障検出手段１０ａが使用する内部故障検出手段として設定されているときは、第１の内部故障検出手段１０ａを使用し（Ｓ２）、表示手段１４に第１の内部故障検出手段１０ａの使用を表示する（Ｓ３）。そして、変圧器３の内部故障が検出されれば（Ｓ４）、外部出力手段１３から遮断器２、７の開放指令を出力し変圧器３を電力系統から切り離す保護動作を行う（Ｓ５）。
【００２１】
ステップＳ１の判定にて第１の内部故障検出手段１０ａの使用でないと判定されたときは、設定手段１５に第２の内部故障検出手段１０ｂが使用する内部故障検出手段として設定されているか否か判定する（Ｓ６）。第２の内部故障検出手段１０ｂが使用する内部故障検出手段として設定されているときは、第２の内部故障検出手段１０ｂを使用し（Ｓ７）、表示手段１４に第２の内部故障検出手段１０ｂの使用を表示する（Ｓ８）。そして、変圧器３の内部故障が検出されれば（Ｓ９）、外部出力手段１３から遮断器２、７の開放指令を出力し変圧器３を電力系統から切り離す保護動作を行う（Ｓ５）。
【００２２】
ステップＳ６の判定にて第２の内部故障検出手段１０ｂの使用でないと判定されたときは、一次側電流Ｉ１が整定された変圧器の定格負荷電流未満か否か判定する（Ｓ１０）。定格負荷電流以上であれば、第１の内部故障検出手段１０ａおよび第２の内部故障検出手段１０ｂとも使用し（Ｓ１１）、表示手段１４に第１の内部故障検出手段１０ａおよび第２の内部故障検出手段１０ｂともに使用である旨を表示する（Ｓ１２）。そして、変圧器３の内部故障が検出されれば（Ｓ１３）、外部出力手段１３から遮断器２、７の開放指令を出力し変圧器３を電力系統から切り離す保護動作を行う（Ｓ５）。
【００２３】
ステップＳ１０の判定にて、一次側電流Ｉ１が整定された変圧器の定格負荷電流未満であると判定されたときは、一次側電流Ｉ１に対し二次側電流Ｉ２の極性が逆方向であるか否かの判定を行う（１４）。一次側電流Ｉ１に対し二次側電流Ｉ２の極性が逆方向であるときは、第２の内部故障検出手段１０ｂをロックし（Ｓ１５）、第１の内部故障検出手段１０ａを使用する（Ｓ１６）。そして、表示手段１４に第１の内部故障検出手段１０ａの使用を表示し（Ｓ１７）、変圧器３の内部故障が検出されれば（Ｓ１８）、外部出力手段１３から遮断器２、７の開放指令を出力し変圧器３を電力系統から切り離す保護動作を行う（Ｓ５）。
【００２４】
ステップＳ１４の判定で、一次側電流Ｉ１に対し二次側電流Ｉ２の極性が逆方向でないと判定されたときは、第１の内部故障検出手段１０ａをロックし（Ｓ１９）、第２の内部故障検出手段１０ｂを使用する（Ｓ２０）。そして、表示手段１４に第２の内部故障検出手段１０ｂの使用を表示し（Ｓ２１）、変圧器３の内部故障が検出されれば（Ｓ２２）、外部出力手段１３から遮断器２、７の開放指令を出力し変圧器３を電力系統から切り離す保護動作を行う（Ｓ５）。
【００２５】
このように、本発明の実施の形態によれば、変流器４、５の極性誤りによる比率差動継電器の誤動作を防止できる。また、変流器４、５の極性を確認できたときは、その極性で正常に動作する内部故障検出手段を設定して使用できる。
【００２６】
【発明の効果】
以上述べたように本発明によれば、入力される電流の極性を検出し、その極性に応じて適切な内部故障検出手段を選択できるので、変流器の極性誤りや配線ミスなどによる運用開始直後の比率差動継電器の誤動作が防止でき、変圧器の内部故障発生時は、適正に事故を検出し保護動作を行うことができる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る比率差動継電器のブロック構成図。
【図２】本発明の実施の形態における比率差動継電器の動作を示すフローチャート。
【図３】電力系統の変圧器を比率差動継電器で保護する場合の系統図。
【符号の説明】
１…電源、２…一次側遮断器、３…変圧器、４…一次側変流器、５…二次側変流器、６…比率差動継電器、７…二次側遮断器、８…入力変換手段、９…アナログデジタル変換手段、１０ａ…第１の内部故障検出手段、１０ｂ…第２の内部故障検出手段、１１…負荷量検出手段、１２…演算処理手段、１３…外部出力手段、１４…表示手段、１５…設定手段、１６…データバス[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ratio differential relay for detecting an accident such as a short circuit inside a transformer of a power system.
