Permissive Underreach Transfer Trip - ABB REL 301 Instruction Leaflet

g. Programmable Reclosing Initiation (Figure 2-18)
The basic programmable reclose initiation application is as described in Section 2.4.14. How-
ever, on pilot systems, to activate the reclose initiate output RI2, for any high-speed trip, the EXT.
PILOT ENABLE SW. (Figure 2-18) must be satisfied, and the setting "FAST RI" should be set
to "Pilot/Z1/Inst I". The operation will occur via the logic AND 89, AND 84 as shown in Figure
2-18.
2.5.1.2 Permissive Underreach Transfer Trip (Figure 2-23)
If a permissive underreaching transfer trip (PUTT) system is desired, the system type setting
"Syst Type", is set to "PUTT". Basic operating concepts of a PUTT scheme are:
1) Pilot distance measurement units PLTP and PLTG ("Pilot Ø" and "Pilot G") are set to
overreach. The pilot channel is a frequency-shift type device, and the transmitter frequency
is different at each terminal.
2) The pilot channel is normally operated with a guard frequency, the channel frequency will
be shifted from guard to trip when the zone-1 distance measurement units Z1P or Z1G op-
erate, and pilot trip is performed when the pilot relay PLTP or PLTG operates, together with
the receiving of a carrier trip signal from the remote end.
PUTT includes the following logic:
a. Pilot Tripping Logic
The Pilot Tripping Logic for the PUTT scheme is the same as for the POTT scheme (Figures
2-20, 2-21).
b. Carrier Keying Logic
1) Forward fault keying (Figure 2-23)
For a forward end zone fault, the PUTT scheme will not key except when the internal fault
is within the zone-1 reach. This means that the PUTT scheme keys only on Zone-1 faults.
Keying is via AND 46, AND 33, OR 18 and AND 35.
2) Signal continuation (Figure 2-23)
Same as for POTT scheme.
The TBM logic is not required because the carrier keying units are set to underreach.
NOTE: For open breaker condition, the echo keying will not work due to lack of the
c. Programmable Reclosing Initiation (Figure 2-18)
Same as for POTT scheme.
d. Carrier Receiving Logic (Figure 2-29)
Same as for POTT scheme except as shown.
e. Channel Indicators (Figure 2-22)
Same as for POTT scheme except recorded as PUTT.
"SEND" signal from the remote terminal for an end zone fault. The remote termi-
nal relies on Zone-2 to clear the fault.
I.L. 40-386.4
2-17