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A2H124-24FX P0973BJ switches

Response after decay of the memorised voltage The voltage measured by the protection can quickly decay to almost zero for a close fault and make determining direction unreliable. For this reason, the function includes a voltage memory feature and for the first 200 milliseconds after the incidence of an overcurrent, the voltage measured immediately before the fault is used as reference to determine fault direction. After this time, the last valid direction is used for an adjustable period (see next paragraph). “MemDirMode” provides facility for setting how the protection must respond after this time or in the event that the circuitbreaker is closed onto a fault and no voltage could be memorised beforehand. The two possible settings are the protection can trip or it can block. Time during which the memorised direction is valid The “MemDuration” setting determines how long the last valid direction measurement shall be used. The setting should be as short as possible (200 ms) when the function is being used as backup for a distance function in an HV power system, because an actually measured voltage is only available during this time and therefore it is only possible to detect a reversal of direction during this time. For longer settings, the last valid power direction is used instead of the actually memorised voltage

Explanation of parameters: 

RunOnCPU defines the processing unit which runs the function. ParSet 4..1 Parameter for determining in which set of parameters a particular function is active (see Section 5.11.). Trip 01-08 defines the tripping channel activated by the tripping O/P of the function (matrix tripping logic).

Trip 09-16 corresponds to Trip 01-08 (providing tripping unit fitted). Trip 17-24 corresponds to Trip 01-08 (providing tripping unit fitted). Trip 25-32 corresponds to Trip 01-08 (providing tripping unit fitted). CurrentInp defines the c.t. current input channel. Only three-phase c.t’s can be set and the first channel (R phase) of the group of three selected must be specified. VoltageInp defines the v.t. voltage input channel. Only three-phase v.t’s can be set and the first channel (R phase) of the group of three selected must be specified. I-Start Pick-up current at which the characteristic becomes effective. Angle Characteristic angle. c-Setting Setting for the exponential factor determining the operating characteristic according to BS 142. k1-Setting Constant determining the parallel shift of the characteristic. t-min Definite minimum operating time, operating characteristic constant. IB-Setting Base current for taking account of differences of rated current IN. tWait Time allowed for the directional decision to be received. MemDirMode determines the response of the protection after the time set for memorising power direction:
trip
block.