[0002]
[Prior art]
As a relay for detecting and protecting an internal accident of a transformer of a power system, there is a ratio differential relay. FIG. 3 is a system diagram in the case where the transformer 3 of the power system is protected by the ratio differential relay 6. The primary side of the transformer 3 is connected to a power source 1 such as a generator via a primary side circuit breaker 2, and the secondary side is connected to a load side such as a transmission line or a distribution line via a secondary side circuit breaker 7. Have been. A primary side current transformer 4 is connected to the primary side of the transformer 3, a secondary side current transformer 5 is connected to the secondary side, and a primary side current I 1 and a secondary side current from the primary side current transformer 4 are connected. The secondary current I2 of the side current transformer 5 is input to the ratio differential relay 6.
[0003]
The ratio differential relay 6 receives the primary side current I1 and the secondary side current I2 in opposite polarities, and determines that an internal failure of the transformer has occurred when the difference current deviates from a predetermined range set according to the load current. Like that. When it is determined that the internal failure of the transformer occurs, the primary circuit breaker 2 and the secondary circuit breaker 7 of the transformer 3 are opened, and the transformer 3 is disconnected from the power system. As a result, the faulty section is separated from the sound power system so that the operation of the sound power system can be continued.
[0004]
As described above, the primary current I1 and the secondary current I2 of the transformer 3 input to the ratio differential relay 6 are input in opposite directions, and the internal fault of the transformer 3 is detected by the difference current. ing. Therefore, the polarity of the primary current transformer 4 for detecting the primary current I1 and the polarity of the secondary current transformer 5 for detecting the secondary current I2 are important.
[0005]
[Problems to be solved by the invention]
However, if the direction of the current is the same due to a polarity error of the current transformers 4 and 5 or a wiring error, a normal failure determination calculation cannot be performed, and the ratio differential relay 6 malfunctions. Will be reached. Therefore, the polarities of the secondary circuits of the current transformers 4 and 5 are carefully adjusted so that the primary current I1 and the secondary current I2 of the transformer 3 are input to the ratio differential relay 6 in the reverse direction. And a confirmation test before the start of operation. However, in the confirmation test, it is practically impossible to perform the test by actually passing a current to the transformer 3, so that incorrect polarity or incorrect wiring of the current transformers 4 and 5 may not be completely prevented. A malfunction of the ratio differential relay 6 may occur.
[0006]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a differential circuit capable of preventing a malfunction even if the directions of a primary current and a secondary current of a transformer are input in wrong directions, and enabling a normal operation when an internal failure occurs in the transformer. To provide a ratio relay.
[0007]
[Means for Solving the Problems]
In the ratio differential relay according to the first aspect of the present invention, current transformers are provided on a primary side and a secondary side of a transformer provided in an electric power system, respectively, and a primary side current and a secondary side flowing from these current transformers are provided. In the ratio differential relay that determines an internal failure of the transformer based on the phase difference and the magnitude of the current, a first internal circuit that performs a failure determination operation with the polarities of the primary current and the secondary current being in opposite directions. Failure detection means, second internal failure detection means for performing a failure determination calculation with the polarities of the primary current and the secondary current being in the same direction, and determining the polarities of the primary current and the secondary current. When the polarity is in the opposite direction, the first internal failure detection means is selected, and when the polarity is in the same direction, the second internal failure detection means is selected. First internal failure detection means or second internal failure External output means for outputting a failure determination calculation result of the output means to the outside, and display means for displaying the first internal failure detection means or the second internal failure detection means selected and used by the arithmetic processing means. It is characterized by having.
[0008]
In the ratio differential relay according to the first aspect of the invention, the arithmetic processing means determines the polarity of the primary current and the secondary current, and selects the first internal failure detection means when the polarities are opposite. If the polarities are in the same direction, the second internal failure detection means is selected, and a failure determination operation of the transformer is performed. Then, the failure determination calculation result of the first internal failure detection means or the second internal failure detection means is output to the outside via the external output means. The display means displays the first internal failure detection means or the second internal failure detection means selected and used by the arithmetic processing means.
[0009]
A ratio differential relay according to a second aspect of the present invention, in the first aspect of the present invention, further includes a load amount detecting unit that detects whether a primary current of the transformer is less than a rated load, and the arithmetic processing unit When the load amount detecting means detects that the primary current of the transformer is less than the rated load, the polarity of the primary current and the secondary current is determined, and the first internal If either the failure detection means or the second internal failure detection means is selected, and the load amount detection means detects that the primary current of the transformer is equal to or more than the rated load, the first internal failure detection means It is characterized in that both the failure detection means and the second internal failure detection means are selected.
