Schweitzer Engineering Laboratories SEL-351 - Timer Settings; GARD1 D - Guard-Present Delay; UBDURD - DCUB Disable Delay; UBEND - DCUB Duration Delay

Date Code 20001006 Trip and Target Logic 5-21
SEL-351 Instruction Manual
In three-terminal line DCUB applications (setting ECOMM = DCUB2), loss-of-guard signals are
received from two remote terminals. Two optoisolated inputs on the SEL-351 Relay (e.g., input
IN5 and IN7) are driven by communications equipment receiver outputs (see Figure 5.13). Make
SELOGIC Control Equation settings LOG1 and LOG2 as follows:
LOG1 = IN5 (three-terminal line application)
LOG2 = IN7
SELOGIC Control Equation settings LOG1 and LOG2 are routed into the DCUB logic in
Figure 5.10 for “unblocking block” and “permissive trip receive” logic decisions.
Timer Settings
See Section 9: Setting the Relay for setting ranges.
GARD1D – Guard-Present Delay
Sets minimum time requirement for reinstating permissive tripping following a loss-of-channel
condition – typically set at 10 cycles. Channel 1 and 2 logic use separate timers but have this same
delay setting.
UBDURD – DCUB Disable Delay
Prevents tripping by POTT logic after a settable time following a loss-of-channel condition –
typically set at 9 cycles (150 ms). Channel 1 and 2 logic use separate timers but have this same
delay setting.
UBEND – DCUB Duration Delay
Sets minimum time required to declare a loss-of-channel condition – typically set at 0.5 cycles.
Channel 1 and 2 logic use separate timers but have this same delay setting.
Logic Outputs
The following logic outputs can be tested by assigning them to output contacts. See Output
Contacts in Section 7: Inputs, Outputs, Timers, and Other Control Logic for more information
on output contacts.
UBB1, UBB2 – Unblocking Block Output(s)
In two-terminal line DCUB applications (setting ECOMM = DCUB1), UBB1 disables tripping if
the loss-of-channel condition continues for longer than time UBDURD.
In three-terminal line DCUB applications (setting ECOMM = DCUB2), UBB1 or UBB2 disable
tripping if the loss-of-channel condition (for the respective Channel 1 or 2) continues for longer
than time UBDURD.
The UBB1 and UBB2 are routed in various combinations in Figure 5.11 to control Relay Word bit
UBB, depending on enable setting ECOMM = DCUB1 or DCUB2. Relay Word bit UBB is the
Courtesy of NationalSwitchgear.com