10.1.3 Setting guidelines IP15000-1 v110.1.3.1 General M13683-3 v5The negative and zero sequence voltages and currents always exist due to different non-symmetries in the primary system and differences in the current and voltage instrumenttransformers. The minimum value for the operation of the current and voltage measuringelements must always be set with a safety margin of 10 to 20%, depending on the systemoperating conditions.Pay special attention to the dissymmetry of the measuring quantities when the function isused on long untransposed lines, on multicircuit lines and so on.The settings of negative sequence, zero sequence and delta algorithm are in percent of thebase voltage and base current for the function. Common base IED values for primary current(IBase), primary voltage (UBase) and primary power (SBase) are set in Global Base ValuesGBASVAL. The settingGlobalBaseSel is used to select a particularGBASVAL and used its basevalues.10.1.3.2 Setting of common parameters M13683-9 v9Set the operation mode selectorOperation toOn to release the fuse failure function.The voltage thresholdUSealIn< is used to identify low voltage condition in the system. SetUSealIn< below the minimum operating voltage that might occur during emergencyconditions. We propose a setting of approximately 70% ofUBase.The drop off time of 200 ms for dead phase detection makes it recommended to always setSealIn toOn since this will secure a fuse failure indication at persistent fuse fail when closingthe local breaker when the line is already energized from the other end. When the remotebreaker closes the voltage will return except in the phase that has a persistent fuse fail. Sincethe local breaker is open there is no current and the dead phase indication will persist in thephase with the blown fuse. When the local breaker closes the current will start to flow and thefunction detects the fuse failure situation. But due to the 200 ms drop off timer the outputBLKZ will not be activated until after 200 ms. This means that distance functions are notblocked and due to the “no voltage but current” situation might issue a trip.The operation mode selectorOpMode has been introduced for better adaptation to systemrequirements. The mode selector enables selecting interactions between the negativesequence and zero sequence algorithm. In normal applications, theOpMode is set to eitherUNsINs for selecting negative sequence algorithm orUZsIZs for zero sequence basedalgorithm. If system studies or field experiences shows that there is a risk that the fuse failurefunction will not be activated due to the system conditions, the dependability of the fusefailure function can be increased if theOpMode is set toUZsIZs OR UNsINs orOptimZsNs. InmodeUZsIZs OR UNsINs both negative and zero sequence based algorithms are activated andworking in an OR-condition. Also in modeOptimZsNs both negative and zero sequencealgorithms are activated and the one that has the highest magnitude of measured negative orzero sequence current will operate. If there is a requirement to increase the security of the fusefailure functionOpMode can be selected toUZsIZs AND UNsINs which gives that both negativeand zero sequence algorithms are activated and working in an AND-condition, that is, bothalgorithms must give condition for block in order to activate the output signals BLKU or BLKZ.10.1.3.3 Negative sequence based M13683-17 v9The relay setting value3U2> is given in percentage of the base voltageUBase and should notbe set lower than the value that is calculated according to equation 86.Section 10 1MRK 504 158-UEN ASecondary system supervision154Application manual