[0010]
In the ratio differential relay according to the second aspect of the invention, in addition to the operation of the first aspect of the invention, the arithmetic processing means may include a primary load current of the transformer less than the rated load by the load detection means. When it is detected, the polarity of the primary current and the secondary current is determined, and either the first internal failure detection means or the second internal failure detection means is selected based on the polarity. On the other hand, when the load amount detecting means detects that the primary current of the transformer is equal to or higher than the rated load, both the first internal fault detecting means and the second internal fault detecting means are selected. Thus, in the operating state of the rated load or more, the transformer is disconnected from the power system when either the first internal failure detection means or the second internal failure detection means operates.
[0011]
According to a third aspect of the present invention, in the ratio differential relay according to the first or second aspect, there is provided setting means for selectively setting either the first internal fault detecting means or the second internal fault detecting means. The arithmetic processing means preferentially uses the first internal failure detection means or the second internal failure detection means set by the setting means.
[0012]
In the ratio differential relay according to the third aspect of the present invention, in addition to the operation of the first or second aspect of the present invention, the arithmetic processing means includes the first internal failure detection means or the second internal failure detection means set by the setting means. Priority is given to internal failure detection means.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram of a ratio differential relay according to an embodiment of the present invention. The primary-side current I1 detected by the primary-side current transformer 4 and the secondary-side current I2 detected by the secondary-side current transformer 5 are converted into respective analog digital signals via the input conversion means 8 of the ratio differential relay 6. It is input to the conversion means 9a, 9b. The analog quantities taken into the analog-to-digital conversion means 9a and 9b are converted into digital data and guided to the data bus 16. The digital data guided to the data bus 16 is taken into the first internal failure detection means 10a, the second internal failure detection means 10b, the load amount detection means 11, and the arithmetic processing means 12.
[0014]
The first internal failure detection means 10a performs a failure determination operation similar to the failure determination operation of the existing ratio differential relay 6. That is, a failure determination operation is performed with the secondary current I2 in the reverse direction with respect to the primary current I1 of the transformer 3, and an internal failure of the transformer 3 is detected. On the other hand, the second internal failure detecting means 10b performs a failure determination operation with the secondary current I2 in the same direction as the primary current I1 of the transformer 3, and detects an internal failure of the transformer 3. That is, even if the connection of the primary side current transformer 4 or the secondary side current transformer 5 is incorrectly connected and the polarity is reversed, the failure determination calculation can be performed properly.
[0015]
The load amount detecting means 11 detects that the primary current I1 of the transformer 3 is less than the rated load current of the transformer 3. When the operation of the transformer 3 is started, a current smaller than the rated load current is applied as a load current, so that the polarities of the current transformers 4 and 5 can be properly determined at the start of operation.
[0016]
When the load detected by the load detector 11 is smaller than the set value, the processor 12 determines the polarity of the primary current I1 and the secondary current I2 of the transformer 3 and determines the polarity. Based on this, either the first internal failure detection means 10a or the second internal failure detection means 10b is selected. When the secondary current I2 has the opposite polarity to the primary current I1, the second internal failure detection means 10b is locked and the first internal failure detection means 10a is selected. On the other hand, when the secondary current I2 has the same polarity as the primary current I1, the first internal failure detection means 10a is locked and the second internal failure detection means 10b is selected. As a result, the internal fault detecting means having the correct polarity is used, and the internal fault detecting means having the wrong polarity is locked.
[0017]
On the other hand, when the load amount detecting means 11 detects that the primary current of the transformer 3 is equal to or more than the rated load, both the first internal fault detecting means 10a and the second internal fault detecting means 10b are switched off. select. As a result, in an operation state in which the load is equal to or higher than the rated load, the transformer 3 is disconnected from the power system when either the first internal failure detection means 10a or the second internal failure detection means 10b operates, and the protection is not performed. We are trying to strengthen it.
[0018]
The external output means 13 takes in the internal fault detected by the first internal fault detecting means 10a or the second internal fault detecting means 10b via the data bus 16 and outputs an open command to the circuit breakers 2, 7. is there. The display means 14 displays the contents set by the setting means 15 and also indicates which internal failure detection means is used. The setting unit 15 sets the operation conditions of the first internal failure detection unit 10a or the second internal failure detection unit 10b, and also sets the load amount of the load amount detection unit 11.
