For ANSI inverse time characteristics, all three types of reset time characteristicsare available: instantaneous (1), IEC (2 = set constant time reset) and ANSI (3 =current dependent reset time).For IEC inverse time characteristics, the possible delay time settings areinstantaneous (1) and IEC (2 = set constant time reset).For the customer tailor-made inverse time delay characteristics (type 17), all threetypes of reset time characteristics are available: instantaneous (1), IEC (2 = setconstant time reset) and ANSI (3 = current dependent reset time). If the current-dependent type is used, settings pr, tr and cr must be given.tResetx: Constant reset time delay in seconds for step x.tPCrvx, tACrvx, tBCrvx, tCCrvx: These parameters are used by the customer tocreate the inverse time characteristic curve. See equation 101 for the timecharacteristic equation. For more information, refer to Technical manual.[ ]>pAt s B IxMulti Cin= + ×-æ öç ÷ç ÷ç ÷æ öç ÷ç ÷è øè øEQUATION1261 V2 EN-US (Equation 101)tPRCrvx, tTRCrvx, tCRCrvx: These parameters are used by the customer to createthe inverse reset time characteristic curve. For more information, refer to Technicalmanual.HarmRestrainx: Enables the block of step x from the harmonic restrain function(2nd harmonic). This function should be used when there is a risk of an unwantedtrip caused by power transformer inrush currents. It can be set to Off/On.8.2.3.2 Setting example GUID-20729467-24AB-42F0-9FD1-D2959028732E v1Directional phase overcurrent protection, four steps can be used in different ways,depending on the application where the protection is used. A general description isgiven below.The operating current setting of the inverse time protection, or the lowest currentstep of the definite time protection, must be defined so that the highest possibleload current does not cause protection operation. The protection reset current mustalso be considered so that a short peak of overcurrent does not cause the operationof a protection even when the overcurrent has ceased. This phenomenon isdescribed in Figure 75.Section 8 1MRK 505 393-UEN BCurrent protection158 Line differential protection RED650 2.2 IECApplication manual
