RATIO DIFFERENTIAL RELAY

To improve the sensitivity of abnormal detection in a ratio differential relay.SOLUTION: A ratio differential relay 1 comprises a data processing control circuit 8. The data processing control circuit 8 calculates a difference current Id that is a difference between a first current (I1 s*Nct1) as a current obtained by converting a first detection current I1s of a first converter 2 into a primary side current I1 of a transformer 50 on the basis of a first current conversion ratio Nct1 of the first converter 2 and a second current (I2s*Nct2*Ntr) as a current obtained by converting a second detection current I2s of a second converter 3 into the primary side current I1 on the basis of a second conversion ratio Nct2 of a second converter 3 and a transformation ratio Ntr, and calculates a suppression current Is that is a sum of an absolute value of the first current and an absolute value of the second current. The data processing control circuit 8 compares a ratio K of the difference current Id and the suppression current Is with a first setting value 131, and determines whether or not the transformer 50 is abnormal on the basis of the comparison result.SELECTED DRAWING: Figure 4 【課題】比率差動継電器において異常検出の感度を向上させる。【解決手段】比率差動継電器１はデータ処理制御回路８を備え、データ処理制御回路８は、第１変流器２の第１変流比Ｎｃｔ１に基づいて第１変流器２の第１検出電流Ｉ１ｓを変圧器５０の一次側電流Ｉ１に換算した電流である第１電流（Ｉ１ｓ×Ｎｃｔ１）と、第２変流器３の第２変流比Ｎｃｔ２および変圧比Ｎｔｒに基づいて第２変流器３の第２検出電流Ｉ２ｓを一次側電流Ｉ１に換算した電流である第２電流（Ｉ２ｓ×Ｎｃｔ２×Ｎｔｒ）との差である差電流Ｉｄを算出するとともに、第１電流の絶対値と第２電流の絶対値との和である抑制電流Ｉｓを算出する。データ処理制御回路８は、差電流Ｉｄと抑制電流Ｉｓとの比率Ｋと第１整定値１３１とを比較し、比較結果に基づいて変圧器５０が異常であるか否かを判定することを特徴とする。【選択図】図４