tDLD: The time delay for activating ZCVPSOF by the internal dead-line detectionis, by default, set to 0.2 seconds. It is suitable in most applications. The delay shallnot be set too short to avoid unwanted activations during transients in the system.Mode: The operation of ZCVPSOF has three modes for defining the criteria fortripping. The setting of Mode is, by default, UILevel, which means that the trippingcriterion is based on the setting of IPh< and UPh<. The choice of UILevel gives afaster and more sensitive operation of the function, which is important for reducingthe stress that might occur when energizing onto a fault. However, the voltagerecovery can be slow in some systems when energizing the line. Therefore, if thetimer tDuration is set too short, ZCVPSOF can interpret this as a fault and release atrip.When Mode is set to Impedance, the operate criterion is based on the BC input(breaker closing), which can be the start of the overreaching zone from theimpedance zone measurement or a tOperate-delayed START_DLYD input. Anondirectional output signal should be used from an overreaching zone. Theselection of the Impedance mode gives increased security.When Mode is set to UILvl&Imp, the condition for tripping is an ORed betweenUILevel and Impedance.tDuration: The setting of the timer for the release of UILevel is, by default, 0.02seconds, which has proven to be suitable in most cases from field experience. If ashorter time delay is to be set, it is necessary to consider the voltage recovery timeduring line energization.tOperate: The time delay for the START_DLYD input to activate TRIP whenMode is set to Impedance or UILvl&Imp is, by default, set to 0.03 seconds.1MRK 505 393-UEN B Section 7Impedance protectionLine differential protection RED650 2.2 IEC 145Application manual
