GE B90 UR Series Instruction Manual page 242

5.7 INPUTS/OUTPUTS
The FlexLogic operand response time to the contact input change is equal to the debounce time setting plus up to one pro-
tection pass (variable and depending on system frequency if frequency tracking enabled). If the change of state occurs just
after a protection pass, the recognition is delayed until the subsequent protection pass; that is, by the entire duration of the
protection pass. If the change occurs just prior to a protection pass, the state is recognized immediately. Statistically a delay
of half the protection pass is expected. Owing to the 0.5 ms scan rate, the time resolution for the input contact is below
1msec.
For example, 8 protection passes per cycle on a 60 Hz system correspond to a protection pass every 2.1 ms. With a con-
tact 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 = 5.1
ms. 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 s accuracy using the
time of the first scan corresponding to the new state (mark no. 2 below). Therefore, the time stamp reflects a change in the
DC voltage across the contact input terminals that was not accidental as it was subsequently validated using the debounce
timer. Keep in mind that the associated FlexLogic operand is asserted/de-asserted later, after validating the change.
The debounce algorithm is symmetrical: the same procedure and debounce time are used to filter the LOW-HIGH (marks
no.1, 2, 3, and 4 in the figure below) and HIGH-LOW (marks no. 5, 6, 7, and 8 below) transitions.
2
5
Time stamp of the first
scan corresponding to
the new validated state is
logged in the SOE record
SCAN TIME
(0.5 msec)
PROTECTION PASS
(8 times a cycle controlled by the
frequency tracking mechanism)
Figure 5–63: INPUT CONTACT DEBOUNCING MECHANISM AND TIME-STAMPING SAMPLE TIMING
Contact inputs are isolated in groups of four to allow connection of wet contacts from different voltage sources for each
group. The
CONTACT INPUT THRESHOLDS
value should be selected according to the following criteria: 17 for 24 V sources, 33 for 48 V sources, 84 for 110 to 125 V
sources and 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 it in
the Event Records menu, make the following settings changes:
CONTACT INPUT H5A ID:
CONTACT INPUT H5A EVENTS:
Note that the 52b contact is closed when the breaker is open and open when the breaker is closed.
5-128
USER-PROGRAMMABLE THRESHOLD
1 3
At this time, the The FlexLogic
new (HIGH) operand is going to
contact state is be asserted at this
validated protection pass
DEBOUNCE TIME
(user setting)
4
The FlexLogic TM operand
changes reflecting the
validated contact state
determine the minimum voltage required to detect a closed contact input. This
"Breaker Closed (52b)"
"Enabled"
B90 Low Impedance Bus Differential System
6
Time stamp of the first
TM
scan corresponding to the
new validated state is
logged in the SOE record
DEBOUNCE TIME
(user setting)
5 SETTINGS
5
At this time, the new
(LOW) contact state is
validated
7
The FlexLogic TM
operand is going to be
de-asserted at this
protection pass
TM
The FlexLogic operand
changes reflecting the
validated contact state
8
842709A1.cdr
GE Multilin