[0019]
Further, it is possible to set which one of the first internal failure detection means 10a and the second internal failure detection means 10b is used. For example, assuming that the internal failure detection means automatically selected by the arithmetic processing means 12 at the start of operation has the correct polarity, and in subsequent operations, when the internal failure detection means is used with priority, the setting means 15 The internal failure detection means is set.
[0020]
FIG. 2 is a flowchart showing the operation of the ratio differential relay according to the embodiment of the present invention. First, it is determined whether or not the setting means 15 is set as the internal failure detection means used by the first internal failure detection means 10a (S1). When the first internal failure detection means 10a is set as the internal failure detection means to be used, the first internal failure detection means 10a is used (S2), and the display means 14 displays the first internal failure detection means 10a. Is displayed (S3). Then, when an internal failure of the transformer 3 is detected (S4), a protection operation of disconnecting the transformer 3 from the power system by outputting an open command of the circuit breakers 2 and 7 from the external output means 13 is performed (S5).
[0021]
If it is determined in step S1 that the first internal failure detection means 10a is not used, it is determined whether or not the setting means 15 is set as the internal failure detection means used by the second internal failure detection means 10b. A determination is made (S6). When the second internal failure detection means 10b is set as the internal failure detection means to be used, the second internal failure detection means 10b is used (S7), and the display means 14 displays the second internal failure detection means 10b. Is displayed (S8). Then, when an internal failure of the transformer 3 is detected (S9), a protection operation of disconnecting the transformer 3 from the power system by outputting an open command of the circuit breakers 2 and 7 from the external output means 13 is performed (S5).
[0022]
When it is determined in step S6 that the second internal failure detecting means 10b is not used, it is determined whether the primary current I1 is less than the rated load current of the set transformer (S10). If the load current is equal to or higher than the rated load current, the first internal fault detecting means 10a and the second internal fault detecting means 10b are also used (S11), and the display means 14 displays the first internal fault detecting means 10a and the second internal fault. The fact that both of the detection means 10b are used is displayed (S12). When an internal failure of the transformer 3 is detected (S13), a protection operation for disconnecting the transformer 3 from the power system by outputting an open command of the circuit breakers 2 and 7 from the external output means 13 is performed (S5).
[0023]
If it is determined in step S10 that the primary current I1 is less than the rated load current of the set transformer, the polarity of the secondary current I2 is opposite to the primary current I1. It is determined whether or not it is (14). When the polarity of the secondary current I2 is opposite to the primary current I1, the second internal failure detection means 10b is locked (S15), and the first internal failure detection means 10a is used (S16). . Then, the use of the first internal failure detecting means 10a is displayed on the display means 14 (S17), and if an internal failure of the transformer 3 is detected (S18), the circuit breakers 2, 7 are opened from the external output means 13. A protection operation for outputting a command and disconnecting the transformer 3 from the power system is performed (S5).
[0024]
If it is determined in step S14 that the polarity of the secondary current I2 is not opposite to the primary current I1, the first internal failure detection means 10a is locked (S19), and the second internal failure is detected. The detecting means 10b is used (S20). Then, the use of the second internal failure detecting means 10b is displayed on the display means 14 (S21). If an internal failure of the transformer 3 is detected (S22), the circuit breakers 2, 7 are opened from the external output means 13. A protection operation for outputting a command and disconnecting the transformer 3 from the power system is performed (S5).
[0025]
As described above, according to the embodiment of the present invention, it is possible to prevent a malfunction of the ratio differential relay due to a polarity error of the current transformers 4 and 5. When the polarities of the current transformers 4 and 5 can be confirmed, an internal failure detecting means that normally operates with the polarity can be set and used.
[0026]
【The invention's effect】
As described above, according to the present invention, the polarity of an input current can be detected and an appropriate internal failure detection means can be selected according to the polarity. Malfunction of the ratio differential relay immediately after can be prevented, and when an internal failure of the transformer occurs, an accident can be properly detected and a protective operation can be performed.
[Brief description of the drawings]
FIG. 1 is a block diagram of a ratio differential relay according to an embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the ratio differential relay according to the embodiment of the present invention.
FIG. 3 is a system diagram in a case where a transformer of a power system is protected by a ratio differential relay.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Power supply 2 ... Primary circuit breaker 3 ... Transformer 4 ... Primary current transformer 5 ... Secondary current transformer 6 ... Ratio differential relay 7 ... Secondary circuit breaker 8 ... Input conversion means, 9 analog-digital conversion means, 10a first internal failure detection means, 10b second internal failure detection means, 11 load amount detection means, 12 arithmetic processing means, 13 external output means, 14 display means, 15 setting means, 16 data bus
