Digital Teleprotection __________________________________________________________________
RF-MCGARDPRO
Hubbell Power Systems, Inc.
–
RFL™
Products
July 1, 2022
©2022 Hubbell Incorporated
6-3
6.1.2 Direct Transfer Trip
A direct transfer trip system is one in which the teleprotection device is solely responsible for
tripping of the remote breaker. This type of system is generally used for tripping remote circuit
breakers, for transformer faults, shunt reactor protection and breaker failure applications. DTT
schemes typically require trip times around 12ms, however, the trip times are not quite as critical
as with PTT systems, since DTT systems are typically backup protection. Because the
teleprotection unit is solely responsible for tripping, without supervision from the local relay,
security and dependability is of the utmost importance.
BREAKER A
BREAKER B
TRIP BREAKER A
TRIP BREAKER B
TRANSMIT TRIP A
TRANSMIT TRIP B
Z1A
Z1A
RXA
Z1B
Z1B
RXB
Figure 6-3. Direct Transfer Trip
