GE D90 Plus Instruction Manual page 348

PROTECTION INPUTS AND OUTPUTS
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Contact input settings
340
The active impedance feature controls the input impedance presented to the system
according to the current state of the input. When the contact input circuitry initially detects
a voltage increase, it will draw 10 mA of current. If the state change is due to a transient
coupled through the stray capacitance of the field wiring, then the high current sink will
charge the capacitance causing the transient to rapidly decay. If voltage increase is due to
a state change of the field contact, then the increased current will have no impact on the
input voltage, and the state change will be validated. Once the input has been declared to
be on, the input circuitry will reduce the current drawn to 1 mA to minimize the power
dissipated by the input.
The contact input update time is 1 ms. However, depending on where the contact input
status change is triggered within a one millisecond window, the worst-case contact input
recognition time will be 2 ms.
Plus
If a D90 unit with firmware revision 1.60 is changed to firmware 1.50 or lower, then the
contact input and output calibration values will be lost.
When the input detects a voltage decrease, the input circuitry will draw 10 mA of current. If
the voltage decrease is due to a state change then the voltage will quickly decrease,
speeding up the recognition of the reset of the field contact.
Select the Settings > Protection > Protection Inputs/Outputs > Contact Inputs > Contact
Inputs menu item to access the contact input configuration settings.
Figure 277: Contact input configuration settings
The contact inputs menu contains configuration settings for each contact input. Upon
startup, the relay processor determines (from an assessment of the installed modules)
which contact inputs are available and then displays settings for only those inputs. The
following settings are available for each contact input.
ID
Range: up to 12 alphanumeric characters
Default: Cont Ip 1
An alphanumeric ID may be assigned to a contact input for diagnostic, setting, and
event recording purposes. The "CONTACT IP 1" text in event records and FlexLogic™
operands will be replaced by the text programmed in this setting.
Debounce Time
Range: 1.5 to 16.0 ms in steps of 0.25
Default: 2.0 ms
This setting defines the time required for the contact to overcome contact bouncing
conditions. As this time differs for different contact types and manufacturers, program it
as a maximum contact debounce time (per manufacturer specifications) plus additional
margin to ensure proper operation.
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION