first case influences the operation of all voltage-dependent functions while thesecond one does not affect the impedance measuring functions.The negative sequence detection algorithm, based on the negative-sequencemeasuring quantities is recommended for use in isolated or high-impedance earthednetworks: a high value of voltage 3U2 without the presence of the negative-sequence current 3I2 is a condition that is related to a fuse failure event.The zero sequence detection algorithm, based on the zero sequence measuringquantities is recommended for use in directly or low impedance earthed networks:a high value of voltage 3U0 without the presence of the residual current 3I0 is acondition that is related to a fuse failure event. In cases where the line can have aweak-infeed of zero sequence current this function shall be avoided.A criterion based on delta current and delta voltage measurements can be added tothe fuse failure supervision function in order to detect a three phase fuse failure.This is beneficial for example during three phase transformer switching.11.2.3 Setting guidelines IP15000-1 v111.2.3.1 General M13683-3 v5The negative and zero sequence voltages and currents always exist due to differentnon-symmetries in the primary system and differences in the current and voltageinstrument transformers. The minimum value for the operation of the current andvoltage measuring elements must always be set with a safety margin of 10 to 20%,depending on the system operating conditions.Pay special attention to the dissymmetry of the measuring quantities when thefunction is used on long untransposed lines, on multicircuit lines and so on.The settings of negative sequence, zero sequence and delta algorithm are in percentof the base voltage and base current for the function. Common base IED values forprimary current (IBase), primary voltage (UBase) and primary power (SBase) areset in Global Base Values GBASVAL. The setting GlobalBaseSel is used to select aparticular GBASVAL and used its base values.11.2.3.2 Setting of common parameters M13683-9 v9Set the operation mode selector Operation to On to release the fuse failurefunction.The voltage threshold USealIn< is used to identify low voltage condition in thesystem. Set USealIn< below the minimum operating voltage that might occurduring emergency conditions. We propose a setting of approximately 70% ofUBase.The drop off time of 200 ms for dead phase detection makes it recommended toalways set SealIn to On since this will secure a fuse failure indication at persistent1MRK 505 393-UEN B Section 11Secondary system supervisionLine differential protection RED650 2.2 IEC 211Application manual
