Multiply the required resistance for the same safety factor KL with the ratiobetween actual voltage and 400kV when the rated voltage of the line underconsideration is higher than 400kV. The outer boundary RLdOutFw obtains in thisparticular case its value according to equation 82.min 0.9 137.2 123.5L LRLdOutFw K R= × = × = WEQUATION1343 V1 EN-US (Equation 82)It is a general recommendation to set the inner boundary RLdInFw of theoscillation detection characteristic to 80% or less of its outer boundary. Takespecial care during the settings of timers tP1 and tP2 which is included in theoscillation detection logic. This requires the maximum permitted setting values offactor kLdRFw = 0.8. Equation 83 presents the corresponding maximum possiblevalue of RLdInFw.98.8= × = WRLdInFw kLdRFw RLdOutFwEQUATION1344 V3 EN-US (Equation 83)The load angles, which correspond to external δOut and internal δIn boundary ofproposed oscillation detection characteristic in forward direction, are calculatedwith sufficient accuracy according to equation 84 and 85 respectively.155.752 arc tan 2 arc tan 64.52 2 123.5d æ ö æ öç ÷= × = × = °ç ÷ç ÷× ×è øè øSOutZRLdOutFwEQUATION1345 V1 EN-US (Equation 84)max155.752 arc tan 2 arc tan 76.52 2 98.8d æ ö æ öç ÷= × = × = °ç ÷ç ÷× ×è øè øSInZRLdInFwEQUATION1346 V1 EN-US (Equation 85)The required setting tP1 of the initial oscillation detection timer depends on theload angle difference according to equation 86.76.5 64.51 13.3360 2.5 360In OutsitP msfd d- ° - °= = =× ° × °EQUATION1347 V1 EN-US (Equation 86)The general tendency should be to set the tP1 time to at least 30 ms, if possible.Since it is not possible to further increase the external load angle δOut, it isnecessary to reduce the inner boundary of the oscillation detection characteristic.The minimum required value is calculated according to the procedure listed inequation 87, 88, 89 and 90.Section 7 1MRK 505 393-UEN BImpedance protection140 Line differential protection RED650 2.2 IECApplication manual
