The setting of the current limit3I0PU is done in percentage ofIBase. The setting of pickup mustbe higher than the normal unbalance current that might exist in the system. The setting can becalculated according to equation 115.3 03 0 100= ×II PU IBaseEQUATION2293-ANSI V2 EN-US (Equation 115)where:3I0PU is the maximal zero sequence current during normal operating conditions, plus a margin of 10...20%IBase is the base current for the function according to the settingGlobalBaseSel12.2.3.5 Delta V and delta I GUID-02336F26-98C0-419D-8759-45F5F12580DE v7Set the operation mode selectorOpDVDI toEnabled if the delta function shall be in operation.The setting ofDVPU should be set high (approximately 60% ofVBase) and the current thresholdDIPU low (approximately 10% ofIBase) to avoid unwanted operation due to normal switchingconditions in the network. The delta current and delta voltage function shall always be usedtogether with either the negative or zero sequence algorithm. IfVSetprim is the primary voltage foroperation of dU/dt andISetprim the primary current for operation of dI/dt, the setting ofDVPUandDIPU will be given according to equation 116 and equation 117.DVPU VSetVBaseprim= ⋅100EQUATION1765-ANSI V2 EN-US (Equation 116)DIPU ISetIBaseprim= ⋅100ANSIEQUATION2385 V2 EN-US (Equation 117)The voltage thresholdsVPPU is used to identify low voltage condition in the system. SetVPPUbelow the minimum operating voltage that might occur during emergency conditions. A setting ofapproximately 70% ofVBase is recommended.The current threshold50P shall be set lower than theIMinOp for the distance protection function.A 5...10% lower value is recommended.12.2.3.6 Dead line detection M13683-78 v4The condition for operation of the dead line detection is set by the parametersIDLDPU for thecurrent threshold andUDLD< for the voltage threshold.Set theIDLDPU with a sufficient margin below the minimum expected load current. A safetymargin of at least 15-20% is recommended. The operate value must however exceed the maximumcharging current of an overhead line, when only one phase is disconnected (mutual coupling to theother phases).1MRK 511 358-UUS A Section 12Secondary system supervision249Application manual
