In figure 81, it can be noted that the fixed extension (c) 4 sec. of tPulseDur, ismade to prevent a situation with TCINPROG set high without the simultaneouspresence of an URAISE or ULOWER command. If this would happen, TCMYLTCor TCLYLTC would see this as a spontaneous TCINPROG signal without anaccompanying URAISE or ULOWER command, and this would then lead to theoutput signal TCERRAL being set high and TR1ATCC or TR8ATCC functionbeing blocked. Effectively this is then also a supervision of a run-away tapsituation.Hunting detection SEMOD159053-361 v4Hunting detection is provided in order to generate an alarm when the voltagecontrol gives an abnormal number of commands or abnormal sequence ofcommands within a pre-defined period of time.There are three hunting functions:1. The Automatic voltage control for tap changer function, TR1ATCC for singlecontrol and TR8ATCC for parallel control will activate the output signalDAYHUNT when the number of tap changer operations exceed the numbergiven by the setting DayHuntDetect during the last 24 hours (sliding window).Active as well in manual as in automatic mode.2. TR1ATCC or TR8ATCC function will activate the output signal HOURHUNTwhen the number of tap changer operations exceed the number given by thesetting HourHuntDetect during the last hour (sliding window). Active as wellin manual as in automatic mode.3. TR1ATCC or TR8ATCC function will activate the output signal HUNTINGwhen the total number of contradictory tap changer operations (RAISE,LOWER, RAISE, LOWER, and so on) exceeds the pre-set value given by thesetting NoOpWindow within the time sliding window specified via the settingparameter tWindowHunt. Only active in automatic mode.Hunting can be the result of a narrow deadband setting or some other abnormalitiesin the control system.Wearing of the tap changer contacts SEMOD159053-376 v4Two counters, ContactLife and NoOfOperations are available within the Tapchanger control and supervision function, 6 binary inputs TCMYLTC or 32 binaryinputs TCLYLTC. They can be used as a guide for maintenance of the tap changermechanism. The ContactLife counter represents the remaining number ofoperations (decremental counter) at rated load.ContactLife ContactLifen+1 n IratedIloadaæ ö= - ç ÷ç ÷è øEQUATION1873 V2 EN-US (Equation 54)where n is the number of operations and α is an adjustable setting parameter,CLFactor, with default value is set to 2. With this default setting an operation at1MRK 504 169-UEN A Section 11ControlTransformer protection RET650 2.2 IEC 223Application manual
