2-26
Specifications
Date Code 20010515
SEL-2BFR, -2/BFR Instruction Manual
timer starts and the 86BF Trip output deasserts. The 62M4 timer has a fixed value of 300 cycles.
When the 62M4 timer expires, the 86RS bit asserts for 60 cycles if no protected trip or close
resistor has failed.
If the 50MD overcurrent elements have not dropped out when 62M1 times out, the relay
postpones 86BF TRIP deassertion and asserts the ALRM bit. As soon as the 50MD overcurrent
elements drop out, the 86BF Trip output deasserts and the 62M4 timer starts, as described above.
In two situations, the relay delays assertion of the 86BF Reset bit 86RS. These situations are (1)
a Close resistor thermal failure element is asserted and CTF is set in the M86T logic mask, or
(2) a trip resistor failure element is asserted and TTF is set in the M86T logic mask. When the
thermal failure condition drops out, the 86BF Reset bit asserts for 60 cycles.
Figure 2.15: MOD Trip Disabled Logic Timing Diagram
MOD Trip Enabled
Figure 2.16 shows the logic used to assert the 86BF trip output and the 86RS reset bit in the
Relay Word when MOD Trip logic is enabled. Figure 2.17 shows the timing of the MOD Trip
Enabled logic.
The 86BF Trip output asserts and the 62M1 timer starts when the Relay Word logically ANDed
with the M86T mask is not zero. If the 50MD elements have dropped out when the 62M1 timer
expires, the MDT (MOD Trip) bit asserts and the 62M2 timer starts. When the 62M2 timer
expires, if no 50LD overcurrent element is picked up, the MOD status input is deasserted, and the
86BF Trip condition has cleared, the 86BF Trip output deasserts and the 62M4 timer starts. Five
seconds (62M4 time) after the 86BF Trip output deasserts, the 86RS bit asserts, and one second
later both MDT and 86RS deassert.
If the 50MD overcurrent elements have not dropped out when 62M1 expires, MDT assertion is
delayed until all three 50MD elements drop out.
If any 50LD overcurrent element is picked up when the 62M2 timer expires, the Relay Word
ALRM bit asserts for one second and the message: “Current after ModTrip” is stored in the
ALRM buffer. When the 50LD elements drop out, the timing sequence continues as described
above.
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