5-304 G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUALINPUTS/OUTPUTS CHAPTER 5: SETTINGS5For example, eight protection passes per cycle on a 60 Hz system correspond to a protection pass every 2.1 ms. With acontact debounce time setting of 3.0 ms, the FlexLogic operand-assert time limits are: 3.0 + 0.0 = 3.0 ms and 3.0 + 2.1 = 5.1ms. These time limits depend on how soon the protection pass runs after the debouncing time.Regardless of the contact debounce time setting, the contact input event is time-stamped with a 1 μs accuracy using thetime of the first scan corresponding to the new state (mark no. 2 shown). Therefore, the time stamp reflects a change in theDC voltage across the contact input terminals that was not accidental as it was subsequently validated using thedebounce timer. Keep in mind that the associated FlexLogic operand is asserted/de-asserted later, after validating thechange.The debounce algorithm is symmetrical: the same procedure and debounce time are used to filter the LOW-HIGH (marksno.1, 2, 3, and 4 in the figure) and HIGH-LOW (marks no. 5, 6, 7, and 8) transitions.Figure 5-170: Input contact debouncing mechanism and time stamp sample timingContact inputs are isolated in groups of four to allow connection of wet contacts from different voltage sources for eachgroup. The CONTACT INPUT THRESHOLDS determine the minimum voltage required to detect a closed contact input. Thisvalue is selected according to the following criteria: 17 for 24 V sources, 33 for 48 V sources, 84 for 110 to 125 V sourcesand 166 for 250 V sources.For example, to use contact input H5a as a status input from the breaker 52b contact to seal-in the trip relay and record itin the Event Records menu, make the following settings changes:CONTACT INPUT H5a ID: "Breaker Closed (52b)"CONTACT INPUT H5a EVENTS: "Enabled"Note that the 52b contact is closed when the breaker is open and open when the breaker is closed.5.9.2 Virtual inputsSETTINGS INPUTS/OUTPUTS VIRTUAL INPUTS VIRTUAL INPUT 1(64) VIRTUAL INPUT 1 VIRTUAL INPUT 1FUNCTION: DisabledRange: Disabled, Enabled
