Date Code 20001006 Trip and Target Logic 5-25
SEL-351 Instruction Manual
BT – Received Block Trip Signal(s)
In two-terminal line DCB applications, a block trip signal is received from one remote terminal.
One optoisolated input on the SEL-351 Relay (e.g., input IN4) is driven by a communications
equipment receiver output (see Figure 5.15). Make SELOGIC Control Equation setting BT:
BT = IN4 (two-terminal line application)
In three-terminal line DCB applications, block trip signals are received from two remote terminals.
Two optoisolated inputs on the SEL-351 Relay (e.g., input IN4 and IN6) are driven by
communications equipment receiver outputs (see Figure 5.16). Make SELOGIC Control Equation
setting BT as follows:
BT = IN4 + IN6 (three-terminal line application)
SELOGIC Control Equation setting BT is routed through a dropout timer (BTXD) in the DCB logic
in Figure 5.14. The timer output, Relay Word bit BTX, is routed to the trip logic in Figure 5.1.
Timer Settings
See Section 9: Setting the Relay for setting ranges.
Z3XPU – Zone (Level) 3 Reverse Pickup Time Delay
Current-reversal guard pickup timer – typically set at 1 cycle.
Z3XD – Zone (Level) 3 Reverse Dropout Extension
Current-reversal guard dropout timer – typically set at 5 cycles.
BTXD – Block Trip Receive Extension
Sets reset time of block trip received condition (BTX) after the reset of block trip input BT.
67P2SD, 67N2SD, 67G2SD, 67Q2SD – Level 2 Short Delay
Carrier coordination delays for the output of Level 2 overreaching overcurrent elements 67P2S,
67N2S, 67G2S, and 67Q2S, respectively – typically set at 1 cycle.
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.
Courtesy of NationalSwitchgear.com
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