Basler BE1-11g Instruction Manual page 56

44
Trip and Reset Equations
Equation 3 and Equation 4 represent the trip time and reset time for a constant V/Hz level. Normally, the
V/Hz pickup is set to a value greater than the V/Hz nominal. This ensures that V/Hz measured divided by
V/Hz nominal is always greater than 1.000 throughout the pickup range. If the pickup is set less than
nominal, then measured values above pickup and below nominal will result in the maximum time delay.
The maximum time delay is determined by Equation 3 with (V/Hz measured / V/Hz nominal) set equal to
1.001. The overall inverse time delay range is limited to 1,000 seconds maximum and 0.2 seconds
minimum.
=
T
T

V/Hz

 V/Hz
Equation 3. Time to Trip
where:
T = Time to trip
T
T = Time to reset
R
D = Time dial, trip
T
D = Time dial, reset
R
E = Elapsed time
T
n = Curve exponent (0.5, 1, 2)
FST = Full scale trip time (T
E /FST = Fraction of total travel toward trip that integration had progressed to. (After a trip, this value
T
will be equal to one.)
Pickup and Trip
The Pickup output occurs first, followed by the Trip output.
Pickup
The Pickup output becomes true when the measured V/Hz increases above the V/Hz threshold
established by the Pickup setting. In BESTlogicPlus, the Pickup output can be connected to other logic
elements to annunciate the condition, control other elements in logic, and start the fault recorder (logic
element FAULTTRIG).
Assertion of the Pickup output initiates an inverse or definite timer that begins timing to a trip. The
duration of the timer is established by the Time Dial (inverse time) or Time Delay (definite time) setting. A
Time Delay or Time Dial setting of zero (0) makes the 24 element instantaneous with no intentional time
delay.
If the monitored V/Hz is above both the calculated inverse time and definite time delay thresholds, the
definite time delay has priority over the inverse time characteristic.
If the pickup condition subsides before the element delay or calculated inverse time expires, the timer and
Pickup output are reset, no corrective action is taken, and the element is rearmed for any other
occurrences of overexcitation. If inverse reset is chosen, the inverse trip timer will ramp down towards
reset at a linear rate based on the Reset Dial setting. A Reset Dial setting of zero (0) makes the reset
instantaneous with no intentional delay. See the Time Curve Characteristics chapter for details on each of
the available time curves.
Trip
The Trip output becomes true if an overexcitation pickup condition exists for the duration of the element
Time Delay (definite time) or calculated inverse time. In BESTlogicPlus, the Trip output can be connected
to other logic elements and to a physical relay output to annunciate the condition and to initiate corrective
action. If a target is enabled for the element, the BE1-11g will record a target when the Trip output
becomes true. See the Fault Reporting chapter for more information about target reporting.
Overexcitation (24) Protection
D
T
n

Measured −

1

Nominal
)
T
9424200994 Rev U
E
=
T
T D * * 100
R R
FST
Equation 4. Time to Reset
BE1-11g