7.4.3.5 Settings for each step (x = 1, 2, 3 and 4) M15282-9 v12Operation: Sets the protection to On or Off.DirModex: The directional mode of step x. Possible settings are Off/Non-directional/Forward/Reverse.Characteristx: Selection of time characteristic for step x. Definite time delay anddifferent types of inverse time characteristics are available.Inverse time characteristic enables fast fault clearance of high current faults at thesame time as selectivity to other inverse time phase overcurrent protections can beassured. This is mainly used in radial fed networks but can also be used in meshednetworks. In meshed networks, the settings must be based on network faultcalculations.To assure selectivity between different protections, in the radial network, there hasto be a minimum time difference Dt between the time delays of two protections. Todetermine the shortest possible time difference, the operation time of protections,breaker opening time and protection resetting time must be known. These timedelays can vary significantly between different protective equipment. Thefollowing time delays can be estimated:Protection operate time: 15-60 msProtection resetting time: 15-60 msBreaker opening time: 20-120 msThe different characteristics are described in the technical reference manual.tx: Definite time delay for step x. The definite time tx is added to the inverse timewhen inverse time characteristic is selected. Note that the value set is the timebetween activation of the start and the trip outputs.INx>: Operate residual current level for step x given in % of IB.INx>Max and INx>Min should only be changed if remote setting of operationcurrent level, INx>, is used. The limits are used for decreasing the used range ofthe INx> setting. If INx> is set outside INx>Max and INx>Min, the closest of thelimits to INx> is used by the function. If INx>Max is smaller than INx>Min, thelimits are swapped.kx: Time multiplier for the dependent (inverse) characteristic for step x.: Minimum operate current for step in % of IB. Set below INx> for every step toachieve ANSI reset characteristic according to standard. If is set above INx> forany step, signal will reset at current equals to zero.1MRK 504 169-UEN A Section 7Current protectionTransformer protection RET650 2.2 IEC 127Application manual
